Ultrasensitive Photoelectrochemical Biosensor Based on DNA Tetrahedron as Nanocarrier for Efficient Immobilization of CdTe QDs-Methylene Blue as Signal Probe with Near-Zero Background Noise

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

Ultrasensitive Assay for Telomerase Activity via Self-Enhanced Electrochemiluminescent Ruthenium Complex Doped Metal–Organic Frameworks with High Emission Efficiency

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 × 10¹ to 10⁶ 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 Cytosensor Based on Self-Enhanced Electrochemiluminescent Ruthenium-Silica Composite Nanoparticles for Efficient Drug Screening with Cell Apoptosis Monitoring

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

Multiparameter Analysis-Based Electrochemiluminescent Assay for Simultaneous Detection of Multiple Biomarker Proteins on a Single Interface

Electrochemiluminescent (ECL) assay with high sensitivity has been considered as one of the potential strategies to simultaneously detect multiple biomarker proteins. However, it was essential, but full of challenges, to overcome the limitation caused by cross reactions among different ECL indicators. Herein, the multiparameter analysis of ECL-potential signals demonstrated by multivariate linear algebraic equations was first employed in the simultaneous ECL assay to realize multiple detection of biomarker proteins on a single interface. Additionally, owing to the exponential amplification of self-synthesized nucleotide dendrimer by hybridization chain reaction (HCR) and rolling circle amplification (RCA), the developed simultaneous ECL assay showed improved sensitivity and satisfactory accuracy for the detection of N-terminal of the prohormone brain natriuretic peptide (BNPT) and cardiac troponin I (cTnI). Furthermore, a self-designed magnetic beads-based flow system was also employed to improve the feasibility and analysis speed of the simultaneous ECL assay. Importantly, the proposed strategy enabled simultaneous detection of multiple biomarker proteins simply, which could be readily expanded for the multiplexed estimation of various kinds of proteins and nucleotide sequence also, revealing a new avenue for early disease diagnosis with higher efficiency