Biogenic Synthesis and Characterization of Silver Nanoparticles: Evaluation of Their Larvicidal, Antibacterial, and Cytotoxic Activities.

To explore the larvicidal activity of the silver nanoparticles (AgNPs) synthesized using the ethanolic Catharanthus roseus flower extract (CRE) against the larvae of Aedes aegypti (A. aegypti), AgNPs were synthesized by an eco-friendly method and characterized by Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Particle Size Analysis, Transmission Electron Microscopy (TEM), and Energy-Dispersive X-Ray spectrometry (EDX) analysis. The resultant AgNPs showed a spherically well-defined, highly stable, and monodispersed shape with an average particle size ranging from 15 to 25 nm. The absorbance of the AgNPs was measured by using a UV-Vis spectrophotometer at a wavelength of 416 nm. The presence and binding of the phenolic functional group with the AgNPs were confirmed using FTIR analysis. Particle size analysis revealed an average particle diameter of 90 nm with 80 % distribution. XRD analysis revealed the highly crystalline nature of the CRE-AgNPs. The LC50 and LC90 values of CRE-AgNPs and the extract were calculated. The mortality percentage of the extract and synthesized CRE-AgNPs was observed after 24 h. The maximum larvicidal activity with 100 % mortality of A. aegypti was observed in AgNPs synthesized using ethanolic CRE. The LC50 and LC90 values are 8.963 and 20.515 ppm for CRE-AgNPs against A. aegypti larvae, respectively. The CRE-AgNPs revealed superior antibacterial activity against human pathogenic bacteria; the zone of inhibition (ZOI) was measured for all of the pathogens, and the results revealed that different concentrations of CRE-AgNPs showed a remarkable ZOI of about (a) 10-14 mm for Salmonella typhimurium, (b) 6-11 mm for Bacillus subtilis, (c) 11-14 mm for Enterococcus faecalis, and (d) 9-10 mm for Shigella boydii. The maximum ZOI was observed in E. faecalis. Impeccably, the cytotoxicity of CRE-AgNPs at 250 µg/mL is 82% against the HaCaT cell lines. The synthesized CRE-AgNPs showed maximum effectiveness of paradoxical activity on mosquito larvae.

Characterisation of pectin and optimization of pectinase enzyme from novel Streptomyces fumigatiscleroticus VIT-SP4 for drug delivery and concrete crack-healing applications: An eco-friendly approach.

Pectinases are enzymes which are widely distributed in microbes that are present in pectin enriched sites. The agro-industrial residues can be utilized in the industrial scale for low-cost and efficient pectinase production in an eco-friendly approach. This study employs low-cost substrates (i.e. culinary fruit peels) for maximum pectinase production from novel Streptomyces fumigatiscleroticus VIT-SP4. The extraction and characterization of pectin from different fruit peels were investigated and pectinase activity was analyzed. The orange pectin gave maximum pectinase activity of about 45.93 (U/mL). Further, statistical optimization of process parameters was studied by using Taguchi method showed optimum values of pH-6, temperature -35 °C, orange pectin% - 2.5, incubation time- 48 h and RPM- 200 rpm and pectinase activity was found to be 98.65 (U/mL). The response surface methodology (RSM) was used for the optimization of media components which revealed that starch -1.17%, yeast extract-2%, and orange pectin% - 0.75% produces maximum pectinase of about 170.05 (U/mL). The drug-delivery study showed drug release was not observed at initial pH 3 after 4 h. The immediate drug release was noted at pH 6 caused due to disintegration of pectin by the pectinase activity. The self-healing of cracks by spray culture technique was investigated. The crack healing was observed up to 0.50 mm wide after 12 days. This confirms the ability of actinomycete spores to survive and they react to form calcite complex directly helps in crack healing process. This low-cost microbial pectinase can be used in drug delivery and concrete crack-healing applications sectors in future.