Accurate and ultrasensitive detection for PEDV based on photoelectrochemical sensing coupling loop-mediated isothermal amplification

Potential-Resolved Ratio Electrochemiluminescence Biosensor Based on Perylene Diimide-MOF and DNA Nanoflowers-CdS Quantum Dots for Detection of Dual Targets

BRCA1 gene and carcinoembryonic antigen (CEA) are important markers of breast cancer, so accurate detection of them is significant for early detection and diagnosis of breast cancer. In this study, a potential-resolved ratio electrochemiluminescence (ECL) biosensor using perylene diimide (PDI)-metal-organic framework and DNA nanoflowers (NFs)-CdS quantum dots (QDs) was constructed for detection of BRCA1 and CEA. Specifically, PDI-MOF and CdS QDs can generate potential-resolved intense ECL signals only using one coreactant, so the detection procedure can be effectively simplified. PDI-MOF was first attached to the electrode by graphene oxide, and the dopamine (DA) probe was linked to quench the ECL signal by DNA hybridization. In the presence of target BRCA1, it can form a bipedal DNA walker, so the quenching molecules (DA) were detached from the electrode via the walker amplification process aided by Mg2+, so that the PDI signal at -0.25 V was restored for the BRCA1 assay. Moreover, CdS QDs@DNA NFs as amplified signal probes were formed by self-assembly, and the target CEA-amplified product introduced the CdS QDs@DNA NFs to the electrode, so the QD ECL signal at -1.42 V was enhanced, while the ECL signal of PDI is unchanged; thus, CEA detection was achieved by the ratio value between them. Therefore, the detection accuracy is guaranteed by detection of two cancer markers and a ratio value. This biosensor has a great contribution to the development of new ECL materials and a novel ECL technique for fast and efficient multitarget assays, showing great significance for the early monitoring and diagnosis of breast cancer.

Efficient CdIn2S4/MgIn2S4 heterojunction for ultrasensitive detection of lung cancer marker neuron-specific enolase

In this work, a photoelectrochemical (PEC) immunosensor was constructed for the ultrasensitive detection of lung cancer marker neuron-specific enolase (NSE) based on a microflower-like heterojunction of cadmium indium sulfide and magnesium indium sulfide (CdIn2S4/MgIn2S4, CMIS) as photoactive material. Specifically, the well-matched energy level structure and narrow energy level gradients between CdIn2S4 and MgIn2S4 could accelerate the separation of electron-hole (e--h+) pairs in the CMIS heterojunction to enhance the photocurrent of CMIS, which was increased 5.5 and 80 times compared with that of single CdIn2S4 and MgIn2S4, respectively. Meanwhile, using CMIS as photoactive material, increasing the biocompatibility by dropping Pt NPs on the surface of CMIS to immobilize the antibody through Pt-N bond. Fe3O4-Ab2, acting as the quencher, competitively consumes electron donors and absorbs light, leading to photocurrent quenching. With the increasing of quencher, the photocurrent decreased. Hence, the developed "signal-off" PEC immunosensor realized the trace detection of NSE within the range from 1.0 fg/mL to 10 ng/mL with a low detection limit of 0.34 fg/mL. This strategy provided a new perspective for establishing ternary metal sulfide heterojunction to construct PEC immunosensor for sensitive detection of disease biomarkers.

Wavelength-dependent photoelectrochemical response demonstrated by the determination of acetaminophen and rutin in differential molecularly imprinted polymers strategy

Herein, the excitation wavelength-dependent responses of the molecularly imprinted polymer (MIP) photoelectrochemical (PEC) sensors were investigated, using acetaminophen (AP), rutin (RT) and perfluorooctanoate (PFOA) as the model templates, pyrrole as functional monomer, CuInS2@ZnS/TiO2 NTs as the basic photoelectrode. With wavelength λ > 240 nm, the photocurrent of MIPPFOA enhanced at higher concentrations of PFOA. With increasing AP concentration, the photocurrents of MIPAP could decline with λ < 271 nm, not change at λ = 270 nm, or increase with λ > 270 nm. As RT concentration increased, the photocurrents of MIPRT could decrease (λ < 431 nm), not change (λ = 431 nm) or increase (λ > 431 nm). The PEC responses depend on the comprehensive interaction of two contrary mechanisms from the template molecules within the MIP membrane. The photocurrent is enhanced by the role of the electron donor for photo-generated holes but attenuated due to the steric hindrance effect and the excitation light intensity loss via absorption or scattering. The apparent molar absorption coefficient of AP and RT within MIP membranes are 9.1-19.4 folds of those measured from dilute solutions. By using a routine UV lamp as the light source, the photocurrents of MIPRT at 254 nm and MIPAP at 365 nm were used to determine RT and AP, with the detection limits of 5.3 and 16 nM, respectively. The interference from the non-specific adsorption of interferents on the surfaces of MIPAP and MIPRT was reduced by one order of magnitude via a differential strategy.

Dual-Signal Mode Ratiometric Photoelectrochemical Sensor Based on G-Quadruplex Hole Transport for Rapid and Sensitive Detection of miRNA-210

For rapid and sensitive detection of miRNA-210, which is important for improving the reliability of clinical diagnosis of breast cancer, a dual-signal mode ratiometric photoelectrochemical (PEC) sensor based on a Au/GaN photoanode is proposed. First, a DNA probe was designed that could complement the target miRNA-210. Then, another G-rich DNA sequence was designed to mismatch the probe and form a double-stranded DNA (dsDNA). Upon addition of the target, the dsDNA unwinds from its binding site and releases G-rich single-stranded DNA. In the presence of Mg2+ and K+, this single-stranded DNA molecule spontaneously forms a G-quadruplex structure, facilitating the rapid transport of photogenerated holes, thereby increasing the photocurrent response of Au/GaN and enabling sensitive label-free detection of miRNA-210. By control of different pH values, a response signal was generated at pH 8, while a reference signal was produced at pH 5. The designed PEC system shows a high potential for the development of miRNA-210 detection. Ultimately, the response signal-to-reference signal ratio was used as the variable, and a broad linear span ranging from 10 fM to 1 nM (R2 = 0.993) has been exhibited, with a detection threshold of 3 fM (S/N = 3). The designed PEC platform shows potential for the development of other disease markers.

Ultrasensitive detection of exosomes by microchip electrophoresis combining with triple amplification strategies

The analysis of exosomes is significant as they can be used for various pathophysiological processes, especially cancer related intercellular communication. Therefore, a convenient, reliable, and sensitive detection method is urgently needed. Strand displacement amplification (SDA) and catalytic hairpin assembly (CHA) are two kinds of effective isothermal nucleic acid amplification methods. In this article, an efficient quantitative MCE method for detecting human breast cancer cell (MCF-7) exosomes assisted by triple amplification strategies combining cholesterol probe (Chol-probe) with SDA-CHA was first developed. CD63 aptamer was immobilized on the avidin magnetic beads to specifically capture exosomes and then Chol-probe with high affinity was spontaneously inserted into the exosome membrane, which was the first step of amplification strategy to improve detection sensitivity. After magnetic separation, Chol-probe could complement ssDNA and trigger SDA, producing a large number of DNA sequences (Ta) to trigger CHA, achieving SDA-CHA amplification. Under optimal conditions, the detection limit (LOD) for MCF-7 exosomes was as low as 26 particle/μL (S/N = 3). This method provides an effective approach for sensitive and accurate quantification of tumor exosomes, and can be expected to detect exosomes in clinical samples.