卡巴他赛纳米混悬剂的制备与质量评价

摘 要 目的：制备卡巴他赛纳米混悬剂,并考察其理化性质。方法: 采用高压均质法制备卡巴他赛纳米混悬剂,以粒径分布作为评价指标,均质压力（X1）和均质次数（X2）为考察对象,利用Box Behnken效应面法优化卡巴他赛纳米混悬剂的制备工艺;考察卡巴他赛纳米混悬剂的外观、微观形态、平均粒径、Zeta电位等理化性质,比较卡巴他赛纳米混悬剂与市售卡巴他赛注射液的体外释药行为。结果: 卡巴他赛纳米混悬剂最优制备工艺为：850 bar均质压力下均质处理6次,制备的卡巴他赛纳米混悬剂在扫描电镜下呈大小均匀分布,平均粒径为（208.6±33.6）nm,PdI为（0.179±0.015）,Zeta电位为（-32.4±0.3）mV,将卡巴他赛制备成纳米混悬剂可提高其体外溶出速率。结论: 高压均质法制备卡巴他赛纳米混悬剂工艺简单易行,卡巴他赛纳米混悬剂能够加快药物释放,提高药物体外溶出速度。     

卡巴他赛白蛋白纳米粒的制备及其体外生物相容性评价

目的 制备卡巴他赛白蛋白纳米粒（CBZ-BSA-Gd-NP）以降低药物毒性,并评价其体外生物相容性。方法 采用生物矿化法制备CBZ-BSA-Gd-NP,对其处方工艺进行优化,对粒径、Zeta电位、载药量等性质进行表征,并采用体外溶血试验考察其体外血液相容性。结果 制得的纳米粒包封率为63.04%,载药量为10.51%,平均粒径为（166.1±4.7） nm,粒径的多分散系数（PDI）为0.256,Zeta电位为（-18.14±1.16） mV,与卡巴他赛-吐温溶液相比,体外溶血作用显著降低。结论 该方法操作简便,制备的CBZ-BSA-Gd-NP载药量高,粒径均匀,体外血液相容性好,增加了药物使用的安全性。     

多西他赛长循环脂质体的制备与大鼠体内药动学评价

摘 要 目的：制备多西他赛长循环脂质体,并评价大鼠尾静脉给药的药动学特性。方法: 采用薄膜分散 挤出法制备多西他赛长循环脂质体,并对其粒径分布、Zeta电位和微观形态进行表征。将12只Wistar大鼠随机分为多西他赛注射液组和多西他赛长循环脂质体组,尾静脉给药剂量均为7.5 mg·kg^-1,采用HPLC法测定大鼠血中多西他赛的药物浓度,采用3P97程序计算多西他赛大鼠体内药动学参数。结果: 多西他赛长循环脂质体平均粒径为（109.2±28.6）nm,Zeta电位为（-15.8±2.7）mV。多西他赛注射液和多西他赛长循环脂质体在大鼠体内的t_1/2(α)分别为（0.19±0.05）h和（0.36±0.07）h;t_1/2(β)分别为（1.82±0.33）h和（17.93±1.37）h;AUC_0-t分别为（4.42±0.76）μg·mL^-1·h^-1和（33.73±3.52）μg·mL^-1·h^-1。结论:多西他赛长循环脂质体与市售多西他赛注射液相比,延长了药物在血浆中的滞留时间,能达到长循环目的。     

苯丁酸氮芥脂质体的制备及处方因素考察

目的 制备苯丁酸氮芥脂质体并优化其处方。方法 薄膜超声分散法制备苯丁酸氮芥脂质体,采用微柱离心-HPLC法测定其包封率,以包封率为考察指标,研究膜材比、药脂比、水相介质pH值以及磷脂浓度等因素对脂质体包封率的影响;通过正交试验对处方进行优化,并进行质量评价。结果 苯丁酸氮芥脂质体优化后的制备处方为胆固醇与磷脂质量比1∶3、药脂比1∶10、水相介质pH值为7.4、磷脂浓度为0.3%。按该处方制得的苯丁酸氮芥脂质体包封率>87%,平均粒径为84.71 nm,PDI为0.167。结论 优选处方稳定可行,制备的苯丁酸氮芥脂质体包封率高、粒径小且均匀。     

