紫杉醇PCL-PEG-PCL温敏性缓释凝胶的制备及性能研究

目的 利用聚己内酯-聚乙二醇-聚己内酯(PCL1250-PEG1500-PCL1250)两亲性聚合物温敏凝胶作为载体材料,构建疏水性抗肿瘤药物紫杉醇的载药体系.方法 以辛酸亚锡为催化剂、聚乙二醇为引发剂,引发己内酯单体开环聚合,合成PCL1250-PEG1500-PCL1250三嵌段共聚物.通过核磁共振氢谱及凝胶渗透色谱对其组成、结构及分子量进行表征:制备不同凝胶浓度及初始载药量的载药温敏凝胶,并对其相转变性能、体外药物释放行为以及体内的生物降解性能进行考察.结果 核磁共振及凝胶渗透色谱测定结果表明:合成的共聚物组成与初始投料比一致,符合设计的PCL1250-PEG1500-PCL1250嵌段聚合物结构;该凝胶在15%～30%浓度区间内,具备温敏性溶胶-凝胶相转变能力;该温敏凝胶对紫杉醇具有可控的药物缓释能力,通过改变凝胶浓度及初始载药量可调节药物释放速率和维持释放的时间.小鼠背部皮下注射PCL1250-PEG1500-PCL1250溶胶后在体内迅速原位凝胶化,凝胶随植入时间逐渐降解至45 d时基本降解完全.结论 PCL1250-PEG1500-PCL1250温敏凝胶作为紫杉醇载药体系具有良好的药物控释能力和体内生物降解性能.     

关节腔注射用甲氨蝶呤温敏性缓释凝胶的制备及性能考察

目的利用聚己内酯-聚乙二醇-聚己内酯（PCL-PEG-PCL）两亲性聚合物温敏凝胶作为载体材料,构建抗类风湿性关节炎药物甲氨蝶呤关节腔注射用给药体系。方法采用开环聚合法,以辛酸亚锡为催化剂、PEG1500为引发剂,与己内酯单体开环聚合得到PCL-PEG-PCL两亲性嵌段共聚物;对得到的PCL-PEG-PCL嵌段共聚物的组成结构及相对分子质量进行表征;采用翻转试管法测定PCL-PEG-PCL聚合物的溶胶-凝胶相转变温度,绘制溶胶-凝胶相转变曲线;评价甲氨蝶呤PCL-PEG-PCL温敏凝胶载药体系的缓释性能;考察PCL-PEG-PCL温敏凝胶关节腔注射后在大鼠体内的生物相容性。结果 PCL-PEG-PCL两亲性嵌段共聚物水溶液具有温敏性溶胶-凝胶相转变能力,其溶胶-凝胶相转变温度介于室温与体温之间。甲氨蝶呤PCL-PEG-PCL温敏凝胶的体外释放研究表明PCL-PEG-PCL温敏凝胶对甲氨蝶呤具有较好的缓释能力,提高载药量和温敏凝胶浓度将减缓甲氨蝶呤从PCL-PEG-PCL温敏凝胶的释放。大鼠滑膜苏木精-伊红染色结果显示,关节腔注射PCL-PEG-PCL温敏凝胶未引起炎症反应发生。结论 PCL-PEG-PCL温敏凝胶作为关节腔局部注射用载药体系具有较好的药物缓释性能和生物相容性。     

