Engineering the Chemistry and Nanostructure of Porous Silicon Fabry-Pérot Films for Loading and Release of a Steroid

Abstract

A method for engineering the surface chemistry and pore dimensions in porous Si films for the purpose of controlling the loading and release of a hydrophobic drug is described. Loading of the steroid dexamethasone is confirmed by Fourier transform infrared spectroscopy, and the release rates are characterized by observation of the appearance of the drug in solution (UV-vis absorption spectroscopy) and by measurement of the Fabry-Perot fringes in the optical reflectivity spectrum of the porous Si film. Optical reflectivity changes provide a measure of the release rate of the drug that is amenable to in-vivo diagnostic applications. Fresh porous Si films are prepared by electrochemical etch and subsequently modified by hydrosilylation with 1-dodecene. The dodecene-modified samples are more robust in aqueous environments and exhibit slower release rates of the drug relative to freshly etched porous Si. Whereas the relatively large dexamethasone molecule is found to infiltrate the freshly etched samples, it does not enter the chemically modified films, because of steric crowding from the dodecyl species. To achieve a high degree of loading into these modified films, the pores are enlarged before hydrosilylation by treatment with an aqueous solution containing HF and dimethyl sulfoxide. The pore expanded, chemically modified samples admit approximately 70% of the dexamethasone that can be admitted into an unmodified (freshly etched) sample. Diffusion of the steroid from the modified, pore expanded films into phosphate-buffered saline solution is slower than from the unmodified sample by a factor of approximately 20, with 90% of the drug delivered in 3 days for the chemically modified films compared to 3 h for the unmodified films.

Biosensing Using Porous Silicon Double-Layer Interferometers: Reflective Interferometric Fourier Transform Spectroscopy

“…The value of 2nL can be obtained directly as the position of the peak in the FFT. 26 Thus the "singlelayer 1" film in air displays a spectral interference pattern (Fig. 3) whose FFT yields a peak at 6950 nm ( Fig.…”

Protein delivery based on uncoated and chitosan-coated mesoporous silicon microparticles

“…Better known in microelectronics, nanostructured semiconductors have been recently recognized to bear great promise for biomedical purposes such as tissue engineering [1], medical diagnosis [2], and drug delivery [3,4]. One of the most interesting features of porous silicon is its longterm stability at low pH (<6.0) [5] and the high hydrophobic nature of its native surface that can be extremely advantageous for the adsorption and delivery of small hydrophobic molecules such as doxorubicin [6], dexamethasone [7] or porphyrins [8]. Although the biocompatibility status of mesoporous silicon is still under investigation, it is known that the bulk material has negligible cytotoxicity [9].…”

Controlled Drug Delivery From Composites of Nanostructured Porous Silicon and Poly( L -Lactide)

“…Also, in contrast to most polymeric materials, the surface chemistry of pSi can be modified by simple onestep chemical treatments without affecting its material properties. Surface modification allows tuning of the loading and release characteristics of a wide range of bioactives [27][28][29][30]. Depending on the chemical doping of the Si material base, etching conditions and surface modification [31][32][33], the degradation kinetics can be controlled from hours to months.…”