生物降解型尼索地平微球的研究

目的制备尼索地平的PLGA微球,并研究其体内外释药行为.方法采用溶剂挥发法制备微球,电镜下观察微球形态,HPLC法测定微球的载药量、包封率及累积释药量.采用HPLC法测定家兔体内的血药浓度.结果微球形态圆整,表面光滑.微球的粒径为15.3±3.8μm,载药量为21.16%,包封率为85.40%.微球的体外释药行为的拟合方程为1-Q=0.7654(1-t/t     

多肽、蛋白质药物的聚乳酸及其共聚物微球研究进展

综述了以可生物降解的合成高分子材料-聚乳酸及其共聚物为载体的多肽，蛋白质药物微球的制备方法和影响因素。讨论了蛋白质在制备和释放过程中的稳定性。     

尼索地平微球的制备

采用溶剂挥发法制备了尼索地平微球 ,考察了制备工艺中影响微球质量的 5个主要因素 ,筛选出较理想的处方和工艺。所得微球形态圆整 ,表面光滑 ,粒径 (18.2± 3.8) μm,载药量 2 1.2 % ,包封率 85 .4 %。     

雌二醇聚乳酸类微囊的制备与体外评价

目的　以聚乳酸或乳酸 乙醇酸共聚物为载体材料制备雌二醇缓释微囊。方法　实验中采用乳化 溶剂萃取法制备微囊 ,考察了影响微囊特性以及体外释药的各种因素 ,采用单因素试验方差分析进行因素影响的显著性检验 ,并在此基础上采用T方法进行两两间多重比较 ,进一步考察因素各水平间差异的显著性。结果　结果表明 ,粒径和加水萃取速度对雌二醇微囊的包封率有显著性影响 (P <0 0 1) ;随油相载体的浓度以及加水萃取速度对微囊的粒径影响显著 (P <0 0 1)。体外释药研究表明 ,加水萃取速度和载体的型号和分子量对微囊释药影响显著 (P <0 0 1)。但这些影响因素的各水平之间的差异性并不都具有显著性。结论　通过改变处方以及制备工艺可以得到具有不同性质的雌二醇聚乳酸类缓释微囊     

海藻酸-壳聚糖-聚乳酸羟乙醇酸复合微球的制备及其对蛋白释放的调节

目的制备蛋白的海藻酸-壳聚糖-聚乳酸羟乙醇酸(PLGA)复合微球，以增加蛋白药物的包封率、减少突释和不完全释放。方法以牛血清白蛋白为模型药物采用修饰的乳化、醇洗法制备小粒径海藻酸微囊，再以壳聚糖孵育制得海藻酸-壳聚糖双层微囊，并进一步用PLGA包裹制得复合微球。采用微量BCA试剂盒测定蛋白浓度，考察其包封率及释放行为，改变各种制备因素调节微球的释放特性。结果复合微球粒径约30 μm，形态圆整。与单纯PLGA微球相比，包封率由60%-70%上升至80%以上。复合微球在磷酸盐缓冲液的1 h突释量由40%-50%下降至25%以下，在生理盐水中则进一步下降至5%以下。结论海藻酸-壳聚糖-PLGA复合微球提高了蛋白药物的包封率，减少了药物的突释，并可通过调节PLGA比例调节药物的释放。     

In vivo biocompatibility of the PLGA microparticles in parotid gland

Poly(lactic-co-glycolic acid) (PLGA) microparticles are used in various disorders for the controlled or sustained release of drugs, with the management of salivary gland pathologies possible using this technology. There is no record of the response to such microparticles in the glandular parenchyma. The purpose of this study was to assess the morphological changes in the parotid gland when injected with a single dose of PLGA microparticles. We used 12 adult female Sprague Dawley rats (Rattus norvegicus) that were injected into their right parotid gland with sterile vehicle solution (G1, n=4), 0.5 mg PLGA microparticles (G2, n=4), and 0.75 mg PLGA microparticles (G3, n=4); the microparticles were dissolved in a sterile vehicle solution. The intercalar and striated ducts lumen, the thickness of the acini and the histology aspect in terms of the parenchyma organization, cell morphology of acini and duct system, the presence of polymeric residues, and inflammatory response were determined at 14 days post-injection. The administration of the compound in a single dose modified some of the morphometric parameters of parenchyma (intercalar duct lumen and thickness of the glandular acini) but did not induce tissue inflammatory response, despite the visible presence of polymer waste. This suggests that PLGA microparticles are biocompatible with the parotid tissue, making it possible to use intraglandular controlled drug administration.     

Investigation of the stabilizer elimination during the washing step of charged PLGA microparticles utilizing a novel HPLC-UV-ELSD method

Quantification of stabilizer content in microparticles and other products is of great importance for formulation development, drug product quality control as well as for reproducible manufacturing. A fast and sensitive HPLC method with evaporative light scattering detection (ELSD) capable of detecting docusate sodium (DOSS), poly (lactic-co-glycolic acid) (PLGA; Resomer RG 503 H) and R-1,2-dioleoyloxy-3-trimethylammonium-propane (DOTAP) in a single run was successfully developed. In contrast to previously described methods, hydrolysis of PLGA as pretreatment is not necessary, thereby enabling accurate quantification of stabilizer next to the intact matrix polymer.This method was used to investigate the impact of washing procedures of polymeric microparticles manufactured either with anionic stabilizer DOSS or with cationic stabilizer DOTAP. High amounts of DOSS were detected in the washing water. This finding was consistent with the result that no DOSS could be detected in the washed and dried microparticles (<limit of detection).In contrast, DOTAP was hardly measurable in the washing water during all washing cycles. However, DOTAP could be quantified in dried particles. The ratio of DOTAP to dry particle mass was approximately 1:10.This is most probably due to the different polymer surfactant interactions (e.g. charge) and the different hydrophilicity of the stabilizers used.     

