Biocompatible silica-gelatin hybrid aerogels covalently labeled with fluorescein

Silica-gelatin hybrid aerogels, introduced recently as drug delivery devices, were investigated for biocompatibility with SCC tumor cells by a time-lapse video-microscopy technique. The particles proved to be not only nontoxic in nature, but the cells migrated towards them. Fluorescently labeled hybrid aerogels were synthesized by covalently binding fluorescein isothiocyanate either to the amino groups of gelatin molecules, or to the amine-functionalized silica backbone prior to sol-gel polycondensation and co-gelation steps. Scanning electron microscopy and fluorescence spectroscopy characterization of pristine and labeled aerogels showed identical structures and spectra, while fluorescence lifetimes were 10% shorter than that of the free fluorescein, due to covalent attachment. Migration plots based on time-lapse video recordings showed that the cells exhibited a directive migration nearby the aerogel particles. No signs of apoptosis or necrosis were observed at any phases of the cell cycle in the presence of the silica-gelatin aerogel particles, indicating that the hybrid aerogels are biocompatible materials, and may be used as drug delivery matrices in living organisms.