RESUMEN
Controlled release formulations (CRFs) are promising in improving the efficiency of pesticide and minimizing the spreading of hazardous residues in environment. By coupling with the pesticide covalently, chitosan can be used as a carrier material for the vulnerable ingredient. For the first time, gibberellic acid (GA3), one of plant growth regulators, was attached to chitosan (CS) to form a GA3-CS conjugate via the formation of an amide bound using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide. The novel conjugate was structurally characterized by fourier transform infrared spectroscopy, ultraviolet spectrophotometer, and thermal gravimetric analysis. Effects of pH, temperature, and UV irradiation on the release of this conjugate were investigated. The results showed that the new conjugate had a remarkable modification degree for CS (more than 60%, w/w) and the optimal coupling conditions were deï¬ned as: the molar ratio of GA3:EDC/NHS:CS was 1:1.2:1.2, at pH 6.0 for 24 h. The release data showed the novel conjugate protected GA3 against photo- and thermal-degradation effectively and the concentration of GA3 in GA3-CS kept unchangeable about 60 d in different pH conditions. Compared with GA3 technical, the conjugate had better water solubility and stability and have potential applications. The present study also provides a novel preparation method of CRFs comprising a pesticide with long duration, sustained-release performance and good environmental compatibility. This method may be extended to other pesticides that possess a carboxyl group.
Asunto(s)
Quitosano , Preparaciones de Acción Retardada , Giberelinas , Reguladores del Crecimiento de las Plantas , Quitosano/química , Quitosano/farmacología , Preparaciones de Acción Retardada/química , Preparaciones de Acción Retardada/farmacocinética , Giberelinas/química , Giberelinas/farmacocinética , Concentración de Iones de Hidrógeno , Plaguicidas , Reguladores del Crecimiento de las Plantas/química , Reguladores del Crecimiento de las Plantas/farmacología , Solubilidad , Factores de TiempoRESUMEN
Controlled release formulation (CRF) of pesticides is highly desirable for attaining the most effective utilization of the pesticide as well as reducing environmental pollution. Due to the selective permeation and protection properties of the semi-permeable membrane, pesticide microcapsules have been widely used. In this work, we developed a novel two-step method for synthesizing highly stable silica-glutaraldehyde-chitosan composite avermectin microcapsules. The silica shell was formed through the hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) at the oil droplet-water interface by using TEOS as the silica precursor and hexadecyl trimethyl ammonium chloride as a surfactant. Then the silica shell was modified with 3-aminopropyltriethoxysilane. Chitosan nanospheres were prepared by adjusting the pH value of the solution and then cross-linking with modified silica at the surface of the silica shell in the presence of glutaraldehyde to form double-shelled avermectin microcapsules. The results showed that the resulting microcapsules had a remarkable loading ability for avermectin (about 40% w/w) and can protect avermectin against photo- and thermal degradation effectively. Compared to single-shelled microcapsules, the double-shelled ones had better controlled release properties under all conditions. The present study provides a novel CRF comprising a pesticide which is light-sensitive or high temperature-sensitive, and a method for preparing the improved pesticide formulation so that the pesticide release rate and release period could be adjusted.
RESUMEN
Chemical pesticides have been widely used to increase the yield and quality of agricultural products as they are efficient, effective, and easy to apply. However, the rapid degradation and low utilization ratio of conventional pesticides has led to environmental pollution and resource waste. Nano-sized controlled-release formulations (CRFs) can provide better penetration through the plant cuticle and deliver the active ingredients efficiently to the targeted tissue. In this paper we reported novel conjugated nanospheres derived from 1-naphthylacetic acid (NNA), 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate and their application as a controlled-release plant growth regulator. The NNA and APTES conjugate was prepared through a covalent cross-linking reaction and subsequent hydrolyzation and polycondensation to synthesize NNA-silica nanospheres. The release data indicated that the release of NNA was by non-Fickian transport and increased as particle size decreased. It was also found that the acidity-alkalinity was enhanced and as the temperature increased, the release of the active ingredient was faster. The nanoconjugate displayed a better efficacy in promoting root formation than NNA technical. The present study provides a novel synthesis route for CRFs comprising a pesticide, with long-duration sustained-release performance and good environmental compatibility. This method may be extended to other pesticides that possess a carboxyl group.