ChemCafé

Biocompatible polymers are avidely sought for owing to their frequent use in reconstructive sugery and as prostheses. One of the challenges is to make implants that are easy to inserate, minimizing scarring and recovery time.

A team led by Prof. Jennifer Helisseeff at Johns Hopkins University recently presented a novel implant, that can be injected as a liquid under the skin, then modeled to appropriate shape, and solidified by exposure to light. The composite material is made by mixing polyethylene glycol (PEG), a widely used artificial polymer, with hyaluronic acid, a natural polysaccharide. The ratio of PEG and hyaluronic acid can be tuned, such as to modulate the properties of the final polymer: it can then be adapted to the location where the injection takes place (fat, muscle, skin). After injection under the skin (tests were made on rodents and with human patients), the implants could be massaged into shape. Finally, exposure to visible light initiated a cross-linking reaction between the PEG molecules, transforming the implant into a solid, shape-persistent hydrogel with entrapped hyaluronic acid molecules.

Although the newly-develped implants possess good longevity and stability, it was found that they cause more inflammation than currently used implants. However, the presented technique will probably find numerous application in reconstructive surgery, as soon as the last problems will have been sorted out.

The liquid polymer is injected, and solidified by irradiation.

Reference: A. T. Hillel et al., Sci. Trans. Med. 2011, 3, 93ra67. DOI: 10.1126/scitranslmed.3002331