The self-enhanced electrochemiluminescence (ECL) with high sensitivity could be an effective method for anticancer drug screening with cell apoptosis monitoring. Here we reported an ultrasensitive ECL cytosensor for cell apoptosis monitoring by using self-enhanced electrochemiluminescent ruthenium-silica composite nanoparticles (Ru-N-SiNPs) labeled annexin V as signal probes. The Ru-N-SiNPs were first synthesized through simple hydrolysis of a novel precursor containing luminescent and intracoreactant groups in one molecule, which presented higher emission efficiency and enhanced ECL intensity due to the shorter electron-transfer path and less energy loss. Moreover, the as-proposed ECL cytosensor was successfully used to investigate efficiency of paclitaxel toward MDA-MB-231 breast cancer cell in the range from 1 nM to 200 nM with a detection limit of 0.3 nM and a correlation coefficient of 0.9917. The improved accuracy and excellent dynamic range revealed the potential applications in biomolecules diagnostics and cells detections, especially in living and complex systems.

Usually, photoelectrochemical (PEC) assays were devoted to the direct modification of photoactive materials on sensing interface, thereby producing high initial signal and unneglected background noise, which could further result in low sensitivity and restricted detection limit during the detection of targets. In this work, a PEC biosensor with near-zero background noise was established for ultrasensitive microRNA-141 (miRNA-141) detection based on DNA tetrahedron (TET) as nanocarrier for efficient immobilization of CdTe quantum dots (QDs)-Methylene Blue (MB) (TET-QDs-MB complex) as signal probe. First, CdTe QDs as PEC signal indicator was bound to the TET through DNA hybridizations. Then, massive MB as PEC signal enhancer was attached to DNA duplex of the TET immobilized with CdTe QDs via intercalation. Thereafter, the as-prepared TET-QDs-MB complex was considered as an efficient PEC signal probe owing to its excellent photovoltaic properties, thereby avoiding direct modification of photoactive materials on sensing interface and producing a near-zero background noise to improve the sensitivity of this PEC biosensor. Besides, the detection sensitivity could be further improved with the help of the duplex specific nuclease (DSN) enzyme-assisted target cycling amplification strategy. The proposed PEC biosensor performs a wide linear range from 50 aM to 50 pM with a low detection limit of 17 aM for miRNA-141, paving a new and promising horizon for highly accurate and ultrasensitive monitoring of multifarious analytes such as proteins, DNAs, and miRNAs in bioanalysis and disease diagnosis.

Here, an ultrasensitive "off-on" electrochemiluminescence (ECL) biosensor was proposed for the determination of telomerase activity by using a self-enhanced ruthenium polyethylenimine (Ru-PEI) complex doped zeolitic imidazolate framework-8 (Ru-PEI@ZIF-8) with high ECL efficiency as an ECL indicator and an enzyme-assisted DNA cycle amplification strategy. The Ru-PEI@ZIF-8 nanocomposites were synthesized by self-enhanced Ru-PEI complex doping during the growth of zeolitic imidazolate framework-8 (ZIF-8), which presented high ECL efficiency and excellent stability. Furthermore, owing to the porosity of Ru-PEI@ZIF-8, the self-enhanced Ru-PEI complex in the outer layer and inner layer of self-enhanced Ru-PEI@ZIF-8 could be excited by electrons causing the utilization ratio of the self-enhanced ECL materials to be remarkably increased. To further improve the sensitivity of the proposed biosensor, the telomerase activity signal was converted into the trigger DNA signal which was further amplified by an enzyme-assisted DNA recycle-amplification strategy. The proposed ECL biosensor presented great performance for telomerase activity detection from 5 × 10 to 10 Hela cells with a detection limit of 11 cells. Moreover, this method was applied in the detection of telomerase activity from cancer cells treated with an anticancer drug, which indicated the proposed method held potential application value as an evaluation tool in anticancer drug screening.

Ultrasensitive and rapid quantification of the universal energy currency adenosine triphosphate (ATP) is an extremely critical mission in clinical applications. In this work, a "signal-off" photoelectrochemical (PEC) biosensor was designed for ultrasensitive ATP detection based on a fullerene (C)-decorated Au nanoparticle@MoS (C-Au NP@MoS) composite material as a signal indicator and a p-type PbS quantum dot (QD) as an efficient signal quencher. Modification of wide band gap C with narrow band gap MoS to form an ideal PEC signal indicator was proposed, which could significantly improve photocurrent conversion efficiency, leading to a desirable PEC signal. In the presence of p-type PbS QDs, the PEC signal of n-type C-Au NP@MoS was effectively quenched because p-type PbS QDs could compete with C-Au NP@MoS to consume light energy and electron donor. Besides, the conversion of a limited amount of target ATP into an amplified output PbS QD-labeled short DNA sequence (output S) was achieved via target-mediated aptazyme cycling amplification strategy, facilitating ultrasensitive ATP detection. The proposed signal-off PEC strategy exhibited a wide linear range from 1.00 × 10 pM to 100 nM with a low detection limit of 3.30 fM. Importantly, this proposed strategy provides a promising platform to detect ATP at ultralow levels and has potential applications, including diagnosis of ATP-related diseases, monitoring of diseases progression and evaluation of prognosis.

Here, a novel sensitive electrochemiluminescence (ECL) biosensor using N doped carbon dots (N-CDs) in situ electro-polymerized onto a glassy carbon electrode (GCE) as luminophores, and Pd-Au hexoctahedrons (Pd@Au HOHs) as enhancers, was developed for the detection of intracellular lead ions (Pb(2+)).