含原酸酯基团的pH敏感纳米载体在抗肿瘤药物递送中的应用进展

pH敏感型纳米药物载体在癌症治疗方面的研究正受到越来越多的关注,显示出诸多优势和良好的应用前景。已报道的pH敏感型纳米药物载体包括多种类型。本文针对含原酸酯基团的pH敏感纳米药物载体,综述了其近年来的研究进展,并介绍了该类药物载体在抗肿瘤药物递送中的应用。     

Synthesis and characterization of pH-sensitive glycopolymers for oral drug delivery systems

pH-sensitive hydrogels are suitable candidates for oral delivery of therapeutic peptides and proteins, due to their ability to respond to environmental pH changes. New pH-sensitive glycopolymers have been developed by free-radical photopolymerization of methacrylic acid and 2- methacryloxyethyl glucoside, using tetra(ethylene glycol) dimethacrylate as a cross-linking agent. To determine the suitability of these hydrogels as carriers for oral drug delivery devices, their swelling behavior was investigated as a function of the pH and copolymer compositions, and various structural parameters such as the number-average molecular weight between cross-links, M _c, the mesh size, ξ, and the cross-linking density, ρ _x, were calculated. The transition between the swollen and the collapsed states of these hydrogels was at a pH of 5. The swelling ratios of the hydrogels increased at pH values above 5. The mesh sizes of the hydrogels were between 18 and 35 Å in the collapsed state (at pH 2.2) and between 70 and 111 Å in the swollen state (at pH 7.0). Finally, as the cross-linking ratio of the copolymer increased, the swelling ratio of the hydrogels decreased at both pH 2.2 and 7.0.     

Monitoring intracellular pH changes in response to osmotic stress and membrane transport activity using 5-chloromethylfluorescein

Intracellular free H⁺ concentration (pHi) responds to numerous extracellular stimuli. The use of fluorescent indicator dyes to measure pHi is strongly influenced by the ability of target cells to retain activated dye within the cytoplasmic compartment. Here, 3 pH-sensitive indicator dyes—acetoxymethyl (AM) esters of SNARF-1 and BCECF, and the thiol-reactive 5-chloromethyfluorescein (CMFDA)—were examined for monitoring pHi. The stability of pH measurements was strongly affected by temperature, cell type, indicator dye, and use of transport inhibitors to prevent dye export. Cellular retention of CMFDA, which forms covalent complexes, was sufficient to permit monitoring of transient pHi changes over extended time periods in a multi-well plate assay format. In human embryonic kidney (HEK293) and Chinese hamster ovary (CHO) cells, increasing osmotic pressure caused a significant rise in pHi. In contrast, activation of native or transfected β-adrenergic, cholinergic, and d and m opioid receptors did not measurably affect pHi in HEK293 cells. Decreases in pHi were observed in CHO cells expressing the human H⁺/peptide transporter PEPT1 upon addition of dipeptide substrates. The use of CMFDA in multi-well formats should facilitate study of osmotic and transport activity and screening for drugs that affect pHi.     

雷替曲塞pH敏感脂质体的制备研究

目的 制备雷替曲塞pH敏感脂质体，并优化其处方和制备工艺，对所优化的pH敏感脂质体进行评价。方法 采用单因素考察和正交设计试验优化处方，考察最优处方制得的雷替曲塞pH敏感脂质体的粒径、Zeta电位、外观形态、包封率、体外释放度和细胞毒性作用。结果 按最优处方制备的雷替曲塞pH敏感脂质体，平均粒径为(227.0±21.4)nm，PDI为0.223±0.061，Zeta电位为(-44.2±3.6)mv，包封率为(58.3±2.1)%；体外释放结果表明载药脂质体在pH5.0和pH6.0的释放介质中释放快速，在pH7.4的释放介质中释放缓慢，pH敏感作用明显；细胞毒性试验证实脂质体载体本身安全性较高，而载药脂质体制剂有较高的细胞毒性。结论 本研究表明，优化得到的雷替曲塞pH敏感脂质体具有简便的制备方法、适宜的理化性质和较高的安全性，具有广阔的临床应用前景。     

Physical hydrogels with self-assembled nanostructures as drug delivery systems

Introduction: As an essential complement to chemically crosslinked hydrogels, drug delivery systems based on physical hydrogels with self-assembled nanostructures are gaining increasing attention, owing to potential advantages of reduced toxicity, convenience of in situ gel formation, stimuli-responsiveness, reversible sol-gel transition, and improved drug loading and delivery profiles.

Areas covered: In this review, drug delivery systems based on physical hydrogels are discussed according to their self-assembled nanostructures, such as micelles, layer-by-layer constructs, supramolecular inclusion complexes, polyelectrolyte complexes and crystalline structures. The driving forces of the self-assembly include hydrophobic interaction, hydrogen bonding, electrostatic interaction, π–π stacking and weak van der Waals forces. Stimuli-responsive properties of physical hydrogels, including thermo- and pH-sensitivity, are considered with particular focus on self-assembled nanostructures.

