Sustained-Release Delivery of Octreotide from Biodegradable Polymeric Microspheres

The study reports on the drug release behavior of a potent synthetic somatostatin analogue, octreotide acetate, from biocompatible and biodegradable microspheres composed of poly-lactic-co-glycolic acid (PLGA) following a single intramuscular depot injection. The serum octreotide levels of three Oakwood Laboratories formulations and one Sandostatin LAR^® formulation were compared. Three formulations of octreotide acetate-loaded PLGA microspheres were prepared by a solvent extraction and evaporation procedure using PLGA polymers with different molecular weights. The in vivo drug release study was conducted in male Sprague–Dawley rats. Blood samples were taken at predetermined time points for up to 70 days. Drug serum concentrations were quantified using a radioimmunoassay procedure consisting of radiolabeled octreotide. The three octreotide PLGA microsphere formulations and Sandostatin LAR^® all showed a two-phase drug release profile (i.e., bimodal). The peak serum drug concentration of octreotide was reached in 30 min for all formulations followed by a decline after 6 h. Following this initial burst and decline, a second-release phase occurred after 3 days. This second-release phase exhibited sustained-release behavior, as the drug serum levels were discernible between days 7 and 42. Using pharmacokinetic computer simulations, it was estimated that the steady-state octreotide serum drug levels would be predicted to fall in the range of 40–130 pg/10 μL and 20–100 pg/10 μL following repeat dosing of the Oakwood formulations and Sandostatin LAR^® every 28 days and every 42 days at a dose of 3 mg/rat, respectively.     

Design of Methylprednisolone Biodegradable Microspheres Intended for Intra-articular Administration

This study aimed to design methyprednisolone (MP)-loaded poly(d,l lactide-co-glycolide) (PLGA) microspheres (MS) intended for intra-articular administration. MP was encapsulated in four different types of PLGA by using an S/O/W technique. The effects of β-irradiation at the dose of 25 kGy were evaluated on the chemical and physicochemical properties of MS and the drug release profiles. The S/O/W technique with hydroxypropylmethylcellulose (HPMC) as surfactant allowed obtaining MS in the tolerability size (7–50 μm) for intra-articular administration. The MP encapsulation efficiency ranged 56–60%. HPMC traces were evidenced in the loaded and placebo MS by attenuated total reflectance Fourier transform infrared spectroscopy. MS made of the capped PLGA DL5050 2M (MS 2M) and uncapped PLGA DL5050 3A (MS 3A) prolonged the release of MP over a 2- to 3-month period with a triphasic (burst release–dormant period–second release pulse) and biphasic release pattern, respectively. The β-irradiation did not significantly alter the morphology, chemical, and physicochemical properties of MS. The only variation was evidenced in the drug release for MS 2M in term of shorting of the dormant period. The minimal variations in the properties of irradiated PLGA MS, which are in disagreement with literature data, may be attributed to a radioprotecting effect exerted by HPMC.     

生物可降解微球作为HPV-E7蛋白免疫佐剂的研究

目的：对聚乳酸聚羟基乙酸（PGLA）作为疫苗运输载体进行免疫学评价。方法：用复乳法制备PLGA微球,通过表面吸附人乳头状瘤病毒（HPV）E7蛋白制备成聚乳酸聚羟基乙酸（PGLA）微球,考察粒径分布情况及体外释放水平,通过皮下免疫注射途径免疫C57BL/6小鼠,用间接ELISA法检测免疫鼠血清中的抗体水平,由此评价PLGA微球疫苗运输载体的佐剂效应。。结果：复乳法制备的PLGA微球表面光滑,大小均匀,包封率20.1%,注射小鼠6周后（第2周加强免疫1次）,微球疫苗诱导产生的IgG1抗体水平较同剂量的铝佐剂组和溴化二甲基双十八胺（DDA）组明显升高,（平均滴度分别为3805、1270、2262）;微球疫苗诱导产生IgG2b的抗体水平明显高于铝佐剂组,略低于DDA组,（平均滴度分别为1131、475、2653）而IgG2c的抗体量高于铝佐剂组和DDA组（平均滴度分别为150、36、106）。结论：人乳头状瘤病毒E7蛋白聚乳酸羟基乙酸微球作为疫苗输送体系可以明显的提高抗原的免疫原性。     

