Development of drug delivery system (DDS) target for the lymphatic system

微米和纳米颗粒已被用于将药物和诊断剂有效递送至淋巴系统。已知间质给药的颗粒被吸收到初始淋巴结中并积聚在局部淋巴结中。然而，关于体内淋巴结中颗粒摄取和累积的尺寸依赖性机制的信息很少。因此，在这项研究中，我们试图评估大小对淋巴结中胶体颗粒的吸收和积累的影响。雄性日本白色家兔用氯胺酮（20 mg/kg iv.）戊巴比妥（20 mg/kg iv.）。在其中一条腘动脉输入淋巴管中进行逆行插管。将直径为0.5、1.1、2.0、5.6和10.0 μm的荧光微球标记乳胶注射于兔足背皮下。然后，通过测量微球在传出淋巴管中的颗粒数量来确定微球在传出淋巴管中的浓度。 关于我们 在荧光显微镜下观察。在其他实验中，分别在其中一条腘动脉传入和传出淋巴管中进行向心和逆行插管。所有其他传出神经均完全结扎。将直径分别为0.5、1.1、1.7和1.9 μm的荧光微球标记乳胶注射入输入淋巴管。每种颗粒一次给药2 μ g，并通过相同途径以1.47 ml/h的恒定速率注射人工淋巴液。然后，通过在荧光显微镜下测量颗粒的数量来确定传出淋巴管中微球的浓度变化。传入淋巴液中颗粒浓度的大小顺序为：0.5μm> 1.1μm >2.0 μ m颗粒。在传入淋巴中未观察到直径为5.6和10.0 μm的颗粒。当对注射部位进行机械按摩时，淋巴流量和颗粒浓度均显著增加。在后一实验中，11.0 ±6.4%的0.5 μ m微球在2.5h内通过淋巴结。而在输出淋巴中未观察到直径为1.9μm的微球。在淋巴结中蓄积能力的大小顺序为：1.9μm>1.7μm>1.1μm>0.5μ m微球。这些结果强烈表明，微米和纳米颗粒从皮下组织运输到淋巴系统中存在尺寸和机械刺激依赖性机制，并且淋巴结中存在尺寸依赖性积聚机制。少

Micro- and nano-particles have been used for efficient delivery of drugs and diagnostic agents to lymphatic system. Interstitially administered particles are known to be taken up into initial lymphatics and accumulate in the regional lymph nodes. Little information, however, exists regarding size-dependent mechanisms for the particle uptake and accumulation in the lymph nodes in vivo. Thus, in this study, we have attempted to evaluate effects of size on uptake and accumulation of colloidal particles in the lymph nodes. Male Japan White rabbits were anesthetized with ketamine (20 mg/kg iv.) and pentobarbital (20 mg/kg iv.). Retrograde cannulation was performed in one of the popliteal afferent lymph vessels. Labeled latex with fluorescence microspheres with 0.5, 1.1, 2.0, 5.6 and 10.0 μm in diameter were injected subcutaneously at dorsal portion of rabbit foot. Then, concentrations of the microspheres in the efferent lymph vessel were determined by measuring the number of the particles u … More nder a fluorescent microscope. In other experiments, centripetal and retrograde cannulations were performed in one of the popliteal afferent and efferent lymph vessels, respectively. All other efferent lymphatics were ligated completely. Labeled latex with fluorescence microspheres with 0.5, 1.1, 1.7 and 1.9 μm in diameter were injected into the afferent lymph vessel. Two microgram of each particle was administered at one time and artificial lymph fluid was injected through the same route at constant rate of 1.47 ml/h. Then, changes in concentration of the microspheres in the efferent lymph vessel were determined by measuring the number of the particles under a fluorescent microscope. The decreasing order of particle concentration in afferent lymph was as follows : 0.5μm> 1.1μm >2.0 μm-particle. No particle with 5.6 and 10.0 μm in diameter was observed in the afferent lymph. When mechanical massage was administered on the injection site, both lymph flow rate and particle concentration were markedly increased. In the latter experiments, 11.0 ±6.4% of the 0.5 μm-microsphere passed through the lymph node in 2.5h. On the other hand, no microsphere with 1.9μm in diameter was observed in the efferent lymph. The decreasing order of ability for accumulating in the lymph node was as follows : 1.9μm>1.7μm>1.1μm>0.5μm-microsphere. These results strongly suggest that size- and mechanical stimulation-dependent mechanisms exist in transport of micro- and nano-particles from subcutaneous tissue into the lymphatic system and that size-dependent accumulating mechanisms exist in the lymph node. Less