Characterization methods for studying protein adsorption on nano-polystyrene beads

This work is dealing with the use of polystyrene (PS) nanoparticles as substrates for bioanalytical specific interactions. Different techniques were used for the accurate characterization of the PS nanoparticles of 100 nm and 196 nm before coating them with a layer of antibodies against immunoglobulins of type E (aIgE), giving to the particle a specific functionality. The formation of the aIgE adsorbed layer was monitored using centrifugal particle separation (CPS) and centrifugal field flow fractionation (CF3) experiments, which allowed to determine the size changes and the adsorbed mass. Particle sizes were also measured with DLS, used both as stand-alone instrument and coupled to CF3 (CF3-DLS). The complementary information obtained from the CPS and CF3-DLS measurements allowed the estimation of the density of the aIgE shell. The proteins immobilized at the surface fully retained their activity, as proven by the reactions between the functionalized PS-aIgE particles and immunoglobulins of type E (IgE) dispersed in suspensions prepared on purpose.