*2.1. Materials*

Titanium plates (bare Ti of grade 2, Titanart, Incheon, Korea) served as EPD substrates. The plates were polished with 800- and 1200-grit silicon carbide paper and ultrasonically cleaned in acetone, ethanol (Duksan, Ansan, Korea), and distilled water (5 min for each bath). Single-layer GO was from Graphene Supermarket (Ronkonkoma, NY, USA). Ethanol (Duksan, Ansan, Korea) was 99.6% pure. Green fluorescence protein (GFP) and bone morphogenic protein-2 (BMP-2) were supplied by Genoss, Gyeonggi-do, Korea.

#### *2.2. Electrophoretic GO Deposition*

A GO suspension (500 μg/mL) was prepared in 80% (*v*/*v*) ethanol and sonicated for 15 min. Ti plates were submerged in the suspension at 1 cm from the cathode, and EPD proceeded at 10 mA for 1 min. The plates were then dried and stored in a desiccator. Prior to biological tests, the coated plates were sterilized with 70% (*v*/*v*) ethanol. EPD was also used to prepare drug-eluting coatings; the test BMs were GFP and BMP-2. Various amounts of the BMs (10, 25, 50, and 100 μg/mL) were added to GO suspensions or GO-coated Ti plates, magnetically stirred for 3 h, and EPD was performed or drug release was assessed.
