Anomalous kinetics on low-fouling surfaces

Protein-surface interactions were probed in terms of adsorption and desorption on a low-fouling surface using single-molecule localization microscopy. Strikingly the experimental data show anomalous kinetics, evident as a surface dwell time distribution that exhibits a power-law distribution, i.e. a heavy-tailed rather than an exponential distribution. As a consequence, the average desorption rate depends upon the time scale of the experiment and the surface protein concentration does not reach equilibrium. Further analysis reveals that the observed anomalous desorption emerges due to the reversible formation of a small fraction of soluble protein multimers, such that each one desorbs from the surface at a different rate. The overall kinetics can be described by a series of elementary reactions, yielding simple scaling relations that predict experimental observations. This work reveals a mechanistic origin for anomalous adsorption/desorption kinetics that can be employed to define design principles for non-fouling surfaces and to predict their performance.