Desai M P, Labhasetwar V, Walter E, Levy R J, Amidon G L
College of Pharmacy, University of Michigan, Ann Arbor 48109, USA.
Pharm Res. 1997 Nov;14(11):1568-73. doi: 10.1023/a:1012126301290.
To study the uptake of biodegradable microparticles in Caco-2 cells.
Biodegradable microparticles of polylactic polyglycolic acid co-polymer (PLGA 50:50) of mean diameters 0.1 micron, 1 micron, and 10 microns containing bovine serum albumin as a model protein and 6-coumarin as a fluorescent marker were formulated by a multiple emulsion technique. The Caco-2 cell monolayers were incubated with each diameter microparticles (100 micrograms/ml) for two hours. The microparticle uptake in Caco-2 cells was studied by confocal microscopy and also by quantitating the 6-coumarin content of the microparticles taken up by the cells. The effects of microparticle concentration, and incubation time and temperature on microparticle cell uptake were also studied.
The study demonstrated that the Caco-2 cell microparticle uptake significantly depends upon the microparticle diameter. The 0.1 micron diameter microparticles had 2.5 fold greater uptake on the weight basis than the 1 micron and 6 fold greater than the 10 microns diameter microparticles. Similarly in terms of number the uptake of 0.1 micron diameter microparticles was 2.7 x 10(3) fold greater than the 1 micron and 6.7 x 10(6) greater than the 10 microns diameter microparticles. The efficiency of uptake of 0.1 micron diameter microparticles at 100 micrograms/ml concentration was 41% compared to 15% and 6% for the 1 micron and the 10 microns diameter microparticles, respectively. The Caco-2 cell microparticle (0.1 micron) uptake increased with concentration in the range of 100 micrograms/ml to 500 micrograms/ml which then reached a plateau at higher concentration. The uptake of microparticles increased with incubation time, reaching a steady state at two hours. The uptake was greater at an incubation temperature of 37 degrees C compared to at 4 degrees C.
The Caco-2 cell microparticle uptake was microparticle diameter, concentration, and incubation time and temperature dependent. The small diameter microparticles (0.1 micron) had significantly greater uptake compared to larger diameter microparticles. The results thus suggest that the mechanism of uptake of microparticles in Caco-2 cell is particle diameter dependent. Caco-2 cells are used as an in vitro model for gastrointestinal uptake, and therefore the results obtained in these studies could be of significant importance in optimizing the microparticle-based oral drug delivery systems.
研究可生物降解微粒在Caco-2细胞中的摄取情况。
采用复乳技术制备平均直径为0.1微米、1微米和10微米的聚乳酸-羟基乙酸共聚物（PLGA 50:50）可生物降解微粒，其中含有牛血清白蛋白作为模型蛋白以及6-香豆素作为荧光标记物。将Caco-2细胞单层与每种直径的微粒（100微克/毫升）孵育两小时。通过共聚焦显微镜研究Caco-2细胞对微粒的摄取情况，并通过定量细胞摄取的微粒中6-香豆素的含量进行研究。还研究了微粒浓度、孵育时间和温度对微粒细胞摄取的影响。
研究表明，Caco-2细胞对微粒的摄取显著取决于微粒直径。按重量计算，直径为0.1微米的微粒摄取量比1微米的微粒高2.5倍，比10微米的微粒高6倍。同样，就数量而言，直径为0.1微米的微粒摄取量比1微米的微粒高2.7×10³倍，比10微米的微粒高6.7×10⁶倍。在100微克/毫升浓度下，直径为0.1微米的微粒摄取效率为41%，而直径为1微米和10微米的微粒摄取效率分别为15%和6%。Caco-2细胞对微粒（0.1微米）的摄取在100微克/毫升至500微克/毫升范围内随浓度增加而增加，在更高浓度时达到平台期。微粒摄取量随孵育时间增加，在两小时时达到稳态。与4℃相比，在37℃孵育温度下摄取量更大。
Caco-2细胞对微粒的摄取取决于微粒直径、浓度、孵育时间和温度。与较大直径的微粒相比，小直径微粒（0.1微米）的摄取量显著更高。因此，结果表明Caco-2细胞中微粒的摄取机制取决于粒径。Caco-2细胞用作胃肠道摄取的体外模型，因此这些研究中获得的结果对于优化基于微粒的口服药物递送系统可能具有重要意义。