紫杉醇聚合物纳米囊泡的制备和体外释放研究

目的 以聚己内酯-b-聚乙二醇-6-聚己内酯（PCEP）两亲性三嵌段共聚物为载体研制紫杉醇聚合物纳米囊泡.方法 以不同分子量的聚乙二醇（PEG）引发合成不同亲水段、疏水段链长的PCEP并进行FT-IR、1H NMR和GPC表征,以合成的嵌段聚合物PCEP为载体,通过薄膜-超声分散法制备紫杉醇聚合物纳米囊泡,用透射电子显微镜（TEM）表征其形态和构造,用粒度分析仪测定其粒径及分布,用高效液相色谱（HPLC）法测定其载药量及包封率,用透析袋法研究药物体外释放;同时,研究不同亲水链长、疏水链长对紫杉醇聚合物囊泡载药量、包封率、粒径及体外释放紫杉醇药物的影响.结果 研制的紫杉醇聚合物囊泡呈核-壳结构球形,粒径为纳米级,随着PCEP共聚物相对分子质量的增加而增大;紫杉醇聚合物囊泡体外释放无突释现象,能稳定缓慢释放紫杉醇,且释放速率随共聚物中亲水段PEG含量增加而增大,随疏水段PCL含量增大而减小.结论 以PCEP两亲性三嵌段共聚物为载体制备的紫杉醇聚合物纳米囊泡,其粒径小且分布均匀,包封率较高,有望成为一种用于提高紫杉醇的药效且降低不良反应的新的紫杉醇缓控释剂型.     

一种可生物降解温度敏感型聚乙二醇-聚己内酯-聚乙二醇水凝胶的合成和表征

合成了一系列分子量较低的聚乙二醇．聚己内酯-聚乙二醇（Poly（ethylene glycol）-Polycaprolactone-Poly（ethylene glycol），PEG-PCL—PEG）三嵌段共聚物。分别采用FTIR和1H—NMR对其结构进行了表征。所合成的PEG-PCL-PEG共聚物具有良好的水溶性，当水溶液浓度高于临界凝胶浓度（Critical gel concentration，CGC）时，随着温度的变化聚合物水溶液会呈现特有的凝胶-溶胶转变。研究了共聚物亲水疏水链段的比例和长度，以及热历史等对凝胶-溶胶转变行为的影响。通过调节上述条件，可以在一定程度上拓宽凝胶-溶胶转变温度范围，有助于PEG—PCL-PEG水凝胶在可注射药物控制释放系统等方面的应用。     

紫杉醇聚己内酯／泊洛沙姆188载药纳米粒及其抗肿瘤活性

目的利用聚己内酯（PCL）与亲水性添加剂泊洛沙姆188（F68）共混物作为载体材料与抗癌药物紫杉醇组成纳米粒缓释载药系统,并评价其在裸鼠人乳腺癌B37实体瘤模型中的抗肿瘤效果。方法采用超声乳化／溶剂挥发法制备紫杉醇PCL/F68载药纳米粒：对紫杉醇PCI／F68载药纳米粒进行表征及高压液相色谱法（HPLC）测定包封率和体外释放度：利用差示扫描热分析（DSC）法分析紫杉醇在PCL／F68载药纳米粒中的分散状态;评价紫杉醇PCL／F68载药纳米粒在裸鼠人乳腺癌B37实体瘤模型中的抗肿瘤活性．结果紫杉醇PCL/F68载药纳米粒呈现规整的球形：平均粒径为150．50nm（标准差25．41nm）．多分散系数为O．18。紫杉醇PCI仃68纳米粒的载药量为18％,药物包封率为84-36％。紫杉醇PCIJF68载药纳米粒体外药物释放研究表明在50d的释放周期内累计释放量约为49％,接近零级释放（R=0．998）。体内抗肿瘤活性实验研究表明．紫杉醇PCL/F68载药纳米粒对裸鼠人乳腺癌B37实体瘤生长具有明显抑制作用。结论肿瘤局部注射紫杉醇PCL/F68载药纳米粒能够有效地抑制肿瘤的生长,     

