Photoelectrochemical Biosensing Platform Research Articles

A novel photoelectrochemical biosensing platform utilizing dual Type-II Bi2O3/CdLa2S4/Bi2S3 ternary heterojunctions as signal transduction materials and Cu2O nanosphere as a sensitizer for CA15-3 detection

Sensitive detection of CA15-3 is important for postoperative monitoring and early diagnosis of breast cancer. In this work, a photoelectrochemical (PEC) biosensing platform was constructed of CA15-3 by using Bi2O3/CdLa2S4/Bi2S3 ternary type-II heterojunction as the photoactive transduction material for sensitive detection, and the raspberry-shaped Cu2O nanospheres were exploited as the signal sensitizing tags. On one hand, the use of Bi2S3 as a sensitizer can effectively enhance the visible light excitation of the substrate material. On the other hand, Bi2S3 and Bi2O3/CdLa2S4 have the ability to create dual type-II heterojunctions with matched energy levels, which significantly enhances the separation and migration efficiency of the photogenerated carriers and effectively suppresses the recombination of the e-/h+ pairs. Raspberry-like semiconducting Cu2O nanospheres can mediate the PEC process of the heterojunctions. An immunosensor was developed combining the signal transduction capacity of ternary heterojunction and the signal sensitizing effect of Cu2O nanospheres. The proposed PEC immunosensor showed good selectivity and stability for detecting CA15-3 (0.001 ∼ 100 U/mL) with a detection limit of 0.0003 U/mL (S/N = 3). The constructed PEC immunosensor had potential applications in the clinical detection of CA15-3, and was expected to play a great role in the early diagnosis of breast cancer in the future. Moreover, in the design engineering of photoactive materials, the improvement of visible excitation and the enhancement of carrier separation efficiency have been realized simultaneously using a single material, which provides new ideas for the design of photoactive materials.

Detection of biological loads in sewage using the automated robot‐driven photoelectrochemical biosensing platform

AbstractReal‐time polymerase chain reaction (RT‐PCR) remains the most prevalent molecular detection technology for sewage analysis but is plagued with numerous disadvantages, such as time consumption, high manpower requirements, and susceptibility to false negatives. In this study, an automated robot‐driven photoelectrochemical (PEC) biosensing platform is constructed, that utilizes the CRISPR/Cas12a system to achieve fast, ultrasensitive, high specificity detection of biological loads in sewage. The Shennong‐1 robot integrates several functional modules, involving sewage sampling and pretreatment to streamline the sewage monitoring. A screen‐printed electrode is employed with a vertical graphene‐based working electrode and enhanced with surface‐deposited Au nanoparticles (NPs). CdTe/ZnS quantum dots (QDs) are further fabricated through the double‐stranded DNA (dsDNA) anchored on Au NPs. Using the cDNA template of Omicron BA.5 spike gene as a model, the PEC biosensor demonstrates excellent analytical performance, with a lower detection limit of 2.93 × 102 zm and an outstanding selectivity at the level of single‐base mutation recognition. Furthermore, the rapid, accurate detection of BA.5 in sewage demonstrates the feasibility of the PEC platform for sewage monitoring. In conclusion, this platform allows early detection and tracking of infectious disease outbreaks, providing timely data support for public health institutions to take appropriate prevention and control measures.

Carbon quantum dots(CQDs)-sensitized CdS/CuInS2 heterojunction as a photoelectrochemical biosensing platform for highly sensitive detection of prostate-specific antigen

Sensitive and quantitative detection of prostate-specific antigen (PSA) has been determined to be indispensable for clinical diagnostics of prostate cancer, whereas such detection is quite challenging due to the extremely low concentration of biomarkers in human serum samples. In this study, a photoelectrochemical (PEC) sensor was effectively developed for the high-sensitivity analysis of prostate-specific antigen (PSA) using a signal amplification method utilizing sensitized carbon quantum dots (CQDs). In this experiment, cadmium sulfide quantum dots were employed as the substrate materials, and indium copper sulfide quantum dots were loaded on their surfaces. Moreover, the efficient matching of energy levels in these two materials contributed to the generation of photocurrents. The aforementioned heterojunction semiconductor QDs were thus combined with CQDs to produce CQDs on their surfaces. As a result of the presence of CQDs, the ability of heterojunction materials to absorb light was remarkably enhanced, increasing the photocurrent by over ten times. Consequently, in this study, CQDs were combined with PEC sensors, and the developed PEC biosensors exhibited excellent optical performance, sensitivity, repeatability, and stability. The results obtained from the analysis of actual samples were satisfactory and have promising application prospects.

