oa Editorial [Hot Topic: Recent Perspectives on Nanoneuroprotection & Nanoneurotoxicity (Guest Editors: Hari Shanker Sharma and Aruna Sharma)]

Recent developments in nanoparticle research have resulted in new opportunities to target drug delivery to the central nervous system (CNS) for treating various brain diseases [1-3]. Nanoparticle-based drug delivery is generally considered to be innocuous in reaching the CNS targets across the blood-brain barrier (BBB) without damaging it [3, 4]. However, new data emerging in the field suggests that neurotoxicity of nanoparticles must be considered in detail before suitable therapeutic strategies are developed to treat patients using nanomedicine [4]. Thus, the need of the hour is to understand the possible effects of nanoparticles on neurotoxicity in vivo. Few reports in cell culture suggest that several nanoparticles, depending on their size, may induce neurotoxicity [3, 4]. Sporadic in vivo findings show that nanoparticles induce cell and tissue damage in the respiratory system following inhalation in animal models [cf 1, 5]. This damage is inversely proportional to the size of the nanoparticles [5]. However, systematic studies in vivo on neurotoxicity of nanoparticles in the CNS are still lacking. Likewise, drug delivery to the CNS is normally accomplished utilizing different kinds of liposomes or related techniques. Recent development of nanowires from different metals that could potentially trap several drug molecules and release them in vivo when implanted has come up [1, 2]. However, the potential role of nanowired delivery of drugs in the CNS is still not well investigated [5, 6]. Thus, there is an urgent need to understand the role of nanowired drug delivery in relation to the toxicity of the nanowire alone, if any, in the CNS using an in vivo model [6-9]. To further expand these new ideas systematic studies on nanoparticle-induced neurotoxicity in specific CNS regions is highly needed. In addition, it is still unclear whether nanoparticle exposure of healthy individuals or persons with common diseases e.g., hypertension or diabetes will modify brain dysfunction [1, 5]. Furthermore, traumatic injuries to the CNS following nanoparticle intoxication may have dangerous consequences that require adjustment of drug dose [cf 1, 6-8]. These are important questions for policy makers, educators and health service providers that require further investigation. Keeping these new developments in Nanoneuroscience in mind during the past 5 years, there is a need to summarize the current state of the art in the field. This special issue of CNS & Neurological Disorders - Drug Targets focuses on “Nanoneuroprotection and Nanoneurotoxicity”, two faces of the same coin, as addressed by leading world experts. The volume is a referred collection of Invited Reviews by World leaders on Nanoneuroscience and related disciplines comprising neurosurgeons, neurophysiologists, neurpathologists, neurophramacologists and neurologists. The salient new features of this volume includes a commentary by Russell J Andrews (Moffet Field, CA, USA) on novel aspects of nano drug delivery. Dafin F Muresanu (Cluj- Napoca, Romania) and co-workers discussed TiO2 nanowired delivery of antioxidants to treat successfully hyperthermia-induced brain damage. Jose V Lafuente (Bilbao, Spain) and his team present new evidence showing that diabetes-induced brain pathology is aggravated by chronic SiO2 exposure. Neurotoxicity of metal nanoparticles is presented by Hari S Sharma (Uppsala, Sweden) who shows that species differences could play an important part in nanoparticle-induced neurotoxicity. To treat nanoparticle-induced neurotoxicity new drug treatments are needed. In this regard, Aruna Sharma (Uppsala University) shows that cerebrolysin is having superior neuroprotective effects in heat stroke after nanoparticle intoxication, as compared to other drugs in identical doses. Furthermore, a double dose of cerebrolysin is needed to induce marked neuroprotection in hyperthermia after nanoparticle exposure. Nanodrug delivery of metal chelators is able to reduce Alzheimer's disease-induced pathology. This is shown by Mark A Smith (Cleveland, Ohio, USA) and his team clearly. In this context Ryan Z Tian (Fayetteville, AR, USA) and co-workers provide new evidence that nanowired drug delivery using TiO2 nanowires in spinal cord injury is more neuroprotective than the parent compound. However, different compounds used may have different neuroprotective ability. This suggests that nanowired delivery of drugs could enhance their therapeutic efficacy but could not transform a non-performing drug into a neuroprotective agent. Lastly, Preeti Menon (Uppsala, Sweden) and co-workers show that cerebrolysin not only provides neuroprotection in hyperthermia-induced brain pathology following nanoparticle intoxication, but also is quite suitable to induce efficient neuroprotection following spinal cord injury after nanoparticle intoxication. These eight selected reviews focus on key factors of nanopartiocle-induced neurotoxicity and neuroprotection. We believe that new strategies discussed here will open new avenues for research in CNS injury that could lead to exploration of novel drug targets and therapeutic agents. This volume is indispensable for neurophramacologists, neurotoxicologists, nanotechnologists, neuroimmunologists, neurosurgeons, military experts, policy makers, educators and students alike. We sincerely hope that data presented in this volume will stimulate further research in Nanomedicine.