Molecular docking-assisted insights into methylene blue ecotoxicity and its detoxification by a biosorbent from Acer negundo.

In the present study, new insights into methylene blue (MB) toxicity were obtained using in vitro model systems and a molecular docking approach. A sustainable biosorbent from A. negundo (AN) biomass was prepared and its detoxification potential was investigated. MB at concentrations of up to 10 ppm caused significant phytotoxic effects on the physiological parameters of Brassica oleracea var. acephala and anatomical parameters of A. cepa L. Germination rate of B. oleracea var. acephala seeds decreased to 76% with increasing MB concentrations. Moreover, significant decreases were observed in fresh weight (760.17 ± 0.76 mg), dry weight (43.09 ± 0.1 mg), root (7.46 ± 0.04 cm), and shoot lengths (13.92 ± 0.09 cm). Significant alterations were observed in the cytogenetic parameters and oxidant-antioxidant dynamics, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂). Molecular interactions contributing to the observed phytotoxicity were revealed by molecular docking analysis of MB with the target receptors associated with in vitro parameters (alpha-amylase (AMY1), beta-amylase (BMY1), serine/threonine-protein kinase (CTR1), B-DNA dodecamer, catalase, peroxidase, and superoxide dismutase). AN biosorbent treatment significantly detoxified MB solutions, and improvements in the values of the tested physiological, anatomical, biochemical, and cytogenetic parameters were observed. The parameters affecting biosorption were pH_pzc, pH, contact time, biosorbent dose, initial MB dye concentration, stirring speed, and temperature. The R² values of the pseudo-second-order kinetic (R²=0.999) and Freundlich isotherm (R² = 0.992) models were the best fitted kinetic and isotherm studies for the biosorption process. Because the ΔH˚ (-36.236 kJ/mol) and ΔG˚ values (-6.63, -5.65, -4.67 and -3.7 kJ/mol) calculated in thermodynamic studies were found to be negative, the biosorption process was determined to be exothermic and spontaneous. Thus, AN biosorbent was determined to be a low-cost, sustainable, and eco-friendly material for the removal and detoxification of synthetic dyes from aqueous solutions.