Universal photoelectrochemical aptasensing platform for antibiotic based on CuInS2/rGO and triplex DNA

In this work, a universal and convenient photoelectrochemical (PEC) biosensor was proposed to detect antibiotic on the basis of CuInS2/rGO and triplex DNA molecular switch. High performance photoactive structure was formed via p-type CuInS2 nanosphere complexed with rGO, which was employed to enhance the cathode photocurrent. Capture probe (CP) was conjugated onto the photoactive interface through covalent bonding. In the absence of target, the triplex DNA (THMS) was in a closed state. After introducing a target, the interaction between the target and the specific ring part DNA fragment leaded to the dissociation of the THMS and thereby liberated the single strand DNA (SP). The above identification process was completed in the homogeneous solution. Then, SP was captured to the electrode by CP and hybridized to form dsDNA. The steric effect of dsDNA hindered the interfacial charge transfer, resulting in signal-off photocurrent output. By only altering the specific loop section sequence of THMS, different targets can release the same SP, and can be detected on the same sensing platform under the same testing conditions. As proof of principle, three kinds of antibiotics amoxicillin (AMOX), ampicillin (AMP) and tobramycin (TOB) was detected, achieving limit of detection values of 3.17 pM, 0.63 nM and 2.81 fM, respectively. This approach was also used to detect antibiotic residues in food and environmental samples, which provides a promising paradigm for developing universal, high-performance and convenient PEC biosensing platform.

ZIF-67 Anchored on MoS2/rGO Heterostructure for Non-Enzymatic and Visible-Light-Sensitive Photoelectrochemical Biosensing.

Graphene and graphene-like two-dimensional layered nanomaterials-based photoelectrochemical (PEC) biosensors have recently grown rapidly in popularity thanks to their advantages of high sensitivity and low background signal, which have attracted tremendous attention in ultrahigh sensitive small molecule detection. This work proposes a non-enzymatic and visible-light-sensitive PEC biosensing platform based on ZIF-67@MoS2/rGO composite which is synthesized through a facile and one-step microwave-assisted hydrothermal method. The combination of MoS2 and rGO could construct van der Waals heterostructures, which not only act as visible-light-active nanomaterials, but facilitate charge carriers transfer between the photoelectrode and glassy carbon electrode (GCE). ZIF-67 anchored on MoS2/rGO heterostructures provides large specific surface areas and a high proportion of catalytic sites, which cooperate with MoS2 nanosheets, realizing rapid and efficient enzyme-free electrocatalytic oxidation of glucose. The ZIF-67@MoS2/rGO-modified GCE can realize the rapid and sensitive detection of glucose at low detection voltage, which exhibits a high sensitivity of 12.62 μAmM-1cm-2. Finally, the ZIF-67@MoS2/rGO PEC biosensor is developed by integrating the ZIF-67@MoS2/rGO with a screen-printed electrode (SPE), which exhibits a high sensitivity of 3.479 μAmM-1cm-2 and a low detection limit of 1.39 μM. The biosensor's selectivity, stability, and repeatability are systematically investigated, and its practicability is evaluated by detecting clinical serum samples.

Efficient sensitization of CdTe QDs towards PTCDA for sensitive photoelectrochemical Hg2+ assay.

