Facile synthesis and physicochemical characterization of κ-Carrageenan-silver-bentonite based nanocatalytic platform for efficient degradation of anionic azo dyes.

Water pollution due to textile industry effluents is a global concern that warrants versatile research solutions for degrading them, and for a sustainable environment. In the present work, by using the imperative role of nanotechnology, a facile one-pot synthesis has been devised to generate κ-carrageenan capped silver nanocatalyst (CSNC), and was immobilized on 2D bentonite (BT) sheets to generate nanocatalytic platform (BTCSNC) for the degradation of anionic azo dyes. The nanocomposite(s) were physicochemically characterized using UV-Vis, DLS, TEM, FESEM, PXRD, ATR-FTIR, TGA, BET and XPS etc., to obtain insights into the nanocomposite composition, structure, stability, morphology and mechanism of interaction. The obtained CNSC are monodispersed, spherical with a size of 4 ± 2 nm, and were stabilized by the functional groups (-OH, COO‾, and SO3‾) of κ-Crg. The broadening of peak corresponding to basal plane (001) of BT montmorillonite in PXRD spectra established its exfoliation upon addition of CSNC. XPS and ATR-FTIR data evidenced the absence of covalent interactions between CSNC and BT. The catalytic efficiency of CSNC and BTCSNC composites were compared for the degradation of methyl orange (MO) and congo red (CR). The reaction followed a pseudo first order kinetics, and immobilization of CSNC on BT resulted in a 3-4 fold enhancement in degradation rates. The rates achieved for the degradation kinetics are: MO degradation within 14 s (Ka 9.86 ± 2.00 min-1), and CR degradation within 120 s (Ka of 1.24 ± 0.13 min-1). Further, a degradation mechanism has been proposed by analyzing the products identified through LC-MS. The reusability studies of the BTCSNC evidenced the complete activity of the nanocatalytic platform for six cycles, and gravitational separation method for catalyst recycling. In a nutshell, the current study provided an environmentally friendly, sizable, and sustainable nano catalytic platform" for the remediation of industrial wastewater contaminated with hazardous azo dyes".

Dissecting the anti-biofilm potency of kappa-carrageenan capped silver nanoparticles against Candida species.

Global antimicrobial crisis and advent of drug resistant fungal strains has substantially distressed disease management for clinicians. Biodegradable silver nanoparticles (AgNps) emerge as an excellent alternative remedial option. In the current study, the anti-biofilm activity of microwave irradiated kappa-carrageenan (CRG) capped AgNps against Candida albicans, and Candida glabrata was investigated in terms of their effect on reactive oxygen species (ROS) generation, cellular morphology, biochemical composition, and the activity of enzymes of extracellular matrix. Minimum inhibitory concentration and fungicidal concentration value of CRG-AgNps against both Candida spp. ranged between 400 and 500 µg/mL. The 80% of Candida biofilm was inhibited and eradicated by CRG-AgNps at a concentration of ~300 µg/mL. Microscopic studies indicate that CRG-AgNps caused morphological damage through membrane disruption and pore formation. Further, CRG-AgNps generated ROS in a concentration-dependent manner and modulated the composition of Candida biofilm ECM by increasing the carbohydrate and eDNA content. CRG-AgNps also significantly inactivated the hydrolytic enzymes, thus hindering the biofilm forming ability. In conclusion, all these results suggest that the CRG-AgNps are potential antifungal agents against Candida biofilms, and they inhibit/eradicate the fungal biofilms through multiple signalling mechanisms.