外泌体作为药物递送载体的研究进展

外泌体(exosomes)是一种由细胞分泌的纳米尺度(40~100 nm)的囊泡,在细胞间物质运输和信号交流中发挥重要作用。外泌体在大小和功能上与合成的纳米颗粒类似,但作为天然内源性转运载体,具有毒性低、无免疫原性、渗透性好等优势,故可能成为更有应用前景的药物递送载体。本文主要介绍了外泌体的基本性质和获得方法、载药方法及其作为纳米载体在小分子和生物大分子药物递送和靶向研究中的应用进展情况,并分析探讨了外泌体在载药和靶向递送方面的不足。     

水溶性紫杉醇前药的制备及抗肿瘤活性的研究

目的紫杉醇是具有良好抗肿瘤疗效的化学药物,由于紫杉醇本身化学结构复杂,难溶于水,在一定程度上限制了紫杉醇药物在临床上的广泛应用,因此改善紫杉醇水溶性是解决紫杉醇药物不足的关键问题。方法本实验选用水溶性叶酸配体作为"导向基团",谷氨酸为连接叶酸和紫杉醇的Linker,氨基PEG(MW:350)为药物增溶剂和稳定剂,制备水溶性叶酸-PEG-谷氨酸-紫杉醇前药。用LC-MS鉴定前药的化学结构,通过对前药溶解性及释药动力学曲线的测定,确定前药的理化性质。用MTT实验分析并对比紫杉醇原药与前药在不同肿瘤细胞(MCF-7、MDA-MB-231、A549)和正常细胞HELF(人胚肺成纤维细胞)中的毒性和药效作用。用荧光标记法直观观察紫杉醇前药在肿瘤细胞和组织中的靶向性。结果实验结果证明已成功合成叶酸-PEG-谷氨酸-紫杉醇前药,并具有较好的溶解性和原药释放动力学曲线,细胞实验表明在叶酸受体-配体作用的介导下,叶酸-PEG-谷氨酸-紫杉醇前药靶向叶酸受体高表达的肿瘤细胞,减少对叶酸受体低表达正常细胞的毒副作用。结论叶酸-PEG-谷氨酸-紫杉醇前药具有良好的抗肿瘤活性。     

基于外泌体的抗肿瘤药物靶向递送的研究进展

外泌体是生命体内细胞进行信息传递的重要方式之一,主要的生理病理过程均离不开外泌体的参与,包括细胞耐药、感染传播、肿瘤发展和心血管疾病等。外泌体的生物学职能使其天然具有免疫原性低、递送效率高、可跨过多种生物屏障和具有靶向性等特点,这些优点也促使人们尝试将其用作药物递送载体,以克服一些药物稳定性差、溶解度低、生物利用度不足和毒性较高的缺点。本文介绍了外泌体在抗肿瘤药物递送方面的最新研究进展,包括小分子化疗药物、生物大分子和核酸类药物的递送,还讨论了外泌体的提取、载药及改造方法,并对其应用前景进行了展望。     

紫杉醇前体药物及其研究进展

紫杉醇前体药物较好解决了紫杉醇水溶性差的问题,可避免辅助溶剂聚氧乙烯蓖麻油（Cremophor EL）的毒性问题,因此,临床使用无需抗过敏预处理。其在药代、药效及毒副反应方面具有明显优势,临床应用前景良好。本文综述近年来紫杉醇前体药物的研发及其临床应用进展。     

前体药物的研究进展

前体药物的出现为新药研发开辟了新的途径,前药能够优化药物传输,提高靶向作用,增强治疗效果,因而日益受到重视。本文综述了近年来前药在心血管系统药物、透皮药物、神经系统药物、抗感染药物、抗肿瘤药物的研发与临床应用中所取得的进展。     

