Thermophoresis in Nanoliter Droplets to Quantify Aptamer Binding


  • Financial support through a joint grant (BR2152/2-1) and project A4 within SFB 1032 from the Deutsche Forschungsgemeinschaft (DFG), by the Center for NanoScience (CeNS), and by the Nanosystems Initiative Munich (NIM) is gratefully acknowledged. The authors would like to thank Maximilian Weitz from the group of Friedrich C. Simmel for sharing his knowledge on microemulsions, Georg C. Urtel for support in building the setup and Christof B. Mast for programming support.


Biomolecule interactions are central to pharmacology and diagnostics. These interactions can be quantified by thermophoresis, the directed molecule movement along a temperature gradient. It is sensitive to binding induced changes in size, charge, or conformation. Established capillary measurements require at least 0.5 μL per sample. We cut down sample consumption by a factor of 50, using 10 nL droplets produced with acoustic droplet robotics (Labcyte). Droplets were stabilized in an oil–surfactant mix and locally heated with an IR laser. Temperature increase, Marangoni flow, and concentration distribution were analyzed by fluorescence microscopy and numerical simulation. In 10 nL droplets, we quantified AMP-aptamer affinity, cooperativity, and buffer dependence. Miniaturization and the 1536-well plate format make the method high-throughput and automation friendly. This promotes innovative applications for diagnostic assays in human serum or label-free drug discovery screening.