Implantable Silk Optics Dissolve, Triggering Tissue Regrowth in Their Wake

Posted by Brian Buntz on November 30, 2012

As one of the strongest-occurring natural materials, silk has long fascinated material scientists. The shimmering material has unique optical properties as well, thanks to the triangular prism-like structure of the fibers within it. Earlier this month, we covered the research conducted at Tufts University (Boston) and the CNRS Institut de Physiques de Rennes (France) that tapped the materials’ optical properties for implantable sensors. 

The researchers have recently released more information on their research on silk-based implantable optics, and have pointed to a number of new biomedical applications for them, including drug delivery and monitoring, and simultaneous tissue engineering and photothermal therapy. An article in PNAS titled “Implantable, multifunctional, bioresorbable optics” explains how the technology, upon dissolution, spurs regrowth of native tissue. 

The microscopic image of a silk optical implant shows embedded gold nanoparticles. Image courtesy of Fiorenzo Omenetto

The researchers created the optical devices by pouring purified silk protein solution into molds for microprism arrays. The speed at which the implants dissolve can be controlled by regulating the water content of the protein solution. Upon drying, the solution dries and forms a material resembling reflective tape.

The researchers experimented with embedding the material with gold nanoparticles. (See image on the left.) When implanted in mice, these implants were illuminated with green laser light, thus heating the implants for use in thermal therapy to combat bacterial infections of destroy malignant cells. At the same time, the implant's optical properties enabled the scientists to monitor the process. 

The researchers also experimented with embedding the material with the cancer drug doxorubicin. The drug remained stabile even when the material was heated to 60° C.

Brian Buntz is the editor-at-large at UBM Canon's medical group. Follow him on Twitter at @brian_buntz.