Controlled release of DEET and Picaridin mosquito repellents from microcapsules prepared by complex coacervation using gum Arabic and chitosan

Abstract

Microcapsules (MCs) of mosquito repellents (DEET and Picaridin) were prepared by complex coacervation using gum Arabic and chitosan as wall materials. The resulting diameters of MCs were 2.35±0.76 µm for DEET and 4.26±1.77 µm for Picaridin, analyzed by optical microscopy. Spherical mononuclear-type MCs were also observed. The mean particle size of dried DEET-MC and Picaridin-MC was 182 µm and 140 µm, respectively, indicating agglomeration of MCs. Fourier transform infrared spectroscopy confirmed the encapsulation of repellents by the appearance of carbonyl (C=O) absorption bands in the associated spectra. Moreover, the microencapsulation efficiency was 60% and 73% for DEET and Picaridin, respectively, determined by Soxhlet extraction. From Thermogravimetric analysis, delay of DEET and Picaridin losses revealed encapsulation of DEET and Picaridin inside the MCs. In addition, the higher release rate of Picaridin compared to DEET under isothermal conditions was correlated with longer protective time relative to the free repellents, as demonstrated by the “arm in cage” test. The study concludes that microencapsulated DEET and Picaridin show high promise of functional textiles for mosquito repellency.