对映异构聚乳酸/聚乙二醇空间异构复合水凝胶的药物释放及形貌和细胞毒性

背景:目前生物降解水凝胶已被广泛应用于抗癌药物及生物活性大分子的装载,但为了保护生物活性大分子的活性,需要得到凝胶化条件更温和,凝胶化时间更短的凝胶体系.目的:制备对映异构聚乳酸∕聚乙二醇的空间异构复合水凝胶,使其具有更短的凝胶化时间,实现对模拟药物溶菌酶的装载和控释.方法:以聚乙二醇为引发剂,辛酸亚锡为催化剂,丙交酯与聚乙二醇发生开环聚合反应,得到聚乳酸/聚乙二醇的三嵌段共聚物(PLLA-PEG-PLLA 和 PDLA-PEG-PDLA).用1H NMR,FT-IR 和 XRD表征三嵌段共聚物.10% PLLA20-PEG227-PLLA20的水溶液和10%PDLA21-PEG227-PDLA21的水溶液在室温下混合,12 h后形成凝胶.通过XRD考察凝胶化机制,以溶菌酶为模拟药物,考察凝胶的释药特性,通过扫描电镜考察凝胶的形貌,采用MTT法考察凝胶的细胞毒性.结果与结论:成功得到聚乳酸/聚乙二醇的三嵌段共聚物,在嵌段共聚物中,聚乳酸嵌段和聚乙二醇嵌段都能结晶,但以聚乙二醇嵌段的结晶为主.通过XRD证明凝胶中存在空间异构复合作用,溶菌酶在凝胶中通过凝胶的溶蚀和降解行为,在7 d之内释放完全.通过扫描电镜观察到冻干的水凝胶呈三维贯穿的多孔结构,空隙尺寸在50~100 μm 之间.鼠成纤维细胞与浓度为100%的凝胶浸提液共培养72 h之后,细胞的存活率为99.3%.     

Failure of folic acid (pteroylglutamic acid) to affect hyperuricemia

PGA administered in doses up to 1000 mg orally a day did not significantly lower the serum urate concentration nor decrease the urinary urate or total oxypurine excretion in five hyperuricemic subjects. The folate was well absorbed, as reflected by marked increases in the serum and erythrocyte folate concentrations, and up to 50% of the administered folate could be recovered in the urine. There was no evidence of clinical or laboratory toxicity at these high doses of folate. PGA is a weak inhibitor of human liver xanthine oxidase in vitro, and much of its inhibitory effect is secondary to trace contamination by pterin-6-aldehyde, a potent inhibitor of the enzyme.     

Stability of insulin during the erosion of poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres.

In recent years, the acylation of peptides during the erosion of poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres has been described in the literature. To investigate whether insulin is prone to the covalent attachment of lactic or glycolic acid, insulin-loaded PLA and PLGA microspheres containing 5% bovine insulin were manufactured using a w/o/w multiple emulsion-solvent evaporation technique. Microspheres were characterized for their insulin encapsulation efficiency and release characteristics in phosphate-buffered saline (PBS) at pH 7.4 and 37 degrees C. Moreover, the stability of the peptide during 18 days of release was evaluated using HPLC and HPLC-MS techniques. The results showed that the insulin loading efficiencies of PLA and PLGA microspheres were 75.18% and 79.63%, respectively. The microspheres were spherical with relatively porous surfaces with an average diameter of 40 and 53 mum, respectively. Insulin release from the microspheres was characterized by an initial burst, which was attributed to the amount of protein located on or close to the microsphere surface. The total ion chromatogram (TIC) of insulin samples extracted after 18 days of erosion in phosphate buffer pH 7.4 at 37 degrees C revealed that deamidation was the major mechanism of instability. Surprisingly, no acylation products were found. Control experiments in concentrated lactic acid solutions confirmed a minimal reactivity of the peptide under these conditions.     

