doi:10.1038/nindia.2012.60 Published online 25 April 2012
Researchers have designed a novel DNA-based sensor that can detect faulty genes linked to chronic myelogenous leukaemia (CML), a type of blood cancer. This biosensor will be useful for the early detection of CML.
The researchers created a single layer of cadmium selenium quantum dots using stearic acid as spacer molecules. They laid this layer on a hydrophobic indium tin oxide substrate and then smeared CML-specific thiol-terminated DNA probe on top to capture target DNA.
The researchers studied the resulting biosensor through electrochemical investigations using target complementary DNA (cDNA) from CML patients, synthetic single-base mismatch DNA sequences and non-cDNA sequences. They exposed the biosensor to varying concentrations of cDNA for a time period of around 30 minutes. The binding of cDNA to the biosensor's DNA probe was detected by a change in current, using methylene blue as redox indicator.
Upon incubation with the cDNA, the peak current of methylene blue was found to decrease significantly. This occurs because the interaction between methylene blue molecules and nucleoside residues of the probe is prevented by hybrid formation between the probe DNA and the target DNA on the electrode surface.
The team observed a significant decrease in methylene blue peak current for one-base mismatch DNA sequences. This indicates that the fabricated DNA sensor can detect even a single base variation in a target DNA sequence. The biosensor also exhibited the ability to discriminate between DNA samples from CML-positive and CML-negative patients.
"This technique may be useful as an additional diagnostic and monitoring device for CML detection," says lead researcher Bansi D. Malhotra.
The authors of this work are from: Department of Science & Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, Materials Physics & Engineering Division, National Physical Laboratory, (CSIR), Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, and Department of Pathology, Army Hospital (Research & Referral), Delhi Cantt, and Department of Biotechnology, Delhi Technological University, New Delhi, India and Centre for NanoBioengineering & SpinTronics, Chungnam National University, Daejeon, Korea.