Analysis of vancomycin loading in OPF/SMA hydrogels.

(A) OPF/SMA 40% hydrogels were incubated with vancomycin at 400 μg/mL for 1 hour, 4 hours, 8 hours, 24 hours, or 72 hours. The concentrations of vancomycin in solution were then measured with HPLC coupled to UV-Vis detection at 280 nm and drug loading was determined by subtracting the initial concentration of drug from the final concentration after completion of vancomycin loading. (B) Hydrogels were incubated for 24 hours, samples were collected, and the concentration of vancomycin in solution was determined as described. Amount of drug loaded was calculated and loading efficiency was determined by dividing the mass of loaded drug by the dried hydrogel mass, such that loading efficiency is represented as μg vancomycin per mg hydrogel. (C) Maximal drug loading was determined by incubating OPF/SMA 30% hydrogel samples in increasingly concentrated solutions of vancomycin in double distilled water for 24 hours. Loading efficiency (Effl) was determined by measurement of the final drug concentration in the distilled water (Cf) after completion of the loading cycle, followed by comparison to concentration of initial solution (Ci) via the equation (Effl) = {[(Ci)—(Cf)] / (Ci)}*100%. (D) Diagram representing drug loading experiment. In all experiments, concentrations of vancomycin remaining were determined from a standard curve of vancomycin solution that was incubated under identical conditions to the sample of interest. Error bars represent +/- one standard deviation, N = 3 in all groups. Statistical representation: (*) indicates p<0.05.