Protein capture performance of microfluidic system: effects of a super hydrophilic coating

Abstract This paper outlines the coating of polymethylmethacrylate (PMMA) with a 316 stainless-steel (SS) thin film to create a super hydrophilic microfluidic system for the capture of hydrophilic bovine serum albumin (BSA) protein. Scanning electron microscopy and atomic force microscopy images revealed a nanopyramid structure on the SS coating, which significantly increased the surface roughness, compared to that of PMMA. Measurements of water contact angle (6.06°) and PBS contact angle (7.14°) confirmed the super hydrophilic nature of the coated surface. The positive zeta potential of SS (−7.58 mV and −5.2 mV) exceeded that of PMMA (−21.73 mV and −22.78 mV) at pH 6.8 and 7.4, respectively. High surface roughness, super hydrophilicity, and positive surface potential make SS coating an ideal candidate for the capture of BSA protein. In spiral channel experiments, high fluorescence intensity confirmed the efficient capture of BSA. In linear channel experiments, the maximum capture efficiency of SS (72.58%) exceeded that of PMMA and increased in a dose-dependent manner. The excellent protein capture performance can be attributed to the large contact area resulting from a rough surface and correspondingly high surface area-to-volume ratio.