Dopamine

The PEGDA-PEDOT OECT response was evaluated by acquiring transfer characteristics in presence of different concentrations of dopamine (MW = 189.54 mg/mol, Alfa Aeser) in 100 mM PBS solution. All the electrical measurements were performed by varying the gate voltage from − 0.2 to 1 V at fixed V_ds = − 0.6 V, with a scan rate of 10 mV/s. The PDMS well was filled with 150 μL of PBS/DA solutions with dopamine diluted at concentrations ranging from 100 nM to 5 mM. A vertical Pt wire gate (0.6 mm diameter, FRANCO CORRADI) was used as the gate electrode. Each measurement was repeated three times and the channel was washed with H₂O Milli-Q and PBS solution after each measurement step. ΔV_gs was calculated by merging transfer curves at different concentrations (three runs per device for each DA concentration, repeated using three different devices) upon shifting them along the V_gs axis in order to define a universal curve⁴⁹ . Error bars have been calculated as the statistical error of the mean (σ_dev/N − 1, where σ_dev are the standard deviations and N is the number of measured devices).
The device LoD against DA sensing was assessed by estimating the intersection between the slope of the linear fit in the dynamic window (sensor transfer curve) and the ideal baseline for concentrations falling below such window. Sensitivity was calculated as the slope of the sensor transfer curve.

TEOS, HAuCl₄, and Fe(acac)₃ were purchased from Energy Chemical; Dopamine purchased from Alfa Aesar; ammonia solution (25–28 %), ethanol, sodium citrate, polyvinylpyrrolidone (PVP), ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol, AgNO₃, and NaCl were purchased from Sinopharm Chemical Reagent Co. (Shanghai, China). All the reagents were used without further purification. Deionized water was used throughout the experiments.

The experiment used commercial allogeneic bone (Bio Gene, Datsing, Beijing, China). All bones were cleaned with deionized water before being submerged in dopamine solution (2 mg/ml in 10 mM TrisHCL, pH 8.5) (dopamine, Alfa Aesar, Ward Hill, United States; TrisHCL, Beyotime, Shanghai, China) for 20 s. The scaffolds were then cleaned three times with deionized water. After 3 days in 75% anhydrous ethanol, the allogeneic bone was soaked in phosphate-buffered saline (PBS, Aladdin, Shanghai, China) for 2 days. Before usage, the bones were washed three times in PBS. Direct soak was used to graft VEGF proteins (Sigma-Aldrich, St. Louis, MO, United States) onto the surface of P@Bone. To make the VP@Bone scaffolds, the P@Bone scaffolds were soaked in a VEGF solution (200 ng/ml in deionized water) under sterile conditions and shaken overnight at 4°C. The scaffolds were then cleaned three times with deionized water.
In the following sections, allogeneic bones without any coating or biomolecules are denoted the “Bone” group; Human Umbilical Vein Endothelial Cells (HUVECs) cultivated with allogeneic bones covered with PDA coating are denoted the “HP@Bone” group; HUVECs cultivated with allogeneic bones with VEGF thought the PDA coating are denoted the “HVP@Bone” group.

The β-Galactosidase assay was carried out in triplicate; overnight cultures were diluted with N medium and grown for 4 h, and the activity was determined as described previously (55 ). Mg²⁺ was added to 0.01 mM (namely, low Mg²⁺), and 10 mM (high Mg²⁺). Complementation was carried out by using complementing plasmid pemrR-FLAG, and heterologous expression of emrR from this plasmid was induced by adding 0.2 mM IPTG or indicated specifically. When needed, salicylate (Sigma-Aldrich) or dopamine (Alfa Aesar, Thermo Fisher Scientific) was added to the required concentrations. Data correspond to three independent assays conducted in duplicate, and all values were means ± standard deviations.