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

Abstract

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.

Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

“…We have already confirmed the usefulness of the oligoamine anchor 15,16,26,27,56,[72][73][74][75][76] instead of the sulfanyl group anchor [77][78][79] for molecular immobilization on gold surfaces and developed polyamineended PEG-modified gold surfaces using PEG-block-poly [2- Densely PEG-chain-tethered biointerface Y Nagasaki platform for ssDNA immobilization and detection; 73 in our scheme, PEG-b-PAMA was immobilized onto the gold surface followed by treatment with a ssDNA-SH, resulting in the formation of ssDNA-SH/ PEG-b-PAMA co-immobilized gold surface.…”

Load-Induced Transitions in the Lubricity of Adsorbed Poly(l-lysine)-g-dextran as a Function of Polysaccharide Chain Density

“…The "dry" thickness of PLL-g-dex was obtained by fitting the VASE spectra to a multilayer model based on the optical properties of a generalized Cauchy layer (A = 1.45, B = 0.01, C = 0). 29 The results of ellipsometric characterization of a PLL-g-dex surface-chemical gradient are shown in Figure 2A. The dry thickness of the copolymer layer ranges from below the experimental scatter of SiO 2 thickness (0.1 Å) at the bare end to 16 ( 1 Å, corresponding to the maximum thickness for this particular PLL-gdex architecture.…”

Poly(l-lysine)-grafted-poly(ethylene glycol)-based surface-chemical gradients. Preparation, characterization, and first applications

“…The protein resistance of PEG modified surfaces is attributed mainly to entropic repulsion and the high water content of the PEG chains. Among other methods, PEG chains may be immobilized on surfaces via covalent coupling, either by "grafting to" [16][17][18][19] or "grafting from," 20 via the adsorption of PEG-containing block copolymers, 18,[21][22][23] graft copolymers, 24,25 and interpenetrating polymer networks 26,27 and via functionalization with ethylene glycol-terminated alkanethiols 7,[28][29][30][31] or silanes. 32,33 For the platforms dealing with PEG in a brushlike conformation, it was found that the most important parameter determining the protein resistance is the ethylene glycol monomer density on the surface n EG expressed as EG units/surface unit.…”