新型5-氟尿嘧啶前药的合成与抗肿瘤活性研究

目的寻找新型、高效的5-氟尿嘧啶(5-Fu)前药并测定其抗肿瘤活性。方法在5-氟尿嘧啶的N1和N3位引入具有抗肿瘤活性的取代基,合成其前体药物,利用MTT方法测定其对不同肿瘤细胞的增殖抑制活性。结果合成的6个5-氟尿嘧啶前体药物均显示了较好的肿瘤细胞增殖抑制活性。结论新型5-氟尿嘧啶前药对肿瘤细胞有较好的抑制活性,值得进一步研究。     

N-乙酰基-L-谷氨酰基-泼尼松龙肾靶向前体药物研究

目的通过研究N-乙酰基-L-谷氨酰基-泼尼松龙的体内分布,考察该前体药物的肾靶向性.方法小鼠iv后,采用高效液相法,在规定时间段测定各组织脏器的泼尼松龙浓度, 并采用大鼠骨密度的测定仪确证前体药物的副作用.结果小鼠给药后15 min,前体药物组肾脏中泼尼松龙浓度为(86±8) μg*g-1,泼尼松龙组为(57±4) μg*g-1,60 min后前体药物组肾脏药物浓度为 (67±5) μg*g-1;泼尼松龙组(42±4) μg*g-1.大鼠给药30 d后,股骨的骨密度分别为(0.08±0.03) g*cm-2 (泼尼松龙)和(0.14±0.06) g*cm-2(前体药物组).结论前体药物具有肾靶向性, 并能降低致骨质疏松的副作用.     

聚乙二醇修饰小分子药物的研究进展

聚乙二醇修饰技术是目前药物化学修饰的研究热点,它能够显著提高药物分子水溶性,同时改善药物的药动学和药效学特性,增加了药物临床应用的范围和疗效,具有较好的开发应用前景;但同时也存在诸多问题,有待改进,目前在国内研究相对较少,值得进一步研究开发。本文从聚乙二醇修饰技术被修饰的小分子药物种类、连接臂类型、聚乙二醇载体以及修饰后药物药动学性质和药效学性质改变等方面进行系统综述。     

神经病理性疼痛互联体前药的设计和合成（II）*

目的：合成具有抗神经病理性疼痛的加巴喷丁、普瑞巴林、美金刚胺以及万拉法新的新互联体前药化合物。方法：四种药物通过酯化、酰胺反应由不同的连接子合成酰胺类和混合键类互联体前药。结果：共合成8个新的互联体前药化合物。结论：具有活泼基团的小分子药物能够通过体内容易酶解的化学键（酯键、酰胺键）合成相对分子质量适中的互联体前药。     

紫杉醇前药的研究概况

目的综述了治疗肿瘤的一线药物,紫杉醇前药的研究进展。方法通过查阅近年来国内外的相关文献,选取有代表性的学术期刊,专利进行分析评述。结果利用前药原理设计的小分子前药,高分子聚合物前药,大分子前药等改善了紫杉醇的应用状况。这些前药通过体内特异性的酶或PH值降解释放出原药。结论前药增大了紫杉醇的水溶性,可以达到靶向、控释、缓释的效果,降低毒副作用,提高了抗肿瘤活性,并且很多前药已经进入临床研究阶段。     

Paclitaxel Prodrugs with Sustained Release and High Solubility in Poly(ethylene glycol)-b-poly(ε-caprolactone) Micelle Nanocarriers: Pharmacokinetic Disposition, Tolerability, and Cytotoxicity

Purpose

Develop a Cremophor® and solvent free formulation of paclitaxel using amphiphilic block co-polymer micelles of poly(ethylene glycol)-b-poly(?-caprolactone) (PEG-b-PCL) and characterize their release, solubility, cytotoxicity, tolerability, and disposition.

Methods

Hydrophobic prodrugs of paclitaxel were synthesized via DCC/DMAP or anhydride chemistry to overcome the poor loading (<1% w/w) of paclitaxel in micelles of PEG-b-PCL. Micelles were prepared by a co-solvent extraction technique. A micellar formulation of paclitaxel prodrug (PAX7′C₆) was dosed intravenously to rats (10 mg/kg) and compared to Taxol® (paclitaxel in CrEL:EtOH) and PAX7′C₆ in CrEL:EtOH as controls at the same dose. Pharmacokinetic parameters and tissue distribution were assessed.

