Scientists at the University of California, San Diego Skaggs School Pharmacy and Pharmaceutical Sciences report development and successful initial testing of the first practical “smart” material to use a form of light that can penetrate four inches into the human body, for use in diagnosing diseases and engineering new human tissues in the lab.

They used near-infrared (NIR) light (just beyond what humans can see), which penetrates through the skin and almost four inches into the body. Low-power NIR does not damage body tissues. However, current NIR-responsive smart materials require high-power NIR light, which could damage cells and tissues.

So they developed a new smart polymer (plastic). Hit with low-power NIR, the material breaks apart into small pieces that appear to be nontoxic to surrounding tissue. They could put the polymer in an implantable hydrogel, which is a water-containing flexible material used for tissue engineering and drug delivery. A hydrogel with the new polymer could release medications or imaging agents when hit with NIR. “To the best of our knowledge, this is the first example of a polymeric material capable of disassembly into small molecules in response to harmless levels of irradiation,” say the researchers.

Ref.: Nadezda Fomina, et al., Low Power, Biologically Benign NIR Light Triggers Polymer Disassembly, Macromolecules, 2011; 44 (21): 8590 [DOI: 10.1021/ma201850q]