DRUG DELIVERY SYSTEMS BASED ON COLLAGEN-TANNIC ACID MATRICES

Tannic acid cross-links collagen both in acid (pH 3.8) and weakly basic (pH 7.4) medium. The cross-linking does not affect the integrity of triple helical structure of collagen as spectral characteristics, enzymatic degradation and release data of tannic acid from collagen matrices demonstrate. Intermolecular bridging produces changes in the amide III IR band of the collagen-tannic acid matrices. The higher the amount of tannic acid in the matrix, the slower the enzymatic degradation process. The release of tannic acid from the collagen-tannic acid matrices is slower for samples obtained at pH 3.8 than for those resulted at pH 7.4 due to the higher amount of intermolecular bonds formed. The kinetic of tannic acid release from each collagen-tannic acid matrix follows the Peppas mechanism, with a value of the exponent of about 0.6.