Results

Paclitaxel prodrugs had solubilities >5 mg/ml in PEG-b-PCL micelles. Resulting PEG-b-PCL micelles contained 17-22% w/w prodrug and were less than 50 nm in diameter. PEG-b-PCL micelles released paclitaxel prodrugs over several days, t_1/2>3 d. Only the 7′derivative of paclitaxel with the shortest acylchain 7′hexonoate (PAX7′C₆) maintained cytotoxic activity similar to unmodified paclitaxel. PAX7′C₆ micelles demonstrated an increase in area under the curve, half-life, and mean residence time while total clearance and volume of distribution decreased.

Conclusions

Paclitaxel prodrugs in PEG-b-PCL micelle nanocarriers augment the disposition and increase tolerability making further studies on tumor efficacy warranted.     

Pure redox-sensitive paclitaxel–maleimide prodrug nanoparticles: Endogenous albumin-induced size switching and improved antitumor efficiency

A commercial albumin-bound paclitaxel nano-formulation has been considered a gold standard against breast cancer. However, its application still restricted unfavorable pharmacokinetics and the immunogenicity of exogenous albumin carrier. Herein, we report an albumin-bound tumor redox-responsive paclitaxel prodrugs nano-delivery strategy. Using diverse linkages (thioether bond and disulfide bond), paclitaxel (PTX) was conjugated with an albumin-binding maleimide (MAL) functional group. These pure PTX prodrugs could self-assemble to form uniform and spherical nanoparticles (NPs) in aqueous solution without any excipients. By immediately binding to blood circulating albumin after intravenous administration, NPs are rapidly disintegrated into small prodrug/albumin nanoaggregates in vivo, facilitating PTX prodrugs accumulation in the tumor region via albumin receptor-mediated active targeting. The tumor redox dual-responsive drug release property of prodrugs improves the selectivity of cytotoxicity between normal and cancer cells. Moreover, disulfide bond-containing prodrug/albumin nanoaggregates exhibit long circulation time and superior antitumor efficacy in vivo. This simple and facile strategy integrates the biomimetic characteristic of albumin, tumor redox-responsive on-demand drug release, and provides new opportunities for the development of the high-efficiency antitumor nanomedicines.KEY WORDS: Paclitaxel, Abraxane, Redox-sensitive, Disulfide bond, Maleimide, Prodrug-based nano-drug delivery systems, Prodrug/albumin nanoaggregates, Breast cancer treatment     

Poly (ethylene glycol) prodrug for anthracyclines via N-Mannich base linker: Design, synthesis and biological evaluation

Poly (ethylene glycol)s (PEGs) are potential drug carriers for improving the therapeutic index of anticancer agents. In this work, a novel methodology for constructing PEG prodrug of anthracycline anticancer drugs was developed based on N-Mannich base of salicylamide and its 2-acyloxymethylated derivative. The resultant conjugates first subjected to in vitro hydrolysis testing, which revealed the release behavior of newly synthesized PEG prodrugs could be adjusted by the status of 2-hydroxy group of salicylamide. These PEG prodrugs also demonstrated superior cytotoxicity in antiproliferative assay. O-blocked doxorubicin prodrug with PEG20k as carrier was selected for further in vivo assessments and presented longer circulating life in pharmacokinetic experiment. This high molecular prodrug was also found to be more efficacious against S-180 xenografted tumor than equivalent amount of doxorubicin.     

