The adsorption behavior of collagen on solid surfaces is a process that determines the role of this protein to mediate cell–material interaction. Herein, the mechanism of self‐assembly and organization of collagen on a model substrate is investigated in the presence of TiO2 nanoparticles. In solution, results show that nanoparticles do not alter the conformation of collagen (triple‐helix), and slightly delay the kinetics of its self‐assembly. In the adsorbed state, by exploring the dewetting patterns of collagen layers from atomic force microscopy (AFM) images, a method is developed to extract parameters describing the characteristics of collagen networks. It is shown that collagen layer is strongly impacted by the presence of nanoparticles in the medium. These results are consistent with the analysis of the protein layers in the hydrated state, showing a rigidification, as observed by quartz crystal microbalance with dissipation monitoring (QCM‐D), and the formation of shorter and/or less extended fibrillar structures with a lower surface density, as probed by AFM force spectroscopy. The approach described here provides a reconciliation between disparate views of collagen layers' characterization in the dried and the hydrated states. It also offers new perspectives to assess the impact of nanoparticles on the organization of collagen during in vitro tests, particularly at the stage of cell adhesion.
Herein, we report the coating of a surface with a random nanoscale topography with a lipid film formed by an anchoring stearic acid (SA) monolayer and phospholipid (DPPC) layers. For this purpose, different procedures were used for phospholipid coating, including adsorption from solution, drop deposition, and spin-coating. Our results reveal that the morphology of the obtained lipid films is strongly influenced by the topography of the underlying substrate but also impacted by other factors, including the coating procedure and surface wettability (modulated by the presence of SA). These coated surfaces showed a remarkable antifouling behavior toward proteins, with different yields of repellency (Y) depending on the amount/organization of DPPC on the nanostructured substrate. The interaction between the proteins and phospholipids involves a partial detachement of the film. The use of characterization techniques with different charcateristics (accuracy, selectivity, analysis depth) did not reveal any obvious vertical heterogenity of the probed interface, indicating that the lipid film acts as a nonfouling coating on the whole surface, including the outermost part (nanoprotrusions) and deeper regions (valleys).
Understanding
the wetting properties of chemically modified inorganic
surfaces with random nanoscale topographies is of fundamental importance
for diverse applications. This issue has hitherto continuously been
the subject of considerable controversies. Herein, we report a thorough
investigation of the wettability–topography–chemistry
balance for a nanostructured surface with random topography, the main
challenge being decoupling topography from surface chemistry. For
this purpose, we use a superficially nanostructured aluminum substrate
chemically modified by fatty acid monolayers. From atomic force microscopic
data, we extract a variety of parameters describing the surface topography
by means of variogram calculations, a method originally developed
by geostatisticians to explore large surfaces. Moreover, by using
log and power transforms, we establish a consistent relationship relating
wettability, topography, and surface chemistry. Interestingly, we
demonstrate that the water contact angle comprises a contribution
due to the surface composition, originating from hydrophobization
through alkyl chains, and a contribution due to the surface topography,
particularly its stochastic feature. This model is valid in the Wenzel
region; it provides guidelines for tuning the wetting properties of
inorganic surfaces with random nanoscale topographies.
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