Silk Fiber Implant Coatings for the Localized Release of Antibiotics

Objectives: The purpose of the present study was to fabricate silk fiber biomaterial implant coatings for titanium surfaces with sustained release of tetracycline.
Methods: An aqueous solvent-processing method was used to generate the silk biomaterials from B. mori for titanium implant coatings. Tetracycline-loaded silk was pipetted onto titanium implant studs and an electric current was used to convert the protein to an adhesive gel coating (electrogelation). Tetracycline-loaded silk was also placed on filter paper discs as controls. To examine the rate of tetracycline release from the silk coatings, the coated titanium studs were incubated with the bacterium, S. mutans, on agar plates and removed after 30 minutes, 60 minutes, or 3 hours (study 1) or up to 3 days (study 2).
Results: Release kinetics studies showed that titanium studs released tetracycline starting within 30 minutes. There were similar zones of inhibition with the titanium studs when compared to the positive paper controls (Table 1). Once it was determined that tetracycline was released from the studs, the duration of release was investigated. Table 2 shows that on day 1 there was no difference between the studs loaded with 3 or 6 mg/ml tetracycline and corresponding controls. After two days, the difference between the inhibition of the bacteria by the release of antibiotic from the stud vs. paper was more apparent (Table 2). By the third day there was little inhibition.
Conclusions: Results showed that tetracycline could be loaded in electrogels and released in as fast as 30 minutes and sustained for up to 24 hours. An important implication of this work is that tetracycline-releasing silk implant coatings may be further studied to potentially reduce dental implant-related periodontal infections during the first 24 hours after the implant procedure, which is the time frame when most infections arise in a clinical setting.