Achieving low-fouling surfaces with oppositely charged polysaccharides via LBL assembly.

UNLABELLED: The aim of this work is to understand and achieve low fouling surfaces by mixing two oppositely charged polysaccharides through layer-by-layer (LBL) assembly. Diethylaminoethyl-dextran hydrochloride and alginate were employed as a model system to build LBL films. A surface plasmon resonance (SPR) biosensor was used to measure quantitatively the adsorption behavior of charged macromolecules during LBL buildup and the protein adsorption behavior of each deposited bilayer in situ in real time accordingly. Results show that LBL films have lower protein adsorption as the films are constructed above the substrate surface. These LBL films eventually reach very low fouling when they are sufficiently far from the substrate surface, where the substrate surface effect is minimized and bilayers consisting of positively and negatively charged marcromolecules are uniformly mixed. Single proteins, undiluted human blood serum and plasma and cells were tested for adsorption to LBL films with similar trends. To verify the generality of these findings, alginates of low and high molecular weights and carboxymethylcellulose as a substitute to alginate were studied with similar trends observed. These results demonstrate that oppositely charged polymers, when uniformly mixed, are able to achieve low fouling properties. Findings from this work will provide a fundamental understanding of and design principles on how to build nonfouling LBL films. STATEMENT OF SIGNIFICANCE: We demonstrate that protein adsorption decreases with the increase of bilayer numbers. Results indicate that oppositely charged components tend to be uniformly mixed and distinct change layers in classical layer-by-layer (LBL) theories no longer exist as LBL films are sufficiently far from the substrate surface. Findings from this work provide a fundamental understanding of and design principles on how to build nonfouling LBL films.