Functionalized Magnetic Iron Oxide Nanoparticles (FMIONPs) are being explored for the development of various biomedical applications, e.g., cancer chemotherapy and/or several other radiological or diagnostic purposes. However, the effects of these NPs per se on the central nervous system (CNS) injury or repair are not well known. This review deals with different aspects of FMIONPs in relation to brain function based on the current literature as well as our own investigation in animal models of CNS injuries. It appears that FMIONPs are innocuous when administered intravenously within the CNS under normal conditions. However, abnormal reactions to FMIONPs in the brain or spinal cord could be seen if they are combined with CNS injuries e.g., hyperthermia or traumatic insults to the brain or spinal cord. Thus, administration of FMIONPs in vivo following whole body hyperthermia (WBH) or a focal spinal cord injury (SCI) exacerbates cellular damage. Since FMIONPs could help in diagnostic purposes or enhance the biological effects of radiotherapy/chemotherapy it is likely that these NPs may have some adverse reaction as well under disease condition. Thus, under such situation, adjuvant therapy e.g., Cerebrolysin (Ever NeuroPharma, Austria), a suitable combination of several neurotrophic factors and active peptide fragments are the need of the hour to contain such cellular damages caused by the FMIONPs in vivo. Our observations show that co-administration of Cerebrolysin prevents the FMIONPs induced pathologies associated with CNS injuries. These observations support the idea that FMIONPs are safe for the CNS in disease conditions when co-administered with cerebrolysin. This indicates that cerebrolysin could be used as an adjunct therapy to prevent cellular damages in disease conditions where the use of FMIONPs is required for better efficacy e.g., cancer treatment.

Spinal cord injury (SCI) is the world's most disastrous disease for which there is no effective treatment till today. Several studies suggest that nanoparticles could adversely influence the pathology of SCI and thereby alter the efficacy of many neuroprotective agents. Thus, there is an urgent need to find suitable therapeutic agents that could minimize cord pathology following trauma upon nanoparticle intoxication. Our laboratory has been engaged for the last 7 years in finding suitable therapeutic strategies that could equally reduce cord pathology in normal and in nanoparticle-treated animal models of SCI. We observed that engineered nanoparticles from metals e.g., aluminum (Al), silver (Ag) and copper (Cu) (50-60 nm) when administered in rats daily for 7 days (50 mg/kg, i.p.) resulted in exacerbation of cord pathology after trauma that correlated well with breakdown of the blood-spinal cord barrier (BSCB) to serum proteins. The entry of plasma proteins into the cord leads to edema formation and neuronal damage. Thus, future drugs should be designed in such a way to be effective even when the SCI is influenced by nanoparticles. Previous research suggests that a suitable combination of neurotrophic factors could induce marked neuroprotection in SCI in normal animals. Thus, we examined the effects of a new drug; cerebrolysin that is a mixture of different neurotrophic factors e.g., brain-derived neurotrophic factor (BDNF), glial cell line derived neurotrophic factor (GDNF), nerve growth factor (NGF), ciliary neurotrophic factor (CNTF) and other peptide fragments to treat normal or nanoparticle-treated rats after SCI. Our observations showed that cerebrolysin (2.5 ml/kg, i.v.) before SCI resulted in good neuroprotection in normal animals, whereas nanoparticle-treated rats required a higher dose of the drug (5.0 ml/kg, i.v.) to induce comparable neuroprotection in the cord after SCI. Cerebrolysin also reduced spinal cord water content, leakage of plasma proteins and the number of injured neurons. This indicates that cerebrolysin in higher doses could be a good candidate for treating SCI cases following nanoparticle intoxication. The possible mechanisms and functional significance of these findings are discussed in this review.

Use of in vivo models of neurotoxicity caused by psychostimulants is discussed based on author's own research and to find suitable drugs that could induce neuroprotection including nanodelivery. Furthermore, novel therapeutic agents for de-addiction and reducing neurotoxicity following psychostimulants administration are presented.