Effect of metal ions on the physical properties of multilayers from hyaluronan and chitosan, and the adhesion, growth and adipogenic differentiation of multipotent mouse fibroblasts.

Polyelectrolyte multilayers (PEMs) consisting of the polysaccharides hyaluronic acid (HA) as the polyanion and chitosan (Chi) as the polycation were prepared with layer-by-layer technique (LbL). The [Chi/HA] multilayers were exposed to solutions of metal ions (Ca, Co, Cu and Fe). Binding of metal ions to [Chi/HA] multilayers by the formation of complexes with functional groups of polysaccharides modulates their physical properties and the bioactivity of PEMs with regard to the adhesion and function of multipotent murine C3H10T1/2 embryonic fibroblasts. Characterization of multilayer formation and surface properties using different analytical methods demonstrates changes in the wetting, surface potential and mechanical properties of multilayers depending on the concentration and type of metal ion. Most interestingly, it is observed that Fe metal ions greatly promote adhesion and spreading of C3H10T1/2 cells on the low adhesive [Chi/HA] PEM system. The application of intermediate concentrations of Cu, Ca and Co as well as low concentrations of Fe to PEMs also results in increased cell spreading. Moreover, it can be shown that complex formation of PEMs with Cu and Fe ions leads to increased metabolic activity in cells after 24 h and induces cell differentiation towards adipocytes in the absence of any additional adipogenic media supplements. Overall, complex formation of [Chi/HA] PEM with metal ions like Cu and Fe represents an interesting and cheap alternative to the use of growth factors for making cell-adhesive coatings and guiding stem cell differentiation on implants and scaffolds to regenerate connective-type of tissues.