Abstract
Due to their unique physical, chemical, and optical properties, gold nanoparticles (AuNPs) have recently attracted much interest in the field of nanomedicine, especially in the areas of cancer diagnosis and photothermal therapy. Because of the enormous potential of these nanoparticles, various physical, chemical, and biological methods have been adopted for their synthesis. Synthetic antioxidants are dangerous to human health. Thus, the search for effective, nontoxic natural compounds with effective antioxidative properties is essential. Although AuNPs have been studied for use in various biological applications, exploration of AuNPs as antioxidants capable of inhibiting oxidative stress induced by heat and cold stress is still warranted. Therefore, one goal of our study was to produce biocompatible AuNPs using biological methods that are simple, nontoxic, biocompatible, and environmentally friendly. Next, we aimed to assess the antioxidative effect of AuNPs against oxidative stress induced by cold and heat in Escherichia coli, which is a suitable model for stress responses involving AuNPs. The response of aerobically grown E. coli cells to cold and heat stress was found to be similar to the oxidative stress response. Upon exposure to cold and heat stress, the viability and metabolic activity of E. coli was significantly reduced compared to the control. In addition, levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and leakage of proteins and sugars were significantly elevated, and the levels of lactate dehydrogenase activity (LDH) and adenosine triphosphate (ATP) significantly lowered compared to in the control. Concomitantly, AuNPs ameliorated cold and heat-induced oxidative stress responses by increasing the expression of antioxidants, including glutathione (GSH), glutathione S-transferase (GST), super oxide dismutase (SOD), and catalase (CAT). These consistent physiology and biochemical data suggest that AuNPs can ameliorate cold and heat stress-induced oxidative damage in E. coli. Our results indicate that AuNPs may be effective antioxidants. However, further studies are needed to confirm the role of AuNPs as antioxidative agents, as well as their mechanism of action.
Highlights
Gold nanoparticles (AuNPs) are being used in biomedical applications such as cancer therapy, cellular imaging, molecular diagnosis, and targeted therapy, and as contrast agents, photothermal agents, and radiosensitizers
We explored a novel bacterium, B. clausii, for synthesis of AuNPs by the addition of selected culture supernatant to 1 mM aqueous HAuCl4 at 40 ̋ C
The levels relative to the stress-induced E. coli. These results suggest that the inhibition of bacterial growth due of MDA were significantly higher in cold and heat stress-induced E. coli than in the controls
Summary
Gold nanoparticles (AuNPs) are being used in biomedical applications such as cancer therapy (as drug carriers), cellular imaging, molecular diagnosis, and targeted therapy, and as contrast agents, photothermal agents, and radiosensitizers. The physical and chemical methods appear to be simple, they have numerous disadvantages, such as the necessity for high temperatures and pressures and toxic chemicals; most importantly, they can cause the particles to become unstable or aggregate upon interaction with biological media or biomolecules [3,4,5]. They require a long centrifugation process to produce multi-shaped or controlled-size particles. Several reports have demonstrated synthesis of AuNPs using a variety of biological materials, exploration of novel biological materials is warranted, because every living entity has unique surface functionalization properties that can provide significant biocompatibility to targeting agents
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
