Amphiphilic derivatives of sodium alginate and hyaluronate for cartilage repair: rheological properties.

Various amphiphilic derivatives of sodium alginate and hyaluronate were prepared by covalent fixation of long alkyl chains (dodecyl and octadecyl) with various ratios on the polysaccharide backbones via ester functions. In the semidilute regime, aqueous solutions of the resulting compounds exhibited the typical rheological properties of hydrophobically associating polymers: tremendous enhancement of zero shear rate Newtonian viscosity, steep shear-thinning behavior, and formation of physically cross-linked gel-like networks. The influence of the alkyl chain length, its content on the polysaccharide and of the polymer concentration in the solution was well identified. All obtained results are discussed with respect to the schedule of conditions related to materials, which could be used for cartilage repair, such as in synovial fluid viscosupplementation as well as in cartilage replacement. In particular, it is seen that HA-C(12)-5 (hyaluronate substituted with 5% of dodecyl chains) and HA-C(18)-1 (hyaluronate substituted with 1% of octadecyl chains) in a 0.15N NaCl solution at 8 g/L have rheological properties quite similar to those of healthy synovial fluid. On the other hand, the rheological parameters of solutions at 8 g/L in 0.15N NaCl of some of derivatives, such as, for example, AA-C(12)-8 (alginate substituted with 8% of dodecyl chains) or HA-C(18)-2, are well fitted for a use in cartilage repair.