Offering mild, non-invasive and deep cancer therapy modality, radio frequency (RF) radiation-induced hyperthermia lacks for efficient biodegradable RF sensitizers to selectively target cancer cells and thus avoid side effects. Here, we assess crystalline silicon (Si) based nanomaterials as sensitizers for the RF-induced therapy. Using nanoparticles produced by mechanical grinding of porous silicon and ultraclean laser- ablative synthesis, we report efficient RF-induced heating of aqueous suspensions of the nanoparticles to temperatures above 45-50 degrees C under relatively low nanoparticle concentrations (< 1 mg/mL) and RF radiation intensities (1-5 W/cm(2)). For both types of nanoparticles the heating rate was linearly dependent on nanoparticle concentration, while laser-ablated nanoparticles demonstrated a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations from 0.01 to 0.4 mg/mL. The observed effect is explained by the Joule heating due to the generation of electrical currents at the nanoparticle/water interface. Profiting from the nanoparticle-based hyperthermia, we demonstrate an efficient treatment of Lewis lung carcinomain in vivo. Combined with the possibility of involvement of parallel imaging and treatment channels based on unique optical properties of Si-based nanomaterials, the proposed method promises a new landmark in the development of new modalities for mild cancer therapy.

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Radio frequency radiation-induced hyperthermia using Si nanoparticle-based sensitizers for mild cancer therapy

Recent developments in the field of silicon nanostructures, particularly those properties and phenomena that are related to the photoluminescence (PL) from silicon nanostructures, have attracted much attention lately. A major source of controversy and disagreement among researchers is the underlying mechanism behind the PL. Two classes of models, i.e., the quantum confinement model that assigns the PL to quantum size effects in the nanocrystalline silicon core of the nanostructures and the surface chemistry model that assign the PL to surface phenomena at the interface between the crystalline core and the host matrix that wrap the nanostructures, are the most notable ones. In recent years, alternative structures to porous silicon, which allow synthesizing high quality silicon nanostructures with better control of their dimensionality, shape and size distribution, have emerged. In particular, fabrication techniques of silicon nanocrystals embedded in silicon-dioxide (SiO2) matrices have reached a level where consistent investigation of surface and quantum size phenomena can be performed. Recent experimental results and theories suggest that none of the above models alone can explain the entire spectrum of optical phenomena in silicon nanostructures. Instead, a refined model that takes into account the mutual role of quantum confinement and surface chemistry in shaping the optical properties of these nanostructures should be considered.

Photoluminescence from silicon nanostructures: The mutual role of quantum confinement and surface chemistry

By adapting microfabrication techniques originally developed in the microelectronics industry novel devices for drug delivery, tissue engineering and biosensing have been engineered for in vivo use. Implant microfabrication uses a broad range of techniques including photolithography, and micromachining to create devices with features ranging from 0.1 to hundreds of microns with high aspect ratios and precise features. Microfabrication offers device feature scale that is relevant to the tissues and cells to which they are applied, as well as offering ease of en masse fabrication, small device size, and facile incorporation of integrated circuit technology. Utilizing these methods, drug delivery applications have been developed for in vivo use through many delivery routes including intravenous, oral, and transdermal. Additionally, novel microfabricated tissue engineering approaches propose therapies for the cardiovascular, orthopedic, and ocular systems, among others. Biosensing devices have been designed to detect a variety of analytes and conditions in vivo through both enzymatic-electrochemical reactions and sensor displacement through mechanical loading. Overall, the impact of microfabricated devices has had an impact over a broad range of therapies and tissues. This review addresses many of these devices and highlights their fabrication as well as discusses materials relevant to microfabrication techniques.

E. Florentin

Papers

Optical properties of porous silicon surface