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The development of a specifically sensitive approach for CA15-3 detection is of great significance for the early diagnosis and treatment monitoring of breast cancer. In the present work, an electrochemiluminescence (ECL) immunosensor was constructed for the sensitive and selective detection of CA15-3 based on a dual-quenching strategy. Ru-(dcbpy)32+, poly-(ethylenimine) (PEI), and gold nanoparticles (AuNPs) were immobilized on dendritic mesoporous silica nanoparticles (DMSNs) (Ru-PEI/AuNPs@DMSNs) with high ECL efficiency due to the high loading amounts of Ru-(dcbpy)32+, the shortened electron-transfer path between the luminophore and coreactant, and the excellent conductivity and localized surface plasmon resonance effect of AuNPs. In the presence of CA15-3, a Cu2O nanoparticles coated with poly-(dopamine) (Cu2O@PDA) nanocomposite was introduced to the synthesized Ru-PEI/AuNPs@DMSNs through antigen–antibody interaction, resulting in a remarkable ECL quenching due to the dual quenchers of Cu2O and PDA. Under the optimal conditions, the fabricated sensor was used to detect CA15-3 in a wide linear range of 5.0 × 10–5–6.0 × 102 U mL–1 with a low limit of detection of 2.4 × 10–6 U mL–1. The dual-quenching ECL immunosensor was successfully applied for the determination of CA15-3 in patient serum, indicating the potential applicability of the present immuosensor for the clinical determination of CA15-3 and other cancer biomarkers. [ABSTRACT FROM AUTHOR]

Development of an effective and convenient sensor for sensitive detection of nitrites is of great concern since excessive amounts of nitrites can be harmful to both human health and the environment. In this work, Cu-MOF modified exfoliated graphite paper (EGP) was employed as a signal reporter to enable the visual and electrochemical dual-mode sensing of nitrites. Cu-MOFs were in situ synthesized on EGP, which exhibited an excellent oxidase enzyme-like activity to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) into its oxidation product (oxTMB). The multi-layer structure and the superior electrical conductivity of EGP not only facilitated the loading of the Cu-MOF nanozyme for colorimetric sensing but also enabled its use as an underlying backbone to support electroanalysis. Based on the recognition of nitrite through a highly specific diazo reaction between nitrite and oxTMB, the addition of nitrite caused the colorimetric sensing solution to change color from blue to green, which allowed for the colorimetric sensing of nitrite with a limit of detection (LOD) of 8.5 × 10−6 mol L−1. Meanwhile, the Cu-MOF/EGP electrochemical platform was employed for ratiometric detection of nitrite based on the electrochemical oxidation of nitrite and TMB. Compared with the colorimetric mode, the electrochemical mode possessed higher sensitivity with a LOD of 5.4 × 10−7 mol L−1, indicating the high sensitivity and accuracy of the proposed dual-mode sensing strategy. Furthermore, the determination of nitrite in different pickled food samples is demonstrated. [ABSTRACT FROM AUTHOR]

A new kind of internal reference probe was developed to construct a ratiometric electrochemical sensor for accurate and sensitive Cd2+ detection. AuPt nanoclusters (AuPt NCs) were synthesized and then evenly distributed on reduced graphene oxide (rGO) to form a nanocomposite (AuPt–rGO), which showed peroxidase-like activity and catalyzed the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP) in the presence of H2O2. It was found that DAP was further reduced on the electrode with a constant current intensity whether Cd2+ was added or not, which enabled it to function as an excellent internal reference probe. Thus, the ratio between the reduction currents of Cd2+ and DAP (iCd2+/iDAP) was proposed to monitor Cd2+ based on the ratiometric strategy. Additionally, the high surface area and good conductivity of AuPt–rGO endowed the sensor with enhanced sensitivity. A wide linear range and a low limit of detection were measured at 5.0 × 10−8–1.0 × 10−4 mol L−1 and 3.1 × 10−8 mol L−1, respectively. Compared with the single signal sensors, this ratiometric sensor presents more accuracy and reliability in the detection of Cd2+, facilitating the quantification of Cd2+ concentration in different water samples with good recoveries. The novel internal reference probe proposed here shows great possibilities for accurate and sensitive Cd2+ detection based on the ratiometric strategy. [ABSTRACT FROM AUTHOR]

A new kind of internal reference probe was developed to construct a ratiometric electrochemical sensor for accurate and sensitive Cd2+ detection. AuPt nanoclusters (AuPt NCs) were synthesized and then evenly distributed on reduced graphene oxide (rGO) to form a nanocomposite (AuPt–rGO), which showed peroxidase-like activity and catalyzed the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP) in the presence of H2O2. It was found that DAP was further reduced on the electrode with a constant current intensity whether Cd2+ was added or not, which enabled it to function as an excellent internal reference probe. Thus, the ratio between the reduction currents of Cd2+ and DAP (iCd2+/iDAP) was proposed to monitor Cd2+ based on the ratiometric strategy. Additionally, the high surface area and good conductivity of AuPt–rGO endowed the sensor with enhanced sensitivity. A wide linear range and a low limit of detection were measured at 5.0 × 10−8–1.0 × 10−4 mol L−1 and 3.1 × 10−8 mol L−1, respectively. Compared with the single signal sensors, this ratiometric sensor presents more accuracy and reliability in the detection of Cd2+, facilitating the quantification of Cd2+ concentration in different water samples with good recoveries. The novel internal reference probe proposed here shows great possibilities for accurate and sensitive Cd2+ detection based on the ratiometric strategy. [ABSTRACT FROM AUTHOR]

Convenient and fast approaches for sensitive monitoring of different biomolecules are of vital importance for obtaining insights into biological processes and related diseases. Herein, silica nanospheres encapsulated with Ru-(bpy)32+ (RuSiO2) were uniformly coated with silver nanoparticles (AgNPs) through the in-situ reduction method to form RuSiO2@Ag core–shell nanoparticles, which were employed to fabricate a versatile electrochemiluminescence (ECL) sensing system for the assay of glucose (Glu) and adenosine triphosphate (ATP) on the basis of ECL resonance energy transfer (ECL-RET). RuSiO2@Ag core–shell nanoparticles showed high RET efficiency due to the combination of the donor (RuSiO2)–acceptor (AgNPs) pair into one nanostructure, causing a significantly quenched ECL signal of RuSiO2. Afterward, the Glu oxidase immobilized on RuSiO2@Ag by DNA complementation naturally catalyzed the oxidation of Glu to produce H2O2, which then triggered the etching of AgNPs. Consequently, the remarkably recovered ECL signal was further used to specifically detect Glu and achieved a limit of detection of 0.15 μM. ATP was chosen as a model molecule to verify the detecting ability of the sensor and achieved femtomolar-level results. The versatile ECL sensing system based on enzymatic oxydate-triggered etching and RET strategies hold potential promise for the convenient and sensitive detection of multiple types of biomolecules. [ABSTRACT FROM AUTHOR]