Terminal Deoxynucleotidyl Transferase Extension-Dominated In Situ Signal Attenuation-Free Electrochemical Platform and Its Logic Gate Manipulation

Signal generation of traditional electrochemical biosensors suffers from the random diffusion of electroactive probes in a electrolyte solution, which is accompanied by poor reaction kinetics and low signal stability from complex biological systems. Herein, a novel circuit system with autonomous compensation solution ohmic drop (noted as “fast-scan cyclic voltammetry (FSCV)”) is developed to solve the above problems, and employed to achieve terminal deoxynucleotide transferase (TdT) and its small molecule inhibitor analysis. At first, a typical TdT-mediated catalytic polymerization in the conditions of original DNA, deoxythymine triphosphate (dTTP) and Hg2+ is applied for the electrode assembly. The novel electrochemical method can provide some unattenuated signals due to in-situ Hg redox reaction, thus improving reaction kinetics and signal stability. This approach is mainly dependent on TdT-mediated reaction, so it can be applied properly for TdT investigation, and a detection limit of 0.067 U/mL (S/N=3) is achieved successfully. More interesting, we also mimic the function of TdT-related signal communication in various logic gates such as YES, NOT, AND, N-IMPLY, and AND-AND-N-IMPLY cascade circuit. This study provides a new method for the detection of TdT biomarkers in many types of diseases and the construction of a signal attenuation-free logic gate.

A Low-Crossover and Fast-Kinetics Thiolate Negolyte for Aqueous Redox Flow Batteries

Aqueous redox flow batteries (ARFBs) are a promising technology for large-scale energy storage. Developing high-capacity and long-cycle negolyte materials is one of major challenges for practical ARFBs. Inorganic polysulfide is promising for ARFBs owing to its low cost and high solubility. However, it suffers from severe crossover resulting in low coulombic efficiency and limited lifespan. Organosulfides are more resistant to crossover than polysulfides owing to their bulky structures, but they suffer from slow reaction kinetics. Herein, we report a thiolate negolyte prepared by an exchange reaction between a polysulfide and an organosulfide, preserving low crossover rate of the organosulfide and high reaction kinetics of the polysulfide. The thiolate denoted as 2-hydroxyethyl disulfide+potassium polysulfide (HEDS+K2S2) shows reduced crossover rate than K2S2, faster reaction kinetics than HEDS, and longer lifespan than both HEDS and K2S2. The 1.5 M HEDS+1.5 M K2S2 static cell demonstrated 96 Ah L-1negolyte over 100 and 200 cycles with a high coulombic efficiency of 99.2% and 99.6% at 15 and 25 mA cm-2, respectively. The 0.5 M HEDS+0.5 M K2S2 flow cell delivered a stable and high capacity of 30.7 Ah L-1negolyte over 400 cycles (691 h) at 20 mA cm-2. This study presents an effective strategy to enable low-crossover and fast-kinetics sulfur-based negolytes for advanced ARFBs.