Photoactive Matrix Research Articles

Ultrasensitive Paper-Based Photoelectrochemical Biosensor for Acetamiprid Detection Enabled by Spin-State Manipulation and Polarity-Switching.

Efficient carrier separation is vitally crucial to improving the detection sensitivity of photoelectrochemical (PEC) biosensors. Here, we developed a facile strategy to efficiently regulate the carrier separation efficiency of the photoactive matrix BiOI and In2S3 signal label functionalized paper chip by manipulation of electrons spin-state and rational design of electron transport pathways. The spin-dependent electronic structures of BiOI and In2S3 were regulated via enhanced electron-spin parallel alignment induced by an external magnetic field, markedly retarding carrier recombination and extending their lifetime. Simultaneously, with the progress of the target-induced catalytic hairpin assembly process, the transfer path of photogenerated carriers was changed, leading to a switch in photocurrent polarity from cathode to anode. This reversed electron transport pathway not only boosted the separation ability of photogenerated electrons but also eliminated false-positive and false-negative signals, thereby further improving the detection sensitivity. As a proof of concept, the well-designed magnetic field-stimulated paper-based PEC biosensor showed highly selectivity and sensitivity for acetamiprid assay with a wide linear range of 1 fM to 20 nM and an ultralow detection limit of 0.73 fM. This work develops a universal strategy for improving the sensitivity of biosensors and exhibits enormous potential in the fields of bioanalysis and clinical diagnosis.

High performance photoelectrochemical immunosensing platform based on front-illuminated Mo:BiVO4 photoelectrodes for procalcitonin assay

The outstanding photoactive materials are the imperative for the construction of a front-illuminated photoelectrochemical (PEC) biosensor, which is crucial step for improving the detection sensitivity. Yet, the weak and unstable initial PEC signals of the photoelectrodes have limited evidently the detection performance. Herein, a front-illuminated “on-off” PEC immunosensor was constructed based on Mo:BiVO4 as photoactive matrix and Au/CeO2 as signal quencher for sensitive detection of procalcitonin (PCT). Systematic studies reveal that the Mo doped BiVO4 can increase the charge carrier density of BiVO4, leading to much higher initial signal under front illumination than back illumination. Moreover, Mo:BiVO4 was directly grown on conducting substrates, which effectively overcomes the loose combination of sensing substrate ensuring good electrical contact and continuity. Upon coupling with Au/CeO2 as signal quencher, the initial photocurrent signal can be significantly quenched. As a result, the proposed PEC immunosensor presents a wide linear range from 10 fg mL−1 to 50 ng mL−1 with a detection limit of 2.45 fg mL−1. Impressively, this study will open a new avenue for the construction of highly efficient and stable photoelectrode, as well as extend the application of PEC biosensor for biomarkers detection in early disease diagnosis.

Photoelectrochemical immunoassay of carcinoembryonic antigen based on hollow In2O3/In2S3 nanocolumn

AbstractThis work presents a split‐type photoelectrochemical (PEC) immunoassay platform for ultrasensitive determination carcinoembryonic antigen (CEA) using In2O3/In2S3 nanocolumn as the photoactive matrix. Initially, In2O3/In2S3 nanocolumn with high photocurrent response was obtained by vulcanizing metal‐organic framework‐derived hollow In2O3 nanomaterials for surface modification. Subsequently, sandwich immunoreactions were conducted utilizing an alkaline phosphatase‐labeled secondary antibody that served as a signal pointer. A large amount of ascorbic acid was produced by the biocatalytic reaction, which enhanced the anodic photocurrent of the In2O3/In2S3 nanocolumn‐modified electrode. Under optimized conditions, the In2O3/In2S3 nanocolumn‐based PEC immunoassay exhibited a promising photocurrent response to the target CEA in the operational scope of 0.02 ng/mL to 10 ng/mL, with a limit of detection of 8.4 pg/mL. Benefiting from the excellent photoelectrochemical response of In2O3/In2S3 nanocolumn to ascorbic acid and the separated detection operation, the constructed PEC immunosensing platform has the advantages of great precision and strong anti‐jamming capability, and the detection results are comparable to those of commercial ELISA kits. Collectively, this study not only offered an efficacious semiconducting surface modification strategy to enhance photocurrent response activity, but also offered a novel thought for the sensitive measurement of a marker of cancer.

