Nano-moles detection of tumor specific biomarker DNA for colorectal cancer detection using vertically aligned multi-wall carbon nanotubes based flexible electrodes

A genosensor, flexible and low cost as well, has been fabricated to efficiently detect colorectal cancer cell by targeting CEACAM5, a tumor biomarker. Sensing electrode was fabricated with efficient transfer of a pattern of vertically aligned multi-wall carbon nanotubes on flexible polyethylene terephthalate (PET) substrate by hot press technique, a technologically advanced one. The purpose was to make the sensor device stretchable, bendable, transparent, disposable and heat resistant; without losing the pristine character of the electrode material before and after transfer process. Fabricated sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). The sensor response was checked by adding target DNA within a range of 50–250 μM and sensor showed a detection limit of 0.92μM; exhibited good linearity with a regression coefficient of 0.96 obtained through calibration plot. The sensor was found to be highly sensitive, stable and good specificity as binding occurs only with the complementary DNA. Besides, the genosensor showed relative standard deviation of 6.5 % and 6.7 % at respective 100 μM and 150 μM complementary DNA concentrations. Reproducibility and stability are two crucial parameters where the developed sensor have scored extremely well.     

Preparation and characterization of nitrilotriacetic-acid-terminated self-assembled monolayers on gold surfaces for matrix-assisted laser desorption ionization-time of flight-mass spectrometry analysis of proteins and peptides

On-target affinity capture, enrichment and purification of biomolecules improve detection of specific analytes from complex biological samples in matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) analysis. In this paper, we report a simple method for preparation of a self-assembled nitrilotriacetic acid (NTA) monolayer on gold surface which can be used as a MALDI-TOF-MS sample target specifically for recombinant oligohistidine-tagged proteins/peptides and phosphorylated peptides. The NTA functional groups are immobilized to the gold surface via the linkage of 1,8-octanedithiol which forms a self-assembled monolayer on gold. Characterization by X-ray photoelectron spectroscopy and MALDI analysis of the modified surface are described. The chemically modified surface shows strong affinity toward the analytes of interest, which allows effective removal of the common interferences, e.g. salts and detergents, and therefore leads to improved signal/noise ratio and detection limit. The use of the modified surface simplifies the sample preparation for MALDI analysis of these targeted analytes.