SURFACE ACTIVATION OF POLY(METHYL METHACRYLATE) BY PLASMA TREATMENT: STABLE ANTIBODY IMMOBILIZATION FOR MICROFLUIDIC ENZYME-LINKED IMMUNOSORBENT ASSAY

With the aim of obtaining stable antibody immobilization on the poly(methyl methacrylate), PMMA channel surface, PMMA substrates were activated with O-2 plasma treatment to introduce surface polar groups on it. The plasma-treated PMMA surfaces were characterized using water contact angle measurement, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). It was observed that plasma treatment significantly improved the surface wettability with changing surface chemistry and topography. The strategy of immobilization of a model antibody, anti-goat IgG on plasma-treated PMMA involved two steps. First the plasma-treated PMMA was functionalized with (3-aminopropyl)thriethoxy silane, APTES off-chip which facilitated covalent capturing of antibody via a crosslinking agent in the inner surface of PMMA channel in the second step. The antibody immobilization on plasma-treated PMMA was also confirmed using AFM, XPS, and fluorescence microscopy. The anti-IgG covalently captured on channel surface was evaluated with sandwich ELISA protocol on-chip using fluorescence microscopy. The observed results demonstrate that this technique could be extended to integrate the current diagnostic techniques into the plastic chip for important biomarker diagnosis.