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Applications of Nanoparticles for Optical Modulation of Neuronal Behavior
Published in Francesco S. Pavone, Shy Shoham, Handbook of Neurophotonics, 2020
Chiara Paviolo, Shaun Gietman, Daniela Duc, Simon E. Moulton, Paul R. Stoddart
Au NPs have also been used for integration into nanocomposite nerve conduits. Recently Baranes et al. reported a nerve guide fabricated with electrospun nanofibers doped with 10 nm Au NPs (shown schematically in Figure 13.4c). The scaffolds encouraged a longer outgrowth of the neurites in primary neurons of the medicinal leech, preferring axonal elongation over the formation of complex networks [34]. Similarly, Das and coworkers reported on a nerve guide fabricated by adsorbing Au NPs onto silk fibers. This nano-hybrid material was successfully tested in a neurotmesis grade injury (complete axonal loss and conduction failure) of the sciatic nerve of Sprague-Dawley rats over a period of eighteen months. The nano-composites were found to promote adhesion and proliferation of Schwann cells in vitro and did not elicit any toxic or immunogenic responses in vivo [35]. Lin and colleagues tested chitosan-AuNP microgrooved nerve conduits both in vitro and in vivo. The results showed that the conduits pre-seeded with primary neuronal stem cells were able to support regeneration of the sciatic nerve better than the controls [36]. Taken together with the work of Barillé et al. showing neuronal network outgrowth on a phototriggered reconfigurable polymeric substrate [68] (see Section 13.2.4), these studies clearly show that neural regeneration is also influenced by the mechanical support of the guides. Nanoparticle-doped scaffolds open up new strategies to combine bio-materials and nanoparticles for providing physical and/or bioactive environments for neural regeneration. There is also potential to combine the electrical properties of Au NP and bio-materials to promote peripheral nerve elongation [84].
MR neurography of the brachial plexus in adult and pediatric age groups: evolution, recent advances, and future directions
Published in Expert Review of Medical Devices, 2020
Alexander T. Mazal, Ali Faramarzalian, Jonathan D. Samet, Kevin Gill, Jonathan Cheng, Avneesh Chhabra
As the most commonly encountered mechanism of injury to the brachial plexus, traumatic injuries are predictably a common indication for brachial plexus MRN. The aim of MRN in the setting of these injuries is twofold: A) to localize and survey the injury site and its extent, and B) to characterize the severity (grade) of injury. The two most widely utilized classification systems for grading of peripheral nerve injuries are those proposed by Seddon and Sunderland, respectively [45–48]. Seddon’s system was first described in 1943 and has remained popular due to its simplicity and three-tiered grading approach. Using this system, nerve injury is stratified into the following categories: neuropraxia, axonotmesis, and neurotmesis. Neuropraxia refers to focal segmental demyelination without concomitant Wallerian degeneration distal to the injury site, implying the preservation of axonal structures. Neuropraxia generally occurs due to mild compression or traction to the nerve and leads to a decrease in conduction velocity through the injury site [49]. The clinical manifestations of neuropraxia can be variable depending on the extent of local demyelination, ranging from asymptomatic injury to muscle weakness [49]. Axonotmesis refers to a complete axonal injury with resultant distal Wallerian degeneration, but without disruption of the endoneurium or perineurium. Finally, neurotmesis refers to the most severe mechanism of injury described in this model, indicating complete transection of nerve axons and supportive connective tissue layers, resulting in complete discontinuity of proximal and distal nerve segments at the site of injury.