肝靶向抗病毒药NGA－ACV的制备及其趋肝性

以无唾液酸糖蛋白受体（ａｓｉａｌｏｇｌｙｃｏｐｒｏｔｅｉｎｒｅｃｅｐｔｏｒ，ＡＳＧＰＲ）的特异性配体半乳糖基拟糖白蛋白（ｎｅｏｇｌｙｃｏａｌｂｕｍｉｎ，ＮＧＡ）为载体，通过丁二酰基桥将抗病毒药无环鸟苷（ａｃｙｃｌｏｖｉｒ，ＡＣＶ）与ＮＧＡ偶联，得到肝靶向抗病毒药ＮＧＡＡＣＶ。差热分析和高效液相色谱分析结果表明，ＮＧＡＡＣＶ是共价键偶联物，且在血液中稳定性很好。将偶联物用１３１Ｉ标记后进行家兔放射性显像比较研究。结果，高、低药密度ＮＧＡＡＣＶ的肝脏放射性分别是全身放射性的８１．６％和８６．６％，其趋肝性无明显差别。研究小鼠体内高药密度１３１ＩＮＧＡＡＣＶ的分布，在５ｍｉｎ时肝脏放射性达到峰值，为注入量的８１．７±１０．４％。受体竞争抑制实验表明ＮＧＡＡＣＶ的肝靶向机理为受体介导的主动靶向过程。初步体外抗乙肝病毒比较研究表明，ＮＧＡＡＣＶ较ＡＣＶ的抗病毒剂量有明显降低。     

肝靶向抗癌药NGA-DHAQ的合成研究

以D－半乳糖和人血清白蛋白（HSA）合成无唾液酸糖蛋白受体的特异性配体一半乳糖基拟糖白蛋白（neoglycoalbumin,NGA）;以NGA为载体通过丁二酰基桥将米托蒽醌（mitoxantrone,DHAQ）与其偶联,得到肝靶向药物NGA－DHAQ,紫外光谱和HPLC分析表明：NGA－DHAQ为化学偶联物,在血液中稳定。     

肝靶向药物研究——模型化合物NGA-去甲替林的合成及其趋肝性

肝细胞膜上的肝结合蛋白(HBP)是无唾液酸糖蛋白的受体。作者合成了无唾液酸糖蛋白的类似物—半乳糖新糖白蛋白(NGA)并用其作为肝靶向药物的载体,采用琥珀酸酐法与药物去甲替林(NT)偶联得NGA-NT。以此作模型化合物,经~(99m)Tc标记后的动物放射显像及HPLC检测结果,说明NGA-NT在血中稳定,在肝脏降解释出NT,具有显著的趋肝性。     

受体介导的肝靶向载药系统研究进展

介绍近几年已报道的有关受体介导的肝靶向载药系统的研究情况。近年来受体介导的肝靶向载药系统的研究取得了一些可喜进展,相关配体-受体可与药物、脂质体、纳米粒、基因、偶联物等相连,提高药物或载体的肝靶向能力。受体介导机制在肝靶向载药系统的研究领域具有广阔的应用前景,尤其是肝脏特异性受体的不断发掘,丰富了肝主动靶向的理论体系,展示了肝脏疾病治疗的美好未来。     

阿昔洛韦复乳的研究:大鼠吸收动力学、生物利用度和趋肝性

目的:研究阿昔洛韦(ACV) 复乳的口服生物利用度和肝靶向性。方法:采用高效液相色谱法测定大鼠口服ACV 复乳和普通片剂后的血药浓度和肝组织分布,对试验数据进行药动学分析。药物浓度对时间数据作房室模型和统计矩解析,并求出相应的药动学参数。结果:大鼠口服ACV 复乳对片剂的相对生物利用度为149-8 % ,达峰时间和血浓维持时间明显延迟。血浓经时过程符合二室开放线性药动学模型。血浓峰值附近的肝组织药物分布是片剂的1-62 倍(P<0.1) ,谷值附近是片剂的5-16 倍(P<0.05) 。结论:大鼠口服ACV 复乳可提高生物利用度,并有一定的肝靶向性。     

