摘要
随着药剂学的不断发展,传统的载药体系已经不能满足其需求。因此出现了许多新型的具有不同功能特性的药物载体。在本论文中,我们通过不同制备手段获得了几种药物控制释放的载体。
首先,我们制备了以疏水性聚乳酸-乙醇酸共聚物(PLGA)纳米颗粒为核,亲水性海藻酸为壳层的核-壳结构微球。选择人血清白蛋白(human serum albumin, HSA)和扑热息痛作为药物模型,分别被包埋在壳层和核层内。实验中,对于制备出的核-壳结构微球,我们使用扫描电子显微镜(Scanning electron microscope, SEM),光学显微镜(Optical microscopy, OM)和透射电子显微镜(Transmission electron microscope, TEM)表征微球的形貌和结构。实验结果直接证明了微球核-壳结构存在。随后的体外降解和药物释放实验中,我们得到了载药微球在药物释放过程中的降解特性和药物释放特性。因此,实验结果表明核-壳结构微球作为一种新型药物载体在一定程度上能实现了抑制内层药物突释现象和不同时间段的药物释放。
其次,在本实验中,选用含有不同聚乙二醇(Poly(ethylene glycol), PEG)比例的聚乳酸-聚乙二醇共聚物作为药物载体,并将荧光标记物异硫氰酸荧光素(Fluorescein isothiocyanate, FITC)包埋入微球中。主要采用扫描电子显微镜、原子力显微镜(Atomic force microscope, AFM)和激光粒度分析仪(Laser diffraction particle size analyzer, LDPSA)表征颗粒的粒径和形貌。本次实验选用小鼠成骨细胞来考察不同PEG含量和粒径的PELA颗粒的细胞毒性和吞噬情况。实验结果显示在同一粒径下,随着PELA中PEG比例的增加,成骨细胞对纳米颗粒的吞噬量在减少。
最后,我们通过模板法制备了可降解壳聚糖(Chitosan, CS)中空纳米颗粒,并对其药物释放特性以及细胞实验做了研究。实验中首先得到纳米核-壳结构颗粒,壳层主要利用改性后PELA表面的硫酸基团和壳聚糖的氨基基团的静电反应,采用层层自组装的方法在PELA模板上建立。然后加入戊二醛将壳聚糖交联固化,最后用溶剂除去PELA核层后即得到了CS中空纳米颗粒。实验中我们用TEM、SEM和AFM对PELA模板,CS-PELA核-壳结构纳米颗粒和中空纳米颗粒的结构进行表征。颗粒的平均粒径和粒径分布用动态激光散射仪(Dynamic light scattering, DLS)分析。此外,我们考察了携载阿霉素的中空纳米颗粒在磷酸缓冲溶液(Phosphate buffered solution, PBS, pH7.4)和醋酸缓冲溶液(Acetate buffered solution, ABS, pH 4.5)中的药物释放情况,并评价了其对肿瘤细胞生长抑制效果。
With the development of biopharmaceuticals, the traditional drug delivery systems have several inherent problems. So many new and advanced drug deliverys with different functions occurred. In the study, we investigated several biodegradable carriers for drug controlled release system by different fabrication methods.
Firstly, the core-shell biodegradable microspheres loading human serum albumin (HSA) and paracetamol were fabricated with a hydrophilic alginic acid (ALG) shell and a hydrophobic poly(D,L-lactide-co-glycolide) (PLGA) core. The two model drugs, HSA and paracetamol, were entrapped in the shell and core, respectively. These microspheres were characterized in terms of morphology, mean size and size distribution, drug loading efficiency, in vitro degradation and drugs release. The morphology of the microspheres was observed with scanning electron microscope (SEM), optical microscopy (OM) and transmission electron microscope (TEM). These photos revealed directly that the microspheres possessed core-shell structure. The degradation and drug release results showed that the microspheres have different feature on the degradation and drug release. The distinct double-walled structure of the microspheres would make an interesting device for exact controlled delivery of therapeutic agents at different stages.
Secondly, PELA copolymers with different weight ratios of polyethylene glycol (PEG) were used as drug carriers in the study. Fluorescein isothiocyanate (FITC) as a fluorescent marker were entrapped. The size and morphology of the particles were observed with scanning electron microscope (SEM), atomic force microscope (AFM) and laser diffraction particle size analyzer (LDPSA). The purpose of the present work was mainly to investigate the cytotoxicity and the process of endocytosis of PELA particles with different contents of PEG and variable particle size using rat osteoblasts (OBs). The endocytosis was observed through a light microscope and a fluorescence microscope, and moreover, their intracellular uptake and retention were determined quantitatively using fluorescence spectrophotometer (FSP). The results showed that with content of PEG in PELA increased, the endocytosis of nanoparticles in osteoblasts was to reduce.
Finally, biodegradable chitosan (CS) hollow nanospheres have been fabricated by employing uniform PELA nanoparticles as templates. The chitosan was adsorbed onto the surface of the PELA templates with layer by layer self-assemble method through the electrostatic interaction between the sulphuric acid groups (from SDS) on the templates and the amino groups on the chitosan. Subsequently, the core-coated structure of CS-PELA nanospheres was obtained with the adsorbed chitosan layer being crosslinked with glutaraldehyde. After the removal of the templates, PELA cores, CS hollow nanospheres were achieved. The morphology of the PELA templates, the CS-PELA core-coated nanospheres and the hollow CS nanospheres was characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The mean size and size distribution of these nanospheres were also measured with dynamic light scattering (DLS). The hollow structure was identified by TEM, AFM and laser confocal scanning microscope (LCSM). The antitumor drug model, adriamycin, was adsorbed on/into the CS hollow nanospheres. The drug release behaviors from the CS hollow nanospheres were investigated in phosphate buffered solution (PBS) at pH 7.4 and acetate buffered solution (ABS) at pH 4.5, respectively, at 37℃, and in vitro tumor cell growth inhibition assay was also evaluated. The results indicated that the biodegradable hollow nanospheres possess great potential applications in drug controlled release system.
引文
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