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The problem of chemically synthesized nanoproducts motivated scientific community to explore ecofriendly methods of nanosynthesis. Diatoms belong to a group of aquatic, unicellular, photosynthetic microalgae have been scarcely investigated as a source of reducing and capping agents for nanosynthesis of pesticides and antibiotics. The present study reports a novel ecofriendly method for the fabrication of bioactive gold nanoparticles using locally isolated Nitzschia diatoms. The diatom-fabricated gold nanoparticles show characteristic ruby red colored with sharp absorbance peak at 529 nm. Electron microscopy confirmed irregular shape of gold nanoparticles, with average size of 43 nm and zeta potential of -16.8 mV. The effects of gold nanoparticles on diatom viability were investigated using light and electron microscopy. The mechanistic approach to shed light on how diatoms reacted after exposure to gold metal salt revealed that exposure to gold chloride triggers elevated levels of catalase and peroxidase (12.76 and 14.43 unit/mg protein, respectively) to relieve reactive oxygen species (ROS) stress induced by gold salt exposure. Investigation studies on mechanisms behind Nitzschia-mediated gold nanoparticles fabrication outlined the role of diatom proteins, polysaccharides in reduction, and stabilization of nanoparticles as confirmed by FT-IR analysis. Bioactivity of gold nanoparticles was accessed by coupling them with antibiotics (penicillin and streptomycin), which increased their antibacterial activity compared to individual nanoparticles and antibiotics (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). Overall, the present novel phyco-nanotechnological approach is a promising tool to be used as sustainable strategy in green nanotechnology as well as to reduce use of antibiotics in microbial control.

Before applying nanotechnologies in biomedical and environmental areas it is advised to study interactions of nanoparticles and other nanomaterials with biomacromolecule present in living system. Moreover there is scarcity of reports on interactions between nanoparticles and biomaterials. In present report a rapid, ecofriendly method of fabricating stable gold nanoparticles (AuNPs) using latex of Jatropha curcas is reported for the first time. AuNPs found to have characteristic absorption maxima centered at 540nm, multiple irregular shapes with size range from 20 to 50nm and have crystalline nature. Latex fabricated AuNPs were found to inhibit catalytic potential of trypsin (a vital enzyme responsible for digestion, insecticide resistance and in several disease conditions). The interactions between AuNPs and trypsin were analyzed by UV-vis spectrophotometry and microwave plasma-atomic emission spectrometry which suggests formation of trypsin-AuNPs complex responsible for lowering catalytic activity of trypsin. Transmission electron microscopy, Fourier transform infrared spectroscopy and particle size distribution studies further confirm complex formation between trypsin and AuNPs. Diverse interactions of metal nanoparticles with proteins such as covalent interaction, electrostatic interactions and binding to SH group of amino acid may be the reasons behind inhibition of trypsin activity. In vivo studies on serum of several vectors and agriculturally important pests supported instrumental results on AuNPs induced trypsin inhibition. This work will bring a new research direction to explore eco-friendly nanoparticle in insect control via inhibition of enzyme catalytic potential., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: 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., Methods: In this study, plant latex was used as reducing and capping agent to synthesize gold nanoparticles. Latex fabricated gold nanoparticles were characterized by different analytical techniques such as UV-Vis spectroscopy, Fourier transforms infrared spectroscopy, dynamic light scattering, zeta potential, transmission electron microscopy and X-ray diffraction. Potential of sunscreen preparations containing gold nanoparticles to protect skin from UV radiation was investigated by in vitro sun protection factor analysis. Transmission electron microscopy and UV-Vis spectroscopy techniques were used to get insight into mechanism by which AuNPs enhance sun protection factor of sunscreen., Results: Monodisperse gold nanoparticles were synthesized using plant latex without need of hazardous chemical reducing and capping agents. Gold nanoparticles showed surface plasmon resonance peak at 550 nm in UV-Vis spectroscopic study. Gold nanoparticles were spherical and triangular in shape with size range of 30-50 nm. The zeta potential of gold nanoparticles was found to be -9.39 ± 0.19 mV. XRD analysis confirmed face-centred cubic (fcc) structure of gold nanoparticles. Incorporation of latex synthesized gold nanoparticles (2 and 4 [% w/w]) into commercial sunscreens increased the sun protection factor from 2.43 ± 0.74 to 24.11 ± 0.46% than sunscreen devoid of gold nanoparticles. From UV-Vis absorption spectroscopy and TEM analysis, it was observed that gold nanoparticles enhance the sun protection factor of commercial sunscreens due to reflection and scattering of UV radiation., Conclusion: Phytolatex synthesized gold nanoparticle is novel agent to enhance sun protection factor of commercial sunscreens. Gold nanoparticles aggregation in commercial sunscreen was the main factor behind SPF enhancement. This study showed that gold nanoparticles are potent alternative to traditionally used hazardous titanium dioxide and zinc oxide nanoparticles in sunscreen., (© 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.)