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试剂高效地输送到淋巴系统。已知的是，间质注射的颗粒被带入初始淋巴管，并在区域淋巴结内积聚。然而，关于体内淋巴结内颗粒摄取和积聚的大小相关机制的信息很少。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摄取和积累的影响。雄性日本大耳白兔静脉注射氯胺酮(20 mg/kg)麻醉。戊巴比妥钠(20 mg/kg)静脉注射。逆行插管于其中一条月国窝传入淋巴管。将直径分别为0.5、1.1、2.0、5.6、10.0μm的荧光微球标记胶乳注入兔足背侧皮下。然后，通过测量微球颗粒u…的数量来确定微球在传出淋巴管中的浓度更多是在荧光显微镜下。在其他实验中，向心性和逆行插管分别在一条输入淋巴管和输出淋巴管中进行。所有其他传出淋巴管均完全结扎。将直径为0.5、1.1、1.7、1.9μm的荧光微球标记胶乳注入传入淋巴管。每次给药2微克，以1.47ml/h的恒速注入人工淋巴液，在荧光显微镜下测量微球在传出淋巴管中的数量，以确定微球的浓度变化。传入淋巴中颗粒浓度由大到小的顺序为：0.5μm&Gt；1.1μm&Gt；2.0μm-颗粒。传入淋巴中未见直径为5.6和10.0μm的颗粒。注射部位机械按摩后，淋巴流率和颗粒浓度均明显增加。在后一次实验中，0.5μm-微球在2.5h内有11.0±6.4%的微球通过了淋巴结。而传出淋巴中未见直径为1.9μm的微球。在淋巴结中的蓄积能力由大到小依次为1.9MGT、1.7MGT、1.1MGT、0.5M型微球(μm&GT)；1.9μm&GT；1.70μm&GT；0.5μm微球。这些结果有力地表明，微小和纳米颗粒从皮下组织向淋巴系统的运输存在大小和机械刺激依赖的机制，淋巴结内存在大小依赖的蓄积机制。较少

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