Bioresorbable fibers for time-domain diffuse optical measurements: A step toward next generation optical implantable devices

The use of bioresorbable fibers represents an innovative way to build optical implantable devices and to look inside the body. Recently, a new kind of bioresorbable fibers, based on calcium-phosphate glasses, has been introduced by some of us. They show a good biocompatibility and improved attenuation loss coefficient with respect to other bioresorbable fibers. In this work, we used those fibers to explore their suitability in diffuse optics. Indeed, the time-domain technique is a non-invasive methodology which allows to have an absolute estimate of the absorption and reduced scattering spectra of the diffusive medium. It allows to bring information about concentration of chemical components (water, oxyand deoxy-hemoglobin), thus conveying information about the functional status and/or the scattering properties (changes in tissue microstructure, edema). Such information can then be related to the tissue regeneration, healing process, or to a harmful evolution. This makes the time domain optical spectroscopy coupled to bioresorbable fibers a good candidate for future medical devices. Here we demonstrate the suitability of these fibers for diffuse optics by means of standardized tests and then we use them for a proof-of-principle measurement on ex-vivo chicken breast, obtaining results comparable with standard fibers. Thanks to the encouraging results, we are working on a system based on a single fiber (serving as both injection and collection fiber) to go closer to a single interstitial fiber which can lessen the effect of the implant.