肝靶向抗疟药半乳糖基拟糖白蛋白-伯氨喹偶联物和磷酸伯氨喹的药代动力学

用HPLC法对肝靶向抗疟药NGA-PQ各磷酸伯氨喹(PQP)在小鼠体内的药代动力学行为进行了比较研究。结果表明NGA-pQ在血中有较好的稳定性,不易解离出PQ。NGA-PQ和PQP在肝中的Tm分别为10和15min,在血中的T_1/2分别为20.44和35.74min。在肝中的T_1/2分别为43.95和21.46min,肝中的AUC分别为2305.80和333.29min·μg^-1·g^-1。说明NGA-PQ在血中很快消除并浓集于肝脏,在肝脏的保留时间长,从而证实NGA-PQ具肝靶向分布特性。     

肝靶向氟尿嘧啶类脂纳米粒的研究

目的　为了提高氟尿嘧啶(5-Fu)的疗效,降低其毒副作用,制备具肝靶向的5-Fu类脂纳米粒。方法　利用氟尿嘧啶与硬脂酰氯进行反应,制备了5-Fu前体药物N₁-硬脂酰-5-Fu,通过红外光谱及核磁共振谱对合成的目标化合物进行结构确认。同时研究了前体药物的性质及稳定性。采用物理凝聚法制备类脂纳米粒,并研究其形态、粒径及粒径分布、载药量、体外释药特征、动物体内分布与药代动力学参数等。结果　平均粒径d_av=240.19 nm,载药量为20.53%。体外释药速率符合一级动力学模型。与5-Fu水针剂比较,类脂纳米粒组在肝脏中药物含量平均增加了一倍以上。家兔体内主要药动学参数为：V_c=0.04336 L.kg^-1,T_1/2β=1.2834 h,CL=0.1632 L.h^-1。结论　利用前体药物可提高药物的脂溶性,首次以物理凝聚法制备类脂纳米粒,小鼠体内分布研究表明类脂纳米粒有明显的肝靶向,有一定的优越性和参考价值。     

肝靶向米托蒽醌白蛋白微球的研究

用乳化—热固化法制备了米托蒽醌白蛋白微球,并对其形态、大小及其分布、微粉学性质、载药性能、体外释药、稳定性和体内分布进行了研究。结果表明,该载药微球的平均算术径为0.99μm,平均表面径为1.24μm,平均容积径为1.44μm;表观载药量为2.558%±0.101%;有效载药量为1.503%±0.127%;包封率为92.82%±4.60%;体外释药符合双相动力学规律,释药方程为1-Q=0.6428e^-0.2132t+0.3988e^-000150t(γ₁=-0.9951,γ₂=-0.9982);T_1/2α=3.250h,T_1/2β=461.7h;室温放置3个月,微球形态、药物含量等均无明显变化。HPLC测定表明,小鼠尾iv该微球20min内即有77.6%±1.38%的药物浓集于肝脏,具有明显的肝靶向性。提示米托蒽醌白蛋白微球有可能提高米托蒽醌的抗肝癌效果和降低其全身毒副作用。     

半乳糖多聚赖氨酸的肝靶向特征

以还原胺化法合成了半乳糖多聚-L-赖氨酸(GalPLL), 并首次利用放射性示踪实验测定了GalPLL在小鼠体内的肝靶向特征. 结果表明, GalPLL具有较高的肝靶向性, 其在体内的分布形式与肝细胞去唾液酸糖蛋白受体(ASGPR)的内源性配体去唾液酸胎球蛋白(ASF)相似. ¹²⁵I标记的GalPLL经静脉注入小鼠体内后, 主要被肝脏吸收, 在注射后5 min时肝脏的最大吸收为注射总量的38.9%, 比人血清白蛋白高5.7倍. 肝脏对GalPLL的吸收可特异地被ASF及非标记的GalPLL抑制, 但不能被未半乳糖基化的多聚-L-赖氨酸抑制, 证明GalPLL是通过肝细胞ASGPR介导的内吞作用特异地被肝脏吸收的. 由于GalPLL不但具有较高的肝靶向性,而且与ASGPR的天然配体相比在合成和应用方面均具有许多优势, 因此有望成为进行药物或基因肝靶向运送的良好载体.     

