Charge Density-Regulated Microchannel-Based Electrochemiluminescence Sensor for Hydrogen Sulfide Detection with a Highly Efficient Accumulation Strategy.

The electrochemiluminescence (ECL) intensity can be regulated by ionic current passing through the microchannel, which broadened the regulation of the ECL sensors. But in the early reported sensors, the electrostatic repulsion and steric hindrance caused few targets to approach the interface of the microchannel driven by concentration difference, which reduced the detection efficiency and prolonged the detection period. In this study, different accumulation strategies, such as a positive electric field and different polarity electric fields, were designed to accumulate targets in the microchannel. The interaction of azide groups and hydrogen sulfide served as a research model. Hydrogen sulfide can react with the negatively charged azide groups in the microchannel surface to produce positively charged amino groups, decreasing the negative charge density of the microchannel and thus altering the ionic current and ECL intensity. The accumulation of hydrogen sulfide at the microchannel tip can increase the collision probability with azide groups to improve the detection efficiency, and the integration of accumulation and reaction can shorten the detection period to 28 min. The hydrogen sulfide concentration on the microchannel tip accumulated by applying different polarity electric fields was 22.3-fold higher than that accumulated by applying a positive electric field. The selected research model broadened the application range of a microchannel-based ECL sensor and confirmed the universality of the microchannel-based ECL sensor.

Photoelectrochemical Sensor for H2S Based on a Lead-Free Perovskite/Metal-Organic Framework Composite.

Halide perovskites have emerged as a highly promising class of photoelectric materials. However, the application of lead-based perovskites has been hindered by their toxicity and relatively weak stability. In this work, a composite material comprising a lead-free perovskite cesium copper iodide (CsCu2I3) nanocrystal and a metal-organic framework (MOF-801) has been synthesized through an in situ growth approach. The resulting composite material, denoted as CsCu2I3/MOF-801, demonstrates outstanding stability and exceptional optoelectronic characteristics. MOF-801 may serve a dual role by acting as a protective barrier between CsCu2I3 nanocrystals and the external environment, as well as promoting the efficient transfer of photogenerated charge carriers, thereby mitigating their recombination. Consequently, CsCu2I3/MOF-801 demonstrates its utility by providing both stability and a notably high initial photocurrent. Leveraging the inherent reactivity between H2S and the composite material, which results in the formation of Cu2S and structural alteration, an exceptionally sensitive photoelectrochemical sensor for H2S detection has been designed. This sensor exhibits a linear detection range spanning from 0.005 to 100 µM with a remarkable detection limit of 1.67 nM, rendering it highly suitable for precise quantification of H2S in rat brains. This eco-friendly sensor significantly broadens the application horizon of perovskite materials and lays a robust foundation for their future commercialization.

Eu MOF-enhanced FeNCD nanozymes for fluorescence and highly sensitive colorimetric detection of tetracycline.

The constrained enzymatic activity and aggregation challenges encountered by small-sized nanozymes pose obstacles to their practical utility, necessitating a strategy to mitigate aggregation and boost enzymatic catalytic efficiency. In this work, a negatively charged Eu MOF was utilized as the encapsulation matrix, encapsulating the small-sized nanozymes FeNCDs into the Eu MOF to synthesize an FeNCDs@Eu MOF. The dispersibility of the encapsulated FeNCDs was increased, and owing to the negative charge of the FeNCDs@Eu MOF, electrostatic pre-concentration of the positively charged target molecule tetracycline (TC) was facilitated, thereby amplifying the enzymatic catalytic efficiency of the FeNCDs. The response of the FeNCDs to TC increased by nearly 6 times upon encapsulation. The TC detection limit (LOD) of the FeNCDs@Eu MOF-based sensor is as low as 11.63 nM. The incorporation of fluorescence detection expanded the linear range of the sensor, rendering it more suitable for practical sample detection.

Nanozyme catalysis pressure-powered intuitive distance variation for portable quantitative detection of H2S with the naked eye.