Integrated combination delivery of IDO inhibitor and paclitaxel for cancer treatment

In order to realize the combination of chemotherapy and immunotherapy, a reduction-responsive paclitaxel (PTX) prodrug PEG-SS-PTX was synthesized and used as a carrier to encapsulate IDO inhibitor CY-1-4 for preparing PEG-SS-PTX/CY-1-4 NPs. PEG-SS-PTX/CY-1-4 NPs were evaluated by cytotoxicity, immunogenic cell death (ICD) induction ability and anti-tumor efficacy. Dynamic light scattering (DLS) results showed that the size of PEG-SS-PTX/CY-1-4 NPs was about 149 nm. In vitro experiments indicated that its cytotoxicity was in a concentration-dependent manner, and it induced the ICD of B16-F10 cells. In vivo studies in melanoma mouse model indicated that PEG-SS-PTX/CY-1-4 NPs significantly inhibited the tumor growth and reduced the expression of IDO in tumor tissues. Moreover, it increased the rate of CD8⁺ T cells in the spleen. In summary, PEG-SS-PTX/CY-1-4 NPs achieved good anti-tumor effects and reduced the dose of chemotherapy drugs, which was a safe and effective combined delivery system.     

靶向肿瘤微环境的紫杉醇前药研究进展

紫杉醇前药（paclitaxel prodrugs）的设计是一种提高药物制剂成药性、降低其毒副作用、增强抗肿瘤效果的有效手段。随着对前药研究的深入,利用肿瘤过表达的受体、酶、转运蛋白、谷胱甘肽及活性氧自由基以及肿瘤组织弱酸性及低氧环境等作为靶标进行的紫杉醇靶向性前药的研究已取得极大进展。综述近年来以肿瘤微环境特殊的病理与生理特征为靶标的紫杉醇前药的研究进展。     

抗肿瘤前药在肿瘤靶向治疗中的新进展

化疗是临床上治疗肿瘤的主要途径之一,但化疗药物在肿瘤部位的低浓度及系统毒性仍是其临床应用受限的首要问题。前体药物通过对原药的化学结构或药物剂型给予一定修饰,大大克服了化疗药物的缺点,开辟了一条靶向治疗肿瘤的新途径。目前,新发展的抗肿瘤前药有导向酶活化前药、载体前药、脂质前药等,现对其研究进展和应用做一综述。     

Preparation and characterization of water-soluble prodrug, liposomes and micelles of Paclitaxel

Alternative formulations of paclitaxel were developed in order to improve its aqueous solubility, and characterized in vitro. A methacrylic acid based nanoconjugate of paclitaxel was synthesized by a simple esterification reaction with molecular weight of 1657 Da. The in vitro hydrolysis study on the prodrug of paclitaxel in presence of rat plasma has shown that the ester bond was quite stable (less than 1% of paclitaxel was liberated from prodrug in 24 h). This water-soluble prodrug was encapsulated into polyethylene glycol coated liposomes optimized with saturated lipids, to overcome the physical instability associated with paclitaxel. Under in vitro testing, prodrug liposomes seem very impressive with release of only 45% of payload in 180 h. Further, chemical as well as physical stability studies have shown that liposomes were stable without any signs of crystallization of paclitaxel. In addition, paclitaxel was covalently coupled to poloxamer via methacrylic acid linker to obtain a micelle forming conjugate. Evidence for self-assembly of this conjugate into micelles was provided by fluorescence spectroscopy, light scattering and differential scanning calorimetry techniques. Micellization of the conjugate was thermodynamically favored and the core of resulting micelles exhibited higher microviscosities (than poloxamer micelles). Release studies using dialysis technique along with high performance liquid chromatography revealed that paclitaxel is liberated from micelle in the form of methacrylic acid oligomer based prodrug in a gradual manner. These preliminary studies provided indication on the performance and feasibility of testing these carrier systems as a safer alternative to the Cremophor EL based paclitaxel formulation.     

