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Highlights • A convenient ECL biosensing method for selective detection of 5-hmC was developed. • The method is based on thiolated anchor probe DNA to immobilize 5-hmC-dsDNA. • The method can be used for detection of 5-hmC in genomic DNA. Abstract Herein, a novel and convenient electrogenerated chemiluminescence (ECL) biosensing method for the quantitative detection of 5-hydroxymethylcytosine (5-hmC) in genomic DNA was developed by employing thiolated anchor probe DNA to immobilize 5-hydroxymethylcytosine double-stranded DNA (5-hmC-dsDNA) and a ruthenium(II) complex-tagged reporter probe as an ECL probe. Briefly, the 5-hmC-dsDNA was firstly oxidized to 5-formylcytosine dsDNA (5-fC-dsDNA) by KRuO 4 in high yields. Subsequently, the thiolated anchor probe DNA is employed to help immobilize the 5-fC-dsDNA onto the gold electrode surface via the Au-S bond. An ECL probe DNA, labeled with a signal transducer − Ru(bpy) 2 (cbpy)NHS, hybridized with the anchor probe DNA on the electrode, resulting in an intensive ECL emission. The obtained ECL intensity was linearly proportional to the content of 5-hmC in the range from 0.0090% to 0.5761%, with the limit of detection calculated to be 0.0036% (S/N = 3). Finally, we applied the developed 5-hmC detection strategy in various mice tissues. It demonstrates that the content of 5-hmC measured by this method in different mice tissues vary significantly: 5-hmC is highest in brain and lowest in spleen. The success in assaying the mice tissues samples signifies its great promise in a broad range of practical applications for the quantitative detection of 5-hmC in genomic DNA. [ABSTRACT FROM AUTHOR]

A dual-emission molecularly imprinted mesoporous microspheres was designed for specific recognition and highly sensitive and selective determination of malachite green (MG). In this ratiometric fluorescent sensor, green fluorescent CdTe quantum dots (QDs)-doped into the core of silica mesoporous microspheres serves as a reference and provides a built-in correction for environmental effects. The other red fluorescent CdTe QDs are embedded around the pores of the silica microspheres as analytical tag. Then, molecular imprinting technique are integrated with the ratiometric sensor to provide high selectivity for MG. When the photoluminescence (PL) of red CdTe QDs is selectively quenched in the presence of MG, a visual color change from orange to green can be observed by naked eyes. The sensing method has a linear response in the range of 27.4 nM–137 μM with a detection limit of 17.0 nM. Moreover, there is an excellent recognition specificity for MG over other water pollutants. The applicability of this method is evaluated through the determination of MG in river water and lake water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Rapid and sensitive detection of thrombin has very important significance in biomedical and bioanalytical applications. In this study, a label-free and simple resonance light scattering (RLS) sensor based on MoS 2 nanomaterial is developed for ultrasensitive and highly selective detection of thrombin. In the presence of thrombin, the thrombin aptamer can transform into a G-quartet structure and combine with thrombin, resulting in dissociation of the random DNA (rDNA) in the solution. Once MoS 2 is introduced, the free rDNA can be adsorbed on the surface of MoS 2 to form a stable DNA1–thrombin–MoS 2 complex, which increases RLS signals. The sensor shows two linear ranges of 10 pM to 500 pM and 1 nM to 60 nM, and a detection limit of 0:71 pMfor detection of thrombin. Our sensor is a promising tool for clinical diagnosis of thrombin in human serum. Moreover, this work can offer new opportunities for the development of convenient sensor for detecting other proteins. [ABSTRACT FROM AUTHOR]

The selective detection of Cu 2+ and S 2− in pure water systems is very challenging. To address this problem, we here present a novel fluorescent probe CF536 for the reversible detection of Cu 2+ and S 2− in a 100% aqueous solution via a displacement approach based on fluorescence quenching and the ESIPT mechanism, and characterized by IR, NMR, HRMS and X-ray analysis. The introduction of Cu 2+ (1.0 equiv.) to the aqueous solution of CF536 led to quenching of the intense green fluorescence within 2 min. On the addition of S 2− (3.0 equiv.), the emission of the ESIPT probe soon recovered from the CF536 -Cu 2+ system due to the abolishment of paramagnetic Cu 2+ . The fluorescence “ON-OFF-ON” cycle can be repeated a minimum of 5 times by the alternate addition of Cu 2+ and S 2− , implying that CF536 is a renewable dual-functional probe. The probe displayed high selectivity, a rapid response time, excellent water solubility due to introduction of the extremely hydrophilic trihydroxyl group and outstanding anti-interference ability for its large Stokes shift of 101 nm (λ abs = 435 nm, λ em = 536 nm), thus making the method highly suitable for bioimaging. The probe CF536 was successfully used for fluorescent imaging of copper and hydrogen sulfide in living cells. [ABSTRACT FROM AUTHOR]

This paper describes a cyanine-based colorimetric and fluorescence probe for the sensitive and selective detection of hydrogen sulfide (H 2 S). The mechanism of H 2 S detection is based on the reaction of hydrosulfide anion with a disulfide bond. The resulting product of the reaction of the probe with hydrogen sulfide can be detected in a colorimetric assay as it changes a color of the reaction mixture from green to pink in aqueous solutions. Simultaneously, a 25-fold increase in the fluorescence signal of the probe upon its interaction with hydrogen sulfide gives a unique opportunity for the usage of this probe for in vivo detection of H 2 S. In addition, the present study demonstrates a potential of the newly developed chemosensor for the detection of increased concentrations of H 2 S in insect cells and alive C.elegans . [ABSTRACT FROM AUTHOR]

