Isopropanol

Total RNA extraction from HEI-OC1 cells was performed using TRIzol reagent (Invitrogen, Carlsbad, CA, USA). The cells were homogenized in 500 μL of TRIzol solution and incubated at room temperature for 5 min to dissolve cellular components. To separate the total RNA, 100 μL of chloroform (Sigma-Aldrich) was added to the mixture and centrifuged at 10,000 rpm for 15 min at 4 °C after a 5 min incubation at room temperature. The supernatant was transferred to a new 1.5 mL microfuge tube and 250 μL of isopropanol (Samchun Chemical Co., Ltd., Seoul, Republic of Korea) was added, which was followed by a 10 min incubation at room temperature to precipitate the RNA. The mixture was then centrifuged for 10 min at 10,000 rpm at 4 °C and the supernatant was discarded. The RNA pellet was purified by adding 500 μL of 75% ethanol; then, it was centrifuged for 5 min at 8000 rpm at 4 °C and the supernatant was discarded. The RNA pellet was dried for 5–10 min at 55 °C and resuspended in DEPC water (Invitrogen, Carlsbad, CA, USA). The quality and quantity of the total RNA were analyzed using NanoDrop 2000 (Thermo Fisher Scientific Inc., Ganseville, FL, USA), Qubit (Invitrogen, Carlsbad, CA, USA), and TapeStation (Agilent Technologies, Palo Alto, CA, USA).

Gold (III) chloride trihydrate (HAuCl₄∙3H₂O), cysteamine hydrochloride, NaBH₄, TBAH, TTIP (Ti[OCH(CH₃)₂]₄), cobalt (II) nitrate hexahydrate (Co(NO₃)₂∙6H₂O), potassium phosphate monobasic, and potassium phosphate dibasic trihydrate were purchased from Sigma-Aldrich (St. Louis, MO, USA). 2-Propanol and isopropanol were obtained from Samchun Pure Chemical Co., Ltd (Pyeongtaek-si, Republic of Korea). ITO-coated glasses (sheet resistance = 10 mΩ cm⁻², 10 mm× 37 mm × 0.7 mm Th) were purchased from Taewon Scientific Co., Ltd (Seoul, Republic of Korea).

DMEM (Dulbecco′s Modified Eagle′s Medium) and fetal bovine serum (FBS) were obtained from Hyclone (HyClone Laboratories Inc., Logan, UT, USA). Antibiotic-Antimycotic was purchased from Gibco (Grand Island, NY, USA). HPLC standard compounds (chlorogenic acid and (−)-epicatechin), 3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and dimethyl sulfate (DMSO) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Organic solvents (chloroform, isopropanol, methanol, and ethanol) were purchased from Samchun Chemical (Seoul, Korea) and Daejung Chemical & Metal (Siheung, Korea). Inorganic salts were purchased from Sigma-Aldrich. Silica gel was purchased from Merck (Kenilworth, NJ, USA).

Chemicals: AgNO₃ (ACS, 99.9 + %, metal basis), oleic acid (OA; tech., 90%), and (3-mercaptopropyl)trimethoxysilane (MPTS, 95%) were purchased from Alfa Aesar. Oleylamine (OAm; 70%) was purchased from Sigma-Aldrich. Ammonium bromide (NH₄Br; ACS reagent,  > 99.0%) was purchased from Honeywell Fluka. Toluene (99.5%), ethanol (95.0%), and isopropanol (IPA; 99.5%) were purchased from Samchun. PET films with thicknesses of 50–250 μm (SKC) were used as the flexible substrate.

Ethylenediamine (>99.5%), ethanethiol (>97%), and glycerol (>99.5%) were purchased from Aldrich Chemical Co. Powders of Cu (99.9%) for high-energy ball milling, Se (99.999%) for the synthesis of Se polyanion were purchased from Alfa Aesar. Powder of Se (99.999%) for high-energy ball milling was purchased from 5 N Plus. Isopropanol was purchased from Samchun Chemicals. The chemicals and elements were used without purification.