Magnetic field enabled spin-state reconfiguration for highly sensitive paper-based photoelectrochemical bioanalysis

Efficient carrier separation plays an utterly pivotal role in enhancing the sensitivity of photoelectrochemical (PEC) analysis. Here we report a concise yet powerful strategy of electron spin polarization induced by magnetic stimulation, to effectively modulate the efficiency of charge separation in a paper-based PEC (μ-PEC) sensing system. The electronic configuration of the sulfur-defected CdIn2S4/FeOOH photoactive matrix and ferromagnetic ZnFe2O4 signal label were regulated via the electron parallel alignment along with spin state flip and reconstruction at particular active sites under external magnetic field, significantly facilitating the separation of photoinduced carriers. As a proof-of-concept application, the magnetic-triggerable spin-state reconfiguration coupled with enzymatic catalytic precipitation reaction was developed for detection of chlorpyrifos with a wide linear range of 10-2.5-106 ng mL−1 and low detection limit of 0.67 pg mL−1. This work provides the basis for understanding the role of magnetic stimulus in tailoring charge separation and constructing a universal strategy for high performance μ-PEC bioanalysis.

A “signal-off” type photoelectrochemical immunosensor for detecting carcinoembryonic antigen based on TiO2 NRs/BiOI heterojunction and SiO2/PDA-Au inhibitor

A novel “signal-off” photoelectrochemical (PEC) immunosensor for sensitive and specific detection of carcinoembryonic antigen (CEA) is proposed. This proposed PEC sensor uses titanium dioxide nanorods (TiO2 NRs)/bismuth iodide (BiOI) heterojunction (TiO2 NRs/BiOI) as the photoactive matrix in which SiO2/PDA-Au is used as the labeled secondary marker. The TiO2 NRs/BiOI heterojunction has excellent visible light absorption capacity and the photoelectric signal is about 3.5 times of pure TiO2 NRs, which also has efficient carrier separation and transfer capabilities. In addition, SiO2/PDA-Au bring a dual inhibitory effect due to SiO2/PDA with a big spatial block and Au nanoparticles with a high visible light absorption capacity, which significantly improves the sensitivity of the constructed sensor. This PEC immunosensor demonstrates great sensitivity, selectivity, and stability, which shows a detection range of 0.005–100 ng mL−1 and a detection limit as low as 0.00167 ng mL−1. The constructed PEC immunosensor also has good performance in the analysis of real human serum samples.

Highly sensitive photoelectrochemical sensing platform based on PM6:Y6 p-n heterojunction for detection of MCF-7 cells

Development of novel photoactive materials is of great significance for improving the analytical performance of photoelectrochemical (PEC) biosensors. Herein, sensitive PEC biosensor was developed based on organic PM6:Y6 p-n heterojunction as photoactive matrix for circulating tumor cells (CTCs) detection. Y6, as organic acceptor that combines with the organic donor PM6 forms p-n heterojunction promoted separation of photo-generated charges with high charge transfer efficiency, resulting in the enhancement of photocurrent intensity. The detection of CTCs was achieved through the traditional “sandwich” protocol. Magnetic nanobeads (MNs) decorated with anti-epithelial cell attachment molecule antibody (anti-EpCAM) were used for capturing and separating CTCs, while the Au-aptamer probe and silver staining reaction were designed for dual signal amplification. The localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs), and silver nanoparticles (Ag NPs) that generated by silver staining reaction improved photocurrent response of PEC sensor. This PEC biosensor was applied to detect MCF-7 and displayed an ultra-low detection limit of 9 cell mL−1 and linear range from 10 to 10000 cell mL−1. This work explored a path for the application of organic semiconductors as photoactive materials in PEC sensing, which may find broad applications for detecting varied analytes.