脱甲氧基姜黄素纳米脂质载体的制备及处方工艺优化

摘 要 目的：优选脱甲氧基姜黄素纳米脂质载体（CurⅡ-NLC）的最佳处方工艺。方法: 以包封率为主要考察指标,采用单因素考察和正交试验法研究制备工艺中影响纳米粒质量的主要因素,筛选出较理想的处方和工艺。结果: 优选的最佳处方工艺为：药脂比为1∶40,液态脂质占总脂质的比例为10%,卵磷脂的用量为2%,表面活性剂用量为4%。优化工艺所制备的纳米粒为球形或类球形实体,粒径在110nm左右,PDI为0.199,粒径分布均匀。结论:由正交试验法优选处方工艺稳定可行,为脱甲氧基姜黄素进一步研究提供参考依据。     

基于pH梯度载药技术的咪喹莫特脂质体的制备工艺研究

目的 根据咪喹莫特的理化性质,利用pH梯度主动载药技术制备脂质体,考察其性状、粒径、表面电荷及体外释药特征。方法 葡聚糖凝胶滤过法测定脂质体的包封率,以包封率与成型性为主要指标筛选制备方法,考察水化液的种类、pH值、离子强度及pH梯度载药、磷脂-胆固醇比例、脂药比、维生素E用量对包封率的影响;正交试验优化咪喹莫特脂质体的处方,考察脂质体样品在0~4℃下的稳定性。结果 按处方咪喹莫特50 mg、大豆卵磷脂400 mg、胆固醇130 mg、油酸10 mg、维生素E 5 mg、柠檬酸pH 2.5缓冲液5 mL,采用薄膜分散法工艺制备脂质体样品,并进行pH梯度主动载药,pH值调至7.0。制得的咪喹莫特脂质体呈白色均匀的混悬液,脂质体微粒圆整,分散性好,粒径（347±21）nm,包封率（81.2±1.9）%,Zeta电位（-12.19±1.7）mV。结论 pH梯度主动载药技术适于咪喹莫特脂质体的制备。     

乌拉草总黄酮脂质体凝胶剂的制备工艺研究

目的 优化乌拉草总黄酮脂质体凝胶剂的制备工艺,并进行质量评价。方法 乙醇注入法制备乌拉草总黄酮（CMTF）脂质体,以包封率为指标,正交试验优化处方;以脂质体凝胶剂的外观、涂展性、均匀度、黏稠度等综合评分为指标,采用Box-Behnken响应面法优化CMTF脂质体凝胶的处方及制备工艺。通过观察性状、pH值、铺展性及可洗除性,以及离心试验、耐寒及耐热试验,考察CMTF脂质体凝胶稳定性;观察其对大鼠正常及破损皮肤的刺激性。结果 CMTF脂质体的最佳制备工艺为：大豆磷脂与胆固醇的质量比为5：3,大豆磷脂与CMTF的质量比为4：1,注入体积比例1：10;平均包封率为89.41%,粒径为（119.7±3.82）nm,Zeta电位为（-20.80±0.40）mV。CMTF脂质体凝胶剂的最佳处方为：1 g CMTF脂质体、2 g卡波姆940、20 g甘油、2 g三乙醇胺、10 mL水,该脂质体凝胶剂的稳定性良好,无皮肤刺激性。结论 优化后的CMTF脂质体凝胶制备工艺简单,质量稳定,为CMTF经皮制剂的开发提供依据。     

光敏ROS响应型雷帕霉素脂质体的制备及表征

目的 研究光敏活性氧自由基（reactive oxygen species,ROS）响应型雷帕霉素脂质体的制备工艺及其性质,旨在开发一种稳定高效的刺激响应型脂质体载体。方法 采用薄膜分散法制备雷帕霉素脂质体;马尔文激光粒度仪测定其粒径及Zeta电位;利用HPLC法建立雷帕霉素含量测定方法;经近红外光照射后,采用反向透析法考察雷帕霉素脂质体的体外释放特性。结果 雷帕霉素脂质体粒径<200 nm,PDI值<0.200;雷帕霉素在0.2～40 μg/ml范围与峰面积呈良好的线性关系,相关系数r=0.9995;雷帕霉素脂质体包封率>94.20%;经730 nm近红外光照射5 min后,雷帕霉素脂质体12 h内体外释放率可达60%。结论 成功制备了光敏ROS响应型雷帕霉素脂质体,具有较高的包封率和体外刺激响应效率。     