脂质体肝实质细胞靶向性研究

目的 脂质体经配体修饰后介导受体细胞,以达靶向给药。方法 肝实质细胞上无唾液酸糖蛋白受体(ASGP-R)的配体无唾液酸胎球蛋白(AF)修饰脂质体得AF-SSL。将ASGP-R重组于脂质双分子膜(BLM)得ASGP-R-BLM,与AF-SSL相互作用,监测BLM膜电参数变化,确定受体-配体间识别反应;用3H标记方法测AF-SSL与肝实质细胞在体内外靶向性;将AF-SSL包抗癌药阿霉素(ADM),考察其抗癌药效。结果ASGP-R-BLM稳定时间随AF-SSL加入量增加而缩短,表现出明显的量效关系,证明在ASGP-R-BLM与AF-SSL之间有特异识别反应;体外AF-SSL与肝实质细胞结合率明显高于无AF修饰脂质体SSL(在第10和90 min时P<0.05,在第30和60 min时P<0.01);抗肝癌疗效,AF-SSL组大鼠存活期显著长于无AF修饰组,且对心、肾、肺的毒副作用小。结论配体修饰脂质体达到主动靶向对应受体细胞是可行的,本文为脂质体细胞水平靶向给药提供依据。     

Synthesis and biological evaluation of 131I‐labelled pyronaridine

¹³¹I‐Labelled pyronaridine, an antimalarial drug was synthesized and evaluated for its stability and biodistribution in rabbits. We observed that there was >99% yield of the labelled compound as determined by HPLC and radio‐TLC in our study. Dynamic imaging studies in rabbits showed that ¹³¹I‐labelled pyronaridine was not concentrated in the thyroid for up to 30 min as that of Na¹³¹I. Biodistribution studies in the blood, liver, heart, spleen, kidney and lung of rats revealed that the maximum percentage of the injected dose (% ID) and the percentage of the injected dose per gram organ weight (% ID/g) of ¹³¹I‐labelled pyronaridine was found in the blood and liver when compared to the other organs even after 6 days of the drug administration. Results suggest that ¹³¹I‐labelled pyronaridine can be effectively used as an imaging agent to study the metabolism and mode of a response of pyronaridine. Copyright © 2007 John Wiley & Sons, Ltd.     

Topical Iontophoresis of Valaciclovir Hydrochloride Improves Cutaneous Aciclovir Delivery

Purpose To investigate the topical iontophoresis of valaciclovir (VCV) as a means to improve cutaneous aciclovir (ACV) delivery.Methods ACV and VCV electrotransport experiments were conducted using excised porcine skin in vitro.Results While the charged nature of the prodrug, VCV, enabled it to be more efficiently iontophoresed into the skin than the parent molecule, ACV, only the latter was detectable in the receptor chamber, suggesting that VCV was enzymatically cleaved into the active metabolite during skin transit. Iontophoresis of VCV was significantly more efficient than that of ACV; the cumulative permeation of ACV after 1, 2 and 3 h of VCV iontophoresis at 0.5 mA cm⁻² and using an aqueous 2 mM (∼0.06%) formulation was 20 ± 10, 104 ± 47 and 194 ± 82 μg cm⁻², respectively (cf. non-quantifiable levels, 0.1 and 1.0 ± 0.7 μg cm⁻² after ACV iontophoresis).Conclusions These delivery rates provide ample room to reduce either current density or the duration of current application. Preliminary in vitro data serve to emphasize the potential of VCV iontophoresis to improve the topical therapy of cutaneous herpes simplex infections and merit further investigation to demonstrate clinical efficacy.     

