Effects of porcine small intestinal submucosa on elution characteristics of gentamicin-impregnated plaster of Paris

Objective - To evaluate effects of small intestinal submucosa (SIS) on elution properties of plaster of Paris (POP). Sample Population - 27 POP cylinders, 27 POP spheres, and 9 polymethylmethacrylate (PMMA) spheres. Procedures - Pellets were loaded with gentamicin (50 mg/g) and divided into 7 groups of 9 beads each: PMMA spheres; POP cylinders coated with 0, 4, or 8 layers of SIS; and POP spheres coated with 0, 4, or 8 layers of SIS. Gentamicin concentration was measured 6, 12, 18, 24, 32, 40, and 48 hours and 3, 4, 5, 7,14, 21, 28, 35, and 42 days after wrapping. Porosity was evaluated via scanning electron microscopy. Curvature factor of elution curves, total amount of drug released (TDR), time required to reach 50% of total release (TDR_t50), and number of days with concentrations ≥ 1 μg/mL were compared among groups. Results - SIS decreased the curvature factor and increased the TDR_t50 and TDR of POP spheres and cylinders. Curvature factor of the PMMA-release curve remained lower than that for any POP group, but all POP groups wrapped in SIS released more gentamicin than PMMA spheres. Gentamicin concentrations remained ≥ 1 μg/mL in SIS-wrapped POP and PMMA groups throughout the study. Wrapping POP in SIS minimized the increase in porosity of pellets. Conclusions and Clinical Relevance - Wrapping POP with SIS slows the release and increases the amount of gentamicin leaching from spheres and cylinders. All groups wrapped in SIS maintained antimicrobial concentrations greater than the minimum inhibitory concentration of most pathogens.