Silk Fiber Films for Controlled Release of Tetracycline and Doxycycline

Objectives: To assess the potential use of silk-based films for the controlled release of tetracycline and doxycycline for localized and continuous delivery of antibiotics during periodontal and oral surgeries.
Methods: Tetracycline and doxycycline were mixed, at various concentrations, with silk solution. Antibiotic loaded silk films were incubated with Streptococcus mutans (S. mutans) cultures to assess the release of the antibiotics. Chlorhexidine was used as a positive control and plain silk films without antibiotic as a negative control. Inhibition of bacterial growth was measured spectrophotometrically after each consecutive 24-hour incubation period. The number of colony forming units (CFUs) was determined to validate the growth inhibition.
Results: Tetracycline and doxycycline-loaded silk films inhibited S. mutans growth in a concentration and time-dependent manner. Tetracycline with the concentrations of 0.375, 0.75 and 1.5 mg/mL inhibited S. mutans growth up to three, four and five days, respectively (n=4). Doxycycline with the concentrations of 0.375, 0.75 and 1.5 mg/mL inhibited S. mutans growth up to six, ten and eleven days, respectively (n=4). The colony forming units for the 1.5 mg/mL doxycycline and tetracycline exposed S. mutans cultures were 1.2x10⁶ and 1.8x10⁶ CFUs/mL, respectively, which are less compared to the uninhibited control cultures which contained 3.5x10⁹ CFUs/mL.
Conclusions: We concluded that tetracycline and doxycycline can be successfully loaded into silk films and can significantly inhibit bacterial growth up to five days for tetracycline and eleven days for doxycycline. Our data support the use of antibiotic loaded silk films for localized and continuous delivery of antibiotics during periodontal and oral surgeries, thus minimizing risks associated with oral delivery of antibiotics.