|  Mello L D, Hernandez S, Marrazza G, et al. Investigations of the antioxidant properties of plant extracts using a DNA-electrochemical biosensor[J]. Biosensors and Bioelectronics, 2006, 21(7): 1374-1382. Valko M, Izakovic M, Mazur M, et al. Role of oxygen radicals in DNA damage and cancer incidence[J]. Molecular and Cellular Biochemistry, 2004, 266(1/2): 37-56. King P, Anderson V, Edwards J, et al. A stable solid that generates hydroxyl radical upon dissolution in aqueous solutions: Reaction with proteins and nucleic acid[J]. Journal of the American Chemical Society, 1992, 114(13): 5430-5432. Cadet J, Delatour T, Douki T, et al. Hydroxyl radicals and DNA base damage[J]. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 1999, 424(1): 9-21. Bandyopadhyay U, Das D, Banerjee R K. Reactive oxygen species: Oxidative damage and pathogenesis[J]. Current Science, 1999, 77(5): 658-666. Raha S, Robinson B H. Mitochondria, oxygen free radicals, disease and ageing[J]. Trends in Biochemical Sciences, 2000, 25(10): 502-508. Loeb L A, Wallace D C, Martin G M. The mitochondrial theory of aging and its relationship to reactive oxygen species damage and somatic mtDNA mutations[J]. Proceedings of the National Academy of Sciences of the United States of America, 2005, 102(52): 18769-18770. Newton G L, Milligan J R. Fluorescence detection of hydroxyl radicals[J]. Radiation Physics and Chemistry, 2006, 75(4): 473-478. Pou S, Ramos C L, Gladwell T, et al. A kinetic approach to the selection of a sensitive spin trapping system for the detection of hydroxyl radical[J]. Analytical Biochemistry, 1994, 217(1): 76-83. Pritsos C A, Constantinides P P, Tritton T R, et al. Use of high-performance liquid chromatography to detect hydroxyl and superoxide radicals generated from mitomycin C[J]. Analytical Biochemistry, 1985, 150(2): 294-299. Yu J, Ge L, Huang J, et al. Microfluidic paper-based chemiluminescence biosensor for simultaneous determination of glucose and uric acid[J]. Lab on A Chip, 2011, 11(7): 1286-1291. Liu Y, Hu N. Electrochemical detection of natural DNA damage induced by ferritin/ascobic acid/H2O2 system and amplification of DNA damage by endonuclease Fpg[J]. Biosensors and Bioelectronics, 2009, 25(1): 185-190. Labuda J, Bu?ková M, Heilerova L, et al. Detection of antioxidative activity of plant extracts at the DNA-modified screen-printed electrode[J]. Sensors, 2002, 2(1): 1-10. Huang J, Li T, Chen Z, et al. Rapid electrochemical detection of DNA damage and repair with epigallocatechin gallate, chlorogenic acid and ascorbic acid[J]. Electrochemistry Communications, 2008, 10(8): 1198-1200. Zu Y, Liu H, Zhang Y, et al. Electrochemical detection of in situ DNA damage with layer-by-layer films containing DNA and glucose oxidase and protection effect of catalase layers against DNA damage[J]. Electrochimica Acta, 2009, 54(10): 2706-2712. Wu L, Yang Y, Zhang H, et al. Sensitive electrochemical detection of hydroxyl radical with biobarcode amplification[J]. Analytica Chimica Acta, 2012, 756: 1-6. Wang Y, Yin X, Shi M, et al. Probing chiral amino acids at sub-picomolar level based on bovine serum albumin enantioselective ?lms coupled with silver-enhanced gold nanoparticles[J]. Talanta, 2006, 69(5): 1240-1245. Chen Z, Peng Z, Luo Y, et al. Successively ampli?ed electrochemical immunoassay based on biocatalytic deposition of silver nanoparticles and silver enhancement[J]. Biosensors and Bioelectronics, 2007, 23(4): 485-491. Lin L, Liu Y, Tang L, et al. Electrochemical DNA sensor by the assembly of graphene and DNA-conjugated gold nanoparticles with silver enhancement strategy[J]. Analyst, 2011, 136(22): 4732-4737. Deng C, Chen J, Nie Z, et al. Impedimetric aptasensor with femtomolar sensitivity based on the enlargement of surface-charged gold nanoparticles[J]. Analytical Chemistry, 2008, 81(2): 739-745. Huang W T, Xie W Y, Shi Y, et al. A simple and facile strategy based on Fenton-induced DNA cleavage for fluorescent turn-on detection of hydroxyl radicals and Fe2+[J]. Journal of Materials Chemistry, 2011, 22(4): 1477-1481. Huang Y, Wang T H, Jiang J H, et al. Prostate specific antigen detection using microgapped electrode array immunosensor with enzymatic silver deposition[J]. Clinical chemistry, 2009, 55(5): 964-971. Huang C C, Chiu S H, Huang Y F, et al. Aptamer-functionalized gold nanoparticles for turn-on light switch detection of platelet-derived growth factor[J]. Analytical Chemistry, 2007, 79(13): 4798-4804. Jia S P, Liang M M, Guo L H. Photoelectrochemical detection of oxidative DNA damage induced by Fenton reaction with low concentration and DNA-associated Fe2+[J]. The Journal of Physical Chemisty B, 2008, 112(14): 4461-4464. Liang M M, Guo L H. Photoelectrochemical DNA sensor for the rapid detection of DNA damage induced by styrene oxide and the Fenton reaction[J]. Environmental Science & Technology, 2007, 41(2): 658-664.