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A cathodic photoelectrochemical sensor has been developed for the determination of exosomes, based on a dual-signal reduction strategy. A heterostructure of NiO/BiOI/Au NP/CdSe was synthesized as a photoelectrochemical sensing interface, which is able to suppress the recombination of electron-hole pairs and produce a higher photocurrent. The obtained materials were characterized, and the mechanism for the generation of the cathodic photocurrent was proposed. CdSe QDs (quantum dots) modified with DNA2 were assembled on the electrode through the hybridization with EpCAM aptamer on the surface of ITO/NiO/BiOI/Au NP. The introduction of CdSe QDs to the electrode increases the photocurrent.The recognition of exosomes with aptamer DNA led to the separation of CdSe QDs from the electrode, which in turn caused the decrease of photocurrents. Meanwhile, the big volume of exosomes hinders the electron transfer between the electrode and electrolyte. Due to the dual reduction effect, a sensitive PEC sensor was obtained with a detection limit of 1.2 × 102 particles/μL exosomes (λex = 430 nm, bias voltage = − 0.1 V). The cathodic photoelectrochemical sensor showed good selectivity, performed well in a complex biological environment and could be used to distinguishbreast cancer patients from healthy individuals. [ABSTRACT FROM AUTHOR]

A photocathode is described for the determination of microRNA-21 by using CuInS2 as an active photocathode material. Exonuclease III assisted target recycling amplification was employed to enhance the detection sensitivity. The TATA-binding protein (TBP) was applied to enhance steric hindrance which decreases the photoelectrochemical intensity. This strategy is designed by combining the anti-interference photocathode material, enzyme assisted target recycling amplification and TBP induced signal off, showing remarkable amplification efficiency. Under the optimized conditions, the detection limit for microRNA-21 is as low as 0.47 fM, and a linear range was got from 1.0 × 10−15 M to 1.0 × 10−6 M. [ABSTRACT FROM AUTHOR]

A highly sensitive fluorometric method is described for the determination of mercury(II) ions. It is based on (a) the use of a DNA probe containing thymine-thymine mismatches that are employed as Hg(II) recognition elements, (b) subsequent toehold binding, and (c) endocuclease-assisted signal amplification. Target recycling is triggered by exonuclease III. This produces a large amount of ssDNA (defined as primer). Then, the generated primer-initiated strand displacement reaction with the help of polymerase and nicking endonuclease releases the free fluorophore-labelled probe. Under excitation at 532 nm, the fluorescent probe displays emission with a peak at 582 nm. The sensitivity of this method is improved by introduction of nicking endonuclease. The working range of the assay extends from 20 pM to 10 nM, and the detection limit is as low as 6 pM of Hg(II). [ABSTRACT FROM AUTHOR]

In recent years, electrochemical sensors for nucleic acid testing based on CRISPR/Cas12a technology have attracted widespread interest due to their ease of operation and high detection sensitivity. Here, a label-free electrochemical sensor amplified by primer exchange reaction (PER), hybridization chain reaction (HCR) and CRISPR/Cas12a system was developed for analyzing miRNA- 155 and PCB 77. In the presence of targets, PER was initiated, whose products could be used to trigger the trans-cleavage activity of Cas12a for the single-stranded DNA (ssDNA) on the electrode. Afterwards, with the amplification of HCR on the electrode and electrostatic adsorption of Ru(NH 3) 6 3+, the concentration of the targets could be indicated by the DPV intensity with a low background signal. The detection limits for miRNA- 155 and PCB 77 were estimated to be 67 aM and 6.9 pg/L, respectively. This work provides a versatile method for sensitive detection of different targets using the same crRNA and can be used in various biochemical investigations. • A label-free electrochemical sensor was used for the detection of two targets. • PER, CRISPR/Cas system and HCR were applied for signal amplification. • CRISPR/Cas system can decrease the background signal without the usage of PAN. • The same crRNA can be used to detect different targets. [ABSTRACT FROM AUTHOR]

This work develops a novel photoelectrochemical sensor for the detection of carcinoembryonic antigen (CEA) based on the composite of UCNPs with semiconductors and conformational changes in the DNA structure. Firstly, SnS 2 , ZnIn 2 S 4 and UCNPs were assembled on the surface of the ITO electrode. Then Au NPs were dropped, which could facilitate the coupling of CdSe NPs modified DNA1 via Au–S bond, giving an ITO/SnS 2 /ZnIn 2 S 4 /UCNPs/CdSe heterojunction structure. When irradiated with 980 nm near-infrared (NIR) light, the UV–visible light emitted by the UCNPs could excite the nanocomposite, producing an enhanced photoelectric reaction. Subsequently, CEA aptamer and DNA2-modified SiO 2 were added to form a Y-shaped DNA structure. At this time, the photocurrent was significantly reduced by the combination of the light-blocking effect of SiO 2 and the departure of CdSe NPs from the electrode surface. When the target CEA was added, the recognition between CEA and the aptamer led to the collapse of the Y-shaped DNA structure, the restoration of hairpin DNA and the proximity of CdSe to the electrode. Accordingly, the photocurrent signals enhanced again. Under optimal experimental conditions, the detection limit as low as 0.3 pg mL−1 was obtained with good selectivity, achieving a sensitive "on-off-on" photoelectrochemical sensor for CEA detection. [ABSTRACT FROM AUTHOR]

In this work, personal glucose meter (PGM) as a portable electrochemical device was utilized for sensitive detection of non-glucose targets: N-gene and PCB77, respectively. DNA hydrogel, which can respond to CRISPR/Cas system, was prepared for label-free encapsulating invertase. In the presence of targets, the repeated sequence for the activation of Cas12a was obtained due to the performance of RCA. Unlike "one-to-one" recognition, activated Cas12a can efficiently cleave multiple single-stranded linker DNAs on DNA hydrogels, thus releasing many invertase that can be used for PGM detection. With the amplification of RCA and CRISPR/Cas system, high detection sensitivity can be obtained even using portable PGM. The detection limits for N-gene and PCB77 were 2.6 fM and 3.2 × 10−5 μg/L, respectively, with high specificity and good practical application performance. The developed biosensor can be used for online monitoring with the merit of low cost, easy operation and can be used for various targets analysis. A label-free strategy for CRISPR/Cas12a triggered portable PGM sensor was developed for the detection of N-gene and PCB77 using DNA hydrogel encapsulating invertase. [Display omitted] • Portable personal glucose meter was used to detect non-glucose targets. • DNA hydrogel was prepared for label-free encapsulating invertase. • CRISPR/Cas system can efficiently destroy DNA hydrogel and release invertase. • The same crRNA can be used to detect different targets. [ABSTRACT FROM AUTHOR]