生物可降解微球作为HPV-E7 蛋白免疫佐剂的研究

目的:对聚乳酸聚羟基乙酸(PGLA)作为疫苗运输载体进行免疫学评价。方法:用复乳法制备PLGA微球,通过表面吸附人乳头状瘤病毒(HPV)E7蛋白制备成聚乳酸聚羟基乙酸(PGLA)微球,考察粒径分布情况及体外释放水平,通过皮下免疫注射途径免疫C57BL/6小鼠,用间接ELISA法检测免疫鼠血清中的抗体水平,由此评价PLGA微球疫苗运输载体的佐剂效应。。结果:复乳法制备的PLGA微球表面光滑,大小均匀,包封率20.1%,注射小鼠6周后(第2周加强免疫1次),微球疫苗诱导产生的IgG1抗体水平较同剂量的铝佐剂组和溴化二甲基双十八胺(DDA)组明显升高,(平均滴度分别为3805、1270、2262);微球疫苗诱导产生IgG2b的抗体水平明显高于铝佐剂组,略低于DDA组,(平均滴度分别为1131、475、2653)而IgG2c的抗体量高于铝佐剂组和DDA组(平均滴度分别为150、36、106)。结论:人乳头状瘤病毒E7蛋白聚乳酸羟基乙酸微球作为疫苗输送体系可以明显的提高抗原的免疫原性。     

A Short Term Quality Control Tool for Biodegradable Microspheres

Accelerated in vitro release testing methodology has been developed as an indicator of product performance to be used as a discriminatory quality control (QC) technique for the release of clinical and commercial batches of biodegradable microspheres. While product performance of biodegradable microspheres can be verified by in vivo and/or in vitro experiments, such evaluation can be particularly challenging because of slow polymer degradation, resulting in extended study times, labor, and expense. Three batches of Leuprolide poly(lactic-co-glycolic acid) (PLGA) microspheres having varying morphology (process variants having different particle size and specific surface area) were manufactured by the solvent extraction/evaporation technique. Tests involving in vitro release, polymer degradation and hydration of the microspheres were performed on the three batches at 55°C. In vitro peptide release at 55°C was analyzed using a previously derived modification of the Weibull function termed the modified Weibull equation (MWE). Experimental observations and data analysis confirm excellent reproducibility studies within and between batches of the microsphere formulations demonstrating the predictability of the accelerated experiments at 55°C. The accelerated test method was also successfully able to distinguish the in vitro product performance between the three batches having varying morphology (process variants), indicating that it is a suitable QC tool to discriminate product or process variants in clinical or commercial batches of microspheres. Additionally, data analysis utilized the MWE to further quantify the differences obtained from the accelerated in vitro product performance test between process variants, thereby enhancing the discriminatory power of the accelerated methodology at 55°C.     

左旋多巴甲酯在PLGA微球的稳定性研究

目的：考察左旋多巴甲酯在PLGA微球中的稳定性并探讨其稳定方法。方法：利用HPLC的方法考察了左旋多巴甲酯在不同pH值和光照的环境中和微球里的稳定性。结果：左旋多巴甲酯在pH3中稳定,在微球中也可以稳定一周。结论：包封左旋多巴甲酯在PLGA微球中,是一种有效地保护了左旋多巴甲酯在微球中的活性,可以实现长效缓释,是一种可行的方案。     

利用生物可降解海藻酸钙微球保护苏云金杆菌晶体与芽胞免受紫外线降解

采用基于注射挤压器的液滴形成技术制备包裹了苏云金杆菌晶体和芽胞的海藻酸钙凝胶微球.通过调节该装置的活塞重量和空气压力,获得了平均直径为20μm的微球.SDS-PAGE分析与平板菌落涂布实验表明,凝胶微球可有效减少紫外线对苏云金杆菌晶体和芽胞的损伤作用.利用小菜蛾进行的毒力生测发现,凝胶微球可有效防止紫外线引起的晶体和芽胞杀虫毒力的下降.本研究的液滴形成技术也可适用于其它微球包裹过程.     

