Biomarker-Mediated Disruption of Coffee-Ring Formation as a Low Resource Diagnostic Indicator

• Published in: Langmuir 2012-01, Vol.28 (4), p.2187-2193
• Main Authors: Trantum, Joshua R, Wright, David W, Haselton, Frederick R
• Format: Article
• Language: English
• Subjects: Antigens, Protozoan - metabolism; Biomarkers - analysis; Biomarkers - chemistry; Biomimetic Materials - chemistry; Biomimetic Materials - metabolism; Clinical Chemistry Tests - instrumentation; Fluorescent Dyes - chemistry; Histidine - chemistry; Histidine - metabolism; Limit of Detection; Magnets - chemistry; Malaria - diagnosis; Malaria - metabolism; Microfluidic Analytical Techniques - instrumentation; Nanoparticles - chemistry; Protozoan Proteins - metabolism; Volatilization
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la203903a

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.