A combination of magnetic permeability detection with nanometer-scaled superparamagnetic tracer and its application for one-step detection of human urinary albumin in undiluted urine.
A rapid (6.5 min) and simple one-step magnetic immunoassay (MIA) has been developed for analysis of human urinary albumin in near patient settings. Polyclonal rabbit anti-human albumin was used as a capture antibody and monoclonal mouse anti-human albumin as a detection antibody in a two-site immunometric assay requiring no additional washing procedures. The polyclonal anti-human albumin was conjugated to silica microparticles (solid phase) and the monoclonal antibody to dextran-coated nanoscaled superparamagnetic particles (tracer). Quantification of human albumin in undiluted urine was performed by adding 2 microL urine to a measuring vial containing solid-phase, superparamagnetic tracer and reaction buffer and then inverting the vial by hand for 20 s. The measuring vial was allowed to stand for 6 min prior to detection, in order for the solid-phase sediment to form at the bottom of the vial. Lastly, the measuring vial was placed into a magnetic permeability detector, which measured the enrichment of superparamagnetic tracer in the sediment due to complex formation with human albumin. Total analysis time was 6.5 min. A linear response was obtained for 0-400 mg/L albumin with a detection limit of 5 mg/L. The total coefficient of variation (CV) was 11% calculated from four consecutive runs on a urine sample containing 11.1 mg/L human albumin during 3 consecutive days. Human urinary albumin analysis was performed on 149 patient samples using the MIA technique and the obtained results showed good correlation with the hospital immunoturbidimetric reference method (y = 1.004x + 4.01, R2 = 0.978, N = 149) and a commercially available point of care albumin analysis provided by HemoCue Inc. (y = 0.98x + 5.8, R2 = 0.833, N = 90).
Lu
Min
M
LifeAssays AB, Research Park Ideon, SE-223 70 Lund, Sweden.
Ibraimi
Filiz
F
Kriz
Dario
D
Kriz
Kirstin
K
D000418:Albumins / Q000032:analysis*; D000419:Albuminuria / Q000652:urine*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D006801:Humans; D018189:Immunomagnetic Separation / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods; D016482:Urinalysis / Q000295:instrumentation* / Q000379:methods; D014556:Urine
D000418:Albumins