As a representative gas of food spoilage, the development of rapid hydrogen sulfide (H2S) analysis strategies for food safety control is in great demand. Despite traditional methods for H2S detection possessing great achievements, they are still incapable of meeting the requirement of portability and quantitative detection at the same time. Herein, a nanozyme catalysis pressure-powered sensing platform that enables visual quantification with the naked eye is proposed. In this methodology, Pt nanozyme inherits the catalase-like activity to facilitate the decomposition of H2O2 to O2, which can significantly improve the pressure in the closed container, further pushing the movement of indicator dye. Furthermore, H2S was found to effectively inhibit the catalytic activity of Pt nanozyme, indicating that the catalase-like activity of PtNPs may be regulated by varying concentrations of H2S. Therefore, by utilizing a self-designed pressure-powered microchannel device, the concentration of H2S was successfully converted into a distinct signal variation in distance. The effectiveness of the as-designed sensor in assessing the spoilage of red wine by H2S determination has been demonstrated. It exhibits a strong correlation between the change in dye distance and H2S concentration within the range of 1-250 µM, with a detection limit of 0.17 µM. This method is advantageous as it enhances the quantitative detection of H2S with the naked eye based on the portable pressure-powered sensing platform, as compared to traditional H2S biosensors. Such a pressure-powered distance variation platform would greatly broaden the application of H2S-based detection in food spoilage management.

Screening and Application of DNA Aptamers for Heparin-Binding Protein.

Rapid detection of heparin-binding protein (HBP) is essential for timely intervention in sepsis cases. Current detection techniques are usually antibody-based immunological methods, which have certain problems, such as complexity and slow detection, and fall short in meeting the urgency of clinical needs. The application of an aptamer can address these concerns well. In this study, HBP-specific DNA aptamers were screened first. Among which, Apt-01, Apt-02, and Apt-13 had a high affinity for HBP, exhibiting impressive KD values of 3.42, 1.44, and 1.04 nmol/L, respectively. Then, the aptamer of HBP and its partially complementary primer probe were combined to form double-stranded DNA (dsDNA) and synthesize a circular DNA template. The template is complementary to the primer probe, but due to the presence of dsDNA, ExoIII cleaves C2-13 as an RCA primer probe, rendering the template unable to recognize the primer probe and preventing the RCA reaction from proceeding. When the target is present, it competes with the adapter for recognition and releases C2-13, exposing its 3' end. After initiating the RCA at room temperature and reacting with SYBR GreenII at 37 °C for 20 min, fluorescence changes can be observed and quantitatively analyzed at a 530 nm wavelength, achieving quantitative biological analysis. Apt-01 was used to develop a fluorescent biosensor for HBP detection, which exhibited a good linear range (0.01 nmol/L to 10 nmol/L) and detection limit (0.0056 nmol/L). This advancement holds the potential to lay a solid groundwork for pioneering sensitive and specific methods for HBP detection and to significantly enhance the diagnostic processes for sepsis.

Multicolor Biosensor for Trypsin Detection Based on the Regulation of the Peroxidase Activity of Bovine Serum Albumin-Coated Gold Nanoclusters and Etching of Gold Nanobipyramids.

The detection of trypsin is significantly important for both clinical diagnosis and disease treatment. In this study, an innovative multicolor sensor for trypsin detection has been established based on the regulation of the peroxidase activity of bovine serum albumin-coated gold nanoclusters (BSA-Au NCs) and efficient etching of gold nanobipyramids (Au NBPs). BSA-Au NCs have slight peroxidase enzyme activity and can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate TMB+, while trypsin can hydrolyze BSA ligands on the surface of BSA-Au NCs, thus exposing more catalytic active sites of BSA-Au NCs and resulting in the enhancement of the peroxidase activity of BSA-Au NCs, hence more TMB+ is generated. Under acidic conditions, TMB+ can etch Au NBPs efficiently, consequently affecting the aspect ratio of Au NBPs accompanied by the ultraviolet-visible (UV-vis) spectra blue shifting of the system. Furthermore, this also results in color variations that can be distinguished and recognized by naked eyes without any expensive and sophisticated instruments. This multicolor sensor has an available linear relationship with the logarithm of the trypsin concentration in the range of 0.1-100 µg/mL, and the detection limit is 0.045 µg/mL. The designed sensor has been used to detect the concentration of trypsin in human serum samples from healthy individuals and pancreatitis patients with satisfactory results.

Low-Background Signal-On Homogeneous Electrochemiluminescence Biosensor for Hepatitis B Virus Detection Based on the Regulation of the Length of DNA Modified on the Nanoparticles by CRISPR/Cas12a and Hybridization Chain Reaction.

