Fouling is the undesirable accumulation of a material on a variety of objects and has now become a widespread global problem with limiting the engineering and medical applications. Polymers have been used to develop the fouling resistance mostly by controlling the surface functionalities (such as interaction and surface energy) and architectures (such as surface grafting), allowing us to design the suitable interfacial properties. In this presentation, we report protein-repellent properties of ultrathin polymer films that are considered to be of structural origin and generalizable across homopolymer systems. We recently found the unique yet universal structure and dynamics of polymer chains adsorbed on solid planar substrates via physisorption. This result highlights the vital roles of nanometer-thick adsorbed layer (“polymer nanolayer”) in protein anti-fouling properties. Ultrathin polymer films composed of polystyrene, poly(2-vinyl pyridine), poly(methyl methacrylate), and polybutadiene with different thicknesses (h) ranging from 2 to ~100 nm were prepared on silicon substrates, and fluorescein-labeled bovine serum albumin (BSA) and human plasma fibrinogen are chosen as model proteins, which have significant differences in their size, shape, and internal stability. The fluorescence intensity I(h) measured by a photon-counting spectrofluorometer generated a master curve over the film thickness regardless of the polymer and protein choice, revealing the two different protein adsorption regimes with the following thicknesses: (i) below the critical thickness (hc ≈ 20 nm), I(h) is minimal and exhibits a very weak thickness dependence; (ii) at h &gt; hc, I(h) exhibits very strong thickness dependence (I(h)∼ h2). The protein resistance is found regardless of a complex interplay of interactions among a polymer and substrate. It is also discovered that the antifouling property of this nanolayer is generalizable to the various homopolymer systems regardless of their hydrophilicity/hydrophobicity. Molecular dynamics simulations identified a correlation between protein adsorption and highly packed conformations of polymer chains. In addition, the simulation explains the absorption behavior of polymer chains in dense layer, which will be discussed in this presentation. These experimental and computational findings detail a new mechanism behind the structure-driven protein-repellent properties of polymer structures under nanoconfinement over surface chemistry.

Generalized protein repellent property of polymer chain nano-architecture

ACS Spring 2022

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