Oxidized Porous Silicon Nanoparticles Covalent-Bonded with Levofloxacin in Hydrogel Polymer as a Drug Delivery System

Oxidized porous silicon (OPS) nanoparticles covalent-bonded with levofloxacin in hydrogel polymer are prepared and used to measure the efficiency for the controlled release drug delivery. Levofloxacin is covalently bonded to a Si–OH surface of OPS nanoparticles by catalytic condensation. The average size of these particles is about 100 nm. Since levofloxacin has a fluorescence property, the release of levofloxacin has been measured by fluorescence spectrometer. The quantity of levofloxacin release from the OPS nanoparticles is measured at the emission wavelength at 455 nm with an excitation wavelength of 330 nm on a time scale in pH 7 aqueous buffer solution. The analysis of release profile reveals that the OPS covalently bonded with levofloxacin (Levo-OPS) exhibits a great potential candidate for controlled release. The drug-release rate depends on the hydrolysis of silyl ester from the surface of OPS nanoparticles.

Analytical and Numerical Modelling of Liquid Penetration in a Closed Capillary

The chapter explores the dynamics of liquid penetration in a closed end vertical capillary. This model is very important for impedance spectroscopy methodology where oxidized porous silicon provides an in vitro medium, and one important criteria of this methodology is the liquid penetration depth inside the silicon pores as the impedance is greatly affected by this penetration depth. This problem is also important in order to understand how the presence of entrapped air inside a micro pore can influence the dynamics of capillary flow. For this purpose, the model is studied both analytically and numerically. In this study, different pore size (500 nm and 2 µm diameter) with equal pore depth (~10 µm) have been used. Finally, the analytical solution is compared with the numerical results. In addition, the linearization of the system is also investigated and found the critical viscosity of which demarcates the over-damped and under-damped regimes. Further, this study is extended by incorporating the dynamic contact angle effects on the meniscus dynamics.

Oxidized porous silicon as a non-interfering support for luminescent dyes

The objective of this work is to elucidate the possibility to passivate the surface states of porous Si (PSi) by thermal oxidation to be used as a passive host matrix. It is known that a large contribution to the Photoluminescence (PL) of PSi comes from defects at the surface. This PL could overlap the PL of guest materials making it difficult to identify the details of the PL spectrum of the guest. We report on an experimental study about the effect of thermal oxidation at low temperature on the PL of PSi and on the functionalization of oxidized PSi with fluorescein. The background PL is minimized allowing a better detection of fluorescein molecules adsorbed on oxidized PSi.