Siloxane-tethered poly(2-ethyl-2-oxazoline) as surface modifying additives for anti-fouling silicones

While silicones are broadly utilized for medical devices, their hydrophobic nature renders them highly prone to biofouling, leading to reduced safety and efficacy. We have previously demonstrated that biofouling is reduced for silicones combined with amphiphilic surface modifying additives (SMAs) comprised of a poly(ethylene glycol) (PEG) segment and a siloxane tether (PEG-silane). However, there is a rising concern regarding the potential immunogenicity of PEG. Herein, SMAs were created wherein poly(2-ethyl-2-oxazoline) (PEtOx) was substituted for PEG. PEtOx-silane SMAs (H-Si-DMS _m -block-PEtOx₁₀; m = 13 and 30) were synthesized, and each incorporated into unfilled (i.e., silica-free) silicones: dimethyl silicone [MED-6019; 0% Ph], dimethyl diphenyl silicone [MED-6010; 5.8% Ph], and dimethyl diphenyl silicone [MED-6020; 8.5% Ph] at increasing concentrations (5 - 25 μmol g^-1). Analogous PEG-silane SMAs (H-Si-DMS _m -block-PEG₈; m = 13 and 30) were likewise used to modify the silicones. The chemical crosslinking and subsequent retention of SMAs in modified silicones was confirmed. The resulting properties imparted by a particular SMA were impacted by the phenyl content of the silicone. However, PEtOx-based SMAs generally produced a greater plasticizing effect than PEG-based SMAs. Fouling against fibrinogen, a fungus, and four bacteria was assessed for silicones modified with each SMA (25 μmol g^-1). In general, silicones modified with POx-based SMAs demonstrated greater anti-fouling behavior versus unmodified silicones. DMS₃₀-POx often achieved similar anti-fouling efficacy versus PEG-based SMAs. These results point to the potential of amphiphilic POx-based SMAs to produce anti-fouling silicones.