Large area etching for porous semiconductors

Nanostructured porous silicon-mediated drug delivery

INTRODUCTION

The particular properties of nanostructured porous silicon (nanoPS) make it an attractive material for controlled and localized release of therapeutics within the body, aiming at increased efficacy and reduced risks of potential side effects. Since this is a rapidly evolving field as a consequence of the number of research groups involved, a critical review of the state of the art is necessary.

AREAS COVERED

In this work, the most promising and successful applications of nanoPS in the field of drug delivery are reviewed and discussed. Two key issues such as drug loading and release are also analyzed in detail. The development of multifunctional (hybrid) systems, aiming at imparting additional functionalities to the nanoPS particles such as luminescence, magnetic response and/or plasmonic effects (allowing simultaneous tracking and guiding), is also examined.

EXPERT OPINION

Nanostructured materials based on silicon are promising platforms for pharmaceutical applications given their ability to degrade and low toxicity. However, a very limited number of clinical applications have been demonstrated so far.

Macroporous Semiconductors

Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed.

Porous silicon protein microarray technology and ultra-/superhydrophobic states for improved bioanalytical readout

One attractive method for monitoring biomolecular interactions in a highly parallel fashion is the use of microarrays. Protein microarray technology is an emerging and promising tool for protein analysis, which ultimately may have a large impact in clinical diagnostics, drug discovery studies and basic protein research. This chapter is based upon several original papers presenting our effort in the development of new protein microarray chip technology. The work describes a novel 3D surface/platform for protein characterization based on porous silicon. The simple adjustment of pore morphology and geometry offers a convenient way to control wetting behavior of the microarray substrates. In this chapter, an interesting insight into the surface role in bioassays performance is made. The up-scaled fabrication of the novel porous chips is demonstrated and stability of the developed supports as well as the fluorescent bioassay reproducibility and data quality issues are addressed. We also describe the efforts made by our group to link protein microarrays to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), suggesting porous silicon as a convenient platform for fast on-surface protein digestion protocols linked to MS-readout. The fabrication of ultra- and superhydrophobic states on porous silicon is also described and the utilization of these water-repellent properties for a new microscaled approach to superhydrophobic MALDI-TOF MS target anchor chip is covered.