Highly sensitive photoelectrochemical neuron specific enolase analysis based on cerium and silver Co-Doped Sb2WO6

A signal-enhanced photoelectrochemical immunoassay technique for detecting neuron specific enolase (NSE) was proposed. As a photoactive matrix, (Ce,Ag):Sb2WO6 was firstly investigated via doping Ce and Ag into Sb2WO6. It could be found that the presence of Ce and Ag not only had enormous variation on the morphology of Sb2WO6, but also showed excellent PEC behavior. In order to further improve the visible light utilization rate of (Ce,Ag):Sb2WO6, In2S3 was modified onto the surface of (Ce,Ag):Sb2WO6 to enhance visible light absorption. In addition, the CdS/PDA was served as a secondary antibody marker to further amplify signal. Especially, PDA as an electron donor could effectively remove photogenerated holes. Meanwhile, the good matching cascade band-edge levels between CdS and Sb2WO6 could promote photoelectron migration, improve the PEC response, and achieve sensitive detection of NSE. Under the selected excellent conditions, the photocurrent can linearly increase with the increase of NSE concentration in the operating range from 0.1 pg/mL to 50 ng/mL, and the limit of detection is 1.57 fg/mL. The constructed immunosensor also exhibits satisfactory stability, selectivity, and reproducibility, and it creates conditions for the detection of other biomolecules.

A dual-signal amplification photoelectrochemical immunosensor for ultrasensitive detection of CYFRA 21-1 based on the synergistic effect of SnS2/SnS/Bi2S3 and ZnCdS@NPC-ZnO

In this study, we utilized SnS2/SnS/Bi2S3 as a photoactive matrix and ZnCdS@NPC-ZnO as a signal label to construct a sandwich-type PEC immune-sensing platform. Specifically, we first applied a one-step solvothermal method to directly synthesize SnS2/SnS and form a p-n heterojunction. We then grew Bi2S3in situ on the SnS2/SnS surface, which greatly enhanced the efficiency for capturing visible light and improved the PEC signal. In addition, we labeled ZnCdS nanoparticles with a secondary antibody (Ab2) to provide a dual-signal response. Finally, we introduced NPC-ZnO, which has good adsorption performance, to the adsorbing matrix for the ZnCdS nanoparticles, which significantly accelerated the photoinduced electron transfer and further improved the sensitivity of the PEC immunosensor. As a proof-of-principle, we used the sensor to detect CYFRA 21-1 in blood plasma, a diagnostic marker of non-small cell lung cancer. Under optimized experimental conditions, the designed PEC immunosensor displayed a good linear range for CYFRA 21-1 from 0.1 pg/mL to 100 ng/mL, with a low limit of detection (LOD) of 0.06 pg/mL (S/N = 3). In summary, our data suggests that the newly developed PEC immunosensor possesses excellent selectivity and stability and has promising potential to detect biomarkers for lung cancer and other diseases.

A duple nanozyme stimulating tandem catalysis assisted multiple signal inhibition strategy for photoelectrochemical bioanalysis