银杏内酯B脂质体的处方与制备工艺研究

目的 将银杏内酯B（ginkgolide B，GB）制备成脂质体，增加GB在水中的分散性和稳定性。方法 采用超滤离心法分离脂质体与游离药物，HPLC测定脂质体中GB的含量与包封率，采用薄膜分散法制备GB脂质体；通过单因素与正交试验分析药脂比、胆固醇用量、装载量、水化温度和水化时间等因素对包封率的影响，以外观、包封率、粒径为评价指标确定GB脂质体的最佳处方和制备工艺。结果 GB脂质体的最佳处方为10 mg GB、160 mg蛋黄卵磷脂、40 mg胆固醇、8 mg维生素E、58 mg DSPE-PEG2000、5 mL PBS缓冲液；优化后的工艺条件为GB与脂质辅料溶于无水乙醇中，33℃水浴条件下减压旋转蒸发除乙醇，pH 6.5 PBS缓冲液水化脂质薄膜，水化温度35℃，时间120 min，粗脂质体混悬液冰水浴超声6 min，超声功率120 W。制备的GB脂质体混悬液微泛蓝色乳光、可透光，粒径为（126±4） nm，包封率>87%，放置24 h无聚集、无沉降。结论 采用薄膜法在实验室阶段成功制备了稳定的GB脂质体，确定了最优制备处方和制备工艺，为GB制剂的剂型研究做出探索和提供参考。     

卡巴他赛注射液在比格犬体内的药代动力学

摘 要 目的：建立LC-MS/MS法测定卡巴他赛在比格犬血浆中的浓度,并将该方法应用于卡巴他赛注射液在比格犬体内的药动学研究。方法: 以卡马西平为内标,血浆样品经甲醇沉淀蛋白,富集生物样品中的卡巴他赛,然后进行LC-MS/MS检测。色谱柱采用Agilent EC C₁₈柱（50 mm×4.6 mm,2.7 μm）,柱温为30℃,以甲醇-水（95∶5）为流动相,流速为0.5 ml·min^-1,进样量为5 μl,采用电喷雾电离源（ESI）,正离子多反应监测（MRM）扫描分析,卡巴他赛和内标的离子选择通道分别为m/z858.4→577.4,m/z237.1→194.1;比格犬单剂量静脉静滴卡巴他赛注射液20 mg·h^-1,于不同时间点取血测定血浆中药物的含量并利用DAS 2.0软件计算其药动学参数。结果: 卡巴他赛在10.0~1 000.0 ng·ml^-1范围内线性关系良好,平均回收率均大于93.53%,日内与日间精密度（RSD）均小于7.4%。比格犬静脉注射卡巴他赛后AUC(0-t)为（155 181.93±11 593.33） ng·ml^-1·min^-1,AUC(0-∞)为（167 528.12±16 671.46） ng·ml^-1·min^-1,T_max为60 min,C_max为(688.37±52.06) ng·ml^-1。结论:该法快速、精确、简便,可用于比格犬血浆中卡巴他赛的测定及药动学研究。     

原花青素在多孔薄膜中实现高效加载和长效释放的研究

目的 探讨了原花青素药物分子通过材料表面介导的方式实现长效扩散型释放行为的可能性。方法 将原花青素分散在水中配制为药物溶液,与三氯甲烷共混后通过超声乳化的方式将混合液制备成为稳定的反相乳液。在高湿度环境条件下,将所制得的乳液浇筑在聚苯乙烯平面膜片上,待有机溶剂和水分挥发后获得表面和本体层均具有多孔结构的聚合物薄膜,并以此一步法实现原花青素在薄膜中的封装加载。最后将所制备得到的药物加载薄膜在磷酸缓冲盐溶液中浸泡进行药物释放实验,分时段取出缓冲液样品进行光谱表征确定原花青素的释放量,以此实现在28天内对原花青素释放行为的跟踪表征。结果 利用反相乳液浇筑致孔的方法,可以制备具有多层多孔结构的载药聚合物薄膜。经过乳液中水油比的调节,可以实现薄膜表层和本体层的多孔结构的调控。利用含水溶性荧光素乳液的浇筑成膜实验,并通过激光共聚焦显微镜结果证实了由反相乳液的乳液水滴所携带的亲水组分可以高效地实现在所形成多孔结构中的选择性分布,证明了原花青素组分在多孔膜当中可以实现有效加载。在这种多孔多层结构的薄膜当中所加载的原花青素可以实现超过28天以上的长效缓释,其释放行为遵循了Fickian扩散式机理。结论 利用聚合物多孔薄膜或者涂层作为药物载体,可以实现有效的药物加载和长效型释放,将能为设计高效灵活的药物释放体系提供有效的参考。     