This work reports a novel [(C6) 2 Ir(dcbpy)]+ complex-sensitized NiO photocathode system and its first application for cathodic photoelectrochemical (PEC) immunoassay. The photocathode system was fabricated by hydrothermal and electrodeposition of hierarchical microspheres NiO film on the ITO electrode, followed by grafting photosensitizer [(C6) 2 Ir(dcbpy)]+ complex (C6 = Coumarin-6, dcbpy = 2,2′-bipyridyl-4,4′-dicarboxylate) through the condensation reaction of the –COOH group and NiO, and characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and UV−vis absorption spectra. The Ir(III) complex-sensitized NiO photocathode was demonstrated to possess favorable PEC characteristics with relatively strong, stable and reproducible PEC response under visible light illumination with dissolved oxygen in the electrolyte as electron acceptor. A possible mechanism for this sensitized system was speculated according to the value of HOMO and LUMO for [(C6) 2 Ir(dcbpy)]+. A simple PEC immunoassay based on the as-prepared photocathode system displayed high sensitivity as well as excellent selectivity for the determination of prostate-specific antigen (PSA). The present work demonstrated a promising future to iridium complex-sensitized NiO photocathode for PEC bioanalysis. [Display omitted] • A dye-sensitised NiO photocathode based on [(C6) 2 Ir(dcbpy)]+ shows favorable PEC characteristics. • [(C6) 2 Ir(dcbpy)]+-sensitised NiO photocathode was introduced for cathodic PEC immunoassay with PSA as a model analyte. • This method for PSA detection showed a low detection limit of 2.09 fg/mL. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, using copper as an etching agent, a novel and easy method to prepare porous graphene nanosheet (P-GR) was reported. With a large number of pores, more acidic groups and edge defect sites (EDSs) compared with graphene (GR), the prepared P-GR was used as an electrochemical biosensing platform for the first time. Using voltammetry and amperometry as detection methods, some important electroactive compounds, including dopamine (DA), ascorbic acid (AA), uric acid (UA), epinephrine (EP), guanine (G), adenine (A), xanthine (XA), hypoxanthine (HX), hydrogen peroxide and β-nicotinamide adenine dinucleotide (NADH) were employed to study their electrochemical responses on P-GR modified glassy carbon electrode (P-GR/GCE). The results show that P-GR/GCE exhibits better electrochemical performance to these substances compared with GR modified glassy carbon electrode (GR/GCE) and edge plane pyrolitic graphite electrode (PGE). The remarkable electrochemical advantage of P-GR makes it a promising material in electrochemical biosensing field. [Copyright &y& Elsevier]

Trenbolone (TB) is used for treating malnutrition in livestock and increasing their muscle mass. However, its excessive intake can lead to metabolic and reproductive disorders in animals. In addition, it causes adverse effects in humans even at very low concentrations. Herein, an innovative electrochemiluminescence (ECL) immunosensor based on a double-assisted signal amplification strategy has been proposed for the sensitive detection of TB. Nb 2 O 5 -decorated TiO 2 nanorods, with a large surface area, good biocompatibility, and excellent catalytic properties, were used as the substrates for the effective loading of TB antibodies. In addition, Co 3 O 4 -Co 3 (PO 4) 2 nanosheets, used as labels, improved the ECL signals and were used to incorporate TB antigens for designing competitive ECL immunosensors. Various experimental factors, such as the pH of the phosphate buffer solution, concentration of the co-reactant, and time of incubation, were examined. The proposed ECL immunosensor exhibited high sensitivity, good repeatability, and high stability for TB concentration and was successfully implemented for the analysis of real water samples. Under optimal conditions, the proposed immunosensor responded linearly to relevant concentrations of TB from 1.0 × 10−3 to 1.0 × 103 ng/mL, with a detection limit of 0.39 × 10−3 ng/mL (S/N = 3). Notably, this study fabricated a simple and ultrasensitive TB detection system with novelty of practical application in environmental monitoring. • This work proposed double-assisted signal amplification strategy due to synergistic effect of Nb 2 O 5 -TiO 2 and Co 3 O 4 -Co 3 (PO 4) 2. • The fabricated ECL immunosensor exhibits excellent selectivity and sensitivity towards TB detection. • TB was detected with LOD low as 0.39 × 10−3 ng/mL along with effective environmental applications. [ABSTRACT FROM AUTHOR]

• Fe-g-CNO nanosheets were synthesized by a facile and green method. • This sensor can detect F- in vitro with high sensitivity and selectivity. • This sensor achieves direct visualization of fluoride ions in living cells and teeth for diagnosis of dental fluorosis. Since excess fluoride ions may lead to a severe health hazard, it is imperative to design a facile and sensitive sensor to detect it in both environmental and biological systems. The reported methods are always subjected to some limits, hampering their practical application. Herein, a two-dimensional turn-on fluorescent sensor, Fe3+-integrated oxidized graphitic-phase carbon nitride nanosheets (Fe-g-CNO), was synthesized via a facile and green method for sensitive detection of fluoride ions. The interactions between the C-N/C = N moieties of oxidized graphitic-phase carbon nitride (g-CNO) and Fe3+ caused fluorescence quenching of g-CNO. Upon addition of F- ions, the fluorescence was recovered through the formation of complex of Fe3+ and F-. The limit of detection of the sensor was 1 × 10-6 M. Furthermore, this probe could be used as an imaging agent of fluoride ions in living cells and teeth for diagnosis of dental fluorosis. The work provides a safe and efficient platform for further environmental and biomedical uses. [ABSTRACT FROM AUTHOR]

