Reyes-Ortega Felisa, Rodríguez Gema, Aguilar María Rosa, Lord Megan, Whitelock John, Stenzel Martina H, San Román Julio
Biomaterials Group, Institute of Polymer Science and Technology (ICTP-CSIC), Spain and Networking Biomedical Research Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Juan de la Cierva 3, 28006 Madrid, Spain.
J Mater Chem B. 2013 Feb 14;1(6):850-860. doi: 10.1039/c2tb00194b. Epub 2012 Dec 13.
Bemiparin (fractionated low molecular weight heparin)-loaded nanoparticles were prepared by two consecutive w/o emulsions and an inversion to an o/w emulsion for various polymer systems as controlled release formulations. New synthetic block copolymers, poly(methyl methacrylate-b-trimethyl aminoethyl methacrylate) (PMMA-b-PMAETMA), with controlled microstructure and molecular weight, were prepared by RAFT (Reversible Addition-Fragmentation chain-Transfer) polymerization creating a set of polymers with different amounts of cationic charges. For comparison, a non-biodegradable positively charged polymer, Eudragit® RS PO, and a biodegradable polymer poly(lactic-co-glycolic acid), PLGA, were used. The microstructural arrangement of MMA and MAETMA sequences in PMMA-b-PMAETMA results in self-assembled core-shell nanoparticles in water with a positively charged surface, which interacts with bemiparin. The formulations were evaluated in terms of particle size, zeta potential and morphology by scanning electron microscopy (SEM). The entrapment of bemiparin molecules was confirmed by a negatively increased zeta potential value and the detection of a sulfur signal by energy dispersive X-ray spectroscopy (EDAX). High encapsulation efficiency was reached with all the polymeric matrices, ranging from 89 to 98%. Systems prepared with synthetic block copolymers PMMA-b-PMAETMA and PLGA showed higher in vitro bemiparin release than Eudragit® RS PO systems. For each formulation, bemiparin released from nanoparticles preserved its biological activity as shown by the BaF32 cell proliferation assay in the presence of fibroblast growth factor (FGF2).
通过连续两次油包水乳液以及向水包油乳液的转变，制备了负载贝米肝素（低分子肝素片段）的纳米颗粒，用于各种聚合物体系作为控释制剂。通过可逆加成-断裂链转移（RAFT）聚合制备了具有可控微观结构和分子量的新型合成嵌段共聚物聚（甲基丙烯酸甲酯-b-甲基丙烯酸三甲基氨基乙酯）（PMMA-b-PMAETMA），从而得到了一组带有不同数量阳离子电荷的聚合物。作为比较，使用了一种不可生物降解的带正电荷聚合物Eudragit® RS PO和一种可生物降解的聚合物聚乳酸-乙醇酸共聚物（PLGA）。PMMA-b-PMAETMA中MMA和MAETMA序列的微观结构排列导致在水中形成自组装的核壳纳米颗粒，其表面带正电荷，可与贝米肝素相互作用。通过扫描电子显微镜（SEM）对制剂的粒径、zeta电位和形态进行了评估。贝米肝素分子的包封通过zeta电位值的负向增加以及能量色散X射线光谱（EDAX）对硫信号的检测得以证实。所有聚合物基质的包封效率都很高，范围在89%至98%之间。用合成嵌段共聚物PMMA-b-PMAETMA和PLGA制备的体系在体外显示出比Eudragit® RS PO体系更高的贝米肝素释放量。对于每种制剂，从纳米颗粒释放的贝米肝素保留了其生物活性，这在成纤维细胞生长因子（FGF2）存在的情况下通过BaF32细胞增殖试验得以证明。