Abstract A sandwich-type photoelectrochemical (PEC) immunosensor was developed for cytokeratin 19 fragment 21−1 (CYFRA21−1) ultrasensitive detection relying on a multiple signal inhibition strategy. In this work, Bi10O6S9 nanosheet arrays (BiOS) sensitized strontium titanate nanocubes (SrTiO3 NCs) was used as photoactive matrix. Bi10O6S9 with the large specific surface area and narrow band gap could improve the utilization of light to provide strong initial PEC signal. Besides, bovine serum albumin stabilized gold nanoparticles (BSA@Au NPs) anchored on Cu7S4 polyhedron composite (BSA-Au@Cu7S4 polyhedron) was utilized as an effective PEC signal regulator. As a duple nanozyme with the glucose oxidase (GOx)-like activity and the peroxidase-like activity, BSA@Au NPs induced intriguing tandem biocatalytic precipitation (BCP). On the one hand, the BCP could produce precipitations which obstructed the electron transfer between the photoelectrode and electron donor, leading a decrease of PEC signal; On the other hand, the competitive light absorption between BSA-Au@Cu7S4 polyhedron and photoactive matrix caused a further reduction of PEC signal. Generally, the PEC signal was quenched sharply taking advantage of multiple signal inhibition strategy including tandem BCP strategy, competitive absorption of light and steric hindrance, which improved the detection sensitivity of PEC immunosensor. The suggested PEC immunosensor displayed a good linearity in the range of 0.1 pg/mL - 50 ng/mL for CYFRA21−1 detection with a low detection limit of 1.12 fg/mL (S/N = 3). The skillful strategy has infinite potential in biological samples analysis.

Ultrasensitive Photoelectrochemical Assay for DNA Detection Based on a Novel SnS2/Co3O4 Sensitized Structure.

In this work, an ultrasensitive photoelectrochemical (PEC) assay was established for sensitive DNA detection based on a novel SnS2/Co3O4 sensitized structure as a photoactive matrix and benzo-4-chlorohexadienone (4-CD) precipitate as a signal quencher. Noticeably, the photoelectric conversion efficiency of the SnS2/Co3O4 sensitized structure was dramatically enhanced due to the effective sensitization of Co3O4 toward SnS2, thus attaining an intense photocurrent response, which was sixfold higher than that of pristine SnS2. Additionally, with the assistance of Nt.BstNBI enzyme-assisted target cycling process, a limited amount of target DNA (a fragment of p53 gene) could be converted into extensive output DNA, which could hybridize with capture DNA to yield abundant DNA duplex for loading mimetic enzyme manganese porphyrin (MnPP). Subsequently, 4-chloro-1-naphthol (4-CN) could be catalyzed to form 4-CD precipitate by MnPP on the modified electrode surface with the existence of H2O2. Then, the 4-CD precipitate severely hampered electron transfer, causing a prominently diminished photocurrent response for DNA determination. The elaborated PEC assay not only extended the application of SnS2 in the PEC biosensing field but also manifested a wide linear range of 100 aM to 1 nM with a low detection limit of 30 aM, exhibiting enormous potential for the detection of various biomarkers or other targets in bioanalysis and disease diagnosis fields.

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.

Magnetic bead-based photoelectrochemical immunoassay for sensitive detection of carcinoembryonic antigen using hollow cadmium sulfide

Herein a versatile photoelectrochemical (PEC) immunoassay platform for sensitive and specific screening of tumor biomarkers (carcinoembryonic antigen; CEA) was innovatively designed using hollow cadmium sulfide (H–CdS) as photoactive matrix based on immunomagnetic separation. Experimental results reveal that the hollow-structure prepared by template hydrothermal-etching method endowed the CdS with better photocurrent intensity compared to the traditional CdS nanoparticles. Upon addition of target CEA, a sandwiched immunoreaction was carried out between anti-CEA capture antibody-conjugated immunomagnetic bead (IMB) and horseradish peroxidase (HRP)-labeled anti-CEA detection antibody, accompanying the immunocomplex formation of the IMB-antibody/CEA/HRP-labeled antibody (IMB-CEA-HRP). Followed by magnetic separation, the carried HRP on the sandwich structure triggers enzymatic bioetching of H–CdS, thus resulting in decreasing photocurrent intensity. The H–CdS-based PEC sensing system exhibited satisfying photocurrent responses toward target CEA within the working range from 0.02 ng mL−1 to 50 ng mL−1 at a low detection limit of 6.12 pg mL−1. Combined with magnetic immunoassay, this sensing platform has the advantages of high precision, great anti-interference ability, and acceptable accuracy. Overall, this research not only provides an efficient strategy for the activity of CdS with a well-defined hollow-nanostructures but also sheds light on the development of enzyme-triggered bioetching technology for traditional PEC immunoassay.

