Sensing of UO22+ and design of logic gates by the application of supramolecular constructs of ion-dependent DNAzymes

Supramolecular constructs composed of ion-dependent DNAzymes and their substrates were used to develop DNAzyme cascades that enabled the sensitive detection of UO22+ or the activation of logic gate operations. The supramolecular complex between the UO22+-dependent DNAzyme and its substrate leads, in the presence of UO22+, to the cleavage of the substrate and to the release of the HRP-mimicking DNAzyme that enables the optical analysis of UO22+ (detection limit 1 x 10-9 M). Similarly, supramolecular complexes between the Mg2+- and UO22+-dependent DNAzymes and tailored substrates enables the design of the "OR" and "AND" logic gates, using Mg2+ and UO22+ as inputs.

Perspective on optical biosensors and integrated sensor systems

Optical biosensors have begun to move from the laboratory to the point of use. This trend will be accelerated by new concepts for molecular recognition, integration of microfluidics and optics, simplified fabrication technologies, improved approaches to biosensor system integration, and dramatically increased awareness of the applicability of sensor technology to improve public health and environmental monitoring. Examples of innovations are identified that will lead to smaller, faster, cheaper optical biosensor systems with capacity to provide effective and actionable information.

Applications of aptamers as sensors

Aptamers are ligand-binding nucleic acids whose affinities and selectivities can rival those of antibodies. They have been adapted to analytical applications not only as alternatives to antibodies, but as unique reagents in their own right. In particular, aptamers can be readily site-specifically modified during chemical or enzymatic synthesis to incorporate particular reporters, linkers, or other moieties. Also, aptamer secondary structures can be engineered to undergo analyte-dependent conformational changes, which, in concert with the ability to specifically place chemical agents, opens up a wealth of possible signal transduction schemas, irrespective of whether the detection modality is optical, electrochemical, or mass based. Finally, because aptamers are nucleic acids, they are readily adapted to sequence- (and hence signal-) amplification methods. However, application of aptamers without a basic knowledge of their biochemistry or technical requirements can cause serious analytical difficulties.