Preparation and characterization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) microspheres for controlled release of buprofezin

Extensive application of pesticides has caused a lot of environmental pollution and health problems, prompting the development of highly efficient and lowly toxic pesticide formulations. Here, buprofezin (BPF)-loaded poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(HB-HH)) microspheres were prepared by O/W emulsion/solvent evaporation method. Under optimal conditions (P(HB-HH) 7.07% (w/v) and PVA 1.84% (w/v)), the spherical and monodispersed microspheres were obtained. The average particle size, pesticide loading (PL), and encapsulation efficiency (EE) of the optimized microspheres were 1.2 μm, 15.68%, and 78%, respectively. Release of 80% BPF from the microspheres in pH 5 (192 h) was faster than that in pH 7 (228 h) and 8 (204 h). Moreover, kinetic analysis indicated that BPF release behaved in a non-Fickian diffusion manner (0.43 < n < 0.85) and the release mechanism was the combined effects of pesticide diffusion and hydrolysis of polymer. The bioassay and toxicity results showed that encapsulation of BPF could exhibit high efficacy on the target organism and low toxicity to the non-target organism. Therefore, these results demonstrated that BPF-loaded P(HB-HH) microspheres with good stability were prepared successfully, and they could be further explored for constructing other highly efficient and lowly toxic pesticide formulations.