Sol-gel coatings for fiberoptics appliances

Porous materials like sol-gel derived silica may have applications for biomedical purposes. We examined the spectroscopic features of sol-gel films placed on fiber cores, replacing the original fiber coatings. Such modification of optical fibers may be exploited for construction of fiberoptics sensors or applicators for interstitial laser therapy. Our coatings were prepared from silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The matrices were produced with various ratios R=5, 15, 20, 32, 40, 50, whereas R denotes the number of solvent moles (here ethanol) to the number of TEOS moles. Two types of coatings were examined: pure sol-gel matrices and sol-gel doped with photosensitive dyes as used for photodynamic therapy. It was demonstrated that PDT photosensitive agents immobilized in sol-gels have contact with external environment, thus showing the clear response to changes of environment. The application of the results for fiberoptic sensing and construction of applicators for enhanced interstitial laser therapy is discussed.