Ultrasensitive Photoelectrochemical Biosensor Research Articles

Single-atom ruthenium nanozyme-induced signal amplification strategy in photoelectrochemical aptasensor for ultrasensitive detection of chloramphenicol

To develop ultrasensitive and rapid antibiotics residue detection method is crucial for ensuring food safety and protecting human health. Herein, a novel photoelectrochemical (PEC) aptasensor integrated with single-atom ruthenium (Ru) nanozyme-mediated catalytic precipitation as a valuable signal amplification strategy, have been established for ultrasensitive chloramphenicol (CAP) detection. Particularly, the exceptional peroxidase-mimicking activity of single-atom Ru nanozyme is responsible for accelerating the oxidation of 4-chloro-1-naphthol (4-CN) to produce insoluble precipitate on the electrode, which in turn causes a notable reduction in the photocurrent. Whereas, when CAP is present, the aptamer is liberated away the electrode because of its potent affinity with CAP, resulting in an elevation of the photocurrent signal, enhancing the detection sensitivity. Importantly, the signal amplification strategy combines the effective photoactive material of Au nanoparticles/CdS quantum dot/TiO2 composites, a PEC aptasensor for determination of CAP with an ultralow detection limit of 4.12 pM is achieved in a self-powered mode with great selectivity and accuracy. This work proposes a novel reasonable approach utilizing high-activity single-atom nanozyme to induce signal amplification strategy for the advancement of single-atom nanozyme in ultrasensitive PEC biosensor, and further creates new avenues for ultrasensitive detection beyond antibiotics residue.

Ultrasensitive Photoelectrochemical Biosensor for Dual-miRNAs Detection Based on Molecular Logic Gates and Methylene Blue Sensitized ZnO@CdS@Au Nanorods.

The occurrence of cancer is often closely related to multiple tumor markers, so it is important to develop multitarget detection methods. By the proper design of the input signals and logical operations of DNA logic gates, detection and diagnosis of cancer at different stages can be achieved. For example, in the early stages, specific input signals can be designed to correspond to early specific tumor markers, thereby achieving early cancer detection. In the late stage, logic gates for multitarget detection can be designed to simultaneously detect multiple biomarkers to improve diagnostic accuracy and comprehensiveness. In this work, we constructed a dual-target-triggered DNA logic gate for anchoring DNA tetrahedra, where methylene blue was embedded in the DNA tetrahedra to sensitize ZnO@CdS@Au, achieving ultrasensitive detection of the target substance. We tested the response of AND and OR logic gates to the platform. For AND logic gates, the sensing platform only responds when both miRNAs are present. In the concentration range of 10 aM to 10 nM, the photoelectric signal gradually increases with an increase of the target concentration. Subsequently, we used OR logic gates for miRNA detection. Even if only one target exists, the sensing platform exhibits excellent performance. Similarly, within the concentration range of 10 aM to 10 nM, the photoelectric signal gradually increases with an increase of the target concentration. The minimum detection limit is 1.10 aM. Whether it is the need to detect multiple targets simultaneously or only one of them, we can achieve it by selecting the appropriate logic gate. This strategy holds promising application prospects in fields such as biosensing, medical diagnosis, and environmental monitoring.

An ultrasensitive photoelectrochemical biosensor based on AgBiS2/CdS photoanode and multiple signal amplification strategy for the detection of dibutyl phthalate plasticizer

Herein, a novel AgBiS2/CdS heterojunction was developed for the construction of sensitive biosensor for dibutyl phthalate (DBP) detection. Compared with the pristine CdS, the AgBiS2/CdS heterojunction exhibited enhanced photocurrent because of the promoted photo-carriers transfer due to the matched energy band arrangement between AgBiS2 and CdS. Based on this AgBiS2/CdS photoanode and a signal amplification strategy integrates DNAzyme-assisted walker reaction and hybridization chain reaction, a sensitive PEC sensing platform was designed for the detection of DBP. A wide detection ranges from 1 fM to 10 nM and a low detection limit of 0.3 fM were achieved. The proposed PEC biosensor with satisfactory sensitivity, selectivity, and stability shows potential application in environmental monitoring.

