Doxycycline Delivery From Collagen Matrices Crosslinked With Tannic Acid

Collagen-doxycycline matrices crosslinked with a natural polyphenol - tannic acid for the treatment of infected wounds were obtained by the freeze-drying of the corresponding gels. FT-IR spectra show that the triple helical structure of collagen is preserved in all the matrices, doxycycline produce collagen crosslinking and the degree of crosslinking increases with tannic acid concentration. Digestion of matrices using collagenase confirms the crosslinking effect of doxycycline and tannic acid and the increasing of the crosslinking degree with the amount of acid. The release of doxycycline from the matrices crosslinked with tannic acid is slower than that from the uncrossliked one and decreases with increasing of acid concentration, according to FT-IR and digestion results, and follows the power law model, with a release exponent of about 0.4, which indicates an anomalous transport. The matrices containing doxycycline, tannic acid and their combination do not develop gram-positive (Staphylococcus aureus) or gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, fungi or leavens.