Nanomedicine: The Future for Advancing Medicine and Neuroscience

Abstract

Over the last half century, the delivery of pharmacologically active substances, such as synthetic drugs, natural compounds, gene material and many other pharmaceutical products, has been widely studied and investigated [1]. Scientists working in the field of pharmacologically active substances easily understood that the main problem of such molecules is represented by their wide and nonspecific biodistribution once administered in the human body. This reflects in an increase in toxicity and, at the same time, a decrease in patient compliance and a decreased benefit/risk ratio. Another critical issue consists of the tremendous difficulty of such drugs and active molecules in crossing biological barriers [2]. In this view, the development of drug delivery systems (DDS) is aimed at creating carriers able to improve the pharmacokinetic profile of drugs. In addition, the carriers could protect the body from exposure to a great amount of drugs, thus decreasing the circulating doses. Taken together, these aspects represent one of the most innovative improvements of the last decade in pharmaceutical research. This strategy took the fashionable name of ‘nanomedicine’, mainly based on the use of lipid-based (liposomes) and polymer-based (nanoparticles; NPs) nanocarriers or metalbased nanovectors. The last example of nanocarriers (i.e., superparamagnetic NPs) are currently used in medicine in order to improve the quality and the specificity of body/cell imaging and diagnostics. These carriers are usually made of gold or iron, comprising a core–shell able to be visualized within the body, thus allowing the physician to obtain better-defined contrast and diagnostic images. Some examples are Resovist (Shering, Berlin, Germany) and Endorem/Lumirem (Advanced Magnetics, Guebert, France), which are used for liver tumor imaging. Considering the drug delivery and drug targeting aim deputed to nanomedicine, the main advantages of nanocarriers rely on the protection of the active molecule from metabolism and degradation, the possibility of governing the drug release over time and the ability in reaching the target site (mainly organs or tissue) by using a passive route. Despite these applications, which encourage support for the research, the main limits that may hamper the development of such nanocarriers are the lack of selectivity and specificity of DDS. Thus, in order to maximize the therapeutic effect, the new ‘smart’ DDS need to be further engineered to obtain ‘stable and ultra-selective’ carriers able to deliver the drugs not only to the target organ or tissue but also to the target cell. In fact, in the last 10 years, research in nanomedicine has strongly focused on the use of specific ligands (e.g., antibodies, peptides, substrates of receptors and many others) to be conjugated onto the surface of NPs and liposomes, thus enabling nanocarriers to specifically target cell populations or to cross virtually impermeable barriers, such as the blood–brain barrier (BBB) [2]. Some important focuses should be considered when approaching nanomedicine, such as its development in comparison with other innovative approaches (i.e., personalized medicine) and its application to the most difficult-to-treat diseases (i.e., neurodegenerative and neurological disorders).