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Title: Interpreting holographic molecular binding assays with effective medium theory
Holographic molecular binding assays use holographic video microscopy to directly detect molecules binding to the surfaces of micrometer-scale colloidal beads by monitoring associated changes in the beads’ light-scattering properties. Holograms of individual spheres are analyzed by fitting to a generative model based on the Lorenz-Mie theory of light scattering. Each fit yields an estimate of a probe bead’s diameter and refractive index with sufficient precision to watch a population of beads grow as molecules bind. Rather than modeling the molecular-scale coating, however, these fits use effective medium theory, treating the coated sphere as if it were homogeneous. This effective-sphere analysis is rapid and numerically robust and so is useful for practical implementations of label-free immunoassays. Here, we assess how measured effective-sphere properties reflect the actual properties of molecular-scale coatings by modeling coated spheres with the discrete-dipole approximation and analyzing their holograms with the effective-sphere model.  more » « less
Award ID(s):
2027013
PAR ID:
10186185
Author(s) / Creator(s):
;
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Biomedical Optics Express
Volume:
11
Issue:
9
ISSN:
2156-7085
Format(s):
Medium: X Size: Article No. 5225
Size(s):
Article No. 5225
Sponsoring Org:
National Science Foundation
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