Herein, a sensitive photoelectrochemical (PEC) biosensor was designed for the detection of mercury ions (Hg2+) on the basis of the efficient sensitization of cadmium telluride quantum dots (CdTe QDs) towards 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and the significant quenching ability of a thymine-Hg2+-thymine (T-Hg2+-T) structure. The proposed CdTe QD/PTCDA sensitized structure was successfully constructed via continuous incubation of PTCDA and CdTe QDs on the glassy carbon electrode (GCE) interface, which embraced strong light absorption capacity and high carrier separation efficiency, giving rise to a remarkably improved initial photocurrent response. Notably, the PEC signal generated from the CdTe QD/PTCDA sensitized structure was almost fivefold higher than that of PTCDA owing to the efficient sensitization of CdTe QDs towards PTCDA. Once target Hg2+ ions were added, a T-rich S1 strand modified on the surface of 1-hexanethiol (HT)/S1/gold nanoparticles (Au NPs)/CdTe QDs/PTCDA/GCE immediately reacted with Hg2+ to produce multiple stable T-Hg2+-T structures. Therefore, the initial PEC signal would be considerably quenched by a high steric hindrance effect derived from the T-Hg2+-T structures. As a result, a quenched PEC response could achieve the detection of Hg2+ in concentrations ranging from 100 fM to 1000 nM. More importantly, the combination of the CdTe QDs/PTCDA sensitization structure and the T-Hg2+-T structure paves a promising pathway to developing a novel PEC biosensing platform for Hg2+ detection and also provides a favorable strategy for monitoring environmental pollution related to Hg2+.

Integrating multiple probes for simplifying signal-on photoelectrochemical biosensing of microRNA with ultrasensitivity and wide detection range based on biofunctionalized porous ferroferric oxide and hypotoxic quaternary semiconductor

A facile and signal-on photoelectrochemical (PEC) biosensing strategy was designed based on hypotoxic Cu2ZnSnS4 NPs nanoparticles (NPs) and biofunctionalized Fe3O4 NPs that integrated recognition units with signal elements, without the need for immobilization of probes on the electrode. Cu2ZnSnS4 NPs were used as the PEC substrate to produce intensive and stable photocurrent. The porous magnetic Fe3O4 NPs displayed favorable loading capacity for CdS QDs and easy biofunctionalization by negatively charged capture DNA (cDNA). cDNA sealed the pore of Fe3O4 NPs, avoiding the escape of CdS QDs as a PEC sensitizer. After hybridizing with target microRNA (miRNA), cDNA split away off Fe3O4 NPs whose porous channel might open and release sealed CdS QDs (signal element), resulting in a dramatical enhancement of PEC response. Herein, miRNA hardly contacted with CdS QDs, effectively avoiding harm to the target miRNA. This proposed strategy simplified procedures of assembly and made the biorecognition process sufficient for promoting a stationary quantity of probes, which was expected to obtain satisfactory performance for bioassay. Using miRNA-155 as a model analyte and combining with duplex-specific nuclease (DSN)-assisted amplification, a simplified and signal-on PEC biosensing platform for miRNA-155 with wonderful performance was proposed. DSN-assisted amplification further promoted PEC signal increment, leading to ulteriorly improving sensitivity (detection limit of 0.17 fM) and linear range (6.5 orders of magnitude) for miRNA-155 assay. Moreover, the developed PEC biosensing platform exhibited satisfactory stability, excellent specificity, and favorable accuracy for miRNA-155, which would have a promising prospect for monitoring miRNA expression in tumor cells.

A self-powered photoelectrochemical biosensing platform for H-FABP monitoring mediated by CsPbBr3@COF–V

Advanced bioelectronic detection based on the integration of modern optical electronics and biological systems has a broad prospect. The strategy of cathode signal amplification in self-powered photoelectrochemical (PEC) immunosensors with excellent performance is rarely reported in the field of immune analysis. Herein, the work demonstrates a self-powered PEC biosensor formed with BiOI photocathode and WO3/SnS2/ZnS photoanode, and CsPbBr3@COF–V was used as the photocathode signal quenching source for the quantitative monitoring of heart fatty acid binding protein (H-FABP). The high efficiency and stable self-powered biosensor formed not only provides continuous and powerful photocurrent response for bioanalysis through reasonable stepped band structure, but also effectively eliminates the interference of reducing substances. The quenching source CsPbBr3@COF–V greatly affects the photocurrent response due to steric hindrance, weak conductivity, competition with the substrate for dissolved oxygen and excitation light source. And the intervention of this key factor achieves multiple signal amplification effect and opens up an innovative vision for self-powered PEC immunosensor. Taking H-FABP as a representative analyte, the proposed signal amplification self-powered photoelectrochemical presents a broad linear range from 0.0005 to 150 ng/mL with the detection limit of 0.19 pg/mL.

