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3D dynamic DNA walker traveling on DNA micelles coupled CRISPR-Cas12a nucleases sensor was proposed to recover electrochemiluminescence (ECL) signal for microcystin-LR (MC-LR) detection. The 3D DNA walker was anchored in DNA micelles, self-assembled from amphiphilic DNA by the hydrophobicity of cholesterol and the electrostatic repulsion of the phosphate backbone. By the MC-LR stimulus, the released swing arm DNA hybridized with the track DNA while cleaving the hairpin structure to obtain the track DNA fragments. The track DNA fragments hybridized with the H1 hairpin structure to form a double-helix structure with PAM sequences, which could activate the Cas12a nucleases for trans-cleavage of the Fc probe-labeled ssDNA to induce ECL signal recovery. The DNA micelles maintained the morphological stability and free diffusion ability of the 3D DNA walker in the biofluidic state and overcome the collisional hindrance for facilitating efficient intraparticle and interparticle walking motions. Meanwhile, the coupled trans-cleavage activity of Cas12a nucleases improved the signal-amplification performance and achieved higher sensitivity with a detection limit of 0.015 pM. Acceptable results confirmed the ability of DNA micelles to stabilize 3D DNA walkers and the validated cleavage activity of Cas12a nucleases. • 3D DNA walker anchored in DNA micelles for maintaining free diffusion ability. • The released swing arm DNA hybridized with the track DNA By microcystin-LR stimulus. • Swing arm DNA could bind the next track DNA for intra- and inter-particle walking. • The track DNA fragments hybridized with H1 to activate the Cas12a nucleases. • The sensor achieved signal-amplification and higher sensitivity with LOD of 0.015 pM. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL)-functionalized metal-organic frameworks (MOFs) have become one of the most favored topics in biomarker immunoassays. Herein, a biocompatible tris(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium(II) [Ru(dcbpy) 3 2+] functionalized γ-cyclodextrin MOF was freshly prepared as an ECL tag for analyzing cytokeratin 19 fragment 21–1 (CYFRA21–1), a quintessential biomarker of non-small cell lung cancer. As a green ECL carrier, γ-CD-MOF possessed a large cavity that can absorb enormous Ru(dcbpy) 3 2+ molecules, obtaining consecutive stable ECL signals using N,N -dibutyl-2-hydroxyethylamine (DBAE) as a coreactant. Further functionalization of palladium nanoparticles with Ru@ γ-CD-MOF not only facilitated the electron-transfer rate to boost the ECL emission but also immobilized the detection antibody (Ab 2) via a Pd-N bond. To fabricate the sensing substrate, a porous NH 2 -MIL-125 (Ti) MOF was coated on the electrode to provide many binding sites for the capture antibody (Ab 1). Through the traditional sandwich-type sensing format, the assembled immunosensor manifested a linear range with a limit of detection of 0.048 pg/mL (S/N = 3) within a concentration gradient of 0.0001–50 ng/mL for CYFRA21–1 detection. Given this strategy's merits of favorable specificity, reliable accuracy and remarkable stability, this study highlighted the feasibility of fabricating γ-CD-based ECL tags for immunosensor construction, revealing this strategy's promising aptitude for bioanalysis and the clinical diagnosis of biomarkers. • Ru(dcbpy) 3 2+ functionalized γ-cyclodextrin MOFs were prepared as biocompatible electrochemiluminescence tags for immunoassay. • The γ-cyclodextrin MOFs efficiently stabilized enormous Ru(dcbpy) 3 2+molecules to enhance the ECL emission. • An electro-active sensing substrate was fabricated based on porous NH 2 -MIL-125 (Ti) MOFs. • The developed immunoassay for cytokeratin 19 fragment 21–1 detection reach to an ultra-trace level. [ABSTRACT FROM AUTHOR]

Encouraged by the remarkable editability, sequence-specificity, trans-cleavage peculiarity of the CRISPR-Cas12a, the concept of CRISPR-Cas12a accessory cleavage activity triggering electrochemiluminescence (ECL) biosensor for adenosine triphosphate (ATP) detection was proposed. The ATP aptamer was elaborately designed to stimulate the CRISPR-Cas12a activity for non-specifical trans-cleavage of the single-stranded DNA (ssDNA) modified L -Cys@Fe 3 O 4 MNPs. Those sheared ssDNA fragments and the hatched capture DNA on the electrode surface folded into double-helix structures for embedding of tris (2, 2´-bipyridine) dichlororuthenium (Ⅱ) [Ru(bpy) 2 3+] molecules to trigger "turn-on" signal. Specific conjugation of ATP aptamer to ATP surpassed base complementary pairing with the CRISPR-Cas12a, which inhibited CRISPR-Cas12a accessory cleavage activity and interfered with stability of the Cas12a-crRNA-ATP aptamer complex causing the "on-off" signal transformation. Thanks to the efficient signal-amplification produced by the editable CRISPR-Cas12a, this biosensor was performed for the specific and precise detection of ATP with the detection limit of 1.9 nM. Acceptable results showcase this CRISPR-Cas12a assisted ECL sensing strategy will open up a new pathway for more related bioanalysis. • ATP aptamer stimulated CRISPR-Cas12a non-specifical trans-cleavage activity. • Specific conjugation of ATP aptamer to ATP surpassed with the CRISPR-Cas12a. • The sheared ssDNA fragment and capture DNA folded into double-helix strands. • The Ru(bpy) 2 3+ embedded to the double-helix structures to trigger "turn-on" signal. • ATP inhibited CRISPR-Cas12a cleavage activity causing "on-off" signal transformation. [ABSTRACT FROM AUTHOR]

