Characterization of Protein Adsorption and Immunosorption Kinetics in Photoablated Polymer Microchannels

A preliminary characterization of protein adsorption and immunosorption kinetics carried out in polymer microchannels is reported. A photoablated poly(ethylene terephthalate) (PET) surface and a PET/polyethylene sealing laminate were used for the channel microfabrication. The surface state of the PET channel substrate and PET/polyethylene lamination were analyzed by using SEM and ATR-FTIR spectroscopy techniques. Protein adsorption and immunosorption studies were carried out using staphylococcal enterotoxin B (SEB) and polyclonal anti-SEB antibody (Ab) samples. Affinity purified polyclonal rabbit (Rb) anti-SEB Ab was radioiodinated and adsorbed in the microchannel. It was determined that the maximum amount of adsorbed antibody was about 13.0 pmol·cm^-2 (about 2 μg·cm^-2), which corresponds to 0.81 pmol per microchannel. The distribution of the adsorbed protein on the walls of the microchannel depended on the surface state of the polymer exposed to the solution. The amount of the radiolabeled antibody adsorbed on the photoablated PET was about 19.4 pmol·cm^-2, whereas it was only 5.5 pmol·cm^-2 on the PET/polyethylene lamination. About 30% of the anti-SEB Ab adsorbed on the microchannel surface was found to be biologically active. A study of the kinetics of the SEB−anti-SEB Ab immunochemical reaction was also carried out. It could be substantiated that the forward reaction is diffusion controlled and that the equilibrium for such a reaction could be achieved within about 1 min in the microchannels. This is in good agreement with the calculation of a diffusion-controlled reaction in such a microchannel, according to Fick's second law.