A multifunctional photoelectrochemical biosensing platform based on CdS QDs@TiO2-sensitizing Ni-TBAPy-SC coupled with multiple amplification for detection of HBV and thrombin

A multifunctional photoelectrochemical (PEC) biosensor using CdS quantum dots (QDs)-sensitized nickel-metal organic frameworks (MOFs) coupled with multiple amplification techniques was developed for detection of hepatitis B virus (HBV) and thrombin (TB). The tetra (p-benzoate) pyrene (TBAPy)Ni-SC was firstly modified on the electrode and showed an ultra-stable anodic photocurrent with excellent reproducibility. Subsequently AgInS2 QDs were attached to the electrode to much decrease the background signal and improved the assay sensitivity. Moreover, an effective PEC sensitizing probe was specifically designed by connecting a large number of CdS QDs onto TiO2 nanoparticles (NPs). After HBV target induced cyclic amplification to produce abundant output DNA, the CdS QDs@TiO2 signal probes were attached to the electrode by DNA hybridization, which turned the PEC signal of Ni-TBAPy-SC “on”, thus achieving sensitive detection of HBV. In addition, the CdS QDs@TiO2 nano-signal probe is released while target thrombin specifically binds to its aptamer, turning the PEC signal of Ni-TBAPy-SC “off” for thrombin detection. This work has developed a novel QD-sensitized Ni-TBAPy-SC PEC biosensor, which is able to rapidly detect dual targets and avoid false results, showing important value for early diagnosis of diseases.

In situ generated PANI promoted flexible photoelectrochemical biosensor for ochratoxin A based on GOx-stuffed DNA hydrogel as enhancer

Aflexible photoelectrochemical (PEC) biosensor isproposed for the sensitive detection of ochratoxin A (OTA) based on glucose oxidase (GOx)-encapsulated target-responsive hydrogel, using Fenton reaction-mediated in situ formation of polyaniline (PANI) as signal amplified strategy. The target-responsive DNA hydrogels with high loading capacity can carry a large amount of GOx, which not only avoids laborious labeling process but also enhances the analytical performance. Upon introduction of target molecules, the hydrogel can be opened, and multiple GOx was released, thus producing lots of H2O2 via catalytic reduction of glucose. As a component of the Fenton reagent, H2O2 can react with the Fe2+ on the graphene oxidase-PAMAM-Fe2+ (GO-PAMAM-Fe2+) to generate Fe3+ and ·OH. This in turn can oxidize aniline and generate polyaniline (PANI), resulting in the enhancement of the photocurrent signal of GO-MoS2-CdS photoelectrode. The GO-PAMAM-Fe2+ as the neighborhood component of GO-MoS2-CdS-based photoactive material not only can increase the loading amount of Fe2+, but also can inhibit the decrease of photocurrent of GO-MoS2-CdS by direct modification of Fe2+ on the photoactive material. Moreover, the high loading capacity of DNA hydrogel can efficiently promote the performance of the PEC biosensor. The PEC biosensor exhibited satisfactory analytical performance for OTA with a linear range of 0.0001-0.1ng/mL and a low detection limit of 0.05pg/mL. Itpresents recommendable specificity, stability, and practical applications. Importantly, the PEC biosensor provides a new concept for construction of PEC biosensing platform.

Smartphone-based portable photoelectrochemical biosensing system for point-of-care detection of urine creatinine and albumin.

