Richard Gray

CD Bioparticles announces the launch of a new range of Low PDI Polymers. CD Bioparticles, a leading manufacturer and supplier of numerous drug delivery products and services, is thrilled to announce the launch of its latest innovation in the field of polymers, a new range of Low PDI Polymers. These cutting-edge polymers are specifically designed to deliver enhanced performance in various applications, such as drug delivery. Polymers with low polydispersity index (PDI) have a narrow molecular weight distribution, which allows for better control of their properties and ensures consistent performance from batch to batch. This unique characteristic makes these polymers popular for a variety of applications. For instance, resins or polymer systems used for creating durable thin coatings benefit from a lower PDI. This is because they provide high-performance coatings that are thin and have excellent adhesion, abrasion, scratch, and chemical resistance. CD Bioparticles now offers a wide range of Low PDI Polymers, including Polyacrylamide, polystyrene, Polysiloxane, Fused Heterocycle Polymers, Hydrophilic Polymers, and Hydrophobic Homopolymers. These polymers have a narrow molecular weight distribution, making them ideal for various applications such as drug delivery. For example, the Poly vinyl alcohol (Catalog: CDP23-251-L) is produced through the hydrolysis of poly vinyl acetate under alkaline conditions. Poly vinyl acetate is synthesized through a free radical polymerization reaction using ethyl acetate iodine as a chain transfer reagent. The polymerization reaction is conducted in bulk. The company also provides biodegradable polymers, monomers, fluorescent polymers, and PEG conjugations to tackle various drug delivery challenges. Its advanced technology platforms provide solutions for complex chemical synthesis, formulation, purification, and the need for functional groups for further modification, conjugation, or cross-linking. Additionally, CD Bioparticles offers solutions to achieve cell-specific or tissue-specific targeting of nanomedicines. These solutions overcome the difficulties of tracking and imaging the distribution of polymeric (nano) materials, improve drug loading efficiency and yields, address immunoreactivity or xenobiotic reactions, prevent rapid clearance of drug carriers, and control delivery profiles. CD Bioparticles is dedicated to providing its customers with the highest quality products and services. The company’s team of professionals is readily available to address inquiries and offer advice on product selection and usage. In addition to its diverse product range, CD Bioparticles offers exceptional customer support, providing expert guidance and technical assistance to researchers worldwide. CD Bioparticles provides comprehensive solutions for drug delivery scientists, specializing in customized delivery strategies, precise drug design, and modifications of drug-contained cargos. To learn more about CD Bioparticles’ Low PDI Polymers and to explore their applications, please visit https://www.cd-bioparticles.net/low-pdi-polymers. About CD Bioparticles CD Bioparticles is an established drug delivery company that provides customized solutions for developing and manufacturing novel biocompatible drug delivery systems. It specializes in various formulation and drug delivery technologies, from conventional liposomes and PEGylated liposomes to polymer microspheres and nanoparticles for drug delivery. The company also provides contract research services for drug delivery formulation, formulation feasibility study, process development and scale-up, as well as analytical and non-clinical research services.

CD Bioparticles has announced the expanded portfolio of its new Particles for Solid Phase Organic Synthesis. With years of experience in the pharmaceutical and life science sectors, CD Bioparticles has announced the expanded portfolio of its new Particles for Solid Phase Organic Synthesis, including functional resins, preloaded resins and resins for special synthesis, providing a more efficient and time-saving method for the synthesis of small molecules, peptides and oligonucleotides. Solid Phase Organic Synthesis (SPOS) is a method in which molecules are covalently attached to a solid support and chemically synthesized stepwise using selective protecting groups. This method offers many significant advantages over conventional solution phase synthesis methods, including purification of the product by simple filtration of the polymer matrix, automation, ease of handling, low moisture susceptibility, minimal side reactions, no need for polymerization due to targeted separation of polymer particles, and recyclability of the polymer matrix for reuse. As a result, the time required for separation is very short and predictable. The traditional support materials are polystyrene (PS)-based resins and polyethylene glycol (PEG)-grafted PS resins. The presence of PEG makes the resins compatible with polar solvents, especially water. SPOS is widely used in organic synthesis, particularly in the field of drug discovery, where efficient synthesis is highly desirable for high-throughput screening and optimization. In addition, with the advent of solid-phase technology, solid-phase peptide synthesis (SPPS) has become a more practical part of scientific research today. CD Bioparticles now offers a range of functional resins and preloaded resins to meet the needs of small molecule, peptide, and oligonucleotide synthesis. Available in a variety of diameters (from 40 µm to 560 µm) and linker types, these SPOS particles offer excellent chemical and mechanical stability, efficient isolation of intermediates, and improved reaction conversions, making them well suited for high-efficiency synthesis. The particles can be used in a wide range of applications, including general peptide synthesis, long peptide synthesis, small molecule synthesis involving acylation and alkylation, Michael addition, reductive amination, oligonucleotide synthesis, and multi-antigen peptide synthesis for polymerization of immunoconjugates. For example, the DiagSupport™ H-Ala-2-Chlorotrityl Polystyrene/DVB Resin (Cat. No. SPS-AP23-001) have a copolymer matrix of copolymerized (styrene-1% DVB) and a particle size of 100-200 mesh. Since the attached amino acids are N-deprotected, these resins can be used without pretreatment. The resins are very acid sensitive and suitable for the synthesis of protected peptide fragments by Fmoc strategies. The finished peptides can be cleaved under very mild conditions to obtain protected peptides for further processing or under standard acidic conditions to obtain fully deprotected peptides. These new offerings hold great promise for researchers and scientists in the field of organic synthesis. For more information about CD Bioparticles’ new particles for SPOS, please visit https://www.cd-bioparticles.com/products/particles-for-solid-phase-organic-synthesis-1074.html. About CD Bioparticles CD Bioparticles is a leading manufacturer and supplier of various nanoparticles, microparticles, and coatings for R&D as well as commercialization across different application areas, including in vitro diagnostics, biochemistry, cellular analysis, cell separation, and immunoassay. The company also offers various custom services, including chemical surface-functionalization, fluorescent modification, antibody immobilization, as well as nucleic acid and oligo conjugation to meet client specifications.

