Our skin forms a protective barrier against things like extreme temperatures, toxins, microorganisms, radiation and mechanical force. But as skin ages, it becomes weaker, more sensitive and less able to repair itself. Aging also leads to things we don’t like, such as the formation of wrinkles or sagging skin.
Many people spend a lot of time and money restoring their skin’s youthful appearance, but what if there was an easier way? In a recently published study in Natural materialsA team of scientists has developed a synthetic skin that can be worn invisibly, restoring both the mechanical and aesthetic characteristics of normal, youthful skin.
Complex design criteria
While skin may seem like a simple organ, developing synthetic skin isn’t as easy as it sounds. The material should be formulated so that it spreads easily on the skin and then adheres to it. It must also be biocompatible to avoid skin irritation or sensitization. The synthetic skin must be breathable yet protect against the environment – and must not be toxic itself.
In addition, the synthetic material should have mechanical properties that accommodate the natural movement of the skin, as well as exhibit the skin’s typical properties of tension and elastic recoil. Finally, synthetic skin should look like healthy skin for different skin tones.
To meet these design criteria, the scientists built their artificial skin from a safe, biocompatible polysiloxane-based material, which can be fine-tuned to modulate properties such as strength, elasticity, flexibility, elongation, contractility, adhesion and permeability.
Material selection
The scientists carefully selected a safe chemistry that allowed them to easily deposit the cross-linked polymer layer onto the skin using a two-step delivery system. During the second delivery step, light-scattering particles are deposited on the surface of the cross-linked polymer layer to change its optical properties. This process ends with a cross-linked polymer layer that remarkably resembles youthful skin.
During the research, the team optimized the mechanical response by testing different network architectures. First, they examined the mechanical properties of normal skin. From these studies, they determined that the synthetic skin should have a tensile modulus between 0.5 and 1.95 MP and an elastic stretch area greater than 180 percent.
The scientists succeeded in creating a reactive polymer blend composition with a tensile modulus of 0.48 MPa, an elongation at break of 826 percent, an adhesive force of 78 N/mm and the correct elasticity. During the development of the final two-step delivery system to form the cross-linked polymer layer on sight, some inactive ingredients have been added to this candidate. For example, fumed silica (27 weight percent) was added to the reactive polymer blend to increase its mechanical toughness.
The skin’s elastic recoil is responsible for the skin’s ability to snap back into place after being pulled or stretched. Mechanical analysis revealed that the synthetic skin retained elastic recoil until fracture and had a tensile modulus similar to that of healthy skin.
The scientists also compared the synthetic skin to commercial products. This analysis showed that the new material had mechanical properties much closer to those of natural skin. In addition, the commercial offer was very visible compared to the newly developed material, which seems more or less invisible.
Human trials
The team then evaluated the synthetic skin’s performance when it overtook the real skin. At first, the team focused on the skin under the eyes because of the frequency of sagging, swollen skin there. They selected a combination of solvents and concentrations that would provide enough compression to shrink the skin with minimal discomfort.
The researchers were able to noticeably reduce the appearance of the bags within minutes as cross-linking of the polymer layer progressed; the effect lasted for several hours. This level of improvement had previously only been achieved through an invasive surgical procedure (called an “blepharoplasty”). In addition, they showed that the synthetic skin dramatically improved the elastic recoil of the skin after pulling.
Next, the researchers examined the influence of the synthetic skin on the elastic recoil of the forearm skin over an entire day and after removal. Forearm skins covered with synthetic material showed improved elasticity. The skin was even in better condition after the wear period, albeit to a lesser extent, suggesting that transient skin memory may develop in response to the 24-hour wear period.
In addition to these studies, the scientists evaluated the synthetic skin on dry leg skin to examine its effect on compromised barrier function. The studies showed that the synthetic skin acts as a protective barrier, preventing the skin from losing excessive amounts of moisture to the environment.
In a more complex study, the team examined the clinical performance of the synthetic skin in reshaping the lower eyelid through a double-blind, randomized, placebo-controlled trial. The placebo control consisted of adding the raw materials but not the catalyst needed to crosslink the polymer layer. Both blinded and trained graders noted significant improvements in skin quality after one hour and four hours of wear. Those treated with the placebo also showed some modest improvements compared to baseline, probably due to hydration caused by the polymer layer and possibly optical changes caused by the light-scattering particles. After four hours, the synthetic skin continued to outperform the placebo, with a smoother appearance and improved skin barrier.
The synthetic skin was assessed after periods of up to 16 hours. The synthetic material showed remarkable adhesion to the underlying skin and remained intact after activities such as running and swimming. Repeated daily wearing did not lead to adverse health effects.
This extensive study demonstrates the promise of this new synthetic skin. The tunability of the chemistry and formulation of this system allows the production of a platform of synthetic skins with potential utility for a variety of cosmetic and medical applications.
The scientists who developed this technology are spread across Living Proof Inc., Olivo Labs LLC, Massachusetts General Hospital, Harvard Medical School, and Massachusetts Institute of Technology. Living Proof Inc. and Olivo Labs LLC are cosmetic companies built on advanced technologies. All scientists in the study have a financial interest in both companies.
Natural materials2016. DOI 10.1038/NMAT4635 (About DOIs).