In vitro and in vivo evaluation of novel implantable collagen–chitosan–soybean phosphatidylcholine composite film for the sustained delivery of mitomycin C

An implantable mitomycin C (MMC) delivery system (MMC‐film), incorporating polylactide (PLA)–MMC nanoparticles in a composite film from blends of collagen–chitosan–soybean phosphatidylcholine (SPC) with a mass ratio of 4:1:1, was developed and evaluated. PLA–MMC nanoparticles were prepared using an improved emulsion/solvent evaporation technique and then dispersed uniformly within the film to result in a final MMC loading content of 0.8 mg/cm². Drug release studies were performed in pH 7.4 PBS at 37°C with drug analysis using UV/vis spectrometer at 366 nm. The MMC‐film exhibited more fractional drug release and a longer time to reach release equilibrium as compared with PLA‐MMC nanoparticles. In vivo, the MMC‐film was implanted at subcutaneous tumor sites of hepatoma‐bearing mice, and the curative effect was compared with those of drug‐free film. The growth of the tumors was dose‐dependently inhibited by MMC‐film. Histopathological analysis of specimens taken from tumor tissues harvested indicated that MMC‐film was lethal to hepatoma cells. Additionally, post mortem visual examination and microscopic images showed no sign of internal infection and fibrous encapsulation in any animals after 20 days of implantation of the MMC‐film or drug‐free film. It was concluded that the system provides great potential for local sustained delivery of MMC at the site of tumor or tumor resection for therapeutic purposes. Drug Dev Res 2009. © 2009 Wiley‐Liss, Inc.     

pH敏感型羧甲基壳聚糖水凝胶的制备及体外释药考察

目的:研制一种新型羧甲基壳聚糖基pH敏感性水凝胶,考察其在药物传输体系中的应用.方法:采用钙离子交联方法制备有良好pH响应性能的羧甲基壳聚糖基水凝胶,并对其pH响应性能进行相关的表征.以磺胺嘧啶钠为模型药物,考察载药水凝胶在不同pH环境条件下(pH =2和pH =7.4)的药物释放行为.结果:所制备的羧甲基壳聚糖水凝胶具有明显的孔洞结构和良好的pH响应性能,在中性磷酸盐缓冲溶液(pH=7.4)中吸水率显著大于在酸性溶液(pH=2)中的吸水率.载有磺胺嘧啶钠的羧甲基壳聚糖水凝胶在中性磷酸盐缓冲溶液(pH=7.4)中的4h的药物累计释放率达到95％,而在酸性溶液(pH=2)中的4h的药物累计释放率却只有50％.结论:本文所制备的羧甲基壳聚糖pH敏感性水凝胶具有良好的孔隙率和pH响应性能,在口服药物传输体系中有一定的应用前景.     

One-step solid-oil-water emulsion for sustained bioactive ranibizumab release

ABSTRACT

Background: The advent of therapeutic proteins highlights the need for delivery systems that protect and extend the duration of its action. Ranibizumab-VEGF is one such drug used for treating wet AMD. This paper describes a facile method to sustain bioactive ranibizumab release from PLGA-based particles.

Methods: Two emulsion techniques were explored namely: water-in-oil-in-water (WOW) and solid-in-oil-in-water (SOW) emulsion. The bioactivity of ranibizumab was evaluated by comparing its binding capability to VEGF, measured with ELISA to total protein measured by microBCA.

Results: During the emulsion process, contact of ranibizumab with the water-oil interface is the main destabilizing factor and this can be prevented with the use of amphiphilic PVA and solid-state protein in WOW and SOW emulsion respectively. In vitro release of the ranibizumab-loaded particles indicated that a 15-day release could be achieved with SOW particles while the WOW particles generally suffered from a burst release. Released ranibizumab was capable of inhibiting endothelial cell growth indicating its retention of bioactivity. The suppression of burst release from the SOW particles was attributed to the relatively smooth surface morphology of the SOW microparticles.

