Carboxyl Microspheres
Overview
Carboxyl microspheres are polymer particles functionalized with carboxyl (–COOH) groups on their surface, enabling covalent bonding with amino-containing molecules via EDC/NHS chemistry. They are synthesized from materials like polystyrene, silica, or magnetic cores, with diameters ranging from nanometers to micrometers. These microspheres are essential tools in life sciences and diagnostics due to their high surface area, stability, and tunable reactivity. Their uniform size and surface chemistry make them ideal for quantitative assays, drug delivery systems, and as solid supports for enzymatic reactions.
Physical and Chemical Properties
Carboxyl microspheres exhibit a negatively charged surface at neutral pH (pKa ~4–5), facilitating electrostatic interactions. Their density is slightly higher than water, allowing easy centrifugation-based separation. The carboxyl group density typically ranges from 0.1 to 1.0 meq/g, customizable for specific applications. Key advantages include low non-specific binding and compatibility with organic solvents. Particle size uniformity (CV <5%) ensures reproducible results in assays. Surface carboxylation is verified via titration or FTIR spectroscopy, with zeta potential measurements confirming colloidal stability.
Main Applications
In diagnostics, carboxyl microspheres serve as carriers for antibodies in lateral flow tests (e.g., pregnancy or COVID-19 rapid tests). They are also used in ELISA, flow cytometry, and magnetic cell sorting (when combined with iron oxide cores). Biomedical research utilizes them for DNA/RNA immobilization, protein purification, and targeted drug delivery. Industrial applications include coatings, sensors, and as additives in composites to enhance mechanical properties or enable functional surfaces.
Safety and Storage
While non-toxic, dry powder forms may cause respiratory irritation; use fume hoods and N95 masks. Aqueous suspensions often contain preservatives (e.g., sodium azide) requiring careful disposal. Store at 2–8°C to prevent aggregation; avoid freeze-thaw cycles. For long-term stability, lyophilized formulations are available. Shelf life is typically 12–24 months. Always centrifuge suspensions before use to ensure homogeneity, and sonicate briefly if aggregation occurs.
B2B Procurement Guide
For bulk purchases (>100g), request batch-specific certificates of analysis (CoA) detailing size distribution, carboxyl content, and endotoxin levels. Compare suppliers’ quality control methods—dynamic light scattering (DLS) for size and FTIR for functional group verification are standard. Consider custom modifications like fluorescent labeling or magnetic cores for specialized applications. Lead times for OEM orders vary from 4–12 weeks. For research-grade microspheres, Thermo Fisher, Merck, and Polysciences are reputable suppliers.
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