Impact of Tether Length and Flexibility on the Efficiency of Analyte Capture by Tethered Receptors

Structure and functionality of molecular layers play a crucial role in determining the outcome of analyte-receptor interactions on affinity biosensors. The control over the structure of these molecular layers gives an independent means to enhance the sensor performance. Here we study the impact of the length and flexibility of molecular tethers on analyte capture by tethered receptors on quartz crystal microbalance and surface plasmon resonance sensors. Our results show clear enhancement of analyte-receptor interactions when receptors are bound to the sensor via flexible, and longer tethers. The findings further reveal a qualitative similarity of the impact of tether length on widely different type of binding interactions, viz. gold nanoparticle binding to tethered amine layers, and neutravidin binding to tethered biotin layers. By independent determination of tether densities, our investigations decouple the impact of receptor densities, and the tether conformations, and confirm the role of tether length on adsorption densities and kinetics. The results agree with theoretical reports in literature that predict enhanced analyte capture by receptors anchored to surface via long, flexible tethers, owing to enhanced freedom of movement and thereby its ability to “seek” the analyte in solution. These findings highlight the significance of factoring in the structure of the molecular tether to enhance analyte capture by tethered receptors, and thereby the performance of affinity biosensors.