Protein-polymer interaction is of great importance in developing novel materials for the protein chromatography. However, the direct observation of protein-polymer interactions is difficult, especially when the kinetic information is needed. In this work we use single molecule spectroscopy to investigate the in-situ dynamics of protein-polymer interactions and extract time-dependent adsorption rates for the adsorption of Alexa 555 labeled α-Lactalbumin to porous and nonporous nylon 6,6 thin films. By spin coating the nylon 6,6 solution on glass substrates, we synthesized a model polymer film with controllable thickness. Protein adsorption events at the polymer solution interface were recorded as spatially resolved movies, allowing the precise quantification of the adsorption rate and adsorption site distribution. We find that the adsorption rate is time dependent: with increasing experiment time, the rate decayed eventually reaching equilibrium. This time-dependent adsorption rate was modeled with a simple monolayer adsorption algorithm, which is related to the protein concentration in bulk solution and the available adsorption sites at the interface. We further studied the morphology affected adsorption kinetics by comparing the flat and porous nylon 6,6 films and found that the surface morphology of the porous nylon 6,6 films increased the number of adsorption sites but decreased the binding affinity compared to the flat film. It may be expected that such single-molecule fluorescence approaches could become a powerful tool to study the kinetics of other protein-polymer interactions, and to find the essential physical properties of polymer thin films.

Single-molecule kinetics of protein adsorption on thin nylon 6,6 films

251st National Meeting (2016)

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