Analysis of tobramycin release from beta tricalcium phosphate drug delivery system

The purpose of this pilot study was to determine the in-vitro release properties of tobramycin by tricalcium phosphate (TCP) delivery capsules. In addition, two different forms of TCP capsules, matrix and reservoir, were characterized. Three types of TCP ceramic capsules were constructed: six sham matrix capsules (Group A), six tobramycin loaded matrix capsules (Group B), and four hollow tobramycin loaded reservoir capsules (Group C). The capsules were submerged in PBS and 1 mL of elutant was collected, centrifuged, and analyzed via spectrometry for 14 days. In addition, elutant from selected capsules was bleached onto bacterial discs and placed on confluent Staphylococcus aureus agar plates to evaluate zones of inhibition. Their was a statistically significant difference in the concentration of tobramycin released between Group A versus Group B and Group C capsules and a statistically significant difference in the concentration of tobramycin released between Group B and Group C capsules over a 14 day period. Bacterial discs containing Group A elutant did not have a visible zone of inhibition, while both Groups B and C elutant discs had an appreciable zone of inhibition for the duration of the study. Group A sham capsules eluted no antibiotics implying that TCP by itself lacks antibacterial properties. Group B matrix and Group C reservoir capsules eluted sustained tobramycin concentrations that were bactericidal for the duration of the study. The data from this study demonstrates that the sustained release property of tobramycin loaded TCP matrix and reservoir capsules make them a suitable mode for local antibiotic delivery.