DNAzymes, screened through in vitro selection, have shown great promise as molecular tools in the design of biosensors and nanodevices. The catalytic activities of DNAzymes depend specifically on cofactors and show multiple enzymatic turnover properties, which make DNAzymes both versatile recognition elements and outstanding signal amplifiers. Combining nanomaterials with unique optical, magnetic and electronic properties, DNAzymes may yield novel fluorescent, colorimetric, surface-enhanced Raman scattering (SERS), electrochemical and chemiluminescent biosensors. Moreover, some DNAzymes have been utilized as functional components to perform arithmetic operations or as “walkers” to move along DNA tracks. DNAzymes can also function as promising therapeutics, when designed to complement target mRNAs or viral RNAs, and consequently lead to down-regulation of protein expression. This feature article focuses on the most significant achievements in using DNAzymes as recognition elements and signal amplifiers for biosensors, and highlights the applications of DNAzymes in logic gates, DNA walkers and nanotherapeutics.

A DNAzyme-based ELISA, termed DLISA, was developed as a novel protein enzyme-free, triply amplified platform, combining a catalytic and molecular beacon (CAMB) system with a cation exchange reaction for ultrasensitive multiplex fluorescent immunosorbent assay. Classical ELISA, which employs protein enzymes as biocatalysts to afford amplified signals, suffers from poor stability caused by the irreversible denaturation of these enzymes under harsh conditions, such as heat and acidity. Compared with proteins, nucleic acids are more stable and adaptable, and they can be easily produced using a commercial DNA synthesizer. Moreover, the catalytic and cleavage activities of DNAzyme can be achieved in solution; thus, no enzyme immobilization is needed for detection. Taken together, these attributes suggest that a DNAzyme-based ELISA detection approach will be more robust than current ELISA assays. Importantly, the proposed triply amplified DLISA immunoassay method shows ultrasensitive detection of such targets as human IgG with a detection limit of 2 fg/mL (3 × 10–17 M), which is well within the range of many important disease biomarkers. DLISA can also be used to construct a sensing array for simultaneous multiplexed detection. With these merits, this high-throughput, stable, simple, sensitive, and low-cost multiplex fluorescence immunoassay shows promise for applications in clinical diagnosis.

DNAzymes, screened through in vitro selection, have shown great promise as molecular tools in the design of biosensors and nanodevices. The catalytic activities of DNAzymes depend specifically on cofactors and show multiple enzymatic turnover properties, which make DNAzymes both versatile recognition elements and outstanding signal amplifiers. Combining nanomaterials with unique optical, magnetic and electronic properties, DNAzymes may yield novel fluorescent, colorimetric, surface-enhanced Raman scattering (SERS), electrochemical and chemiluminescent biosensors. Moreover, some DNAzymes have been utilized as functional components to perform arithmetic operations or as “walkers” to move along DNA tracks. DNAzymes can also function as promising therapeutics, when designed to complement target mRNAs or viral RNAs, and consequently lead to down-regulation of protein expression. This feature article focuses on the most significant achievements in using DNAzymes as recognition elements and signal amplifiers for biosensors, and highlights the applications of DNAzymes in logic gates, DNA walkers and nanotherapeutics.