Fabrication of chitosan-alginate nanospheres for controlled release of cartap hydrochloride.

Insecticide cartap hydrochloride (C) was fabricated as nanospheres by a two-step method of ionic gelification and polyelectrolyte complexation of alginate (ALG) and chitosan (CS) to undermine its adverse effects on environment. Nanospheres were characterized by field emission scanning electron microscope, Fourier transform infrared spectra and x-ray diffraction. The size of cartap hydrochloride entrapped chitosan alginate nanospheres (C-CS-ALG nps) was in range of 107.58-173.07 nm. Cartap hydrochloride nanospheres showed encapsulation efficiency of 76.19% and were stable for 30 d at ambient temperature. Release of cartap from nanospheres fitted best with first order linear kinetics followed by Hixson and Higuchi model suggesting super case II transport release. With the application of such control release nanoformulations, it is possible to reduce the frequency of field application of insecticide due to its slow release to the target organism, which is economical as well as environmentally safe.

Cartap hydrochloride induced stress response in Anabaena variabilis ARM 441.

Cartap hydrochloride is a moderately hazardous nereistoxin analogue insecticide that is predominantly applied in paddy fields of India, at a recommended dose of 10 µg ml-1 to kill chewing and sucking insect pests of rice crop. Toxicity of cartap hydrochloride was studied on non-target free-living nitrogen fixing cyanobacterium Anabaena variabilis ARM 441 commonly used as algal biofertilizer in rice cultivation. Anabaena sp. could tolerate commercial grade insecticide up to 30 µg ml-1. However, at the recommended dose of 10 µg ml-1, it caused reduction in algal growth, total nitrogen and heterocyst frequency by 47.28, 24.29 and 17.72% respectively, as well as photosynthetic pigments under pure culture conditions. Scanning electron micrographs revealed cell rupture and breakage in filaments due to cartap exposure with the formation of akinetes. Cartap hydrochloride induced stress, since level of superoxide dismutase, peroxidase and catalase were increased by 108.57, 187.5 and 117% respectively. Generation of superoxide radicals and hydrogen peroxide were also increased by 152.48 and 34% respectively. Lipid peroxidation was increased by 31.03%, whereas there was decline in ascorbate content by 48.45%, however the glutathione content was increased by 128.57%. Increase in osmolytes such as proline from 8.6 to 32.8% and sucrose from 61.22 to 90.13% indicates their possible role in overcoming cartap induced oxidative stress and can be helpful in assessing its detrimental effect on Anabaena variabilis ARM 441, since cyanobacterial biofertilizers are purposely used in paddy fields as nitrogen contributors.