Bioerodable Ketamine-Loaded Microparticles Fabricated Using Dissolvable Hydrogel Template Technology

For severe cancer-related pain that is not relieved adequately by escalating doses of oral or parenterally administered strong opioid analgesics such as morphine, alone or in combination with an adjuvant drug such as ketamine, more invasive dosing routes may be warranted. One such approach involves surgical implantation of an intrathecal pump to deliver small doses of analgesic or adjuvant drugs in close proximity to the receptors that transduce their pain-relieving effects. However, the use of implanted devices is associated with a range of catheter-related problems. To address this, we have developed biodegradable microparticles loaded with the analgesic adjuvant drug, ketamine, for sustained release after a single bolus intrathecal injection. Drug-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles were prepared using a dissolvable hydrogel template. Using PLGA with 3 different ratios of lactic acid to glycolic acid (L/G), relatively high ketamine loading and homogenous particle shape and size were achieved. Specifically, ketamine loading of PLGA5050, PLGA7525, and PLGA8515 in ester-terminated microparticles was 20.0%, 20.4%, and 18.9%, respectively. The microparticles were within the desired size range (20 μm diameter and 30 μm height) and in vitro release was sustained for ≥14 days with an acceptable initial burst release (～10%-20%) achieved.     

Time course study of the antigen-specific immune response to a PLGA microparticle vaccine formulation

Microparticle-based vaccine delivery systems are known to promote enhanced immune responses to protein antigens and can elicit T_H1-biased responses when used in combination with Toll-like receptor (TLR) agonists. It is important to understand the kinetics of the immune responses to microparticle-based protein vaccines in order to predict the duration of protective immunity and to optimize prime-boost vaccination regimens. We carried out a 10-week time course study to investigate the magnitude and kinetics of the antibody and cellular immune responses to poly(lactic-co-glycolic acid) (PLGA) microparticles containing 40 μg ovalbumin (OVA) protein and 16 μg CpG-ODN adjuvant (MP/OVA/CpG) in comparison to OVA-containing microparticles, soluble OVA plus CpG, or OVA formulated with Alhydrogel^® aluminum adjuvant. Mice vaccinated with MP/OVA/CpG developed the highest T_H1-associated IgG2b and IgG2c antibody titers, while also eliciting T_H2-associated IgG1 antibody titers on par with Alhydrogel^®-formulated OVA, with all IgG subtype titers peaking at day 56. The MP/OVA/CpG vaccine also induced the highest antigen-specific splenocyte IFN-γ responses, with high levels of IFN-γ responses persisting until day 42. Thus the MP/OVA/CpG formulation produced a sustained and heightened humoral and cellular immune response, with an overall T_H1 bias, while maintaining high levels of IgG1 antibody equivalent to that seen with Alhydrogel^® adjuvant. The time course kinetics study provides a useful baseline for designing vaccination regimens for microparticle-based protein vaccines.     

Pharmacodynamics and pharmacokinetics of PLGA-based doxorubicin-loaded implants for tumor therapy

The traditional systemic chemotherapy through intravenous infusion of doxorubicin (DOX) has many side effects. The aim of this study was to develop a PLGA-based DOX-loaded implant and to evaluate the efficacy and drug metabolism distribution of the implant in intratumoral chemotherapy for osteosarcoma (OS). In this study, implants containing DOX, poly(d,l-lactide-co-glycolide), and polyethylene glycol 4000 were prepared by melt-molding method. Then, the antitumor activity and systemic drug distribution of the implants were tested in a K7M2 OS bearing mouse model. The scanning electron microscope images showed that DOX was uniformly dispersed in the polymer matrix. Both the in vitro and in vivo release profiles of implants are characterized by three-phase release. Implantation of DOX-loaded implants into tumors can inhibit tumor growth in a dose-dependent manner. The pharmacokinetic behavior shows that intratumor chemotherapy through implants has a much higher drug concentration in tumors than in normal tissues, which may be the reason for improving antitumor activity and reducing systemic side effects. In summary, the drug release of the implants prepared in this study is sustained and stable, which promotes long-term local accumulation of drugs in tumors, improves the efficacy of chemotherapy and has low toxicity to normal tissues.     

Directional Growth of cm-Long PLGA Nanofibers by a Simple and Fast Wet-Processing Method

The development of aligned nanofibers as useful scaffolds for tissue engineering is an actively sought-for research objective. Here, we propose a novel improvement of an existing self-assembly-based nanofabrication technique (ASB-SANS). This improvement, which we termed Directional ASB-SANS, allows one to produce cm²-large domains of highly aligned poly(lactic-co-glycolic acid) (PLGA) nanofibers in a rapid, inexpensive, and easy way. The so-grown aligned PLGA nanofibers exhibited remarkable adhesion to different substrates (glass, polyimide, and Si/SiOx), even when immersed in PBS solution and kept at physiological temperature (37 °C) for up to two weeks. Finally, the Directional ASB-SANS technique allowed us to grow PLGA fibers also on highly heterogeneous substrates such as polyimide-based, gold-coated flexible electrodes. These results suggest the viability of Directional ASB-SANS method for realizing biocompatible/bioresorbable, nanostructured coatings, potentially suitable for neural interface systems.     

