Significant Signal Degradation Research Articles

Sensor Array: Impedimetric Label‐Free Sensing of DNA Hybridization in Real Time for Rapid, PCR‐Based Detection of Microorganisms

AbstractA novel, impedance‐based electronic sensor format was used for label‐free, real‐time detection of microbial DNA on oligonucleotide probe arrays. Detection limits of 5–10 nM were achieved for single‐stranded, PCR‐amplified DNA targets. Hybridization selectivity yielded 9‐ to 12‐fold signal increases for specific targets, and the sensor arrays were re‐used multiple times without significant signal degradation. These and other features of the SHARP Laboratories of America (SLA) sensor array, such as its ability to acquire continuous measurements of DNA as it accumulates on the array surface, make it an attractive biosensor platform for field detection and monitoring of sentinel and/or pathogenic microorganisms.

The electrochemical detection of cadmium using surface-immobilized DNA

An electrochemical assay based on underpotential deposition (UPD) of metal has been utilised for the detection of Cd 2+ using surface immobilized single-stranded DNA (ss-DNA). Since Cd 2+ is able to undergo UPD on gold surface, this allows the opportunity to detect the amount of Cd 2+ accumulated by immobilized ss-DNA directly via voltammetry. This is evidenced by the appearance of Cd 2+/Cd 0 electrochemistry at E 0′ of 92 mV (rather than E 0′ of −795 mV in bulk solution) at the ss-DNA modified gold electrode only after an exposure to Cd 2+ solution. An association constant of 8.33 × 10 5 M −1 was determined from a Cd 2+ calibration curve assuming a Langmuir-binding model for Cd 2+ with surface-immobilized DNA. The high association constant is reflected in a low detectable concentration of 10 pM. The sensing layer can also be regenerated to metal-free status and can be reused up to 18 times without significant signal degradation.