Creatinine and albumin are crucial biomarkers for health monitoring and their ratio in urine is an effective approach for albuminuria assessment. Herein, to address the challenges of point-of-care and efficient analysis of the biomarkers simultaneously, we developed a fully integrated handheld smartphone-based photoelectrochemical biosensing system. A miniaturized printed circuit board included a potentiostat for photocurrent measurements and single-wavelength light-emitting diodes (LEDs) for photo-excitation, which was controlled with a Bluetooth-enabled smartphone. Graphitic carbon nitride (g-C3N4)/chitosan nanocomposites were modified on a transparent indium tin oxide (ITO) electrode as photoactive materials. Creatinine was detected through chelate formation with copper ion probes, while albumin was recognized specifically by an antigen-antibody reaction based on immunoassay. The biosensing system demonstrated good linearity and high sensitivity, with detection ranges of 100 μg mL-1 to 1500 μg mL-1 for creatinine, and 9.9 μg mL-1 to 500 μg mL-1 for albumin. Spiked artificial urine samples with different concentrations were tested to confirm the practical validity of the biosensing system, where an acceptable recovery rate ranged from 98.7% to 105.3%. This portable photoelectrochemical biosensing platform provides a convenient and cost-effective method for biofluid analysis, which has an extensive prospect in point-of-care testing (POCT) for mobile health.

Fabrication of a high-performance photoelectrochemical aptamer sensor based on Er-MOF nanoballs functionalized with ionic liquid and gold nanoparticles for aflatoxin B1 detection

One of the most dangerous mycotoxins is Aflatoxin B1 (AFB1) that is commonly found in food. Thus, AFB1 has been considered as a serious food safety concern. Herein, using Er-MOF nanoballs assembled with gold nanoparticles (AuNPs) as photoactive elements, a photoelectrochemical aptasensor with high analytical performance was developed for sensing AFB1. Er-MOFs nanoballs were prepared by using ionic liquid as a ligand and Er3+ as a metal center through a solvothermal method. Chloroauric acid was reduced in-situ onto Er-MOF nanoballs to form Er-MOF@AuNPs nanocomposites. AuNPs can effectively enhance the photocurrent of Er-MOF nanoballs attributed to their excellent conductivity and local surface plasma resonance effect. In addition, they can provide active sites for immobilizing more biorecognition elements that can further enhance the sensing performance. Through self-assembling reaction, thiol-functionalized hairpin DNA (hDNA) was immobilized onto an Er-MOF@AuNPs-based interface to construct a photoelectrochemical biosensing platform. As the AFB1 aptamers labeled with gold nanoparticles (AuNPs-Apt) were selectively recognized, the photocurrent response can be further amplified. Due to the high affinity of AFB1 and its aptamer (Apt), when Apt is reacted with AFB1, it causes AuNPs-Apt detaching from the PEC aptasensing interface, and thus a reduced photocurrent response is generated. Under optimized conditions, the changes of photocurrent before and after recognition of AFB1 exhibits a linear response from 0.005 to 10.0 ng mL−1. In addition, the limit of detection obtained was 19.6 fg mL−1. This PEC aptasensor provides relatively high selectivity, reproducibility and accuracy in the determination of AFB1 in real corn samples.

Novel Photoelectrochemical Biosensing Platform Based on a Double Type II CdLa2S4/SnIn4S8/Sb2S3 Ternary Heterojunction as Photoactive Materials and NiCo2O4 Nanospheres as a Photoquencher for CA19-9 Detection.

A novel signal-off biosensing platform based on the CdLa2S4/SnIn4S8/Sb2S3 heterojunction as photoactive materials and NiCo2O4 nanospheres as a photoquencher was developed to achieve the sensitive detection of CA19-9. First, the narrow band gap hydrangea-like CdLa2S4/SnIn4S8/Sb2S3 not only provided excellent photocurrent response but also supplied a mass of active sites that facilitated the loading of capture antibody (Ab1). Second, a double type II CdLa2S4/SnIn4S8/Sb2S3 heterojunction promoted the fast separation and migration of photogenerated e-/h+ and overcame the problem of short carrier lifetime caused by the recombination of photogenerated carriers. In addition, to improve the sensitivity of the constructed sensor to detect CA19-9, signal tags (p-type NiCo2O4) with large steric hindrance were introduced to accomplish signal amplification by the effect of double signal quenching. On one hand, NiCo2O4, which was strongly responsive to visible light, utilized its own advantages to compete for AA with CdLa2S4/SnIn4S8/Sb2S3, resulting in a decrease in the hole scavenging rate of the substrate. On the other hand, the photoquencher NiCo2O4 also prevented AA from contacting the matrix and further aggravated the photoelectrochemical (PEC) signal-damping effect. The PEC immunosensor was prepared with brilliant selectivity and splendid stability to detect CA19-9 (0.001-50 U/mL), and the detection limit was 0.0004 U/mL (S/N = 3).

