Nanomaterials Raise New Challenges

Scientists are pursuing nanotechnology-based drug delivery and production technologies, despite protests about unsafe products.
Jul 02, 2006
Volume 30, Issue 7

Jill Wechsler
Nanotechnology holds huge potential for improving the design and manufacture of novel medical therapeutics, medical devices, and combination products. Scientists in industry and academia are investigating methods for using minute particles to deliver drugs to specific organs and cells. The methods are prompting the US Food and Drug Administration to encourage public–private collaborations on initiatives to understand the physical and chemical characteristics of nanomaterials and nanoparticles better as part of its Critical Path Initiative. Analysis of new test methods, development of characterization protocols, and agreement on standards promise to help manufacturers move nanoproducts from preclinical testing to commercialization.

Nanotechnology already is being used in a host of consumer and industrial products, including a growing number of drugs and diagnostics. Nanotechnology involves atom-sized particles that are less than 100 millionths of a millimeter in size. By way of illustration, a human hair is about 80,000 nanometers wide. Reducing particles to nanometer size may increase drug product stability and enhance drug absorption and elimination from the body. These features increasingly are touted by makers of cosmetics and sunscreens. Nanoparticles' ability to pass easily through cellular membranes and tissues is raising high hopes for developing cancer therapies that deliver drugs to target tumor cells with less damage to healthy tissues and fewer toxic side effects.

Support for research

The federal government is spending more than $1 billion per year on the White House National Science and Technology Council's National Nanotechnology Initiative. The National Science Foundation is distributing much of that money to fund research projects ranging from semiconductor nanocrystals and nanoelectromechanical sensors to new materials for propellants and explosives and nanoparticles able to remove contaminants from groundwater. The Department of Defense has a large nanotechnology program for military purposes, and the Department of Energy is focusing on new fuels and energy sources that incorporate nanotechnology.

The Department of Health and Human Services has received about $175 million to spend on nanotechnology research. Much of that money has gone to the National Institutes of Health (NIH), which has identified nanomedicine as one of its major initiatives. NIH is allotting $12 million per year to develop a network of Nanomedicine Development Centers to explore how nanotechnology might enhance a basic understanding of biological concepts and cellular processes.

The immediate goal is to characterize the nanoscale components of the cell quantitatively and to examine how to manipulate molecular nanomachines to improve human health. The long-term hope is that this technology will lead to new methods for repairing cellular structures and treating disease by delivering therapies more directly to cells and tissues.

Conquering cancer

National Cancer Institute (NCI) officials are particularly enthusiastic about the great potential of nanotechnology for detecting cancer at very early stages and for developing more effective and less toxic anticancer therapies. Scientists working with NCI's Alliance for Nanotechnology in Cancer are developing nanoscale devices able to identify rare molecular signals associated with malignancy and genome instability. Nanoscale imaging-contrast agents can spot early tumors and metastatic lesions invisible to the eye. Attaching a magnetic resonance imaging (MRI) contrast agent to a nanoscale particle can target the agent to a specific tumor.

Clinical trials for cancer treatments may be able to assess efficacy much earlier by using highly sensitive, nanosized imaging agents and diagnostics able to determine faster whether a therapeutic agent is reaching its intended target and killing malignant cells. The nanotechnological equivalent of a Trojan horse would be able to smuggle chemotherapeutic drugs inside tumor cells. Nanoscale baskets and cages may deliver targeting agents and therapeutic payloads to parts of the body often blocked by biological barriers. Scientists are finding that gold nanoparticles may be extremely effective in delivering treatments or genetic material to cancerous cells as a way to block tumor activity.

And, smart nanotherapeutics could time the release of a drug or deliver multiple drugs sequentially, as well as provide sustained therapy for chronic cancers.

One visible example is "Abraxane," a nanoparticle formulation of "Taxol" (paclitaxel), which was approved by FDA in February 2005 for metastatic breast cancer. By using human albumin to create nanoparticles of the chemotherapy, Abraxis BioScience (Santa Monica, CA, was able to produce an injectible suspension without the usual toxic solvent. Because it reduces the severity of side effects, a higher dose of Abraxane can be given to patients, thereby increasing efficacy and minimizing safety problems. The manufacturer is studying additional anticancer indications for the drug and seeks to reformulate other water-insoluble anticancer treatments with albumin nanoparticles.

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