The Influence of Iontophoresis on Acyclovir Transport and Accumulation in Rabbit Ear Skin

Purpose The aim of this work was to explore the effect of iontophoresis on acyclovir (ACV) accumulation and permeation. In particular, the objectives were to check the efficacy of the transport mechanisms, electromigration and electroosmosis, on drug accumulation.Methods Permeation experiments were performed in vitro, using rabbit ear skin as barrier, from donor solutions at pH 3.0, 5.8, and 7.4. At the end of the experiments, drug accumulation in epidermis and dermis was measured. Anodal and cathodal iontophoresis were applied at pH 3.0, whereas only anodal iontophoresis was used at pH 5.8 (current densities 0.06–0.50 mA/cm²) and 7.4.Results Cathodal iontophoresis was more efficient than anodal iontophoresis on ACV permeation across the skin at pH 3.0. At pH 5.8, ACV flux and accumulation increased with current density during anodal iontophoresis. At pH 7.4, anodal iontophoresis produced a remarkable increase of flux and a modest increase of accumulation. Overall, anodal flux increased as the pH of the donor solution was increased as a result of the increase of the skin net negative charge.Conclusions From the results obtained in the present work, it can be concluded that iontophoresis application increases ACV flux and, to a limited extent, accumulation in the skin.     

Radiolabeling of EGCG with <Superscript>131</Superscript>I and biodistribution in rats

Epigallocatechin gallate (EGCG), is the most abundant and widely studied catechin in green tea (Camellia sinensis Theaceae). The inhibitory effects of EGCG and green tea extract on carcinogenesis in various organs in rodents have now been demonstrated over the past decade. The aim of study was to label EGCG with I-131, to determinate its structure and to evaluate its biodistribution in Wistar rats. Radiolabeling was carried out by direct electrophilic iodination method (iodogen) and yield was determined by radio thin layer chromatography (RTLC). Radiolabelling yield is determined as 89 ± 1.0%. Besides, determination of structure of iodinated molecule, serum stability, and partition coefficient experiments was performed. The structure analysis of synthesized cold ¹²⁷I-EGCG complex was assessed with LC–MS–MS and ¹H-NMR. ¹H-NMR and LC–MS–MS results of iodinated EGCG (¹²⁷I-EGCG) show that oxidize iodine reacts electrophilic with aromatic ring. Serum stability results showed that in vitro stability of ¹³¹I-EGCG was quite high. It is observed that labeling percentage decreased 83 ± 2% at 24th, Partition coefficient results show that the partition coefficient of EGCG was calculated as theoretical partition coefficient = 2.04 ± 0.42 and the experimental partition coefficient of ¹³¹I-EGCG was found as 1.46 ± 0.2. The biodistribution data shown that the maximum uptake of the radioiodinated EGCG was seen in lung and pancreas at 30 min. The blocking assay results indicated that the uptake of ¹³¹I-EGCG in lung was not significantly change (0.25, 0.23, and 0.22%ID/g at 30, 60, and 150 min, respectively). Biodistribution data showed no significant uptake in a specific organ of the rat. Hence radiolabeled EGCG is seen in some organs (lung, liver, pancreas, kidney, etc.).     

Radioiodinated acebutolol as a new highly selective radiotracer for myocardial perfusion imaging

Acebutolol was successfully labeled with ¹²⁵I via direct electrophilic substitution reaction. Radioiodinated acebutolol was prepared with a maximum radiochemical yield of 96.5 ± 0.3% and in vitro stability up to 72 h. The in vivo biological distribution of radioiodinated acebutolol showed high heart uptake of 37.8 ± 0.14% injected activity/g organ with low lungs and liver uptakes at 5 min post‐injection. In vivo receptor blocking study was carried out in mice to evaluate its selectivity to heart. Radioiodinated acebutolol showed fast heart accumulation with high heart/liver ratio, which provides the ability for fast myocardial imaging with significant decrease in the radiation hazards risk on patients. So, radioiodinated acebutolol could be displayed as a radiotracer drug of choice in case of emergency patients for myocardial perfusion imaging.     

