The redox homeostasis in living cells is greatly crucial for maintaining the redox biological function, whereas accurate and dynamic detection of intracellular redox states still remains challenging. Herein, a reversible surface-enhanced Raman scattering (SERS) nanosensor based on covalent organic frameworks (COFs) was prepared to dynamically monitor the redox processes in living cells. The nanosensor was fabricated by modifying the redox-responsive Raman reporter molecule, 2-Mercaptobenzoquione (2-MBQ), on the surface of gold nanoparticles (AuNPs), followed by the in situ coating of COFs shell. 2-MBQ molecules can repeatedly and quickly undergo reduction and oxidation when successively treated with ascorbic acid (AA) and hypochlorite (ClO–) (as models of reductive and oxidative species, respectively), which resulted in the reciprocating changes of SERS spectra at 900 cm–1. The construction of the COFs shell provided the nanosensor with great stability and anti-interference capability, thus reliably visualizing the dynamics of intracellular redox species like AA and ClO– by SERS nanosensor. Taken together, the proposed SERS strategy opens up the prospects to investigate the signal transduction pathways and pathological processes related with redox dynamics.

ATP and reactive oxygen species (ROS) are considered significant indicators of cell apoptosis. However, visualizing the interplay between apoptosis-related ATP and ROS is challenging. Herein, we developed a metal–organic framework (MOF)-based nanoprobe for an apoptosis assay using duplex imaging of cellular ATP and ROS. The nanoprobe was fabricated through controlled encapsulation of gold nanorods with a thin zirconium-based MOF layer, followed by modification of the ROS-responsive molecules 2-mercaptohydroquinone and 6-carboxyfluorescein-labeled ATP aptamer. The nanoprobe enables ATP and ROS visualization via fluorescence and surface-enhanced Raman spectroscopy, respectively, avoiding the mutual interference that often occurs in single-mode methods. Moreover, the dual-modal assay effectively showed dynamic imaging of ATP and ROS in cancer cells treated with various drugs, revealing their apoptosis-related pathways and interactions that differ from those under normal conditions. This study provides a method for studying the relationship between energy metabolism and redox homeostasis in cell apoptosis processes.

Herein, a fluorescence and surface-enhanced Raman spectroscopy dualmode system was designed for cholesterol detection based on self-assembled plasmonic nanojunctions mediated by the competition of rhodamine 6G (R6G) and cholesterol with β-cyclodextrin modified on gold nanoparticles (HS-β-CD@Au). The fluorescence of R6G was quenched by HS-β-CD@Au due to the fluorescence resonance energy transfer effect. When cholesterol was introduced as the competitive guest, R6G in the cavities of HS-β-CD@Au was displaced to recover its fluorescence. Moreover, two of HS-β-CD@Au can be linked by one cholesterol to form a more stable 2:1 complex, and then, plasmonic nanojunctions were generated, which resulted in the increasing SERS signal of R6G. In addition, fluorescence and SERS intensity of R6G increased linearly with the increase in the cholesterol concentrations with the limits of detection of 95 and 74 nM, respectively. Furthermore, the dual-mode strategy can realize the reliable and sensitive detection of cholesterol in the serum with good accuracy, and two sets of data can mutually validate each other, which demonstrated great application prospects in the surveillance of diseases related with cholesterol.

Photoactive nanowires play an important role on the photoelectric-related applications; however, the in situ large-scale growth of photoactive nanowires on the arbitrary substrate still faces a great challenge. Herein, for the first time, we develop a facile coordination-induced self-assembly strategy for preparing the nanowires with high photoactivity through keeping a high concentration of Sc(NO 3 ) 3 and tartaric acid (TA) aqueous solution at room temperature. Surprisingly, the nanowires can grow directionally along the direction of water flow on any substrate due to the growth mechanism driven by water molecules, showing that the proposed nanowires are morphoplastic depending on the direction of liquid flow. The formation of nanowires has been proved to be attributed to the synergistic effect of water molecule-involved hydrogen bonding between hydroxyl groups of TA ligands as well as the multicoordination of Sc 3+ ions. Meanwhile, the prepared nanowires are highly photoactive, showing a strong photooxidation ability toward rhodamine 6G dyes, with a degradation efficiency of about 95.8% within 40 min. This finding introduces a coordination growth mechanism of nanowires, which not only provides a great possibility for large-scale and low-cost synthesis of photoactive nanowires with morphoplastic features but also shows a good application prospect in water cleaning by the photocatalysis technique.