Control of neonatal human dermal fibroblast migration on poly(lactic‐co‐glycolic acid)‐coated surfaces by electrotaxis

Many types of cells respond to applied direct current electric fields (dcEFs) by directional cell migration, a phenomenon called galvanotaxis or electrotaxis. In this study, electrotaxis was used to control cell migration. We designed a new electrotaxis incubator and chamber system to facilitate long‐term (> 12 h) observation and to allow for alterations to the direction of the current. Poly(lactic‐co‐glycolic acid) (PLGA) was coated onto surfaces to mimic a commonly used tissue‐engineering scaffolding environment. Neonatal human dermal fibroblasts (nHDFs) were grown on PLGA‐coated surfaces and exposed to EFs at increasing currents in the range 0–1 V/cm. These cells migrated toward the cathode during 3 h of dcEF stimulation; however, the migration speed decreased with increasing electric fields. Cells exposed to dcEFs in the range 1–2 V/cm showed no changes to migration speed or x forward migration indices (xFMIs) and the cells continued to move toward the cathode. nHDFs showed directional migration towards the cathode in direct current (dc) EFs (1 V/cm) and they moved in the opposite direction when the polarity of the dcEF was reversed. Reorganization of the actin cytoskeleton and polarization of the Golgi apparatus were evaluated by immunostaining, which showed that the actin cytoskeleton elongated towards the cathode and the Golgi apparatus polarized in the direction of the dcEF. This study revealed that cell migration could potentially be controlled on PLGA scaffolds through electrotaxis. Copyright © 2015 John Wiley & Sons, Ltd.     

BCNU缓释微球制备条件的优化

目的以溶剂挥发-萃取法制备卡氮芥-聚乳酸羟基乙酸(BCNU-PLGA)缓释微球,对微球制备过程中的工艺条件进行优化选择。方法以正交实验设计对可能的影响因素,包括不同聚合度的聚乙烯醇(PVA)、PVA浓度、PLGA浓度、搅拌速度、甲基纤维素(MC)浓度进行了探讨。结果发现影响微球质量的因素,顺序从大到小依次为:PVA浓度、PLGA浓度、搅拌时间和MC浓度(A-B-D-C)。最佳实验方案为A2B1C2D3,即分散介质PVA浓度为1.5%,有机相中PLGA浓度为2%,搅拌时间为60min,MC浓度为0.05%。结论正交实验设计方法有助于选择更合适的制备条件。     

地高辛-PLGA抗肿瘤纳米粒子的制备及其抗肿瘤活性的初步研究

目的 制备载地高辛的聚乳酸-羟基乙酸共聚物(PLGA)纳米粒子,提高地高辛的生物利用度,降低其毒副作用.方法 建立测定地高辛-PLGA纳米粒子载药量和包封率的高效液相色谱法;采用乳化溶剂挥发法制备地高辛-PLGA纳米粒子,并通过单因素实验优化制备条件;采用噻唑蓝法评价地高辛和地高辛-PLGA纳米粒子的抗肿瘤能力.结果 以粒径为筛选条件的单因素实验结果表明,制备地高辛-PLGA纳米粒子的最佳条件为PLGA 30 mg,地高辛2 mg,二氯甲烷3 ml,聚乙烯醇质量分数0.5％,超声功率200 W.此制备条件下得到的地高辛-PLGA纳米粒子的粒径约231 nm,包封率为74.61％,载药量为5.37％,且其抗肿瘤活性优于地高辛,差异具有统计学意义(P＜0.05).结论 以PLGA为载体材料制备地高辛-PLGA纳米粒子可增强地高辛的抗肿瘤作用.     

PLGA为佐剂的OVA纳米疫苗皮下注射可预防小鼠过敏反应性气道炎症和调节Thl/Th2反应

目的 探讨聚乳酸.羟基乙酸共聚物[poly(D,L-lactic-co-glycolic)acid,PLGA]包裹的卵清蛋白(OVA)纳米癌苗(POM)对哮喘小鼠的免疫治疗效果.方法 包裹不同剂量(低、中、高)的OVA纳米粒子和对照(OVA、空白纳米粒子、PBS)通过皮下注射给予小鼠,再用OVA进行致敏和激发,通过肺组织学、支气管肺泡灌洗液(BALF)细胞计数、测定BALF和脾细胞培养上清液中细胞因子的含量,观察小鼠呼吸道炎症和免疫学改变.结果 肺部组织学和BALF中细胞计数结果显示,与PBS对照组相比,OVA治疗组、中剂量和高剂量OVA纳米组的肺部嗜酸性浸润显著减轻,BALF中总细胞和嗜酸性细胞显著减少.卸胞因子测定结果显示,与PBS对照组相比,中、高剂量OVA纳米组的BALF和脾细胞培养上清液中IFN-γ显著升高,Ⅱ,4水平显著降低.OVA治疗组中IL-4水平显著下降,而IFN-γ水平无显著差异.结论 OVA纳米疫苗可预防哮喘嗜酸性气道炎症,其可能的机制之一是调节了过敏性哮喘的Th1/Th2失平衡反应.