Controlled Release of Dutasteride from Biodegradable Microspheres: In Vitro and In Vivo Studies

The aim of the present work was to study the in vitro/in vivo characteristics of dutasteride loaded biodegradable microspheres designed for sustained release of dutasteride over four weeks. An O/W emulsion-solvent evaporation method was used to incorporate dutasteride, which is of interest in the treatment of benign prostatic hyperplasia (BPH), into poly(lactide-co-glycolide) (PLGA). A response surface method (RSM) with central composite design (CCD) was employed to optimize the formulation variables. A prolonged in vitro drug release profile was observed, with a complete release of the entrapped drug within 28 days. The pharmacokinetics study showed sustained plasma drug concentration-time profile of dutasteride loaded microspheres after subcutaneous injection into rats. The in vitro drug release in rats correlated well with the in vivo pharmacokinetics profile. The pharmacodynamics evaluated by determination of the BPH inhibition in the rat models also showed a prolonged pharmacological response. These results suggest the potential use of dutasteride loaded biodegradable microspheres for the management of BPH over long periods.     

大肠杆菌微球包封效率及稳定性的研究

多聚物制备而成的微球是一种具有佐剂效应的疫苗控释系统,在疫苗研制中得到广泛应用.为改进大肠杆菌疫苗的制备质量,本文以天然高分子聚合物海藻酸钠和壳聚糖为材料,应用了三种不同制备微球的方法来制备大肠杆菌微球,观察微球的形态、粒径和稳定性,并测算其对大肠杆菌的包封率.结果表明,采用乳化-内部凝胶化法制备的大肠杆菌海藻酸钙-壳聚糖微球,圆整规则,粒径较小,包封率达到≈93.1％,具有良好的控释性能和稳定性,适于低温保存.     

PGLA编织支架的制备与初步体内评价

目的:热拉伸会改变纤维的结构和性能,进而影响由纤维编织而成的支架的性能。本文考察了PGLA纤维的拉伸倍数对编织支架在SD大鼠皮下的体内降解行为的影响。方法:制备了基于生物可降解高分子材料聚乙交酯丙交酯(PGLA,GA/LA摩尔比=90/10)的完全生物可降解编织支架,通过测试支架在大鼠体内降解过程中的失重、表面形貌、热性能、径向压缩力等变化情况,考察了纤维的不同的拉伸倍数对支架体内降解过程的影响。结果:用拉伸倍数为5的PGLA纤维编织的支架在植入SD大鼠皮下后降解最慢,重量、吸水率、结晶度、化学成分和径向压缩力的变化最慢,植入体内10天后能够保持完整的支架形态。结论:纤维的拉伸倍数会影响由纤维编织成的支架的热性能和力学性能的变化,本研究结果表明这种新的手工编织的支架具有短暂支撑管腔狭窄的潜在应用,为支架的材料选择和制备方法提供了参考,为在体内起到短暂支撑作用的支架的深入研究提供了实验基础。     

Evaluation of Ionotropic Cross-Linked Chitosan/Gelatin B Microspheres of Tramadol Hydrochloride

Microspheres of tramadol hydrochloride (TM) for oral delivery were prepared by complex coacervation method without the use of chemical cross-linking agents such as glutaraldehyde to avoid the toxic reactions and other undesirable effects of the chemical cross-linking agents. Alternatively, ionotropic gelation was employed by using sodium-tripolyphosphate as cross-linking agent. Chitosan and gelatin B were used as polymer and copolymer, respectively. All the prepared microspheres were subjected to various physicochemical studies, such as drug–polymer compatibility by thin layer chromatography (TLC) and Fourier transform infrared (FTIR) spectroscopy, surface morphology by scanning electron microscopy, frequency distribution, drug entrapment efficiency, in vitro drug release characteristics and release kinetics. The physical state of drug in the microspheres was determined by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). TLC and FTIR studies indicated no drug–polymer incompatibility. All the microspheres showed initial burst release followed by a fickian diffusion mechanism. DSC and XRD analysis indicated that the TM trapped in the microspheres existed in an amorphous or disordered-crystalline status in the polymer matrix. From the preliminary trials, it was observed that it may be possible to formulate TM microspheres by using biodegradable natural polymers such as chitosan and gelatin B to overcome the drawbacks of TM and to increase the patient compliance.     

