Nucleic acid/quantum dots (QDs) hybrid systems for optical and photoelectrochemical sensing

Nucleic acid/semiconductor quantum dots (QDs) hybrid systems combine the recognition and catalytic properties of nucleic acids with the unique photophysical features of QDs. These functions of nucleic acid/QDs hybrids are implemented to develop different optical sensing platforms for the detection of DNA, aptamer-substrate complexes, and metal ions. Different photophysical mechanisms including fluorescence, electron transfer quenching, fluorescence resonance energy transfer (FRET), and chemiluminescence resonance energy transfer (CRET) are used to develop the sensor systems. The size-controlled luminescence properties of QDs are further implemented for the multiplexed, parallel analysis of several DNAs, aptamer-substrate complexes, or mixtures of ions. Similarly, methods to amplify the sensing events through the biocatalytic regeneration of the analyte were developed. An additional paradigm in the implementation of nucleic acid/QDs hybrids for sensing applications involves the integration of the systems with electrodes, and the generation of photocurrents as transduction signals for the sensing events. Finally, semiconductor QDs conjugated to functional DNA machines, such as "walker" systems, provide an effective optical label for probing the dynamics and mechanical functions of the molecular devices. The present article addresses the recent advances in the application of nucleic acid/QDs hybrids for sensing applications and DNA nanotechnology, and discusses future perspectives of these hybrid materials.