In this work, a nonenzymatic electrochemical sensor based on nanoporous magnesium oxide (MgO) was developed for the rapid screening of hydrogen peroxide (H₂O₂) in milk.

Fluorescent nanoparticles (NPs) have been increasingly studied as contrast agents for better understanding of biological processes at the cellular and molecular level. However, their use as bioimaging tools is strongly dependent on their optical emission as well as their biocompatibility. This work reports the fabrication and characterization of silk fibroin (SF) coated magnesium oxide (MgO) nanospheres, containing oxygen, Cr³⁺ and V²⁺ related optical defects, as a nontoxic and biodegradable hybrid platform for bioimaging applications. The MgO-SF spheres demonstrated enhanced emission efficiency compared to noncoated MgO NPs. Furthermore, SF sphere coating was found to overcome agglomeration limitations of the MgO NPs. The hybrid nanospheres were investigated as an in vitro bioimaging tool by recording their cellular uptake, trajectories, and mobility in human skin keratinocytes cells (HaCaT), human glioma cells (U87MG) and breast cancer cells (MCF7). Enhanced cellular uptake and improved intracellular mobilities of MgO-SF spheres compared to MgO NPs was demonstrated in three different cell lines. Validated infrared and bright emission of MgO-SF NP indicate their prospects for in vivo imaging. The results identify the potential of the hybrid MgO-SF nanospheres for bioimaging. This study may also open new avenues to optimize drug delivery through biodegradable silk and provide noninvasive functional imaging feedback on the therapeutic processes through fluorescent MgO.

Metal nanoparticle assisted photoelectrochemical (PEC) biosensing has attracted attention for point-of-care testing due to its fast and low background noise signal. However the interfacial charge transfer of plasmonic-enhanced biosensing is not yet fully understood. Herein, a plasmonic-enhanced PEC platform has been demonstrated for glutathione (GSH) detection based on a hybrid structure of a well-oriented zinc oxide nanorod array (ZnO NR) with gold nanoparticles (Au NPs) as photoanode. In the PEC system, the self-powered bioanalysis is carried out at 0 V versus Ag/AgCl under simulated sunlight. In detail, the optical experiments (e.g. photoluminescence, PL) and theoretical analysis (e.g. finite-difference time-domain, FDTD) illustrate the photoresponse enhancement mechanism of the Au NPs–ZnO NRs and reaction process of GSH. The GSH oxidization and the effect of pH on the photocurrent response are demonstrated and investigated. The as-prepared surface plasmon resonance (SPR) based PEC sensor could be considered for GSH detection for early diagnosis of tumors.