Research ArticleTissue Engineering

Photoactivated Composite Biomaterial for Soft Tissue Restoration in Rodents and in Humans

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Science Translational Medicine  27 Jul 2011:
Vol. 3, Issue 93, pp. 93ra67
DOI: 10.1126/scitranslmed.3002331

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Photogenic Polymers Can Fix the Flaws

Some people just love the spotlight; apparently, some polymers do too. Here, Hillel et al. introduce a class of composite polymers that react favorably to light by crosslinking within minutes. These polymers, composed of synthetic poly(ethylene glycol) (PEG) and natural hyaluronic acid (HA), have been developed for reconstructing facial soft tissue. Deformities in craniofacial soft tissue are a clinical challenge because even small defects can have a major impact on a person’s social behavior and psychological well-being.

Hillel and colleagues created a polymeric composite that can be injected into the damaged site, massaged into shape, and then crosslinked in situ with light. A transdermal light exposure method would allow clinicians to inject a liquid polymer, rather than surgically inserting already-polymerized material. First, the authors designed an array of light-emitting diodes to penetrate up to 4 mm of human skin (both light and dark) without any painful side effects. A 2-min exposure to light was enough to crosslink the PEG-HA material under the skin. Next, the polymer was tailored to closely match the elastic properties of native soft tissues, such as human fat. Various amounts of PEG and concentrations of HA were tested, with the authors arriving at an optimal combination of 100 mg PEG and 24 mg/ml HA. When polymerized subcutaneously in rats, the PEG-HA implants were able to maintain near their original volume for up to 491 days, whereas control HA injections were completely resorbed. Notably, these HA-based materials were partially reversible with the addition of the enzyme hyaluronidase.

To translate this material to the clinic, Hillel et al. then tested the PEG-HA composites in humans. The polymer was injected into the intradermal space in the abdomen of three patients scheduled to undergo abdominoplasty surgery. Similar to the rodent studies, the PEG-HA material persisted for 12 weeks, whereas the control HA injections lost their shape. An inflammatory response was observed surrounding the injections. It is clear that this new photo-friendly polymer and transdermal crosslinking method will be clinically useful for soft tissue reconstruction—perhaps even encouraging more people to put their best faces forward in the spotlight.


  • * These authors contributed equally to this work.

  • Citation: A. T. Hillel, S. Unterman, Z. Nahas, B. Reid, J. M. Coburn, J. Axelman, J. J. Chae, Q. Guo, R. Trow, A. Thomas, Z. Hou, S. Lichtsteiner, D. Sutton, C. Matheson, P. Walker, N. David, S. Mori, J. M. Taube, J. H. Elisseeff, Photoactivated Composite Biomaterial for Soft Tissue Restoration in Rodents and in Humans. Sci. Transl. Med. 3, 93ra67 (2011).

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