一种磁共振造影剂前体BSA-(Gd-DTPA)_n的制备、表征及体内外评价

目的:改进BSA-(Gd-DTPA)_n制备及纯化方法,探讨其作为磁共振造影剂前体的优势及应用前景.方法:BSA与二乙烯三胺五乙酸环酐反应生成BSA-(DTPA)_n,并与GdCb螯合生成BSA-(Gd-DTPA)_n.紫外光谱法鉴定其结构,并定量测定其中DTPA对BSA的偶联率.测定配合物体外弛豫时间T_1、T_2,分析其弛豫性能R1、R2.小鼠急性毒性试验评价药物安全性.大鼠磁共振增强扫描评价其活体内代谢及分布情况.结果:本研究制得的BSA-(Gd-DTPA)n配合物中n=26.体外弛豫性能RI约为7.00×10~(-3) L·mmol~(-1)·ms~(-1).比小分子Gd-DTPA的弛豫性能(3.52×10~(-3) L·mmol~(-1)·ms~(-1))提高近1倍.大鼠磁共振增强扫描显示BSA-(Gd-DTPA)-n和白蛋白一样具有长循环特性.结论:本实验改进方法可制备出磁共振造影剂前体BSA-(Gd-DTPA)_n,该配合物具备长循环特性,且具有多个可供修饰的氨基,可作为一种潜在的磁共振造影剂前体.

Synthesis, Characterization and Evaluation of BSA - (Gd - DTPA)_n as a MRI Contrast Agent Precursor

Purpose: To improve the synthesis and purification methods of BSA - (Gd - DTPA)_n, and to explore its advantages and application prospect as a high - performance relaxation magnetic resonance imaging agent precursor. Methods: Bovine serum albumin (BSA) reacted with diethylenetriamine pen-taacetic acid cyclic anhydride (DTPACA) under the condition pH = 9, and produced the conjugate BSA -(DTPA)_n, GdCl_3 was further chelated to the conjugate to produce BSA- (Gd- DTPA)_n. BSA- (Gd - DT-PA)_n was characterized and identified by UV spectroscopy . The coupling ratio of DTPA and BSA was quantitatively determined by ICP/AES. The relaxation rates of R1/R2 were further analyzed by measur-ing the relaxation time T_1/ T_2 of the complex in vitro. The drug safety was evaluated by acute toxicity test. The preliminary evaluation of its metabolism and distributions in vivo was done by magnetic reso-nance multi - phase enhanced scanning for multi - organs in rats. Results: In the obtained complex BSA -(Gd-DTPA)_n, n = 26. The relaxation property R1 in vitro was about 7.00×10~(-3) L·mmol~(-1)·ms~(-1) at 0.5T in 32℃, about twice of the relaxation property of the small - molecule Gd - DTPA(3.52×10~(-3) L· mmol~(-1)·ms~(-1)). The enhanced MRI scans in SD rats showed that vessels were obviously enhanced at the same time that the renal pelvis already bad been filled by the contrast agent. This indicated that BSA-(Gd - DTPA)_n had notable long - circulating characteristic as albumin, and this was conducive to its fully integration with the targeted lesions and displaying the vessels.Conclusion: The high relaxation per-formance magnetic resonance contrast agent precursor BSA - (Gd- DTPA)_n can be prepared and purified by the improved methods in this experiment, it has notable long - circulating characteristic, and has many amino - groups for modification, so it can be used as a potential MRI targeting contrast agent pre-cursor.