External diffusion in solid-phase immunoassays |
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| Authors: | M Stenberg L Stiblert H Nygren |
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| Institution: | 1. National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland;2. Universidade Federal de São Carlos, CCTS, Rod. João Leme dos Santos, km 110, CEP 18052-780, Sorocaba, São Paulo, Brazil;1. Research Institute for Brain and Blood Vessels-AKITA, Akita, Japan;2. Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan;3. Department of Oral Diagnosis & Radiology, Tohoku University Graduate School of Dentistry, Sendai, Japan;4. Department of Neurology-Vascular Neurology and Neurocritical Care, Baylor College of Medicine, Houston, TX, USA;1. GeoRessources Laboratory, Université de Lorraine (ENSG), CNRS, CREGU, F-54518 Vandoeuvre-lès-Nancy, France;2. Mechanical & Aerospace Engineering, New Mexico State University, PO Box 30001 / MSC 3450, Las Cruces, NM 88003, USA |
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| Abstract: | Calculations are presented describing the influence of external diffusion in the kinetics of solid-phase immunoassays. The analysis is concerned with systems where one reactant is immobilized at the surface of a sphere of arbitrary radius. The solution for a plane surface is found as a limiting case. The factors determining whether the reaction is diffusion or reaction controlled are found to be sphere radius, surface concentration of binding sites, forward reaction rate and diffusion constant of reacting species. Means of determining whether the reaction is diffusion or reaction controlled from observable quantities are described. When applied to heterogeneous antibody-antigen binding it is found that normally the binding to cell-size spheres is not limited by external diffusion. However, when applied to solid-phase assays with high surface concentrations of binding sites immobilized at plane surfaces or macroscopic spheres the binding is found to be diffusion limited. The importance of a mass transfer analysis in this case is also discussed. |
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