Folate-modified poly(2-ethyl-2-oxazoline) as hydrophilic corona in polymeric micelles for enhanced intracellular doxorubicin delivery

The transmembrane transport of drug loaded micelles to intracellular compartment is quite crucial for efficient drug delivery. In the current study, we investigated the cellular internalization and anticancer activity of doxorubicin loaded micelles with folate modified stealthy PEOz corona. Folate-decorated micelles incorporating doxorubicin were characterized for particle size, degree of folate decoration, drug loading content and encapsulation efficiency, morphology, and surface charge. The targeting capability and cell viability were assessed using HeLa, KB, A549 and MCF-7/ADR cell lines. In vitro study clearly illustrated the folate receptor (FR) mediated targeting of FA modified micelles to FR-positive human HeLa, KB and MCF-7/ADR cells, while specific delivery to FR-negative A549 cells was not apparently increased at the same experimental conditions. Cytotoxicity assay showed 60% and 58% decrease in IC₅₀ values for HeLa and KB cells, while only a slight decrease for A549 cells, following treatment with folate modified formulations. The enhanced intracellular delivery of FA modified micelles in MCF-7/ADR cells was also observed. In vivo antitumor tests revealed DOX entrapped FA-PEOz-PCL micelles effectively inhibited the tumor growth and reduced the toxicity to mice compared with free DOX. The current study showed that the targeted nano-vector improved cytotoxicity of DOX and suggested that this novel PEOz endowed stealthy micelle system held great promise in tumor targeted therapy.     

Enhanced oral bioavailability of paclitaxel in pluronic/LHR mixed polymeric micelles: preparation, in vitro and in vivo evaluation

In order to enhance paclitaxel oral bioavailability, mixed polymeric micelles that comprised of pluronic copolymers and low molecular weight heparin-all-trans-retinoid acid (LHR) conjugate were developed. PTX-loaded mixed polymeric micelles (MPMs) were prepared by dialysis method with high drug loading 26.92 ± 2.08% and 25.82 ± 1.9% for F127/LHR and P188/LHR MPMs respectively, and were found to be spherical in shape with an average size of around 140 nm and a narrow size distribution. In vitro release study showed that pluronic/LHR MPMs exhibited delayed release characteristics compared to Taxol and faster drug release profile compared to LHR plain polymeric micelles (PPMs). The cytotoxic activity of PTX-loaded pluronic/LHR MPMs was slightly higher than LHR PPMs in MCF-7 cells (p<0.01). In situ effective permeability of PTX through rat small intestine was 5- to 6-fold higher with mixed micelles than that of Taxol. Moreover, pluronic/LHR MPMs achieved significantly higher AUC and C(max) level than both of LHR PPMs and Taxol. This enhancement might be due to the inhibition of both P-glycoprotein efflux system and cytochrome P450 metabolism by pluronic copolymers. The current results encourage further development of paclitaxel mixed polymeric micelles as an oral drug delivery system.     

Remote loading paclitaxel–doxorubicin prodrug into liposomes for cancer combination therapy

The combination of paclitaxel (PTX) and doxorubicin (DOX) has been widely used in the clinic. However, it remains unsatisfied due to the generation of severe toxicity. Previously, we have successfully synthesized a prodrug PTX-S-DOX (PSD). The prodrug displayed comparable in vitro cytotoxicity compared with the mixture of free PTX and DOX. Thus, we speculated that it could be promising to improve the anti-cancer effect and reduce adverse effects by improving the pharmacokinetics behavior of PSD and enhancing tumor accumulation. Due to the fact that copper ions (Cu²⁺) could coordinate with the anthracene nucleus of DOX, we speculate that the prodrug PSD could be actively loaded into liposomes by Cu²⁺ gradient. Hence, we designed a remote loading liposomal formulation of PSD (PSD LPs) for combination chemotherapy. The prepared PSD LPs displayed extended blood circulation, improved tumor accumulation, and more significant anti-tumor efficacy compared with PSD NPs. Furthermore, PSD LPs exhibited reduced cardiotoxicity and kidney damage compared with the physical mixture of Taxol and Doxil, indicating better safety. Therefore, this novel nano-platform provides a strategy to deliver doxorubicin with other poorly soluble antineoplastic drugs for combination therapy with high efficacy and low toxicity.