Conclusions: The use of SOW encapsulation in modulating ranibizumab release while maintaining their bioactivity has been highlighted.     

Effect of Ingested Lipids on Drug Dissolution and Release with Concurrent Digestion: A Modeling Approach

Purpose

To mechanistically study and model the effect of lipids, either from food or self-emulsifying drug delivery systems (SEDDS), on drug transport in the intestinal lumen.

Methods

Simultaneous lipid digestion, dissolution/release, and drug partitioning were experimentally studied and modeled for two dosing scenarios: solid drug with a food-associated lipid (soybean oil) and drug solubilized in a model SEDDS (soybean oil and Tween 80 at 1:1 ratio). Rate constants for digestion, permeability of emulsion droplets, and partition coefficients in micellar and oil phases were measured, and used to numerically solve the developed model.

Results

Strong influence of lipid digestion on drug release from SEDDS and solid drug dissolution into food-associated lipid emulsion was observed and predicted by the developed model. Ninety minutes after introduction of SEDDS, there was 9% and 70% drug release in the absence and presence of digestion, respectively. However, overall drug dissolution in the presence of food-associated lipids occurred over a longer period than without digestion.

Conclusion

A systems-based mechanistic model incorporating simultaneous dynamic processes occurring upon dosing of drug with lipids enabled prediction of aqueous drug concentration profile. This model, once incorporated with a pharmacokinetic model considering processes of drug absorption and drug lymphatic transport in the presence of lipids, could be highly useful for quantitative prediction of impact of lipids on bioavailability of drugs.

     

Microencapsulation with carrageenan-locust bean gum mixture in a multiphase emulsification technique for sustained drug release

Abstract

A multiphase emulsification technique was modified in this process of microencapsulating gentamicin sulphate, thus avoiding the necessity for a surfactant in preparing the secondary emulsion for a W/O/W emulsion. Various proportions of iota-carrageenan (i-C) and locust bean gum (LBG) were investigated for the W/O/W emulsion after forming the primary W/O emulsion with sorbitan trioleate, Span 85. Upon removal of the oil phase (chloroform) from the W/O/W emulsion by heating (60-65°C), microcapsules or ‘W/W particles containing drug dissolved in sodium hyaluronate were spontaneously formed. These were dispersed in a solution of a mixture of 5-10 per cent w/v polyvinyl alcohol, PVA (average MW 50000-106000; 98 per cent hydrolysed) and 3 per cent v/v polyethylene glycol 200 (PEG 200), and dried to form the hydrogel film casts. Our in vitro experiments in isotonic phosphate buffer solution (pH 7-4) at 37°C., showed that the release of gentamicin sulphate was dependent on concentration of LBG, and concentration or molecular weight of PVA. With the exception of PVA hydrogel matrix preparations containing 20 per cent w/v LBG, all other formulations showed a significant initial ‘burst' release of drug within 6h. The drug-containing microcapsules in the PVA hydrogel film with 20 per cent w/v LBG, exhibited an almost zero-order release of drug up to 140h. It is postulated that an effective barrier or high-density membrane enveloping the microcapsules was formed between i-C and LBG because of their unique molecular configurations. This phenomenon, together with the possible adsorption of i-C molecules at the transient oil and outer aqueous phase interface, presumably eliminated the need for a permanent oil phase and/or an O/W surfactant normally required for preparing W/O/W emulsions.     

多西他赛pH敏感嵌段共聚物胶束的制备

本文在合成pH敏感两亲性嵌段共聚物聚(2-乙基-2-噁唑啉)-聚乳酸(PEOz-PDLLA)的基础上，采用薄膜分散法制备多西他赛pH敏感嵌段共聚物胶束，利用芘荧光探针技术测定胶束的临界胶束浓度(CMC)；通过高效液相色谱测定胶束的载药量及包封率；分别利用透射电镜、动态光散射法和zeta电位分析仪对胶束的形态、粒径和表面电位进行了表征；采用透析法考察了载药聚合物胶束的体外释放行为。结果表明，胶束的临界胶束浓度值为1.0×10^-3 g·L^-1；载药量可达15.0%，包封率为91.1%；胶束的粒度分布很窄，平均粒径为28.7nm；胶束粒子为圆球形且分散良好，其表面zeta电位值为(1.19±0.12)mV；在pH 7.4释放介质中，多西他赛胶束具有缓释作用；而在pH 5.0条件下，胶束释药明显加快，体现出PEOz-PDLLA胶束释药行为的pH敏感性。综合上述研究可见，PEOz-PDLLA嵌段共聚物胶束作为疏水性抗肿瘤药物的给药系统具有很好的应用前景。     

