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Inspired by the composition of the native extracellular matrix, biomimetic polyelectrolyte multilayers were assembled from polypeptides and the glycosaminoglycan chondroitin sulfate (CS). To investigate whether peptide conformation imposes an effect on the cell biological functions of osteoblasts, the secondary structure was analyzed by in situ infra-red and circular dichroism spectroscopy. Multilayers composed of polypeptides and CS reveal a predominantly random coiled conformation and impede osteoblast spreading. On the contrary, polypeptide chains in assemblies of poly-L-lysine and poly-L-glutamic acid (PGA) primarily adopt an intermolecular β sheet structure and reveal an increased area of spread, which consequently supports the proliferation of osteoblasts. When CS is replaced by PGA in mixed multilayers, we observe a structural rearrangement from random coils to β sheets with a concomitant improved cell response. We conclude that polypeptide conformation in biomimetic multilayer assemblies affects osteoblast response by altering the stiffness of the multilayer.

Coatings of biomaterials or implants that facilitate biomineralization possess a great potential for applications focused to the replacement, augmentation, and regeneration of bone tissue. Biomimetic approaches utilize biomolecules for either templating or supporting the crystallization process. One of these promising biomolecules is phosvitin (PV), an egg yolk protein known to transport and store inorganic phosphates and calcium ions. The incorporation of PV into polyelectrolyte multilayers is favorable due to PVs high degree of phosphorylation and thus a high acidity. Utilizing the reflectometric interference spectroscopy, the adsorption kinetics of this novel polyelectrolyte system composed of poly-L-lysine and the heavily phosphorylated phosvitin were monitored. The results demonstrate an unexpected nonregular growth regime called overshoot. Effective measures of shifting this irregular polyelectrolyte adsorption process back to a regular multilayer growth regime are reported in this paper.