Poly(lactic-co-glycolic acid) (PLGA) is a functional polymer organic compound randomly polymerized by lactic acid (PLA) and glycolic acid (PGA). It has been approved by the U.S. Food and Drug Administration It is certified by the Food and Drug Administration (FDA) and is a copolymer material available on the market. PLGA has good biocompatibility, biodegradability, mechanical strength, good plasticity, surface modification, and drug encapsulation. It has a wide range of uses in the field of biomedical engineering and has been used in drug sustained-release carriers, artificial catheters and tissue engineering scaffold materials. Figure 1. Schematic representation of PLGA NPs and their multiple potential functionalizations: for diagnostic, targeting, shielding, or stability purposes. As a drug carrier, PLGA is soluble in common solvents such as acetone and ethyl acetate. The size, shape and surface area of PLGA nanoparticles can be adjusted by adjusting the molecular weight and ratio of lactic acid and glycolic acid in the polymer to obtain the required nanocarriers are simultaneously processed and prepared into various shapes and sizes. Currently, PLGA nanoparticles can be prepared based on emulsion solution volatilization or co-precipitation technology. The most common methods include simple mechanical stirring, ultrasonic treatment, high shear mixing (HSM), high pressure homogenization (HPH) and microfluidics. Depending on the preparation methods of PLGA nanoparticles, amphiphilic, hydrophobic or hydrophilic drug molecules can be loaded into the core area of the nanoparticles or adsorbed on the surface of the nanoparticles, which can effectively deliver drugs. Compared with other carrier materials, PLGA nanocarriers have the following advantages: It is polymerized by glycolic acid and lactic acid, and the synthesis process is relatively mature; The nanoparticle size is controllable, uniform in size and small in dispersion; It can achieve long-term sustained release of carrier drugs (several weeks or months), reduce the frequency of medication, and greatly improve patient compliance; Modified PLGA nanoparticles can contain biologically active molecules such as proteins, genetic DNA, and vaccines; After the PLGA surface is chemically modified with ligands, precise targeted delivery of drugs can be achieved. Functional modulation or modification of PLGA nanoparticles is of great significance for the treatment and application of diseases, such as active targeted therapy of drugs or diagnosis of diseases. In drug delivery, in order to accurately reach the lesion site with the appropriate amount of drugs and achieve targeted therapy, proteins, polysaccharides, peptides, or small molecules can usually be formulated on the PLGA carrier through certain chemical coupling or physical cross-linking methods. The body is modified on the surface of PLGA nanoparticles to achieve active targeted delivery to the lesion, improve the therapeutic effect and biological safety of the drug, and reduce the toxic and side effects of the drug on other normal tissue cells. For example, Tween 80, also known as polysorbate 80, can be used as a surfactant in the preparation of PLGA nanoparticles, and it can also adsorb apolipoprotein E to the surface of PLGA nanoparticles. Promote the binding of nanoparticles to lipoprotein receptor-related protein (LRP), thereby effectively promoting the nanoparticles to cross the blood-brain barrier (BBB), which has potential application value in the treatment of brain diseases. The particle size of PLGA nanoparticles is controllable, uniform in size, and has low dispersion. Therefore, it can be well modified on its surface, such as coating with cell membrane, for the design and development of tumor vaccines. CpG is a type of oligodeoxynucleotide that can be used as an immune adjuvant to stimulate the maturation and development of antigen-presenting cells. CpG can be encapsulated with PLGA using the emulsion evaporation method. The tumor cell membrane expresses a large number of tumor-related antigens, so the cell membrane can be used as an antigen to stimulate the body’s immune response. The tumor cell membrane is coated with PLGA nanoparticles, and a nanovaccine based on PLGA as the core is constructed, which can be used to fight melanoma B16 of immunotherapy.

What is POCT? Multiplexed point-of-care testing POCT (Point-of-Care Testing) refers to clinical and bedside testing conducted in close proximity to patients. It is often not performed by clinical laboratory personnel. POCT holds significant importance in disease prevention, etiology determination, prognosis, enhancing treatment outcomes, and reducing healthcare expenses. It meets clinical testing needs across various healthcare settings. POCT serves as a complement to traditional laboratory testing methods. It is characterized by short testing times, spatial flexibility, and simple operation. However, as it is decentralized, the accuracy of test results in POCT can be greatly affected by non-standardized procedures and inadequate quality control. The field of POCT products has advanced through four generations: qualitative, semi-quantitative, fully quantitative, and automated, due to the continuous innovation in testing technologies. POCT technical principles include dry chemistry, colloidal gold, immunofluorescence, microfluidic chips, chemiluminescence, biosensors, and biochips. Colloidal gold is the most commonly used nanoparticle for optical labeling due to its ease of use, biocompatibility, and high visibility. It appears deep red in color, which can cause confusion in on-site testing as it displays the same color in two or more test lines. Polystyrene particles (PS particles), also referred to as latex beads (LBs), impregnated with various bright dyes have several advantages. They are easy to synthesize and have multi-color capability, making them an ideal choice for developing robust immunochromatographic analysis. CD Bioparticles offers a variety of uniform and monodisperse colored polystyrene particles, including Diagpoly™ Colored Polystyrene Particles. These particles are highly pigmented, which can improve visual detection in assays such as latex agglutination, dipstick, and membrane-based assays. Advantages of Colored Polystyrene Particles for POCT Simplicity and speed: In contrast to colloidal gold and fluorescent nanoparticles, colored polystyrene nanoparticles can be prepared by copolymerization with dyes, solvent swelling of templated nanoparticles and self-assembly of block copolymers and dyes, providing various surface functional groups. In addition, polystyrene nanoparticles exhibit excellent biocompatibility and flexibility, facilitating effective conjugation with specific proteins and antibodies. Increased sensitivity and specificity: Each particle of colored polystyrene nanoparticles is carefully designed in size and coated with specific ‘capture molecules’ designed to trap their intended targets. When samples containing target molecules are introduced, these coated