Transpiration-Inspired Fabrication of Opal Capillary with Multiple Heterostructures for Multiplex Aptamer-Based Fluorescent Assays

In this work we report a method for the fabrication of opal capillary with multiple heterostructures for aptamer-based assays. The method is inspired by plant transpiration. During the fabrication, monodisperse SiO₂ nanoparticles (NPs) self-assemble in a glass capillary, with the solvent gradually evaporating from the top end of the capillary. By a simple change of the colloid solution that wicks through the capillary, multiple heterostructures can be easily prepared inside the capillary. On the surface of the SiO₂ NPs, polydopamine is coated for immobilization of aminomethyl-modified aptamers. The aptamers are used for fluorescent detection of adenosine triphosphate (ATP) and thrombin. Owing to fluorescence enhancement effect of the photonic heterstructures, the fluorescent signal for detection is amplified up to 40-fold. The limit of detection is 32 μM for ATP and 8.1 nM for thrombin. Therefore, we believe this method is promising for the fabrication of analytical capillary devices for point-of-care testing.