Biogenic synthesis, characterisation and antifungal activity of gum kondagogu-silver nano bio composite construct: assessment of its mode of action

The biogenic synthesis of silver nanoparticles was achieved by using gum kondagogu (Cochlospermum gossypium), a natural biopolymer (Gk-AgNPs). Synthesised nanoparticles were characterised by using UV–visible spectroscopy, inductively coupled plasma-atomic emission spectrometer, X-ray diffraction, transmission electron microscope techniques. The silver nano particle size determined was found to be 3.6 ± 2.2 nm. The synthesised Gk-AgNPs showed antifungal activity and exhibited minimum inhibitory concentration and minimal fungicidal concentration values ranging from 3.5 to 6.5 µg mL−1 against Aspergillus parasiticus (NRRL-2999) and Aspergillus flavus (NRRL-6513). Scanning electron microscopy–energy dispersive spectroscopy analysis revealed morphological changes including deformation, shrunken and ruptured mycelium of the fungi. At the biochemical level, the mode of action revealed that there was an elevated level of reactive oxygen species, lipid peroxidation, superoxide dismutase, and catalase enzyme activity. Increased oxidative stress led to increased outer membrane damage, which was confirmed by the entry of N-phenyl naphthylamine to the phospholipid layer of outer membrane and higher levels of K+ release from the fungi treated with Gk-AgNPs. This study explores the possible application of biogenic silver nanoparticles produced from gum kondagogu as potent antifungal agents. The potent antifungal activity of Gk-AgNPs gives scope for its relevance in biomedical application and as a seed dressing material.