Zinc and Molybdenum Co-Doped BiVO4 Nanoarray for Photoelectrochemical Diethylstilbestrol Analysis Based on the Dual-Competitive System of Manganese Hexacyanoferrate Hydrate Nanocubes.

This study proposes a competitive photoelectrochemical (PEC) immunosensor for detecting diethylstilbestrol (DES). The PEC sensing platform uses a zinc and molybdenum codoped BiVO4 nanoarray ((Zn,Mo):BiVO4) as the photoactive matrix and manganese hexacyanoferrate hydrate loading silicon dioxide layer composite nanocubes (MHCF@SiO2 NCs) as the signal quencher. The (Zn,Mo):BiVO4 nanoarray demonstrated brilliant PEC behavior, by virtue of the local electric field formed by the codoped Zn and Mo. This doping accelerated the electron transfer and improved the photoelectric conversion efficiency in BiVO4 nanoarray under visible light. Furthermore, the nanoarray structure with its large surface area provided abundant binding sites for the immune response. As the MHCF@SiO2 NCs-anti-DES competitively bonded with either free DES or bovine serum albumin conjugated DES (BSA-DES), hydrogen peroxide (H2O2) as electron donor was competitively consumed and meanwhile steric resistance blocked electrons transfer. For the above reasons, the photocurrent signal was reduced. Thus, the standard sample free DES was accurately detected, and the fabricated PEC immunosensor displayed an outstanding photocurrent response from 0.1 pg/mL to 50 ng/mL with a detection limit of 0.05 pg/mL. Simultaneously, the acceptable stability, selectivity, and reproducibility of the designed dual-competitive sensing platform suggest its applicability to small molecule detection.

A "σ-Hole"-Containing Volatile Solid Additive Enabling 16.5% Efficiency Organic Solar Cells.

SummaryHere we introduce a σ-hole-containing volatile solid additive, 1, 4-diiodotetrafluorobenzene (A3), in PM6:Y6-based OSCs. Aside from the appropriate volatility of A3 additive, the synergetic halogen interactions between A3 and photoactive matrix contribute to more condensed and ordered molecular arrangement in the favorable interpenetrating donor/acceptor domains. As a result, greatly accelerated charge transport process with suppressed charge recombination possibility is observed and ultimately a champion PCE value of 16.5% is achieved. Notably, the A3 treated OSCs can maintain a high efficiency of over 16.0% in a wide concentration range of A3 additive between 10 and 35 mg/mL. The A3-treated device shows excellent stability with an efficiency of 15.9% after 360-h storage. This work demonstrates that the σ-hole interaction can be applied to enhance the OSC performance and highlights the importance of non-covalent interactions in the optoelectronic materials.

Enzyme‐Encapsulated DNA Hydrogel for Highly Efficient Electrochemical Sensing Glucose

AbstractAn innovative bioetching photoelectrochemical (PEC) mode was developed by using enzyme‐encapsulated DNA hydrogel for high‐precision quantification of glucose, using In2O3−CdS nanocomposite as a photoactive matrix. In a proof‐of‐concept study, horseradish peroxidase and glucose oxidase were encapsulated in situ in DNA hydrogel to initiate enzymatic bioetching of CdS nanoparticles in the presence of target glucose. The bioetching reaction of CdS inhibits the electron transfer efficiency of In2O3 and CdS, which causes a change in photocurrent intensity and thus provides a powerful bioetching PEC strategy with enzyme‐encapsulated DNA hydrogel.

