Surface-based single-liposome sensing for diagnostics and drug screening applications

Fredrik Höök1,*

1Applied Physics, Chalmers, Gothenburg, Sweden

Measurements of ligand binding events on membrane protein receptors in a near-natural environment would display an advantage in mechanistic studies of membrane receptors. Furthermore, the residence time of drug-target interactions is being increasingly recognized as a key parameter in evaluating drug efficacy, but is hampered by the technical challenge to perform such studies for e.g. membrane proteins and virus particles. With single-molecule sensitivity, such information can be gained for both high and low affinity interactions, and be used in both drug-screening and medical-diagnostic applications. Recent advancement in nanotechnology has led to a diverse set of tools offering single-molecule sensitivity. To yield sufficient statistics within reasonable time scales, multiple single biomolecular binding events should preferably be probed simultaneously in imaging mode. I will present a single-molecule detection concept that meets this requirement, and which enables simultaneous fluorescent and label-free operation. The principle is based on the use of lipid vesicles as enhancer elements in optical waveguide based fluorescence and label-free scattering microscopy, making the concept compatible with analysis of both water-soluble and cell-membrane bound receptors. Focus will be put on how the concept is currently evaluated as a diagnostic assay for virus and biomarker detection as well as drug-screening applications, previously explored by us using conventional total internal reflection fluorescence microscopy[1,2]. I will also discuss the use of the wave-guide microscopy system in the context of single-enzyme detection in complex biological fluids, with focus on single-molecule biomarker detection in cerebrospinal fluid from individuals suffering from the Alzheimer’s disease[3].

[1] Bally M et al. PRL 2011, 107: # 188103

[2] Gunnarsson A et al. JACS 2011, 133: 14852

[3] Tabaei, S. R. et al. JACS 2013, 135 (38), 14151.

Keywords: Biomarker, Brain, Method