Called a light-guiding hydrogel, the implant is constructed from a polymer-based scaffolding capable of supporting living cells and contains cells genetically engineered either to carry out a specific activity in response to light or to emit light in response to a particular metabolic signal. An optical fiber connects the implant to either an external light source or a light detector.
The investigators first determined the properties of the hydrogel scaffolding - including transparency, flexibility and stability - that would be most appropriate for delivering or detecting a light signal. After determining how many cells could be implanted into the hydrogel without significantly reducing its ability to transmit a light signal, they developed and tested in mice two different systems, both involving implantation of a 4-centimeter hydrogel beneath the animal's skin.
The first system's implants contained cells genetically engineered to express light-emitting green fluorescent protein (GFP) upon contact with a toxin. After confirming in vitro the hydrogels' response to nanoparticles containing the toxic metal cadmium, the researchers implanted the hydrogels beneath the skin of three groups of mice. One group was then injected with the cadmium nanoparticles, the second received nanoparticles encased in a polymer shell that shielded cells from the toxin, and the third received a control saline injection. The implants only produced a GFP-signal in response to the unshielded nanoparticles, indicating their ability to sense a change - in this instance the presence of a toxin - in the cellular environment.
To investigate a possible therapeutic application for the system, the investigators used a hydrogel implant containing cells that respond to blue light by producing glucagon-like peptide-1 (GLP-1), a protein playing an essential role in glucose metabolism. After the implants were placed under the skin of mice with diabetes, the blue light signal was delivered for 12 hours. A day and a half later - 48 hours after the implant - the animals that received the light signal had double the level of GLP-1 in their blood, along with significantly better results in a glucose tolerance test, than did implanted mice not treated with light.
"This work combines several existing technologies well known in their respective fields - such as drug delivery, genetic engineering, biomaterial science, and photonics - to build a new implant system that enables the delivery of photomedicine deep in the body," says Yun, an associate professor of Dermatology at
The researchers add that future studies should investigate how changing the shape and structure of the hydrogel can improve the implant's light-guiding properties, ways to improve the production and delivery of a therapeutic protein, how the immune system would react to long-term implantation and ways to deliver or detect the light signal that would not require passing a fiber through the skin.
Keywords for this news article include: Therapy, Engineering, Nanotechnology, Emerging Technologies,
Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2013, NewsRx LLC
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