A composite (N-rGO@ppy) of N-doped reduced graphene oxide (N-rGO) coated with polypyrrole (ppy) particles was successfully synthesized. The incorporation of N-rGO significantly mitigates the aggregation of ppy synthesized in situ, and the doped N atoms improve the conductivity of graphene oxide (GO), thereby enhancing N-rGO@ppy’s redox properties. Firstly, a glassy carbon electrode (GCE) modified with N-rGO@ppy (N-rGO@ppy/GCE) was used in combination with a bismuth film and square-wave anodic stripping voltammetry (SWASV) for the simultaneous trace analysis of Pb²⁺ and Cd²⁺. N-rGO@ppy/GCE exhibited distinct stripping peaks for Pb²⁺ and Cd²⁺, with a linear range of 1 to 500 μg L⁻¹. The limits of detection (LODs) were found to be 0.080 μg L⁻¹ for Pb²⁺ and 0.029 μg L⁻¹ for Cd²⁺, both of which are significantly below the standards set by the World Health Organization (WHO). Subsequently, the same electrochemical sensing strategy was adapted to a more portable screen-printed electrode (SPE) to accommodate the demand for in situ detection. The performance of N-rGO@ppy/SPE for analyzing Pb²⁺ and Cd²⁺ in actual samples, such as drinking water, milk, and honey, showed results consistent with those obtained from conventional graphite furnace atomic absorption spectrometry (GFAAS).

Reducing Ca²⁺ content in the sarcoplasmic reticulum (SR) through ryanodine receptors (RyRs) by calcin is a potential intervention strategy for the SR Ca²⁺ overload triggered by β-adrenergic stress in acute heart diseases. OpiCal-PEG-PLGA nanomicelles were prepared by thin film dispersion, of which the antagonistic effects were observed using an acute heart failure model induced by epinephrine and caffeine in mice. In addition, cardiac targeting, self-stability as well as biotoxicity were determined. The synthesized OpiCa1-PEG-PLGA nanomicelles were elliptical with a particle size of 72.26 nm, a PDI value of 0.3, and a molecular weight of 10.39 kDa. The nanomicelles showed a significant antagonistic effect with 100 % survival rate to the death induced by epinephrine and caffeine, which was supported by echocardiography with significantly recovered heart rate, ejection fraction and left ventricular fractional shortening rate. The FITC labeled nanomicelles had a strong membrance penetrating capacity within 2 h and cardiac targeting within 12 h that was further confirmed by immunohistochemistry with a self-prepared OpiCa1 polyclonal antibody. Meanwhile, the nanomicelles can keep better stability and dispersibility in vitro at 4 °C rather than 20 °C or 37 °C, while maintain a low but stable plasma OpiCa1 concentration in vivo within 72 h. Finally, no obvious biotoxicities were observed by CCK-8, flow cytometry, H&E staining and blood biochemical examinations. Our study also provide a novel nanodelivery pathway for targeting RyRs and antagonizing the SR Ca²⁺ disordered heart diseases by actively releasing SR Ca²⁺ through RyRs with calcin.