Highly sensitive microfluidic detection of carcinoembryonic antigen via a synergetic fluorescence enhancement strategy based on the micro/nanostructure optimization of ZnO nanorod arrays and in situ ZIF-8 coating

In this work, a synergetic fluorescence enhancement strategy based on micro/nanostructure optimization of ZnO nanorod arrays and in situ ZIF-8 coating was proposed for the highly sensitive microfluidic detection of carcinoembryonic antigen (CEA). The glass capillary was chosen as the microfluidic channel, and controllable construction of ZnO nanorod arrays on the inner wall of the microchannel was conducted via the intermittent reaction method. Additionally, the application of the optimal ZnO nanorod array to glass capillary-based microfluidic fluorescence detection was demonstrated. The fluorescence enhancement characteristic of the zeolitic imidazolate framework-8 (ZIF-8) towards organic fluorescence labels were investigated and successfully applied to protein marker detection. After formation of sandwich immunoassay on the ZnO/PAA nanorod arrays, the in situ ZIF-8 coating via a moderate chemical method could significantly improve the fluorescence intensity of fluorescent labels via direct contact. In CEA detection, the limit of detection (LOD) reached as low as 0.01 pg mL−1, and the dynamic range was 0.01 pg mL−1 to 100 pg mL−1. Hence, the microfluidic fluorescence detection strategy based on the ZnO nanorod arrays/PAA layers/ZIF-8 coating with a synergetic fluorescence enhancement effect provides a superior, promising, and highly sensitive approach for the detection of protein markers, including CEA.