Scientists are reporting development and successful initial testing of the first practical \"smart\" material that may supply the missing link in efforts to use in medicine a form of light that can penetrate four inches into the human body.Their report on the new polymer or plastic-like material, which has potential for use in diagnosing diseases and engineer new human tissues in the lab, appears in ACS\' journal Macromolecules.Adah Almutairi and colleagues explain that near-infrared (NIR) light (which is just beyond what human can see) penetrates through the skin and almost four inches into the body, with great potential for diagnosing and treating diseases. Low-power NIR does not damage body tissues as it passes. Missing, however, are materials that respond effectively to low-power NIR.Plastics that disintegrate when hit with NIR, for instance, could be filled with anti-cancer medicine, injected into tumors, and release the medicine when hit with NIR. Current NIR-responsive smart materials require high-power NIR light, which could damage cells and tissues. That\'s why Almutairi\'s team began research on development of a new smart polymer that responds to low-power NIR light. Hit with low-power NIR, their new material breaks apart into small pieces that seem to be nontoxic to surrounding tissue. The researchers envision, for instance, putting 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.