戊型肝炎重组蛋白聚乳酸羟基乙酸微球疫苗的研究

目的:研究戊型肝炎重组蛋白(NE2)聚乳酸羟基乙酸(PLGA)微球疫苗诱导免疫应答的情况.方法:复乳法制备微球,考察粒径分布等特性.通过间接ELISA法检测其诱导BALB/c小鼠体内IgG、IgG2a和IgGl1水平,并通过IFN--ELISPOT方法检测其诱导BALB/c小鼠体内抗原特异性免疫应答情况.结果:微球的平均粒径为7.1m.注射小鼠6周后(第4周加强免疫1次),微球疫苗诱导产生的抗戊型肝炎病毒IgG抗体水平较同剂量铝佐剂组明显升高(间接ELISA:OD450/620 10.09vs.5.32).IgG2a抗体量略高于铝佐剂组,OD450/620分别为0.17、0.04.IgG1抗体量明显高于铝佐剂组.OD450/620分别为20.48、15.00.IFN--ELISPOT结果显示,微球疫苗能很好的诱导NE2或P34肽抗原特异性免疫应答.结论:戊型肝炎重组蛋白聚乳酸羟基乙酸微球作为疫苗输送体系能明显的提高抗原的免疫原性,有很好的应用前景.     

Bioadhesive Microspheres for Bioavailability Enhancement of Raloxifene Hydrochloride: Formulation and Pharmacokinetic Evaluation

Raloxifene hydrochloride (R-HCl), a BCS class II drug, remains a mainstay in the prevention and pharmacologic therapy of osteoporosis. Its absolute bioavailability, however, is 2% due to poor solubility and extensive first pass metabolism. The present study describes two simultaneous approaches to improve its bioavailability, complexation of R-HCl with cyclodextrin(s), and formulation of mucoadhesive microspheres of the complex using different proportions of carbopol and HPMC. Microspheres were pale yellow in color, free-flowing, spherical, and porous in outline. The particle size ranged between 3 and 15 μm, and entrapment efficiency was found to be within 81.63% to 87.73%. A significant improvement in the solubility of R-HCl was observed, and it differed with the combination of excipients used. X-ray diffraction and differential scanning calorimetry studies revealed that enhancement in drug solubility was resulted due to a change in its crystallinity within the formulation. Microspheres possessed remarkable mucoadhesion and offered controlled drug release, lasting up to 24 h. They produced a sharp plasma concentration–time profile of R-HCl within 30 min post-administration to Wistar rats. [AUC]_0–24 h was found to be 1,722.34 ng h/ml, and it differed significantly to that of pure drug powder (318.28 ng h/ml). More than fivefold increase in AUC and more than twofold increase in MRT were observed. FT-IR studies evidenced no interaction among drug and excipients. The results of this study showed that mucoadhesive microspheres could be a viable approach to improve the pharmacokinetic profile of R-HCl.     

Development and Evaluation of Biodegradable Chitosan Films of Metronidazole and Levofloxacin for the Management of Periodontitis

Metronidazole (MZ) and levofloxacin (LF) are widely employed for treatment of periodontitis, but high oral dose and resistance development after long-term oral administration limit their use. The aim of this study was to alleviate shortcomings in the treatment of periodontitis by fabrication of intrapocket, biodegradable films of chitosan (CS) loaded with MZ and LF meant for inserting into periodontal pockets to treat infections. The films were developed by solvent casting technique using propylene glycol as plasticizer and glutaraldehyde as crosslinking agent. Their physical characteristics, such as drug content, surface pH, swelling index, and folding endurance, exhibited results within limit. Further, FTIR and DSC studies revealed stability of films and compatibility between drugs and excipients. SEM images of films showed the presence of free drug particles on the surface causing burst effect. In vitro release in McIlvaine buffer pH 6.6 was of sustained nature assisted by the burst effect. CS and crosslinking agent concentrations negatively affected drug release and positively affected T₉₀ (time for releasing 90% of the drug) due to altered matrix density. In contrast, the plasticizer concentration increases membrane permeability and hence increased drug release, lowering T₉₀. Crosslinked films demonstrated sustained release up to 7 days. The antibacterial efficacy of films was tested on Staphylococcus aureus and Escherichia coli, indicating good antibacterial activity. Clinical trials on patients proved the therapeutic efficacy of the films by a significant (p?<?0.05) decrease in the clinical markers of periodontitis, i.e. gingival index, plaque index and pocket depth. Conclusively, the films of MZ and LF were successful tools for the management of periodontitis.     

