Preparation and Characterization of Dextran Magnetite-Incorporated Thermosensitive Liposomes: An on-line Flow System for Quantifying Magnetic Responsiveness

Purpose. Dextran magnetite (DM)-incorporated thermosensitive liposomes, namely thermosensitive magnetoliposomes (TMs), were prepared and characterized in order to investigate their possibility for magnetic drug targeting. Methods. TMs containing calcein were prepared at various DM concentrations by reverse-phase evaporation of dipalmitoylphosphatidylcholine (DPPC). They were evaluated for their physicochemical properties including size, DM capture, magnetite distribution within liposomes, and temperature-dependent calcein release. Moreover, a novel on-line flow apparatus with a sample injector, a coil of tubing placed in an electromagnet, and a fluorescence detector was developed for quantifying the magnetic responsiveness of TMs. This device allowed us a real-time measurement of percentage holding of TMs by magnetic field. Results. Due to water-soluble property of DM, higher contents of magnetite up to 490 mg per mmol DPPC were successfully incorporated into the liposomes with DM than with conventional magnetite (Fe₃O₄). Thermosensitivity and lipid integrity of TMs were not influenced by inclusion of DM. Using the on-line flow system, percentage holding of TMs by magnetic field was shown to vary with several factors; it increases as the magnetic field strength increases, the fluid flow rate decreases, the magnetite content increases, and the liposome concentration increases. Typically, at 490 mg incorporated magnetite per mmol DPPC, 0.5 ml/min-fluid flow rate, and high magnetic field strength (10 kiloGauss), approximately 100% of TMs were found to be held. Conclusions. The TMs were suggested to be useful in future cancer treatment by magnetic targeting combined with drug release in response to hyperthermia.     

可生物降解的注射用药物传递系统研究进展

目的在大量文献的基础上对可注射的体内半固态药物传递系统进行综述 ,指出它们作为局部植入药物传递系统所存在的优、缺点及其前景。方法根据在体内获得固态化的机制不同 ,介绍形成这些系统的不同方法及类型。结果与结论这些系统主要是由可生物降解材料制成的 ,具有生物相容性好、应用方便、可局部给药、延缓药物释放等优点 ,促进了新型药物传递系统的发展     

温度敏感原位凝胶中药物的扩散行为温度敏感原位凝胶中药物的扩散行为

环境敏感凝胶对外界物理或化学条件的微小变化发生响应的性质在药物控制释放领域得到广泛应用.原位凝胶(in situ gel)是指高分子材料的溶液因温度[1,2]、离子强度[3]或pH[4]的改变而在用药部位发生相转变,形成的半固体制剂.由于完美地融合了液体与凝胶制剂的优点,该药物传递系统近年来已逐步发展成为环境敏感凝胶最受瞩目的分支.     

PEG-g-chitosan thermosensitive hydrogel for implant drug delivery: cytotoxicity,in vivo degradation and drug release

Thermosensitive hydrogels based on chitosan are of great interests for injectable implant drug delivery. The poly(ethylene glycol)-grafted-chitosan (PEG-g-CS) hydrogel was reported as a potential thermosensitive system. The objective of the present study is to evaluate the cytotoxicity, in vivo degradation and drug release of PEG-g-CS hydrogel. Cytotoxicity was evaluated using L929 murine fibrosarcoma cell line. Degradation and drug release in vivo were investigated by subcutaneous injection of the hydrogel into Sprague-Dawley rats. PEG-g-CS polymer exhibits no significant cytotoxicity when its concentration is less than 3 mg mL^?1. After being implanted, PEG-g-CS hydrogel maintains its integrity for two weeks and collapses, merging into the tissue, in the third week. It causes moderate inflammatory response but no fibrous encapsulation around the hydrogel is found. The hydrogel presents a three-week sustained release of cyclosporine A with no significant burst release in vitro and produces the effective drug concentration in blood for more than five weeks in vivo, performing almost the same bioavailability to chitosan/glycerophosphate hydrogel. Further modifications of PEG-g-CS hydrogel might be necessary to modulate the degradation and to mitigate the fluctuations in blood drug concentration.     

Role of N-vinyl-2-pyrrolidinone on the thermoresponsive behavior of PNIPAm hydrogel and its release kinetics using dye and vitamin-B12 as model drug

Temperature-sensitive hydrogels hold great promise in biological applications as they can respond to changes in physiological temperature to produce a desired effect like controlled drug delivery. In this study, a series of poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidinone) thermosensitive hydrogels were synthesized by radical copolymerization of NIPAm with 1-vinyl-2-pyrrolidinone (NVP). By altering the initial NIPAm/NVP mole ratios, copolymers were synthesized to have their own distinctive lower critical solution temperature which was established using differential scanning calorimetry. The swelling behavior of the hydrogel was analyzed gravimetrically and it was observed that reswelling rate increases with increasing NVP mole ratio. Further characterizations of the hydrogels were performed using Fourier transform infrared spectroscopy and scanning electron microscopy. Release kinetics with respect to temperature was studied using methylene blue dye solution and vitamin B12. Kinetic modeling of the release profile revealed that the release mechanism is a non-Fickian diffusion mechanism. These results suggested that this material has potential application as intelligent drug carriers. The quantities of residual monomers in the PIV4 hydrogel were determined by HPLC method, and the results show almost complete conversion.     