• A highly sensitive ECL biosensing platform based on polyA-gold interaction and HCR was fabricated. • Multifunctional polyA probe which consists of a recognition part, a polyA part and a signal amplification part was designed. • The ECL method could even detect 5-hmC-dsDNA in mice tissues without sequence preference. 5-Hydroxymethylcytosine (5-hmC), as the sixth base in the mammalian genome, is increasingly regarded as an epigenetic marker with crucial biological functions. Herein, a highly sensitive electrogenerated chemiluminescence (ECL) sensing platform for double-stranded DNA containing 5-hmC (5-hmC-dsDNA) in genome was fabricated, which based on polyadenine-gold interaction combining with signal amplification of hybridization chain reaction (HCR). This biosensing strategy could be executed to detect 5-hmC in the native double-stranded DNA, irrespective of the specific sequences of DNA. Firstly, DNA methyltransferase (M.HhaI) was introduced to chemically modify the hydroxyl of 5-hmC in double-stranded DNA, which converted 5-hmC-dsDNA to amino-derived 5-hmC-dsDNA. Subsequently, DNA sequence containing polyadenine (polyA) was used as an anchor probe to incorporate the derivatized 5-hmC-dsDNA by amide reaction to form compound DNA and then completely assembled onto the gold electrode surface through preferential polyA-gold interaction. Subsequently, two designed DNA hairpin probes which can alternately hybridize with each other were linked to the signal amplification part of multifunctional polyA probes, forming ultra-long nicked double helix structures. Finally, ECL indicator of Ru(phen) 3 2+ molecules were intercalated into the groove of the nicked DNA double helices, resulting greatly increased ECL intensity. Therefore, the quantitatively analysis of 5-hmC-dsDNA could be obtained relied on the relationship between the ECL intensity and 5-hmC-dsDNA content. The detection limit of this method for 5-hmC-dsDNA was 0.0001 % (S/N = 3). Moreover, the biosensing platform was successfully applied to detect 5-hmC-dsDNA in mice tissue samples with satisfactory results, manifesting its great potential application in clinical analysis. [ABSTRACT FROM AUTHOR]

The construction of robust photoelectrochemical (PEC) transducing platforms mediates the feasibility and performance of the PEC biosensors. In this work, perylene tetracarboxylic acid (PTA) nanoassemblies were exploited as robust semiconductors to form type II heterojunctions with In 2 O 3. The prepared organic/inorganic heterojunctions show high PEC transducing performances. The carboxyl groups of PTA avoid the additional surface functionalization for covalent immobilization of capturing elements which will diminish the transducing performance. This enables the facile construction of PEC immunosensing platforms. More importantly, Ag@CeO 2 nanoparticles were used as energy level matching nanolabels to develop a signal-on PEC immunosensing method. A linear response from 0.1 pg/mL to 100 ng/mL with a detection limit of 63.1 fg/mL was achieved for a typical protein biomarker carcinoembryonic antigen (CEA). • Sandwich-type immunoassay enables sensitive PEC detection. • PTA as robust semiconductors to form type II heterojunctions with In 2 O 3. • The carboxyl groups of PTA provide a large number of active sites. • The biosensor detection CEA exhibited the detection limit of 63.1 fg/mL. [ABSTRACT FROM AUTHOR]

• A sandwich-type signal off PEC sensor was constructed for PCT detection. • The photoactive matrix was Au NPs/BiOI NSs/B-TiO 2 NPs. • PbS/Co 3 O 4 was as a quenching signal label for signal amplification. • The PEC sensor exhibited a low detection limit of 0.02 pg/mL. A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO 2 nanoparticles (Au NPs/BiOI NSs/B-TiO 2 NPs) as photoactive matrix and PbS quantum dots/Co 3 O 4 polyhedron (PbS/Co 3 O 4) 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-TiO 2 NPs electrode forming Au NPs/BiOI NSs/B-TiO 2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co 3 O 4 , 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. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (S. aureus) infections pose a serious threat to human health worldwide. Therefore, selective and accurate detection of S. aureus is necessary for preventing infections. Herein, we design the colorimetric-electrochemical sensing platform based on specific oligonucleotide (SA31 aptamer)-tunable oxidase-like activity of mesoporous polydopamine/MnO 2 (MPDA/MnO 2) nanozymes for the S. aureus detection. The MPDA/MnO 2 nanozymes possess excellent oxidase-like activity and electrochemical property. MPDA/MnO 2 nanozymes can catalyze the oxidation of TMB to generate TMB+ (blue color) and TMB2+ (yellow color) products. The oxidase-like activity of MPDA/MnO 2 can be inhibited when the SA31 is adsorbed on the surface of the nanozymes. In the presence of S. aureus, SA31 aptamer desorbs from MPDA/MnO 2 surface based on the specific identification between S. aureus and aptamer, resulting in the recovery of their oxidase-like activity. Based on the different oxidative degree of TMB, the color of sensing solution changes from blue to yellow, the electrochemical signals also have changed simultaneously. The colorimetric-electrochemical sensing platform can accurately detect S. aureus, showing a low detection limit in 3 CFU/mL (S/N = 3). Furthermore, the dual-mode sensing platform can be utilized for the accurate and specific detection of S. aureus in real sample with the recovery of 95.15%− 115.28%. This work based on SA31 aptamer-tunable oxidase-like activity of MPDA/MnO 2 nanozymes provides a dual-mode assay for specific and accurate detection of S. aureus. • A dual-modal strategy was designed to detect S. aureus based on the colorimetric-electrochemical sensing platform. • The SA31 can regulate the oxidase-like activity by adsorption and desorption on the surface of MPDA/MnO 2 nanozymes. • The electrochemical behavior of the electrode can be adjusted by the specific binding between aptamers and S. aureus. • This dual-modal sensing platform possesses low detection limit (3 CFU/mL) and wide linear range. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ultrasensitive electrochemical aptasensor was developed for detecting Pb2+. • Au@p-rGO was applied as support for immobilizing the aptamer. • Au NPs@GO as signal probe exhibited high electrocatalytic activity towards H 2 O 2. • The aptasensor displayed low detection limit of 1.67 pmol/L for Pb2+. Abstract A sensitive electrochemical aptasensor was designed based on gold modified graphene nanocomposite with different morphologies for the detection of lead ion (Pb2+). Specifically, a sulfydryl-labeled substrate strand (Apt1) and a sulfydryl-labeled catalytic strand (Apt2) were devised in fabricating the electrochemical aptasensor. Gold modified porous reduced graphene oxide (Au@p-rGO) was synthesized and applied as support for immobilizing the Apt1. And gold modified graphene oxide (Au NPs@GO) was employed as signal probe and connected with Apt2 to realize the immobilization of it on the electrode by means of the principle of complementary base pairing. The current signal can be obtained by recording the electrocatalytic conditions toward H 2 O 2. The Pb2+-dependent DNAzyme could play a role when Pb2+ existed. With the increase of the concentration of Pb2+, the current response revealed a diminishing signal, thus realizing the sensitive detection of Pb2+. Under the optimal conditions, the fabricated electrochemical aptasensor exhibited a linear response toward Pb2+ ranging from 5 pmol/L to 1 μmol/L, together with a low limit of detection of 1.67 pmol/L. Moreover, the prepared aptasensor displayed outstanding selectivity, acceptable stability and superior reproducibility for detecting Pb2+. This proposed tactics may provide reference and potential applications for detecting some other heavy metal ions. [ABSTRACT FROM AUTHOR]

