Shandong University of Technology

A rapidly growing field is piezoresistive sensor for accurate respiration rate monitoring to suppress the worldwide respiratory illness. However, a large neglected issue is the sensing durability and accuracy without interference since the expiratory pressure always coupled with external humidity and temperature variations, as well as mechanical motion artifacts. Herein, a robust and biodegradable piezoresistive sensor is reported that consists of heterogeneous MXene/cellulose-gelation sensing layer and Ag-based interdigital electrode, featuring customizable cylindrical interface arrangement and compact hierarchical laminated architecture for collectively regulating the piezoresistive response and mechanical robustness, thereby realizing the long-term breath-induced pressure detection. Notably, molecular dynamics simulations reveal the frequent angle inversion and reorientation of MXene/cellulose in vacuum filtration, driven by shear forces and interfacial interactions, which facilitate the establishment of hydrogen bonds and optimize the architecture design in sensing layer. The resultant sensor delivers unprecedented collection features of superior stability for off-axis deformation (0–120°, ~ 2.8 × 10–3 A) and sensing accuracy without crosstalk (humidity 50%–100% and temperature 30–80 °C). Besides, the sensor-embedded mask together with machine learning models is achieved to train and classify the respiration status for volunteers with different ages (average prediction accuracy ~ 90%). It is envisioned that the customizable architecture design and sensor paradigm will shed light on the advanced stability of sustainable electronics and pave the way for the commercial application in respiratory monitory.

Herein, an enzyme-free and highly efficient sandwich-type electrochemical immunosensor for cTnI detection was developed using covalent organic framework (COF) confined Co₃O₄ nanoparticles (NPs) as the signal probe and enhancing the sensitivity with electrochemical-chemical-chemical (ECC) redox cycle amplification (RCA) strategy. The multifunctional COF, with high surface area and rich nitrogen, serves not only as a substrate material but also as a scaffold for Co²⁺ entrapment, enabling the confined growth and uniform distribution of ultrafine Co₃O₄ NPs as signal amplification platform, thereby providing abundant catalytic active sites for ECC redox cycling reactions. COF confined Co₃O₄ NPs with variable valence states (Co³⁺/Co²⁺) serve as a redox-active electrode material that can enhance the current signal substantially. The ECC redox cycle is triggered by the redox reaction between Co³⁺ at the electrode and electroactive hydroquinone (HQ), while HQ was regenerated by the reducing agent tris (2-carboxyethyl) phosphine (TCEP), resulting in a significant amplification of the current signal for cTnI analysis. The constructed immunosensor exhibited excellent performance with a wide linear range from 1 fg mL^-1 to 100 ng mL^-1, and a low detection limit of 0.88 fg mL^-1. Furthermore, the immunosensor successfully applied to detected cTnI in human serum, proving its clinical potential.

Carcinoembryonic antigen (CEA), a clinically critical tumor biomarker, enables early cancer screening and diagnosis. Here, we describe a sandwich-structured electrochemical immunosensing platform enabling supersensitive CEA quantification, leveraging synergistic signal amplification by sea urchin-like PdAg nanostructures and Au NPs/N-C@CNTs substrates. The urchin-like morphology of PdAg endows the material additional catalytic active sites for hydrogen peroxide reduction, which has remarkable electrochemical performance. Moreover, PdAg with superior biocompatibility can effectively immobilize the secondary antibody. Polydopamine-coated carbon nanotubes are carbonized to yield nitrogen-doped carbon nanotubes (N-C@CNTs), which are bound to gold nanoparticles (Au NPs) via stable AuN bonds, thereby facilitating the subsequent binding of primary antibodies to the Au NPs. Optimized assays demonstrated a broad dynamic range (50 fg mL^-1-100 ng mL^-1) with low detection limits (1.04 fg mL^-1, S/N = 3), coupled with exceptional reproducibility, selectivity, and stability. This platform holds significant promise for the screening of early-stage tumor biomarkers.