Impact of tether length and flexibility on the efficiency of analyte capture by tethered receptors

Molecular tethers that mediate the immobilization of receptors to the sensor surface, carry critical ability to influence sensor outcomes by determining how the receptors are presented to the analyte in the biological medium. An aspect that has however been less explored is the role of flexibility of such tethers in enhancing the efficiency of analyte capture by the receptor, by enhancing its ability to “seek” the analytes in solution. In the enclosed study, we show the length and flexibility of PEG tethers to have a strong influence on the binding of gold nanoparticles (AuNP) or neutravidin (NAv) to tethered amine or biotin receptors respectively. The qualitative similarity in the influence of the tethers, despite the largely dissimilar interactions that drive binding of AuNPs and NAv implies a generic influence at play. The impact of tether length or flexibility is decoupled from that of the density and conformation of tethers, using real-time, quantitative measurements performed using quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) sensors. Substituting neutravidin with neutravidin-conjugated gold nanoparticles accentuated the impact of the tether length, providing additional possibilities to harness the benefits of flexible tethers by increasing the analyte valency. The results emphasize the opportunity to enhance sensor performance by factoring in the influence of tether structure into the design of the sensor interface.