Graphical abstract A simple and sensitive electrochemical biosensor is constructed for the detection of telomerase activity based on the electrocatalysis of Pd/MIL101-NH 2 as a redox mediator. Highlights • A sensitive electrochemical biosensor is constructed for the detection of telomerase activity based on Pd/MIL101-NH 2. • This biosensor shows low limit of detection and wide dynamic correlation of telomerase activity. • The proposed method was enzyme-free and PCR-free without the requirement of any additional separation steps. Abstract As a critical biomarker for early cancer diagnostics, telomerase activity has attracted extensive attention concerning its monitoring and detection. Herein, a simple and sensitive electrochemical biosensor is constructed for the detection of telomerase activity based on the electrocatalysis of Pd nanoparticles anchored on amine functionalized Cr-based metal-organic frameworks (Pd/MIL101-NH 2) as a redox mediator. Upon telomerase triggered extension, the telomerase activity is related to the amount of the adsorbed electrocatalyst, leading to the different electrochemical signals for readout. Integrating with the efficient electrocatalysis of Pd/MIL101-NH 2 towards oxidation of acetaminophen, this biosensor shows wide dynamic correlation of telomerase activity from 5 × 102 to 1.62 × 107 HeLa cells mL−1 and the limit of detection was calculated to be 11.25 HeLa cells mL−1, providing a powerful platform for detecting telomerase activity. [ABSTRACT FROM AUTHOR]

Specific and sensitive detection method for anti-cyclic citrullinated peptide antibody (anti-CCP) is highly in demand for the early diagnosis of rheumatoid arthritis (RA). In this work, a label-free electrogenerated chemiluminescence (ECL) immunosensor for the detection of anti-CCP was proposed based on the application of an interfacially synthesized asymmetric heterogeneous nanomaterial. Dumbbell-like polyaniline-gold (PANI-Au) nanocomposite show excellent synergetic enhancement effect on the ECL behaviors of graphite-like carbon nitride (g-C 3 N 4 ). The formation of electrostatic complex between g-C 3 N 4 and PANI-Au composite improves the interfacial stability of hydrophilic g-C 3 N 4. The synergetic enhancement effect of PANI and Au NPs was confirmed by tailoring the morphology of the nanocomposite. An ECL immunosensor was constructed using asymmetric PANI-Au incorporated g-C 3 N 4 as a sensing platform. The presence of Au NPs enables the facile immobilization of the recognition element for anti-CCP antibody. The simple preparation method endows the good reproducibility and stability for the proposed ECL immunosensor. A wide linear range of 0.001 ∼ 15 ng mL −1 with a lower detection limit of 0.2 pg mL −1 was obtained for the determination of anti-CCP antibody. The proposed ECL method may has promising application in other bioassays. [ABSTRACT FROM AUTHOR]

An original electrochemiluminescent (ECL) luminophore porphyrin nanosphere–graphene oxide composite (TCPP NS-GO) was prepared. The TCPP NS-GO could produce greatly enhanced ECL in buffer with potassium peroxydisulfate (K 2 S 2 O 8 ) as the co-reactant. The enhancement ECL mechanism of TCPP NS-GO/K 2 S 2 O 8 system was investigated in detail. Moreover, The TCPP NS-GO composite had an abundant surface functional group to expand its application, which exhibited high sensitivity and selectivity to Fe 3+ . The wide linear relationship between ECL intensity and Fe 3+ concentration from 0.002 to 5.128 μmol L −1 (R 2 = 0.998) was found with the detection limit as low as 1 nmol L −1 . The ECL quenching mechanism of Fe 3+ was proved by UV-vis absorption spectroscopy, Fluorescence emission spectroscopy (FL) and Fourier transform infrared spectroscopy (FT-IR) analysis technology. [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]

