Analysis of the in vitro swelling behavior of poly(vinyl alcohol) hydrogels in osmotic pressure solution for soft tissue replacement.

An osmotic solution was used to evaluate poly(vinyl alcohol) (PVA) hydrogels as potential non-degradable soft tissue replacements in vitro. Osmotic solutions are necessary in order to mimic the swelling pressure observed in vivo for soft tissues present in load-bearing joints. In vitro studies indicated that PVA hydrogels experience minimal changes in swelling with a polymer concentration of 20 wt.% PVA in phosphate-buffered saline solution (0 atm) and between 30 and 35 wt.% PVA in osmotic solution with a pressure of 0.95 atm. Swelling in osmotic pressure solutions caused decreases in the equilibrium hydrogel hydration. An investigation of hydrogel compressive modulus indicated that PVA hydrogels are within the range of articular cartilage, meniscal tissue, and the temporomandibular joint disk. Furthermore, it is possible to tailor PVA hydrogels through careful modification of the polymer concentration and freeze-thaw cycles during hydrogel preparation to match both a desired swelling ratio and a desired compressive modulus or porosity. The microstructure of the PVA hydrogels was also evaluated as a function of freeze-thaw cycles and polymer concentration to give an insight into the processes occurring during synthesis and swelling in osmotic solutions.