particles act like magnets, attracting their specific targets with high affinity. This targeted binding significantly reduces the chance of capturing the wrong molecules, thus minimizing false positives. The large surface area of the polystyrene particles allows more capture molecules to be accommodated, increasing test sensitivity and minimizing false negatives. Polystyrene itself plays a critical role in detection accuracy. This robust material is chemically inert, meaning it does not interfere with the binding process or produce false signals. In addition, its uniform surface provides a stable platform for capture molecule attachment, ensuring consistent and reliable results. Versatility and multiplex detection: While LFTs are typically designed for the rapid detection of single analytes per assay, there is growing interest in multiplex analysis due to its potential for increased throughput, reduced sample requirements and improved assay efficiency. The most common approach to achieving multiplex detection in LFTs is to use multiple test lines on the test strip, each reporting the detection results of specific analytes. Although colloidal gold has a distinct red color, it is limited to single color testing and is not suitable for multiplexing. In contrast, colored latex beads offer a variety of vivid colors for easier visual assessment of multiple test lines, reducing the risk of misinterpretation of results. Cost-effectiveness: Test strips produced with colored latex beads from different batches have relatively little variation between batches, and production processes typically require minimal or no adjustment. Colloidal gold readily adsorbs to certain materials, even when glass containers are used, which introduces unavoidable risks in large-scale production. Therefore, a more cautious approach is to opt for colored latex particles. The use of colored latex particles in the production of immunochromatographic test strips is therefore more cost effective. Customization and flexibility: Through unique surface modification processes, CD Bioparticles can add different functional groups to the surface of colored latex particles, such as carboxyl and amine groups, to facilitate antibody/antigen coupling on microsphere surfaces. Carboxyl-modified colored latex particles introduce more N and O atoms onto the microsphere surface, increasing the rate of antibody migration to the material surface and effectively improving the coupling efficiency. Our microspheres feature uniform particle sizes, stable and controllable surface functional groups and excellent experimental reproducibility. CD Bioparticles can customize colored latex particles with various functional group surface modifications according to customer requirements. Features of CD Bioparticles’ Colored PS Particles Our monodisperse-colored polystyrene latex microspheres have perfect sphericity and narrow size distribution. With a wide size range from 30 nm to 750 µm, they have larger diameters compared to colloidal gold particles typically used in immunochromatography products (colored latex microspheres from 200 nm to 400 nm, colloidal gold particle sizes from 20-40 nm), offering higher relative sensitivity. Shop for DiagPoly™ Colored Polystyrene Particles, 200 nm to 400 nm. We offer a variety of vividly colored latex particles including black, blue, green, orange, red, purple and yellow. With enhanced coloring capabilities, results are more visually intuitive, allowing for easy visual interpretation or multiplexed analysis. Black Latex Particles Red Latex Particles Blue Latex Particles Violet Latex Particles Green Latex Particles Yellow Latex Particles Orange Latex Particles   These colored microspheres are manufactured using an internal embedding method, where the dye is located inside the microsphere, ensuring minimal leakage and stable structural integrity. Our products exhibit exceptional stability in physicochemical properties, which facilitates easy storage. With a high specific surface area and negative surface charge, our colored latex particles can be covalently linked to antibodies via chemical reactions or adsorbed for antibody conjugation. For molecules containing multiple sulphur atoms, latex microspheres offer superior labelling effects. The polystyrene matrix exhibits excellent stability and affinity, as well as good biocompatibility. CD Bioparticles has achieved scale production, offering product specifications from 10 mL to 1000 mL with consistent performance, uniform particle size and minimal variation between batches. Applications of Colored PS Particles Temperature sensing is a promising approach to improve the detection sensitivity of lateral flow immunoassays (LFIA) for POCT. By optically stimulating colored latex beads (CLB) on LFIA strips with laser power below 100 mW, temperature elevations above 100 °C can be easily achieved. The researchers observed a dependence of membrane-bound CLB density on temperature elevation and found that the light absorption of red (and black) latex beads at 520 nm increased 1.3-fold (and 3.2-fold, respectively). This increase is attributed to multiple light scattering in this highly porous medium, a mechanism that could significantly impact the sensitivity improvement of LFIA. The detection limit is 1 × 10^5 particles/mm². The researchers proposed a novel lateral flow detection scheme based on two-color latex labels (blue latex beads, 400 nm, and red latex beads, 400 nm) for multiplex detection of CHIKV and DENV IgG/IgM on a single lateral flow detection strip. They demonstrate that their detection can indicate the presence of anti-CHIKV IgG/IgM and anti-DENV IgG/IgM by observing the color and position of the test areas for CHIKV and DENV. Two-color lateral flow assay for multiplex IgG/IgM detection of several febrile illnesses According to the World Health Organization’s (WHO) REASURED guidelines, an ideal point-of-care testing should have real-time connectivity, ease of specimen collection, affordable, sensitive and specific, user friendly, rapid and robust, equipment-free and environment friendly, and deliverable to end-users. Lateral flow testing will therefore remain an important format for future point-of-care devices. In particular, multiplexing capabilities could represent the next generation of POC testing. One way to achieve multiplex detection in LFTs is to use uniquely labeled or differently colored detector particles (nanoscale beads responsible for visualizing signals on test strips). CD Bioparticles’ colored polystyrene beads significantly increase detection sensitivity and reduce cost, facilitating multiplexing in lateral flow applications. References Lee, S., Mehta, S., & Erickson, D. (2016). Two-color lateral flow assay for multiplex detection of causative agents behind acute febrile illnesses. Analytical chemistry, 88(17), 8359-8363. Azuma, T., Hui, Y. Y., Chen, O. Y., Wang, Y. L., & Chang, H. C. (2022). Thermometric lateral flow immunoassay with colored latex beads as reporters for COVID-19 testing. Scientific Reports, 12(1), 3905.

