Bimetallic nanocomposite (Ag-Au, Ag-Pd, Au-Pd) synthesis using gum kondagogu a natural biopolymer and their catalytic potentials in the degradation of 4-nitrophenol

Bimetallic nanoparticles (BNPs) constitute two different metal elements and exhibit relatively superior mechanistic and catalytic efficacies owing to their synergistic functions over monometallic nanoparticles. In the present study various bimetallic Ag-Au, Ag-Pd, Au-Pd nanoparticles were synthesized using a natural biopolymer gum kondagogu (GK) as a reducing and capping agent, by a simple and cost-effective method. The synthesized BNPs when characterized using UV-vis spectroscopy revealed a specific surface plasmon resonance band (SPR) of each nanocomposite. The average particle size of Ag-Au, Ag-Pd, and Au-Pd BNPs was found to be 23 ± 10.3, 21 ± 7.6, and 23 ± 9.4 nm respectively based on transmission electron microscopy analysis. Surface morphology and functional groups on the gum matrix of GK-BNPs were analyzed by XRD and FT-IR respectively. The bimetallic nanocomposites were evaluated for their catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol in the presence of NaBH₄. The kinetic studies performed, depicted rate constants for Ag-Au, Ag-Pd, and Au-PdNPs as 0.31, 0.39, and 0.28 min^-1 respectively. The catalytic efficiencies of three bimetallic nanocomposites were of the following order Ag-Pd > Ag-Au > Au-Pd. This study establishes the catalytic potentials of the three different bimetallic nanocomposites in the reduction of 4-NP an environmental pollutant, and the impact of their synergistic property.

Synthesis, characterisation and anti-tumour activity of biopolymer based platinum nanoparticles and 5-fluorouracil loaded platinum nanoparticles

A facile and green synthesis of platinum nanoparticles [gum kondagogu platinum nanoparticles (GKPtNP)] using biopolymer- gum kondagogu was developed. The formation of GKPtNP was confirmed by ultraviolet (UV)-visible spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, Zeta potential, Fourier transform infrared, inductively coupled plasma mass spectroscopy. The formed GKPtNP are well dispersed, homogeneous with a size of 2-4 ± 0.50 nm, having a negative zeta potential (-46.1 mV) indicating good stability. 5-Fluorouracil (5FU) was loaded onto the synthesised GKPtNP, which leads to the development of a new combination of nanomedicine (5FU-GKPtNP). The in vitro drug release studies of 5FU-GKPtNP in pH 7.4 showed a sustained release profile over a period of 120 min. Agrobacterium tumefaciens induced in vitro potato tumour bioassay was employed for screening the anti-tumour potentials of GKPtNP, 5FU, and 5FU-GKPtNP. The experimental results suggested a complete tumour inhibition by 5FU-GKPtNP at a lower concentration than the GKPtNP and 5FU. Furthermore, the mechanism of anti-tumour activity was assessed by their interactions with DNA using agarose gel electrophoresis and UV-spectroscopic analysis. The electrophoresis results revealed that the 5FU-GKPtNP totally diminishes DNA and the UV-spectroscopic analysis showed a hyperchromic effect with red shift indicating intercalation type of binding with DNA. Over all, the present study revealed that the combined exposure of the nanoformulation resulted in the enhanced anti-tumour effect.

Tree gum stabilised selenium nanoparticles: characterisation and antioxidant activity

Selenium nanoparticles (Se NPs) were synthesised using sodium borohydride as a reductant and gum kondagogu as a stabiliser. Plant gum serves as a renewable, non-toxic, non-immunogenic, biopolymer based feedstock. Role of gum on synthesis and mean particle size was studied using ultraviolet-visible spectroscopy and dynamic light scattering. NP generation was visualised with orange red colouration and NPs exhibited a surface plasmon resonance peak at 250 nm. Formed NPs were amorphous, polydisperse and spherical. NPs showed a bimodal distribution, size varied from 44.4 to 200 nm and mean particle size was 105.6 nm. NP solution exhibited a zeta potential of -39.9 mV, confirming the superior stability. In comparison to ionic Se, the gum capped Se NPs exhibited superior 1, 1-diphenyl-2-picrylhydrazyle and 2, 2-azinobis-(3-ethylbenzthinzoline-6-sulphonic acid) radial scavenging activities of 73.2 and 92.2%, respectively, at 25 µg/ml. Antibacterial potential of NPs was checked with well diffusion assay. NPs exhibited growth inhibition activity against Gram-positive bacteria only. Bacillus subtilis and Micrococcus luteus showed respective inhibition zones of 6.3 and 8.6 mm at 12 µg. Thus, the present study demonstrates the applicability of tree gum stabilised Se NPs as a potent antioxidant nutrition supplement at a much lower dose, in comparison with ionic Se.