Pharmaceutical nanotechnology is the exciting, rapidly emerging branch of medical science that deals with harnessing nanoscale materials as drug delivery and/or diagnostic tools. As drug delivery tools, nano-delivery systems can be used to enhance the site-specific, targeted delivery of precise medicines. This typically results in significant reductions in side effects and concomitant improvements in efficacy.
Nanomedicines have already demonstrated several key advantages, including improved delivery in water-insoluble conditions, extended bioactivity by providing protection of the “payload” against a potentially destructive biological environment, enhanced transport across epithelial and endothelial barriers, and the ability to combine therapeutic and diagnostic activities. Gold nanoparticles, for instance, can be used as biomarkers and tumor labels for biomolecule detection assays.
Nanomedicines run the gamut from chemotherapeutic to biologic to immunotherapeutic agents and more. Nanotech also can be used to enhance selective diagnosis through disease-marker molecules. To be clear, nanomaterials are defined as objects ranging in size between 1 nm and 100 nm, although many experts include particles as large as 1,000 nm which technically are sub-micrometer-sized molecules. They may be organic or inorganic, comprised of materials such as metals, organic compounds, polymers, carbon nanotubes or liposomes. Most often, these objects are spherical in shape, further enhancing their ability to travel freely throughout the body.
To date, the most promising application of nanomedicine has occurred in the arena of chemotherapeutics, where the unique capabilities and complex properties of these cutting-edge delivery devices can greatly improve effectiveness while diminishing potentially harmful, counterproductive side effects.
For example, doxorubicin is an older, common chemotherapeutic agent with notable cardiotoxicity. In the past, its adverse effects on the heart have curtailed its usefulness. But a new liposomal delivery form, in which doxorubicin is encapsulated in lipid nanoparticles, is vastly less cardiotoxic. Thus, nanotechnology has conferred promising new life to this toxic old drug. That’s not to say oncology is the only medical subspecialty to benefit from nanomedicine. The technology is also under investigation for the treatment of cardiovascular and respiratory diseases, among many others.
Opportunities and Challenges Ahead
Some of the challenges and opportunities in nanomedicine involve improving the specificity of these nanostructures to more precisely target specific areas of the body. Another goal is to reduce immunogenicity. The longer the immune system permits nanoparticles to circulate, the more likely they are to reach their intended targets. Strategies to accomplish this include altering their coating or chemical functionalization using a number of substances, including polymers, natural polysaccharides, antibodies, cell membranes (for example, erythrocyte membranes), “tunable” surfactants and peptides.
More than one thousand patents have been issued to date and scores of products have advanced to the clinical trial stage. A large handful of products, including the nano-encapsulated doxorubicin referenced above, already are in use. Essentially, future challenges include improvements in drug loading and release, and further development of the potential of metallic nanoparticles to enhance both diagnosis and treatment.
Gold nanoparticles, for example, are viewed by some experts as especially promising. They are well absorbed by soft tumor tissue and can render tumors susceptible to damage through the application of near-infrared radiation. Thus, selective elimination of these tissues through relatively safe heat therapy becomes possible. It’s tempting to allude to a new gold rush on the horizon.
While this relatively new and undeniably exciting area of research is only about two decades old, many questions remain to be answered before a true revolution in medicine can be declared with any meaningful credibility. Key biological markers of disease remain to be elucidated in many instances, and their precise targeting — without altering normal cellular processes — remains a fertile area of research.