Tumor pH-responsive flower-like micelles of poly(l-lactic acid)-b-poly(ethylene glycol)-b-poly(l-histidine)

Polymeric micelles were constructed from poly(l-lactic acid) (PLA; M_n 3K)-b-poly(ethylene glycol) (PEG; M_n 2K)-b-poly(l-histidine) (polyHis; M_n 5K) as a tumor pH-specific anticancer drug carrier. Micelles (particle diameter: ∼ 80 nm; critical micelle concentration (CMC): 2 μg/ml) formed by dialysis of the polymer solution in dimethylsulfoxide (DMSO) against pH 8.0 aqueous solution, are assumed to have a flower-like assembly of PLA and polyHis blocks in the core and PEG block as the shell. The pH-sensitivity of the micelles originates from the deformation of the micellar core due to the ionization of polyHis at a slightly acidic pH. However, the co-presence of pH-insensitive lipophilic PLA block in the core prevented disintegration of the micelles and caused swelling/aggregation. A fluorescence probe study showed that the polarity of pyrene retained in the micelles increased as pH was decreased from 7.4 to 6.6, indicating a change to a more hydrophilic environment in the micelles. Considering that the size increased up to 580 nm at pH 6.6 from 80 nm at pH 7.4 and that the transmittance of micellar solution increased with decreasing pH, the micelles were not dissociated but rather swollen/aggregated. Interestingly, the subsequent decline of pyrene polarity below pH 6.6 suggested re-self-assembly of the block copolymers, most likely forming a PLA block core while polyHis block relocation to the surface. Consequently, these pH-dependent physical changes of the PLA-b-PEG-b-polyHis micelles provide a mechanism for triggered drug release from the micelles triggered by the small change in pH (pH 7.2–6.5).     

Identification of urinary metabolites of (+/-)-2-(p-isobutylphenyl)propionic acid (Ibuprofen) by routine organic acid screening.

Ibuprofen [(+/-)-2-(p-isobutylphenyl)propionic acid] has recently been introduced as a pediatric anti-inflammatory agent. To determine how this agent interferes with urine organic acid analysis, an important pediatric investigation, we have analyzed urine from two subjects pre- and post-Ibuprofen dosage and two subjects on chronic Ibuprofen therapy. A distinctive pattern of drug interference on the organic acid profile was detected. There were three major components, corresponding to unmetabolized Ibuprofen and to the oxidation products hydroxy Ibuprofen and carboxy Ibuprofen. Therefore, the major mechanism of Ibuprofen metabolism appears to be microsomal, although mitochondrial and peroxisomal routes cannot be excluded. Laboratories carrying out routine organic acid analysis should be aware of the nature and magnitude of the organic aciduria caused by Ibuprofen.     

Role of HCA(2) (GPR109A) in nicotinic acid and fumaric acid ester-induced effects on the skin

Traumatic brain injury (TBI) is a devastating neurological injury with broad manifestations. Unfortunately, its diagnosis and efficacious treatments remain elusive. Different post injury symptoms are exhibited at different time frames, indicative of a time-related progression of the pathology. Therefore, particular treatments must be tailored to the post injury time frame. This overview is focused on the secondary chronic phase following TBI and the value of sympathomimetic therapy during this phase. The various direct- and indirect-acting drugs are reviewed, and the treatment protocol employed by the author is described.     

Psychotic symptoms during phenibut (beta-phenyl-gamma-aminobutyric acid) withdrawal

Background: Phenibut is a GABAB agonist that was developed in the Soviet Union in the 1960s. In Russia, it is used in clinical practice to treat, for example, anxiety and alcohol withdrawal symptoms. In Europe and in the United States, phenibut is marketed as a nutritional supplement for improved sleep. In different Internet discussion forums, there are several reports of withdrawal symptoms. Aim: Our aim was to share what we have learnt from a case study wherein a patient was followed throughout the whole abstinence period.

Case report: A somatically healthy man in his mid-20s with a previous history of substance abuse took phenibut for 2 months. He noted tolerance development already after the first week and increased doses up to 20 g/day. Already a few hours after the last dose the patient started to experience subjective symptoms, at the third day of abstinence the patient started to hallucinate and the following day’s symptoms were aggravated with increased hallucinations and confusion. After treatment with benzodiazepines the psychosis resolved.

Conclusion: Phenibut withdrawal symptoms can become severe and have similarities to Baclofen, GHB, benzodiazepine and alcohol withdrawal. Benzodiazepines and supportive care seems to be the most effective choice of treatment for objective abstinence symptoms.     

