Doxycycline hyclate-loaded in situ forming gels composed from bleached shellac, Ethocel, and Eudragit RS for periodontal pocket delivery

Polymeric material plays an important role as a matrix former in the modulation of drug release of antimicrobial-loaded <i>in situ</i> forming gel (ISG) for efficient periodontitis treatment. This study was conducted to compare three polymers, namely bleached shellac (BS), Ethocel (EC) and Eudragit RS (ERS), as matrix formers of doxycycline hyclate (DH)-loaded solvent exchange-induced ISG. All prepared ISGs, except 25% EC ISG, exhibited the Newtonian flow behaviour. Transformation from solution into matrix-like was achieved rapidly within 5 min. Increasing the amount of these polymers extended the release of DH. DH-loaded EC and ERS ISG systems exhibited high antimicrobial activity, and all ISGs were effective in inhibiting the growth of <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Streptococcus mutans</i>, <i>Porphyromonas gingivalis</i> and <i>Candida albicans</i>. By comparison, the DH-loaded ERS ISG, through the solvent exchange mechanism, was found to be ease in injection with low viscosity and sustained the release with higher concentration, meanwhile, it also exhibited interesting <i>in vitro</i> degradability and antimicrobial activities. Therefore, the DH-loaded ERS ISG exhibited a potential use for localized periodontal drug delivery system for the treatment periodontitis.