Formulation Development and Antitumor Activity of a Filter-Sterilizable Emulsion of Paclitaxel

Purpose. Paclitaxel is currently administered i.v. as a slow infusion of asolution of the drug in an ethanol:surfactant:saline admixture. However,poor solubilization and toxicity are associated with this drug therapy.Alternative drug delivery systems, including parenteral emulsions, areunder development in recent years to reduce drug toxicity, improveefficacy and eliminate premedication. Methods. Paclitaxel emulsions were prepared by high-shearhomogenization. The particle size of the emulsions was measured by dynamiclight scattering. Drug concentration was quantified by HPLC and invitro drug release was monitored by membrane dialysis. The physicalstability of emulsions was monitored by particle size changes in boththe mean droplet diameter and 99% cumulative distribution. Paclitaxelpotency and changes in the concentration of known degradants wereused as chemical stability indicators. Single dose acute toxicity studieswere conducted in healthy mice and efficacy studies in B16 melanomatumor-bearing mice. Results. QW8184, a physically and chemically stable sub-micronoil-in-water (o/w) emulsion of paclitaxel, can be prepared at high drugloading (8-10 mg/mL) having a mean droplet diameter of <100 nmand 99% cumulative particle size distribution of <200 nm. In vitro release studies demonstrated low and sustained drug release both inthe presence and absence of human serum albumin. Based on singledose acute toxicity studies, QW8184 is well tolerated both in miceand rats with about a 3-fold increase in the maximum-tolerated-dose(MTD) over the current marketed drug formulation. Using the B16mouse melanoma model, a significant improvement in drug efficacywas observed with QW8184 over Taxol^®. Conclusions. QW8184, a stable sub-micron o/w emulsion of paclitaxelhas been developed that can be filter-sterilized and administered i.v.as a bolus dose. When compared to Taxol^®, this emulsion exhibitedreduced toxicity and improved efficacy most likely due to thecomposition and dependent physicochemical characteristics of the emulsion.     

他克莫司阳离子微乳原位凝胶的制备及体外释放研究

目的 为了改善他克莫司水溶性差、眼部生物利用度低的问题,研制了他克莫司阳离子微乳原位凝胶,并研究其体外药物释放行为,为后期进一步研究提供基础。方法 通过高压均质法制得他克莫司阳离子纳米乳,并将其分散于泊洛沙姆407和泊洛沙姆188中制备他克莫司阳离子微乳原位凝胶。采用无膜溶出模型研究其体外释放行为。结果 采用玻璃瓶倒置法测定胶凝温度,筛选出最优凝胶基质处方为26%泊洛沙姆407和12%泊洛沙姆188;体外释药结果显示凝胶溶蚀速率是决定体外释药速率的关键。结论 成功制备了他克莫司阳离子微乳原位凝胶,其体外释药稳定,能满足眼用制剂要求,展现出良好的眼部应用前景。     

Preparation and in vitro evaluation of polylactic acid-mitomycin C microcapsules

Abstract

An emulsion method was developed for the incorporation of water-soluble mitomycin C into polylactic acid biodegradable microcapsules. With an average particle size of about 95 μm, microcapsules with a desired loading of from 3.65 to 13.80 per cent were prepared. These microcapsules, which contained both crystalline and finely dispersed drug particles, showed a dose-dependent drug release pattern with microcapsules of higher drug loading having a faster release rate than those of lower drug loading. Effective sterilization of the microcapsules for parenteral use was achieved by ⁶⁰Co γ-ray irradiation, which did not affect the microcapsule structure, release rate or drug stability. Mitomycin C showed dose-dependent antiproliferative activity against the growth of the K562 human erythroleukaemia cells. The microencapsulated dosage form of mitomycin C was found to enhance the drug's activity through sustained drug release. In experiments where drug concentrations in the cell medium were reduced according to the drug's biological half-life, the microcapsule systems showed a distinct advantage over the non-capsulated dose for the kinetic inhibition of K562 cell growth.