Silane-dextran chemistry on lateral flow polymer chips for immunoassays.

The prognosis for patients suffering from cardiovascular and many other diseases can be substantially improved if diagnosed at an early stage. High performance diagnostic testing using disposable microfluidic chips can provide a platform for realizing this vision. Amic AB (Uppsala, Sweden) has developed a new microfluidic test chip for sandwich immunoassays fabricated by injection molding of the cycloolefin-copolymer Zeonor. A highly ordered array of micropillars within the fluidic chip distributes the sample solution by capillary action. Since wetting of the pillar array surface is the only driving force for liquid distribution precise control of the surface chemistry is crucial. In this work we demonstrate a novel protocol for surface hydrophilization and antibody immobilization on cycloolefin-copolymer test chips, based on direct silanisation of the thermoplastic substrate. Dextran is subsequently covalently coupled to amino groups, thus providing a coating with a low contact angle suitable for antibody immobilization. The contact angle of dextran coated chips is stable for at least two months, which enables production of large batches that can be stored for extended periods of time. We demonstrate the utility of the presented platform and surface chemistry in a C-reactive protein assay with a detection limit of 2.6 ng ml(-1), a dynamic range of 10(2) and a coefficient of variance of 15%.

Lateral flow immunoassay using Europium (III) chelate microparticles and time-resolved fluorescence for eosinophils and neutrophils in whole blood.

BACKGROUND: A simple point-of-care method for measuring leukocyte counts in a doctor's office or emergency room could be of great importance. We developed a protocol for measuring cell count by disrupting the cell membrane and analyzing specific proteins within the cells and used it to analyze proteins from eosinophils and neutrophils. METHODS: Lateral immunochromatographic (ICR) assays have been developed for eosinophil protein X (EPX) and human neutrophil lipocalin (HNL) as measures of the concentration of eosinophils and neutrophils. The correlation between the lateral ICR assays and cell counting of eosinophils and neutrophils was performed manually and with an automated cell counter. RIA assays measuring the same analytes were also compared with the results from cell counting and lateral ICR assays. RESULTS: The optimized assays showed analytical detection limits below the clinical ranges of 3.36 microg/L and 2.05 microg/L for EPX and HNL, respectively. The recovery was 114.8%-122.8% for EPX and 94.5%-96.9% for HNL. The imprecision was 3%-17% CV for EPX over the whole range and 5%-16% CV for HNL. The correlation coefficients between manually counted cells and lateral ICR assays were 0.9 and 0.83 for EPX and HNL, respectively. CONCLUSION: The numbers of eosinophils and neutrophils in small amounts of blood can be estimated in the point-of-care setting by means of fast lateral ICR assays of EPX and HNL.