DNA biosensors and bioassays

Electrochemical devices have proven very useful for sequence-specific biosensing of DNA. Electrochemical detection of DNA hybridization usually involves monitoring a current response under controlled potential conditions. The hybridization event is commonly detected via the increased current signal of a redox indicator (that recognizes the DNA duplex) or from other hybridization-induced changes in electrochemical parameters (e.g., conductivity or capacitance). Modern electrical DNA hybridization biosensors and bioassays offer remarkable sensitivity, compatibility with modern microfabrication technologies, inherent miniaturization, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway. Such devices are thus extremely attractive for obtaining the sequence-specific information in a simpler, faster, and cheaper manner, compared to traditional hybridization assays. 

MOLECULAR RECOGNITION BIOASSAYS, BIOSENSORS, DNA-ARRAYS AND PYROSEQUENCING... 

In undertaking our search of the literature linked to bioanalytical assessment of solid waste leachates (Tab. 2), we circumscribed it to small-scale toxicity testing performed on leachates. Furthermore, we did not exclude marine bioassays, but we exclusively selected literature references involving test battery approaches (TBAs) on solid wastes (or their elutriates). As defined previously in the first chapter of this book, a TBA represents a study conducted with two or more tests representing at least two biotic levels. As also pointed out in Section 2 of this chapter, TBAs are suitable to assess hazard at different levels so as not to underestimate ecotoxicity. Nevertheless, we have not excluded from this review publications describing other types of bioassays (e.g., terrestrial bioassays, sub-cellular bioassays or those carried out with recombinant DNA (micro)organisms and biosensors), when those were part of the TBA. 

In bioassays, the molecular recognition between antibody and antigen as well as the signal generation for detection usually occur in solution or on an inert solid phase, whereas in biosensors, they are closely integrated on the surface of an active electronic device. DNA-arrays make use of the specific recognition of single strands of DNA, which only combine to form a double strand where... 

The use of DNA in diagnostics has increased in recent years and is likely to become more important following the now completed Human Genome Project and the rapid elucidation of more and more microbial genomes. Reporter gene technology and biosensors can make use of DNA in the development of toxicity bioassays that are rapid, sensitive, and cost-effective. 

---