Neuron-specific enolase (NSE), a marker of small cell lung cancer, is over-expressed in patient serum. To reduce the threat of lung cancer to human health and life, a rapid and effective method for the sensitive detection of NSE is necessary. In this study, a sandwich-type photoelectrochemical (PEC) immunosensor for the rapid and sensitive detection of NSE was constructed. To provide a powerful and stable photocurrent signal, the bandgap-matched CdS/NiCo 2 O 4 was used as the substrate material. In addition, Au@CoFe 2 O 4 , which can form a step electron transfer mode with NiCo 2 O 4 , was proposed for the first time as a second antibody (Ab 2) marker to amplify photoelectric signals. The constructed signal-amplified PEC immunosensor showed good linearity in the range of 1 pg/mL − 100 ng/mL with a detection limit as low as 0.24 pg/mL (S/N=3). The constructed PEC immunosensor has shown excellent stability, selectivity, reproducibility, and repeatability. It showed recoveries in the range of 98% − 105% and relative standard deviations (RSD) within 5% in sample analysis. The method proposed in this study is expected to be more widely used in the future for the detection of other disease markers as well as environmental pollutants. [Display omitted] • II-type heterojunction CdS/NiCo 2 O 4 as substrate material to provide stable photocurrent. • Au@CoFe 2 O 4 as the secondary antibody label for signal amplification. • Constructed sandwich-type immunosensor enables ultrasensitive detection of NSE. • PEC immunosensor exhibited a low detection limit of 0.24 pg/mL for NSE. [ABSTRACT FROM AUTHOR]

• A sandwich-type immunosensor for detection of PCT was designed. • CeO 2 -CuO-Au as platform can promote electron transfer. • Au@Ag-Th as signal labels can further effectually amplify the current signal. • The immunosensor presents prominent performance for PCT detection. Procalcitonin (PCT) is a kind of protein exists in the human blood. If the human bodies are infected with bacteria, fungi or parasites, the value of PCT in blood will be significantly raised. Thereby, we report an electrochemical immunosensor for measurement of PCT using gold nanoparticle (Au NP) decorated CeO 2 -CuO (CeO 2 -CuO-Au) as the platform and thionine modified Au@Ag heterojunction nanorods (Au@Ag-Th) as signal labels. Au NP decorated CeO 2 -CuO exhibits high surface area, high activity and good biocompatibility, which can immobilize more primary antibodies and promote electron transfer. The Au@Ag-Th provides good active sites to link secondary antibodies, further effectually amplify the current signal. This immunosensor exhibits a well-pleasing response with a limit detection of 0.17 pg mL−1 and linear detection between 0.5 pg mL−1 and 50 ng mL−1. Meanwhile, the high sensitivity, excellent specificity and acceptable human serum samples testing results of this method lead to potential applications in diagnosis of bacterial infections. [ABSTRACT FROM AUTHOR]

Developing electrochemical biosensor, particularly for high sensitive recognizing and detecting tumor marker at low level under benign conditions, is highly desired, but still remains a severe challenge. In this communication, we report a dual-signaling ratiometric method for sensitive detection of carcinoembryonic antigen (CEA) based on gold nanoparticles (Au NPs) functionalized Cu 2 S-CuS/graphene composite (Au-Cu 2 S-CuS/graphene) as the matrix material and carboxyl-Au nanoparticles (Au-COOH) functionalized mesoporous CeO 2 nanoparticles (Au-CeO 2 ) supported toluidine blue (TB) complex as signal label. The oxidation peak current of Cu 2 S-CuS decreases with the increase of CEA concentration, while the oxidation peak current of TB increases. The change of dual signals “Δ I = Δ I TB + |Δ I Cu2S-CuS |” (Δ I TB and |Δ I Cu2S-CuS | are the change values of the oxidation peak currents of TB and Cu 2 S-CuS, respectively) is used as the response signal for quantitative determination of CEA. Notably, the linear range is 0.001 ∼ 100 ng/mL with a detection limit of 0.78 pg/mL (S/N = 3). The ratiometric electrochemical system provides an extremely simple strategy for detecting tumor markers in a reliable, facile, sensitive, and specific manner, which has a promising application for quantitative detection of other tumor markers in clinical diagnosis. [ABSTRACT FROM AUTHOR]