For giving birth to a healthy baby without Down’s syndrome, screening the level of alpha fetoprotein (AFP) and free-beta human chorionic gonadotropin (β-hCG) in maternal serum has been a routine examination for all gravidas. However, many assays only detect one target once time, which requires large samples and is low-throughput and costly. Herein, we describe a sensitive and inexpensive multiplex detection assay based on inverse opal structure hydrogel barcodes with poly(ethylene glycol) diacrylate (PEG-DA), poly(ethylene glycol) (PEG) and acrylic acid (AA) hybrid components. The polymerized PEG-DA hydrogel could guarantee the stabilities of the inverse opal structure, while the AA could offer active carboxyl groups for the probe immobilization. In addition, the interconnected pores of the inverse opal structure caused by PEG could also provide channels for biomolecules diffusing and reaction into the voids of the barcodes. The immunoassay results of our detection on AFP and β-hCG showed acceptable accuracy and detection reproducibility, and the results were in acceptable agreement with those from common clinic method for the detection of practical clinical samples. Thus, the new platform is apparently suitable for multiplex detection of Down’s syndrome. [ABSTRACT FROM AUTHOR]

One-dimensional ZnO@In 2 O 3 core@shell nanofibers (CSNFs) were synthesized via a facile coaxial electrospinning method followed by high-temperature pyrolysis treatment. The obtained nanofibers have a well-defined core@shell structure with ZnO as the core and In 2 O 3 as the shell. Compared with the pure ZnO nanofibers and pure In 2 O 3 nanofibers, the ZnO@In 2 O 3 CSNFs based sensor presents the highest response to ethanol (31.87 at 100 ppm) at an operating temperature of 225 °C, which can be ascribed to the formation of a completely electron depletion layer in In 2 O 3 shell. Moreover, the ZnO@In 2 O 3 CSNFs based sensor also demonstrates outstanding selectivity, excellent stability and low detection limitation (∼5 ppm) to ethanol vapor. The ultraviolet photoelectron spectroscopy confirms a type-II heterojunction formed at the interface of ZnO core and In 2 O 3 shell. The main mechanism for the enhanced performance of ZnO@In 2 O 3 CSNFs gas sensor is the depletion modulating of In 2 O 3 shell layer in electron transfer. These results are valuable for the practical application of ZnO@In 2 O 3 CSNFs in ethanol detection. [ABSTRACT FROM AUTHOR]

The content of Cytokeratin-19 fragments (CYFRA21–1) is correlated with the metastasis and survival status of patients with lung cancer, and the expression level is higher in the serum of nearly half of non-small cell lung cancer patients. Using CYFRA21–1 as the detection target, a sandwiched photoelectrochemical (PEC) immunosensor based on CdS/Ni(OH) 2 was designed and constructed successfully. Herein, due to the matched energy band structure, the Ni(OH) 2 modified CdS nanorods made up for the shortcomings of CdS photogenerated electrons and holes that were easy to recombine quickly. In addition, the Z-type heterojunction composite material CdSe@MoSe 2 was used as a label to improve the sensitivity of the sensor. On the one hand, MoSe 2 , with excellent resistance to light corrosion, could absorb and utilize near-infrared light due to its narrow band gap, which expanded the light source available for the sensor. On the other hand, the photo-generated charge on CdSe@MoSe 2 would be transferred to the CdS/Ni(OH) 2 , thereby enhancing the photocurrent of the sensor. The detection limit of this sensor was as low as 0.027 pg mL−1 due to the above advantages, and the sensor's detection range was from 0.100 pg mL−1 to 500 ng mL−1. Additionally, the sensor showed good stability, selectivity and reproducibility, which provided a feasible method for the detection of such tumor markers. • The CdS/Ni(OH) 2 has excellent photoelectric response as the substrate. • Z-type heterojunction CdSe@MoSe 2 was firstly used as a label to improve the sensitivity of the sensor. • The PEC platform showed desired high sensitivity and stability for CYFRA21-1 detection. [ABSTRACT FROM AUTHOR]

As a promising alternative for conventional wet electrode made from silver/silver chloride (Ag/AgCl), micro-needles array (MNA)-based dry electrode has gained extensive attention. The low contact impedance between the MNA-based dry electrode and skin interfaces is pivotal for the acquisition of high quality biopotential, especially for long-term monitoring. In this report, we study, for the first time, the use of organic conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as the interface material of MNA-based dry electrode to improve its electrochemical performance. The interface performance of PEDOT coated dry electrode was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The mean impedance magnitudes (measured from skin) of PEDOT dry electrode are around 7.5±3.2kΩ at 2Hz and 2.7±1.2kΩ at 100Hz, while the values are 274.2±54.6kΩ and 31.8±9.6kΩ for gold dry electrode, and 547.1±374.2kΩ and 79.9±10.3kΩ for commercial electroencephalography (EEG) wet electrode. The charge storage capacity (measured on rat skin sample) of PEDOT and gold was 461.48μC and 1.8296μC, respectively. These improvements provided by PEDOT interface material can significantly contribute to MNA-based dry electrode for recording or electrostimulation. Compared with commercial EEG wet electrode, similar biopotential signals can be acquired with our PEDOT-coated MNA-based dry electrodes. [ABSTRACT FROM AUTHOR]