可生物降解PLA/PCL、PELA/PECL高分子共混体系的早期降解行为——相结构与降解性能的关系

本文以吸水率,GPC、SEM等考察了聚d,1—乳酸(PLA)/聚ε—己内酯(PCL)、聚d,1—乳酸—聚乙二醇(PEG)/聚ε—己内酯—聚乙二醇(PEG)可生物降解共混多相体系的体外降解行为,研究了PH值、共混组成及相容性对降解性能的影响,并就共混物形态结构与降解性能的关系作了讨论。PLA/PCL共混体系,随PLA含量增大,吸水性增强,降解速率加快。PLA/PCL(75/25)共混物表现出较PLA更高的吸水宰,经65天降解,分子量显著下降。由于聚乙二醇链段的亲水性和内增容作用,PELA/PECL(50/50)共混物的吸水率较PLA/PCL(50/50)共混物大为提高。     

对映异构聚乳酸/聚乙二醇空间异构复合水凝胶的药物释放及形貌和细胞毒性

背景：目前生物降解水凝胶已被广泛应用于抗癌药物及生物活性大分子的装载,但为了保护生物活性大分子的活性,需要得到凝胶化条件更温和,凝胶化时间更短的凝胶体系。 目的：制备对映异构聚乳酸∕聚乙二醇的空间异构复合水凝胶,使其具有更短的凝胶化时间,实现对模拟药物溶菌酶的装载和控释。 方法：以聚乙二醇为引发剂,辛酸亚锡为催化剂,丙交酯与聚乙二醇发生开环聚合反应,得到聚乳酸/聚乙二醇的三嵌段共聚物(PLLA-PEG-PLLA 和 PDLA-PEG-PDLA)。用1H NMR,FT-IR 和 XRD表征三嵌段共聚物。10% PLLA20-PEG227-PLLA20的水溶液和10%PDLA21-PEG227-PDLA21的水溶液在室温下混合,12 h后形成凝胶。通过XRD考察凝胶化机制,以溶菌酶为模拟药物,考察凝胶的释药特性,通过扫描电镜考察凝胶的形貌,采用MTT法考察凝胶的细胞毒性。 结果与结论：成功得到聚乳酸/聚乙二醇的三嵌段共聚物,在嵌段共聚物中,聚乳酸嵌段和聚乙二醇嵌段都能结晶,但以聚乙二醇嵌段的结晶为主。通过XRD证明凝胶中存在空间异构复合作用,溶菌酶在凝胶中通过凝胶的溶蚀和降解行为,在7 d之内释放完全。通过扫描电镜观察到冻干的水凝胶呈三维贯穿的多孔结构,空隙尺寸在50~100 μm 之间。鼠成纤维细胞与浓度为100%的凝胶浸提液共培养72 h之后,细胞的存活率为99.3%。     

核交联聚(N-异丙基丙烯酰胺-co-N,N-二甲基丙烯酰胺)-b-聚己内酯胶束及紫杉醇的温敏控制释放行为(英文)

背景:高分子纳米胶束是近几年正在发展的一类新型药物载体,其载药范围广、结构稳定、具有优良的组织渗透性,体内滞留时间长,能使药物有效地到达靶点。而使其带有智能靶向性以及减弱其初期爆发释放行为成为了最近研究的热点。目的:得到一种低临界溶液浓度在40℃左右的智能靶向药物载体,可以通过对温度的改变而改变其药物释放行为,并进一步通过核交联改善胶束的稳定性以及其药物释放行为。方法:通过N-异丙基丙烯酰胺(NIPAAm)和N,N-二甲基丙烯酰胺(DMAAm)的自由基共聚,合成端羟基聚(N-异丙基丙烯酰胺-co-N,N-二甲基丙烯酰胺)(P(NIPAAm-co-DMAAm))。通过调节巯基乙醇和单体的比例,以及NIPAAm和DMAAm的比例,调节P(NIPAAm-co-DMAAm)的相对分子质量和低临界溶液温度。然后在异辛酸亚锡的催化下,利用P(NIPAAm-co-DMAAm)端羟基引发己内酯开环聚合,得到端羟基P(NIPAAm-co-DMAAm)-b-PCL两亲性嵌段共聚物。该嵌段共聚物再与丙烯酰氯反应得到末端带有不饱和双键的两亲性嵌段共聚物。用透析法制备具有不同核交联程度的纳米载药胶束,并对其释放行为进行研究。结果与结论:得到了温敏段相对分子质量为3600、PCL段相对分子质量为1600的两亲性嵌段共聚物,其低临界溶液浓度为42℃。采用不同比例端羟基和端羧基P(NIPAAm-co-DMAAm)-b-PCL混合,制备得到具有不同核交联程度的温敏性纳米载药胶束。胶束的药物释放速度在43℃快于37℃,随着核交联程度的增高,紫杉醇的释放速度变慢。结果提示以低临界溶液浓度在40℃左右的温敏性P(NIPAAm-co-DMAAm)-b-PCL所制备的胶束,具有一定的温敏控制释放行为,药物释放速度可进一步通过核交联程度来控制。     