In vivo pain relief effectiveness of an analgesic-anesthetic carrying biodegradable controlled release rod systems

Pain is the most common and feared symptom for patients, especially those with cancer. Treatment of chronic pain with conventional ways of medication usually fails with increasing severity of the pain. New approaches enabling the prolonged provision of pain relievers are required. We designed a controlled release system of pain relievers, mainly for opioids (morphine, M, codeine, C, and hydromorphone, HM), and a local anesthetic (bupivacaine, BP) in the form of poly(L-lactide-coglycolide) (PLGA) rods. The efficacy of these rods implanted alone or in combination in relieving chronic pain in rats caused by the ligation of the sciatic nerve of their right hind limbs was studied. The two most common tests for measuring analgesia, i.e. tail-flick tests, that show analgesia at sites other than the site of injury, were used to study the degree of systemic distribution of the drugs and paw-withdrawal tests were used to study the analgesia at the site of injury. Alleviation of this chronic and severe neuropathic pain could be obtained for about 3-4 days when rods for two drugs, 'dual drug' (analgesic-anesthetic), were used. This duration is decreased by half (2 days) with the single-drug rods. Also the dual-drug rods, though at half the dose of each single drug application, enhanced the degree of analgesia of the first day. These in vivo results are also consistent with the previous in vitro results as in the case with codeine which had a higher first-day analgesia than morphine, despite a lower potency due to the faster in vitro release rate. Similarly, slower release of hydromorphone from PLGA (85 :15) rods resulted in less systemic analgesia than the more rapidly eroding PLGA (50 : 50) rods of the same drug.     

Development of a single-dose recombinant CAMP factor entrapping poly(lactide-co-glycolide) microspheres-based vaccine against Streptococcus agalactiae

Streptococcus agalactiae is an important contagious bovine mastitis pathogen. Although it is well controlled and even eradicated in most Northern European and North American dairy herds, the prevalence of this pathogen remains very high in China. However, research on development of a vaccine against S. agalactiae mastitis is scarce. The aims of the present study were to: (1) develop a single-dose vaccine against S. agalactiae based on poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) encapsulated CAMP factor, a conserved virulent protein encoded by S. agalactiae’s cfb gene; and (2) evaluate its immunogenicity and protective efficacy in a mouse model. The cfb gene was cloned and expressed in a recombinant Escherichia coli strain Trans1-T1. The CAMP factor was tested to determine a safe dose range and then encapsulated in MS of PLGA (50:50) to assess its release pattern in vitro and immune reaction in vivo. Furthermore, a mouse model and a histopathological assay were developed to evaluate bacterial burden and vaccine efficacy. In the low dosage range (<100 μg), CAMP factor had no obvious toxicity in mice. The release pattern in vitro was characterized by an initial burst release (44%), followed by a sustained and slower release over 7 wk. In mice immunized with either pure CAMP factor protein or PLGA-CAMP, increased antibody titers were detected in the first 2 wk, whereas only PLGA-CAMP immunization induced a sustained increase of antibody titers. In mice vaccinated with PLGA-CAMP, mortality and bacteria counts were lower (compared to a control group) after S. agalactiae challenge. Additionally, no pathological lesions were detected in the vaccinated group. Therefore, PLGA-CAMP conferred protective efficacy against S. agalactiae in our mouse model, indicating its potential as a vaccine against S. agalactiae mastitis. Furthermore, the slow-release kinetics of PLGA MS warranted optimism for development of a single-dose vaccine.     

Sequentially releasing dual-drug-loaded PLGA–casein core/shell nanomedicine: Design,synthesis, biocompatibility and pharmacokinetics

The present study reports an engineered poly-l-lactide-co-glycolic acid (PLGA)–casein polymer–protein hybrid nanocarrier 190 ± 12 nm in size entrapping a combination of chemically distinct (hydrophobic/hydrophilic) model drugs. A simple emulsion–precipitation route was adopted to prepare nearly monodispersed nanoparticles with distinct core/shell morphology entrapping paclitaxel (Ptx) in the core and epigallocatechin gallate (EGCG) in the shell, with the intention of providing a sequential and sustained release of these drugs. The idea was that an early release of EGCG would substantially increase the sensitivity of Ptx to cancer, thereby providing improved therapeutics at lower concentrations, with less toxicity. The hemo- and immunocompatibility of the core/shell nanomedicine was established in this study. The core/shell nanoparticles injected via the tail vein in Sprague–Dawley rats did not reveal any organ toxicity as was evident from histopathological evaluations of the major organs. In vivo pharmacokinetic studies in rats by high-performance liquid chromatography confirmed a sustained and sequential release of both the drugs in plasma, indicating prolonged circulation of the nanomedicine and enhanced availability of the drugs when compared to the bare drugs. Overall, the polymer–protein multilayered nanoparticles proved to be a promising platform for nanopolypharmaceutics.