k-Carrageenan-Bacillus thuringiensis israelensis hydrogels: A promising material to combat larvae of the Aedes aegypti mosquito

Bacillus thuringiensis israelensis (Bti) is a biopesticide to combat Aedes aegypti mosquito, vector of dengue, zyka and chikungunya. Its rapid degradation prevents its widespread use. This work aimed to prepare a hydrogel based on k-carrageenan and Bti, in order to avoid its degradation and enhance its action against Aedes aegypti larvae. Hydrogel physicochemical properties were evaluated by swelling degree, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. Bioassays were performed to assess larvicidal activity by releasing Bti incorporated into the hydrogel. The hydrogels were kept immersed in water for seven months and showed good resistance, without changing its shape, proving the stability of hydrogel. The microscopy images confirmed the presence of Cry protein into hydrogels, proving the incorporation of Bti. The bioassays results showed that the material produced was effective in gradual release of Bti, for the 11 weeks analyzed, providing a larval mortality rate of 100%.