新型聚己内酯／聚醚嵌段共聚物的合成及其释放蛋白药物的研究

目的合成一种含有活泼环氧基和羟端基的聚己内酯（PCL）／聚醚嵌段共聚物，这个新聚合物具有更理想的亲水性，并可通过与环氧基团的反应进一步衍生化。方法采用双官能团的环氧基化合物作为交联剂，通过化学偶联的方法合成嵌段共聚物，用^1H核磁共振（^1H—NMR）、热分析和接触角测定法表征其结构和性能。通过多官能环氧基化合物将肝素偶联到嵌段共聚物的端羟基上，用讯标记的肝素定量测定肝素的结合量和结合稳定性。采用溶液浇注和压膜方法制备含牛血清蛋白（BSA）的共聚物膜，37℃恒温摇床中进行体外模拟释放，用分光光度法（595nm波长）测定BSA的释放量。结果^1H—NMR测定证明共聚物中环氧基团（EO）对CL单元的比例与原始配方的计算值相符，热分析曲线表明嵌段共聚物有两个吸热峰，证明它具有微观相分离结构。接触角测定表明，随着共聚物中亲水组分的增加其亲水性增加。选择聚醚的类型和比例可以调控其亲水性，嵌段共聚物上化学偶联肝素的量可达到15％，具有明显高于物理混合的结合稳定性和很好的抗凝血活性。共聚物中亲水性聚醚组分的存在促进蛋白质的释放，而且通过改变聚醚片段的组成可以对蛋白质的释放速率进行调控。结论本研究提出了一种合成预设片段长度的聚酯-聚醚嵌段共聚物的新方法，并提供了一类新的肝素化的释放蛋白和多肽类药物的控释新材料。     

聚己内酯-吐温80共聚物纳米粒在神经胶质瘤化疗中的应用

目的 研究新型载多西紫杉醇聚己内酯-吐温80共聚物(PCL-Tween 80)纳米粒在神经胶质瘤化疗中的应用.方法 以PCL-Tween 80和聚己内酯为材料,利用改良的溶剂萃取/挥发方法制备载多西紫杉醇纳米粒并进行性质表征.利用激光共聚焦显微镜观察纳米粒的细胞摄取情况,并利用噻唑蓝(MTT)法测定纳米粒对C6细胞的细胞毒作用.结果 载药纳米粒呈球形,粒径约为200 nm.PCL-Tween 80纳米粒的载药量为10%,28 d内可以释放包裹药物的34.90%.与同浓度的泰素帝(Taxotere(R))比较,载多西紫杉醇PCL-Tween 80纳米粒对C6细胞的细胞毒性作用更强.结论 载多西紫杉醇PCL-Tween 80纳米粒用于神经胶质瘤的化疗极具应用前景.     

