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A fluorescence quenching enhanced immunoassay has been developed to achieve ultrasensitive recognition of human epididymal 4 (HE4) modifying the fluorescence quencher. The carboxymethyl cellulose sodium-functionalized Nb2C MXene nanocomposite (CMC@MXene) was firstly introduced to quench the fluorescence signal of the luminophore Tb-Norfloxacin coordination polymer nanoparticles (Tb-NFX CPNPs). The Nb2C MXene nanocomposite as fluorescent nanoquencher inhibits the electron transfer between Tb and NFX to quench the fluorescent signal by coordinating the strongly electronegative carboxyl group on CMC with Tb (III) of Tb-NFX complex. Simultaneously, due to the superior photothermal conversion capability of CMC@MXene, the fluorescence signal has been further weakened by the photothermal effect driven non-radiative decay of the excited state under near-infrared laser irradiation. The constructed fluorescent biosensor based on CMC@MXene probe finally realized the enhanced fluorescence quenching effect, and achieved ultra-high sensitivity and selective detection of HE4, exhibiting a wide linear relationship with HE4 concentration on the logarithmic axis in the range of 10−5 to 10 ng/mL and a low detection limit of 3.3 fg/mL (S/N = 3). This work not only provides an enhanced fluorescent signal quenching method for the detection of HE4, but also provides novel insights for the design of fluorescent sensor toward different biomolecules. [ABSTRACT FROM AUTHOR]

A dual-readout immunosensor coupled with electrochemical impedance and temperature signal was successfully proposed to detect autoimmune hepatitis markers (ASGPR). Nb2C MXene with excellent conductivity, abundant surface functional groups, and extraordinary photothermal conversion efficiency, was designed to be a multifunctional biological probe, whose specific binding with antigen enhanced steric hindrance to generate electrochemical impedance signal, and at the same time, it had a strong optical response in the near-infrared band to achieve temperature output. In addition, poly(N-isopropyl acrylamide) (PNIPAM) was a temperature-sensitive polymer, which was adopted as the sensing matrix. When the multifunctional probe was specifically bound to the antigen, under 808-nm laser irradiation, the captured Nb2C MXene achieved photothermal conversion to increase the electrode surface temperature, and the conformation of PNIPAM changed from a free spiral to a spherical shape, further realizing double amplification of the EIS signal. Under the optimized experimental conditions, the impedance values and the temperature changes increased proportionally with the increase of the ASGPR concentration from 10−5 to 1 ng/mL, and the detection limit of the immunosensor was 3.3 × 10−6 ng/mL. The established dual-readout immunosensor exhibited good selectivity and acceptable stability and provided an effective detection method for autoimmune hepatitis marker detection. [ABSTRACT FROM AUTHOR]

Herein, a photothermal triggered multi-signal readout (MSR) system was innovatively established with great convenience for low-cost and sensitive point-of-care testing (POCT). In this sensing system, an intelligent multi-signal readout interface (MSRI) with multidimensional response-ability to thermal stimulus was developed and utilized as a sensing element. A bio-bar-code photothermal probe peptides@H 2 N-HCNTs acted as a target associated photothermal agent anchored on MSRI via competitive reaction. The multi-signal assay of target was realized under the driven of 808 nm laser, photo-to-thermal conversion effect of photothermal probe caused dramatically thermal energy increase on MSRI. As a result, the competitive recognition events were translated into several detectable signals on MSRI, including a local temperature elevation, a visual color change from blue to green as well as weight loss on MSRI, all of these signals were proportional to the target concentration. This assay has been successfully applied in field work for detecting zearalenone (ZEN), a common mycotoxin in grain food, with linear ranger from 10−7 ng/mL to 10−1 ng/mL and detection limits of 1.06 × 10−7 ng/mL. Combination of the different signal principles was expected to result in more reliable and precise results. Accordingly, this creatively designed MSR-system not only provided a platform for sensitive monitor of mycotoxin but also offered new method for reliable and affordable personal assays in daily life and low-resource setting. • A multi-signal readout system was proposed for sensitive point-of-care testing. • An interface with multidimensional response ability to thermal stimulus was utilized as a smart sensing element. • The bio-bar-code photothermal probe induced several detectable signal responses on MSRI. • The mutual calibration between different signals improved precision in positive judgments. • A common mycotoxins zearalenone was selected as a target analyte. [ABSTRACT FROM AUTHOR]

• AgI nanohybrids was proposed as a photothermal agent. • Signal amplification was achieved by photothermal effect. • A multifunctional probe was performed by the precise controlling of NIR laser. Herein, a photothermal in-situ amplified electrochemical immunoassay based on multifunctional probe for detecting autoimmune hepatitis marker was constructed. The immunoassay followed a sandwich protocol, helical carbon nanotubes (HCNTs) and polyaniline (PANI) composite provided a desirable substrate for the immobilization of massive primary antibody (Ab 1). Subsequently, the multifunctional probe, by utilizing Chitosan (CS) modified AgI nanohybrids (AgI NHs) labeled secondary antibody (Ab 2), were simply designed for the first time. To be specific, AgI NHs were not only directly served as signal readout, but also as amplifier further enhanced electrochemical signal. Under the near-infrared (NIR) laser irradiation, electrochemical reaction was significantly accelerated on electrode in situ due to the extraordinary photothermal conversion capability of AgI NHs. Therefore, the evidently improved sensitivity together with enhanced signal-to-noise ratio of immunoassay was achieved in the short time by precise-controlling of NIR laser irradiation. Under the optimal conditions, the developed electrochemical immunoassay realized sensitive and specific detection of autoimmune hepatitis marker from 10−4 ng/mL to 1 ng/mL with low detection limit of 3.3 × 10-5 ng/mL. Importantly, this work provided a promising prospect for the application of photothermal effect coupled with electrochemical immunoassay and opened up a new pathway for signal amplification. [ABSTRACT FROM AUTHOR]