Mesoporous silica nanoparticles modified with N-rich polymer as a potentially environmentally-friendly delivery system for pesticides

The focus of the article is on the design of environmentally-friendly nanocarriers for improved controlled pesticide release, which have low environmental toxicity and nitrogen elemental composition as the most important components of fertilisers. In this study, a novel delivery system was developed for post-loading a biopesticide to mesoporous silica nanoparticles (MeSiNPs) functionalised with N-rich derived polymer. Initially, MeSiNPs were synthesised by the template-assisted method, which yielded MeSiNPs in the nm range, together with highly ordered mesoporous channels with a pore size of 2.9 nm. Subsequently, the water-soluble branched polyethyleneimine (bPEI) was derived systematically with epoxy organosilicate, and functionalised on MeSiNPs to create a source of N-nutrients. The carefully designed novel nano-carrier was analysed by several physico-chemical and structural analyses, which confirmed the successful attachment of the derived bPEI to MeSiNPs. Further, the novel nano-synthesised system was used as a delivery for the model biopesticide citridiol. The loading efficiency of citridiol in/on MeSiNPs@bPEI was 19%, while the loading capacity of citridiol was proven to be 5 mg biopesticide/1 mg MeSiNPs@bPEI. The MeSiNPs@bPEI with loaded citridiol was investigated for kinetic release. The system showed a fast initial release behaviour in the first 300 min, which was continued by slow release behaviour and started to reach equilibrium after 10 days. It has been shown that the MeSiNPs@bPEI showed an excellent potential for use in agrochemical applications, not only as a nanocarrier for controlled and slow pesticide release, but may also act as a soil improver by providing Si and N as key nutrient sources.