Ultra-sensitive photoelectrochemical biosensor for determination of African swine fever virus based on surface plasmon resonance

Sensitive and specific detection of African swine fever virus (ASFV) is crucial for agricultural production and economic development due to the mortality and infectivity. In this study, a bismuth induced enhanced photoelectrochemical (PEC) biosensor based on in-situ loop mediated isothermal amplification (LAMP) was constructed using deposited bismuth nanoparticles loaded bismuth oxycarbonate (Bi/(BiO)2CO3) as photoactive material, using primers designed according to LAMP as recognition elements, and using in-situ LAMP to achieve nucleic acid amplification of target genes. As the Bi induced surface plasmon resonance (SPR) effect, enhanced light captures and effective electron hole separation, it could effectively enhance the photoelectric activity, so the prepared Bi/(BiO)2CO3 nanohybrid had higher photocurrent intensity and good stability. The constructed PEC biosensor has realized the detection of ASFV in real samples with good sensitivity, specificity and repeatability. In the range from 1.0 × 10−13 to 1.0 × 10−7 g/L, the photoelectric current decreased with the increase of the concentration of ASFV, and the detection limit was 3.0 × 10−14 g/L (about 0.048 copies/μL). Combining the advantages of LAMP with the excellent performance of PEC, it provides a simple, economical and efficient method for nucleic acid diagnosis, and also provides a new idea for biosensor detection.

Ultrasensitive photoelectrochemical biosensor amplified by target induced assembly of cruciform DNA nanostructure for the detection of dibutyl phthalate

In this work, an ultra-sensitive signal quenched photoelectrochemical (PEC) aptasensor for dibutyl phthalate (DBP) detection was constructed by using a target induced cruciform DNA structure as signal amplifier and g-C3N4/SnO2 composite as signal indicator. Impressively, the designed cruciform DNA structure shows high signal amplification efficiency due to the reduced reaction steric hindrance because of its mutually separated and repelled tails, multiple recognition domains, and a fixed direction for the sequential identification of the target. Therefore, the fabricated PEC biosensor demonstrated a low detection limit of 0.3 fM for DBP in a wide linear range of 1 fM to 1 nM. This work offered a novel nucleic acid signal amplification approach for enhancing the sensitivity of PEC sensing platforms for the detection of phthalates (PAEs)-based plasticizer, laying the foundation for its utilization in the determine of real environmental pollutants.

Metal Porphyrin Complex Combined with Polymerization and Isomerization Cyclic Amplification for a Sensitive Photoelectrochemical Assay.

5,10,15,20-Tetrakis(4-aminophenyl)-21H,23H-porphine (TPAPP) possesses good light-harvesting ability and photoelectrochemical (PEC) cathode response signal; however, the disadvantages of easy stacking and weak hydrophilicity limit its application as a signal probe in PEC biosensors. Based on these, we prepared a Fe3+ and Cu2+ co-coordinating photoactive material (TPAPP-Fe/Cu) with horseradish peroxidase (HRP)-like activity. The metal ions in the porphyrin center not only enabled the directional flow of photogenerated electrons between electron-rich porphyrin and positive metal ions within inner-/intermolecular layers but also accelerated electron transfer through a synergistic redox reaction of Fe(III)/Fe(II) and Cu(II)/Cu(I) as well as rapid generation of superoxide anion radicals (O2-•) by mimicking catalytically produced and dissolved oxygen, thereby providing the desired cathode photoactive material with extremely high photoelectric conversion efficiency. Accordingly, by combining with toehold-mediated strand displacement (TSD)-induced single cycle and polymerization and isomerization cyclic amplification (PICA), an ultrasensitive PEC biosensor was constructed for the detection of colon cancer-related miRNA-182-5p. The ultratrace target could be converted to abundant output DNA by TSD possessing the desirable amplifying ability to trigger PICA for forming long ssDNA with repetitive sequences, thus decorating substantial TPAPP-Fe/Cu-labeled DNA signal probes for producing high PEC photocurrent. Meanwhile, the Mn(III) meso-tetraphenylporphine chloride (MnPP) was embedded in dsDNA to further exhibit a sensitization effect toward TPAPP-Fe/Cu and an acceleration effect analogous to that of metal ions in the porphyrin center above. As a result, the proposed biosensor displayed a detection limit as low as 0.2 fM, facilitating the development of high-performance biosensors and showing great potential in early clinical diagnosis.

