Synthesis of pH-responsive carboxymethyl chitosan for encapsulating tetracycline-HCl: Morphology, drug release behavior and antibacterial activity of microcapsules

In this work, tetracycline hydrochloride (TCH) as an antibiotic drug is encapsulated in carboxymethyl chitosan (CMCS) microcapsules (MCs). CMCS was synthesized by reacting chitosan with monochloroacetic acid to improve its pH sensitivity. The MCs were prepared by the emulsion crosslinking method and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), field emission-SEM (FESEM) and transmission electron microscopy (TEM). The in vitro drug release behavior of TCH-loaded MCs was investigated in buffer media with different pHs (4, 7 and 9) at 37 °C. The drug release in alkaline medium was higher as compared to acidic and neutral media that is desirable for infection treatment in which pH is relatively high due to bacterial activities. The kinetics of drug release was verified with conventional models and it was found that the Korsmeyer–Peppas model could predict the reduction of drug release at longer times. The physical stability of the MCs/TCH in different pH conditions was investigated with SEM and FTIR. The MCs/TCH showed appropriate antibacterial effects against E. coli and S. aureus, showing these microcapsules as promising candidates for drug delivery systems specially in wound dressing application.