Approach For Ultrasensitive Detection Research Articles

Improved approach for ultra-sensitive detection of NO

An improved approach has been developed for ultra-sensitive detection of the concentration of NO using Faraday Modulation spectrometry (FAMOS) combined with the strong electronic transition. By changing the modulating magnetic field attributing to linear absorption and refraction of gas sample, the polarized laser was rotated and absorbed by the complex refraction index of NO. We confirm the relation between the magnitudes of absorption and the optimum modulation magnetic field. Also, the accuracy and the precision of the technique have been evaluated at different pressures. It is shown that the system is capable of detecting NO concentration down to 0.34 ppb·m.

원자 힘 현미경을 이용한 단일 생분자 힘 측정

The interaction force between biomolecules (DNA DNA, antigen-antibody, ligand-receptor, protein-protein) defines not only biomolecular function, but also their mechanical properties and hence bio-sensor. Atomic force microscopy (AFM) is nowadays frequently applied to determine interaction forces between biological molecules and biomolecular force measurements, obtained for example using AFM can provide valuable molecular-level information on the interactions between biomolecules. A proper modification of an AFM tip and/or a substrate with biomolecules permits the direct measurement of intermolecular interactions, such as DNA-DNA, protein-protein, and ligand-receptor, etc. and a microcantilever-based sensor appeared as a promising approach for ultra sensitive detection of biomolecular interactions.

Electrical detection of DNA using gold and magnetic nanoparticles and bio bar-code DNA between nanogap electrodes

This paper presents an electrical detection method on a DNA biochip that employs a novel approach for ultra sensitive detection of DNA using self-assembled gold nanoparticles and bio-bar-code-based amplification (BCA) DNA. The experimental study relies on three-components oligonucleotide-modified gold nanoparticles, single-component oligonucleotide-modified magnetic nanoparticles and subsequent detection of amplified target DNA in the form of bio-bar-code ssDNA (single strand DNA) using a chip-based detection method. In this study, the BCA technique measures the bar-code DNA rather than the target DNA. There withal, the DNA chips with nanogap electrodes are fabricated by electron-beam lithography. The gap distance and an electrode height are 300 and 65 nm, respectively. Here, the surface between the electrodes and multilayer of gold nanoparticles is established by the hybridization among single strand BCA, the second capture DNA (C2DNA) and the second probe DNA (P2DNA). Measurable current through nanogap electrodes can be obtained over multilayer gold nanoparticles. In this way, magnetic nanoparticles and bio-bar-code DNA are used to amplify obtainable current through nanogap electrodes from the extremely low concentration of target DNA. The detective concentration of target DNA with electrical DNA biosensor is as low as 1 fM for the analysis of current-voltage curves.