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聚酰胺-胺(polyamidoamine, PAMAM)型树枝状高分子纳米材料是以乙二胺为核,与丙烯酸甲酯通过麦克尔加成反应制备的支化大分子,以-CH2CH2-CONHCH2CH2N-为重复单元可以得到不同代数的PAMAM[1-2]。不同代数的PAMAM具有不同的几何尺寸和分子质量,与生物体内的生物大分子大小相当,有人称之为“人工蛋白”(artificial protein)[3]。随着树枝状聚合物代数的升高,其末端官能团数目成倍增加,并交替转化。因其大量的末端活性基团和可控的结构,自合成以来即在催化材料、生物医用材料、废水处理等领域得到广泛的应用,近年来,将PAMAM应用于药物载体[4-5]及非病毒基因载体[6]的报道大量出现。
虽然PAMAM作为药物载体具有很多优势,但是,作为一类新的纳米材料,PAMAM在体内的分布及代谢特性是否满足临床使用要求的研究却很少。本研究通过对PAMAM进行125I标记来研究其在小鼠体内的分布代谢规律,探讨PAMAM作为药物载体的可行性。
125I标记聚酰胺-胺及其在小鼠体内的生物分布
Labeling of polyamidoamine with 125I and its biodistribution in mice
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摘要:
目的 研究125I标记的树枝状高分子纳米材料聚酰胺-胺(PAMAM)在小鼠体内的生物分布。 方法 通过羟基琥珀酰亚胺将酪氨酸连接到4代PAMAM上,再对PAMAM进行125I标记,透析法对标记化合物进行纯化,放射性薄层扫描对标记物进行标记率、放化纯度及稳定性检测。将125I-PAMAM经尾静脉注射入小鼠体内,分别在1、4、8、24、48 h时对小鼠进行活体成像,并取主要脏器进行放射性计数。 结果 磁共振氢谱法检测结果显示,每个PAMAM分子上约连接了两个酪氨酸分子,标记率约为56%,放化纯度>98%,标记化合物具有良好的稳定性,体外放置72 h放化纯度仍>90%。小动物活体成像结果显示,PAMAM主要聚集在肝脏部位。各组织的放射性计数与显像结果基本一致,主要分布在肝、肾和脾中,而且体内代谢较慢,48 h时在小鼠体内仍有较高分布。 结论 未经修饰的PAMAM在肝、肾及脾中大量聚集,体内代谢缓慢,不适合直接作为药物载体进行使用,需进行化学修饰来加速体内代谢,防止体内蓄积从而引起不良反应。 Abstract:Objective To investigate the biodistribution of 125I labeled dendrimer nanomaterial—polyamidoamine (PAMAM) in mice. Methods Tyrosine was conjugated to four generation PAMAM by N-Hydroxysuccinimide, then 125I was labeled on PAMAM with chloramines-T method, and purified by dialysis. Labeling rate, radiochemical purity and stability of 125I-PAMAM were detected by radioactive thin layer chromatography scanning. The gamma imaging and biodistribution were detected by in vivo imaging system and gamma counter at one, four, eight, twenty-four and forty-eight hours after intravenous injection. Results The 1H nuclear magnetic resonance results showed that about two tyrosines were conjugated to PAMAM. The 125I labeling rate was about 56% and radiochemical purity was more than 98%. The radiochemical purity of labeled compound remained more than 90% at 72 hours in vitro. In vivo imaging results showed that PAMAM was mainly accumulated in liver periphery. The gamma counter results showed that PAMAM mainly accumulated in liver, kidney and spleen, the excretion of PAMAM was slow and there has high dose of PAMAM in mice at 48 hours. Conclusion PAMAM with no chemical modification was mainly accumulated in liver, kidney and spleen, and the excretion of PAMAM was slow, so PAMAM is not fit as drug carrier. PAMAM need to chemical modification to accelerate excretion and prevent the emergence of toxicity caused by accumulation in body. -
Key words:
- Iodine radioisotopes /
- Polyamidoamine /
- Body distribution
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