Rahul B. Salunkhe

Plant Extract: A Promising Biomatrix for Ecofriendly, Controlled Synthesis of Silver Nanoparticles

Uses of plants extracts are found to be more advantageous over chemical, physical and microbial (bacterial, fungal, algal) methods for silver nanoparticles (AgNPs) synthesis. In phytonanosynthesis, biochemical diversity of plant extract, non-pathogenicity, low cost and flexibility in reaction parameters are accounted for high rate of AgNPs production with different shape, size and applications. At the same time, care has to be taken to select suitable phytofactory for AgNPs synthesis based on certain parameters such as easy availability, large-scale nanosynthesis potential and non-toxic nature of plant extract. This review focuses on synthesis of AgNPs with particular emphasis on biological synthesis using plant extracts. Some points have been given on selection of plant extract for AgNPs synthesis and case studies on AgNPs synthesis using different plant extracts. Reaction parameters contributing to higher yield of nanoparticles are presented here. Synthesis mechanisms and overview of present and future applications of plant-extract-synthesized AgNPs are also discussed here. Limitations associated with use of AgNPs are summarised in the present review.

Phytolatex synthesized gold nanoparticles as novel agent to enhance sun protection factor of commercial sunscreens

To study the potential of phytolatex (latex of Jatropha gossypifolia) fabricated gold nanoparticles as promising candidate in sunscreen formulations for enhancement in sun protection factor.

Innovative approach for urease inhibition by Ficus carica extract–fabricated silver nanoparticles: An in vitro study

In the present study, a rapid, low‐cost, and ecofriendly method of stable silver nanoparticles (AgNPs) synthesis using leaves extract of Ficus carica (F. carica), a plant with diverse metabolic consortium, is reported for the first time. An absorption peak at 422 nm in UV–Vis spectroscopy, a spherical shape with an average size of 21 nm in transmission electron microscopy, and crystalline nature in X‐ray powder diffraction studies were observed for the synthesized AgNPs. Fourier transform infrared analysis indicated that proteins of F. carica might have a vital role in AgNP synthesis and stabilization. AgNPs were found to inhibit urease, a key enzyme responsible for the survival and pathogenesis of the bacterium, Helicobacter pylori. Inhibition of urease by AgNPs was monitored spectrophotometrically by the evaluation of ammonia release. The urease inhibition potential of AgNPs can be explored in the treatment of H. pylori by preparing novel combinations of standard drugs with AgNPs‐ or AgNPs‐encapsulated drug molecules.

Catalytic and synergistic antibacterial potential of green synthesized silver nanoparticles: Their ecotoxicological evaluation on Poecillia reticulata

In the present study, stable silver nanoparticles (AgNPs) were fabricated at a rapid rate from leaf extract of medicinally important plant Alstonia macrophylla. Biosynthesized AgNPs are of spherical shape and narrow size (70 nm), exhibiting a surface plasmon resonance peak at 435 nm, and a zeta potential of –30.8 mV and have a crystalline nature. A diverse biochemical consortium of protein, terpenoids, phenolics, and flavonoids in leaf extract of A. macrophylla was found to be responsible for AgNP synthesis as evidenced from qualitative–quantitative chemical analysis and Fourier transform infrared spectroscopy studies. Nitroaromatic compounds are anthropogenic pollutants with long‐lasting environmental persistence and are needed to transform into less toxic derivatives. 4‐Nitrophenol and p‐nitroaniline were reduced to less hazardous and commercially useful 4‐aminophenol and p‐phenylenediamine by phytosynthesized AgNPs. Rate constants of 0.052 and 0.040 Min−1 were calculated for 4‐nitrophenol and p‐nitroaniline reduction, respectively. Thin‐layer chromatography also confirms the reduction of these nitroaromatic compounds. Combinational studies could be one of the strategies to overcome microbial resistance to antibiotics. In synergistic antibacterial assay, the highest increase in a fold area of 3.84 was reported against Staphylococcus aureus using a combination of AgNPs with penicillin. Biosynthesized AgNPs were found to be less toxic (LC50 = 9.13 ppm) than chemically synthesized AgNPs having a LC50 value of 2.86 ppm against nontarget fish Poecillia reticulata. Our green nanosynthesis method offers a faster rate of formation of stable AgNPs having antibacterial and catalytic potential with lower environmental toxicity.

Effect of wax degrading bacteria on life cycle of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae)

The pink mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) is a polyphagous insect pest with protective wax covering. Bacterial isolates originating from M. hirsutus cadavers were screened for their wax degrading effects and the three most potent wax degrading isolates were identified to be Serratia marcescens, Pseudomonas aeruginosa and Bacillus subtilis by 16S rRNA gene sequencing. Bacteria degrading M. hirsutus wax reduced female longevity, offspring production as well as weight and wax content of emerging adults. Treatment with S. marcescens was the most effective in reducing wax content, fecundity and honeydew production. Analysis of honeydew produced by M. hirsutus after each microbial treatment revealed reduction in amino acids, proteins, and reducing sugars concentration compared to controls. Most negative effect on reducing sugars was observed in the B. subtilis treatment suggesting disequilibrium in mealybug metabolism. S. marcescens and P. aeruginosa treatments showed significantly lower content of wax as compared to control suggesting utilization of wax as carbon source by these microorganisms. This study suggests that the use of each of three bacterial isolates reduces wax content of mealybug and might be useful in devising mealybug control strategies.