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Developing a highly sensitive immunoassay for tumor biomarkers is particularly important in bioanalysis and early disease diagnosis. In this work, a simple one-pot solvothermal method was developed for controllable synthesis of well-dispersed PtCo alloyed nanodendrites (PtCo NDs) by using l -carnosine as the co-structure-directing agent. The PtCo NDs had a large specific surface area and provided abundant active sites available for electrocatalytic oxygen reduction reaction (ORR). Based on the highly enhanced currents of the ORR, a novel label-free electrochemical immunosensor was fabricated for highly sensitive assay of carbohydrate antigen 15–3 (CA15-3). The sensor showed a wide linear range of 0.1–200 U mL−1 and a low limit of detection (LOD) down to 0.0114 U mL−1 (S/N = 3), in turn exploring its application to diluted human serum samples with satisfactory results. This study provides a feasible platform for monitoring other tumor markers in clinical diagnosis.

Procalcitonin (PCT) is a sensitive and specific biomarker for sepsis diagnosis. In this study, a novel ratio-typed electrochemical immunosensor was constructed for reliable and sensitive assay of PCT based on hierarchical PtCoIr nanowires/polyethylene polyamine-grafted-ferrocene (PtCoIr HNWs/PEPA-Fc) and porous SiO

For immobilization and signal amplification of the probes, it is feasible and promising by using porous nanomaterials as nanocarriers. Herein, a novel label-free electrochemical immmunosensor was efficiently designed for ultrasensitive detection of procalcitonin (PCT). The immunosensor was prepared by using porous silica-coated gold nanorods (Au NRs@m-SiO2) to load electroactive dye thionine (Thi) on the electrode surface. Apart from the improved electrical conductivity, the porous feature highly increased the loading amount of Thi to boost the detection signals, while the good biocompatibility and protective microenvironment are beneficial to the largely improved stability for the target. For quantification of PCT, the developed immunosensor exhibited a good linear relationship in the antigen concentration range of 0.001–100 ng mL−1 with an ultra-low limit of detection (LOD, 0.39 pg mL−1, S/N = 3). Moreover, the built platform was successfully applied to such assay in human serum samples. The research provides some valuable guidelines for clinical screening and diagnosis of other biomarkers.

For early diagnosis and prevention of acute myocardial infarction (AMI), accurate and sensitive analysis of cardiac biomarkers by a single test has faced substantial challenge. A novel electrochemical immuno-sensing platform was built for untrasensitive assay of heart-type fatty acid-binding protein (h-FABP) via multi-signal output. This immunosensor utilized Au nanodendrites/chitosan-grafted-ferrocene (Au NDs/Chit-g-Fc) as the substrate and thionine-absorbed AuPt nanocrystals/polydopamine/open-pored hollow carbon spheres (Thi/AuPt/PDA/OHCSs) as the label material, producing two independent electrochemical signals from the Fc and Thi probes, respectively. For such assay of the target h-FABP in the immuno-sensing system, the ratios (IThi / IFc) between the double signals showed a broad dynamic range of 0.001–200.0 ng mL−1 and a low detection limit of 0.53 pg mL−1 (S/N = 3). This ratiometric sensor exerts a far-reaching influence on other biomarkers researches in practical applications.

Procalcitonin (PCT) is a sensitive and specific biomarker for sepsis diagnosis. In this study, a novel ratio-typed electrochemical immunosensor was constructed for reliable and sensitive assay of PCT based on hierarchical PtCoIr nanowires/polyethylene polyamine-grafted-ferrocene (PtCoIr HNWs/PEPA-Fc) and porous SiO2@Ag nanoparticles-toluidine blue (porous SiO2@Ag NPs-TB). Importantly, the PtCoIr HNWs/PEPA-Fc was first modified on the sensing interface, which harvested stable and strong electrochemical signals for readout of Fc due to the enriched anchoring sites created by the PtCoIr HNWs. Meanwhile, porous SiO2@Ag NPs-TB behaved as the label to conjugate with secondary antibody (Ab2), which also provided another strong detection signals originated from TB confined in such porous structures. The resulting immunosensor displayed a measurable output of procalcitonin (PCT) in the dynamic scope of 0.001 ~ 100 ng mL−1 with a low limit of detection (LOD) of 0.46 pg mL−1 (S/N = 3). Moreover, we exploited this strategy for PCT assay in a diluted human serum sample with acceptable results, exhibiting promising applications in the clinical analysis.

Severe challenges are still remained for development of highly sensitive, selective and stable photoelectrochemical (PEC) sensing technology, albeit with its broad application for chloramphenicol (CAP) detection. Herein, a novel “signal-on” PEC aptasensor was fabricated based on a 3D self-supporting Z-scheme AgI/Ag/BiOI heterojunction arrays subtly integrated with in-situ formed biocatalytic precipitation (BCP) for highly sensitive and selective determination of CAP. Impressively, the HRP modified CAP aptamer (HRP-CAP aptamer) was released from the electrode by its strong affinity to the introduced CAP, and gradually terminated the BCP reaction, in turn recovering the photocurrent. By virtues of the 3D self-supporting AgI/Ag/BiOI Z-scheme heterojunction arrays and BCP signal amplification strategy, the resultant PEC sensor exhibited a wide linear range of 2–250 nM with a limit of detection (LOD) as low as 0.226 nM (S/N = 3). This work opens a new avenue for design of PEC aptasensing strategy and exhibits the marvelous potential in bioanalysis of environmental samples.

Breast cancer, one of common malignant tumors, is threatening woman's health and life with high mortality rate to this day, and thereby its early screening and detection are of significance in medical diagnosis and follow-up treatment. In view of the low sensitivity, cost-effectiveness and invasive procedures, conventional approaches generally exhibit limited applications in practice. Such oncologic diseases have close correlation with the tumor markers usually situated in tumor cells or secreted by tumor cells. The biomarkers can work as good indicators for developing highly sensitive and specific immmunoassays towards detecting breast cancer. This work provides an overview of recent researches to screen and detect the benchmarked biomarkers of breast cancer, and discuss the developed immunosensing strategies on selected works published early in the past five years. Particular emphasis is focused on remarkable amplification approaches of detection signals to improve the sensitivity. Concretely, the paper introduces the design, fabrication, and applications of such sensors mainly by electrochemistry, electrochemiluminescence, and photoelectrochemistry, coupled with improved stability and selectivity. For developing such high-efficiency biosensors, recent challenges and opportunities are finally discussed towards early diagnosis of breast cancer.