Dual-sensitized heterojunction PDA/ZnO@MoS2 QDs combined with multilocus domino-like DNA cascade reaction for ultrasensitive photoelectrochemical biosensor

In this work, by integrating with a highly efficient multilocus domino-like cascade reaction on DNA nanonet, an ultrasensitive PEC biosensor based on dual-sensitized PDA/ZnO@MoS2 QDs photoactive material as signal probe was proposed for detection of miRNA-182-5p. The dual-sensitized PDA/ZnO@MoS2 QD composed by both of p-n and S-scheme heterojunctions on electrode generated an extremely high initial PEC signal, which however quenched by CdTe QDs decorated on DNA nanonet owing to the significant p-n quenching effect. Thereafter, the output DNA (RS) from DSN enzyme-assisted target recycling amplification triggered an ingenious multilocus domino-like DNA cascade reaction on DNA nanonet for releasing numerous CdTe QDs. Thanks to the multilocus domino-like mode that owned abundant binding sites for increasing trigger efficiency and drove cascade reaction automatically advance along four stated pathways, the target conversion rate could be improved effectively compared with that of traditional approaches, significantly enhancing the detection sensitivity. Consequently, the developed PEC biosensor exhibited a low detection limit to 0.17 fM, providing a new avenue for sensitive, fast and reliable sensing of various DNA/RNA.

Ultrasensitive photoelectrochemical biosensor for DNA 5-methylcytosine analysis based on co-sensitization strategy combined with bridged DNA nanoprobe

Altered DNA methylation in the form of 5-methylcytosine (5-mC) patterns is correlated with disease diagnosis, prognosis, and treatment response. Therefore, accurate analysis of 5-mC is of great significance for the diagnosis of diseases. Here, an efficient enhanced photoelectrochemical (PEC) biosensor was designed for the quantitative analysis of DNA 5-mC based on a cascaded energy level aligned co-sensitization strategy coupling with the bridged DNA nanoprobe (BDN). Firstly, Au nanoparticle/graphite phase carbon nitride/titanium dioxide (AuNPs/g-C3N4@TiO2) nanocomposite was synthesized through in situ growth of AuNPs on g-C3N4@TiO2 surface as a matrix to provide a stable background signal. Next, BDN with a high mass transfer rate synthesized from a pair of DNA tetrahedral as nanomechanical handles was used as a capture probe to bind to the target sequence. The polydopamine nanosphere was applied to load with CdTe QDs (PDANS-CdTe QDs) as a photocurrent label of 5-mC antibodies. When the 5-mC existed, a large number of PDANS-Ab-CdTe QDs were introduced to the electrode surface, the formed CdTe QDs/AuNPs/g-C3N4@TiO2 co-sensitive structure could effectively enhance the electron transfer capability and photocurrent response rate due to the effective cascade energy level arrangement, leading to a significantly enhanced photocurrent signal. The proposed PEC biosensor manifested a wide range from 10−17 M to 10−7 M and a detection limit of 2.2 aM. Meanwhile, the excellent performance indicated the practicability of the designed strategy, thus being capable of the clinical diagnosis of 5-mC.

Ultrasensitive photoelectrochemical biosensor based on black/red phosphorus heterojunction@Bi2Te3 hybrid and enzymatic signal amplification for the detection of colorectal cancer-related piRNA-823

Piwi-interacting RNAs (piRNAs) are a class of noncoding small RNAs that have been identified as promising biomarkers for cancer detection. However, the development of emerging detection methods for piRNAs has not attracted widespread attention. In this work, we proposed an ultrasensitive photoelectrochemical (PEC) biosensor that combines photosensitive hybrid with enzymatic signal amplification strategy for detecting colorectal cancer (CRC)-related piRNA-823. The synergy of the type-II heterostructure between red phosphorus (RP) and black phosphorus (BP), the photothermal effect of BP, and the excellent electron transfer capability and thermoelectric effect of Bi2Te3 endowed the BP/RP heterojunction@Bi2Te3 hybrid with excellent photoelectric conversion performance. The connection of the poorly conductive composite probe system (SiO2-COOH-p2-p1) significantly reduced the photocurrent. The target triggered the release of SiO2-COOH-p2 from the electrode surface and the subsequent specific cleavage of p1 by duplex-specific nuclease, which significantly restored the photocurrent. The released target could react with other composite probes to form a photocurrent signal-increasing cycle. The PEC biosensor showed a linear detection range of 0.1–106 fM and a calculated detection limit of 0.016 fM. In addition, the PEC biosensor exhibited a stable photocurrent response under continuous on-off irradiation and could clearly distinguish the target from the mismatch sequences. The accuracy of the PEC biosensor in detecting piRNA-823 in clinical serum samples was verified by RT–qPCR, and the PEC biosensor could distinguish healthy controls from CRC patients. This work provides a new strategy for ultrasensitive liquid biopsy of piRNAs.

