The nature of the
protein corona forming on biomaterial surfaces
can affect the performance of implanted devices. This study investigated
the role of surface chemistry and wettability on human serum-derived
protein corona formation on biomaterial surfaces and the subsequent
effects on the cellular innate immune response. Plasma polymerization,
a substrate-independent technique, was employed to create nanothin
coatings with four specific chemical functionalities and a spectrum
of surface charges and wettability. The amount and type of protein
adsorbed was strongly influenced by surface chemistry and wettability
but did not show any dependence on surface charge. An enhanced adsorption
of the dysopsonin albumin was observed on hydrophilic carboxyl surfaces
while high opsonin IgG2 adsorption was seen on hydrophobic hydrocarbon
surfaces. This in turn led to a distinct immune response from macrophages;
hydrophilic surfaces drove greater expression of anti-inflammatory
cytokines by macrophages, whilst surface hydrophobicity caused increased
production of proinflammatory signaling molecules. These findings
map out a unique relationship between surface chemistry, hydrophobicity,
protein corona formation, and subsequent cellular innate immune responses;
the potential outcomes of these studies may be employed to tailor
biomaterial surface modifications, to modulate serum protein adsorption
and to achieve the desirable innate immune response to implanted biomaterials
and devices.
All natural surfaces exhibit nanoscale roughness (NR) and chemical heterogeneity (CH) to some extent. Expressions were developed to determine the mean interaction energy between a colloid and a solid-water interface, as well as for colloid-colloid interactions, when both surfaces contain binary NR and CH. The influence of heterogeneity type, roughness parameters, solution ionic strength (IS), mean zeta potential, and colloid size on predicted interaction energy profiles was then investigated. The role of CH was enhanced on smooth surfaces with larger amounts of CH, especially for smaller colloids and higher IS. However, predicted interaction energy profiles were mainly dominated by NR, which tended to lower the energy barrier height and the magnitudes of both the secondary and primary minima, especially when the roughness fraction was small. This dramatically increased the relative importance of primary to secondary minima interactions on net electrostatically unfavorable surfaces, especially when roughness occurred on both surfaces and for conditions that produced small energy barriers (e.g., higher IS, lower pH, lower magnitudes in the zeta potential, and for smaller colloid sizes) on smooth surfaces. The combined influence of roughness and Born repulsion frequently produced a shallow primary minimum that was susceptible to diffusive removal by random variations in kinetic energy, even under electrostatically favorable conditions. Calculations using measured zeta potentials and hypothetical roughness properties demonstrated that roughness provided a viable alternative explanation for many experimental deviations that have previously been attributed to electrosteric repulsion (e.g., a decrease in colloid retention with an increase in solution IS; reversible colloid retention under favorable conditions; and diminished colloid retention and enhanced colloid stability due to adsorbed surfactants, polymers, and/or humic materials).
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