Polymer Bulletin 46, 91–98 (2001) * Corresponding author Polymer Bulletin  Springer-Verlag 2001 In vitro dynamic swelling behaviors of polyhydroxamic acid hydrogels in the simulated physiological body fluids Dursun Saraydin * , Yasemin Çaldiran Cumhuriyet University, Department of Chemistry, 58140 Sivas, Turkey e-mail: saraydin@cumhuriyet.edu.tr Received: 15 March 2000/Accepted: 18 December 2000 Summary Influence of some simulated physiological body fluids on the dynamic swelling behaviour of polyelectrolytic hydroxamic acid hydrogels (PHA) was investigated at 37 °C in vitro. The simulated physiological body fluids are distilled water, human sera, physiological saline (0.89 % NaCl), isoosmotic phosphate buffer at pH 7.4, gastric fluid at pH 1. 1, (gylicine-HCl buffer), urea (0-3 mol L -1 ), and the aquatic solutions of K 2 HPO 4 and KNO 3 (the sources of K + ). The values of equilibrium swelling of PHA hydrogels varied in the range of 130-4625%, while the values of equilibrium fluid content of the hydrogels varied in the range of 57-97%. The initial rate of swelling, diffusional exponent, and, diffusion coefficient were calculated using swelling kinetics data. Diffusion of the fluids into the hydrogel was found to be non- Fickian character. The diffusion coefficients of the hydrogel varied between 0.6x10 -6 - 8.1x10 -6 cm 2 s -1 . Introduction Polyelectrolyte hydrogels are highly swelling polymer networks. They possess many interesting properties. They may swell hundreds of times their initial volume or drastically reduce their size under the influence of external forces or in response to the changes in the surrounding media. This makes them a very interesting scientific object of observation and useful material for practical applications (1). Hydrogels have been extensively studied and used for a large number of applications in the medical field as implants, controlled drug release devices, for enzyme and cell immobilization, blood-contacting applications and other uses. A hydrogel can be defined as a polymeric material that is characterized by its capacity to absorb water, other solvents and biological fluids. The utility of hydrogels as biomaterials lies in the similarity of their physical properties with those of living tissues. This resemblance is based on their water content, soft and rubbery consistency and low interfacial tension with water and other biological fluids. So, from this viewpoint more hydrophilic hydrogels are better as implants, as long as their mechanical properties are acceptable (2).