聚乙丙交酯支架的细胞相容性特点

背景:聚乳酸及其衍生物具有良好的生物相容性、降解产物无毒性、易加工、具备一定强度等优点在骨组织工程中得到越来越广泛的应用。目的:观察骨髓基质干细胞与聚乙丙交酯类支架的细胞相容性及体外贴附情况,为制备负载多种细胞因子的聚乙丙交酯类支架提供研究基础。设计:对比观察。单位:南方医科大学南方医院创伤骨科。材料:实验于2004-09/2005-06在广东省组织构建与检测重点实验室完成。选择健康2月龄雄性新西兰兔1只。实验用主要材料:聚乙丙交酯支架(中山大学高分子研究所),β-磷酸三钙(瑞士AO公司)。方法:抽取新西兰兔骨髓,用全骨髓培养法获取单核细胞,经条件培养液体外诱导、扩增。骨髓基质干细胞以1×109L-1接种于聚乙丙交酯和β-磷酸三钙上,另设不加材料的空白对照组。通过倒置相差显微镜、扫描电镜观察细胞生长及细胞与材料的附着情况。以MTT法、流式细胞仪等手段检测各组细胞增殖和细胞周期变化情况。主要观察指标:①相差显微镜下每日定期观察细胞生长及与材料贴附情况。②培养1,3,6d扫描电镜下观察细胞生长情况。③MTT法检测细胞增殖情况。④采用化学比色法测定碱性磷酸酶活性。⑤流式细胞仪检测2种材料对骨髓基质干细胞的细胞周期、DNA含量及倍体水平的影响,并计算样品细胞的DNA指数。结果:①细胞培养后相差显微镜观察:空白对照组培养7～10d时细胞多呈梭形,未发现接触抑制现象。聚乙丙交酯组细胞开始贴壁时间明显晚于β-磷酸三钙组,随培养时间延长,细胞在材料周围与材料表面密集生长,细胞形态为多角形,两材料组细胞生长状态及细胞形态与空白对照组相似。②细胞培养后扫描电镜观察:空白对照组培养7d的细胞仍为单层并融合成片,但多角形细胞增多,细胞表面存在颗粒状物,细胞间以微丝相连。聚乙丙交酯组培养7d时,细胞数量大为增加,胞体扁平,跨越孔隙表面,形成细胞间连结,细胞连接成片,有大量基质形成。β-磷酸三钙组培养7d时,细胞数量增加,并相互连接,表面呈单层排列,可有细胞外基质形成,细胞长入孔隙内。③细胞增殖情况:随培养时间的延长各组细胞数量都有所增加,但聚乙丙交酯组与空白对照组及与β-磷酸三钙组间差异无显著性意义(P>0.05)。④碱性磷酸酶活性:随细胞培养时间延长,检测到各组细胞的碱性磷酸酶活性均增加,但聚乙丙交酯组与空白对照组及与β-磷酸三钙组间细胞碱性磷酸酶活性差异无显著性意义(P>0.05)。⑤细胞周期情况:两种材料对兔骨髓基质干细胞的细胞周期影响不大,各组细胞皆为正常的二倍体细胞,未见异倍体细胞形成。结论:聚乙丙交酯类支架的细胞相容性较好,并可进一步作为多种细胞因子载体构建缓释型支架用于骨组织工程。     

乳酸-羟基乙酸共聚物纳米粒的研究进展

乳酸-羟基乙酸共聚物是目前被认为最具发展前景的生物医用高分子可降解材料之一,对近年来乳酸-羟基乙酸共聚物纳米粒的制备方法和改性研究进行分析.目前制备乳酸-羟基乙酸共聚物纳米粒药物载体的方法主要有沉淀法、乳化溶剂挥发法、溶剂扩散法、喷雾干燥法等.乳酸-羟摹乙酸共聚物纳米粒的表面涂层、表面接枝、表面特异性配体修饰及与其他高聚物共聚、与无机物复合是改性研究的热点.乳酸-羟基乙酸共聚物纳米粒药物载体的制各技术和改性研究方法较多,但尚未完全解决临床应用上如何控制药物适量的突释,使血药浓度快速达到有效治疗浓度而不导致杀死正常细胞等一些问题,乳酸-羟基乙酸共聚物纳米粒系统有待进一步的完善.