title: A Method for Designing Instrument-Free Quantitative Immunoassays.
abstract: Colorimetric readouts are widely used in point-of-care diagnostic immunoassays to indicate either the presence or the absence of an analyte. For a variety of reasons, it is more difficult to quantify rather than simply detect an analyte using a colorimetric test. We report a method for designing, with minimal iteration, a quantitative immunoassay that can be interpreted objectively by a simple count of number of spots visible to the unaided eye. We combined a method called polymerization-based amplification (PBA) with a series of microscale features containing a decreasing surface density of capture molecules, and the central focus of the study is understanding how the choice of surface densities impacts performance. Using a model pair of antibodies, we have shown that our design approach does not depend on measurement of equilibrium and kinetic binding parameters and can provide a dynamic working range of 3 orders of magnitude (70 pM to 70 nM) for visual quantification.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Shefali
authors.initials: S
authors.lastname: Lathwal
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Hadley D
authors.initials: HD
authors.lastname: Sikes
mesh_terms: D002138:Calibration; D003124:Colorimetry; D007118:Immunoassay / Q000379:methods*; D058105:Polymerization