降钙素葡聚糖颗粒缓释微球的研究

目的：降钙素（一个由32个氨基酸组成的多肽）是治疗骨质疏松的首选药之一。降钙索的劣势是其半衰期过短,需要一天一次注射给药,本实验旨在制备突释小,药物释放浓度稳定的降钙素微球制剂。方法：制备降钙素羧酸葡聚糖颗粒和降钙素硫酸葡聚糖颗粒组合物,分别将其包裹于PLGA微球内,制备成降钙素组合微球,采用C18反相色谱柱研究药物的包封率和体外释放行为。结果：所制得的降钙素葡聚糖颗粒缓释微球体外释放一个月,释放曲线比较完美,接近零级释放。结论：本研究制得的降钙素葡聚糖颗粒缓释组合微球能实现理想的体外缓释效果,为后期药动学实验提供基础。     

Physico-mechanical and Stability Evaluation of Carbamazepine Cocrystal with Nicotinamide

The focus of this investigation was to prepare the cocrystal of carbamazepine (CBZ) using nicotinamide as a coformer and to compare its preformulation properties and stability profile with CBZ. The cocrystal was prepared by solution cooling crystallization, solvent evaporation, and melting and cryomilling methods. They were characterized for solubility, intrinsic dissolution rate, chemical identification by Fourier transform infrared spectroscopy, crystallinity by differential scanning calorimetry, powder X-ray diffraction, and morphology by scanning electron microscopy. Additionally, mechanical properties were evaluated by tensile strength and Heckel analysis of compacts. The cocrystal and CBZ were stored at 40°C/94% RH, 40°C/75% RH, 25°C/60% RH, and 60°C to determine their stability behavior. The cocrystals were fluffy, with a needle-shaped crystal, and were less dense than CBZ. The solubility profiles of the cocrystals were similar to CBZ, but its intrinsic dissolution rate was lower due to the high tensile strength of its compacts. Unlike CBZ, the cocrystals were resistant to hydrate transformation, as revealed by the stability studies. Plastic deformation started at a higher compression pressure in the cocrystals than CBZ, as indicated by the high yield pressure. In conclusion, the preformulation profile of the cocrystals was similar to CBZ, except that it had an advantageous resistance to hydrate transformation.     

生物可降解聚酯PBS的合成工艺研究

目的:为了提高1,4-丁二醇的附加值和开发新型的生物可降解材料.方法:以钛酸四丁酯为催化剂通过酯化缩聚合成了聚丁二酸丁二醇酯(PBS).考察了醇酸摩尔比、催化剂用量、反应温度、反应时间等因素对酯化率的影响.结果:醇酸物质的量比为1∶1.2,催化剂用量为0.6%(质量百分含量),反应温度220℃,反应时间6h,酯化率可达98.7%,平均分子量和分子量分布分别为:Mn=182197,Mw/Mn=1.626406.利用红外谱(IR)、凝胶渗透色谱(GPC)对产物进行了表征确认.     

胶原酶缓释微球的研究

目的:本实验旨在开发一种胶原酶缓释微球制剂,用以治疗手掌腱膜挛缩症,以减小现有水针剂的不足。方法:利用水相-水相乳化法和低温冷冻相分离法两种方法制备载药颗粒,分别将其包裹于PLGA微球内,制备成胶原酶微球,并用扫描电镜考察其表面形态,对其粒径进行统计学分析,测定体外释放行为并比较。结果:两种方法制备的微球表面光滑圆整,都可以达到缓释的效果,一个星期内释药完全。水相-水相乳化法制备的微球比低温冷冻相分离制备的微球粒径大,且具有统计学差异(P0.05)。水相-水相乳化法制备的微球粒径较均一,其体外释放更加平缓,突释较小。结论:本研究制得的胶原酶微球能实现理想的体外缓释效果,解决了现有技术中胶原酶粉针剂型快速释放并分散的问题。