Advanced electrode material — pg-C 3 N 4 /CoMn 2 O 4 which has superior electrochemical analysis and sensing performance to detect heavy metal ions was prepared by a facile strategy. [Display omitted] • A nanocomposite system of porous graphitic carbon nitride and CoMn 2 O 4 (pg-C 3 N 4 /CoMn 2 O 4) was constructed. • The incorporation of CoMn 2 O 4 into the pg-C 3 N 4 enabled a better electron transfer kinetics. • The pg-C 3 N 4 /CoMn 2 O 4 generates great synergistic effect with high surface area and extraordinary electronic conductivity. • The pg-C 3 N 4 /CoMn 2 O 4 exhibits superior electrochemical sensing performance to detect heavy metal ions. The combination of semiconductors and binary transition metal oxides has drawn growing interest in terms of their enhanced electrochemical analysis performance in electrochemical sensing. A new type of highly sensitive and selective sensor was designed and developed by constructing a nanocomposite system of porous graphitic carbon nitride and CoMn 2 O 4 (pg-C 3 N 4 /CoMn 2 O 4) to detect heavy metal ions of Cd(II) and Pb(II). The morphological and structural characteristics of pg-C 3 N 4 /CoMn 2 O 4 nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The optimized current responses obtained through the square wave anodic stripping voltammetry (SWASV) of Cd(II) and Pb(II) increased linearly with their concentration in wide linear dynamic ranges of 0.5–7.0 μM and 0.2–4.4 μM, respectively, as well as low detection limits of 0.021 μM for Cd(II) and 0.014 μM for Pb(II). Further, the proposed sensor was successfully applied for the determination of Cd(II) in actual water samples accomplished with the value of recoveries ranging from 93.0%–106.0%. In addition, good anti-interference, favorable reproducibility, excellent stability and repeatability of the sensor enable it feasible for the detection of heavy metal ions. [ABSTRACT FROM AUTHOR]

• Microfluidics-based magnetic structure color hydrogel microcarrier is proposed. • The microcarrier had high sensitivity and specificity for multiplex analysis. • The microcarrier can detect sample with extremely low volume (as low as 10 μL). • The magnetic control effect improves the sensitivity and efficiency of detection. • The microcarriers are potential for the diagnosis of bladder cancer. Bladder cancer is one of the most common malignant tumors of the urinary system with a significantly increased incidence in recent years. Tumor biomarkers detection with high specificity and sensitivity bears great significance in clinical diagnosis and treatment. Here, we propose a novel microfluidics-based magnetically responsive structural color hydrogel microcarrier as the multiplex detection platform, with the advantages of easy accessibility and high sensitivity. The resin material with the superior mechanical property was applied to prepare the inverse opal as the framework, in whose gaps perfused with a multifunctional hydrogel composed of polyethylene glycol diacrylate (PEGDA), acrylic acid (AA) and Fe 3 O 4 nanoparticles. The composition enabled the microcarrier with high mechanical strength, low non-specific molecular adhesion, and directional magnetic motion ability, which significantly improved the detection efficiency of the platform. The results demonstrated that our detection system had good sensitivity and reliable specificity in the multiplex analysis of bladder cancer-related protein nuclear matrix protein 22, human bladder tumor antigen and fructose-1,6-diphosphate. Furthermore, the microcarriers were proved to have an ideal application prospect in clinical diagnosis and monitoring. Therefore, magnetically responsive structural color hydrogel microcarriers were suitable for the construction of liquid chips for bladder cancer protein markers. [ABSTRACT FROM AUTHOR]

• A novel antifouling DNA sensor is proposed for BRCA1 ultrasensitive detection. • The needle-like Eu:Co 3 O 4 was in situ synthesized on conductive Ni foam as the basic photocathode. • CuS nanoparticles was grown on the surface of Eu:Co 3 O 4 /Ni foam through a SILAR to enhance the PEC response. • The antifouling interface was applied for DNA sequence fixing to improve the sensitivity of the sensor. • The sensor for BRCA1exhibits a low detection limit of 0.38 fM. In this work, the photosensitive needle-like Eu: Co 3 O 4 was synthesized on conductive nickel foam (Ni foam) in situ via hydrothermal and subsequent heat treatment, and as the basic material to construct an antifouling photoelectrochemical (PEC) DNA sensor for BRCA1 (breast cancer marker) detection. Ni foam has a great frame structure, which could well control the morphology and size of materials. Then CuS nanoparticles could easily grow on the surface of Eu: Co 3 O 4 /Ni foam through a sequential ionic layer adsorption reaction to further enhance the PEC response. For BRCA1 sensitivity analyzing, the excellent antifouling property was realized rely on the conjugation of amino-terminal poly(ethylene glycol) (PEG-NH 2). The developed PEC sensor displayed an outstanding stability and great sensitivity under the dissolved oxygen environment, and Ni foam PEC electrode provided potential application for other photosensitive materials-controlled preparation. [ABSTRACT FROM AUTHOR]