Antibody-drug conjugates (ADCs) are conjugated products of monoclonal antibodies (mAbs) and cytotoxic small molecules. In tumor treatment, although monoclonal antibodies have good targeting properties, most of them target extracellular or cell surface antigens, have weak anti-tumor activity, have limited therapeutic effect on solid tumors, and are more likely to develop drug resistance; conventional anti-tumor chemotherapy Although drugs have high anti-tumor cell activity, they lack targeting and often accidentally damage normal cells in the body, causing serious side effects. Antibody-drug conjugates complement each other perfectly, combining the high specificity of antibodies with the high toxicity of cytotoxic drugs to tumors. They can specifically kill tumor cells without damaging normal tissue cells, and are clinically highly effective and low-cost. Figure 1. The history of ADC development. Mechanism of Action of ADC As a new targeted drug delivery system using monoclonal antibodies as carriers, ADC consists of three parts: monoclonal antibodies, cytotoxic small molecule drugs, and antibody-drug linkers. The main function of monoclonal antibodies is as a drug carrier, controlling the targeting of ADC drugs, and targeting and enriching the “warhead” – cytotoxic small molecule drugs to the tumor site. The target antigen it binds to must be expressed with high specificity in tumor cells or tumor microenvironment. Cytotoxic small molecule drugs are the second key factor in ADC drug design. The anti-tumor effect of ADC drugs mainly depends on the killing effect of the selected cytotoxic small molecule drugs. The linker mainly acts as a bridge to stably couple the monoclonal antibody to the cytotoxic small molecule. It carries the functions of ADC stability, water solubility, and intra-tumor cell release. ADC enters the blood circulation by intravenous injection. After entering the tumor tissue, it binds to the antigen on the surface of the tumor cells. Then, under the mediation of the receptor, it is mostly endocytosis through clathrin traction and enters the tumor cell lysosome, where it is released. Cytotoxic small molecules combine with the DNA, RNA, tubulin, etc. of tumor cells, affecting their replication or mitosis, and produce anti-tumor effects. In addition to the cytotoxic effects of cytotoxic small molecules (payload), the inhibition of tumor cell receptor signaling pathways mediated by monoclonal antibodies, and the immune response mediated by the antibody Fc domain and payload can all assist the efficacy of ADCs. The selection of antibodies, target antigens, cytotoxins, linkers and conjugation methods are all critical to the success of ADC drug development. Monoclonal Antibody Selection The ADC antibody part not only serves as a cytotoxic carrier, but also assumes a targeting role, and can induce endocytosis mediated by target antigens on the surface of tumor cells. Monoclonal antibodies are generally specific monoclonal antibodies designed against target antigens on the surface of tumor cells. They are produced from a single B cell clone and have the characteristics of high purity, high sensitivity, strong specificity, less cross-reaction, and low preparation cost. Usually Prepared using hybridoma technology. In addition to having low immunogenicity, an ideal monoclonal antibody should also have the following characteristics: high specificity, that is, good targeting, the ability to specifically bind to target cells and high affinity, and after endocytosis by target cells, It results in the effective release of the carried small cytotoxic molecules; no negative feedback occurs after binding to the antigen; and its own characteristics do not change after being coupled with toxic drugs. At present, monoclonal antibodies generally choose IgG with longer half-life, mostly IgG1, IgG2 and IgG4. ADC Linker The linker that connects the antibody and the toxin must remain stable in the blood circulation for a long time to prevent the early release of toxic small molecules into the blood and cause serious adverse reactions and reduce the efficacy. After entering the cancer cells, it is necessary to ensure the effectiveness of the “warhead” cytotoxic molecules freed. ADC generally uses covalent bonds such as peptide bonds, disulfide bonds, and thioether bonds to connect monoclonal antibodies and toxic small molecules. Linkers are divided into two categories: non-cleavable and cleavable. Non-cleavable linkers have good stability, such as thioether linkers. Kadcyla, which treats breast cancer, uses a stable thioether linker to link the maytansine derivative DM1 to the antibody. According to different cleavage mechanisms, cleavable linkers are divided into chemically cleavable linkers and enzymatic cleavable linkers. The former includes hydrazone linkers, etc., and the latter includes peptide linkers, etc. Adcetris, developed and marketed by Seattle Genetics for the treatment of Hodgkin lymphoma, successfully conjugates MMAE, a synthetic derivative of the microtubule inhibitor Aplysia toxin 10, to the monoclonal antibody cAC10 using a valine-citrulline dipeptide linker. The connection methods of linkers are divided into non-fixed-point coupling method and fixed-point coupling method. Since there are a large number of functional groups on the antibody molecule, the coupling reaction can be performed at multiple sites using a non-directed coupling method. The final product of the coupled ADC is a mixture with different drug-to-antibody ratios (DAR), resulting in a complex product. The pharmacology, pharmacokinetics and pharmacodynamics are not easy to control, and the product stability is poor. The connected cytotoxic molecules are easy to fall off and cause toxic side effects. Problems are prone to occur in its analysis, identification and product quality control. These problems can be solved by using fixed-site coupling technology. This technology mostly involves modifying and transforming antibodies to connect cytotoxic molecules to specific sites on the antibody. This technology greatly improves the uniformity and purity of the ADC and can effectively control the drug-antibody ratio. As well as key quality attributes such as drug loading distribution, it facilitates analysis, identification and quality control, reduces drug side effects, and increases the drug treatment window. For Enhertu, which will be launched in 2019, and Trodelvy, which will be launched in 2020, the connection strategy of the linker is fixed-site coupling. Fixed-site coupling has become a trend in the research and development and innovation of the new generation of ADCs.

What are Dyed Polystyrene Latex Particles? Polystyrene particles (PSP) are commercially available in different sizes, ranging from 15 nanometers to several micrometers, with narrow size distributions and various surface chemistries. Additionally, polystyrene is generally considered inert and nontoxic, making it safe for use in a variety of biological assays. Dyed polystyrene latex particles or colored latex beads have excellent multiplexing capability and have the following characteristics: a. Diversity, that is, diversity of particle size, color, and color depth; b. High labeling efficiency; c. Stability, it has good chemical and physical properties in aqueous solution. These characteristics provide a strong guarantee for the rapid development and application of colored latex particles in medical diagnostic technology. Shop for Colored Polystyrene Particles Black Polystyrene Particles Red Polystyrene Particles Blue Polystyrene Particles Violet Polystyrene Particles Green Polystyrene Particles Yellow Polystyrene Particles Orange Polystyrene Particles   At present, there are three main methods for preparing colored latex particles: the first is to copolymerize dye monomers and latex monomers; the second is to prepare latex particles first, then modify them with active groups on the surface of the particles, and finally combine the dye molecules by covalent cross-linking to the particle surface; a third method is to prepare colored latex particles by physically trapping or absorbing dye molecules. Immunochromatographic Assay: Leveraging Colored Polystyrene Particles (Adapted from Wang, J, 2021) Immunochromatographic assay (ICA), also known as lateral flow assay (LFA), is a rapid analysis technology with simplicity, speed, and sensitivity advantages. ICA is one of the most successful and widely used point-of-care tests (POCT) and has been successfully used for human chorionic gonadotropin (hCG) detection, serodiagnostic assays, cancer detection, cardiac markers and infectious microorganism detection. ICA has been widely used in many fields such as medicine and food safety. To enhance the sensitivity of colorimetric ICA, labeled nanomaterials need to exhibit deep and bright color signals. Utilizing new colored nanomaterials as labeled probes is an important strategy to improve sensitivity. Wang et al. developed crimson red 0.2000 µm polystyrene microspheres (PMs)-based ICA for sensitive and quantitative detection of AFB1 in corn. PMs-ICA is more sensitive than CG (colloidal gold)-ICA, and results can be obtained with the naked eye rather than using