Biomarker mediated disruption of coffee ring formation as a low resource diagnostic indicator.
The ring pattern resulting from the unique microfluidics in an evaporating coffee drop is a well studied mass transport phenomenon generating interest in the research community mostly from a mechanistic perspective. In this report, we describe how biomarker induced particle particle assemblies, magnetic separation, and evaporation driven ring formation can be combined for simple pathogen detection. In this assay design, the presence of biomarkers causes self assembly of a magnetic nanoparticle and a fluorescently labeled micrometer sized particle. A small spherical magnet under the center of the drop prevents these assemblies from migrating to the drop's edge while a nonreactive control particle flows to the edge forming a ring pattern. Thus the presence or absence of biomarker results in distinctly different distributions of particles in the dried drop. Proof of principle studies using poly L histidine, a peptide mimic of the malaria biomarker pfHRPII, show that the predicted particle distributions occur with a limit of detection of approximately 200 300 nM.
Langmuir the ACS journal of surfaces and colloids