In vitro studies of PEG thin films with different molecular weights deposited by MAPLE

In this work, polyethylene glycol (PEG) films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE). The possibility to tailor the properties of the films by means of polymer molecular weight was explored. The films of PEG of average molecular weights 400 Da, 1450 Da, and 10000 Da (PEG₄₀₀, PEG₁₄₅₀, and PEG₁₀₀₀₀) were investigated in vitro, in media similar with those inside the body (phosphate buffer saline PBS with pH 7.4 and blood). The mass of the polymer did not change during this treatment, but the polymer molecular weight was found to strongly influence the films properties and their behavior in vitro. Thus, immersion in PBS induced swelling of the PEG films, which was more pronounced for PEG polymers of higher molecular weight. Prior to immersion in PBS, the PEG films of higher molecular weight were more hydrophilic, the water contact angles decreasing from ～66 grd for PEG₄₀₀ to ～41 grd for PEG₁₄₅₀ and to ～15 grd for PEG₁₀₀₀₀. The same trend was observed during immersion of the PEG films in PBS. Before immersion in PBS, the refractive index of the films increased from ～1.43 for PEG₄₀₀ to ～1.48 for PEG₁₄₅₀ and to ～1.68 for PEG₁₀₀₀₀. During immersion in PBS the refractive index decreased gradually, but remained higher for the PEG molecules of higher mass. Finally, blood compatibility tests showed that the PEG films of higher molecular weight were most compatible with blood.