UC San Diego

By leveraging its structural, chemical and photonic properties, porous silicon materials were employed to develop platform drug delivery, theranostic and sensing systems. For drug delivery applications, oxidative and magnesium/calcium trapping strategies were investigated to physically immobilize small molecule and protein payloads within the silicon skeleton. The trapping chemistry utilized the pore volume of porous silicon for hosting payload so that high loading efficiency and near 0-order release kinetics was achieved. This strategy also alters the mechanism of payload release from diffusion to particle degradation and substantially minimizes or eliminates burst release. The intrinsic luminescence of silicon was employed as a self-reporting tool for real-time monitoring of payload release from the skeleton and activated by either thermal oxidation or aqueous aging. Correlations between pharmacokinetics and luminescence decay were demonstrated in both in vivo and in vitro studies for intraocular delivery applications.

Polymer-silicon composite photonic crystals were investigated for sensing applications by utilizing the change in structural color as a signal output. The molecular weight dependence on polymer melt infiltration into porous silicon templates enabled fabrication of free-standing polymer photonic crystals with different porosities and optical signatures. Porous silicon films were embedded into polymer catheter devices as sterilization sensors using simple manufacturing methods. Bacteria testing revealed that by wiping the tip of the catheter hub with an alcohol swab and upon observing a complete color change from green to red (and back to green) the catheter device was sterile and confirmed the sensing ability of the porous silicon film.