Shake It or Shrink It: Mass Transport and Kinetics in Surface Bioassays Using Agitation and Microfluidics

Surface assays, such as ELISA and immunofluorescence, are nothing short of ubiquitous in biotechnology and medical diagnostics today. The development and optimization of these assays generally focuses on three aspects: immobilization chemistry, ligand–receptor interaction, and concentrations of liga...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2020-08, Vol.92 (15), p.10187-10195
Main Authors: Pereiro, Iago, Fomitcheva-Khartchenko, Anna, Kaigala, Govind V
Format: Article
Language:English
Subjects:
Agitation
Assaying
Bioassays
Biological Assay - methods
Biotechnology
Buffers (chemistry)
Chemistry
Depletion
Enzyme-linked immunosorbent assay
Enzyme-Linked Immunosorbent Assay - methods
Fluorescent Antibody Technique - methods
Immobilization
Immunofluorescence
Kinetics
Ligands
Mass transport
Microfluidic Analytical Techniques - methods
Microfluidics
Optimization
Reaction kinetics
Reagents
Shear stress
Surface tension
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Summary:Surface assays, such as ELISA and immunofluorescence, are nothing short of ubiquitous in biotechnology and medical diagnostics today. The development and optimization of these assays generally focuses on three aspects: immobilization chemistry, ligand–receptor interaction, and concentrations of ligands, buffers, and sample. A fourth aspect, the transport of the analyte to the surface, is more rarely delved into during assay design and analysis. Improving transport is generally limited to the agitation of reagents, a mode of flow generation inherently difficult to control, often resulting in inconsistent reaction kinetics. However, with assay optimization reaching theoretical limits, the role of transport becomes decisive. This perspective develops an intuitive and practical understanding of transport in conventional agitation systems and in microfluidics, the latter underpinning many new life science technologies. We give rules of thumb to guide the user on system behavior, such as advection regimes and shear stress, and derive estimates for relevant quantities that delimit assay parameters. Illustrative cases with examples of experimental results are used to clarify the role of fundamental concepts such as boundary and depletion layers, mass diffusivity, or surface tension.
ISSN:0003-2700
1520-6882
DOI:10.1021/acs.analchem.0c01625