Hybridization chain reaction performed on a metal surface as a means of signal amplification in SPR and electrochemical biosensors.

A more specific and intense signal is desirable for most kinds of biosensors for biomedical or environmental applications, and it is especially so for label-free biosensors. In this paper, we show that hybridization chain reaction (HCR) can be exploited for the easily detectable accumulation of nucleic acids on metal surfaces as an event triggered by specific recognition between a probe and a target nucleic acid. We show that this process could be exploited to increase the sensitivity in the detection of nucleic acids derived from a pathogenic microorganism. This strategy can be straightforwardly implemented on SPR biosensors (commercial or custom-built) or on label-free electrochemical biosensors. Together with signal amplification, HCR can serve as a confirmation of the specificity of target recognition, as it involves the specific matching with a separate base sequence in the target nucleic acid. Furthermore, the kinetics of the target binding and the HCR can be easily distinguished from each other, providing an additional means of confirmation of the specific recognition.

Phantom with pulsatile arteries to investigate the influence of blood vessel depth on pulse oximeter signal strength.

This paper describes a three-layer head phantom with artificial pulsating arteries at five different depths (1.2 mm, 3.7 mm, 6.8 mm, 9.6 mm and 11.8 mm). The structure enables formation of spatially and temporally varying tissue properties similar to those of living tissues. In our experiment, pressure pulses were generated in the arteries by an electronically controlled pump. The physical and optical parameters of the layers and the liquid in the artificial arteries were similar to those of real tissues and blood. The amplitude of the pulsating component of the light returning from the phantom tissues was measured at each artery depth mentioned above. The build-up of the in-house-developed pulse oximeter used for performing the measurements and the physical layout of the measuring head are described. The radiant flux generated by the LED on the measuring head was measured to be 1.8 mW at 910 nm. The backscattered radiant flux was measured, and found to be 0.46 nW (0.26 ppm), 0.55 nW (0.31 ppm), and 0.18 nW (0.10 ppm) for the 1.2 mm, 3.7 mm and 6.8 mm arteries, respectively. In the case of the 9.6 mm and 11.8 mm arteries, useful measurement data were not obtained owing to weak signals. We simulated the phantom with the arteries at the above-mentioned five depths and at two additional ones (2.5 mm and 5.3 mm in depth) using the Monte Carlo method. The measurement results were verified by the simulation results. We concluded that in case of 11 mm source-detector separation the arteries at a depth of about 2.5 mm generate the strongest pulse oximeter signal level in a tissue system comprising three layers of thicknesses: 1.5 mm (skin), 5.0 mm (skull), and >50 mm (brain).

A novel point of care diagnostic device: impedimetric detection of a biomarker in whole blood.

There is an unmet medical need for a more reliable and earlier assessment of patients suspected of having a deep vein thrombosis. We describe a novel approach which is developing a highly reliable, accurate, portable and handheld prototype medical diagnostic device to improve radically the speed, accuracy and reliability with which DVT and related blood clotting conditions can be assessed. The device will measure whole blood concentration of D-dimer, a recognized biomarker of increased blood clotting activity, and through innovation in the development of a novel detection, measurement and reporting system, will offer the opportunity to use the test in the point of care setting. The device combines innovation in antibody bio-engineering for high specificity immunoassay-based diagnostics and nano/micro engineered impedimetric analysis electrodes incorporating a biocompatible polymer substrate with development of a disposable microfluidic manifold specifically enabling diagnostics at the point-of-first-contact.