Ultrasensitive Photoelectrochemical Biosensor for DNA 5-Methylcytosine Analysis Based on Co-Sensitization Strategy Combined with Bridged DNA Nanoprobe

Ultrasensitive Photoelectrochemical Biosensor for DNA 5-Methylcytosine Analysis Based on Co-Sensitization Strategy Combined with Bridged DNA Nanoprobe

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.

Photoelectrochemical biosensor for 1,4-dihydroxybenzene based on copper sulfide and horseradish peroxidase enzyme: Application in skin cream samples

This work presents the development and application of an ultrasensitive photoelectrochemical biosensor based on copper (I) sulfide (Cu2S) and horseradish peroxidase enzyme (HRP) immobilized on a fluorine-doped tin oxide modified glass slide (FTO) for the determination of 1,4-dihydroxybenzene (DHB). The Cu2S/FTO photoelectrochemical platform was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical properties of the proposed photoelectrochemical biosensor (HRP-Cu2S/FTO) were evaluated by electrochemical impedance spectroscopy (EIS) and amperometry. The photocurrent of the photoelectrochemical platform was amperometrically monitored, using a commercial 20 W white LED light bulb as the source of light. After optimization of experimental parameters, the biosensor had shown good responses for detection of DHB, in the presence of 50 µmol L−1 of hydrogen peroxide, exhibiting a wide linear range for DHB concentrations between 10 nmol L−1 up to 1 mmol L−1 (r2= 0.998), with a detection limit of 4.0 nmol L−1. The selectivity of the photoelectrochemical biosensor was also evaluated and the results demonstrated that the proposed biosensor presents a good selectivity for DHB detection. The HRP-Cu2S/FTO photoelectrochemical biosensor was applied in skin cream samples presenting recovery percentages for the analyte in the samples between 99.89 and 100.70%, suggesting a good accuracy for the proposed method.

A novel ultrasensitive photoelectrochemical biosensor for detecting microRNA 21 based on cosensitization strategy and p-n heterojunction quenching mode

Highly sensitive detection of biomarkers has a vital role in clinical diagnosis and disease treatment. Integrating cosensitization strategy and p-n heterojunction quenching mode, we have established a novel ultrasensitive “signal off” photoelectrochemical (PEC) biosensor for detecting microRNA 21 (miRNA 21) via target-triggered catalytic hairpin assembly (CHA) cycling amplification. The n-type nano-hybrid (Bi2S3-ZnS) wrapped by toluidine blue O dye (TBO@Bi2S3-ZnS composite) has been synthesized, in which TBO and Bi2S3 as photosensitizers for photoactive matrix of ZnS. Since the cosensitization effect of Bi2S3 and TBO, 136-fold enhancement in PEC signal of TBO@Bi2S3-ZnS has been acquired compared with ZnS. Trace miRNA 21 can be transformed to abundant p-type copper sulfide (CuS) labeled signal tags to form p-n heterojunction with TBO@Bi2S3-ZnS, leading to obvious quenching effect. Thus, the PEC signals decrease with the increasing concentration of miRNA 21 and achieve the quantitative detection. The proposed PEC biosensor exhibits good linear relationship to miRNA 21 ranging from 1.0 × 10−17 to 1.0 × 10−11 mol·L−1 with a limit of detection of 3.3 × 10−18 mol·L−1. This biosensor based on TBO used as photosensitizer for the first time may offer new opportunities for detecting other biomarkers and facilitate the application of organic dyes in PEC sensing field.

