Toxic implications of silver nanoparticles on the central nervous system: A systematic literature review

Abstract

Silver nanoparticles have many medical and commercial applications, but their effects on human health are poorly understood. They are used extensively in products of daily use, but little is known about their potential neurotoxic effects. A xenobiotic metal, silver, has no known physiological significance in the human body as a trace metal. Biokinetics of silver nanoparticles indicates its elimination from the body via urine and feces route. However, a substantial amount of evidence from both in vitro and in vivo experimental research unequivocally establish the fact of easier penetration of smaller nanoparticles across the blood–brain barrier to enter in brain and thereby interaction with cellular components to induce neurotoxic effects. Toxicological effects of silver nanoparticles rely on the degree of exposure, particle size, surface coating, and agglomeration state as well as the type of cell or organism used to evaluate its toxicity. This review covers pertinent facts and the present state of knowledge about the neurotoxicity of silver nanoparticles reviewing the impacts on oxidative stress, neuroinflammation, mitochondrial function, neurodegeneration, apoptosis, and necrosis. The effect of silver nanoparticles on the central nervous system is a topic of growing interest and concern that requires immediate consideration.

Dose-dependent biological toxicity of green synthesized silver nanoparticles in rat’s brain

“…Secondly, green synthesized AgNPs are capped with flavonoids, including quercetins, that have potent antioxidant characteristics and their ability to ameliorate oxidative damage 17 , 18 , 50 , 59 , 69 . These two interpretations are further supported by Suthar et al 56 , stating that NP coating is used to improve stability by reducing agglomeration, minimizing oxidation, and restricting ionic release. And that Several studies have discovered a relationship between coating characteristics and toxicity.…”

“…This was further confirmed by Opris et al 58 who also added that these changes were not only dose-dependent but time-dependent too. The present distribution of green synthesized AgNPs inside the brain could be attributed to the affinity of the flavonoids cap and silver to sulfur and phosphorus elements 59,60 , which are present mostly in different proteins forming these membranes (walls) and the myelin sheath layers in addition to the proteins that act as enzymes or have other functions in the cytoplasm 56 .…”

“…This could improve the pharmacokinetic properties of AgNPs by increasing the time of circulation. On the other hand, the biosynthesized AgNPs are expected to acquire an unavoidable protein corona in vivo, due to their exposure to plasma proteins in its route through the bloodstream, which would add further stabilization to the nanoparticles in the biological medium in addition to altering their biological activity 55 , 56 .…”

May PdCu@f‐MWCNT NPs be an ecotoxicologic risk?

“…The smaller the particle, the larger its surface area and the stronger its interaction with biological systems. [ 50 ] While particle size is an important consideration in toxicity studies, the physico‐chemical properties specific to NPs size and shape are also important. Therefore, any change in the size and shape of NPs of the same material can change the toxicity depending on the change of physico‐chemical properties and hence their environmental behavior.…”

Methods for Enhancing the Electrical Properties of Epoxy Matrix Composites

“…Currently, additives in the form of conductive polymers (most commonly polyaniline) [22][23][24][25] and carbon fillers (graphite, graphene, conductive carbon black, carbon nanotubes) are mainly used [14,[26][27][28][29][30][31][32][33][34][35][36]. At the same time, the use of metal modifiers of epoxy resin is abandoned, because, firstly, they significantly increase the weight of the whole composite, and, secondly, their nanoparticles are undesirable due to their toxic properties [37][38][39][40][41] and possibility of carcinogenicity [42]. However, recent studies show that there is an opportunity to use metal nanoparticles as modifiers of carbon fillers [43][44][45]; limiting them in this manner and incorporating them into the structure of other molecules increases their overall size, thus reducing negative effects on living organisms.…”