Single-Molecule Sandwich Aptasensing on Nanoarrays by Tethered Particle Motion Analysis

Plasmonic Probing of Deoxyribonucleic Acid Hybridization at the Single Base Pair Resolution

Partial DNA duplex formation greatly impacts the quality of DNA hybridization and has been extensively studied due to its significance in many biological processes. However, traditional DNA sensing methods suffer from time-consuming amplification steps and hinder the acquisition of information about single-molecule behavior. In this work, we developed a plasmonic method to probe the hybridization process at a single base pair resolution and study the relationship between the complementarity of DNA analytes and DNA hybridization behaviors. We measured single-molecule hybridization events with Au NP-modified ssDNA probes in real time and found two hybridization adsorption events: stable and transient adsorption. The ratio of these two hybridization adsorption events was correlated with the length of the complementary sequences, distinguishing DNA analytes from different complementary sequences. By using dual incident angle excitation, we recognized different single-base complementary sequences. These results demonstrated that the plasmonic method can be applied to study partial DNA hybridization behavior and has the potential to be incorporated into the identification of similar DNA sequences, providing a sensitive and quantitative tool for DNA analysis.

Target-Synergized Biologically Mediated RAFT Polymerization for Electrochemical Aptasensing of Femtomolar Thrombin

The assay of thrombin levels is integral to the assessment of coagulation function and clinical screening of coagulation disorder-related diseases. In this work, we illustrate the ingenious use of the target-synergized biologically mediated reversible addition-fragmentation chain transfer (RAFT) polymerization (tsBMRP) as a novel amplification strategy for the electrochemical aptamer-based biosensing of thrombin at the femtomolar levels. Briefly, the tsBMRP-based strategy relies on the boronate affinity-mediated decoration of the glycan chain(s) of the target itself with RAFT agents and the subsequent recruitment of signal labels via BMRP, mediated by the direct reduction of RAFT agents by NADH into initiating/propagating radicals. Obviously, the tsBMRP-based strategy is biologically friendly, low-cost, and simple in operation. As thrombin is a glycoconjugate, its electrochemical aptasensing involves the use of the thrombin-binding aptamer (TBA) as the recognition receptor, the site-specific decoration of RAFT agents to the glycan chain of thrombin via boronate affinity, and further the recruitment of ferrocene signal labels via the BMRP of ferrocenylmethyl methacrylate (FcMMA). As boronate affinity results in the decoration of each glycan chain with tens of RAFT agents while BMRP recruits hundreds of signal labels to each RAFT agent-decorated site, the tsBMRP-based strategy allows us to detect thrombin at a concentration of 35.3 fM. This electrochemical aptasensor is highly selective, and its applicability to thrombin detection in serum samples has been further demonstrated. The merits of high sensitivity and selectivity, low cost, good anti-interference capability, and simple operation make the tsBMRP-based electrochemical thrombin aptasensor great promise in biomedical and clinical applications.