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Resveratrol, a polyphenolic and biocompatible molecule, exhibits significant pharmacological effects but has poor bioavailability and metabolic stability. It appears in two isomeric forms trans-(E)-resveratrol (tRes) and cis-(Z)-resveratrol (cRes). Many pharmacological activities studied so far are of tRes and is the most stable, predominant, and natural form. cRes is not commercially available due to difficulty in its purification and hence not explored much for its biological activities. Therefore, our study focuses on investigating the stability and therapeutic potential of cRes through its bio-conjugation to nanomaterial. In this study, tRes reduces gold ions to gold nanoparticles (GNPs) and itself gets oxidized to its isomeric form cRes. The isomeric switching was evidenced through cRes characteristic spectral differences and chromatographic elution pattern. The monodispersed GNPs of 25.6 ± 0.4 nm size was formed having zeta potential of −19 ± 3.82 mV confirming it to be a stable formulation. The stability studies were further extended to be tested under different physiological fluids. The cRes loaded GNPs (cRGNPs) reflecting the biological activity of cRes presented equivalent antioxidant property to that of tRes even at low concentrations. Also, cRGNPs showed the hemocompatibility by presenting no hemotoxicity and simultaneous in vitro anti-hemolytic activity. Therefore, the stability provided to cRes upon conjugating to GNPs can further be exploited to study the biological activities of cRes through its nano-conjugated delivery. [ABSTRACT FROM AUTHOR]

The green synthesis of gold nanoparticles has attracted tremendous interest owing to their unique physicochemical properties and widespread applications which are primarily size-dependent. The stability, less reaction time, and use of biological resources as novel nanofactories as an alternative to conventional synthesis strategies are the main objectives of green synthesis approaches. However, to attain size-controlled synthesis from the biogenic route is still a challenge. Hence, use of nontoxic stabilizers becomes increasingly essential. Herein, we describe an emerging, simple, nonconventional approach to synthesize stable and size-controlled biogenic nanogold using cell lysate supernatant containing nitrate reductase of Bacillus licheniformis in the presence of Tween 20 and dodecanethiol respectively. The face-centered central composite design used for the optimization of gold nanoparticles (AuNPs) biosynthesis. The maximum AuNPs biosynthesis obtained using the optimized media variables, glucose (2.1 g/L), peptone (14.05 g/L), yeast extract (4.14 g/L), and potassium nitrate (3.91 g/L) was 0.769 a.u. Highly stable monodispersed nanogold of 10.4 ± 0.6 nm and 12.5 ± 0.9 nm sizes arranged in ordered self-assembly was obtained. The stability profile and kinetics of bioreduction was evaluated with respect to time, and the involvement of the nitrate reductase enzyme in bioreduction was validated by inhibitor study. The physicochemical properties of biogenic nanoparticles were characterized using multiple spectroscopy and microscopy techniques. The obtained nanogold demonstrated excellent bactericidal property against both gram-negative and gram-positive bacteria in size-dependent manner and thus could find tremendous utility in clinical, biological, and environmental applications as a broad-spectrum antibacterial agent. [ABSTRACT FROM AUTHOR]

Context: The development of a reliable, eco-friendly process for synthesis of gold nanoparticles (AuNPs) has gained impetus in recent years to counter the drawbacks of chemical and physical methods. Objective: This study illustrates simple, green synthesis of AuNPs in vitro using cell lysate supernatant (CLS) of non-pathogenic bacteria and to investigate its potential antimicrobial activity. Materials and methods: Gold nanoparticles were synthesized by the reduction of precursor AuCl4 − ions using the CLS of Bacillus licheniformis at 37°C upon 24 h of incubation. The nanoparticles were characterized for their morphology, particle size, optical absorption, zeta potential, and stability. Further the antimicrobial activity was assayed using cup-plate method. Results: The process of biosynthesis was extracellular and the gold ions were reduced to stable nanogold of average size 38 nm. However, upon storage of AuNPs for longer duration at room temperature stability was influenced in terms of increase in particle size and decrease in zeta potential with respect to as synthesized nanoparticles. SEM micrographs revealed the spherical shape of AuNPs and EDX analysis confirmed the presence of gold in the sample. Also clear zone of inhibition was observed against Bacilllus subtilis MTCC 8364, Pseudomonas aeruginosa MTCC 7925, and Escherichia coli MTCC 1698 confirming the antimicrobial activity of AuNPs. Discussion: The bioprocess under study was simple and less time consuming as compared to other methods as the need for harvesting AuNPs from within the microbial cells via downstream process will be eliminated. Nanoparticles exhibited good stability even in absence of external stabilizing agents. AuNPs showed good antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria. Conclusion: The extracellular biosynthesis from CLS may serve as a suitable alternative for large scale synthesis of gold nanoparticles in vitro. The synthesis from lysed bacterial cell strongly suggests that exposure of microbial whole cells to the gold solution for nanoparticle formation is not necessary and that microorganism even in lysed state retained its bioreduction potential. Further the potential of biologically synthesized AuNPs as antimicrobial agents will be of great commercial importance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable synthesis of cis -Resveratrol (cRes) capped gold nanoparticles biologically. • cRes functionalized gold nanoparticles (GNPs) increased the proliferation, migration, and differentiation of the MC3T3-E1 cells. • cRes capped GNPs showed osteo-modulatory properties by increasing the levels of alkaline phosphatase and calcium deposition. • cRes passivated GNPs enhanced expression of osteoblastic genes like RUNX2, OPN, OCN, BMP, OPG, and Col1A. Resveratrol, a stilbene, particularly trans- isomer, shows significant osteogenic potential but experiences high instability and poor bioavailability. However, cis- isomer (cRes) is not explored yet due to its instability. Our study investigates the osteoinductive potential of cRes for the first time by stabilizing it onto the surface of gold nanoparticles. cRes capped GNPs (cRGNPs) presented no toxic effects on the MC3T3-E1 cells with increased levels of alkaline phosphatase and calcium deposition. The nanoparticles presented a 2.6-fold increase in cell number compared to the control. The pro-migratory effect of the cRGNPs was also significantly higher (97.21 ± 0.99 % migration) in 4 days. The osteoinductivity was further confirmed by enhanced expression of osteoblastic genes like RUNX2, OPN, OCN, BMP, OPG, and Col1A. The stability provided to cRes upon conjugating to GNPs allowed exploration of its potential in aiding proliferation, migration, and differentiation of the pre-osteoblasts, which will be beneficial in repairing bone defects. [ABSTRACT FROM AUTHOR]