The rheological properties of silated hydroxypropylmethylcellulose tissue engineering matrices

This paper describes the rheological properties of silated hydroxypropylmethylcellulose (HPMC-Si) used in biomaterials domain as a three-dimensional synthetic matrix for tissue engineering. The HPMC-Si is an HPMC grafted with 3-glycidoxypropyltrimethoxysilane (GPTMS). HPMC and HPMC-Si were studied. It is shown that although silanization reduces the hydrodynamic volume in dilute solution, it does not affect significantly the rheological behavior of the concentrated solutions. The HPMC-Si viscous solution (pH 12.8) cross-links by decreasing the pH using an acid buffer, since HPMC-Si solution transforms into an elastic state. The kinetics of cross-linking and final elastic properties is influenced by several parameters such as polymer concentration, pH and temperature. pH and temperature play an important role in the silanol condensation, mainly responsible for network formation. The study of the gelation process revealed the dependence of the final concentration of HPMC-Si hydrogel on cross-linking kinetics and viscoelastic properties. The percolation theory was applied to determine gel point and to discuss the dependence of storage (G') and loss (G'') moduli on frequency. Results showed that both G' and G'' exhibit a power-law behavior with an exponent (0.68) which extends over the entire frequency range. This method is the only one to characterize the time where a liquid viscous phase shifts to hydrogel with elastic properties. In this case it was about 23 min for a final pH of 7.4.