a reader. Nagaoka et al developed a new visual immunodiagnostic method using red latex beads to detect urinary IgG4. Taking those with ICT antigen test positive as the standard (136/156), the sensitivity is 87.2%. Comparing gold nanoparticles with latex beads, it can be observed that lateral flow assays using latex beads on the conjugation pad have higher sensitivity and specificity than assays using gold nanoparticles. Latex Agglutination Assays: The Role of Dyed Polystyrene Particles Latex agglutination is the change in agglutination capacity observed when a sample containing a specific antigen is mixed with antibodies coated on the surface of latex particles. Agglutination can also be reversed by coating latex particles with specific antigens and testing the sample for the presence of specific antibodies. Latex agglutination assays have the advantage of rapid results, often determined within minutes, and this type of reaction does not require expensive equipment to evaluate the sample. A user-friendly latex agglutination assay was developed and evaluated for the serodiagnosis of human brucellosis. The assay was obtained by coating blue latex beads with Brucella lipopolysaccharide and drying the activated beads onto a white agglutination card. For initial serum samples collected from patients with culture-confirmed brucellosis, the assay had a sensitivity of 89.1% (95% CI, 76-96) and a specificity of 98.2% (95% CI, 96-99). Grace et al. developed a rapid diagnostic test for porcine JEV diagnosis and serosurveillance using violet-dyed polystyrene beads (0.80 μm) that can be easily applied in the field and is useful to fill the gap between existing diagnostic methods and surveillance programs. Advantages of Colored Polystyrene Particles in Immunoassays Latex particles formed from amorphous polymer (usually polystyrene) represent a class of particles that have applications in many different aspects of biotechnology. These monodisperse particles range in size from 20 nm to 160 µm, with 100-400 nm covering the typical range used in lateral flow immunoassays. Colored polystyrene beads are inexpensive. Second, because they are doped with organic dyes, they are available in a variety of colors, with red, blue, black, and green being the most popular choices for lateral flow assays. The versatility of latex particles in color selection and compatibility with many biological matrices make them ideal candidates for labeling in many lateral flow immunoassays. References Nagaoka, F., Itoh, M., Samad, M. S., Takagi, H., Weerasooriya, M. V., Yahathugoda, T. C., … & Kimura, E. (2013). Visual detection of filaria-specific IgG4 in urine using red-colored high density latex beads. Parasitology international, 62(1), 32-35. Wang, J., Li, X., Shen, X., Zhang, A., Liu, J., & Lei, H. (2021). Polystyrene microsphere-based immunochromatographic assay for detection of aflatoxin B1 in maize. Biosensors, 11(6), 200. Abdoel, T. H., & Smits, H. L. (2007). Rapid latex agglutination test for the serodiagnosis of human brucellosis. Diagnostic microbiology and infectious disease, 57(2), 123-128. Grace, M. R., Dhanze, H., Pantwane, P., Sivakumar, M., Gulati, B. R., & Kumar, A. (2019). Latex agglutination test for rapid on-site serodiagnosis of Japanese encephalitis in pigs using recombinant NS1 antigen. Journal of Vector Borne Diseases, 56(2), 105-110.

As a promising systemic drug delivery method, transdermal drug delivery system (TDDS) is easier and more convenient to operate than traditional oral, intravenous and subcutaneous injection methods. It can improve patient compliance while also avoiding First-pass effect and drug side effects. As the largest organ of the human body, the skin is also the body’s first line of defense against foreign microorganisms and chemical substances. Its drug permeability is lower, which is orders of magnitude different compared to the epithelial cells of the gastrointestinal tract and lungs. Therefore, how to pass through the many barriers of human skin is the first problem faced during transdermal drug delivery. In the past 20 years, with the continuous development of nanotechnology, various nanoformulations have been increasingly used in transdermal drug delivery. These nano-preparation transdermal delivery systems can greatly enhance the penetration of drugs into the skin and improve the transdermal efficiency of drugs due to their nanoscale size and unique physical and chemical properties. This article will review the overview, preparation methods, advantages and research progress of various nano-preparation transdermal delivery systems based on the literature in recent years. Skin Barrier Skin Physiological Structure Human skin is composed of three layers with different compositions and structures. From the outside to the inside, they are the epidermis, dermis and subcutaneous tissue. In addition, there are hair follicles, sweat glands, sebaceous glands and other appendages. The epidermis can be divided into stratum corneum (SC), stratum lucidum, stratum granulosum, stratum spinosum and stratum basale from outside to inside. The four layers except the stratum corneum are composed of living cells and are collectively called the active epidermis; the stratum corneum is mainly composed of dead and dehydrated anucleate keratinocytes and the lipid matrix between keratinocytes. The internal structure of the stratum corneum is tightly packed and highly hydrophobic, which allows it to play a major role in the skin’s permeability barrier. The structure of the stratum corneum is often simply represented as a “bricks and mortar” model, in which keratinocytes are stacked and staggered like bricks, and a lipid matrix fills the gaps between keratinocytes, but this model is not entirely accurate. New models of lipid matrices include asymmetric (bilayer unfolding) models, domain mosaic models, sandwich models, single gel phase models, etc., which better describe the architecture of lipid matrices. The dermis under the epidermis is composed of fiber network, matrix and cells. The fiber network is a dense network structure formed by collagen, elastin, etc., which can provide mechanical strength to the skin; the matrix is mainly composed of a variety of hydrophilic proteoglycans, filling Between the fiber network; the cells in the dermis are mainly fibroblasts, followed by immune cells such as macrophages, mast cells, and dendritic cells, which are responsible for the immune response of the skin. In addition, the roots of capillaries, lymphatic vessels, nerve endings, and various appendages are also in the dermis. The subcutaneous tissue in the deepest layer of the skin is mainly composed of loose connective tissue and fat, which plays a role in buffering and energy storage. Figure 1. Barriers to transdermal drug delivery and strategies to overcome them. Skin Absorption Route The pathways through which drugs enter the systemic circulation through the skin include the epidermal pathway and the adnexal pathway]. The epidermal pathway is the process in which drugs penetrate the epidermis into the dermis, then diffuse into capillaries and then transfer to the systemic circulation. The epidermal pathway includes the transcellular pathway and the interstitial pathway, in which drugs diffuse across keratinocytes and through the lipid matrix between keratinocytes, respectively. In the epidermal pathway, drugs are mainly transported by passive diffusion through the concentration difference between the skin surface and the deep skin layer, and the special composition and structure of the stratum corneum make it the main barrier for drug transport. In the adnexal route, the drug enters the dermis directly through the openings of the skin appendages and reaches the systemic circulation. Generally speaking, the epidermal pathway is the main pathway for drug transdermal absorption. Although the adnexal pathway has a faster penetration rate, the appendages only account for 0.1% of the skin surface area. Therefore, when drugs are absorbed through the epidermal pathway, after steady state is reached, uptake by the adnexal pathway can be neglected. However, ionic drugs and hydrophilic macromolecule drugs are extremely difficult to penetrate into the stratum corneum, so these drugs are mainly absorbed through the adnexal pathway. In addition, nanopreparations such as lipid nanoparticles (LN), polymeric nanoparticles (PNP), and nanocrystals (NC) can aggregate in hair follicles to form drug reservoirs and accelerate drug transdermal absorption through the adnexal pathway. Nanoformulation Transdermal Delivery System Nanopreparations refer to drug carriers or drug particles with a size below 1000 nm, and their nanosize can bring unique physical and chemical properties. Nanoformulations commonly used in transdermal delivery systems in current research include nanoemulsion, lipid-based nano-vesicles, LN, PNP, NC, lyotropic liquid crystal (LLC), etc.. These nanopreparations provide a new platform for transdermal delivery through unique penetration promotion mechanisms and drug release mechanisms. Their advantages and disadvantages in drug transdermal delivery and formulation preparation are as follows: Nanoemulsion Advantage