A Feasibility Study of a Capacitive Biosensor for Direct Detection of DNA Hybridization

Abstract

This preliminary study was performed to prove the feasibility of a direct capacitive DNA biosensor for detection of nucleic acids. Two different methods for immobilization of the oligonucleotide probes were used. The ®rst type of sensor was composed of a gold rod with a self-assembled monolayer of a 26-base long oligonucleotide probe, modi®ed with an SH-group at the 5 H -end. Coverage studies showed that only around 20% of the surface was covered, probably due to the bulky nature of the probes. Hybridization studies performed in a¯ow-through cell showed selectivity towards a DNA sample containing single stranded fragments of cytomegalo virus (CMV) possessing a complementary sequence. As few as 25 molecules could be detected at sample concentrations of 0.2 attomolar with an injection volume of 250 mL. Controls with fragments of double-stranded CMV and single-stranded hepatitis B virus and tyrosinase mRNA gave all lower responses. The other type of sensor was modi®ed by covalent immobilization of a phosphorylated 8-base long oligonucleotide probe to a self-assembled monolayer of cysteamine. This biosensor also showed selectivity against single stranded fragments of CMV and also in this case as few as 25 molecules could be detected.

Label‐Free Impedance Biosensors: Opportunities and Challenges

“…In 1998 similar results were reported for IL-2, and even more impressive results for IL-6, though the detection limits were not specified [149]. The same investigators later constructed a DNA biosensor based on the same principle, and reported a detection limit of 0.2 aM for a 179mer ssDNA target using 26mer and 8mer oligonucleotide probes [188]. They used a target much larger than the probe, but a still-impressive 1 -5 aM limit of detection is expected for identical-length targets.…”

Carbon and gold electrodes as electrochemical transducers for DNA hybridisation sensors

“…The carbodiimide covalent coupling of a 8-mer oligonucleotide to a previously self-assembled monolayer of cysteamine was described by Johansson and co-workers (Berggren et al, 1999).…”

“…Johansson's group demonstrated that the decrease in capacitance of a probe-modified gold electrode, accrued from the hybridisation to the complementary strand and the corresponding displacement of solvent molecules from the surface, can be used for monitoring with high sensitivity and speed the hybridisation event (Berggren et al, 1999). In hybridisation studies performed in a flow-through cell, as few as 25 molecules of single-stranded, 179 bp cytomegalovirus target sequence could be detected.…”

Peer Reviewed: Detecting DNA Hybridization and Damage

“…The large differences in capacitance measurements arising from the interfacial properties of ss-and dsDNAs have been shown to recognize DNA hybridization (1,27,28). Recently, a three-component ODN system on a gold electrode was used to detect specific DNA sequences by Faradaic impedance spectroscopy (29).…”