One competitive aptasensor based on novel intramolecular ECL emission system was investigated for ultrasensitive detection of E 2. It should be noted that the Ru(II) derivative for the mechanism of intramolecular ECL could improve electron transfer efficiency and reduce energy consumption. The Ru(II) derivatives were prepared by optimizing distribution ratio of Ru(dcbpy) 3 2+ and carbohydrazide for acquiring the ECL signal maximum. Stimulated by In3+/In+ redox reversible electron pair in the InVO 4 /β-AgVO 3 heterostructures, the InVO 4 /β-AgVO 3 heterostructures were designed as co-reaction accelerator to expedite ECL emission reaction between CON 4 H 6 • and Ru(dcbpy) 3 3+. Taking advantage of associative competition between cDNA and E 2 with aptamer, the ECL signal realized further amplification. The specific binding of the aptamer to E 2 , was stronger than that to the cDNA by hybridization. A mass of Ru(II) derivatives could adsorb and embed into the hybridized double-stranded DNA to immobilize on the electrode surface and generate satisfactory ECL signal. The specific binding of the aptamer to E 2 decreased the cDNA content on electrode surface, which contributed to lessen the adsorption amount of Ru(dcbpy) 3 2+ and distinctly affected the ECL signal. Under optimal conditions, the proposed biosensor provided an admirable linearity to the level of E 2 between 0.001 nmol/L and 100 nmol/L with a low detection limit of 0.27 pmol/L. The proposed aptasensor not only stimulates more interest in the mechanism of intramolecular ECL but also has towardly development potential for constructing competitive strategies. • This mode involved the Ru(II) derivative for the mechanism of intramolecular ECL, which could be obtained through an amide reaction between Ru(dcbpy) 3 2+ and carbohydrazide. • Stimulated by In3+/In+ redox reversible electron pair in the InVO 4 /β-AgVO 3 heterostructures, the InVO 4 /β-AgVO 3 heterostructures were designed as co-reaction accelerator to expedite ECL emission reaction between CON 4 H 6 • and Ru(dcbpy) 3 3+. • The competition between cDNA and E 2 could determine the amount of adsorption of the Ru(II) derivative to further improve the sensitivity of the aptasensor. • The proposed biosensor provided an admirable linearity to the level of E 2 between 0.001 nmol/L and 100 nmol/L with a low detection limit of 0.27 pmol/L. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) is a widely applied technique for trace detection and analysis, but the stability of luminophores and external environmental factors strongly influence the analysis results. Herein, a low-potential ECL sensing platform based on enhanced nanomaterial catalysis for the traditional system luminol-H 2 O 2 is proposed for the detection of neuron specific enolase (NSE). In this strategy, Au nanoparticles modified with three-dimensional graphitic phase carbon nitride (3DCNA) were used as a solid platform for antibodies (Ab 2), which not only solved the problem of accumulation between traditional two-dimensional nanosheets but also had good biocompatibility, ensuring the accuracy of the analysis results. CoSn(OH) 6 , benefiting from its inherently higher catalytic activity and greater number of adsorption sites on perovskite hydroxide, can catalyze the oxidation reduction reaction of H 2 O 2 to improve the ECL behavior of luminol and lower the applied voltage to reduce damage to biological activity. Owing to these exceptional properties, this proposed sandwich ECL immunosensor was explored for the primary diagnosis of SCLC by detecting NSE with a detection limit of 0.18 pg mL–1. It exhibited satisfactory linearity in the range of 0.0005 ng mL–1 to 100 ng mL–1 with favorable stability, excellent specificity, and good reproducibility. This study provides an important reference for low-potential ECL with promising application prospects in actual clinical analysis and detection. • A low-potential electrochemiluminescence biosensor was constructed for NSE detection. • 3DCNA had good biocompatibility ensuring the accuracy of the analysis results. • CoSn(OH) 6 had higher catalytic activities to improve the ECL behavior of luminol. [ABSTRACT FROM AUTHOR]

The theory of aggregation-induced electrochemiluminescence (AIECL) provides a new method for preparing novel electrochemiluminescence emitters, but the lack of AIECL-based functional nanomaterials seriously hinder its development and application. In this work, Ti 3 C 2 T x MXene-stabilized iridium bis(1, 2-dipheny1–1 H-benzimidazole)(acetylacetonate) [Ir(pbi) 2 (acac)] with AIECL in polymer hydrogel was prepared for the first time. Due to the large electroactive surface area of Ti 3 C 2 T x MXene, the stabilized Ir(pbi) 2 (acac) (Ir@MXene) can amplify the ECL signal of the system. The confinement of Ir@MXene into the polyvinyl alcohol (Ir@MXene-PVA) hydrogel increased the local concentration of Ir(pbi) 2 (acac), which could not only prevent oxides from entering the Ir(pbi) 2 (acac) nanodots but also limit the vibration to reduce non-radiative transitions of Ir(pbi) 2 (acac), leading to a distinct AIECL emission. In addition, dopamine (DA) and H 2 O 2 have been used to explore the ECL quenching behavior of Ir@MXene-PVA systems. Based on ECL quenching of Ir@MXene-PVA system by DA, a sensor has been constructed to detect DA in human serum sensitively. The detection range was 0.01–100 nmol/mL, with a detection limit of 2.0 pmol/mL. This strategy provides an efficient method for the preparation of Ir@MXene-PVA hydrogel with AIECL emission, which may have promising potential in the clinical detection of DA, H 2 O 2, and other biomarkers. • Ir@MXene-PVA hydrogel composite as an AIECL emitter was used for detection DA. • Using Ti 3 C 2 Tx MXene to stabilize Ir(pbi) 2 (acac) can amplify the ECL of the system. • DA and H 2 O 2 can efficiently quench the ECL of the Ir@MXene-PVA/DBAE system. • The detection range of this sensor is 0.01–100 nmol/mL, with a LOD of 2.0 pmol/mL. [ABSTRACT FROM AUTHOR]