Necrosis affinity evaluation of 131I-hypericin in a rat model of induced necrosis

Abstract

Cancers are often with spontaneous or therapeutic necrosis that could be utilized as a generic target for developing new treatments. The purpose of this study was to investigate the biodistribution and pharmacokinetics of radioiodinated hypericin (Hyp), a naturally occurring compound, after intravenous (i.v.) injection in a rat model of liver and muscle necrosis (n?=?42), and evaluate its necrosis affinity. Hyp was labeled with ¹³¹I with labeling efficiency >99%. After incubating in solution/rat plasma for 8 days, radiochemical purity of ¹³¹I-Hyp remained 98.1 and 97.1%, respectively, indicating good in vitro stability. SPECT-CT images at 24?h after i.v. injection of ¹³¹I-Hyp in rats with induced liver and muscle necrosis showed obvious tracer absorption in necrotic tissues. Biodistribution studies revealed that the percentage of the injected dose per gram of tissue (%ID/g) evolved from 1.9 %ID/g at 6?h, through a maximum 3.0 %ID/g at 12?h, to 1.0 %ID/g at 192?h in necrotic liver. Pharmacokinetics studies revealed that the terminal elimination half-life, total body clearance and area under the curve of ¹³¹I-Hyp were 32.7?h, 9.2?L/h/kg and 1.6?MBq/L*h, respectively. These results demonstrated that ¹³¹I-Hyp features a long blood circulation in animals and persistent retention in necrotic tissues. Therefore, ¹³¹I-labeled Hyp could be a broad-spectrum anti-tumor agent with a cost much cheaper relative to the biological agents such as monoclonal antibodies.     

Scintillation proximity radioimmunoassay for the measurement of acyclovir

A homogeneous, single-tube scintillation proximity radioimmunoassay (SPRIA) to quantitate acyclovir (Zovirax^®), ACV, (9-[(2[hydroxyethoxy)]methylguanine)} in human plasma is described. The reagents for the SPRIA are an anti-ACV monoclonal antibody (WACO4 MAb), tritiated ACV, and scintillation proximity reagent (goat anti-mouse immunoglobulin G (IgG) coupled to fluoromicrospheres). The ACV standard curve range in the SPRIA is from 0.7 ng ml⁻¹ (3.0 nmol l⁻¹) to 90.0 ng ml⁻¹ (0.4 μmol l⁻¹) with a 50% inhibitory concentration of 5.0 ng ml⁻¹ (22.2 nmol l⁻¹). However, the lower limit of quantification is 7 ng ml⁻¹ at 1:10 dilution of plasma. Analytical recovery of ACV in spiked human plasma controls ranges between 90–110%. Intra- and inter-assay relative standard deviations were < 8%. This high throughput homogeneous assay is a rapid, convenient and simple alternative to the current radioimmunoassay that uses ammonium sulfate precipitation as the separation method. This technique is particularly attractive because it requires neither separation of bound from free drug nor use of scintillation fluid. The procedure was applied to quantitate ACV in samples from pre-clinical and clinical studies after the administration of valaciclovir, a prodrug of ACV (256U87, Valtrex^®, l-valyl ester of ACV). Automation of this assay will further improve efficiency in processing a larger number of samples.     

Development of mucoadhesive floating hollow beads of acyclovir with gastroretentive properties

Abstract

This study aimed at improving the oral bioavailability of acyclovir (ACV) through incorporating it into gastroretentive dosage form based on floating hollow chitosan beads. Hollow chitosan beads were prepared using a solvent free, ionotropic gelation method. The effect of formulation parameters, including chitosan molecular weight and drug concentration, on bead characteristics was studied. The drug containing formulations had yields >70.5?±?0.31%. The entrapment efficiencies for the medium molecular weight chitosan formulations (56.29?±?0.94%–62.75?±?0.86%) was greater than the high molecular weight chitosan formulation (29.21?±?0.89%). The density of all formulations was below that of gastric fluid, the greatest density observed was 0.60?±?0.01?g?cm^?3. Unsurprisingly, the formulations were immediate bouyant to different degrees in both pH 1.2 and pH 6.8 media. In addition, the chitosan beads were all seen to swell in pH 1.2 media and demonstrated mucoadhesive properties. A sustained release profile was observed from the chitosan beads, the developed formulations released drug at slower rates than a marketed ACV oral tablet. The developed system has the dual advantages of being gastroretentive, to increase oral bioavailability and releasing drug in a controlled manner, to reduce the required frequency of administration thereby promoting patient adherence.