Unusual Protein Adsorption Phenomena on Ultrathin Homopolymer Films

We recently designed a new anti-fouling polymer nanolayer of a few nanometer-thick composed of non-charged homopolymer chains physically adsorbed onto a solid [1]. Interestingly, the anti-fouling property of this polymer nanolayer emerged regardless of the degree of hydrophilicity of the polymers against a model protein (bovine serum albumin (BSA). However, it was observed that 50 nm-thick spin-cast thin films composed of the same homopolymers showed BSA adsorption. To shed light on the anti-fouling/fouling switching between the nanolayer and thin film, BSA adsorption was studied on a series of ultrathin films of different thicknesses (2-200 nm in thickness) using polystyrene, poly(2-vinyl pyridine), polybutadiene, poly(methyl methacrylate), and polypropylene. Additionally, we examined the adsorption behavior of another protein, Fibrinogen, to see generality/differences in the anti-fouling/fouling switching. To quantify this protein adsorption, photon counting spectrofluorometry along with the fluorescence-labeled proteins was utilized. Therefore, we will discuss the universal anti-fouling/fouling switching as a function of film thickness regardless of the polymer and protein choice.
[1] Endoh et al., ACS Macro Lett., 2019, 8, 1153.