Tunable Competitive Absorption-Induced Signal-On Photoelectrochemical Immunoassay for Cardiac Troponin I Based on Z-Scheme Metal-Organic Framework Heterojunctions.

Recently emerged Z-scheme heterostructure-based immunoassays have presented new opportunities for photoelectrochemical (PEC) biosensing development. Here, we described a tunable signal-on PEC biosensor for the detection of cardiac troponin I (cTnI), which exploited a competitive absorption effect between Cu(II) ions and a Zr metal-organic framework (Zr-MOF) constructed on TiO2 nanorods (Cu2+@Zr-MOF@TiO2 NRs). Water-stable Zr-MOF was coated onto TiO2 NRs on fluorine-doped tin oxide to form a Z-scheme heterostructure substrate (Zr-MOF@TiO2 NRs), which exhibited a high photoelectric response. Cu2+@Zr-MOF@TiO2 NRs, constructed by loading Cu(II) ions onto the architecture of Zr-MOF by electrostatic interaction, demonstrated a low background signal. After sandwich immunorecognition within a 96-well plate, H2S, generated by confined alkaline phosphatase on zeolitic imidazolate framework-8, was directed to react with Cu(II) ions to form CuS. This resulted in an in situ change in the photoelectrode and an enhanced photoelectric signal. The developed PEC biosensing platform exhibited high sensitivity and selectivity for the cTnI immunoassay with a detection limit of 8.6 pg/mL. The Z-scheme-based competition absorption modulation of photoelectrochemistry provides a new strategy for general PEC biosensing development.

Photoelectrochemical biosensing platform based on in situ generated ultrathin covalent organic framework film and AgInS2 QDs for dual target detection of HIV and CEA

In this work, a new photoelectrochemical (PEC) biosensing platform based on an ordered two-dimensional (2D) ultrathin covalent organic framework (COF) film and AgInS2 quantum dots (QDs) has been developed to enable dual-target detection of HIV and CEA. The porous COF film was firstly in situ generated on ITO, displaying super-stable and intense photocurrent with excellent repeatability. Moreover, an effective PEC quenching probe was specifically designed by loading large number of AgInS2 QDs on Au nanoparticles (NPs). After target HIV-induced cyclic amplification process to generate abundant DNA S0, the Au NPs-AgInS2 QDs probe was binded to the COF film through DNA hybridization, enabling PEC signal of the COF film to turn “off” for ultra-sensitive detection of HIV. Furthermore, when CEA as the second target specifically binded to its aptamer, the Au NPs-AgInS2 QDs quenching probe was released, achieving PEC signal “on” of the T-DA COF film for ultra-sensitive detection of CEA. This work opened a unique 2-D COF film-based PEC biosensing platform with excellent signal for rapid detection of dual targets, which can effectively avoid false positives and negatives and shows promising application for early prevention and detection of cancer diseases.

Identification and ultrasensitive photoelectrochemical detection of LncNR_040117: a biomarker of recurrent miscarriage and antiphospholipid antibody syndrome in platelet-derived microparticles

