Effect of Freezing on the Release Rate of Gentamicin Palmitate and Gentamicin Sulfate from Bone Tissue

ABSTRACT: In this study we evaluated gentamicin palmitate salt and gentamicin sulfate salt mixed with bone chips after storage at
80°C. Different concentration rates of gentamicin sulfate and gentamicin palmitate were mixed with human bone chips and stored for
1–6 months at 80°C. Nonstored samples were used as control. The release of the antibiotics from the bone was carried out in
phosphate-buffered saline. Antibiotic concentrations in the elutions were determined with microbiological agar diffusion assay using
Bacillus subtilis. Susceptibility tests were carried out using Staphylococci strains. The rate of gentamicin base (GB) released from bone was similar for all gentamicin salts and all storage conditions. The elutions released were efficient on reducing S. aureus and S. epidermidis CFU during all storage time. In resume, the capacity of bone grafts to act as gentamicin carriers has been confirmed in this study. GSþGP showed equivalent efficacy against S. aureus and S. epidermidis compared with GS pure. The lower delivery rate of GSþGP, related to its affinity with fat tissue can be an advantage for longer release times, increasing the local protection against infections. Storage at 80°C does not interfere on the gentamicin salts activity used. 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res