Expert opinion: Fabricating self-assembled nanostructures in drug delivery hydrogels, via physical interactions between polymer–polymer and polymer–drug, requires accurately controlled macro- or small molecular architecture and a comprehensive knowledge of the physicochemical properties of the therapeutics. A variety of nanostructures within hydrogels, with which payloads may interact, provide useful means to stabilize the drug form and control its release kinetics.     

pH敏感型魟鱼软骨多糖眼用原位凝胶兔眼药动学及其抑制角膜新生血管的研究

目的：制备pH敏感型魟鱼软骨多糖眼用原位凝胶剂（RCG凝胶）并考察其兔眼药动学和抑制角膜新生血管作用。方法：以卡波姆940和HPMC（1∶4, w/w）为辅料制得pH敏感型原位凝胶。取健康家兔30只,向兔眼中滴入50 μL RCG凝胶,分别于给药10,30,60,120,180 min后处死家兔,收集兔眼玻璃体、房水、角膜和虹膜,并测定药物含量。取家兔20只,建立角膜新生血管模型并随机分为4组,分别给予生理盐水,25,50,100 mg·mL^-1 RCG凝胶。观察给药后第3,6,9,12天新生血管面积及角膜病理切片。结果：魟鱼软骨多糖在玻璃体、房水、角膜和虹膜的药动学均符合二室模型,在玻璃体、房水、角膜和虹膜中的C_max分别为（1.35±0.41）,（9.31±0.39）,（27.78±0.32）,（15.97±0.13） μg·mL^-1;AUC_0-180分别为（80.54±9.65）,（571.91±18.32）,（1 763.72±48.66）,（1 034.55±33.87） μg·mL^-1·min。对照组、低、中、高剂量组在第12天的新生血管面积分别为（30.00±3.45）,（24.31±3.12）,（5.36±1.24）,（4.89±1.09） mm²。角膜病理切片中,对照组和低剂量组中有大量炎性细胞浸润,新生血管较多;而中剂量和高剂量组中角膜中炎性细胞和新生血管明显较少。结论：制备了一种pH敏感型魟鱼软骨多糖眼用原位凝胶,该凝胶给药后在角膜部位具有最大的药物浓度,其给药剂量高于50 mg·mL^-1时,具有显著的抑制新生血管生成的作用,该原位凝胶剂具有较好的临床应用价值。     

HPAN/SPI水凝胶纤维的PH刺激响应性能

探索了聚丙烯腈(PAN)和大豆分离蛋白(SPI)在NaOH水溶液中进行PAN碱解，然后挤到凝固浴中凝固、交联，制备水解聚丙烯腈(HPAN)／SPI水凝胶纤维的方法。通过测定凝胶纤维的平衡溶胀伸长率和溶胀伸长率，观察到HPAN／SPI水凝胶纤维的滞后和可逆的伸长／收缩行为，同时在不同组成的凝胶纤维中，随着PAN含量的逐渐增大，水凝胶纤维的响应速率呈现由小到大然后减小的变化规律，当mPAN／mspt=6／4时有最好的响应性能。     

Long-circulating, pH-sensitive liposomes sterically stabilized by copolymers bearing short blocks of lipid-mimetic units

A major hurdle towards in vivo utilization of pH-sensitive liposomes is their prompt sequestration by reticuloendothelial system and hence short circulation time. Prolonged circulation of liposomes is usually achieved by incorporation of pegylated lipids, which have been frequently reported to deteriorate the acid-triggered release. In this study we evaluate the ability of four novel nonionic copolymers, bearing short blocks of lipid-mimetic units to provide steric stabilization of DOPE:CHEMs liposomes. The vesicles were prepared using the lipid film hydration method and extrusion, yielding liposomes of 120–160 nm in size. Their pH-sensitivity was monitored via the release of encapsulated calcein. The incorporation of the block copolymers at concentration up to 10 mol% did not deteriorate the pH-sensitivity of the liposomes. A selected formulation was tested for stability in presence of 25% human plasma and proved to significantly outclass the plain DOPE:CHEMs liposomes. The ability of calcein-loaded liposomes to deliver their cargo inside EJ cells was investigated using fluorescent microscopy and the results show that the surface-modified vesicles are as effective to ensure intracellular delivery as plain liposomes. The pharmacokinetics and organ distribution of a selected formulation, containing a copolymer bearing four lipid anchors was investigated in comparison to plain liposomes and PEG (2000)–DSPE stabilized liposomes. The juxtaposition of the blood clearance curves and the calculated pharmacokinetic parameters show that the block copolymer confers superior longevity in vivo. The block copolymers utilized in this study can be consider as promising sterically stabilizing agents for pH-sensitive liposomes.     

Modifying matrix micro-environmental pH to achieve sustained drug release from highly laminating alginate matrices

Lamination of alginate matrix tablet at acidic pH can compromise its function as a sustained release carrier. This phenomenon is associated with the conversion of sodium alginate to alginic acid. An innovative approach for controlling the release of a highly water-soluble drug from such matrices is presented in this paper. Inclusion of pH-modifiers was employed to raise the micro-environmental pH within matrices undergoing dissolution at gastric pH. The changes in micro-environmental pH of hydrating alginate matrices were visualized with the aid of a pH-indicator and subsequently quantified using image analysis. Transient elevation in micro-environmental pH impeded alginate protonation and minimized or prevented matrix lamination, contributing to preservation of drug diffusion barrier. Significant reduction in the rate of drug release at pH 1.2 was achieved in the presence of such additives. The action of pH-modifiers was synergistically enhanced in the presence of a carbon dioxide barrier formed by effervescing sodium bicarbonate, reducing drug release in the acidic medium from 60 to 20%. Further insight into the influence of lamination on drug release from alginate compacts was given.     

薄膜包衣法制备中药复方结肠定位定时片

目的应用薄膜包衣法制备复方盐酸小檗碱结肠定位定时片。方法以肠溶丙烯酸树脂Eudragit L100与Eudragit S100为pH敏感层材料,以乙基纤维素水分散体(Surelease)为时滞层包衣材料,采用包衣锅包衣法制成结肠定位定时片;以体外释放度为考察指标,使包衣片释药特性基本符合设计要求。结果体外释放度试验表明,当pH敏感层增重4%、时滞层增重6%时,可控制药物在到达小肠后3h释药,且不受胃排空的影响。结论通过调整时滞层、肠溶层包衣厚度,包衣片可基本达到结肠定位释药的预期效果。