The abnormal expression of long non-coding RNAs (LncRNAs) in platelet-derived microparticles (PMPs) is closely related to immune disorders and may lead to antiphospholipid antibody syndrome and recurrent miscarriage. To understand the association between the LncRNAs in PMPs and RM/APS, the differences in the expression of LncRNAs in RM/APS patients and healthy controls were analyzed. Microarray analysis and RT-qPCR detection proved that RM/APS patient exhibited high levels of LncNR_040117 expression. The lentiviral silent expression transfection of HTR-8/SVneo cells indicated that LncNR_040117 downregulation decreased the activity of HTR-8/SVneo cells and inhibited the MAPK signaling pathway, further confirming the biomarker proficiency of LncNR_040117 for RM/APS. After that, we proposed a β-In2S3@g-C3N4 nanoheterojunction-based photoelectrochemical (PEC) biosensor to achieve the ultrasensitive detection of LncNR_040117. The nanoheterojunction aids in the effective separation of photogenerated carriers and significantly improve the photocurrent response of the biosensor. The conjugation of LncNR_040117 onto the PEC biosensing platform increased the steric hindrance between electrolyte and electrode, subsequently decreasing the photocurrent signal. The PEC biosensor showed a wide detection range of 0.1–106 fM and a low limit of detection of 0.025 fM. For clinical sample testing, the results of the PEC and RT-qPCR were highly consistent. Overall, LncNR_040117 in PMPs was identified as an effective biomarker for RM/APS and could be accurately detected by the proposed PEC biosensor, which is expected to provide a reliable diagnostic platform for RM/APS.

Metal-organic framework-enabled surface state passivation integrating with single-nuclease-propelled multistage amplification for ultrasensitive lab-on-paper photoelectrochemical biosensing

The surface states and photoinduced corrosion in the photoelectrode can severely reduce the photocurrent signal and stability of photoelectrochemical (PEC) sensor, which imposes a great challenge on the improvement of analytical performance. Herein, metal–organic framework (MOF)-enabled surface passivation strategy is proposed to passivate surface states, suppress photocorrosion and facilitate interfacial charge transport. In the concrete, zeolitic imidazolate framework-8 (ZIF-8), which serves as the passivation layer, is in-situ assembled on the surface of paper-based ZnO nanorods (NRs) array to restrain the charge trapping at the surface states and keep ZnO NRs from photocorrosion, thereby substantially enhancing the photocurrent signal and durability. Moreover, the unique single-nuclease-propelled multistage amplification (SNMA) and triple-helix molecular switch (THMS)-conformation-transition-mediated signal quenching strategies are also designed to further improve the sensitivity. The SNMA process can convert target microRNA-141 into quadruple amount of useful output DNA strands (trigger DNA) in one duplex-specific nuclease (DSN) cleavage cycle assisted by succedent DSN cleavage of DNA duplexes, guaranteeing a higher target amplification efficiency. Subsequently, the THMS structure which anchors double amount of signal enhancers to the photoelectrode surface can be disassembled by the resulted trigger DNA, therefore achieving powerful signal amplification. Profiting from the MOF-enabled surface state passivation and elegantly designed signal amplification strategies, the ultrasensitive detection of microRNA-141 is realized with a liner range from 0.2 fM to 2 nM and detection limit of 72 aM, which provides a promising paradigm for developing high-performance lab-on-paper PEC biosensing platform.

CRISPR/Cas12a-based photoelectrochemical sensing of microRNA on reduced graphene oxide-anchored Bi2WO6 coupling with catalytic hairpin assembly

An innovative and generic CRISPR/Cas12a-driven photoelectrochemical (PEC) biosensing platform was developed for screening of microRNA-21 (miR-21) by coupling with target-triggered catalytic hairpin assembly (CHA) and reduced graphene oxide-anchored Bi2WO6 (rGO-BWO) as the photoactive material. CHA isothermal amplification involved two programmable hairpin DNA modules and miR-21 as an activator. In the presence of miR-21, the products of target-triggered CHA circuit were inserted into the Cas12a-crRNA duplex to initial trans-cleavage capacity of CRISPR/Cas12a nuclease, accompanying the digestion on alkaline phosphatase (ALP)-labeled single-stranded DNA (ssDNA)-encoded magnetic bead (MB) through the activated CRISPR system. The ALPs were detached from magnetic beads and promoted the generation of ascorbic acid (AA), which increased the photocurrent of rGO-BWO-modified electrode. The value of photocurrent was positively proportional to the level of AA, which was also linearly correlated with target concentrations. Under optimum conditions, the CRISPR-based PEC sensing system displayed satisfying photocurrent responses toward miR-21 within the range from 1.0 fM to 1.0 nM with a limit of detection of 0.47 fM. In addition, the biosensor exhibited acceptable stability and excellent selectivity. Impressively, CHA-mediated CRISPR-based PEC biosensing platform provides a universal and sensitive method for clinical cancer diagnostics and biomolecular research.

