Rapid one-step whole blood C-reactive protein magnetic permeability immunoassay with monoclonal antibody conjugated nanoparticles as superparamagnetic labels and enhanced sedimentation

• Published in: Analytical and bioanalytical chemistry Vol. 384; no. 3; pp. 651 - 657
• Main Authors: Ibraimi, Filiz, Kriz, Dario, Lu, Min, Hansson, Lars-Olof, Kriz, Kirstin
• Format: Journal Article
• Language: English
• Published: Germany Berlin/Heidelberg : Springer-Verlag 01.02.2006
• Subjects: Analytical Chemistry; Analytisk kemi; Antibodies, Monoclonal - chemistry; C-reactive protein; C-Reactive Protein - analysis; Calibration; Chemical Sciences; Humans; immunoassay; Immunoassay - methods; Kemi; Magnetic permeability; Magnetics; magneto; Magneto immunoassay; Nanoparticles - chemistry; Natural Sciences; Naturvetenskap; Particle Size; Point-of-care; Reproducibility of Results; Sensitivity and Specificity; Silicon Dioxide - chemistry; Superparamagnetic nanoparticles; Surface Properties
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-005-0094-6

A rapid (5.5 min) one-step whole blood C-reactive protein (CRP) magnetic permeability immunoassay utilizing monoclonal antibody conjugated dextran iron oxide nanoparticles (70 nm) as superparamagnetic labels and mixed fractions (1:1 ratio of 15-40 and 60 μm) of polyclonal anti-CRP conjugated silica microparticles for enhanced sedimentation is described. In this one-step assay procedure, a whole blood sample (4 μl) is applied to an assay glass vial, containing both antibody conjugates, and mixed for 30 s. The target analyte, CRP, forms a sandwich complex between the conjugated nanoparticles and microparticles, and, subsequently, the complex sediments under normal gravitation within 5 min to the bottom of the vial. The magnetic permeability increase of the sediment due to the presence of the complexed superparamagnetic nanoparticles is determined using an inductance-based transducer. Assayed patient whole blood samples were compared with the Abbott Diagnostics Architect reference method. A strong linear correlation was observed for the CRP concentration range 0-260 mg/l in whole blood (y=1.001x+0.42, R ²=0.982, n=50). The CRP assay presented showed a limit of detection of 3 mg/l and a total imprecision (coefficient of variation) of 10.5%. On the basis of our observations, we propose a rapid, one-step, CRP assay for near-patient testing.