Nanosilver is one of the most commercialized nanomaterials in the world. Due to its unique surface plasma resonance performance and excellent antibacterial activities, nanosilver has been widely used in many fields, such as medical area, health care, industrial products and our daily supplies. Meanwhile, the increasing application of nanosilver has drawn more and more attention to its biosafety. Previous toxicological studies have revealed diverse deleterious effects nanosilver may cause, wherein, neurotoxicity is highly concerned. This review mainly focuses on the neurotoxicological effects of nanosilver, and three aspects, including the bioaccumulation of nanosilver in brain and its penetration routes, neurotoxicological effects and the underlying molecular mechanisms, and the influencing factors, are comprehensively discussed. The administration of nanosilver through diverse ways could cause brain silver accumulation, and its penetration routes to the brain were mainly involved with the direct nasal olfactory nerve transfer and the translocation of the blood-brain barrier. The neurotoxicological effects of nanosilver were evidenced by neurobehavioral changes in the exposed animals, histopathological alteration in the brain or cellular morphological changes in neurons and neuroglia cells, and the disturbance in the neurontransmitter secretion. The underlying mechanisms were related with oxidative damage and inflammatory responses. The factors, including particle size, surface coating and silver ion release, would potentially determine nanosilver induced neurotoxicity. Finally, the existing problems in neurotoxicological studies on nanosilver are pointed out, and the future perspectives in this area are proposed. The review would be of great help to risk assessment of the production, application and disposal of nanosilver.
Contents
1 Introduction
1.1 Overview
1.2 The synthesis of nanosilver
1.3 The environmental release of nanosilver
1.4 The toxicological effects of nanosilver
2 The bioaccumulation of nanosilver in brain and its penetration routes
2.1 The bioaccumulation of nanosilver in brain
2.2 The penetration routes of nanosilver to brain
3 The neurotoxicological effects of nanosilver and its molecular mechanisms
3.1 Neurobehavioral changes
3.2 Histopathological effects
3.3 Neurotransmitter changes
3.4 The underlying molecular mechanisms
4 The key factors influencing the neurotoxicity of nanosilver
4.1 Particle size
4.2 Surface coating
4.3 Release of silver ions
5 Conclusion and perspective