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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]

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]

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]

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]

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]

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]