Adjustable degradation and drug release of a thermosensitive hydrogel based on a pendant cyclic ether modified poly(ε-caprolactone) and poly(ethylene glycol)co-polymer

The convenient and precise fabrication of drug–hydrogel formulations with satisfactory degradability and a well-controlled drug release profile are crucial factors for injectable hydrogel formulations in clinical applications. Here a new injectable thermosensitive hydrogel formed from poly(ε-caprolactone) (PCL)–poly(ethylene glycol)–poly(ε-caprolactone) amphiphilicco-polymers with 1,4,8-trioxa[4.6]spiro-9-undecanone (TOSUO) moieties incorporated in the poly(ε-caprolactone) (PCL)block (PECT) was constructed to provide a route to tailor the degradation and drug release behavior. The effect of hydrophilic cyclic ether moieties on the degradation of and drug release by PECT hydrogels were evaluated in vitro and in vivo. The results indicated that a freeze-dried powder of paclitaxel-loaded PECT nanoparticles rapidly dissolved in water at ambient temperature with slightly shaking and formed a stable injectable in situ drug–hydrogel formulation at body temperature, which is convenient for clinical operations because it avoids the need for pre-quenching or long-term incubation. The paclitaxel distribution was also more quantitative and homogeneous on entrapping paclitaxel in PECT nanoparticles. Further, the small number of pendant cyclic ether groups in PCL could decrease the cystallinity and hydrophobicity and, as a result, the in vitro and in vivo retention time of PECT hydrogels and the release of entrapped paclitaxel could be tuned from a few weeks to months by varying the amount of PTOSUO in the hydrophobic block. Significantly, paclitaxel-loaded PECT nanoparticles and free paclitaxel could be simultaneously released during the in vitro paclitaxel release from PECT hydrogels. A histopathological evaluation indicated that in vivo injected PECT hydrogels produced only a modest inflammatory response. Thus pendant cyclic ether modification of PCL could be an effective way to achieve the desired degradation and drug release profiles of amphiphilicco-polymer thermosensitive hydrogels and PECT hydrogels may be suitable for local drug delivery.     

Chitosan-based thermosensitive hydrogel as a promising ocular drug delivery system: Preparation, characterization, and in vivo evaluation

The purpose of this study was to evaluate the feasibility of in situ thermosensitive hydrogel based on chitosan in combination with disodium α-d-Glucose 1-phosphate (DGP) for ocular drug delivery system. Aqueous solution of chitosan/DGP underwent sol-gel transition as temperature increased which was flowing sol at room temperature and then turned into non-flowing hydrogel at physiological temperature. The properties of gels were characterized regarding gelation time, gelation temperature, and morphology. The sol-to-gel phase transition behaviors were affected by the concentrations of chitosan, DGP and the model drug levocetirizine dihydrochloride (LD). The developed hydrogel presented a characteristic of a rapid release at the initial period followed by a sustained release and remarkably enhanced the cornea penetration of LD. The results of ocular irritation demonstrated the excellent ocular tolerance of the hydrogel. The ocular residence time for the hydrogel was significantly prolonged compared with eye drops. The drug-loaded hydrogel produced more effective anti-allergic conjunctivitis effects compared with LD aqueous solution. These results showed that the chitosan/DGP thermosensitive hydrogel could be used as an ideal ocular drug delivery system in terms of the suitable sol-gel transition temperature, mild pH environment in the hydrogel as well as the organic solvent free.     

Photoresponsive Coumarin‐Based Supramolecular Hydrogel for Controllable Dye Release

Recently, photoresponsive hydrogels have attracted increasing interest due to their ability to provide precise spatial and temporal control of drug release. Herein, a new kind of coumarin‐based photoresponsive supramolecular hydrogelator without conventional gelation motif is designed and synthesized through a facile one‐pot method. The gelation process, photoresponsiveness, self‐assembly morphology, self‐assembly mechanism, and release kinetics are fully investigated by various characterization methods (e.g., scanning electron microscopy, single crystal X‐ray diffraction, high pressure liquid chromatography, UV–vis spectroscopy). Furthermore, encapsulated methyl violet dye molecules can be precisely released from the hydrogel by manipulating photoirradiation time. The study reveals that the coumarin‐based photoresponsive hydrogel holds great potential as soft materials for controllable drug release.     