Highly sensitive photoelectrochemical biosensor for microRNA159c detection based on a Ti3C2:CdS nanocomposite of breast cancer

Herein, an ultra-sensitive photoelectrochemical biosensor based on Ti3C2:CdS nanocomposite was established for the selective detection of microRNA159c. Ti3C2:CdS nanocomposites were used as optoelectronic materials because Ti3C2:CdS interaction effectively separates photogenerated electrons and holes, and significantly improves the high photoelectric conversion efficiency. Firstly, Ti3C2:CdS nanocomposite was deposited on the surface of the fluorine-doped tin oxide (FTO) electrode. After the chitosan (CS) was dropped, the SH-miRNA were bonded on the electrode surface via the S–Cd bond. Then 6-mercaptohexanol (MCH) blocked the unbound site, the DNA strand was introduced to hybridize with the target SH-miRNA. At this time, the obtained photocurrent gradually decreases. Subsequently, the photosensitizer TMPyP as signal amplification was modified, the photocurrent increased significantly. The target SH-miRNA was detected based upon the photocurrent change originated from quantities change of TMPyP. Working under the best experimental conditions, the sensing platform had good stability, selectivity, and high sensitivity. The detection range for miRNA159c was 1.0 × 10−6-1.0 × 10−13 mol·L-l, and the detection limit was approximately 33 fmol·L-l. The detection of miRNA159c in human serum provided a huge opportunity to explore the relationship between the abundance of this miRNA and the incidence of breast cancer (BC), and to further achieve effective detection of BC.

L-phenylalanine-imprinted polydopamine-coated CdS/CdSe n-n type II heterojunction as an ultrasensitive photoelectrochemical biosensor for the PKU monitoring

A simple and highly sensitive photoelectrochemical biosensor towards L-phenylalanine, as a kind of typical essential amino acid and phenylketonuria biomarker was developed on a surface molecular imprinted (MIP) polydopamine-coated CdS/CdSe/Zn heterojunction. Hierarchical marigold flower-like Zn layer decorated by n-type dichalcogenides interfacial heterojunction was successfully designed and synthesized on Ti foil for PEC converter by in situ electrodeposition. A visible-light-driven molecular imprinting film was prepared through the electropolymerization of dopamine in the presence of L-Phe as biomarker. The combination of bio-MIP and photoelectrochemistry overcomes the defects of the PEC method, which is the absence of selectivity, and offers a new PEC sensor with high sensitivity and selectivity based on visible-light-driven heterojunction and biopolymer-enhanced strategy. The unique interfacial between the Zn marigold flower layer as low work function support and CdS/CdSe n-n heterojunction as well as n-type characteristics of polydopamine imprinted by L-Phe biomarker drastically increase the light trapping and absorption in the visible range, and dramatically inhibit the charge carrier recombination, which is crucial for boosting the Bio-PEC activity. Photocatalytic, electrocatalytic and physicochemical properties of the above-mentioned layers were fully characterized. As-prepared PEC biosensor displayed superb performance for the detection of L-Phe biomarker in the optimized condition obtained from central composite design modeling, showing two linear range 0.005–2.5 and 2.5–130 μM and a low detection limit of 0.9 nM. This work suggests that such L-Phe-imprinted polydopamine-coated Zn/CdS/CdSe heterojunction is greatly promising for being applied in photoelectrochemical biosensing with high photo-electron conversion efficiency.

Dependent signal quenching and enhancing triggered by bipedal DNA walker for ultrasensitive photoelectrochemical biosensor

Herein, by utilizing bipedal DNA walker as booster to adjust the distance of quencher ferrocene (Fc) and sensitizer methylene blue (MB) to photoactive material perylene-3,4,9,10-tetracarboxylic acid (PTCA), a novel “on-off-super on” photoelectrochemical (PEC) biosensor was proposed for ultrasensitive detection of thrombin (TB). Firstly, the PTCA matrix on electrode could provide a high initial PEC signal assisted by depAu. Upon the Fc labeled on hairpin DNA 1 (H1-Fc) proximate to PTCA, the PEC signal could obviously decrease to reduce the background signal. Interestingly, the target TB-related bipedal DNA walker implemented the opening of H1-Fc for the departure of Fc toward PTCA, which achieved the recovery of PEC signal and exposed the prelocked toehold domain for the hybridization with hairpin DNA 2 labeled with MB (H2-MB), thereby making the MB approach to PTCA for achieving the “super on” signal. As a result, this proposed strategy showed a wide linear range from 0.5 fM to 100 nM with a low detection limit down to 0.17 fM for TB detection, providing an efficient and available avenue for sensitive detection of biomolecules in bioanalysis and disease diagnosis.

