The effects of fixed electrical charge on chondrocyte behavior

In this study we have compared the effects of negative and positive fixed charges on chondrocyte behavior in vitro Electrical charges have been incorporated into oligo(poly(ethylene glycol) fumarate) (OPF) using small charged monomers such as sodium methacrylate (SMA) and (2-(methacryloyloxy) ethyl)trimethyl ammonium chloride (MAETAC) to produce negatively and positively charged hydrogels, respectively The physical and electrical properties of the hydrogels were characterized by measuring and calculating the swelling ratio and zeta potential, respectively Our results revealed that the properties of these OH modified hydrogels varied according to the concentration of charged monomers Zeta potential measurements demonstrated that the electrical properties of the OFF hydrogel surfaces changed on incorporation of SMA and MAETAC and that these changes in electrical properties were dose-dependent Attenuated total reflectance Fourier transform infrared spectroscopy was used to determine the hydrogel surface composition To assess the effects of surface properties on chondrocyte behavior primary chondrocytes isolated from rabbit ears were seeded as a monolayer on top of the hydrogels We demonstrated that the cells remained viable over 7 days and began to proliferate while seeded on top of the hydrogels Collagen type II staining was positive in all samples, however, the staining intensity was higher on negatively charged hydrogels Similarly, glycosammoglycan production was significantly higher on negatively charged hydrogels compared with a neutral hydrogel Reverse transcriptase polymerase chain reaction showed up-regulation of collagen type II and down-regulation of collagen type I on the negatively charged hydrogels These findings indicate that charge plays an important role in establishing an appropriate environment for chondrocytes and, hence, in the engineering of cartilage Thus, further investigations into charged hydrogels for cartilage tissue engineering is merited (C) 2011 Published by Elsevier Ltd on behalf of Acta Materialia Inc