Investigation on injectable, thermally and physically gelable poly(ethylene glycol)/poly(octadecanedioic anhydride) amphiphilic triblock co-polymer nanoparticles

A family of injectable, biodegradable and thermosensitive co-polymer nanoparticle (NP) hydrogels based on mPEG-b-POA-b-mPEG, which was synthesized from mono-methoxy poly(ethylene glycol) (mPEG) and poly(octadecanedioic anhydride) (POA), was investigated in this paper. It was found that the aqueous dispersions of these NPs underwent a reversible gel-sol transition upon temperature change. By using paclitaxel and Bovine serum albumin (BSA) as model drugs, we noticed that the in vitro releases of both in situ gel-forming formulations were sustained and no initial burst releases were observed for 7 days. In vitro cytotoxicity tests via MTT assay indicate that mPEG-b-POA-b-mPEG NPs are non-toxic to normal mouse lung fibroblast cells (L929). The in vivo hydrogel formation and in vivo biocompatibility of co-polymer NP hydrogel were also investigated and the results further validate the biocompatible nature of co-polymer NP hydrogel. In conclusion, our mPEG-b-POA-b-mPEG NP hydrogel is able to control the release of incorporated drug for longer duration.     

Injectable drug-delivery systems based on supramolecular hydrogels formed by poly(ethylene oxide)s and alpha-cyclodextrin

Polymeric hydrogels long have attracted interest for biomaterials applications because of their generally favorable biocompatibility. High in water content, they are particularly attractive for delivery of delicate bioactive agents, such as proteins. However, because they require covalent crosslinking for gelation, many hydrogels can be applied only as implantables, and incorporation of drugs by sorption may be time-consuming and limiting with regard to the loading level. Therefore a delivery formulation where gelation and drug loading can be achieved simultaneously, taking place in an aqueous environment and without covalent crosslinking, would be attractive. Herein is described a new class of injectable and bioabsorbable supramolecular hydrogels formed from poly(ethylene oxide)s (PEOs) and alpha-cyclodextrin (alpha-CD) for controlled drug delivery. The hydrogel formation is based on physical crosslinking induced by supramolecular self-assembling with no chemical crosslinking reagent involved. The supramolecular structure of the hydrogels was confirmed with wide-angle X-ray diffraction studies. The gelation kinetics was found to be dependent on the concentrations of the polymer and alpha-CD as well as on the molecular weight of the PEO used. The rheologic studies of the hydrogels showed that the hydrogels were thixotropic and reversible and that they could be injected through fine needles. The components of the supramolecular hydrogels potentially are biocompatible and nontoxic. Drugs can be encapsulated directly into the hydrogels in situ at room temperature without any contact with organic solvents. The supramolecular hydrogels were evaluated in terms of their in vitro release kinetics. The rate-controlling mechanism of macromolecular drug release might be the erosion of the hydrogels.     

Silk fibroin/poly(vinyl alcohol) photocrosslinked hydrogels for delivery of macromolecular drugs

Hydrogels are three-dimensional polymer networks widely used in biomedical applications as drug delivery and tissue engineered scaffolds to effectively repair or replace damaged tissue. In this paper we demonstrate a newly synthesized cytocompatible and drug releasing photo-crosslinked hydrogel based on poly(vinyl alcohol) methacrylate and silk fibroin which possesses tailorable structural and biological properties. The initial silk fibroin content was 0%, 10%, 20%, 30%, 40% and 50% with respect to the weight of poly(vinyl alcohol) methacrylate. The prepared hydrogels were characterized with respect to morphology, crystallinity, stability, swelling, mass loss and cytotoxicity. FITC-dextrans of different molecular weights were chosen as model drugs molecules for release studies from the hydrogels. The hydrogels containing different silk fibroin percentages showed differences in pore size and distribution. X-ray diffraction analysis revealed that amorphous silk fibroin in poly(vinyl alcohol) methacrylate is crystallized to β-sheet secondary structure upon gelation. The sol fraction increased with increasing fibroin concentration in the co-polymer gel (from 18% to 45%), although the hydrogel extracts were non-cytotoxic. Similarly, the addition of silk fibroin increased water uptake by the gels (from 7% to 21%). FITC-dextran release from the hydrogels was dependent on the silk fibroin content and the molecular weight of encapsulated molecules. The study outlines a newer type of photo-crosslinked interpenetrating polymer network hydrogel that possess immense potential in drug delivery applications.     

