title: Competitive-type displacement reaction for direct potentiometric detection of low-abundance protein.
abstract: Prostate-specific antigen (PSA), one of the indications of possible prostate malignancy, is used as a biomarker for the diagnosis and prognosis of prostate cancer. Herein, we develop a new homogeneous potentiometric immunoassay for sensitive detection of low-concentration PSA without the need of sample separation and washing step. Two nanostructures including positively charged polyethyleneimine-poly(styrene-co-acrylic acid) (PEI-PSAA) nanospheres and negatively charged gold nanoparticles conjugated with anti-PSA antibody (Ab-AuNP) were first synthesized by using mulsifier-free emulsion copolymerization and wet chemistry method, respectively. Thereafter, the as-prepared PEI-PSAA was used as a pseudo hapten for the construction of immunosensing probe based on an electrostatic interaction between PEI-PSAA and Ab-AuNP. Upon target introduction, the added PSA competed with PEI-PASS for Ab-AuNP based on a specific antigen-antibody interaction, and displaced Ab-AuNP from PEI-PASS. The dissociated PEI-PASS was captured through the negatively charged Nafion- modified electrode, thereby resulting in the change of membrane potential. The fabrication process was characterized by using high-resolution transmission electron microscope (HRTEM), scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDX), surface plasmon resonance (SPR) and dynamic laser scattering (DLS) technique. Under optimal conditions, the output signal was indirectly proportional to the concentration of target PSA in the sample and exhibited a dynamic range from 0.1 to 50 ng/mL with a detection limit (LOD) of 0.04 ng/mL. Intra- and inter-assay coefficients of variation (CVs) were 6.8 and 7.5%, respectively. In addition, the methodology was evaluated for analysis of 12 clinical serum samples and showed good accordance between the results obtained by the developed immunosensing protocol and a commercialized enzyme-linked immunosorbent assay (ELISA) method.
authors.affiliation: Key Laboratory of Analysis and Detection for Food Safety, Ministry of Education & Fujian Province, Department of Chemistry, Fuzhou University, Fuzhou 350108, PR China.
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.forename: Bingqian
authors.initials: B
authors.lastname: Liu
authors.forename: Guonan
authors.initials: G
authors.lastname: Chen
authors.forename: Dianping
authors.initials: D
authors.lastname: Tang
mesh_terms: D000937:Antigen-Antibody Reactions; D015374:Biosensing Techniques / Q000379:methods*; D006046:Gold; D006801:Humans; D007118:Immunoassay; D008297:Male; D053768:Metal Nanoparticles; D046529:Microscopy, Electron, Transmission; D054118:Nanospheres; D011199:Potentiometry; D017430:Prostate-Specific Antigen / Q000097:blood / Q000302:isolation & purification*; D011471:Prostatic Neoplasms / Q000097:blood*; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold; D017430:Prostate-Specific Antigen
keywords: Competitive-type displacement reaction; Nanogold-labeled antibody; Polyethyleneimine-poly(styrene-co-acrylic acid) microsphere; Potentiometric immunoassay; Prostate-specific antigen