• Normal prostate cells and those of differing cancer progression vary in biophysical properties, wound healing time, and chemotaxis response. • The iMEP assay rapidly obtains single cell biophysical characteristics to distinguish between different prostate cell lines with p-value < 0.05. • Individual migration assays are not sufficient for assessing the tumorigenicity of a cell population or the metastatic potential of cancer cells. This study reveals a new microfluidic biosensor consisting of a multi-constriction microfluidic device with embedded electrodes for measuring the biophysical attributes of single cells. The biosensing platform called the iterative mechano-electrical properties (iMEP) analyzer captures electronic records of biomechanical and bioelectrical properties of cells. The iMEP assay is used in conjunction with standard migration assays, such as chemotaxis-based Boyden chamber and scratch wound healing assays, to evaluate the migratory behavior and biophysical properties of prostate cancer cells. The three cell lines evaluated in the study each represent a stage in the standard progression of prostate cancer, while the fourth cell line serves as a normal/healthy counterpart. Neither the scratch assay nor the chemotaxis assay could fully differentiate the four cell lines. Furthermore, there was not a direct correlation between wound healing rate or the migratory rate with the cells' metastatic potential. However, the iMEP assay, through its multiparametric dataset, could distinguish between all four cell line populations with p-value < 0.05. Further studies are needed to determine if iMEP signatures can be used for a wider range of human cells to assess the tumorigenicity of a cell population or the metastatic potential of cancer cells. [ABSTRACT FROM AUTHOR]

• ZIFs-derived Zn x Co 3-x O 4 dodecahedron was adopted to construct PEC aptasensor for the first time. • The hollow Zn x Co 3-x O 4 /N-GQDs/AgBiS 2 composite exhibited remarkable photoactivity using as matrix for PEC aptasensing. • The designed PEC aptasensor showed superior performances for ampicillin detecting. A sensitive photoelectrochemical (PEC) aptasensing platform based on Nitrogen-doped graphene quantum dots (N-GQDs) and AgBiS 2 dual-sensitized Zn/Co bimetallic oxide (Zn x Co 3-x O 4) dodecahedron as a matrix was constructed for the ultrasensitive detection of ampicillin (AMP). Concretely, the Zn x Co 3-x O 4 dodecahedron derived from ZnCo-ZIFs retained the unique hollow porous structure, which provided large specific surface and efficacious active sites, and thereby significantly enhancing the light utilization and shortening the photoelectrons transmission path. Both N-GQDs with the up-conversion effect and eco-friendly AgBiS 2 with optimal band gap for solar absorption were utilized to dual-sensitize Zn x Co 3-x O 4 dodecahedron to further strengthen the PEC performance. Subsequently, the aptamer recognition technology was integrated with the modified photoelectrode, adopting AMP-aptamer to catch the target AMP, accompanied the hole oxidation of bind AMP causing the remarkable increase of photocurrent signal, the AMP could be specific and sensitive detect. Under optimized conditions, the photocurrent of developed aptasensor increased linearly displayed large liner response of 0.5 pmol/L – 10 nmol/L with a detection limit of 0.25 pmol/L (S/N = 3). Besides, the novel PEC AMP-sensoring exhibited excellent reproducibility, perfect stability and selectivity, which could open a potential avenue for antibiotic residues detection in environmental media. [ABSTRACT FROM AUTHOR]

This work for the first time proposed a photoelectrochemical (PEC) sensor based on the in situ generation of BiOBr/Bi 2 S 3 by Cs 3 Bi 2 Br 9 to detect trenbolone (TB). To be specific, Cs 3 Bi 2 Br 9 /BiOBr/Bi 2 S 3 heterojunction, the chosen photoelectric material, that could produce stable and large photocurrent was obtained through two steps in situ growth method on the basic of Cs 3 Bi 2 Br 9 perovskite. CdS and Au nanoparticles with outstanding light absorption characteristics were selected as TB antigen (Ag) marker. Under the aid of Au/CdS, the association between TB concentration and output current will be revealed by the competitive combining of TB antibodies (Ab) with TB or Ag-Au/CdS. If the concentration of TB was lower, the more Ag-Au/CdS was connected to the Ab, and the higher photocurrent signal was obtained. Hence, the competitive PEC sensor could realize reliable detection of TB with a lower detection limit of 29.7 fg mL-1. • We for the first time constructed a PEC sensor to detect trenbolone. • Cs 3 Bi 2 Br 9 /BiOBr/Bi 2 S 3 was prepared by two steps in situ growth method. • Au/CdS was selected as a signal enhancer to improve the sensitivity of sensor. • The detection limit was 29.7 fg mL−1. [ABSTRACT FROM AUTHOR]