The preparation process is simple and easy to expand; Has a sustained release effect; Reduce drug irritation and side effects Shortcoming Poor thermodynamic stability, leading to aggregation, flocculation and other phenomena; The potential biological toxicity of some non-natural emulsifiers needs to be further studied. Lipid Nanovesicles Advantage Strong lipophilicity and easy to penetrate the stratum corneum; It has strong elasticity and deformability and can pass through skin pores completely; It can be loaded with both hydrophilic and lipophilic drugs; Can be used as a drug storage to extend the residence time Shortcoming The preparation is time-consuming, costly and low-yield, making it unsuitable for large-scale ?production. Lipid Nanoparticles Advantage The drug loading rate is high and the drug can be maintained at a high concentration on the skin surface and tissues for a long time; Improve drug stability and reduce drug irritation to skin; Strong occlusive effect, which can reduce skin moisture loss and facilitate drug penetration Shortcoming There are problems with particle size growth, gelation, and drug precipitation during storage; Some drugs have a burst release phenomenon Polymer Nanoparticles Advantage Improve drug stability, reduce drug degradation and denaturation, and reduce drug irritation; Form a drug reservoir in the hair follicles, release it sustainably, and reduce the side effects of toxic drugs; Targeted drug delivery can be achieved through surface modification Shortcoming Solvent residue is prone to occur during the preparation process; Some polymers have cytotoxicity issues Nanocrystals Advantage Composed of pure drugs, the drug loading rate is close to 100%; The dosage of stabilizer is low, the local irritation is small, and the safety is high; The preparation process is mature and perfect, easy for large-scale production Shortcoming Physical stability is poor, with aggregation and settling, Ostwald ripening, Phenomenon such as crystal transformation Lyotropic Liquid Crystal Nanoparticles Advantage High bioadhesion, can adhere to the skin surface and release drugs for a long time; Good biocompatibility; There is a wide range of drug candidates that can be loaded, which has the advantage of drug loading; High stability and can exist stably in excess water Shortcoming The intermediate product has high viscosity and requires high preparation process; The quality standards of preparation materials need to be established and improved, and the preparation process needs to be industrialized.

What is Zeta Potential? Figure 1. Electrical double layer at the surface of solution-phase nanoparticles. Zeta potential (ZP) is a physical property exhibited by any particle in a suspension, macromolecule or material surface. ZP is an analytical technique used to determine the surface charge of nanoparticles in colloidal solutions. The surface of a charged particle attracts and binds firmly to a thin layer of opposite charge, forming a thin layer of liquid called the Stern layer; as the particle diffuses in the solution, it will be replaced by a thin layer of loosely bound ions. The outer diffusion layer is involved, resulting in an electric double layer (Figure 1). Zp is named after the potential of the electric double layer and is determined by measuring the speed of charged particles moving through the sample solution toward the electrode in the presence of an external electric field. ZP values are typically in the range of +100 to −100 mV. The magnitude of the ZP gives a prediction of colloidal stability. The ZP of NPs with values >+25 mV or <−25 mV is generally highly stable. Lower dispersion ZP values can lead to aggregation, coagulation or flocculation due to van der Waals attraction between particles. Zeta potential can be used to optimize the formulation of suspensions, emulsions and protein solutions, predict interactions with surfaces, and optimize the formation of films and coatings. Understanding zeta potential can reduce the time required to produce pilot formulations. It can also be used as an aid in forecasting long-term stability. Factors Affecting Zeta Potential The most important factor affecting the zeta potential is the pH value of the medium. Other factors include ionic strength, concentration of any additives, and temperature. pH The pH level can have a significant impact on the potential value of zeta potential. If a material’s surface chemistry has polar functional groups, then pH is the most critical factor affecting zeta potential. Due to the effect of pH on zeta potential results, all zeta potential results should correspond to the pH of the sample during analysis. Zeta potential without correlating pH is effectively meaningless. When diluting a sample for zeta potential analysis, it is important to maintain the pH at which the sample was pre-diluted so as not to affect the zeta potential of the suspension. Ionic strength The conductivity of a solution is related to the free ions in the solution. The concentration of available ions forming a double layer around the particle will affect the potential at the slip plane, and the potential at the slip plane directly affects the Zeta potential value. The pH of the solution has a greater impact on the zeta potential, but the ionic strength also plays a role in the overall zeta potential. Temperature Zeta potential is affected by temperature because both particle mobility and viscosity are affected by temperature changes. Zeta Potential Measurement Although the zeta potential cannot be measured directly, it can be calculated using theoretical models. Electrokinetic phenomena and electroacoustic phenomena are common sources of data for calculating zeta potential. The zeta potential of a dispersion is measured by applying an electric field across the dispersion. Particles with a zeta potential in the dispersion will migrate toward the oppositely charged electrode at a rate proportional to the magnitude of the zeta potential. There are two different experimental techniques: microelectrophoresis, which has the advantage of producing images of moving particles, and electrophoretic light scattering, which is based on dynamic light scattering. The latter can be used to characterize very small particles. The frequency shift or phase shift of the incident laser beam caused by these moving particles is measured as the mobility of the particles, and this mobility is converted into the Zeta potential using Smoluchowski or Huckel theory. Significance of Zeta Potential Pharmaceutical industry Nanoparticle surface is a very important factor in targeted drug delivery. Indeed, once in the bloodstream, conventional nanoparticles (no surface medication) and negatively charged particles can be rapidly opsonized and cleared in large quantities by fixed macrophages. Surface modification of these polymeric nanoparticle systems with hydrophilic polymers is the most common method to control the opsonization process and improve the surface properties of the system, especially the surface charge. Zeta potential, determined by surface charge, is very important for the stability of nanoparticle suspensions and is a major factor in the initial adsorption of nanoparticles to cell membranes. After adsorption, the endocytic uptake rate depends on particle size. Zeta potential and size therefore influence the toxicity of nanoparticles. Cosmetics industry Emulsions are one of the most commonly used vehicles in skin care because of their strong affinity to the skin and the variety of formula benefits they can provide. However, emulsions are thermodynamically unstable systems. Zeta potential can be used to predict emulsion instability and control the behavior of colloidal suspensions/emulsions. Environmental science Suspended solids are common impurities in industrial and mining wastewater. Safety and aesthetics require that all water be essentially free of suspended solids. To meet water clarity requirements for reuse or discharge, suspended solids are often allowed to settle to the bottom or cream to the top of large tanks. The duration of these processes is strongly related to particle size, e.g. larger particles settle/cream faster. Therefore, if the particles can be made to agglomerate, the sedimentation process will be shorter and therefore the treatment operation will be faster and therefore cheaper. Additives can reduce the magnitude of the particle surface charge (zeta potential) to zero. This increases the number of particle collisions, thereby increasing the rate of flocculation. Therefore, zeta potential measurement can be used to monitor the effect of coagulant addition. The results are then used to optimize the treatment process. Accessing Highly Stable Particles CD Bioparticles offers a range of basic silica particles with terminal hydroxyl groups which give silica colloids a large negative zeta potential at neutral and basic pH. We also have plain fluorescent polystyrene particles with positive/negative/neutral zeta potential for your research. Reference Rasmussen, M. K., Pedersen, J. N., & Marie, R. (2020). Size and surface charge characterization of nanoparticles with a salt gradient. Nature communications, 11(1), 2337.

