Influence of poly(propylene sulfide-block-ethylene glycol) di- And triblock copolymer architecture on the formation of molecular adlayers on gold surfaces and their effect on protein resistance: A candidate for surface modification in biosensor research

Control of nonspecific interactions between bioanalytical surfaces and proteins in the analyte is critical in the design of biosensor systems. Here we explore poly(propylene sulfide-block-ethylene glycol) (PPS-PEG) di- and triblock copolymer adlayers on gold to gain such control. Chemisorption of the PPS block permits a simple dip-and-rinse coating process. We synthesized different architectures of di- and triblock copolymers, varying the molecular weight of PEG between 1.1 and 5 kDa while keeping the PPS block constant at around 4 kDa, thus permitting systematic variations in ethylene glycol surface density in the adlayer. A simple dip-and-rinse process was used to produce PPS-PEG adlayers on gold substrates, which were characterized with surface plasmon resonance (SPR) and further confirmed by ex situ variable angle spectral ellipsometry (VASE), and X-ray photoelectron spectroscopy (XPS). Crowding in the PPS chemisorbed layer seemed to limit the polymer adsorption process. Subsequent exposure of PPS-PEG adlayers to protein adsorption (human serum albumin at 1 mg/mL or full-concentration human serum) was monitored with in situ SPR. Protein adsorption can be reduced up to 97% for human serum albumin and up to 96% for blood serum relative to bare gold substrates. Triblock copolymers were more effective than corresponding diblocks. The possibility to render gold surfaces bioinert is the basis for application in bioanalytical devices.