Herein, a split-type photoelectrochemical (PEC) immunosensor is designed to detect neuron-specific enolase (NSE), which is a tumor marker for small cell lung cancer present in nerve and neuroendocrine tissues. In this study, a heterogeneous In 2 O 3 /BiVO 4 structure is developed with coral-like BiVO 4 films adsorbed onto In 2 O 3 based on simplified successive ionic layer adsorption and reaction (s-SILAR). Moreover, immune recognition occurs in a 96-well plate in the split-type PEC immunosensor, thus effectively avoiding interference with the recognition of biomolecules. However, the sensitivity of zeolitic imidazolate framework (ZIF)− 8 molecules to pH varies, and most of the degradation of ZIF-8 molecules can be achieved by a reaction at a pH of 5.5–6.5 for > 30 min. Therefore, SiO 2 -glucose oxidase is selected as a regulatory switch to act on ZIF-8 molecules by catalyzing the conversion of glucose to gluconic acid, whereas In 2 O 3 /BiVO 4 is selected as the photoactive substrate and ZIF-8 protective layer as the signal switch. By constructing a split-type PEC immunosensor, gluconic acid of different concentrations is released in the 96-well plate through the change of NSE concentration to regulate the degradation of the ZIF-8 protective layer and achieve the sensitive detection of NSE. The constructed PEC sensor exhibits an excellent photocurrent response between 0.1 pg mL–1 and 100 ng mL–1, with a detection limit of 0.03 pg mL–1. Simultaneously, the accuracy, specificity, stability, and reproducibility of this split-type PEC sensing platform predict its promising application in the future in the field of biomolecules. • S-SILAR In 2 O 3 /BiVO 4 exhibited excellent PEC behavior. • The ZIF-8 layer is used as a medium for regulating photosensitive signals. • Tandem reforming of ZIF-8 layer with SiO 2 -GOx markers. • A split-type PEC sensor exhibited a low detection limit of 0.03 pg/mL for NSE. [ABSTRACT FROM AUTHOR]

A peptide-based antifouling photoelectrochemical (PEC) interface was developed for protein (small cell lung cancer marker as an example) sensitive detection. Hereinto, the monocrystal perovskite magnesium dititanate (MgTi 2 O 5) was successfully synthesized and applied as the basic material for PEC biosensor construction. This MgTi 2 O 5 processes a hollow nanorod morphology which enables enhanced photogenerated charges separation, and the hollow structure provides great specific surface area for visible light absorption. Polydopamine (PDA) with excellent biocompatibility and good electron transfer capability was also used as the bridge for inorganic functional materials and organic recognition proteins. Furthermore, the peptide sequence EKEKEKEPPPPC with antifouling performance was fixed on PDA and modified on photoanode to generate an antifouling interface, such a peptide-based antifouling PEC sensor not only blocks the nonspecific molecules and reducing agents, but also boosts the detection sensitive. And the proposed biosensor shows a wide detection range from 0.00001 to 1000 ng/mL, as well as a low detection limit of 4.3 fg/mL for neuron specific enolase (NES) analysis. This developed sensor widens the application of perovskite in analytical chemistry and offers a new prospect for practical applications of peptide-based antifouling interface. • The monocrystal perovskite MgTi 2 O 5 was successfully synthesized as photoactive material. • A peptide with the sequence EKEKEKEPPPPC was used to obtain the antifouling interface. • The biosensor exhibited the wide detection range from 0.00001 to 1000 ng/mL and the low detection limit of 4.3 fg/mL. [ABSTRACT FROM AUTHOR]

In this work, an efficient bioactivity-protective electrochemiluminescence (ECL) sensor was developed for biomarker analysis. First, 3,4,9,10-perylenetetracarboxylic acid (PTCA) with stable ECL emission served as luminophores, and its non-toxic properties were conducive to the survival of biomarkers. Second, CeO 2 /Co 4 N heterostructures were developed as coreaction accelerators to realize multiple amplification of luminescence signal. Concretely, large amounts of sulfate radicals (SO 4 •-) were generated through the reversible conversion of Ce3+/Ce4+ redox pairs. Meanwhile, the aggregation defect of CeO 2 nanoparticles (NPs) was alleviated with the introduction of Co 4 N nanowires, thereby improving catalytic efficiency. Furthermore, Co 4 N possessed good hydrogen evolution reaction (HER) characteristics, which promoted the ECL emission by enhancing the production of SO 4 •-. Third, the heptapeptide affinity ligand (HWRGWVC) was introduced to achieve the directional fixation of antibodies, thus protecting the bioactivity of the sensor and improving incubation efficiency of antibodies. In general, this study proposed a highly effective ECL enhancement mechanism, which provided the direction for the construction of highly bioactive and sensitive sensors. • Providing an efficient signal amplification strategy by designing CeO 2 /Co 4 N as co-reaction accelerators. • Proposing new insights for promoting ECL emission by hydrogen evolution reaction. • Developing the heptapeptide (HWRGWVC) as difunctional antibody orientation fixative. • Developing highly sensitive and active biosensor for biomarkers detection in serum sample. [ABSTRACT FROM AUTHOR]