Hydrogel is a three-dimensional network of hydrophilic polymers that swells in water without dissolving. Because the polymer contains a large number of hydrophilic groups, the hydrogel can absorb and lock a large amount of water. After absorbing water, the hydrogel network can maintain its original shape without being destroyed. Hydrogels are widely used in tissue engineering, drug delivery, biosensing, etc. due to their simple preparation, strong tunability of mechanical properties, good biocompatibility, and elasticity and softness that are very similar to most tissues and extracellular matrices of the human body. The field is developing rapidly. Depending on the source from which the hydrogel is prepared, hydrogels can be divided into natural hydrogels and synthetic hydrogels. Due to society’s demand for sustainable products, hydrogels derived from natural materials, especially those from renewable resources, have attracted attention. Among renewable resources, polysaccharides have become the most promising hydrogel precursors due to their inherent hydrophilicity and biodegradability. Carrageenan is a sulfated polysaccharide extracted from red algae. It is composed of alternating units of D-galactose and 3,6-anhydrogalactose linked by α-1,3 and β-1,4-glycosidic bonds. Carrageenan is divided into 6 basic forms according to its sulfate content, extraction source and solubility, namely: k-carrageenan, t-carrageenan, λ-carrageenan, μ-carrageenan, ν-carrageenan and θ-carrageenan. K-carrageenan, t-carrageenan and λ-carrageenan have important commercial value due to their gelling and viscoelastic properties. t-carrageenan and k-carrageenan have the ability to form hydrogels and form a three-dimensional double helix network through cross-linking of adjacent sulfate groups. However, the sulfate groups of λ-carrageenan do not cross-link and therefore do not form a gel. The presence of hydroxyl/sulfate groups on carrageenan makes it easy to undergo physical or chemical cross-linking, giving carrageenan better physical and chemical properties, new special functions and characteristics. Carrageenan hydrogel has been widely used in biomedicine and tissue engineering fields, such as drug delivery, wound dressings, tissue engineering scaffold materials, etc. This article reviews several types of carrageenan hydrogels and their application progress in the biomedical field. Figure 1. Recent advances in chemically-modified and hybrid carrageenan-based platforms for drug delivery, wound healing, and tissue engineering. Several Types of Carrageenan Hydrogels Traditionally, k-carrageenan and t-carrageenan form brittle hydrogels through ionic cross-linking in the presence of K+ and Ca2+ respectively. In order to improve the performance of carrageenan, one of the measures is to change the cross-linking method. Physical cross-linking is cross-linking through non-chemical bonds such as hydrogen bonding van der Waals forces or mutual entanglement. Chemical cross-linking is the connection between chains through chemical bonds. By compounding carrageenan with polymer materials such as polyvinyl alcohol, gelatin, cellulose, and silk fibroin, a hydrogel with excellent performance can be obtained through a certain cross-linking method (physical cross-linking, chemical cross-linking based on cross-linking agents). On this basis, researchers have studied different types of carrageenan hydrogels, including photo-crosslinked hydrogels, interpenetrating polymer network hydrogels, hydrogel scaffolds, nanogels and 3D bioprinting bioinks etc. Photo-crosslinked Hydrogel Photo-crosslinking usually introduces methacrylic acid groups into the carrageenan structure, then adds a photoinitiator to make it photosensitive, and finally cures and cross-links it through ultraviolet or visible light irradiation. Interpenetrating Polymer Network Interpenetrating polymer networks (IPNs) are “alloys” of cross-linked polymers in which at least one polymer is synthesized and/or cross-linked in the direct presence of another polymer without any covalent connection between them. polymers cannot be separated unless the chemical bond is broken. One network structure in the interpenetrating polymer network is rigid and brittle, and the other is soft and tough. When stressed, the rigid and brittle network mainly bears the force, while the soft and tough network mainly prevents the gel from breaking. Hydrogel Scaffold The gel scaffold has excellent surface adhesion, promoting cell adhesion, proliferation and differentiation; it also has a highly porous structure, which can provide sufficient space for cell adhesion and stimulate new tissue growth. Researchers have used various physical and chemical methods to develop carrageenan gel scaffolds that can simulate the natural extracellular matrix (ECM) in the body. Nanogel “Nanogel” refers to a nanohydrogel with a size range of 1 to 1000 nm formed by a physical or chemical cross-linked network. The carrageenan nanogel network can encapsulate drugs, proteins, DNA, etc., providing a large surface area for multivalent biological binding. Bioink for 3D bioprinting 3D bioprinting is a versatile layer-by-layer manufacturing technology that directly guides the gradual addition of materials (bioink) through a predefined digital model to create 3D objects. It can use living cells to create complex tissue structures. Carrageenan has the properties of biocompatibility, biodegradability, shear dilution and ionic gelation, but its gelation properties are difficult to control and is not suitable for use in 3D bioprinting. Researchers have made it suitable for 3D bioprinting by introducing methacrylates, cationic polymers (such as gelatin) and other substances into the carrageenan structure. Application of Carrageenan in Biomedical Field Wound Dressing An ideal wound dressing is nontoxic, antibacterial, keeps the skin surface moist, has a good effect on absorbing wound toxins and accelerates wound healing, and does not cause any trauma to the healing skin when removed. In addition to its biodegradability, biocompatibility and significant swelling properties, carrageenan also exhibits high ductility and can better contact with the skin, making it an ideal wound dressing. Drug Delivery Drug delivery plays a key role in continuously delivering medications or key ingredients, including antimicrobials, to wounds. Drug delivery systems can deliver therapeutic drugs to target sites in organs and tissues in a better way. Carrageenan has good biocompatibility, adjustable viscoelasticity, simple gel mechanism and thermally reversible gelation, and has good drug release ability. Therefore, carrageenan-based hydrogels are promising materials for drug delivery systems. Tissue Engineering Three-dimensional cell culture plays an important role in tissue repair, replacement or regeneration. Extracellular matrix (ECM) is an important component that produces different types of cells and is the basis of special tissues. To be used in 3D cell culture, biomaterials must imitate the characteristics of the extracellular matrix. Carrageenan is a natural polysaccharide with a similar structure to natural glycosaminoglycans and is one of the important components of tissue extracellular matrix. Bio-intelligent Sensing Biosensing is usually the detection of biomolecules with the help of biosensors (analytical devices). These biosensors combine biological components such as sweat, saliva or other vital body fluids with a physicochemical detector. Sensors have received increasing attention due to their portability, extremely short diagnostic time, and reduced sample preparation requirements. In recent years, carrageenan hydrogel has made breakthrough progress in health monitoring as an intelligent wearable sensing device.

Surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) are two key surface plasmon technologies that ultimately enable single-molecule-level chemical and biological sensors. Due to the tremendous progress in solution-based synthesis methods, plasmonic nanoparticles with various complex shapes (e.g., spheres, rods, and prisms) have been widely used for surface plasmon resonance and surface-enhanced Raman scattering sensing. Localized surface plasmon resonance (LSPR) around plasmonic nanoparticles enables very high SERS enhancement and SPR sensitivity. What are Plasmonic Nanoparticles? Materials such as nanoparticles, nanorods, and nanotubes that exhibit optical properties at the nanometer scale are called plasmonic nanoparticles. Plasmons can be defined as when a metal nanoparticle interacts with light whose size is smaller than or equal to the wavelength, and the free electrons begin to resonate at a certain frequency, called the plasmon resonance frequency. Plasmon resonance is a material property that depends on the shape, size, composition and environment of the nanoparticle. Another viable option for modifying plasmon resonances is the synthesis of multimetallic nanoparticle composites. Metal nanoparticles of gold (Au), platinum (Pt), and silver (Ag) exhibit high light absorption and light scattering behaviors. Gold and silver nanoparticles display unique spectral responses due to their specific wavelengths of light that can drive collective oscillations of conducting electrons. At the resonance of these plasmonic nanoparticles, their absorption and scattering intensity can be 40 times higher than that of non-plasmonic particles. The tunability and brightness of these nanoparticles make them useful in molecular tracking, imaging, and detection. Applications of Plasmonic Nanoparticles In vitro biosensors Detection of biomolecules at nanomolar concentrations is now common in biological laboratories due to the high specificity of antibodies working in conjunction with a variety of labels, including radioisotopes, enzymes, and phosphorus. Single-antibody or sandwich-based detection methods (i.e., ELISA) have been successfully used in combination with plasmonic nanoparticle-labeled antibodies, particularly in areas where low detection sensitivity is required. Antibodies can be covalently bonded to plasmonic nanoparticles using various methods, such as EDC/NHS chemistry-based amide bonding, maleimide groups, and disulfide bonds. Intracellular detection and ex vivo/in vivo imaging SERS can provide very rich information about the intracellular environment and organelles. However, a challenging issue in applying SERS to cellular systems is how to successfully inject NPs into living cells and maintain effective and detectable SERS signals. The composition of cells and their ability to take up NPs varies greatly depending on the cell type or tissues from which the cells are obtained. Yashchenok et al. used functionalized colloidal particles to probe the intracellular environment. The designed probes are based on the SERS proximity effect or “hotspot” effect of gold nanoparticles and carbon nanotubes to respond to biomolecules in cells, and both are chosen with both functionality and biocompatibility in mind. Therapeutic applications The applications of plasmonic nanoparticles are not limited to sensing and imaging but also exhibit excellent performance in photothermal systems. Because cancer cells lack a general blood supply, delivering drugs to tumor cells for testing or treatment is a major problem. To reduce damage to healthy cells, ligands capable of targeting target tumor cells are attached to the surface of the nanoparticles. The El-Sayed group reported the use of gold nanorods (Au NRs) for near-infrared-triggered photothermal therapy of HSC-3 tumor cells. First, antibody-labeled Au NRs were used for selective labeling of tumor cells in vitro. When these Au-NRs serve as photothermal contrast agents attached to the cell membrane, near-infrared laser irradiation causes hyperthermia effect and subsequently induces cell apoptosis. Accessing Plasmonic NPs Plasmonic nanoparticles have unique optical and physical properties that enable higher sensitivity for in vitro detection and intracellular or in vivo imaging at the nanoscale. These plasmonic nanomaterials in biology and medicine offer new and exciting approaches. CD Bioparticles offers a series of novel gold nanoparticles, silver nanoparticles, and gold nanostars, as a plasmonic core, for SERS-based lateral flow immunoassay. References Dou, X., Chung, P. Y., Jiang, P., & Dai, J. (2012). Surface plasmon resonance and surface-enhanced Raman scattering sensing enabled by digital versatile discs. Applied Physics Letters, 100(4). Willets, K. A., & Van Duyne, R. P. (2007). Localized surface plasmon resonance spectroscopy and sensing. Annu. Rev. Phys. Chem., 58, 267-297. Liu, J., He, H., Xiao, D., Yin, S., Ji, W., Jiang, S., … & Liu, Y. (2018). Recent advances of plasmonic nanoparticles and their applications. Materials, 11(10), 1833. Yashchenok, A., Masic, A., Gorin, D., Shim, B. S., Kotov, N. A., Fratzl, P., … & Skirtach, A. (2013). Nanoengineered Colloidal Probes for Raman?based Detection of Biomolecules inside Living Cells. Huang, X., El-Sayed, I. H., Qian, W., & El-Sayed, M. A. (2006). Cancer cell imaging and photothermal therapy in the near-infrared region by using gold nanorods. Journal of the American Chemical Society, 128(6), 2115-2120.