title: Ultrasensitive photoelectrochemical immunoassay for matrix metalloproteinase-2 detection based on CdS:Mn/CdTe cosensitized TiO2 nanotubes and signal amplification of SiO2@Ab2 conjugates.
abstract: An ultrasensitive photoelectrochemical sandwich immunoassay was developed to detect matrix metalloproteinase-2 (MMP-2, antigen, Ag) based on CdS:Mn/CdTe cosensitized TiO2 nanotubes (TiO2-NTs) and signal amplification of SiO2@Ab2 conjugates. Specifically, the TiO2-NTs electrode was first deposited with CdS:Mn by successive ionic layer adsorption and reaction technique and then further coated with CdTe quantum dots (QDs) via the layer-by-layer method, forming TiO2-NTs/CdS:Mn/CdTe cosensitized structure, which was employed as a matrix to immobilize capture MMP-2 antibodies (Ab1); whereas, SiO2 nanoparticles were coated with signal MMP-2 antibodies (Ab2) to form SiO2@Ab2 conjugates, which were used as signal amplification elements via the specific antibody-antigen immunoreaction between Ag and Ab2. The ultrahigh sensitivity of this immunoassay derived from the two major reasons as below. First, the TiO2-NTs/CdS:Mn/CdTe cosensitized structure could adequately absorb the light energy, dramatically promote electron transfer, and effectively inhibit the electron-hole recombination, resulting in significantly enhanced photocurrent intensity of the sensing electrode. However, in the presence of target Ag, the immobilized SiO2@Ab2 conjugates could evidently increase the steric hindrance of the sensing electrode and effectively depress the electron transfer, leading to obviously decreased photocurrent intensity. Accordingly, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 3.6 fg/mL and a wide linear range from 10 fg/mL to 500 pg/mL for target Ag detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising platform for the detection of other important biomarkers.
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing 210093, People's Republic of China.
authors.forename: Gao-Chao
authors.initials: GC
authors.lastname: Fan
authors.forename: Li
authors.initials: L
authors.lastname: Han
authors.forename: Hua
authors.initials: H
authors.lastname: Zhu
authors.forename: Jian-Rong
authors.initials: JR
authors.lastname: Zhang
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Zhu
mesh_terms: D019187:Cadmium Compounds / Q000378:metabolism*; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D008345:Manganese / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D055668:Photochemical Processes; D018036:Selenium Compounds / Q000378:metabolism*; D012822:Silicon Dioxide / Q000378:metabolism*; D013691:Tellurium / Q000378:metabolism*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D008345:Manganese; D012822:Silicon Dioxide; C058667:cadmium selenide; D020778:Matrix Metalloproteinase 2; D013691:Tellurium; C028337:cadmium telluride