Nanotechnological applications in medicine

 

       

    

 Nanotechnological applications in medicine  

Nanotechnology-based tools and techniques are rapidly emerging in the fields of medical imaging and targeted drug delivery. Employing constructs such as dendrimers, liposomes, nanoshells, nanotubes, emulsions and quantum dots, these advances lead toward the concept of personalized medicine and the potential for very early, even pre-symptomatic, diagnoses coupled with highly-effective targeted therapy. Highlighting clinically available and preclinical applications, this review explores the opportunities and issues surrounding nanomedicine.

Introduction

‘Molecular imaging’ is a phrase that has come into heavy use within the past decade. It is a broad term, difficult to define. Although the initial use implied imaging novel contrast agents to probe molecular information [1], the current use has evolved to include a wide scope of imaging techniques that use molecular agents or rely on molecular signatures. These include virtually all positron emission tomography imaging (indeed all nuclear medicine techniques requiring radioactive or radiolabeled molecules), magnetic resonance spectroscopy, and other parametric magnetic resonance imaging techniques (like diffusion-weighted imaging). Similarly, the term ‘nanomedicine’ is difficult to define precisely, as much of what transpires in human biology happens at the nanometer scale. Thus, one might successfully argue that all medicine is ‘nanomedicine’. Herein, we discuss nanomedicine as the application of technologies on the scale of approximately 1 to 500 nm toward the goal of diagnosing and treating disease.

Within the past decade, there has been a plethora of new research, development and patent activities around nanoscaled technologies in the health sciences field [2•]. One indicator of this is the flurry of activity around the National Nanotechnology Initiative [3] of the US government and, in particular, those initiatives of the National Institutes of Health (NIH). Within the National Cancer Institute (NCI) alone, the Alliance for Nanotechnology in Cancer program (http://nano.cancer.gov/) has launched eight Centers of Cancer Nanotechnology Excellence (http://nano.cancer.gov/programs/ccne.asp) and twelve Cancer Nanotechnology Platform Partnerships (http://nano.cancer.gov/programs/nanotech_platforms.asp) [4]. The Program for Excellence in Nanotechnology (http://www.nhlbi-pen.info/) of the National Heart, Lung and Blood Institute is another instance of the profuse programs fueling this growing research arena. To help facilitate the transfer of nanotechnological research into clinical practice, the NCI, in conjunction with the National Institute of Standards and Technology and the US Food and Drug Administration (FDA), has also established the National Characterization Laboratory (http://ncl.cancer.gov/).

The overall goal of nanomedicine is the same as it always has been in medicine: to diagnose as accurately and early as possible, to treat as effectively as possible without side effects, and to evaluate the efficacy of treatment non-invasively. The promise that nanotechnology brings is multifaceted, offering not only improvements to current techniques but also providing entirely new tools and capabilities. By manipulating drugs and other materials at the nanometer scale, the fundamental properties and bioactivity of materials can be altered. These tools can permit control over characteristics of drugs or agents such as solubility, blood pool retention times, controlled release over short or long durations, environmentally triggered controlled release or highly specific site-targeted delivery. Furthermore, by using nanometer-sized particles, the increased functional surface area per unit volume can be exploited in various ways.

This review presents some of the more recent successes of applying various new nanotechnological techniques and tools in diagnostic imaging and therapeutics, including both current products and late-stage preclinical research. It will not delve into screening or in vitro diagnostics, although nanotechnological applications certainly abound in these areas (e.g. improvements to ‘laboratory on a chip’ technologies like microarrays and microfluidics [5, 6]). Nor will this review focus on the many advances in biomedical laboratory research tools and techniques resulting from nanotechnology.

Section snippets

Diagnostic imaging in nanomedicine

Combining advances in related fields such as genomics, proteomics, drug delivery and molecular imaging, nanomedicine offers the potential to move from a ‘one-size-fits-all’ approach to one more individually tailored for higher efficacy [1, 7]. For diagnosis, this translates to recognition and characterization of very early (even pre-symptomatic) disease providing assessment, preferably non-invasively, akin to that of immunohistochemistry. Of course doing so is complex, requiring simultaneous

Controlled drug delivery

Unfortunately, early diagnosis is futile if not coupled with effective therapy. Owing in part to the national nanotechnology initiatives, there has been much activity in applying nanotechnology to therapeutics [38, 39, 40, 41, 42•]. Currently, there are limited numbers of nanomedical products on the market [2•], with the majority being pharmaceuticals that are formulated (or re-formulated) into nanosized structures to manipulate the pharmacodynamics, biodistribution and overall effectiveness.

Limitations and considerations in nanomedicine

Obviously, not all attempts to apply new nanotechnology approaches in medicine have met with the same success as those cited herein. The new tools are not necessarily intuitive and bring with them new challenges and hurdles. Nanometer-sized structures do not behave in the same predictive ways that single, small-molecule interactions occur. Nanoconstructs, especially multifunctional ones, are complex three-dimensional objects with critical dependence on position, size, shape and charge of

Conclusions

Nanotechnology, in general, is experiencing a rapid growth period with major advances arriving quickly. Accordingly, these advances are applied in the biomedical field in numerous diverse ways. Already, a few medical products are providing a glimmer of the overwhelming benefits nanomedicine will surely provide. Current preclinical research promises new ways to diagnose disease, to deliver specific therapy, and to monitor the effects acutely and non-invasively. This rapid onset and drastic

Disclosure statement

SDC is an employee of Philips Medical Systems. SAW and GML receive research grant funding from Philips Medical Systems and are equity shareholders in Kereos.

References and recommended reading

Papers of particular interest, published within the annual period of review, have been highlighted as:

• of special interest

•• of outstanding interest