Terahertz imaging for label-free protein detection

We demonstrate an imaging method combined a terahertz time-domain spectroscopy and an interference effect for label-free protein detection on a membrane filter. Biotin is linked to the membrane using poly ethylene glycol (PEG) or poly ethylene glycol methyl ether (MPEG) to prevent it from being washed off. Binding of the biotin with streptavidin is then observed by measuring the terahertz signal change due to the variation of the membrane refractive index. From result of competition binding experiments, it becomes clear that specific binding of antibody protein are detected by using this imaging method. This technique is used only to detect the existence of the binding. And the selectivity depends absolutely on specific ligand-protein interactions. This measurement principle is suitable to high throughput detection for drug discovery.