MIT scientists and associates have developed a new material that can temporarily protect and tighten skin, and smooth wrinkles. With further development, it could also be used to deliver drugs to help treat skin conditions such as eczema.
The material is a silicone-based polymer that could be applied on the skin as a thin, imperceptible coating, mimicking the mechanical and elastic properties of healthy, youthful skin.
In tests with human subjects, the researchers found that the material was able to reshape “eye bags” under the lower eyelids and also enhance skin hydration (moisturizing, or preventing the skin from dying out). This type of “second skin” could also be adapted to provide long-lasting ultraviolet protection, the researchers say.
As skin ages, it becomes less firm and less elastic — problems that can be exacerbated by sun exposure. This process impairs skin’s ability to protect against extreme temperatures, toxins, microorganisms, radiation, and injury. About 10 years ago, the MIT-headed research team set out to develop a protective coating that could restore the properties of healthy skin, for both medical and cosmetic applications.
The idea was to control the properties of skin by coating it with polymers that would impart beneficial effects, while making the coating invisible and comfortable.
“It has to have the right optical properties, otherwise it won’t look good, and it has to have the right mechanical properties, otherwise it won’t have the right strength and it won’t perform correctly,” says Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute. Langer is the senior author of a paper describing the polymer in the May 9 online issue of Nature Materials.
The researchers created a library of more than 100 possible polymers with the chemical structure known as siloxane — a chain of alternating atoms of silicon and oxygen. These polymers can be assembled into a network arrangement known as a cross-linked polymer layer (XPL).
The researchers then tested the materials in search of one that would best mimic the appearance, strength, and elasticity of healthy skin.
The best-performing material they found has elastic properties very similar to those of human skin. In laboratory tests, it easily returned to its original state after being stretched more than 250 percent (natural skin can be elongated about 180 percent). In laboratory tests, the novel XPL’s elasticity was much better than that of two other types of wound dressings now used on skin — silicone gel sheets and polyurethane films.
In the paper, researchers describe studies performed on humans to test the material’s effectiveness in terms of wearability, prevention of water loss, and safety. In wearability, the XPL material outperformed two commercial wound dressings with respect to flexibility, elasticity, thickness and visibility. In moisturization (hydration) and water loss, XPL exhibited statistically less water loss and more skin-hydration than high-end commercial moisturizers. Additionally, no skin irritation was observed in these tests.
The XPL is currently delivered in a two-step process. First, polysiloxane components are applied to the skin, followed by a platinum catalyst that induces the polymer to form a strong cross-linked film that remains on the skin for up to 24 hours. This catalyst has to be added after the polymer is applied because after this step the material becomes too stiff to spread. Both layers are applied as creams or ointments, and once spread onto the skin, XPL becomes essentially invisible.*
MIT | Engineering a second skin
The new material was developed at MIT spinoff Living Proof, which has now spun out the XPL technology to Olivo Laboratories, LLC. Initially, Olivo’s team will focus on medical applications of the technology for treating skin conditions such as dermatitis.
“This ‘skin conforming’ platform brings with it transport properties that have significant promise to treat underlying conditions,” said Dr. Rox Anderson, Harvard Professor, Olivo co-founder, and Dermatologist at Massachusetts General Hospital, where researchers were also involved in the research. “For eczema or sun protection as examples, this second skin platform can then serve as a reservoir for control-release transdermal drug delivery or SPF ingredients, a possibility we are currently pursuing in our lab.”
A beauty business based on MIT bioengineering
Living Proof, a hair care company with roots in research emerging from the Langer Lab at MIT, has won 80 awards and counting and retails in 33 countries plus Hong Kong.
Fronted by celebrity spokesperson and co-owner Jennifer Aniston, Living Proof has formulated hair products that capitalize on the properties of octaflouropentyl methacrylate, or OFPMA, which is both hydrophobic and lipophobic (repels both water and fat). “It lays down on the surface and changes how moisture moves in and out of the fiber,” Spengler explains. “That has a profound influence on the quality of hair.”
The researchers have also discovered poly beta-amino ester (PBAE), which deposits a flexible pattern of thickening points that create space between each hair strand, making fine hair feel fuller.
* The researchers performed several studies in humans to test the material’s safety and effectiveness. In one study, the XPL was applied to the under-eye area where “eye bags” often form as skin ages. These eye bags are caused by protrusion of the fat pad underlying the skin of the lower lid. When the material was applied, it applied a steady compressive force that tightened the skin, an effect that lasted for about 24 hours.
In another study, the XPL was applied to forearm skin to test its elasticity. When the XPL-treated skin was distended with a suction cup, it returned to its original position faster than untreated skin.
The researchers also tested the material’s ability to prevent water loss from dry skin. Two hours after application, skin treated with the novel XPL suffered much less water loss than skin treated with a high-end commercial moisturizer. Skin coated with petrolatum was as effective as XPL in tests done two hours after treatment, but after 24 hours, skin treated with XPL had retained much more water. None of the study participants reported any irritation from wearing XPL.
Abstract of An elastic second skin
We report the synthesis and application of an elastic, wearable crosslinked polymer layer (XPL) that mimics the properties of normal, youthful skin. XPL is made of a tunable polysiloxane-based material that can be engineered with specific elasticity, contractility, adhesion, tensile strength and occlusivity. XPL can be topically applied, rapidly curing at the skin interface without the need for heat- or light-mediated activation. In a pilot human study, we examined the performance of a prototype XPL that has a tensile modulus matching normal skin responses at low strain (<40%), and that withstands elongations exceeding 250%, elastically recoiling with minimal strain-energy loss on repeated deformation. The application of XPL to the herniated lower eyelid fat pads of 12 subjects resulted in an average 2-grade decrease in herniation appearance in a 5-point severity scale. The XPL platform may offer advanced solutions to compromised skin barrier function, pharmaceutical delivery and wound dressings.