Nucleic acid-based ratiometric electrochemiluminescent, electrochemical and photoelectrochemical biosensors: a review

The demand of precise assay of nucleic acids and other bioanalytes has been increasing enormously in various areas including point-of-care diagnostics, military, environmental monitoring and so on. Compared with other nucleic acid biosensors, the electrochemical nucleic acid biosensors possess a range of merits like amenable miniaturization, lowcosts and high sensitivity. Ratiometric electrochemical nucleic acid biosensors can overcome the inherent systematic errors of conventional electrochemical biosensors and enhance the reproducibility and credibility. This short review (with 81 refs.) summarizes the evolvements made in the area of nucleic acid-based biosensors based on ratiometric (electrochemiluminescent, electrochemical and photoelectrochemical) readout in the past few years. Many of the methods discussed here are based on the use of advanced nanomaterials such as quantum dots, graphitic carbon nitrides, graphene oxide, C-dots, gold nanoparticles, metal-organic frameworks, and respective nanohybrids. Three sections (on electrochemiluminescence, classical electrochemical and emerging photoelectrochemical systems) demonstrate the merits of ratiometric assaysin various applications. The review ends with a section with conclusions and a discussion of future perspectives.