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

Here, a novel method of immobilizing proteins with well‐defined 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.