In this work, combined with the high amplification efficiency of hybridization chain reaction (HCR), high specificity of the CRISPR/Cas12a system, and convenience of the homogeneous electrochemiluminescence (ECL) assay based on the regulation of negative charge on the reporting probes, a sensitive ECL biosensor for hepatitis B virus DNA (chosen as a model target) had been developed. The initiator chain trigger DNA that can induce HCR amplification is modified on the surface of ruthenium bipyridine-doped silica nanoparticles (Ru@SiO2 NPs) first, and large amounts of negative charges modified on the particles were achieved through the HCR amplification reaction. The efficiency of the nanoparticles reaching the negatively charged working electrode can be regulated and realize the change of the ECL signal. In addition, long DNA on the surface of the luminescent body may prevent the coreactant from entering the pore to react with ruthenium bipyridine. These factors combine to produce a low-background system. The presence of the target can activate the CRISPR/Cas12a system and make trigger DNA disappear from the nanoparticle surface, and strong ECL can be detected. The sensor does not require a complex electrode modification; therefore, it has better reproducibility. Additionally, due to dual signal amplification, the sensor has a high sensitivity. In the range of 10 fM to 10 nM, the ECL intensity exhibits a strong linear relationship with the logarithm of the target concentration, and the detection limit is 7.41 fM. This sensor has shown high accuracy in detecting clinical samples, which holds significant potential for application in clinical testing.

Dual Self-Amplification Homogeneous Electrochemiluminescence Biosensor for Terminal Deoxynucleotidyl Transferase Activity Based on Controlling the Surface Morphology and Charge of Reporter Nanoparticles.

Terminal deoxynucleotidyl transferase (TdT) is upregulated in several types of leukemia and is considered a disease biomarker and a potential therapeutic target for leukemia. In this research, a homogeneous electrochemiluminescence (ECL) method based on the control of surface charge and morphology of tris (2,2'-bipyridine) ruthenium(II) chloride hexahydrate-doped silica nanoparticles (Ru@SiO2 NPs) has been designed for TdT activity detection. A small amount of short single-stranded DNA (ssDNA) was modified onto the surface of Ru@SiO2 NPs, and the nanoparticles with a slight positive charge experienced electrostatic attraction with the indium tin oxide (ITO) electrode with a negative charge, so relatively high ECL signals had been detected. Under the action of TdT, the ssDNA was significantly elongated, carrying numerous negative charges on its phosphate backbone, so the overall negative charge of the reporter nanoparticles was enhanced, resulting in a strong electrostatic repulsion with the ITO electrode. Simultaneously, the long ssDNA wrapped around the nanoparticles hindered the approach of the coreactant. Due to the dual effects, the ECL response of the system decreased. The constructed biosensor exhibited excellent sensitivity toward TdT over a range spanning from 1 to 100 U/L. The limit of detection is as low as 1.78 U/L. The developed approach was effectively applied to detect TdT activity in leukemic patients' leukocyte extracts.

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.

Electrochemiluminescence Biosensor for Estrogen-Related Receptor Alpha (ERRα) Based on Target-Induced Change of the Steric Hindrance Effect of an Antibody-Modified Electrode.

In this work, a simple and sensitive electrochemiluminescence (ECL) biosensor has been devised based on target-induced steric hindrance of an antibody-modified electrode surface. Estrogen-related receptor alpha (ERRα) is closely related to estrogen-dependent tumors, which had been chosen as a model target. The ERRα antigen can bind to the antibody modified on the electrode surface with high specificity and results in the increase of steric hindrance, which prevented the ECL indicators (tris(2,2'-bipyridine) dichlororuthenium(II) hexahydrate) from approaching the electrode surface, and the ECL intensity of the system decreased. The ECL response of the system has a good linear relationship with ERRα concentration in the range of 1.0-60 ng/L, and the limit of detection is 0.5 ng/L. Different from the traditional sandwiched immune ECL detection system, which need the modification of ECL indicators on the secondary antibody, only one antibody had been used in this system. The system is easy to operate and has good sensitivity. The designed biosensor has been applied to detect ERRα in the serum and different cell line samples with satisfied results.

KIAA1199 drives immune suppression to promote colorectal cancer liver metastasis by modulating neutrophil infiltration.

