Preparation of biodegradable crosslinking agents and application in PVP hydrogel

Firstly, biodegradable crosslinking agents (BCA) were synthesized by ring-opening polymerization reaction of lactide, four kinds of which with different molecular weights were got by means of changing the ratio of DL-lactide(LA) and glycerol(GL). Then a series of poly(N-vinyl pyrrolidone) (PVP) hydrogels were prepared successfully by radical polymerization of BCA and N-vinyl pyrrolidone(NVP). Both the ratio of NVP/BCA and the molecular weight of BCA were used to control the performance of PVP hydrogels, which were measured in terms of the ratio of swelling, contact angle, mechanical properties, and biodegradabitity in vitro. This study showed that increasing both the ratio of NVP/BCA and the molecular weight of BCA resulted in a low crosslinking density of the hydrogels. The crosslinking density played an important role in determining the properties of biodegradable PVP hydrogels. Both the ratio of NVP/BCA and the molecular weight of BCA contributed to high ratio of swelling. A smaller amount of crosslinking agent caused a lower contact angle, while the molecular weight of BCA had little effect on it. In terms of mechanics of hydrogels on both dry and wet conditions, tensile modulus decreased along with decreasing BCA, while the extension at break increased at the beginning and decreased at the end. In the end, measured by mass loss, biodegradability in vitro of hydrogels had two stages: an initial stage with approximately constant loss of mass (stage 1) followed by a stage with rapid mass loss (stage 2). Both increased content and molecular weight of BCA improved the degradation rate of the hydrogels. (c) 2006 Wiley Periodicals, Inc.