Characterization Of Gentamicin Impregnated Collagen Scaffolds: In Vitro Elution, Cytocompatibility, And In Vivo Tissue Interface

Infection is a common complication in orthopedic surgery, and it is often challenging to prevent or eliminate bacterial infection. Treatment is complicated by biofilm formation, insufficient antibiotic penetration, and systemic side effects associated with prolonged antibiotic administration. The desire to eliminate bacterial infection while minimizing side effects has inspired the creation of local drug delivery systems for local antibiotic delivery. Challenges accompanying the use of local drug delivery devices include: foreign body reaction, bacterial colonization on the device, and the risk of prolonged subtherapeutic antibiotic release that could promote antimicrobial resistance (AMR). This study aimed to evaluate the antibiotic elution profile and cytocompatibility, in vitro, and the effect of local delivery of high dose gentamicin on the tissue-scaffold interface, in vivo, with a commercially available collagen matrix (Fibro Gide, Geistlich) selected as the drug delivery vehicle. Our hypothesis was that the gentamicin impregnated scaffolds would be cytocompatible, would elute gentamicin with an initial burst release, and that the gentamicin impregnated scaffolds would negatively impact the tissue-scaffold interface in vivo. Cytocompatibility testing was performed using 3T3-E1 murine pre-osteoblast cells, cultured in standard media and media spiked with increasing doses of gentamicin (50mg/mL and 100mg/mL). Results of cell proliferation assays, calcein AM staining, and histology of the in vitro scaffolds indicated that the gentamicin impregnated scaffolds were cytocompatible. In vitro gentamicin elution was characterized by an initial burst release of antibiotic followed by gradual, sustained low-concentration release. In vivo assessment of tissue-scaffold interfaces was performed using a rat mandible defect model. Surgical defects were created unilaterally in the mandible of 12 rats and scaffolds were placed within the defect (n=6, 40mg/kg gentamicin; n=6, native scaffold). Rectal culture swabs were collected throughout the study to evaluate for the development of AMR. Histopathology of the tissue-scaffold interface was performed on mandible defects harvested 28 days after implantation. AMR to gentamicin was not detected at any timepoint. Histopathology results showed no significant difference in tissue integration between the native and gentamicin impregnated groups. Based on the results of this study, the collagen matrix was cytocompatible, capable of eluting gentamicin for a period of 14 days, and local delivery of a high dose of gentamicin did not significantly alter the tissue-scaffold interface. This collagen matrix represents a promising device for utilization in local drug delivery. This model and drug delivery platform may be used for future studies to evaluate various drugs and their effects on infection, AMR, and tissue-scaffold integration.