A photoelectrochemical sensor based on a reliable basic photoactive matrix possessing good analytical performance for miRNA-21 detection.

The basic photoactive matrixes on transparent electrodes are essential for the performance of photoelectrochemical (PEC) biosensors. Herein, we demonstrate an optimized fabrication strategy toward a reliable ITO/TiO2/AuNP photoanode by sequential deposition of TiO2/Au nanoparticles (Au NPs) on indium tin oxide (ITO) substrates. The identified fabrication conditions include spin-coating tetraisopropyl titanate on ITO slices followed by in situ electrodeposition of Au NPs and finally the thermal annealing treatment. By the conjugation of the thiolated hairpin NH2-DNA sequence and CdTe quantum dots (QDs) onto the thus-prepared photoanodes, a novel PEC sensor for the ultrasensitive detection of miRNA was constructed. The proposed PEC sensor offered advantages including simple structure, storage stability and excellent detection reproducibility as well as sensitivity and specificity toward miRNA-21. Finally, we found that this PEC displayed a broad detection linear range of 1.0 fM to 1.0 nM with a low detection limit of 0.37 fM. This PEC sensor can also excellently discriminate the mismatched miRNA. Moreover, the PEC sensor also showed a satisfactory result in normal human serum sample analysis. These findings emphasized the importance of basic photoactive matrixes for the fabrication of PEC sensors, providing solid fundamental insights for future application of metal oxide substrates for other PEC applications, especially PEC biosensors.

CdS:Mn-sensitized 2D/2D heterostructured g-C3N4-MoS2 with excellent photoelectrochemical performance for ultrasensitive immunosensing platform

The exploration of advanced photoactive materials with fine photoelectrochemical (PEC) performance is always the hot subject in PEC bioanalysis. Herein, Mn-doped CdS nanocrystals (CdS:Mn)-sensitized 2D/2D heterostructured g-C3N4-MoS2 was prepared and served as photoactive matrix of PEC sensing platform for myoglobin (Myo) detection using CuO nanoparticles labeled anti-Myo (anti-Myo-CuO) conjugates as signal amplification tags. The heterostructured g-C3N4-MoS2 could effectively promote the electron transfer and evidently restrain the recombination of electron-hole pairs, producing the high photocurrent response. Upon loaded CdS:Mn on the heterostructured g-C3N4-MoS2 to form co-sensitized structure, the photocurrent further gives a dramatically increase. To proof the performance of the co-sensitized structure in PEC bioanalysis, a sandwich type PEC immunosensor was designed by using the co-sensitized structure as photomatrix, Myo as model protein, and anti-Myo-CuO conjugates as amplifying tags. The introduction of anti-Myo-CuO conjugates in this system could significantly quench the PEC response of the sensing interface owing to the competition of the light-generated electron, poor conductivity and steric hindrance of the anti-Myo-CuO conjugates. In virtue of synergistic amplification of the CdS:Mn sensitized heterostructured g-C3N4-MoS2 and the anti-Myo-CuO conjugates, the immunosensor could respond down to 0.42 pg mL−1 Myo with a detectable range of 1.0 pg mL−1 to 50 ng mL−1. Moreover, this PEC platform demonstrates high specificity and sensitivity for Myo detection in real biological matrices. This strategy may furnish new insights for applications of novel 2D/2D heterostructures in PEC bioanalysis.