• A novel molecularly imprinted photoelectrochemical sensor is proposed for BPA ultrasensitive detection. • The In 2 S 3 nanoparticles is used to sensitized flower-like AgBiS 2 to provide basic PEC response. • CdS is in situ generated on AgBiS 2 /In 2 S 3 via ion exchange reaction for further improve the stability of the sensor. • The sensor for BPA exhibits a low detection limit of 0.18 nM. As one of the fashionable ways for molecular recognition site display, molecular imprinting technology has attracted increasing attention as a means to design complementary parts of target molecules. Herein, a novel molecularly imprinted photoelectrochemical (PEC) sensor is designed for bisphenol A (BPA) analysis based on In 2 S 3 /Cd2+ sensitized flower-like AgBiS 2. The bimetallic sulphide AgBiS 2 possess a three-dimensional flower-like structure that is assembled by using nanosheets, the outstanding structure provides a favorable surface morphology for fixing other photoactive nanomaterials. Thus, photosensitizer In 2 S 3 nanoparticles are used to sensitize AgBiS 2 , and an enhanced PEC response is achieved thanks to the matched band gap and the electron delivery synergy. In order to acquire a more stable and higher photocurrent, Cd2+ is dropped directly on the AgBiS 2 /In 2 S 3 electrode to generate CdS in situ, the generated CdS coupled with In 2 S 3 co-sensitize AgBiS 2 and realized satisfactory PEC basic response. The molecularly imprinted membrane is prepared by electrodeposition of pyrrole solution in the presence of BPA. Under optimized detection conditions, the proposed PEC sensor displays a wide detection range between 0.0005 and 50 μM for BPA, and with a low detection limit 0.18 nM. The skillful strategy also displays excellent stability and great reproducibility. [ABSTRACT FROM AUTHOR]

• It was the first application of GaON in PEC immunosensors. • An effectively cascade-like energy band edge level was obtained, which can effectively amplified PEC response. • The BiVO 4 /GaON/CdS label-free PEC immunosensor was successfully developed for determination of procalcitonin. In this paper, GaON with excellent photoelectrochemical (PEC) performance was adopted in PEC immunosensor for the first time. Based on CdS sensitized BiVO 4 /GaON composite material, a label-free PEC immunosensor was successfully developed for determination of procalcitonin (PCT). Firstly, BiVO 4 nanoarray was prepared by electrodeposition. Then GaON was added to form the BiVO 4 /GaON composite material, due to the greatly increasing charge transfer efficiency, the PEC signal increased by about 3 times. At last, CdS grew in situ on BiVO 4 /GaON composite that further expanded the light absorption range and improved the light utilization, and the PEC signal further increased again. This PEC immunosensor has a good linear relationship of 0.1 pg mL−1 - 50 ng mL−1 and the detection limitation of 0.03 pg mL−1 is calculated. Importantly, the BiVO 4 /GaON/CdS immunosensor platform showed good specificity and stability, and serum sample analysis have been performed with satisfactory results. [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]

An electrochemical biosensor was fabricated for reliable and highly sensitive microRNA-21 assay by catalytic hairpin assembly and Pd nanoparticles-DNA layered nanoreticulation, providing a new way in the biochemical assay for detecting microRNA-21 in early disease diagnosis. • The sensitive biosensor was constructed for the detection of miR-21 based on CHA and Pd NPs-DNA LNR. • This biosensor shows low limit of detection and wide dynamic correlation of miR-21, providing a powerful platform for detecting miR-21. • The proposed method was enzyme-free, PCR-free, and convenient without the requirement of any additional separation steps. Herein, a Pd nanoparticles-DNA layered nanoreticulation (Pd NPs-DNA LNR) sensor was assembled to a graphene oxide (GO)-modified electrode by catalytic hairpin assembly (CHA) and a self-assembly process. In this process, GO was modified on the electrode surface to provide -COOH sites for DNA bonding. Moreover, with the CHA circular amplification strategy, many single DNA1 were exposed to be able to be bound with Pd-DNA2 for the formation of the Pd NPs-DNA LNR, which enabled the ultrasensitive detection of microRNA-21 (miR-21) with a low limit of detection 63.1 aM. This strategy combines the amplification technology of CHA and Pd NPs-DNA LNR with Pd NPs. Such a layered nanoreticulation material can support abundant Pd NPs to avoid aggregation and obtain enhanced electrochemical signals. Significantly, this method can be successfully applied in tumor cell lysates and provides a neoteric channel for early disease diagnosis. [ABSTRACT FROM AUTHOR]

• This split-type sensor separates the two processes of antigen-antibody specific recognition and photoelectric conversion. • THCH as extra electron donor is released through the controlled-release strategy. • CdS sensitized Bi 2 Sn 2 O 7 forms a heterojunction as the matrix to provide basic PEC response effectively. • The biosensor for sensitive detection PCT exhibited the detection limit of 0.17 pg/mL. A split-type photoelectrochemical (PEC) sensor for procalcitonin (PCT) detection was successfully prepared. This split-type sensor adopted controlled-release strategy, which separated the two processes of antigen-antibody specific recognition and photoelectric conversion, so that the two processes can be performed independently. In addition, CdS sensitized Bi 2 Sn 2 O 7 is combined for the first time to form a heterojunction as the matrix to provide the basic PEC response, which could effectively absorb visible-light, and reduced electron-hole pair recombination, ensured the stability of the sensor. Distinctly important, the skillfully process was performed in a 96-well plate where the specific reaction was completed proceeded between antigen and antibody. For improving sensitivity of the sensor, acetylcholinesterase (ACHE) connected to SiO 2 nanospheres (SiO 2 NSs) modified by second antibody (Ab 2 -ACHE@SiO 2 NSs) was designed, the thiocholine (THCH) can be released when acetylthiocholine iodide (ATCH) exists, and the THCH as an electron donor could enhance PEC response. The proposed PEC immunoassay with high-performance photosensitive materials, and the smart electron donor released strategy have a wide detection liner range from 0.0005 to 100 ng/mL with a low detection limit of 0.17 pg/mL, also provide great clinical diagnostic potential for other target proteins. [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]