BACKGROUND AND AIMS: Metastasis is the primary cause of cancer mortality, and colorectal cancer (CRC) frequently metastasizes to the liver. Our previous studies demonstrated the critical role of KIAA1199 in tumor invasion and metastasis in CRC. In the present study, we described an immune regulatory effect of KIAA1199 that creates a permissive environment for metastasis. APPROACH AND RESULTS: Flow cytometry was used to examine the effects of KIAA1199 on the infiltration of tumor immune cells. Neutrophils and T cells were isolated, stimulated, and/or cultured for in vitro function assays. In the patients with CRC, high expression levels of KIAA1199 were associated with an increased neutrophil infiltration into the liver. This result was further validated in mouse metastasis models. The increased influx of neutrophils contributed to the KIAA1199-driven CRC liver metastasis. Mechanistically, KIAA1199 activated the TGFß signaling pathway by interacting with the TGFBR1/2 to stimulate CXCL1 and CXCL3 production, thereby driving the aggregation of immunosuppressive neutrophils. Genetic blockade or pharmacologic inhibition of KIAA1199 restored tumor immune infiltration, impeded tumor progression, and potentiated response to immune checkpoint blockade (ICB). CONCLUSIONS: These findings indicated that KIAA1199 could facilitate the liver infiltration of immunosuppressive neutrophils via the TGFß-chemokine (C-X-C motif) ligand (CXCL)3/1-CXCR2 axis, which might be clinically targeted for the treatment of hepatic metastasis.

Ultrasensitive photoelectrochemical detection of glutathione based on the multifunctional catalytic properties of phosphotungstic acid.

A novel photoelectrochemical (PEC) sensor was constructed for the highly sensitive detection of reduced glutathione (GSH) based on the multiple catalytic properties of phosphotungstic acid (PTA). In this work, the catalytic properties of PTA were applied to PEC sensing for the first time and interpreted in detail. First, PTA as an electron acceptor can inhibit the complexation of photogenerated electron-hole pairs in p-Cu2O, thus significantly increasing the photogenerated current of p-type semiconductor material Cu2O. Secondly, when GSH is oxidized to oxidized glutathione (GSSG) by photogenerated holes on the photocathode, PTA is able to reduce GSSG to GSH by transferring protons, forming a redox cycle regeneration process of GSH. Finally, the relatively large amount of PTA in the background solution was able to pre-oxidize interfering substances such as L-cysteine and ascorbic acid, which improved the selectivity of the method. Under the optimal experimental conditions, the linear range of the PEC sensor response to GSH was 0.050-100 nmol L-1, with a detection limit as low as 0.017 nmol L-1 (S/N = 3), which can be applied to the detection of GSH content in cell lysate samples.

A photoelectrochemical aptasensor for tetracycline based on the self-assembly of 2D MoS2 on a 3D ZnO/Au/ITO electrode.

Two-dimensional (2D) layered MoS2 has good dispersion and adsorption properties, but being a narrow bandgap semiconductor limits its application in photoelectric sensing. In this study, a homogeneous photoelectrochemical sensor based on three-dimensional (3D) ZnO/Au/2D MoS2 is proposed for the ultrasensitive detection of tetracycline (TET). MoS2 is uniformly embedded on the 3D ZnO/Au surface by ordered self-assembly. The physical method of π-π interaction of MoS2 replaces the conventional use of chemically modifying aptamers on the electrode material surface. Under optimal conditions, this method has been successfully applied to the detection of TET in milk, honey, pig kidney and pork samples with reliable results. We believe that this study presents a method for the preparation of sensing carriers and target detection with great potential for application.

Dual-target nucleic acid sequences responsive electrochemiluminescence biosensor using single type carbon dots as probe for SARS-CoV-2 detection based on series catalytic hairpin assembly amplification.

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) is rampant all over the world, and rapid and effective virus detection is the best auxiliary to curb the spread of the epidemic. A diagnosis can only be made if two or more different nucleic acid sequences are confirmed at the same time, and in most of traditional detection technologies, these target sequences have been detected separately. In this work, an electrochemiluminescent (ECL) biosensor employing a single ECL probe as signal output and responding to dual-target simultaneously is proposed for the first time. Taking the two sequences located in ORF 1ab region and N region of SARS-CoV-2 gene sequence as the model target and nitrogen doped carbon quantum dots (CDs) as ECL beacon, supplemented with catalytic hairpin assembly (CHA) reaction for signal amplification, the presented strategy has been successfully applied to the rapid detection of SARS-CoV-2. The developed SARS-CoV-2 biosensor based on the series CHA systems can realize the quantitative determination of SARS-CoV-2 in the range of 50 fM to 200 pM within 40 min. Moreover, the clinical validity of this method has been verified by the high consistency between the detection results of using this method and those using RT-qPCR for seven clinical pharyngeal swab samples.