Ultrasensitive photoelectrochemical biosensor for MiRNA-21 assay based on target-catalyzed hairpin assembly coupled with distance-controllable multiple signal amplification.

Here, with the target-catalyzed hairpin assembly generated dsDNA (HP1-HP2) to synchronously control the departure of quencher ferrocene and approach of sensitizer methylene blue, a distance-controllable multiple signal amplification based photoelectrochemical biosensor was proposed for MiRNA-21 assay.

An ultrasensitive photoelectrochemical biosensor for glucose based on bio-derived nitrogen-doped carbon sheets wrapped titanium dioxide nanoparticles

In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed from the bio-derived nitrogen-doped carbon sheets (NDC) wrapped titanium dioxide nanoparticles (NDC-TiO2 NPs) followed by the covalent immobilization of glucose oxidase (GODx) on them (designated as a GODx/NDC-TiO2NPs/ITO biosensor). Initially, the TiO2 NPs was synthesized by sol-gel method and then NDC-TiO2 NPs was synthesized utilizing a green source of Prunus persica (peach fruit) through a simple hydrothermal process. The synthesized NDC-TiO2 NPs composite was characterized by FESEM, HRTEM, Raman spectroscopy, XRD, ATR-FTIR spectroscopy and XPS to determine composition and phase purity. These fabricated GODx/NDC-TiO2NPs/ITO biosensor exhibited a good charge separation, highly enhanced and stable photocurrent responses with switching PEC behavior under the light (λ > 400 nm). As a result, GODx/NDC-TiO2NPs/ITO PEC glucose sensor exhibits a good photocurrent response to detection of glucose concentrations (0.05–10 μM) with an ultra-low detection limit of 13 nM under optimized PEC experimental conditions. Also, the PEC glucose sensor revealed a high selectivity, good stability, long time durability, and capability to analyze the glucose levels in real human serum. Also, the further development of this work may provide new insights into preparing other bio-derived carbon nanostructure-based photocatalysts for PEC applications.

An ultrasensitive photoelectrochemical biosensor based on [Ru(dcbpy)2dppz]2+/Rose Bengal dyes co-sensitized fullerene for DNA detection

Though preferable progresses have been achieved to improve the photoelectric performance of fullerene (C60 NPs) by sensitized structure in photoelectrochemical (PEC) field, further application inevitably suffers from the inherent scarcities of heavy metal-involved quantum dots as sensitizers containing restricted sensitization effect, complex preparation and biological toxicity. In this work, a PEC biosensor based on [Ru(dcbpy)2dppz]2+/Rose Bengal dyes co-sensitized C60 NPs was constructed for ultrasensitive DNA (a fragment sequence of p53 gene) detection. With the merits of low toxicity and accessible operation, [Ru(dcbpy)2dppz]2+/Rose Bengal dyes exhibited a further sensitization efficiency towards C60 NPs. Through modifying wide band gap C60 NPs with two narrower band gap dyes ([Ru(dcbpy)2dppz]2+ and Rose Bengal) to form a cascade-type energy band structure, the photoelectric conversion of C60 NPs was significantly improved and the visible light absorption was markedly promoted, leading to an exceptional photocurrent signal. Additionally, Nt.BstNB I enzyme-assisted target recycling amplification was employed to convert a limited quantity of target to numerous SiO2 NPs-labeled DNA sequences (the signal quencher), resulting in a sharp decrement of photocurrent since a dramatic increment of steric hindrance on the modified electrode surface, which was performed to quantitatively estimate target. The proposed PEC biosensor for DNA detection possessed a wide linear range from 0.1 fM to 1 nM with a calculated detection limit of 37 aM. This work opened up an intriguing avenue for determination of various targets such as DNAs, microRNAs and proteins, and exhibited desirable application potential in the clinic researches, cancer therapies and other related subjects.

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 lowsensitivity 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.