缓释TGF-β3的去细胞软骨微丝/温敏型水凝胶复合支架的制备

目的：探讨一种可注射且能缓释TGF-β3的去细胞软骨微丝/温敏型水凝胶复合支架的制备方法。方法：使用去污剂-酶化学消化法和层层自组装技术制备缓释TGF-β3 的去细胞软骨微丝,混入温敏型水凝胶后制成缓释TGF-β3的去细胞软骨微丝/温敏型水凝胶复合支架,用ELISA试剂盒检测TGF-β3缓释情况;然后再将骨髓间充质干细胞（BMSCs）与复合支架共培养,显微镜下观察细胞生长情况,Western blot法检测Collagen II（Col II）、Aggrecan（AGG）和SOX9表达水平。结果：复合支架在低温状态下为溶胶状态,当温度升高至37 ℃时变为凝胶状态;复合支架中的TGF-β3 可有效缓释25 d左右;BMSCs在复合支架上生长情况良好,细胞呈现类似软骨细胞的形态,Col II、AGG和SOX9 的表达较对照组显著增加（P ＜0.05）。结论：成功制备了一种可注射且能缓释TGF-β3的去细胞软骨微丝/温敏型水凝胶复合支架,该支架能较好地诱导BMSCs成软骨分化。     

蛇床子素温敏型原位凝胶的研制及含量测定

目的：蛇床子素温敏型凝胶剂的研制,并建立其含量测定方法。方法建立用HPLC法测定制剂的含量及体外释药量。采用搅拌子法测定相变温度并测定其动态黏度,从而确定处方。用转篮法进行处方的体外释放实验。结果确定蛇床子素温敏型凝胶的最佳基质配比是质量分数为25%的泊洛沙姆407和质量分数为10%的泊洛沙姆188的组合。结论该制剂制备工艺简单,进入体内形成凝胶并且24 h累计释放药物约83%。含量测定方法操作简便、快速准确。     

星点设计-效应面法优选磷酸川芎嗪鼻用原位凝胶基质处方的研究

目的：比较3种不同类型磷酸川芎嗪鼻用原位凝胶与人工鼻液混合后的胶凝行为,筛选合适的凝胶基质类型,再以星点设计-效应面法确定基质的优选处方配比。方法：以凝胶强度与胶凝速度为指标,选出合适的磷酸川芎嗪原位凝胶基质类型。再以基质处方中主要成分及増黏剂含量为自变量,基质与人工鼻液混合后的胶凝温度为因变量,采用星点设计-效应面法优选制剂处方,并进行处方验证。结果：指标与因素之间采用二项式拟合,r²=0.978 7,优选处方P407用量为20.11%,P188用量为6.94%,PEG600用量为2.01%,3批验证样品胶凝温度均在32~34℃之间,说明二次模型拟合效果良好。结论：采用优选处方制备的温敏型磷酸川芎嗪鼻用原位凝胶具有理想的胶凝温度,星点设计-效应面法所建立的基质配比影响胶凝温度的数学模型具有良好的拟合精度与数据预测性。     

Synthesis and Characterization of Thermosensitive Poly(N‐Vinyl Caprolactam)‐Grafted‐Aminated Alginate Hydrogels

Thermosensitive hydrogels are characterized by the drastic and reversible change of their physical properties with temperature. Herein is presented the development of a thermosensitive poly(N‐vinylcaprolactam)‐grafted‐aminated alginate (PNVCL‐g‐Alg‐NH₂) having a temperature‐dependent phase transition close to physiological temperature. The hybrid copolymer is formed through the combinational use of chemical and physical methods, that is, carbodiimide chemistry, and ionotrophic gelation by calcium cations. PNVCL‐g‐Alg‐NH₂ exhibits a phase transition at ≈35 °C, and temperature‐dependent water uptake. Copolymerization with PNVCL leads to a decrease in the water uptake of aminated alginate, while improving its thermal stability. Model protein (bovine serum albumin) release from PNVCL‐g‐Alg‐NH₂ scaffolds indicates a higher rate of release below the lower critical solution temperature (LCST) than that of the above, owing to the fact that PNVCL chains collapse at above the LCST and forms a more compact network. In vitro cytotoxicity and hemocompatibility analyses confirm that PNVCL‐g‐Alg‐NH₂ scaffolds are basically non‐cytotoxic and non‐hemolytic.