Colorimetric and visual determination of uric acid based on decolorization of manganese dioxide nanosheet dispersions.

Serum levels of uric acid (UA) play an important role in the prevention of diseases. Developing a rapid and accurate way to detect UA is still a meaningful task. Hence, positively charged manganese dioxide nanosheets (MnO2NSs) with an average latter size of 100 nm and an ultra-thin thickness of below 1 nm have been prepared. They can be well dispersed in water and form stable yellow-brown solutions. The MnO2NSs can be decomposed by UA via redox reaction, leading to a decline of a characteristic absorption peak (374 nm) and a color fading of MnO2NSs solution. On this basis, an enzyme-free colorimetric sensing system for the detection of UA has been developed. The sensing system shows many advantages, including a wide linear range of 0.10-50.0 µmol/L, a limit of quantitation (LOQ) of 0.10 µmol/L, a low limit of detection (LOD) of 0.047 µmol/L (3σ/m), and rapid response without need of strict time control. Moreover, a simple and convenient visual sensor for UA detection has also been developed by adding an appropriate amount of phthalocyanine to provide a blue background color, which helps to increase visual discrimination. Finally, the strategy has been successfully applied to detect UA in human serum and urine samples.

Ultra-sensitive electrochemiluminescent biosensor for miRNA based on CRISPR/Cas13a trans-cleavage-triggered hybridization chain reaction and magnetic-assisted enrichment.

The great selectivity and trans-cleavage activity of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a had been coupled with high amplification efficiency of hybridization chain reaction (HCR) and magnetic-assisted enrichment, high sensitivity of electrochemiluminescence (ECL) detection to develop an ultra-sensitive biosensor for microRNA-21 (miRNA-21). The CRISPR/Cas13a was used to recognize target RNA with high specificity and performed the trans-cleavage activity. An initiation strand was generated to bind to the probe on the surface of nanomagnetic beads and then trigged HCR to produce long double-strand DNAs (dsDNAs) to realize signal amplification. Ru(phen)32+ can be inserted in the groove of the dsDNAs and acts as the ECL indicator, which can be separated through magnetic enrichment and allowed the platform to reduce the signal background. Under the optimized conditions, there is a good linear correlation between the ECL intensity and the logarithm of miRNA-21 concentration in the range 1 fM-10 nM; the limit of detection (LOD) was 0.53 fM. The proposed system was applied to detect miRNA-21 from the urine of acute kidney injury (AKI) patients with good results.

Competitive substitution in europium metal-organic gel for signal-on electrochemiluminescence detection of dipicolinic acid.

Metal-organic gels (MOGs) emerged as an attractive luminescent soft material for electrochemiluminescence (ECL). In this work, a cathodic ECL-activated europium metal-organic gel (Eu-MOG) has been synthesized by a facile mixing of Eu3+ with 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine (Hcptpy) under mild conditions. The prepared Eu-MOG is highly mesoporous for co-reactant permeation to produce an ultra-stable and high-efficient ECL, based on the antenna effect of Eu3+ coordinating with Hcptpy. Moreover, dipicolinic acid (DPA) can competitively coordinate with Eu3+ instead of water molecules, producing an enhanced ECL signal. Therefore, an ECL enhancement assay was developed for DPA detection. There was a linear relationship between the ECL intensity and the logarithmic concentration of DPA in the 0.01-1 µM range, and the detection limit is 7.35 nM. This work displays the promising application of Eu-MOG in the ECL field, opening a broad inspection for seeking a new generation of ECL luminophores.

Homogeneous Photoelectrochemical Aptasensors for Tetracycline Based on Sulfur-Doped g-C3N4/n-GaN Heterostructures Formed through Self-Assembly.

