Nanotech Meets Medicine

Nanotechnology is a developing field that is showing promise in a number of areas. One such area discussed at the 11th annual Food & Drug Administration Science Forum last month is medicine. The size of nanoparticles is on the same order of magnitude as biological materials; thus, nanotechnology can aid in improving the efficiency and effectiveness of things like drug delivery and bioimplants.

In the area of drug delivery, Jennifer L. West, joint professor in chemical engineering and in biomedical engineering at Rice University, is directing research using nanoshell systems for drug delivery. The nanoshells are tiny spheres with dielectric silica cores covered with a layer of gold nanoparticles.

The key for using these nanoshells for drug delivery is their tunable optical wavelength properties. This tunablity is dependent on the gold nanoshell thickness and has been varied by West and her fellow researchers to fall in the near-infrared wavelength region--a region where human blood and tissue are relatively transparent.

West discussed a system for insulin delivery in which these tunable nanoshells are embedded into thermoresponsive polymers. The polymers form a capsulelike pod in which insulin (or another drug) can be contained. When light of the proper wavelength irradiates the polymer, however, the embedded nanoshells heat up and in turn activate the polymer, which causes it to collapse and release the insulin.

Nanoshells have also been used in West's lab to target and ablate cancer cells (C&EN, April 19, 2004, page 35). She noted that nanoshells can be designed to target cancerous cells through addition of antibodies and peptides to the shell.

Once targeted, the nanoshells bind to the tumors and, by applying the proper wavelength of light, heat up and destroy the tumor. West said damage done by this heating process is limited to 100 µm from the tumor surface. In related work, she is now developing a metastatic disease model to treat cancerous tumors.

Another area where nanotechnology is showing promise is in biomimics, namely biological implants such as joint replacements and artificial blood vessels. Thomas J. Webster, associate professor of biomedical engineering at Purdue University, explained that many of the current implants used today fail because of adverse tissue response. One problem, he noted, is that tissues have nanostructures, whereas implants are smooth at the nanoscale.

The goal of Webster's work is to develop surfaces that are similar to the tissue itself so that cells will adhere to them; that is, to develop implants that have structure at the nanoscale that is recognizable to cells. His work includes the use of nanofiber ceramics and carbon nanofibers.