静脉注射羧基化单壁碳纳米管在大鼠腋窝淋巴结的积聚

Accumulation of intravenously injected carboxylated single-walled carbon nanotubes in rat axillary lymph nodes

背景:基于碳纳米管的淋巴靶向示踪和治疗是肿瘤靶向诊疗的研究热点之一,评价碳纳米管对腋窝淋巴结的聚集作用,能够为开发淋巴特异性更高、生物兼容性更好的纳米示踪剂和药物载体提供实验依据。目的:观察静脉注射羧基化单壁碳纳米管在SD大鼠腋窝淋巴结的积聚作用,并评价其对血液细胞的影响。方法:将64只SD大鼠随机均分为两组,实验组尾静脉注射羧基化单壁碳纳米管2 mg/kg,空白对照组尾静脉注射5%葡萄糖溶液1 m L/kg,3次/周,设定7,60,90,120 d(120 d为给药90 d后停药30 d)共4个周期,每个周期结束时每组随机抽取8只大鼠,采集腹主动脉血液进行血常规检测,观察腋窝淋巴结变化,采集实验组120 d淋巴结标本进行透射电子显微镜观测。结果与结论:与空白对照组相比,实验组7 d的腋窝淋巴结无明显黑染;随着给药周期的增加,实验组大鼠淋巴结肿大、质地变硬、黑染加深,伴随血液中性粒细胞百分数显著升高(P<0.01或P<0.001);停药30 d后,腋窝淋巴结缩小、黑染局部褪去,中性粒细胞百分数下降。停药30 d后,透射电子显微镜观测证实实验组大量羧基化单壁碳纳米管被淋巴细胞吞噬,形成大量吞噬泡。表明尾静脉注射羧基化单壁碳纳米管对SD大鼠腋窝淋巴结的短期靶向示踪作用较弱,长期静脉注射会逐渐在大鼠腋窝淋巴结形成积聚,并引起中性粒细胞增多;停止给药后,羧基化单壁碳纳米管能够被淋巴结缓慢清除。

BACKGROUND： Lymph-targeted tracing and therapy based on carbon nanotubes have been one of the hottest researches on targeting tumor diagnosis and treatment. To evaluate the accumulation of carbon nanotubes in axillary lymph node can provide experimental evidences for developing nano-tracers and drug carriers which are more lymph-specific and more biocompatible. OBJECTIVE： To study the accumulation of the intravenously injected carboxylated single-walled carbon nanotubes in axillary lymph nodes of Sprague-Dawley rats, and to evaluate their effect on blood cells. METHODS： Sixty-four Sprague-Dawley rats were randomly divided into two groups. Rats in testing group were injected with carboxylated single-walled carbon nanotubes suspension（2 mg/kg）, while those in control group were injected with 5% glucose solution（1 m L/kg）, both through the tail vein, three times per week. Four periods of 7, 60, 90 and 120 days were set（the 120-day period referred to 90 days of administration followed by 30 days ofdrug withdrawal）. At the end of each period, eight rats from each group were randomly picked out, to collect blood samples via the abdominal aorta for blood routine test. Finally the axillary lymph nodes were observed, and the lymph node samples of rats in the testing group were collected and analyzed at 120 days by transmission electron microscope. RESULTS AND CONCLUSION： Compared with the control group, black staining of axillary lymph nodes of rats in testing group was not obvious at the end of the 7-day period. However, with the increase of the dosing periods, the lymph nodes of the rats in the testing group became enlarged, firm and black stained, coupled with a significant rising in the percentage of blood neutrophils. After 30 days of drug withdrawal, the size of the rat axillary lymph nodes was reduced and black staining partly faded, with the decreasing of blood neutrophil percentage. Under the transmission electron microscope, abundant carboxylated single-walled carbon nanotubes were uptaken by lymphocytes to form a large number of phagocytic vacuoles after drug withdrawal for 30 days. It indicates that the short-term tracing of rat axillary lymph nodes by carboxylated single-walled carbon nanotubes injected through the tail vein is relatively weak, while the long-term intravenous injection can cause their accumulation in rat axillary lymph nodes, coupled with the increase of neutrophils; after drug withdrawal, the carboxylated single-walled carbon nanotubes can be slowly cleared by the lymph nodes.