New Material Aids Facial Skin Reconstruction

An injectable composite of biological and synthetic molecules shows promise in restoring damaged soft tissue relatively safely and durably.

Researchers at Johns Hopkins University (Baltimore, MD, USA) created the new composite material from hyaluronic acid (HA), a natural component in skin of young people that confers elasticity, and polyethylene glycol (PEG), a synthetic molecule used successfully as surgical glue in operations and known not to cause severe immune reactions. The PEG can be cross-linked-- forming sturdy chemical bonds between many individual molecules--using energy from light, which traps the HA molecules with it. Such cross-linking makes the implant hold its shape and not dissipate away from the injection site.

To develop the best PEG-HA composite with the highest long-term stability, the researchers injected different concentrations of PEG and HA under the skin and into the back muscle of rats, used a green light emitting diode (LED) light to gel the material, and then used magnetic resonance imaging (MRI) to monitor the persistence of the implant over time. The MRIs and direct measurements of the implants showed that the ones created from HA and the highest tested concentration of PEG with HA remained the same size over time, compared to injections of only HA, which shrank over time.

The researchers also evaluated the safety and persistence of the PEG-HA implants in three volunteers undergoing abdominoplasty. Technicians injected about five drops of PEG-HA or HA alone under the belly skin. The participants said they sensed heat and pain during the gel setting process; 12 weeks after implantation, MRI revealed no loss of implant size in patients. Removal of the implants and inspection of the surrounding tissue revealed mild to moderate inflammation, a response similar to that seen in the rats, although the types of white blood cells (WBCs) responding to implant differed between the rodents and humans. The difference was attributed to the fact that the target tissue in the rats (muscle) was different than human belly fat. The study was published in the July 27, 2011, issue of Science Translational Medicine.

“Implanted biological materials can mimic the texture of soft tissue, but are usually broken down by the body too fast, while synthetic materials tend to be more permanent but can be rejected by the immune system and typically don’t meld well with surrounding natural tissue,” said lead author Prof. Jennifer Elisseeff, MD, PhD, director of the Translational Tissue Engineering Center at JHU School of Medicine. “Our composite material has the best of both worlds, with the biological component enhancing compatibility with the body and the synthetic component contributing to durability.”

“Many of the skin fillers available on the market consisting of HA-like materials used for face lifts are only temporarily effective, and are limited in their ability to resculpt entire areas of the face,” added Professor Elisseeff. “Our hope is to develop a more effective product for people, like our war veterans, who need extensive facial reconstruction.”

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