2.1.2. Cu-MOF/GOD@HA

The above Cu-MOF/GOD nanoparticles (final concentration: 2 mg mL–1) mixed with HA (final concentration: 0.5 mg mL–1) under sonication for 30 min. Finally, the resultant Cu-MOF/GOD@HA was washed with DI water 3 times.

#### *2.2. Extracellular* ·*OH Generation under Catalysis by Cu-MOF*

#### 2.2.1. Reaction between Cu-MOF and GSH

Two hundred μL of Cu-MOF solution (1 mg mL–1) was mixed with 800 μL GSH solution (10 mmol L–1) under vortex mixing until the appearance of a white precipitate (Cu(I)-MOF). The precipitated intermediate products were characterized via UV-vis absorption spectroscopy (Hitachi, Hitachi, Japan).

#### 2.2.2. Extracellular ·OH Generation under Catalysis by Cu-MOF

A 5 μg mL–<sup>1</sup> methylene blue (MB) solution was mixed with 5 mmol L–<sup>1</sup> H2O2 and 200 μg mL–<sup>1</sup> Cu(I)-MOF or Cu-MOF under vortex mixing. After different time intervals of reaction, ·OH-induced MB degradation was evaluated based on the change in the absorption at the maximum absorption wavelength 630 nm.

#### 2.2.3. Gluconic Acid Generation under Catalysis by GOD

(1) A 100 μg mL–<sup>1</sup> Cu-MOF or Cu-MOF/GOD solution was mixed with 500 μg mL–<sup>1</sup> Glu under vortex mixing. After different times of reaction, the generation of gluconic acid was monitored by the acidity change of the solution. (2) A 100 μg mL–<sup>1</sup> Cu-MOF or Cu-MOF/GOD solution was mixed with different concentrations of Glu under vortex mixing for 24 h. The generation of gluconic acid was monitored by the acidity change of the solution.

#### 2.2.4. The H2O2 Generation under Catalysis by GOD

The fluorescence signals of Ampliflu Red are influenced by the change of H2O2 concentration. Thus, Ampliflu Red was used to investigate the H2O2 generation. Specific steps were as follows: (1) A 600 μg mL–<sup>1</sup> Ampliflu Red solution was mixed with 500 μg mL–<sup>1</sup> Glu and 100 μg mL–<sup>1</sup> Cu-MOF/GOD under vortex mixing. After different time intervals (0, 5, 10, 25, 50 min), the fluorescence intensity at -585 nm under 530 nm wavelength excitation was measured. (2) A 600 μg mL–<sup>1</sup> Ampliflu Red solution was mixed with 100 μg mL–<sup>1</sup> Cu-MOF/GOD and different concentrations of Glu (0, 20, 50, 70, 100 μg mL–1) under vortex mixing. After 30 min of reaction, the fluorescence intensity at ∼585 nm under 530 nm wavelength excitation was measured.
