Rheological and Biological Characteristics of Hyalu-ronic Acid Derivative Modified by Polyethylene Glycol

Hyaluronic acid （HA） was chemically modified by polyethylene glycol. Meanwhile, the dynamic mechanics properties of HA derivative and its viscoelastic changes were measured on 3ARES3 Rheometer （Japan） at 25℃. Dried cross-linked films of 10- 10 mm^2 were immersed in phosphate buffered saline（PBS： pH 7.4） at 37 ℃ with different time periods to measure its water content and in vitro degradation. Moreover, cell cultured solutions, which were in the different cultivation vesse with 1 mg/mL Solution of HA derivative as doing experimental sample for 2 d, 4 d and 7 d, were observed, respectively, by an inverted discrepancy microscope. The cell relative growth rate was analyzed with the SPSS10.0 mathematic statistic software. Based on the above experiments, structure-modified HA derivative can meet the requirements of biomaterials in view of rheological and degradation in vitro and cytotoxicity charactereistics from clinical medical aspect under this experiment conditions.

Characteristics of Hyaluronic Acid Derivative Cross-linked by Polyethylene Glycol

Characteristic and dynamic viscosities of Hyaluronic acid （ HA ） derivative modified by polyethylene glycol （PEG） were tested with different reaction times （6 h,12 h,18 h and 24 h ）, different molar ratio of HA/PEG （1/10,1/5,1/3 and 1/2）, different molecular weight of PEG（400,6 000 and 20 000） and mass fraction is 0. 4% by Wushi Viscosimeter and L-90 Rheometer at 25℃ . Characteristic viscosity of HA derivative had the largest value in 12 h, which decreased with increasing of PEG molecular weight, bat its aqueous dynamic viscosity increased with increment of PEG molecular weight. Meanwhile, we tested dynamic mechanic properties of HA derivative by 3ARES3 Rheometer at 25℃ to study viscoelastic changes and to compare change difference from viscosity to elasticity with the changes of vibration frequency between unmodified HA and HA derivative. Change from low vibrated freqnency to high one of solution resulted in change from viscosity to elasticity of solution. In conclusion, as to the rheological properties, structure- modified HA derivative meets the requirement of biomaterial .

Characteristic of hyaluronic acid derivative films cross-linked by polyethylene glycol of low water content

Objective:To test the characteristics of hyaluronic acid(HA)derivative cross-linked by polyethylene glycol films of low water content.Methods:The cross-linked HA film with 200μm thickness was got at atmospheric pressure at 25℃for 5 d.After dried,cross-linked films of 10 mm×10 mm were weighed and immersed in phosphate buffered saline (PBS pH 7.45)at 37℃for 24 h.Then the solution fraction and water content were estimated.Meanwhile,cross-linked HA derivative films were immersed in phosphate buffered saline(PBS:pH 7.45)at 37℃for determined time and then implanted subcutaneously in the back of white rats to test in vitro or in vivo degradation characteristic.Results and Conclusion:HA hydrogel cross-linked by polyethylene glycol with water content is as low as 60% and this kind of HA derivative has a slow degradation rate.