Production, characterization and controlled release studies of biodegradable polymer microcapsules incorporating neem seed oil by spray drying

Azadirachtin is a biologically active constituent of neem seed oil, exhibiting medicinal and pesticidal properties. This work reports on the encapsulation of neem seed oil extract within three different polymeric shells: polyvinyl alcohol (PVA), gum arabic (GA) and whey protein isolate/maltodextrin (WPI/MD), using spray drying. The obtained, roughly spherical microcapsules had average sizes of 28.84 +/- 11.86 mu m, 32.43 +/- 13.06 mu m, and 52.88 +/- 17.33 mu m (obtained from PVA, GA, and WPI/MD, respectively). Fourier transform infrared spectroscopy confirmed the presence of the core and shell components, in addition to surface functional groups. Encapsulation efficiencies for neem seed oil proved higher in smaller microcapsules, although efficiency values of 60-92% were obtained in all cases. In vitro release of neem seed oil from the microcapsules followed the Ritger-Peppas model, as governed by Fickian diffusion. From these results, the association of botanical insecticides within biopolymer cores offer considerable potential for increasing agricultural production levels, and reducing impacts on the environment and human health.