Xie Yunchang, Jiang Sifan, Xia Fei, Hu Xiongwei, He Haisheng, Yin Zongning, Qi Jianping, Lu Yi, Wu Wei
School of Pharmacy, Fudan University, Key Laboratory of Smart Drug Delivery of MOE and PLA, Shanghai 201203, China.
J Mater Chem B. 2016 Jun 14;4(22):4040-4048. doi: 10.1039/c6tb00237d. Epub 2016 Apr 25.
Although glucan microparticles (GMs) can be efficiently taken up and transported by M cells, their subsequent accumulation in lymphatic tissues of sub-follicle-associated epithelia (FAE) in Peyer's patches might present a barrier to the oral delivery of insulin by GMs into the systemic circulation. The goal of this study is to weigh the potential of GMs as carriers for oral delivery of systemic therapeutics using insulin (INS) as a model drug. INS is encapsulated into the inner cavities of GMs by repeated soaking in INS solution at acidic pH values and switching to an isoelectric pH of 5.6 to precipitate INS. To immobilize INS, a thermosensitive poloxamer 407 (P407) gel is introduced into the interior of GMs. Interiorly thickened GMs show significantly decreased in vitro release and well protected INS stability against enzyme-enriched media, highlighting the importance of thickening with P407 gels. A mild and prolonged hypoglycaemic effect is achieved in both normal and diabetic rats for a duration of at least 20 h with pharmacological bioavailability as high as about 9-10%. Lymphatic transportation of GMs is investigated by labelling with a near-infrared water-quenching fluorescent probe in a conscious mesentery lymphatic duct cannulation rat model following oral administration. GMs appear in lymph within the first 2 h, peak at around 6 h and slow down after 10 h with a cumulative amount of over 8% in 24 h. The high correlation between lymphatic transportation and pharmacological bioavailability implies that GMs are principally absorbed via the lymphatic route. An in vitro study on phagocytosis by macrophages confirms the easy and fast uptake of GMs by J774A.1 cell lines with as many as over 10 particles within the cytoplasm of a single cell. Intracellular pharmacokinetics indicates robustness and persistent residence of GMs within the cells. Little effect on cell viability and tight junctions was observed in Caco-2 cell models. It is concluded that GMs are mainly absorbed via the lymphatic route and show potential as carriers for oral delivery of labile therapeutics, though with limited bioavailability due to the sub-FAE residence barriers.
尽管葡聚糖微粒（GMs）能够被M细胞有效摄取和转运，但其随后在派尔集合淋巴结中滤泡相关上皮（FAE）亚区的淋巴组织中的蓄积，可能会成为GMs将胰岛素经口服递送至体循环的障碍。本研究的目的是评估GMs作为全身治疗药物口服递送载体的潜力，以胰岛素（INS）作为模型药物。通过在酸性pH值下将GMs反复浸泡于INS溶液中，然后切换至等电点pH值5.6使INS沉淀，从而将INS包封于GMs的内腔中。为了固定INS，将热敏性泊洛沙姆407（P407）凝胶引入GMs的内部。内部增厚的GMs在体外释放显著降低，并且对INS在富含酶的介质中的稳定性具有良好的保护作用，突出了用P407凝胶增厚的重要性。在正常大鼠和糖尿病大鼠中均实现了温和且持久的降血糖作用，持续时间至少为20小时，药理生物利用度高达约9 - 10%。在清醒状态下进行肠系膜淋巴管插管的大鼠模型中，通过用近红外水猝灭荧光探针标记来研究GMs的淋巴转运。口服给药后，GMs在最初2小时内出现在淋巴中，在约6小时达到峰值，10小时后减缓，24小时内累积量超过8%。淋巴转运与药理生物利用度之间的高度相关性表明GMs主要通过淋巴途径吸收。对巨噬细胞吞噬作用的体外研究证实J774A.1细胞系能够轻松快速地摄取GMs，单个细胞的细胞质内有多达10个以上的颗粒。细胞内药代动力学表明GMs在细胞内具有稳健性和持久性。在Caco - 2细胞模型中未观察到对细胞活力和紧密连接有显著影响。结论是，GMs主要通过淋巴途径吸收，并且显示出作为口服递送不稳定治疗药物载体的潜力，尽管由于FAE亚区的滞留障碍，生物利用度有限。
