Bifunctional TiO2 Nanoflower-Induced H4TCBPE Aggregation Enhanced Electrochemiluminescence for an Ultrasensitive Assay of Organophosphorus.

In this work, the aggregation-induced emission ligand 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H4TCBPE) was rigidified in the Ti-O network to form novel electrochemiluminescence (ECL) emitter H4TCBPE-TiO2 nanospheres, which acted as an effective ECL emitter to construct an "on-off" ECL biosensor for ultrasensitive detection of malathion (Mal). H4TCBPE-TiO2 exhibited excellent ECL responses due to the Ti-O network that can restrict the intramolecular free motions within H4TCBPE and then reduce the nonradiative relaxation. Moreover, TiO2 can act as an ECL co-reaction accelerator to promote the generation of sulfate radical anion (SO4•-), which interacts with H4TCBPE in the Ti-O network to produce enhanced ECL response. In the presence of Mal, numerous ligated probes (probe 1 to probe 2, P1-P2) were formed and released by copper-free click nucleic acid ligation reaction, which then hybridized with hairpin probe 1 (H1)-modified H4TCBPE-TiO2-based electrode surface. The P1-P2 probes can initiate the target-assisted terminal deoxynucleoside transferase (TdTase) extended reaction to produce long tails of deoxyadenine with abundant biotin, which can load numerous streptavidin-functionalized ferrocenedicarboxylic acid polymer (SA-PFc), causing quenching of the ECL signal. Thus, the ultrasensitive ECL biosensor based on H4TCBPE-TiO2 ECL emitter and click chemistry-actuated TdTase amplification strategy presents a desirable range from 0.001 to 100 ng/mL and a detection limit low to 9.9 fg/mL. Overall, this work has paved an avenue for the development of novel ECL emitters, which has opened up new prospects for ECL biosensing.

Recent advances in metal-organic framework-based photoelectrochemical and electrochemiluminescence biosensors.

As a newly emerging class of molecular crystal materials, metal-organic frameworks (MOFs) are extensively used in a variety of fields including catalysis, separation, energy storage, and biosensors, by virtue of their large specific surface area, excellent chemical stability, and adjustable pore size. In particular, several functional materials have been integrated into the MOF structure, which greatly improves the conductivity of MOFs and facilitates the application of MOFs in the field of electrochemical biosensing. Herein, this review highlights the recent applications of MOF composites for photoelectrochemical (PEC) and electrochemiluminescence (ECL) biosensors. This paper first briefly describes the classification and various synthesis methods of MOFs. Then, it comprehensively summarizes different types of MOF-based biosensors in PEC and ECL and their applications. Finally, the challenges and outlook for future work in MOF-based PEC and ECL biosensors are tentatively proposed.

Cu2+@NMOFs-to-bimetallic CuFe PBA transformation: An instant catalyst with oxidase-mimicking activity for highly sensitive impedimetric biosensor.

In this work, a facile impedance biosensor was constructed for sensitive assaying of miRNA-10b based on the Cu2+ modified NH2-metal organic frameworks (NMOF@Cu2+) coupling with a three-dimensional (3D) DNA walker signal amplification strategy. Specifically, abundant Cu2+ can adhere to the MOF via the coordination reaction between NH2 and Cu2+, which can be applied as a skeleton to produce CuFe Prussian blue analogue@NMOF (CuFe PBA@NMOF) just in time. Meanwhile, the carboxyl group, which is rich in the organic ligands of the NMOF, can be used to assemble DNA strands (complementary strand, CS) (CS-NMOF@Cu2+) for biorecognition reaction. With the introduction of the target, a 3D DNA walker was triggered to shear out large amounts of assistant strands (AS), which were then anchored on the surface of GCE. Afterward, CS-NMOF@Cu2+ can be assembled on the GCE by hybridization with AS. Eventually, abundant CuFe PBA@NMOF were generated in situ on the electrode with the help of K3[Fe(CN)6], which can catalyze the 4-chloro-1-naphthol (4-CN) precipitation without H2O2, thereby increasing the resistance of the platform. Under the optimal conditions, the EIS biosensor presents reliable analytical performance in a wide linear range from 0.8 pM to 250 pM with a low detection limit of 0.5 pM.