Single antibody detection in a DNA origami nanoantenna.

DNA nanotechnology offers new biosensing approaches by templating different sensor and transducer components. Here, we combine DNA origami nanoantennas with label-free antibody detection by incorporating a nanoswitch in the plasmonic hotspot of the nanoantenna. The nanoswitch contains two antigens that are displaced by antibody binding, thereby eliciting a fluorescent signal. Single-antibody detection is demonstrated with a DNA origami integrated anti-digoxigenin antibody nanoswitch. In combination with the nanoantenna, the signal generated by the antibody is additionally amplified. This allows the detection of single antibodies on a portable smartphone microscope. Overall, fluorescence-enhanced antibody detection in DNA origami nanoantennas shows that fluorescence-enhanced biosensing can be expanded beyond the scope of the nucleic acids realm.