Engineering of multifunctional carbon nanodots-decorated plasmonic Au@Ag nanoenzymes for photoelectrochemical biosensing of microRNA-155

Herein, the multifunctional carbon nanodots (CDs)-decorated plasmonic Au@Ag nanoenzymes coupled with Ti2C/Ag2S composites were proposed for photoelectrochemical (PEC) biosensing of microRNA. Two-dimensional (2D) Ti2C MXenes-sensitized Ag2S quantum dots (QDs) (Ti2C/Ag2S composites) acquired an initial photocurrent. After immobilization of a hairpin subsidiary probe (S1) onto the Ti2C/Ag2S composites photoelectrode surface, the target microRNA-associated bipedal DNA walker performed the opening of S1 for forming triple helix molecules. Then the CDs-decorated Au@Ag core–shell (Au@Ag@CDs) nanocuboids were introduced into the PEC biosensing platform through target-induced triple helix molecules. The Au@Ag@CDs nanocuboids as a multifunctional signal amplifier not only competitively captured the irradiating light and electron donors to weaken the PEC signal, but also quenched the photocurrent response resulting from energy transfer between plasmonic bimetallic Au@Ag nanocuboids and Ag2S QDs. Additionally, the Au@Ag and CDs in Au@Ag@CDs nanocuboids displayed a synergistic catalytic effect, and could serve as peroxidase nanoenzymes to catalyze the production of precipitates onto the biosensor surface, resulting in a significantly decreased photocurrent. Based on the plasmonic Au@Ag@CDs nanoenzymes coupled with Ti2C/Ag2S composites, microRNA-155 was ultrasensitively detected with a wide linear range (1–10,000 fM) and a low limit of detection (0.83 fM). Moreover, the engineered plasmonic Au@Ag@CDs nanoenzymes offer an environmentally friendly and multifunctional signal amplifier for fabricating PEC biosensor and have potential applications in biomarkers detection and disease diagnostics.

Ultrasensitive photoelectrochemical biosensing platform based target-triggered biocatalytic precipitation reactions on a flower-like Bi2O2S super-structured photoanode.

Herein, we reported a novel photoelectrochemical immunoassay method based on a target-triggered on/off signal of the ultra-structured Bi2O2S (BOS) photoanode system for the sensitive testing of carcinoembryonic antigens (CEAs) in serum samples. Well-defined three-dimensional sheet-like self-assembled flower-like Bi2O2S superstructures were obtained using a time-controlled hydrothermal method. Such well-shaped multifaceted surfaces were considered to be good laser cavity mirror surfaces for multifaceted reflection and refraction of excitation light in the material. An elegant enzyme biocatalytic strategy was introduced into the constructed detection model to sensitively detect CEAs. The substrate 4-chloro-1-naphthol (4-CN) was oxidized to 4-chloro-hexadienone (4-CD) under the formation of target-triggered immune complexes against mAb1 and peroxidase-modified mAb2. Subsequently, 4-CD produced by the biocatalytic precipitation reaction was transferred to the photoanodes of Bi2O2S nanoflowers (BOS NFs) to burst their photoelectric signals, thus achieving the quantification of CEAs. Through optimization of the conditions of the immunization protocol, a good negative photocurrent response to the target CEA was found in the wide range of 0.02-50 ng mL-1 with a detection limit of 11.2 pg mL-1. Impressively, the reported biocatalytic PEC sensing strategy on superstructures is comparable, or superior, to the gold standard ELISA kit in terms of sensitivity and the target response range. This study presents a target-mediated PEC immunoassay for biocatalytic precipitation based on a self-assembled superstructure of Bi2O2S, providing a fresh scheme for the analysis of disease-related markers.