title: Label-free detection of 3-nitro-l-tyrosine with nickel-doped graphene localized surface plasmon resonance biosensor.
abstract: 3-nitro-l-tyrosine (3-NT) is believed to be a biomarker of neurodegenerative diseases and metal doped graphene possess exceptionally high binding energy of 3-NT with metal-nitro chemisorption. Here we report a novel label-free detection scheme of 3-NT via nickel-doped graphene (NDG) as the functionalized receptor on our phase detecting localized surface plasmon resonance (LSPR) biosensor. When compared with reported 3-NT immunoassay with enzyme-linked immunosorbent assay (ELISA), our NDG-LSPR platform offers two advantages i.e. 1) label-free and 2) capture of 3-NT by direct chemisorption. Our limit of detection for 3-NT in PBS was found to be 0.13pg/ml and the linear dynamic range of response was from 0.5pg/ml to 1ng/ml, i.e. four orders of magnitude. The specificity of our NDG receptor to 3-NT was also verified with l-tyrosine of equivalent concentrations in PBS and diluted human serum, for which the NDG receptor shows negligible responses. In addition, the adsorption of 3-NT and l-tyrosine to the NDG receptor were also investigated by atomic force microscopy and further verified by surface enhanced Raman spectroscopy. Therefore, our NDG-LSPR biosensor competes favorably against ELISA and we believe it should be an attractive and economical solution to early diagnostic of 3-NT related disorders for clinical applications.
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, PR China.
authors.forename: Siu Pang
authors.initials: SP
authors.lastname: Ng
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, PR China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Qiu
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, PR China; Shandong Academy of Sciences, Jinan, Shandong 250014, PR China.
authors.forename: Ning
authors.initials: N
authors.lastname: Ding
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong 266580, PR China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, PR China; Shandong Academy of Sciences, Jinan, Shandong 250014, PR China. Electronic address: lawrence.wu@cityu.edu.hk.
authors.forename: Chi-Man Lawrence
authors.initials: CL
authors.lastname: Wu
mesh_terms: D015415:Biomarkers / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D006046:Gold / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D057230:Limit of Detection; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D019636:Neurodegenerative Diseases / Q000175:diagnosis; D009532:Nickel / Q000737:chemistry*; D020349:Surface Plasmon Resonance / Q000379:methods*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: D015415:Biomarkers; C002744:3-nitrotyrosine; D014443:Tyrosine; D006046:Gold; D006108:Graphite; D009532:Nickel
keywords: 3-Nitro-l-tyrosine; Differential phase detection; Label-free biosensor; Localized surface plasmon resonance; Nickel-doped graphene