Au Nanoparticle/CoFc/Metal–Organic Framework as Enzyme-Free Dual-Signal Ratiometric Electrochemical Sensor for In-Situ Determination of Cell-Secreted H2O2

In-situ determination of cell-secreted biomolecules is important for elucidating its regulation of signal transduction pathways, but detecting these low-level endogenous biomolecules is difficult. Herein, using H2O2 as the detection object, we developed an ultrasensitive enzyme-free ratiometric electrochemical sensing platform in a simple and low-cost method for in-situ determination of cell-secreted H2O2, in which ferrocene (Fc) acts as an internal reference probe and nanoflower Au-Co-MOF acts a detection probe. First, flower-like CoFc-MOF was synthesized in situ on flexible carbon cloth (CC) by a one-step hydrothermal method, and then Au-CoFc-MOF/CC was obtained by electrodeposition of gold nanoparticles. The electrochemical measurement results show that the presence of H2O2 increases the reduction peak signal of Co-MOF (−0.32 V), while that of Fc (+0.4 V) is almost unchanged. By taking full advantage of the obviously separated reduction potential of Fc and Co-MOF, the well-designed sensing platform can reflect the concentration of H2O2 based on the IH2O2 – Iblank/IFc value in the 0.5 μM–10 mM range, with a detection limit as low as 32 nM, which is ∼15.6 times lower than the value obtained from the single signal method. In addition, the sensing platform also demonstrates excellent selectivity, reproducibility, stability, and biocompatibility. More significantly, this ratiometric electrochemical sensing platform based on flexible substrate shows great application potential in the in-situ determination of cell-secreted H2O2, which provides a feasible strategy for detecting other active substances released from living cells in clinical diagnosis.