Carboxyl Polystyrene Particles, 2.5% w/v, 0.05-0.1 µm

• Carboxyl or Amino functionalized particles are very useful for covalent coupling of proteins, ligands, antibodies or antigens to the surface of the microparticles using water soluble carbodiimide as the coupling agent. Below is a diagram of antibody and protein coating of carboxyl and amino particles using EDC coupling. • Varying particle surface charges can be obtained using functionalized particles such as hydroxyl, sulfate and dimethylamino. These particles are used to manipulate the orientation of the coated material by passive adsorption. • Polyclonal antibodies can be coated to polystyrene particles by passive adsorption. According to our experience, the optimal amount of antibody to particles ratio is ~100μg of antibody per mL of 0.5%w/v (5mg solid per mL) of 0.8μm polystyrene. Since the total surface area of the particles is inversely proportional to the diameter of the particles, the amount of antibody to particles ratio needs to be adjusted accordingly. • The washing of polystyrene particles to remove unbound proteins or ligands during coating is accomplished by centrifugation or tangential flow filtration for particles with size of 0.4μm or larger. For smaller size particles gel filtration, dialysis, or tangential flow filtration should be used.