Nanomaterials, which come into contact with blood, are immediately covered with blood plasma proteins. Those proteins form the so called hard and soft protein corona, which relates to their respective binding affinities and exchange rates. While there is a lot of research focusing on the characterization of the hard protein corona, the soft protein corona is only barely understood as it can be only identified with methods like dynamic light scattering (DLS) or isothermal titration calorimetry (ITC), that require no extraction from the interaction medium. By a combination of different techniques we were able to combine hard and soft corona characteristics and to distinguish between hard and soft corona proteins.We investigated the adsorption of plasma proteins onto differently functionalized hydroxyethyl-starch nanocapsules as well as the interaction with single proteins (human serum albumin (HSA), apolipoprotein A1 (ApoA1)). We applied SDS-PAGE and a protein assay to characterize the hard corona. The protein pattern and adsorbed protein amounts of the hard corona did not change significantly for all types of capsules. Further, ITC and DLS were applied to analyze the soft protein corona. ITC revealed that several thousand plasma proteins are loosely associated with all capsules after adsorption, leading to an increase of the hydrodynamic radius of 80-100 nm. The investigated processes are all enthalpy driven and indicate only weak interactions. Whereas the interaction of HSA with all capsules is similar to the plasma mixture, ApoA1 behaves very different. The binding affinity for ApoA1 is around 40 times higher than for HSA, but surprisingly only about 10 molecules are adsorbed to the surface. DLS measurements confirmed aggregates with increased size for HSA but not for ApoA1 adsorption. Additionally NH2-functionalized capsules produced a strong endothermic reaction with ApoA1 along with a large entropy increase, most likely arising from a structure change upon adsorption.

Correlation of hard and soft protein corona for sugar-based nanocapsules

248th National Meeting (2014)

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