• Preparing Bi 2 S 3 in situ grown on SnS 2 /SnS heterojunction for the first time • Developing a "dual-signal" amplification strategy based on the synergistic effect of SnS 2 /SnS/Bi 2 S 3 and ZnCdS@NPC-ZnO. • Realizing ultrasensitive detection of CYFRA 21-1 by the sandwich-type PEC immunosensor. In this study, we utilized SnS 2 /SnS/Bi 2 S 3 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 SnS 2 /SnS and form a p-n heterojunction. We then grew Bi 2 S 3 in situ on the SnS 2 /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 (Ab 2) 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. [ABSTRACT FROM AUTHOR]

• A sandwich-type PEC immunosensor was constructed for cytokeratin 19 fragment 21−1 ultrasensitive detection. • Bi 10 O 6 S 9 nanosheet arrays sensitized strontium titanate nanocubes (SrTiO 3 /BiOS) was used as photoactive matrix providing initial PEC signal. • BSA-Au@Cu 7 S 4 polyhedron was as a signal regulator through tandem BCP, competitive absorption of light and steric hindrance. 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, Bi 10 O 6 S 9 nanosheet arrays (BiOS) sensitized strontium titanate nanocubes (SrTiO 3 NCs) was used as photoactive matrix. Bi 10 O 6 S 9 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 Cu 7 S 4 polyhedron composite (BSA-Au@Cu 7 S 4 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@Cu 7 S 4 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. [ABSTRACT FROM AUTHOR]

• Silver nanoparticle decorated CuS@CoS 2 DSNBs were acting as dual-quencher firstly. • ECL-RET takes place from Au@C 3 N 4 (donor) towards CuS@CoS 2 DSNBs@Ag NPs (acceptor). • This ECL method acquired high sensitivity and selectivity for cerebrospinal fluid samples. A highly effective dual-quenching electrochemiluminescence (ECL) immunosensor premised on the electrochemiluminescence resonance energy transfer (ECL-RET) was constructed using silver nanoparticle decorated CuS@CoS 2 double shelled nanoboxes (CuS@CoS 2 DSNBs@Ag NPs) as the ECL acceptor and gold nanoparticles functionalized carbon nitride (Au@C 3 N 4) composites as the ECL donor. Generally, the UV–vis absorption spectra of CuS@CoS 2 DSNBs@Ag NPs were found effectively overlapped with the ECL spectra of Au@C 3 N 4 composites to trigger dual-quenching process. The fabricated Au@C 3 N 4 composites were also served as substrate to immobilize primary antibody (Ab 1) via Au-N bond besides providing excellent ECL signal sources. Moreover, CuS@CoS 2 DSNBs@Ag NPs can capture the secondary antibody (Ab 2) via the Ag-N bond to complete the sandwich immune interaction, where the ECL emission of Au@C 3 N 4 composites were flexibly regulated by CuS@CoS 2 DSNBs@Ag NPs via dual-quenching to indicate the concentration information of the detected antigens. This established immunosensor represented eminent performance for β-amyloid 1−42 oligomers (Aβ) detection in a wider detection range of 0.5 pg/mL-20 ng/mL with a much low detection limit of 0.0038 pg/mL (S/N = 3). With high sensitivity and good specificity features, the expected ECL strategy paved a latest pathway to perceive a persuable sensitive detection of Aβ. [ABSTRACT FROM AUTHOR]

• Ferrocene carboxylic acid inhibited ECL behavior of Ru(bpy) 3 2+. • Ru(bpy) 3 2+ and n-butyl diethanolamine co-doped in silica nanoparticles. • The quenching mechanism was Fca+ decrease Ru(bpy) 3 2+ * through electron-transfer. • The sandwich quenching ECL immunosensor was used to detect procalcitonin. Herein, a quenching electrochemiluminescence (ECL) immunosensor was applied to detect procalcitonin (PCT) based on ferrocene carboxylic acid (Fca) quenching the ECL of Ru(bpy) 3 2+. Co-reactant n-butyl diethanolamine and Ru(bpy) 3 2+ co-doped in silica nanoparticles which grafted on g-C 3 N 4 surface (RuSiNPs-g-C 3 N 4) as luminophores. g-C 3 N 4 could immobilize large amounts of RuSiNPs due to large specific surface area, besides, its electrical conductivity also contributed to enhance the ECL intensity. N-butyl diethanolamine serving as alternative co-reactant promoted ECL efficiency. Zeolitic Zn2+-imidazolate cross-linked frame-work (ZIF-8) were served as the supporter to immobilize more amounts of Fca, which could remarkably decrease the ECL signal. The quenching mechanism mainly because that the oxidation species of Fca could further react with the excited states of Ru(bpy) 3 2+*. Under optimal experiment conditions, the proposed immunosensor presented a linear response range for detecting PCT from 5 pg mL−1 to 100 ng mL−1 with a detection limit of 0.85 pg mL−1 (S/N = 3). Furthermore, the proposed ECL immunosensor presented favorable specificity, good stability as well as excellent reproducibility, this strategy can offer a guiding significance in fundamental and clinical analysis of PCT. [ABSTRACT FROM AUTHOR]

