Quantum Instruments Sensor Specification Sheet - page 8

Sensors & Transducers Journal, Vol.76, Issue 2, February 2007, pp.935-936

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Fig. 2. This "medical telesensor" chip on a fingertip can measure and transmit body temperature 

(Courtesy:  Oak Ridge National Laboratory, ref. 32). 

3. Biosensing and Nucleic Acid Analyses 

Over the past two decades, the practice of DNA sequence detection has become more ubiquitous and 

will continue to increase exponentially in genetics (primary patient diagnosis, carrier detection and 

prenatal diagnosis), pathology, criminology, food safety and biological warfare agents. This has been 

driven partly by the quantity of DNA sequence information that we have collected on humans and 

other organisms and partly by the increasing technological advances that provides us with the tools 

needed to develop new techniques to monitor biorecognition and interaction events. Current 

methods[33] for the identification of a particular DNA base sequence in a biological sample begin with 

the isolation of intact, double-stranded DNA and employ the polymerase chain reaction (PCR) to 

amplify the region of interest. The PCR product can then be subjected to electrophoresis or adsorbed 

directly onto a membrane, which is then exposed to a solution containing a DNA probe which has been 

chemically or enzymatically labeled with a radioactive material, chemiluminophore or hapten / ligand 

such as biotin to provide detectable signal for DNA hybridization. Radioactive materials are extremely 

sensitive, but have the obvious disadvantage of short self-life & high cost. Radioactive assay can not 

be done in open or ordinary labs which are not well equipped for handling, storage & dumping of 

radioactive materials. Fluorescent dye labels are expensive, they photobleach rapidly & are less 

sensitive. Most recently, Luminescent semiconductor nanocrystals (or “quantum dots”, QD) have been 

used as labels for bioanalytical applications [34-35]. Thermoquenching and extremely high cost are 

potent disadvantages of Quantum dots and hence generally limited to use in sensitive research 

experiments. There fore, large-scale, routine clinical screening based on gene diagnostics is limited by 

the current available technologies. Remarkably, DNA Biosensor technology can provide rapid, simple 

and low-cost on field detection of specific DNA sequence (pathogenic, virulent, transgenic) or point 

mutations that are responsible for, or linked to, inherited diseases. Diseases such as cystic fibrosis, 

muscular dystrophy, sickle-cell anemia, phenylketonuria, 

β-thalassemia and hemophilia A are known 

to be associated with specific changes in normal DNA base sequence. The list of known genetic 

abnormalities that cause, or are associated with, disease states will continue to expand as the 

sequencing of the human genome continues. During sensing of nucleic acids,  single-stranded (ss) 

oligonucleotide probe are immobilized onto transducer surface forming a recognition layer that binds 

its complementary (target) DNA sequence to form a hybrid. The hybridization reaction is recognized 

and analytical signal (light, current, frequency) is passed by the transducer to the processor to provide 

a readable output. The measurement system (transducer and read out device or signal processor) can be 

gravimetric [36], electrochemical [37], optical [38], electrical [39], surface plasma resonance [40] 

based. Electrochemical DNA biosensor based detection show superior results over the other existing 

measurement systems. Basic principle of DNA biosensor is based on the properties that 1) DNA is 

double helical and has strong stacking interaction between bases along axis of double-helix and the 

base-pairing interactions between complimentary sequences are both specific and robust. 2) Double 

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