Tetracycline release from tripolyphosphate-chitosan cross-linked sponge: a preliminary in vitro study

The aim of this study was to design a tripolyphosphate-chitosan cross-linked tetracycline-containing (TPP-TC) sponge that slowly releases tetracycline, for future periodontal applications. Chitosan sponge was made by freezing and drying 2.5% chitosan solution. Tripolyphosphate-chitosan cross-linked (TPP) sponge was made by immersing the chitosan sponge in tripolyphosphate solution and air drying it. Tetracycline-containing chitosan (TC) sponge was prepared by freezing and drying a mixture of chitosan and tetracycline. TPP-TC sponge was made by immersing the TC sponge in tripolyphosphate solution. The weight, thickness and diameter of the four chitosan sponges were recorded. Their surface microstructures were inspected using scanning electron microscopy. The amount of tetracycline released from the sponges was analyzed by spectrophotometry. Antimicrobial activities of the residual sponges were tested against Staphylococcus aureus and Escherichia coli. The topography of the scaffolds was intact after the addition of tetracycline. However, increased surface irregularities were noted. In sponges with tripolyphosphate, intensified surface folding was observed. The weight of the sponges increased after tripolyphosphate and tetracycline were added, but their thicknesses and diameters decreased after cross-linking. Tetracycline was detected in the solution containing TPP-TC sponges until day 11. On day 7, the tetracycline released from TC sponges was less than that released from TPP-TC sponges. Bacterial growth was inhibited by sponges containing tetracycline. The inhibitory effect of the TPP-TC sponges was detectable until day 11. Our data showed that TPP-TC sponge was suitable as a slow-release device for tetracycline and that it maintained antimicrobial effects against the bacteria tested for up to 11 d.