Ultrasonic degradation of aqueous dextran: effect of initial molecular weight and concentration.

Seven dextrans with different initial molecular weight (IMW) were depolymerized by ultrasonic treatment. The effects of IMW in a wide range from 9.3×10(3) Da to 1.7×10(6) Da and solution concentration (1, 10 and 20 mg/mL) on dextran degradation were investigated. Changes in weight-average molecular weight (Mw) and polydispersity index (D value) were monitored as a function of ultrasonic time. Results showed that Mw and D value decreased with increasing time of ultrasonic treatment. Moreover, the degradation proceeded faster for higher IMW dextrans and more dilute solutions, yielding lower molecular weight dextrans and more homologous solutions. Percentage variation of dextran fragments at different molecular weight divisions showed that most of the degradation took place in larger molecular weight fragments. Ultrasonic treatment is a simple and controllable method for producing dextrans with low molecular weight, which are more suitable for clinical use.