Silver nanoparticles from leaf extract of Mentha piperita: Eco-friendly synthesis and effect on acetylcholinesterase activity.

Silver nanoparticles (AgNPs) have been used in various medicinal and commercial products because of their exceptional anti-microbial and anti-odor properties. On the other hand, increased commercialization of AgNPs containing products has led to its release into the environment. Thus, studies are needed to assess their impact on the environment as well as on human body. Several reports have shown that AgNPs could cause some serious neurotoxic effects. Most of these studies have been performed using chemically synthesized AgNPs. In contrast, green nanoparticles are usually considered safer than their chemically synthesized counterparts. Accordingly, in this research work, we have assessed the effect of AgNPs synthesized from aqueous-leaf-extract of Mentha piperita on one of the most important neurological enzymes i.e. acetylcholinesterase (AChE) to predict its neurotoxicity. M. piperita synthesized AgNPs were subjected to characterization by UV-visible-spectrometry, Scanning Electron-Microscopy as well as Transmission Electron-Microscopy. Here, the size of the AgNPs was found to be 35 nm with spherical shape. These AgNPs showed concentration-dependent inhibitory-effect on the AChE enzyme-activity displaying an IC50 of 150 nM. Further, kinetic analysis showed mixed type of inhibition, which means that AgNPs were capable of binding to both the free enzyme (AChE) and to the enzyme-substrate (AChE-acetylcholine) complex. These results suggest that even green synthesized AgNPs might cause neurotoxicity via inhibiting AChE activity. However, more studies are needed to elucidate the exact mechanism of neurotoxicity by AgNPs. Nevertheless, we could safely state that the present study provides relevant preliminary information regarding neurotoxicity of green synthesized AgNPs.

Gold nanoparticles: A plausible tool to combat neurological bacterial infections in humans.

Management of bacterial infections of central nervous system is a major challenge for the scientists all over the world. Despite the development of various potential drugs, the issue of central nervous system infections persists in the society. The main constraint is the delivery of drugs across the blood brain barrier and only a few drugs after meeting the stringent criteria could cross the blood brain barrier. On the other hand, certain bacterial pathogens could easily enter the brain by using several factors and mechanisms by crossing the blood brain barriers. Interestingly, in the recent past, gold nanoparticles have shown immense potential to overcome the issues associated with the treatment of central nervous system infections, especially due to their inherent ability to cross the blood brain barrier. Initially, the present review summarized the recent updates on the pathogenesis and factors involved in neurological bacterial infections, including the mechanism used by bacterial pathogens to cross the blood brain barriers. Thereafter, the emphasis of the review was on providing current information on gold nanoparticles pertinent to their applicability for the treatment of neurological infections. After discussing the background of neurological bacterial infections, the characteristic features, antibacterial properties, mechanisms of antibacterial action and ability to cross the blood brain barrier of gold nanoparticles have been summarized. Some of the features of gold nanoparticles that make them an ideal candidate for brain delivery are biocompatibity, stability, ability to get synthesized in different sizes with facile methods, surface affinity towards various functional groups, spontaneous crossing of blood brain barrier without applying any external field and most importantly, easy non-invasive tracing by CT imaging. The current updates on the development of gold nanoparticles based therapeutic strategies for the prevention and treatment of central nervous system infections have been discussed in the present study. However, further investigation would be required to translate these preclinical outcomes into clinical applications. Nevertheless, we could safely state that the information gathered and discussed in the present review would benefit the scientists working in the field of neuro-nanotechnology.