Current Issues Nanomedicine Nanotechnology in Neurology—Current Status and Future Possibilities James M Provenzale, MD1 and Aaron M Mohs, PhD2
1. Professor of Radiology, Department of Radiology, Duke University Medical Center, and Professor of Radiology, Oncology, and Biomedical Engineering, Departments of Radiology, Oncology, and Biomedical Engineering, Emory University School of Medicine; 2. Distinguished Fellow, Department of Biomedical Engineering, Emory-Georgia Tech Center for Cancer Nanotechnology Excellence
Abstract
The field of nanomedicine is rapidly emerging and will provide many novel methods for diagnosis and treatment. In this article the applications of nanotechnology to the central nervous system (CNS) will be described. Nanotechnology provides many potential solutions to various problems encountered in CNS diseases. Specifically, nanomedicine offers the possibility of new methods of drug delivery, more sensitive and specific means for diagnosis of disease at earlier stages and assessment of treatment response, and also potential techniques for neuro-protection and neuro-engineering. In this article, information is provided on the various types of nanoparticles involved in medical applications, the principles of nanoparticle delivery and targeting, and both in vivo and ex vivo uses of nanoscale materials.
Keywords Nanoparticle, iron oxide, quantum dot, nanomedicine, drug, delivery, neuroprotection
Disclosure: The authors have no conflicts of interest to declare. Received: May 5, 2010 Accepted: June 28, 2010 Citation: US Neurology, 2010;6(1):12–7 Correspondence: James M Provenzale, MD, Department of Radiology, Emory University School of Medicine, 1364 Clifton Road, Atlanta, GA 30322. E:
prove001@mc.duke.edu
The term nanomedicine refers to a field in which the advances of nanotechnology are applied to health and medical diseases. This rapidly growing field is based on the remarkable advances being made in nanotechnology, a field in which materials (e.g. nanoparticles) and devices that have a size on the nanometer scale are developed.1
The
relative scale of nanometer-size materials is important to understand when discussing nanomedicine. As a useful example, the diameter of a typical nanoparticle in medical use is in the order of 10–100 nanometers (nm), which is very similar to the size of most viruses and much smaller than a cell. As will be clear from the following discussion, the extremely small size of nanoparticles and other materials on the nano-scale allows for types of interactions with living tissue that are impossible with larger materials.
Nanotechnology has a number of applications to the central nervous system (CNS), including new possibilities for the diagnosis of CNS diseases, novel methods of drug delivery, and, perhaps most intriguingly, innovative methods of regenerating CNS tissues. This article will introduce the reader to the various types of nanoparticles, the principles of nanoparticle delivery and targeting, and in vivo and ex vivo uses of nanoscale materials.
Introduction to Types of Nanoscale Devices An explanation of the types of nanoscale devices is important in order to understand their unique properties, benefits, and limitations. As a result of space limitations, this article will focus solely on nanoparticles rather than many other types of nanomaterials that are
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described in more detail elsewhere.2
Throughout this discussion, the
reader should be aware that the effects of nanomaterials on living human tissue is still a matter of active investigation; although many nanomaterials are believed to be safe for use in the human body, much work remains to understand the toxicology of various materials.3
Liposomes and Micelles
Liposomes are the form of nanoparticle that has found the widest use to date in actual medical applications. These particles consist of two major components: an aqueous core and a surrounding phospholipid bilayer membrane. The aqueous core provides an inner compartment in which a cargo, such as a water-soluble drug, can be carried. The phospholipid bilayer membrane provides a protective coating that insulates the contents of the inner core from degradation as well as from release of contents at unintended sites.4
As such, liposomes can
be designed to provide a timed release at their intended target depending on local physiological conditions (e.g. pH)5
or controlled by external stimuli (such as heat or light) applied by an operator.6
Liposomes are already in clinical use in humans. For instance, liposomes containing doxorubicin have been approved by the US Food and Drug Administration (FDA) for use in ovarian cancer and multiple myeloma.7
In addition, liposomal formulations of chemotherapy are under investigation for primary and secondary brain tumors.8
Micelles have some similarities to liposomes in that they also provide a protective inner environment that allows sequestration of a
© TOUCH BRIEFINGS 2010
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