EzyAmp signal amplification cascade enables isothermal detection of nucleic acid and protein targets

Sensitive Detection of Nucleic Acids Using Subzyme Feedback Cascades

The development of Subzymes demonstrates how the catalytic activity of DNAzymes can be controlled for detecting nucleic acids; however, Subzymes alone lack the sensitivity required to detect low target concentrations. To improve sensitivity, we developed a feedback system using a pair of cross-catalytic Subzymes. These were individually tethered to microparticles (MP) and separated by a porous membrane rendering them unable to interact. In the presence of a target, active PlexZymes^® cleave a first Subzyme, which separates a first DNAzyme from its MP, allowing the DNAzyme to migrate through the membrane, where it can cleave a second Subzyme. This releases a second DNAzyme which can now migrate through the membrane and cleave more of the first Subzyme, thus initiating a cross-catalytic cascade. Activated DNAzymes can additionally cleave fluorescent substrates, generating a signal, and thereby, indicating the presence of the target. The method detected 1 fM of DNA homologous to the ompA gene of Chlamydia trachomatis within 30 min, demonstrating a 10,000-fold increase in sensitivity over PlexZyme detection alone. The Subzyme cascade is universal and can be triggered by any target by modifying the target sensing arms of the PlexZymes. Further, it is isothermal, protein-enzyme-free and shows great potential for rapid and affordable biomarker detection.

Universal ratiometric electrochemical biosensing platform based on mesoporous platinum nanocomposite and nicking endonuclease assisted DNA walking strategy

The occurrence and development of many complex diseases are associated with various molecules, whose contents are rarely in the early stage of the disease. Thus a universal platform for the ultrasensitive detection of multilevel biomarkers should be developed. In this study, we introduced an electrochemical biosensing system based on nicking endonuclease (Nt.BbvCI) assisted DNA walking strategy. We successfully constructed a universal signal-off-on ratiometric electrochemical biosensor for various biomolecules, including small molecules, nucleic acids, and proteins, by progressively optimizing the schematics (schemes 1, 2, and 3). The MB-hairpin probes (MB-HPs) acted as a signal-off probe, and nanocomposites (MPNs@DOX@DNA2) acted as a conventional signal-on probe (scheme 3). With the aid of the MPNs@DOX@DNA2 and Nt.BbvCI assisted DNA walking mechanism, the designed ratiometric electrochemical biosensor showed a high sensitivity and broad detection range. In addition, the proposed method can be utilized to detect diverse targets quantitatively by changing the sequence of aptamers under optimum experimental conditions. Furthermore, it has been widely proved to realize well-accepted signal response in identifying complex samples, thereby resulting in an wide prospect for bioanalysis and clinical diagnosis.