Unique Polymer Degrades Under Low-Level Near Infrared Irradiation

Scientists at the University of California, San Diego (UCSD), have reported a unique polymeric material that disassembles when exposed to low levels of near infrared (NIR) irradiation, is well-tolerated by cells, and could be used for in vivo medical and biological applications.

“To the best of our knowledge, this is the only polymeric material specifically designed to break down [into] small fragments in response to very low levels of NIR irradiation,” said research team leader Adah Almutairi in a statement from the university. In addition, “we think there is great potential for use in human patients, allowing previously inaccessible targets sites to be reached for both treatment and diagnosis,” she said.

The Geisel Library at UCSD.

NIR irradiation penetrates up to 10 cm deep into tissues with more precision and less damage, absorption, and scattering in comparison with visible light. Though a few materials could respond to high-level NIR irradiation, no material has responded to low-level NIR irradiation, according to the statement.

The milestone research also indicates that cells can tolerate both the polymer and its breakdown products. Biomaterials that were previously developed were difficult to clear out of the body.

The new biomaterial is considered a “smart” polymer because it responds when its environment changes. Scientists and engineers envision using them for applications including tissue engineering, wound-healing, drug delivery, and biosensors.

The researchers reported in a journal article how this smart polymer works:

The design relies on the photolysis of the multiple pendant 4-bromo7-hydroxycoumarin protecting groups to trigger a cascade of cyclization and rearrangement reactions leading to the degradation of the polymer backbone.

The UCSD researchers are currently working on synthetic and engineering strategies to create biomaterials that are even more sensitive to NIR irradiation.

Source: “New Polymeric Material Developed at UC San Diego Has Potential for Use in Non-Invasive Surgical Procedures,” UCSD press release, 10/3/11
Source: “Low Power, Biologically Benign NIR Light Triggers Polymer Disassembly,” Macromolecules, 9/30/11
Image by kafka4prez, used under its Creative Commons license.

Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.