Abstract:Low degree of polymerization (DP) and narrow molecular weight distribution chitosan (LNCS6) (DP=6, Mw/Mn = 1.08) was prepared with the method of microwave-assisted oxidative degradation. It was used as a carrier molecular to link 7-hydroxyl-8-formylcoumarin (CA) as the fluorescence emission group, diethylenetriaminepentaacetic acid (DTPA) as complex of gadolinium ions to get the final product Gd[DTPA/CA-LNCS6] as an potential magnetic resonance (MR) /fluorescence bifunctional imaging molecular probe. The magnetic resonance imaging (MRI) efficiency and fluorescence properties were studied, and the binding constants and thermodynamic parameters between Gd[DTPA/CA-LNCS6] and bovine serum albumin (BSA) were measured by isothermal titration calorimetry (ITC). The results showed that Gd[DTPA/CA-LNCS6] exhibited higher MRI relaxation 〔r1=13.71 L/(mmol ∙ s)〕, which was well above the clinically used Magnevist 〔r1=3.63 L/(mmol ∙ s)〕; Meanwhile, the product had significant fluorescence characteristics at 438nm, and the binding constants between Gd[DTPA/CA-LNCS6] and BSA was over 104 which was suitable for blood transportation. This work has good reference for the synthesis of probes like such type of fine chemical.