• Manganese-eumelanin coordination nanocomposites quenched ECL behavior of luminol. • Luminol was anchored on PtCo and CuFe 2 O 4 nanoparticles decorated with rGO. • Quenching mechanism maybe inhibit electrooxidation of H 2 O 2 and ECL energy transfer. • The sandwich quenching ECL immunosensor was used to detect procalcitonin. Herein, a facile one-pot intrapolymerization strategy to synthesize manganese-eumelanin coordination nanocomposites (Mn-Eu) was introduced to quench the electrochemiluminescence (ECL) behavior of luminol/H 2 O 2 system. Bimetallic PtCo and CuFe 2 O 4 nanoparticles decorated with reduced graphene oxide was prepared to combine with luminol via electrostatic attractions (Lu-PtCo-CuFe 2 O 4 -rGO) which possessed excellent ECL signals. PtCo-CuFe 2 O 4 -rGO not only exhibited well electrocatalytic activity toward the electrooxidation reactions of luminol and H 2 O 2 , but also facilitated the electroreduction of H 2 O 2 producing more reactive oxygen species (ROSs) which can further enhance the ECL intensity of luminol. To sensitively detect procalcitonin, Mn-Eu labeled-secondary antibodies were employed to specific recognize antigen which incubated with primary antibodies/Lu-PtCo-CuFe 2 O 4 -rGO. The quenching mechanism may be via the synergistic effect between Mn-Eu inhibiting the electrooxidation of H 2 O 2 and ECL resonance energy transfer (ECL-RET) from ECL donor luminol to ECL acceptor Mn-Eu. Under optimal experiments, the ECL immunosensor for detecting procalcitonin with a wider linear range from 0.005 pg/mL to 100 pg/mL and a detection limit of 0.0021 pg/mL (S/N = 3) was obtained. The suggested strategy possessed great potential in bioanalysis and will broaden the application of Mn-Eu. [ABSTRACT FROM AUTHOR]

• This report outlines a method to detect CYFRA21−1 by quenching electrochemiluminescence immunosensor. • Electron transfer and energy transfer occurs between TP−COOH NCs and Fe-HAP. • TP−COOH NCs was prepared with low impedance and good functionalization. • The cathode emission excited at -1.15 V to obtain better biocompatibility in K 2 S 2 O 8. • This electrochemiluminescence immunosensor obtains the detection limit of 0.01471 pg/mL. This report outlines a versatile novel quenching electrochemiluminescence immunosensor based on electrochemiluminescence (ECL) emission with aggregation induced emission (AIE) from TP−COOH NCs, which was utilized by poly-(styrene-co-maleicanhydride) to wrap on tetraphenylethylene nanocrystals. On the one hand, the cathode emission excited at -1.15 V could reduce emission produced by oxygen from high potential stimulation, on the other hand, such low potential can further protect the activity of immune molecules. Meanwhile, the coating can reduce interface impedance and completed functionalization. Herein, based on the synergistic effect of electron transfer and energy transfer between TP−COOH NCs and iron doped hydroxyapatite (Fe-HAP), the high efficiency of this ECL sensing platform can be achieved. The proposed ECL immunosensor for detection of trace Cytokeratin 19 fragment 21−1 (CYFRA21−1), exhibited a satisfied detection limit low to 0.01471 pg/mL (S/N = 3). As a result, this approach not only enriches the ECL strategies study to provide a feasible method for foundational clinical examination but also expands the potential application of ECL sensors in biological testing and clinical high-throughput diagnosis. [ABSTRACT FROM AUTHOR]

• The signal indicator and matrix, Fe 3 S 4 -Pd, displayed excellent electrocatalytic activity for H 2 O 2 redox reaction. • Magnetic glassy carbon electrode was used to firmly immobilized the magnetic Fe 3 S 4 -Pd to achieve satisfied stability. • PBG nanomaterial played a role as the electron blocking label that realized a sensitive variation of current signal. • The signal-off sensing platform was successfully constructed, with a low detection limit of 130 fg/mL. Herein, a sandwich-type electrochemical (EC) immunosensor is proposed based on a special signal-off mode for the sensitive detection of procalcitonin (PCT) by utilizing Fe 3 S 4 loaded with Pd nanoparticles (Fe 3 S 4 -Pd) as a signal indicator and matrix and functionalized pineal mesoporous bioactive glass (PBG) as the label for signal amplification. Fe 3 S 4 -Pd not only shows excellent electrocatalytic activity for the H 2 O 2 redox reaction but is also firmly immobilized on a magnetic glassy carbon electrode due to its excellent magnetic properties; because of the above features, this immunosensor exhibits excellent sensitivity and stability, respectively. Glutaraldehyde is used as a cross-linking agent to bond the secondary antibodies (Ab 2) with PBG. It is worth mentioning that the electron transfer rate between the electrolyte and electrode is decreased significantly by PBG-Ab 2 ; thus, a sensitive variation in the current signal is observed, and a further improvement in the sensitivity of the immunosensor is realized. More importantly, the proposed signal-off sensing system has a wide linear detection range of 500 fg/mL to 50 ng/mL for PCT and a low detection limit of 130 fg/mL, which promotes it as a promising detection method for the sensitive detection of other biomarkers. [ABSTRACT FROM AUTHOR]

