Potassium superoxide

MCF-7 was bought from Cell bank of the representative culture preservation committee of the Chinese Academy of Sciences, China. Manganese sulfate (MnSO₄), potassium phosphate tribasic (K₃PO₄) and Nafion were purchased from East Sichuan Chemical Industry (Group) Co., Ltd. (Chongqing, China) and used as received. Graphene was obtained from Sinocarbon Materials Technology Co., Ltd., China. Zymosan A (Zym, from Saccharomyces cerevisiae) SOD, DNA (low molecular weight extracted from salmon sperm), and potassium superoxide were purchased from Sigma-Aldrich and used without further purification. The O₂˙⁻ solutions were prepared by dissolving KO₂ in PBS solution (pH 7.0, N₂ saturated). The concentration of O₂˙⁻ was determined by the reduction of ferri cytochrome c spectrophotometrically.^{21 (link)} All the other solutions were prepared using deionized water (18 MΩ cm) and were degassed with high purity nitrogen before experiments. All electrochemical experiments were carried out at room temperature.

N-Methyl-4-piperidone, Benzaldehyde, Diisopropylamine, n-Butyllithium (2.5 M solution in hexanes), 4-(Dimethylamino)pyridine (DMAP), and Sodium bicarbonate were purchased from Merck. Acetic acid, Dichloromethane, Tetrahydrofuran, Ethanol, Ethyl acetate, Citric acid, Sodium Sulfate(VI), and Acetic anhydride were purchased from POCH, Gliwice, Poland. Vanilin was purchased from Acros, Waltham, Massachusetts, USA. Dimethyl-sulfoxide (DMSO), Potassium superoxide, 18-crown-6-ether, Nitro blue tetrazolium chloride (NBT), Curcumin, Fetal bovine serum (FBS), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), recombinant PTP1B phosphatase, para-nitrophenyl phosphate (pNPP), and 2′,7′-dichlorofluorescein were purchased from Sigma-Aldrich, Saint Louis, Missouri, USA. Dulbecco’s Modified Eagle’s Medium (DMEM) and Phosphate-buffered saline (PBS) were purchased from PAN-biotech, Aidenbach, Germany. Lastly, 4–20% MP TGX Tain-Free Gel 10W was purchased from Bio-Rad Laboratories, Hercules, CA, USA and PTP1B antibodies were purchased from Cell Signaling, Danvers, MA, USA.