Clinical dextran purified by fractional ultrafiltration coupled with water washing

Dextran with extremely narrow molecular weight distribution (MWD) is demanded for clinical use. To elucidate the effect of fractional ultrafiltration on the purification of clinical dextran, a range of ultrafiltration membranes with 100, 30, 5 and 1 kDa molecular weight cut-off (MWCO) were applied. High Performance Gel Permeation Chromatography (HPGPC) analysis indicated that the MWD of ultrafiltrated dextran fractions are wide, with polydispersity index (D) between 2.2 and 5.4, suggesting that the MWD of dextran is hard to be strictly controlled by fractional ultrafitration. However, when coupled with water washing during ultrafiltration process, the homogeneity of dextran was greatly improved. An ultrafiltration fraction of 5–30 kDa (Mw ≈ 35 kDa) with narrow MWD (D = 1.2) was obtained after 5 times of water washing. The results show that fractional ultrafiltration coupled with water washing can be used as a simple and effective method to improve the quality of clinical dextran.