• Bifunctional peptides that biomineralize gold clusters and specifically recognize antibody Fc domains. • Flexible fragmented-antibody are used as sensing substrate instead of using traditional micro-nano carrier. • The sensing platform fabricated by these strategies exhibit ultralow detection limit of 1.8 fg/mL. Non-competitive immunoassay systems often are used for detecting biomarkers, and their sensitivity depends on the arrangement mode of substrate and the property of signal label. In this work, a novel electrochemiluminescence (ECL) sensing platform utilizing split antibody fragments (Fab') 2 as substrate and self-designed nonapeptide H 2 N-CCYHWRGWV-COOH (CCYTAR) biomineralized gold nanocluster (Au NCs) as label was fabricated. Fixated (Fab') 2 domains on gold-plated electrodes via Au-S bonds could form well-ordered microarray with higher immune affinity than random antibody fixation. Besides, The CCYTAR nonapeptide not only could function as reductant and capping agent for synthesizing Au NCs, but also act as specific antibody immobilizer for recognizing Fc domains specifically. Also, related experiments verified that CCY and TAR, two independent regions of bifunctional nonapeptide, acted independently. In the end, the Cyfra 21-1 is employed as target to test the feasibility of all strategies, and the results confirmed that the sensing platform could be promising candidate for ECL-based biosensor fabrication in the future. [ABSTRACT FROM AUTHOR]

• An enzyme-free colorimetric immunosensor was designed for detection PCT. • MgFe 2 O 4 @Cys was first used as the sacrificial probe of the immunosensor. • MgFe 2 O 4 @Cys released Fe3+ under acidic condition and reacted with [Fe(CN) 6 4− can generate soluble PB. • PCT determination was established by measuring absorbance of generated PB. • It achieved an excellent result in human serum sample analysis. An enzyme-free immunosorbent assay using MgFe 2 O 4 modified with cysteine (MgFe 2 O 4 @Cys) as sacrificial probe for the detection of procalcitonin (PCT) was developed. MgFe 2 O 4 @Cys was linked with second antibody of PCT (Ab 2) by cysteine amino group and released Fe3+ under acidic conditions. Taking advantage of Fe3+ and [Fe(CN) 6 4− generating soluble Prussian blue (PB), a novel method of PCT determination was established by measuring the absorbance of the generated PB. Different from the traditional immunosensor detection mode, the enzyme-free colorimetric immunosensor in this work can not only avoid the interference of nano-enzymes or enzymes, but also has the advantages of rapid detection, low cost, high selectivity and sensitivity. Therefore, the developed immunosensor for PCT detection exhibited a wide linear response (0.0001–50 ng/mL) and a low detection limit (44.9 fg/mL). Additionally, the immunosensor exhibits satisfactory performance in human serum testing, which indicated its good application value in clinical diagnoses. [ABSTRACT FROM AUTHOR]

• An ECASE-based PEC sandwich-type immunosensor for PCT detection was designed. • The porous nanoarray BiVO 4 /CuS was prepared as matrix material. • The photocurrent could be significantly enhanced by the ECASE-based PEC strategy. • PS@Ab 2 bioconjugate act as labels for enhancing the sensitivity of PEC immunosensor. • The PEC immunosensor exhibited a low detection limit of 17.3 fg mL−1. A new, porous nanoarray BiVO 4 /Cu x S (PN-BiVO 4 /Cu x S) platform as an advanced signal amplification strategy under anodic bias on the process of electrochemical catalysis assisted self-enhancing based photoelectrochemical (ECASE-based PEC) without electron donors was established for ultrasensitive procalcitonin (PCT) detection. The system operated upon that the PN-BiVO 4 /Cu x S electrode could enhance separation of e−/h+ pairs under illumination of visible-light because the energy levels between BiVO 4 and Cu x S matched well. Afterwards, the photoexcited electrons could shift to working electrode as output signal, while the photoexcited holes could oxidize water under anodic bias to produce hydrogen peroxide (H 2 O 2) that was subsequently reduced by Cu x S, which resulted in significantly enhanced photocurrent intensity by electrochemical process. To further enhance the sensitivity of PEC immunosensor, amino-modified polystyrene (PS) nanoparticles act as labels for immobilizing secondary antibodies (Ab 2) to form PS@Ab 2 conjugates for construction of sandwich-type immunosensor on the basis of ECASE-based PEC strategy. The designed PEC immunosensor exhibited a linear concentration range from 50 fg mL-1 to 100 ng mL-1, with a low detection limit of 17.3 fg/mL (S/N = 3) for PCT, and achieved good selectivity, acceptable stability, and high sensitivity. This work first conducted the ECASE-based PEC system, and we believed it will provide a new perspective for developing innovative signal amplification toward detection of other biomarker in the future. [ABSTRACT FROM AUTHOR]