Sandwich-type signal-off photoelectrochemical immunosensor based on dual suppression effect of PbS quantum dots/Co3O4 polyhedron as signal amplification for procalcitonin detection

A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO2 nanoparticles (Au NPs/BiOI NSs/B-TiO2 NPs) as photoactive matrix and PbS quantum dots/Co3O4 polyhedron (PbS/Co3O4) as a quenching signal label for signal amplification. Concretely, BiOI NSs was fabricated by successive ionic layer absorption and reaction (SILAR) and formed the interlaced flake-like structure. Then Au NPs dropped on the BiOI NSs/B-TiO2 NPs electrode forming Au NPs/BiOI NSs/B-TiO2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co3O4, an effective dual suppression signal quencher, was proposed for signal-off PEC immunosensor to weaken the photocurrent response because of the steric impedance, competitive absorption of light and competing consumption of electron donor. In this proposal, PCT was chosen to measure the performance of the suggested PEC immunosensor. Consequently, the fabricated PEC immunosensor showed a widely detection ranged from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.02 pg/mL (S/N = 3). What is more, the proposed PEC immunosensor possessed satisfactory selectivity, stability and reproducibility.

Palindromic Fragment-Mediated Single-Chain Amplification: An Innovative Mode for Photoelectrochemical Bioassay.

This work reports a strategy for glutathione-loaded liposome-encoded magnetic beads initiated by palindromic fragment-mediated single-chain amplification (PFMSCA) for high-precision quantification of a low-abundance aminoglycoside antibiotic (kanamycin; Kana) by using In2O3-ZnIn2S4 (IO-ZIS) as a photoactive matrix. In this strategy, a Kana-recognition region, primer-like palindromic fragment, and polymerization/nicking template are reasonably integrated into one oligonucleotide (hairpin HP1) for target recognition, magnetic separation, and target amplification. Upon target Kana introduction, the Kana-aptamer region in HP1 specifically recognizes the Kana and triggers the palindromic tails intramolecular self-hybridization, amplifying a large number of short fragments in the presence of Klenow fragment polymerase and Nt.BbvCI. The as-generated nick fragments act as a linker to introduce the free hairpin HP2-functionalized glutathione-loaded liposomes (HP2-GLL) onto the surface of the hairpin HP3-modified magnetic beads (HP3-MB), constructing liposome-encoded magnetic beads (HP3-MB-nick-HP2-GLL). Following magnetic separation, the detached glutathione-loaded liposomes (GLL) are lysed by treatment with 1% Triton X-100 to release the glutathione within it, which were then detected as an amplified photocurrent at the IO-ZIS-based photoelectrode. Importantly, this method can be readily carried out by using one oligonucleotide to achieve an exponential amplification effect and open new opportunities for advanced development of robust biodetection systems.

Photoelectrochemical bioanalysis of antibiotics on rGO-Bi2WO6-Au based on branched hybridization chain reaction

Herein a versatile photoelectrochemical (PEC) bioanalysis platform for sensitive and specific screening of low-abundance antibiotics (kanamycin, Kana, used in this case) was innovatively designed using rGO-Bi2WO6-Au as photoactive matrix and target-induced branched hybridization chain reaction (t-bHCR) for efficient signal amplification. To realize the high-performance of our PEC bioanalysis system, rational introduction of reduced graphene oxide (rGO) and Au nanoparticles (Au NPs) greatly accelerated the electron transfer and enhances photoactivity. As expected, the ternary nanocomposite (i.e., rGO-Bi2WO6-Au) system with cascade energy level exhibited intense PEC signal responses thanks to multistep electron-transfer (MET) mechanism. Upon sensing the target Kana, t-bHCR is readily implemented, thus resulting in the assembly of numerous CuS nanoparticle (CuS NP). As a result, the loading CuS NPs from hyper-branched structure boosted the electron donors (ascorbic acid) consumption and enhanced the steric hindrance, synergistically decrease the photoelectric response. Under the optimized testing conditions, the t-bHCR-based PEC bioanalysis exhibited superior analytical performance with a linear range of 1 pM to 5 nM target Kana and limit of detection down to 0.78 pM. Additionally, favorable stability, great anti-interference ability and satisfactory accuracy for the analysis of actual samples were acquired. Impressively, the concept of t-bHCR-mediated provides an alternative to construct PEC bioanalysis and inspire more interest in the design of advanced PEC bioanalysis through nucleic acid-related signal amplification.