• Ultrasensitive electrochemical aptasensor was fabricated for detecting Pb2+. • AuPd@Fe-MOFs labeled DNA was firstly applied to produce the electrical signal. • Au@MoS 2 /rGO was utilized as sensing platform to construct the aptasensor. • The aptasensor displayed low detection limit of 0.07 pmol/L for Pb2+ detection. In this work, an electrochemical aptasensor was proposed by using gold-modified molybdenum disulfide/reduced graphene oxide (Au@MoS 2 /rGO) nanocomposite and gold-palladium (AuPd)-modified MIL-88 (Fe) metal-organic frameworks (AuPd@Fe-MOFs) for sensitive detection of lead ions (Pb2+). The 8–17 DNAzyme consisting of a substrate strand (Apt1) and a catalytic strand (Apt2) was used to construct the aptasensor. Au@MoS 2 /rGO nanocomposite was applied as the sensing platform to immobilize the mercapto-group-labeled Apt1. Meanwhile, AuPd@Fe-MOFs was employed to label Apt2, which showed excellent catalytic ability toward H 2 O 2. In the presence of Pb2+, the Apt1 of the DNAzyme was catalytically cut off, decreasing the amount of AuPd@Fe-MOFs. The current response was correlated to the Pb2+concentration, thereby achieving Pb2+ detection. Under the optimal experimental conditions, the fabricated aptasensor showed a highly linear response for Pb2+ in the range from 5.0 pmol/L to 2.0 μmol/L, with a detection limit of 0.07 pmol/L. Additionally, the proposed electrochemical aptasensor exhibited excellent selectivity, stability and reproducibility. Moreover, the proposed aptasensor demonstrated good performance in real water sample analysis, making it promising for use in Pb2+ detection in environmental monitoring. [ABSTRACT FROM AUTHOR]

• A PEC aptamer sensor for 17β-estradiol detection was introduced. • The Mo doped porous BiVO 4 nanoarray/Bi 2 S 3 as sensing platform for immobilization of aptamer. • The Mo-p BiVO 4 /Bi 2 S 3 presented a high PEC signal by supplying additional free electrons. • The nanoarray structure provided large specific surface area and large number of binding sites. • The PEC aptamer sensor exhibited a low detection limit of 3.2 × 10−4 pM. A new porous nanoarray is constructed as sensing platform of photoelectrochemical (PEC) biosensor for detection of 17β-estradiol (E2) by using aptamer. The molybdenum (Mo) ions doped into porous bismuth vanadate (Mo-p BiVO 4) nanoarray by electrodeposition of BiOI nanoarray. Then, the bismuth sulfide (Bi 2 S 3) nanoparticles are grown in-situ on the surface of Mo-p BiVO 4 by the self-sacrificial synthesis method to form novel Mo-p BiVO 4 /Bi 2 S 3 heterojunction. Herein, the Mo-p BiVO 4 /Bi 2 S 3 heterojunction presents a high PEC signal because of Mo-p BiVO 4 could increase electron-hole separation yield by supplying additional free electrons, furthermore the heterojunction of Mo-p BiVO 4 /Bi 2 S 3 could promote ultrafast transfer of charge and inhibit the recombination of e−/h+ pairs by presenting cascade band-edge levels under irradiation of the visible light. Moreover, the nanoarray structure has large specific surface area, which could accelerate electron transfer and provide large number of binding sites to immobilize aptamer. This PEC aptamer sensor exhibits high sensitivity with a detection limit 3.2 × 10-4 pM and a good photocurrent response toward target E2 in the range of 1 × 10-3 - 5 × 102 pM. Good specificity and stability are acquired for analysis of E2 in human urine. Importantly, this designed sensor platform of Mo-p BiVO 4 /Bi 2 S 3 heterojunction provides a new promising application for other environmental estrogen analysis. [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]

• Novel potential and current type electrochemical chiral amino acid biosensor. • Left/right-handehelix carbon nanotubes as chiral recognition substrate material. • Synergistic effect and interaction of L/D-DHCNT and L/D-Cys. • Realize the detection and analysis of actual samples of amino acids. • Quantitative detection of amino acids enantiomers based on both potential and current signals. Novel chiral amino acids biosensor based on both potential difference and current ratio simultaneously was first established by employing left/right-handed double helix carbon nanotubes (L/D-DHCNT) with chiral structure as substrate material, and by self-assembly anchoring L/D-cysteine (L/D-Cys) on the surface of the left/right-handed double helix carbon nanotubes@Polypyrrole@Au nanoparticles nanocomposites (L/D-DHCNT@PPy@AuNPs). In this work, L/D-DHCNT@PPy@AuNPs@L/D-Cys was successfully constructed via a facile and environment-friendly process. Interestingly, in order to obtain highly dispersed AuNPs deposited on L/D-DHCNT, polypyrrole polymerized from pyrrole acts as a locating agent. Owing to the combination of unique performance of the L/D-Cys and L/D-DHCNT with chiral structure, and PPy and AuNPs with outstanding conductivity, an extremely efficient electrochemical chiral biosensing system was constructed that exhibited enhanced conductivity, sensitivity and chiral recognition capacity for tyrosine (Tyr), tryptophan (Trp) and glutamic acids (Glu) enantiomers. Utilizing both the potential difference and current ratio signal to commendably realize the electrochemical recognition and quantitative determination of amino acid enantiomers in their racemic solution. In addition, achieving the detection of Tyr in tablet samples by fabricated ultra-efficient electrochemical chiral biosensing system. Therefore, L/D-DHCNT@PPy@AuNPs@L/D-Cys as novel and ultrasensitive chiral biosensing system possesses the capability of chiral recognition of amino acid enantiomers, and it opens up the potential application of L/D-DHCNT@PPy@AuNPs@L/D-Cys in the field of chiral biosensors. [ABSTRACT FROM AUTHOR]