Towards pain-free diagnosis of skin diseases through multiplexed microneedles: biomarker extraction and detection using a highly sensitive blotting method

Immunodiagnostic microneedles provide a novel way to extract protein biomarkers from the skin in a minimally invasive manner for analysis in vitro. The technology could overcome challenges in biomarker analysis specifically in solid tissue, which currently often involves invasive biopsies. This study describes the development of a multiplex immunodiagnostic device incorporating mechanisms to detect multiple antigens simultaneously, as well as internal assay controls for result validation. A novel detection method is also proposed. It enables signal detection specifically at microneedle tips and therefore may aid the construction of depth profiles of skin biomarkers. The detection method can be coupled with computerised densitometry for signal quantitation. The antigen specificity, sensitivity and functional stability of the device were assessed against a number of model biomarkers. Detection and analysis of endogenous antigens (interleukins 1α and 6) from the skin using the device was demonstrated. The results were verified using conventional enzyme-linked immunosorbent assays. The detection limit of the microneedle device, at ≤10 pg/mL, was at least comparable to conventional plate-based solid-phase enzyme immunoassays

Glass microchannel technology for capillary electrophoresis

The fabrication process of glass chips for capillary elect rophoresis by means of micromachining is reported. The device is made up of two glass substrates joined by means of thermal fusion bonding. Selective wet etchings were used to define Five microchannels, four for samples injection and one for the separation, while the access holes were obtained with diamond drills. The fabrication process required only one photolithographic step and the thermal fusion bonding did not reduce the uniformity and integrity of the channels. Good results in terms of microchannels shape definition, repeatability and glass surface quality have been obtained

Pushing the limit of the silicon technology by using porous silicon: a CMOS gas sensing chip

Air monitoring is a challenging objective both for city safeguard and human health. However, in order to get information on the real population exposure with the necessary spatial and temporal resolution a high density monitoring network would be needed. To this aim, small, reliable, low cost, integrated silicon-based sensors would be required. Among the different materials proposed in literature for gas sensor integration, porous silicon (PS) is one of the most promising because of its intrinsic compatibility with the silicon technology. In this work, the design and fabrication of a gas sensing chip, containing an array of PS gas sensors integrated along with several electronic basic blocks, by using an industrial CMOS process is reported, along with its electrical characterization. Finally, to demonstrate the functionality of the sensing chip, a simple readout electronic interface connected to one of the sensors is used to implement an integrated current-voltage converter

NO2 adsorption effects on p(+)-n silicon junctions surrounded by a porous layer

In this work, nitrogen dioxide (NO2) detection by using p(+)-n silicon diodes surrounded by a porous silicon (PS) layer is demonstrated. The effect of the NO2 (at concentrations of hundreds ppb) on the sensor current was investigated for both reverse and forward polarization voltages, using relative humidity (RH) and ethanol at different levels as interfering species. Adsorption of NO2 in the PS layer modifies the electrical properties of the PS/crystalline silicon interface and, in turn, the p(+)-n diode current. The device shows a high selectivity to NO2 with respect to ethanol. at any polarization voltage and relative humidity level: for instance, a NO2 concentration as low as 100 ppb produces a current variation of about one order of magnitude, while 100 ppm of ethanol do not significantly affect the diode current. For a given NO2 concentration, the current variation depends on the diode bias, so that the sensor response can be tuned by changing the polarization voltage. Finally, the relative humidity, one of the most important interfering species for gas sensors, shows a negligible effect on the sensor behaviour. (c) 2008 Elsevier B.V. All rights reserved

Porous silicon micromachining technology

In this chapter, silicon electrochemical micromachining (ECM) technology is reviewed with particular emphasis to the fabrication of complex microstructures and microsystems, as well as to their applications in optofluidics, biosensing, photonics, and medical fields. ECM, which is based on the controlled electrochemical dissolution of n-type silicon under backside illumination in acidic (HF-based) electrolytes, enables microstructuring of silicon wafers to be controlled up to the higher aspect ratios (over 100) with sub-micrometer accuracy, thus pushing silicon micromachining well beyond up-to-date both wet and dry microstructuring technologies. Both basic and advanced features of ECM technology are described and discussed by taking the fabrication of a silicon microgripper as case study