Protein polymer hydrogels by in situ, rapid and reversible self-gelation

Protein-based biomaterials are an important class of materials for applications in biotechnology and medicine. The exquisite control of their composition, stereochemistry, and chain length offers unique opportunities to engineer biofunctionality, biocompatibility, and biodegradability into these materials. Here, we report the synthesis of a thermally responsive peptide polymer-based hydrogel composed of a recombinant elastin-like polypeptide (ELP) that rapidly forms a reversibly cross-linked hydrogel by the formation of intermolecular disulfide cross-links. To do so, we designed and synthesized ELPs that incorporate periodic cysteine residues (cELPs), and show that cELPs are thermally responsive protein polymers that display rapid gelation under physiologically relevant, mild oxidative conditions. Gelation of cELPs, at concentrations as low as 2.5 wt%, occurs in ≈ 2.5 min upon addition a low concentration of hydrogen peroxide (0.3 wt%). We show the utility of these hydrogels for the sustained release of a model protein in vitro, and demonstrate the ability of this injectable biomaterial to pervade tumors to maximize tumor coverage and retention time upon intratumoral injection. cELPs represent a new class of injectable reversibly cross-linked hydrogels with properties intermediate between ELP coacervates and chemically cross-linked ELP hydrogels that will find useful applications in drug delivery and tissue engineering.     

Controlled release of paclitaxel from biodegradable unsaturated poly(ester amide)s/poly(ethylene glycol) diacrylate hydrogels

Biodegradable hydrogels (FPBe-G) were synthesized by the photopolymerization of two precursors: FPBe, a fumurate-based unsaturated poly(ester amide) (UPEA), and poly(ethylene glycol) diacrylate (PEG-DA). Depending on the feed ratio of these two precursors, the resultant FPBe-G hydrogels showed different crosslinking levels of network structure, mesh sizes (xi) and matrix morphology. When a lipophilic drug, paclitaxel, was preloaded into FPBe-G hydrogels, the two-month drug-release kinetics from FPBe-G hydrogels in both pure PBS buffer and alpha-chymotrypsin media were measured. The paclitaxel-preloaded FPBe-G hydrogels in a alpha-chymotrypsin solution had significantly faster drug release rate than the corresponding hydrogels in a pure PBS buffer due to an enzyme catalyzed biodegradation of FPBe-G hydrogels. Sustained paclitaxel releases over a two-month period without initial burst release were also achieved by using hydrogels having certain feed ratios of hydrogel precursors. These paclitaxel release data correlated well with the molecular mesh size (xi), molecular weight between cross-links (M(c)) and matrix morphological structure of FPBe-G hydrogels.     

Possibility of active targeting to tumor by local hyperthermia with temperature-sensitive nanoparticles

Recently, the concept of drug delivery requires that the release of encapsulated drug be produced only at the diseased site with controllable rates. Given that thermosensitive hydrogels have been widely investigated for controlled delivery based on their phase transition, we speculate that nanoparticles with the novel polymers play a key role in tumor therapy respond to thermal activity. Therefore, we here hypothesize that enhanced delivery of therapeutics might be achieved by conjugation to thermosensitive polymers, in concert with targeted hyperthermia by precisely specifying the phase transition temperature of the thermosensitive polymer. By local hyperthermia at tumor site, a targeted drug delivery system could be obtained, exploiting both the temperature-sensitive and the site-specific behaviors. The proposition may provide a new strategy into the development of a novel drug delivery system for tumor therapy.