Decorating Liquid Crystal Surfaces with Proteins for Real-Time Detection of Specific Protein-Protein Binding

Here, a novel method of immobilizing proteins with well-define orientation directly on liquid crystal surfaces that allow subsequent real-time imaging of specific protein-protein binding events on these surfaces is reported. Self- assembly of nitrilotriacetic acid terminated amphiphiles loaded with Ni2+ ions at aqueous-liquid crystal interface creates a surface capable of immobilizing histidine-tagged ubiquitin through complex formation between Ni2+ and histidine. When these surfaces containing immobilized histidine- tagged ubiquitin are exposed to anti-ubiquitin antibody, the spatial and temporal of specific protein-protein binding events trigger orientational transitions of liquid crystals. As a result, sharp liquid crystal optical switching from dark to bright can readily be observed under polarized lighting. The protein-protein binding can be observed within seconds and only requires nanogram quantities of proteins. This work demonstrates a simple strategy to immobilize proteins with well-defined orientation on liquid crystal surfaces for real-time and label-free detection of specific protein-protein binding events, which may find use in biomedical diagnostics.