Introduction: Various antibiotic coatings have been proposed to prevent bacteria colonization and infection of orthopaedic implants. While most of the available technologies seem to provide an effective implant protection from infection, unknown long-term effects of antibiotic coatings raise some concerns for extensive application. Aim of the present study was to develop and test a new fast-resorbable antibacterial carrier to be used as a temporary coating to prevent early bacteria colonization of metallic implants.
Methods: The patented tested hydrogel is a co-polimer comprising hyaluronic acid (HA) and a biocompatible polyester (poly-lactic acid) with or without polyethylene glycol chains to further modulate hydrophilicity and anti-fouling characteristics of the compound. The HA derivative is then added to water and mixed, just before its use, with the chosen antibacterial agent. For the purpose of this study, different HA-PLA derivatives have been tested, with two vancomycin and tobramycin concentrations and manually spread to uniformly cover the surface of a titanium specimen. To evaluate the release of vancomycin or tobramycin, high performance chromatographic analysis (HPLC) was carried out.
Results: Antibacterial hydrogels provided vancomycin release ranging from 47 % to 80 % in two hours to 100 % (complete release) in 24 to 72 hours, with antibiotic concentrations up to 400 times the minimum inhibiting concentration. The combined release of the two antibiotics (1 % w/v) showed 26.8 % release of vancomycin and 35.8 % of tobramycin at 2 hours and complete release at 72 hours. Doubling antibiotic concentration (2 % w/v), yielded 56.6 % and 76.6 % antibiotic release, respectively for vancomycin and tobramycin at 2 hours and complete release at 48 hours.
Discussion and Conclusion: HA chemical derivatization with polyesters leads to the formation of copolymers which can be used to produce antibacterial hydrogels with promising applications in the orthopedic field. These antibacterial hydrogels are in fact easily prepared and spread over a surface, showing the ability of releasing high concentrations of antibiotics for a desired, limited, period of time. Adding antibiotics to the hydrogel just before its use, allows customized antibiotic choice and dosing, avoiding shelf-life problems.
