Biofilm inhibition in Candida albicans with biogenic hierarchical zinc-oxide nanoparticles.

The present study demonstrates lignin (L), fragments of lignin (FL), and oxidized fragmented lignin (OFL) as templates for the synthesis of zinc oxide nanoparticles (ZnO NPs) viz., lignin-ZnO (L-ZnO), hierarchical FL-ZnO, and OFL-ZnO NPs. The X-ray diffraction patterns confirmed the formation of phase pure ZnO NPs with a hexagonal wurtzite structure. Electron microscopy confirmed the hierarchical structures with one-dimensional arrays of ZnO NPs with an average particle diameter of 40 nm. The as-synthesized L-ZnO, FL-ZnO, and OFL-ZnO NPs were tested in-vitro for growth and virulence inhibition (morphogenesis and biofilm) in Candida albicans. L-ZnO, FL-ZnO, and OFL-ZnO NPs all inhibited growth and virulence. Growth and virulence inhibitions were highest (more than 90%, respectively at 125, 31.2, and 62.5 µg/mL) in presence of FL-ZnO NPs, indicating that the hierarchical FL-ZnO NPs were potent growth and virulence inhibiting agent than non-hierarchical ZnO NPs. Furthermore, the real-time polymerase chain (RT-PCR) was used to study the virulence inhibition molecular mechanisms of L-ZnO, FL-ZnO, and OFL-ZnO NPs. RT-PCR results showed that the downregulation of phr1, phr2, efg1, hwp1, ras1, als3 and als4, and the upregulation of bcy1, nrg1, and tup1 genes inhibited the virulence in C. albicans. Lastly, we also performed in-vitro test cell cytotoxicity on the cell line, mouse embryo 3T3L1, and in-vivo toxicity on Rats, which showed that FL-ZnO NPs were biocompatible and nontoxic.

Fragmented lignin-assisted synthesis of a hierarchical ZnO nanostructure for ammonia gas sensing.

In the present study, we demonstrated the use of fragmented lignin in the synthesis of a hierarchical-type structure of ZnO nanorods. Lignin was isolated from bagasse by the microwave assisted method and its fragmentation was achieved in alkaline conditions along with hydrogen peroxide. Lignin and fragmented lignin were purified by crystallisation followed by column chromatography and characterized by UV-visible spectroscopy, Frontier infra-red spectroscopy (FTIR), 1H-NMR and high resolution mass spectroscopy (HRMS). Fragmented lignin was utilized as a template for the synthesis of ZnO nanorods, which were characterized by powder XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-DRS for the determination of crystal structure, particle morphology and band gap. XRD of the ZnO samples revealed a hexagonal wurtzite structure. The morphology of ZnO without fragmented lignin showed agglomerated nanoparticles and with fragmented lignin, a self-assembled hierarchical nanostructure due to nanorods of 30 nm diameter and 200-500 nm length was observed. The fragmented lignin showed a pronounced effect on the particle size and morphology of ZnO nanoparticles. We measured the response of the hierarchical ZnO nanostructure (50 ppm) for sensing NH3 in terms of change in voltage across known resistance. We observed the response and recovery upon introduction of the analyte ammonia gas at 175 °C.