Zhang Xiaojun, Chen Dawei, Ba Shuang, Chang Jing, Zhou Jiaying, Zhao Haixia, Zhu Jia, Zhao Xiuli, Hu Haiyang, Qiao Mingxi
School of Pharmacy, Shenyang Pharmaceutical University, P.O. Box 42, Wenhua Road 103, Shenyang, Liaoning Province 110016, PR China.
School of Pharmacy, Shenyang Pharmaceutical University, P.O. Box 42, Wenhua Road 103, Shenyang, Liaoning Province 110016, PR China.
Colloids Surf B Biointerfaces. 2016 Apr 1;140:176-184. doi: 10.1016/j.colsurfb.2015.12.032. Epub 2015 Dec 23.
Even though the Poly(l-histidine) (PHis) based copolymers have been well studied, the effect of the chemically substituted l-histidine on the physio-chemical and biological properties of the micelles has never been elucidated to date. To address this issue, triblock copolymer of poly(ethylene glycol)-poly(D,L-lactide)-poly(2,4-dinitrophenol-L-histidine)(mPEG-b-PLA-b-DNP-PHis) with DNP group substituted to the saturated nitrogen of l-histidine were synthesized. The pH sensitive properties of the copolymer micelles were characterized using an acid-base titration method, fluorescene probe technique, DLS observation, in vitro drug release and cytotoxicity against MCF-7 cells under different pH conditions, respectively. The results suggest that mPEG-b-PLA-b-DNP-PHis copolymers showed similar micellar stability for DOX loaded micelles, increased particle size, and similar pH responsive properties with mPEG-b-PLA-b-PHis copolymers. The subcellular distribution observation demonstrated that mPEG-b-PLA-b-DNP-PHis micelles showed a slightly compromised endo-lysosmal escape of doxorubicin as compared to mPEG-b-PLA-b-PHis micelles. The mPEG-b-PLA-b-DNP-PHis micelles showed higher cellular uptake by MCF-7 cells than mPEG-b-PLA-b-PHis micelles due to the different uptake pathways. Effect of DNP substitution on the in vivo distribution of the copolymer micelles was studied using non-invasive near-infrared fluorescence (NIRF) imaging with mPEG-b-PLA-b-PHis micelles as control. The results indicate that the mPEG-b-PLA-b-DNP-PHis micelles showed a reduced passive targeting to the tumor due to the larger particle size. These results suggest that saturated nitrogen of PHis may serve as a valuable site for chemical modification of the PHis based copolymers because of the little effect on the pH responsive properties. However, selection of the substitution group needs to be considered due to the possible increase of micellar particle size of the micelles, leading to compromised passive targeting.
尽管基于聚（L-组氨酸）（PHis）的共聚物已得到充分研究，但化学取代的L-组氨酸对胶束的物理化学和生物学性质的影响至今尚未阐明。为了解决这个问题，合成了聚乙二醇-聚（D，L-丙交酯）-聚（2,4-二硝基苯酚-L-组氨酸）（mPEG-b-PLA-b-DNP-PHis）三嵌段共聚物，其中DNP基团取代了L-组氨酸的饱和氮。分别采用酸碱滴定法、荧光探针技术、动态光散射观察、体外药物释放以及在不同pH条件下对MCF-7细胞的细胞毒性来表征共聚物胶束的pH敏感性质。结果表明，mPEG-b-PLA-b-DNP-PHis共聚物对载有阿霉素的胶束表现出相似的胶束稳定性、粒径增大，并且与mPEG-b-PLA-b-PHis共聚物具有相似的pH响应性质。亚细胞分布观察表明，与mPEG-b-PLA-b-PHis胶束相比，mPEG-b-PLA-b-DNP-PHis胶束中阿霉素的内吞溶酶体逃逸略有受损。由于摄取途径不同，mPEG-b-PLA-b-DNP-PHis胶束比mPEG-b-PLA-b-PHis胶束显示出更高的MCF-7细胞摄取率。以mPEG-b-PLA-b-PHis胶束为对照，采用非侵入性近红外荧光（NIRF）成像研究了DNP取代对共聚物胶束体内分布的影响。结果表明，由于粒径较大，mPEG-b-PLA-b-DNP-PHis胶束对肿瘤的被动靶向性降低。这些结果表明，由于对pH响应性质影响较小，PHis的饱和氮可能是基于PHis的共聚物化学修饰的一个有价值的位点。然而，由于胶束粒径可能增加，导致被动靶向性受损，因此需要考虑取代基团的选择。
