AuNPs-COFs Core–Shell Reversible SERS Nanosensor for Monitoring Intracellular Redox Dynamics

Abstract

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.

Smart Nanoplatform for Visualizing Hydrogen Sulfide and Amplifying Oxidative Stress to Tumor Apoptosis

“…The introduction of a silver layer made the surface charge of Au transform from a negative to a positive potential due to the changes of the surfactant, while the coating of the COF layer and the loading of DOX enabled the surface of the nanoparticles still keep the positive potential, which were attributed to the positive charge of DOX and the residual amino of COFs. Furthermore, comparing the FTIR spectra of 4,4′-disulfanediyldibenzaldehyde (S–S–CHO) and 1,3,5-tris­(4-aminophenyl)­benzene (TAPB) in Figure G with that of S–S-COFs showed the peaks at 1628 cm –1 belonging to the stretching vibration of CN . Thus, the appearance of the peaks at approximately 1628 cm –1 in the FTIR spectrum of Au@M@Ag@COFs confirmed the successful formation of COFs which possessed a hexagonal structure as expected (Figure S5).…”

“…Moreover, the surface charge of the nanoparticles also had the corresponding changes (Figure S4). The introduction of a silver layer made the surface charge of Au transform from a negative to a positive potential due to the changes of the surfactant, while the coating of the COF layer and the loading 38 Thus, the appearance of the peaks at approximately 1628 cm −1 in the FTIR spectrum of Au@M@Ag@COFs confirmed the successful formation of COFs which possessed a hexagonal structure as expected (Figure S5). The layer-bylayer-assembled function of Au@M@Ag@COFs was further .…”

“…In addition, the dark-field image of Au@M@Ag@COFs after adding H 2 S became blue from green, and its scattering wavelength also showed a blue shift, as shown in Figure S6, which may be the transformation of Ag to Ag 2 S. , The TEM and EDS characterization results of the nanoplatform after reacting with H 2 S showed that the COF layer remained intact, while the surface of the silver layer displayed evident presence of the S element, which further proves the formation of Ag 2 S (Figure S7). Furthermore, the SERS spectra of Au@M@Ag@COFs-DOX both had no conspicuous change over 60 days, while that of Au@M@Ag had an obvious decrease in the same time interval (Figures S8 and S9), which can be attributed to the protective effect of the COF layer. , In addition, Au@M@Ag@COFs-DOX can remain stable under different pH conditions (Figure S10). Therefore, Au@M@Ag@COFs-DOX showed excellent stability.…”

“…Furthermore, the SERS spectra of Au@M@Ag@COFs-DOX both had no conspicuous change over 60 days, while that of Au@M@Ag had an obvious decrease in the same time interval (Figures S8 and S9), which can be attributed to the protective effect of the COF layer. 38,42 In addition, Au@M@ Ag@COFs-DOX can remain stable under different pH conditions (Figure S10). Therefore, Au@M@Ag@COFs-DOX showed excellent stability.…”

Efficient Electrochemical Microsensor for the Simultaneous Measurement of Hydrogen Peroxide and Ascorbic Acid in Living Brains

“…Up to now, various approaches have been proven to be effective for determination of H 2 O 2 or AA alone, including fluorescence and colorimetric sensing, − chemical and electrochemical luminescence, − surface-enhanced Raman scattering, − capillary electrophoresis, − electrochemical sensing and so on. − Thereinto, an electrochemical method has been successfully applied in in situ , real-time measurements in vivo due to its flexibility in miniaturization and advantage in simplicity and sensitivity. − Several elegant electrochemical microsensors were reported to be applicable in in vivo analysis of H 2 O 2 or AA alone. − Nevertheless, it is still a challenge to realize simultaneous determination of H 2 O 2 and AA in the brain, since H 2 O 2 and AA possess opposite redox properties. Normally, H 2 O 2 can be easily reduced on the electrode within a cathodic scan, while AA can be cushily oxidated through an anodic scan.…”