Use of Gelatin as Tannic Acid Carrier for Its Sustained Local Delivery

Background: Polyphenols are macromolecules that play a pivotal role in plant protection against external aggression from microorganisms or radiations. Their antimicrobial properties have raised interest in the medical community for several years now. Among them, tannic acid is one of the cheapest polyphenols extracted from plants. However, its broad use is impeded because it is unstable, with rapid hydrolysis leading to byproducts such as epigallocatechin with less activity. In this work, we developed a porous material to deliver locally tannic acid. Methods: The preparation of this matrix relied on the interaction between gelatin and tannic acid in an aqueous medium. Structure properties of the developed matrix were investigated through rheology measurement and by scanning electron microscopy (SEM). Tannic acid quantity and release over time were measured. Antimicrobial activity was tested in vitro on E. coli and S. aureus. Results: The presence of two tannic acid populations, one free to diffuse across the scaffold and the second stabilized by gelatin with a more structural activity, was demonstrated. We showed that the formulation is possible above a molar ratio of 1:15 (gelatin:tannic acid). Gelatin was used here as a carrier for the tannic acid. Tannic acid content could be modulated depending on its initial concentration during the preparation. Tannic acid was released from these matrices over a period of four days at a concentration that was above the minimum inhibitory concentration (MIC). Antimicrobial activity was confirmed on E. coli and S. aureus. The porous material could be conserved by lyophilization without loss of activity. Its handiness is good enough to consider its use as a wound dressing. Conclusions: We demonstrate herein an easy and cost-effective protocol to locally deliver tannic acid.