As one of the significant intracellular
signaling molecules, hydrogen
peroxide (H2O2) regulates some vital biological
processes. However, it remains a challenge to develop noninvasive
electrodes that can be used for sensing trace H2O2 at the cellular level. Here, we evaluated a high-performance solid-state
electrochemiluminescence (ECL) H2O2 sensor based
on MIL-88B(Fe) nanocrystal-anchored Ti microwires. Semiconducting
TiO2 nanotubes (TiNTs) vertically grown around a Ti wire via an anodization technique act as an intrinsic ECL luminophore.
By integrating with MIL-88B(Fe), the synergistic effect of the TiO2 luminophore and the remarkable peroxidase-like activity of
MIL-88B(Fe) enable the resulting H2O2 sensor
an ultrahigh sensitivity featuring a minimum detection limit of 0.1
nM (S/N = 3), long-term stability, high durativity, and wide-range
linear response to a concentration of up to 10 mM. To demonstrate
the concept of a MIL-88B(Fe)@TiO2 microelectrode for single-cell
sensing, the electrode was used to detect intracellular H2O2 in a single cell. Moreover, benefiting from the heterojunction
of MIL-88B(Fe)/TiO2, the microelectrode was found to exhibit
excellent photocatalytic activity in the visible-light range, that
is, the sensor surface can be self-cleaning after a short visible-light
treatment. These advanced sensor characteristics involving easy reusability
reveal that the MIL-88B(Fe)@TiO2 microelectrode is a new
platform for cytosensing. This study provides a new strategy to design
semiconductor materials with arbitrary shape and size, allowing for
profound applications in biomedical and clinical analysis.