Label-free electrical detection

Furthermore, as commented in Sec. 4,2.1, impedimetric genosen-sors were also constructed by making use of gold nanoparticles electrodeposited on the surface of a gold electrode, and subsequent immobilization of probe DNA on the surface of gold nanoparticles through a 5 -thiol-linker [15]. The difference of electron-transfer resistance was linear with the logarithm of complementary 

An amplified electrochemical impedimetric aptasensor for thrombin has been also described [70]. A nice improvement in the detection sensitivity was achieved by constructing a sandwich platform where the thiolated aptamers were immobilized on a gold substrate to capture the thrombin molecules. Then, aptamer functionalized Au-NPs were used to amplify the impedimetric signals (Fig. 4.11). A detection limit of 0.02 nM, with a linear range of 0.05 to 18 nM was achieved. 

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The work discussed above demonstrates that it is possible to use molecular monolayers on silicon for label-free electrical detection of DNA hybridization. More work remains to fully understand the details of the observed response, optimize the sensitivity of this approach and benchmark it with respect to fluorescence detection methods. However, this work points... 

C.T. Lin, P.T.K. Loan, T.Y. Chen, K.K. Liu, C.H. Chen, K.H. Wei, et al Label-free electrical detection of DNA hybridization on graphene using Hall effect measurements revisiting the sensing mechanism. Advanced Functional Materials 23 (2013) 2301-2307. 

Direct detection biosensors utilize direct measurement of the biological interaction. Such detectors typically measure physical changes (e.g., changes in optical, mechanical, or electrical properties) induced by the biological interaction, and they do not require labeling (i.e., label free) for detection. Direct biosensors can also be used in an indirect mode, typically to increase their sensitivity. Direct detection systems include optical-based systems (most common being surface plasmon resonance) and mechanical systems such as quartz crystal resonators. 

K. Feng, C. Sun, Y. Kang, J. Chen, J.-H. Jiang, G.-L. Shen, and R.-Q. Yu, Label-free electrochemical detection of nanomolar adenosine based on target-induced aptamer displacement, Electr. Comm., 10,531-535 (2008). 

The topics discussed in the book include electrochemical detection of DNA hybridization based on latex/gold nanoparticles and nanotubes nanomaterial-based electrochemical DNA detection electrochemical detection of microorganism-based DNA biosensor gold nanoparticle-based electrochemical DNA biosensors electrochemical detection of the aptamer-target interaction nanoparticle-induced catalysis for DNA biosensing basic terms regarding electrochemical DNA (nucleic acids) biosensors screen-printed electrodes for electrochemical DNA detection application of field-effect transistors to label-free electrical DNA biosensor arrays and electrochemical detection of nucleic acids using branched DNA amplifiers. 

The benefits of modifying EIS structures with LbL films to achieve biosensors with improved performance was also reported by Abouzar et al., who observed an amplification of the signal response upon alternating layers of polyelectrolytes and enzymes as gate membranes on the p-Si-Si02 EIS structure [99]. A new variant of EIS sensors has been produced, which comprised an array of individually addressable nanoplate field-effect capacitive biochemical sensors with an SOI (silicon-on-insulator) stmcture to determine pH and detect penicillin. It also allows for the label-free electrical monitoring of formation of polyelectrolyte multilayers and DNA (deoxyribonucleic acid)-hybridization event [100]. 

P. Liepold, H. Wieder, H. Hillebrandt, A. Friebel and G. Hartwich, DNA-arrays with electrical detection a label-free low cost technology for routine use in life sciences and diagnostics, Bioelectrochemistry, 67 (2005) 143-150. 

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