Preparation of pH-stabilized microcapsules for controlled release of DEET via novel CS deposition and complex coacervation

In order to slow down the volatilization rate of N, N-Diethyl-m-toluidine (DEET) and enhance its safe application, an improved complex coacervation method was developed to encapsulated it to prepare microcapsules with the function of mosquito repellent. Tannic acid as a cross-linking agent for gelatin and Arabic gum enhanced the structural stability of the capsule through hydrogen bonding. Chitosan was selected to further deposited on the surface of G/AG MC for the improvement of pH stability and formed CS-G/AG MC. Scanning electron microscopy and optical microscope confirmed the chitosan was successful deposited on the G/AG MC, which ameliorated the agglomeration of microcapsules and promoted their monodispersity. Fourier transform infrared spectroscopy confirmed that electrostatic attraction accounted predominantly for the forces between the shell materials. The deposition of chitosan imparted controlled release to the microcapsules, resulting in a high retention efficacy of DEET in the pH range of 2–10. The CS-G/AG MC showed good storage stability and biocompatibility, and the static leakage of DEET within 40 days was negligible. The microcapsules prepared by this method showed green ecological properties, derived from the natural origin and biocompatibility of the shell material. And the tight structure of the microcapsule shell effectively barriered the volatile of DEET, while greatly extending its release time. This study can effectively protect the biological activity of core materials of microcapsules, and has long-lasting release performance, which has potential economic benefits in personal care products market directly contacted by humans.