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

微粒子和纳米粒子已被用于淋巴系统药物和诊断试剂的有效输送。已知间质给药颗粒被吸收到初始淋巴管中并在区域淋巴结中积聚。然而，关于颗粒在体内淋巴结吸收和积累的大小依赖机制的信息很少。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。用氯胺酮（20mg /kg）和戊巴比妥（20mg /kg）麻醉雄性日本大白兔。在其中一条腘窝传入淋巴管中行逆行插管。分别在兔足背皮下注射直径为0.5、1.1、2.0、5.6和10.0 μm的荧光微球标记乳胶。然后，在荧光显微镜下通过测量微球颗粒的数量来确定微球在传出淋巴管中的浓度。在其他实验中，分别在腘动脉的一条传入和传出淋巴管中进行向心和逆行插管。所有其他传出淋巴管完全结扎。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到传入淋巴管中。每次给药各2微克，并以1.47 ml/h的恒定速率注射人工淋巴液。然后，在荧光显微镜下通过测量微球颗粒的数量来确定微球在传出淋巴管中的浓度变化。传入淋巴颗粒浓度的递减顺序为：0.5μm> ~ 1.1μm > ~ 2.0 μm-particle。传入淋巴未见直径为5.6和10.0 μm的颗粒。在注射部位进行机械按摩时，淋巴流速和颗粒浓度均明显增加。在后一组实验中，0.5 μm微球在2.5h内通过淋巴结的比例为11.0±6.4%。另一方面，传出淋巴未见直径1.9μm的微球。其在淋巴结内的积聚能力由大到小依次为：1.9μm>1.7μm>1.1μm>0.5μm微球。这些结果强烈表明，微观和纳米颗粒从皮下组织转运到淋巴系统存在大小和机械刺激依赖机制，淋巴结中存在大小依赖的积累机制。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