Steven M. Serkiz

Porous-wall hollow glass microspheres as novel potential nanocarriers for biomedical applications

UNLABELLED Porous-wall hollow glass microspheres (PW-HGMs) are a novel form of glass material consisting of a 10- to 100-microm-diameter hollow central cavity surrounded by a 1-microm-thick silica shell. A tortuous network of nanometer-scale channels completely penetrates the shell. We show here that these channels promote size-dependent uptake and controlled release of biological molecules in the 3- to 8-nm range, including antibodies and a modified single-chain antibody variable fragment. In addition, a 6-nm (70-kDa) dextran can be used to gate the porous walls, facilitating controlled release of an internalized short interfering RNA. PW-HGMs remained in place after mouse intratumoral injection, suggesting a possible application for the delivery of anticancer drugs. The combination of a hollow central cavity that can carry soluble therapeutic agents with mesoporous walls for controlled release is a unique characteristic that distinguishes PW-HGMs from other glass materials for biomedical applications. FROM THE CLINICAL EDITOR Porous-wall hollow glass microspheres (PW-HGMs) are a novel form of glass microparticles with a tortuous network of nanometer-scale channels. These channels allow size-dependent uptake and controlled release of biological molecules including antibodies and single-chain antibody fragments. PW-HGMs remained in place after mouse intratumoral injection, suggesting a possible application for the delivery of anti-cancer drugs.

Ultra-Sensitive Duffing Behavior of a Microcantilever

We investigate the properties of an electrostatically driven microcantilever exhibiting duffing-like behavior using harmonic detection of resonance. Its potential use as a highly sensitive sensing platform is discussed. We find high sensitivity of this duffing system near its bistability point in a gaseous environment. The response of the higher harmonics of the measured charge on the cantilever induced by an ac voltage that drives the counter electrode is investigated. In particular, we follow the duffing behavior at the higher harmonics (up to the sixth harmonic) as a function of gap distance between the cantilever and counter electrode. To our knowledge, this work represents the first experimental demonstration of sensing a pressure change using the duffing behavior.

Harmonic detection of resonance method

Electromechanical resonators in the micro (MEMS) and nano (NEMS) regimes have emerged as promising tools for use in diverse applications such as ultrasensitive physical, chemical, and biological sensors, with detection limits as low as a single molecule. The advent of state-of-the-art micro-fabrication techniques has enabled a high throughput platform for commercialization. However, the sensitivity and reliability of such devices are highly dependent on the employed detection technique. We present a highly useful yet simple electrical detection scheme: the Harmonic Detection of Resonance (HDR) method. The prominent HDR features will be discussed and applications ranging from the use of micro-cantilevers as sensors to probing mechanical properties in nano-cantilever systems will be presented.

Ringdown sensing method

Miniaturization of devices into lab-on-chip designs is a dominating field of current scientific research. While the technology to build these devices is continuing to develop, the practical realization of such devices remain elusive, mainly due to lack of techniques that bridge the macroscopic world to the mechanical motion and/or the electronic signals generated on the micro- or nano-sized scale. Hence, there is an increasing need for sensitive detection techniques that can not only be implemented on such small scale systems but also be integrated with the current CMOS technology. In this regard, a fully electrical microcantilever-based ringdown method will be presented. We show that detection technique can be employed to precisely analyze the composition of gas mixtures. The viscosity and density can be measured simultaneously, which is illustrated for multiple gases yielding viscosities within ± 2% and densities within ± 6% of NIST values.