Nucleic acid biosensors probes

Optical nucleic acid biosensors and microarrays based on fluorescence detection make use of fluorescent dyes to provide a measurable signal for target/probe hybridization. Ideally, fluorophores used for detecting nucleic acid hybridization should exhibit large molar absorptivity, resistance to pho-tobleaching, quantum yields that approach unity and the abibty to produce a resolvable signal at low concentrations both quickly and reproducibly [40]. 

Deshpande, S. S. Sharma, . P. Diagnostics. Immunoassays, nucleic acid probes, and biosensors — two decades of development, current status, and future projections in clinical, environmental, and agricultural applications, Diagnostics in the year 2000. Antibody, Biosensor, and Nucleic Acid Technologies , Eds. Singh, P. Sharma, . P. Tyle, P. Van Nostrand Reinhold New York, 1993, pp. 459-525. 

An electrochemical DNA hybridization biosensor basically consists of an electrode modified with a single stranded DNA called probe [109]. Usually the probes are short oligonucleotides (or analogues such as peptide nucleic acids). The first and most critical step in the preparation of an electrochemical DNA biosensor is the immobilization of the probe sequence on the electrode. The second step is the hybrid formation under selected conditions of pH, ionic strength and temperature. The next step involves the detection of the double helix... 

Molecular beacons (MBs) are hairpin-shaped oligonucleotides that report the presence of specific nucleic acids. The MBs have been immobihzed by Tan and co-workers [27] onto ultrasmall optical fibre probes through avidin-biotin binding. The MB-DNA biosensor detected its target DNA molecules, in real time, with selectivity for a single base-pair mismatch. This MB-DNA-biosensor was used by Perlette and Tan [28] for real-time monitoring of mRNA-DNA hybridization inside a living cell. 

Assays based on sandwich-hybridization are available in several platforms, such as sequential injection analysis (55), microtiter plate assays (61), and microfluidic devices (62). The LFA biosensor assays described in this chapter rely on the sandwich-hybridization of a nucleic acid sequence based amplified (NASBA) RNA target between a membrane immobilized capture probe and SRB-encapsulating liposome conjugated reporter probe. NASBA uses the enzymes avian myeloblastosis virus reverse transcriptase (AMV-RT), RNaseH, and T7 DNA dependent RNA polymerase in the presence of deoxyribonucleoside triphosphates and appropriate primers to amplify relatively few copies of target RNA into... 

So far, several bioanalytical methods, including biosensors, have used nucleic acid probes to detect specific sequences in RNA or DNA targets through... 

This definition also clarifies what is not a chemical sensor or biosensor for purposes of market projections and commercialization. Passive assays such as, for example, colorimetric chemical reactions, immunoassays, and nucleic acid probes are not sensors. While such assays do result in a quantifiable entity (such as color production, fluorescence, etc), the assay itself does not provide the means to quantify the response. Rather, a separate quantification system is required. 

Peptide nucleic acid (PNA) is a powerful new biomolecular tool with a wide range of important applications. PNA mimics the behavior of DNA and binds complementary nucleic acid strands and RNA sequences with high affinity and selectivity. The unique chemical, physical, and biological properties of PNA are exploited to produce powerful biomolecular tools, antisense and antigene agents, molecular probes, and biosensors [50-53]. 

---