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Issue 10, 2005
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Detection of picomolar levels of interleukin-8 in human saliva by SPR

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Abstract

Researchers at UCLA have discovered that the levels of interleukin-8 (IL-8) protein in the saliva of healthy individuals and patients with oropharyngeal squamous cell carcinoma (OSCC) are 30 pM and 86 pM, respectively. In this study, we present the development of the first immunoassay for the quantification of picomolar IL-8 concentrations in human saliva using Biacore surface plasmon resonance (SPR) in a microfluidic channel. A sandwich assay using two monoclonal antibodies, which recognize different epitopes on the antigen (IL-8), was used. Only 13 minutes were required to determine the quantity of pure IL-8 added to just 100 µL of either buffer or saliva-based samples. The limit of detection (LOD) of this immunoassay in buffer was 2.5 pM, and the precision of the response for each concentration was <3% of the coefficient of variation. When first analyzing the saliva supernatants, non-specific binding to the surface was observed. By adding carboxymethyl dextran sodium salt (10 mg mL−1) to compete with the surface dextran and primary antibody for non-specific interactions, the signal to noise ratio was greatly improved. The LOD of this immunoassay in saliva was 184 pM. A minimum concentration of 250 pM of exogenous IL-8 could then be consistently detected in a salivary environment. The precision of the response for each IL-8 concentration tested was <7% of the coefficient of variation. Diagnostic sensitivity for oral cancer can be achieved by pre-concentrating the saliva samples 10 fold prior to SPR analysis, making the target levels of IL-8 300 pM for healthy individuals and 860 pM for oral cancer patients.

Graphical abstract: Detection of picomolar levels of interleukin-8 in human saliva by SPR

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Publication details

The article was received on 05 Apr 2005, accepted on 04 Aug 2005 and first published on 18 Aug 2005


Article type: Paper
DOI: 10.1039/B504737D
Citation: Lab Chip, 2005,5, 1017-1023
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    Detection of picomolar levels of interleukin-8 in human saliva by SPR

    C. Yang, E. Brooks, Y. Li, P. Denny, C. Ho, F. Qi, W. Shi, L. Wolinsky, B. Wu, D. T. W. Wong and C. D. Montemagno, Lab Chip, 2005, 5, 1017
    DOI: 10.1039/B504737D

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