The complex synthesis of photoelectric materials and the difficulty of fixing the identification elements on the photoelectrode are long-standing problems in the field of photoelectrochemical (PEC) biosensing. In this work, a simple PEC aptasensor construction strategy based on a sulfur-doped g-C3N4 (SCN)/n-GaN heterostructure photoelectrode was proposed. The SCN/n-GaN heterostructure can be formed through self-assembly in solution since SCN can be uniformly dispersed in solution. In addition, as a dual-function mediate, an aptamer can be fixed on an SCN substrate automatically because of the good adsorption performance of SCN. Therefore, tedious steps of PEC electrode preparation and the fixing of recognition elements were both avoided. Compared with the traditional ones, the construction difficulty and time cost of the prepared PEC aptasensors are greatly reduced. The simplified experimental process improves the stability and reproducibility of the aptasensor. Finally, tetracycline (TET) was used as a model target to verify the sensing performance of the proposed PEC strategy. TET can consume the photogenerated holes of the SCN/n-GaN heterostructure, promote carrier migration, and result in the change in the photocurrent. The linear relationship between the change in the photocurrent intensity and the TET concentration can be used to detect TET. The aptasensor has a linear range of 0.10-10.0 nmol L-1 and the detection limit is 0.030 nmol L-1 (3S/N). The aptasensor was applied to the detection of TET in milk samples with satisfactory results.

Ultrasensitive Photoelectrochemical Biosensor for microRNA-155 Based on Energy Transfer between Au Nanocages and Red Emission Carbon Dot-Assembled Nanosheets Coupled with the Duplex-Specific Nuclease Enzyme-Assisted Target Recycling Strategy.

Energy transfer (ET) is an effective tool to construct photoelectrochemical (PEC) biosensors for its high sensitivity. Since the materials to develop ET systems are limited, exploring new and universal ET systems is significant. Herein, new photoactive nanosheets (R-CDs NS) formed by self-assembling of red emission carbon dots (R-CDs) have been synthesized, which exhibit wide visible light absorption and stable photocurrent response and have an obvious sensitization effect for TiO2. Gold nanocages (AuNCs), whose absorption overlap well with the R-CDs' emission, were synthesized and served as PEC quenchers for the photosensitized system that consists of TiO2 and R-CDs. The ET between R-CDs and AuNCs can boost the recombination of photogenerated electron-hole pairs of R-CDs and results in a quenched photocurrent of this system. MicroRNA-155 was chosen as a model target. First, the nanocomposite containing R-CDs NS and AuNCs was prepared through DNA modification and hybridization. In the absence of the target, AuNCs and R-CDs were close enough for ET, with TiO2-modified FTO serving as the working electrode, and a quenched photocurrent was detected. In the presence of the target, the disintegration of the nanocomposite was induced through target hybridization and DNA hydrolyzation, leading to the separation of AuNCs and R-CDs NS, and the ET disappeared and led to a high photocurrent. With duplex-specific nuclease enzyme-assisted target recycling, the high sensitivity enabled the sensor to monitor the target in cancer cells. The sensor has a low detection limit of 71 aM. The sensing platform has high sensitivity, good selectivity, and reproducibility.

Highly Sensitive Photoelectrochemical Biosensor for MicroRNA-21 Based on a Dumbbell-Shaped Heterostructure AuNRs@end-TiO2 Combined with Carbon Dots as Photosensitizers and Duplex-Specific Nuclease-Assisted Signal Amplification.

TiO2 was grown on both ends of gold nanorods (AuNRs) to form a dumbbell-shaped heterostructure (called AuNRs@end-TiO2) first, and then assembled on the fluorine tin oxide (FTO) electrode surface through hydrophobic interactions to construct a concise photoelectrochemical microRNA-21 (miRNA-21, model target) biosensor using carbon dots (CDs) as photosensitizers. Hairpin probes (HPs) were fixed on the AuNRs@end-TiO2-modified FTO electrode surface through the Au-S bond, and CDs-modified complementary DNA (CDs-cDNA) served as photosensitive probes. In the presence of the target, miRNA hybridized with the HP and triggered double-strand-specific nuclease to cleave the complementary part of the HP with miRNA, and miRNA was released, which can trigger another cycle to realize signal amplification. Many HPs were cleaved and the complementary sequence with cDNA was exposed, which can capture the photosensitive probes to the electrode surface and resulted in photocurrent enhancement. The photocurrent intensity system has a linear relationship with the logarithm of the miRNA concentration in the range of 0.1 fM to 100 pM with a low detection limit of 96 aM (S/N = 3). The biosensor has high sensitivity, good selectivity, and good reproducibility and shows satisfactory results in actual sample detection.