In situ forming gel comprising bleached shellac loaded with antimicrobial drugs for periodontitis treatment

Abstract

Bleached shellac, a mixture of polyesters made up of sesquiterpenoid acids esterified with hydroxy aliphatic acids, is a well-known water-insoluble polymer. Owing to its high solubility in N-methyl pyrrolidone (NMP) it is interesting to apply as a polymer matrix for solvent-exchanged in situ forming gel. The aim of this research was to study the gel properties, drug release and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyromonas gingivalis of the in situ forming gels prepared from bleached shellac dissolving in NMP to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The solvent exchange between NMP and external aqueous simulated gingival crevicular fluid stimulated the dissolved bleached shellac transforming into the opaque rigid gel. Increasing the amount of bleached shellac increased the viscosity of the system while still exhibiting Newtonian flow and increased the work of syringeability whereas prolonging the drug release. The developed systems comprising 5% w/w antimicrobial agent showed antimicrobial activities against all test bacteria. Thus the solvent exchange-induced in situ forming gels comprising of bleached shellac-antimicrobial drugs exhibited potential use for periodontitis treatment.