Enhancing UV radiation protection of Bacillus thuringiensis formulations using sulfur quantum dots: synthesis and efficacy evaluation

Abstract

Bacillus thuringiensis (Bt) is a widely used microbial insecticide, but its effectiveness is limited due to the degradation of Bt spores and crystals under UV radiation from sunlight. The objective of this study was to develop a novel Bt formulation with improved UV protection by utilizing sulfur quantum dots (SQDs) as stabilizing agents in a Pickering emulsion. The SQDs were comprehensively characterized using FTIR, XRD, TEM, HRTEM, UV, and fluorescence analyses, which confirmed the formation of well-dispersed, spherical SQDs. The microcapsule formulation with SQDs demonstrated superior UV stability, as it maintained 57.77% spore viability after 96 h of UV exposure, in comparison to 33.74% and 31.25% for the SQDs formulation (non-microcapsules) and unprotected Bt formulations (free spore, as a control), respectively. Furthermore, the microcapsule formulation exhibited higher insecticidal activity, resulting in a larval mortality of 71.22%, as opposed to 42.34% and 38.42% for the other formulations. These findings emphasize the effectiveness of microcapsule formulation with SQDs in safeguarding Bt spores and crystals against UV radiation, thereby enhancing their practical application in pest control. This approach presents a promising strategy for the development of biopesticides that are more resilient and have a longer shelf life.