Biology Reference
In-Depth Information
1.3 Detection of Specific DNA Interactions
Among specific DNA interactions tested using DNA-based biosen-
sors, DNA hybridization, DNA association with low molecular mass
compounds (drugs, chemicals), and DNA damage are typically
considered.
1.3.1
DNA Hybridization Biosensors
DNA hybridization is a chemical interaction of DNA based on the
ability of ssDNA to form a helix, dsDNA with ssDNA counterpart
exhibiting nucleotide sequence complementarity. In DNA hybridiza-
tion biosensors, a specifically designed ssDNA probe (capture
probe [CP]) with a defined (known) nucleotide sequence is usually
immobilized on the electrode surface and allowed to interact as
a recognition element with target DNA (tDNA) in test solution.
By varying experimental conditions such as the pH, temperature,
and ionic strength, hybridization e
ciency can be controlled, thus
allowing detection of single- ormulti-basemismatches [15, 31].
Experimental arrangement for electrochemical DNA hybridiza-
tion biosensorsincludes the following:
1. Label-free and indicator (reagent)-less detection of target DNA
typically basedon guanineresidues response.
2. Noncovalent redox indicators that allow distinguishing between
the ssCP and dsDNA hybrid at the electrode surface (successful
hybridization)[22, 23].
3. Sandwich hybridization assay that employs a covalently labeled
reporter or signaling probe (RP) and involves two tDNA recogni-
tion steps (CP-tDNA and tDNA-RP) [32]. The RPs are designed to
hybridizewiththetDNAatasitenexttothesequencerecognized
bythecaptureprobetoconfere
cientelectroniccommunication
between the label and the electrode.
4. Peptidenucleicacid(PNA)probesasaDNAanaloguethatpossess
an uncharged pseudopeptide backbone instead of the charged
phosphate-sugar backbone of natural DNA and, consequently,
greater a
nity to complementary DNA and better distinction
between closely related sequences [33].
