The potential of Pluronic polymeric micelles encapsulated with paclitaxel for the treatment of melanoma using subcutaneous and pulmonary metastatic mice models

The increasing global incidence of malignant melanoma combined with the poor prognosis and low survival rates of patients necessitates the development of new chemotherapeutic strategies. Thus, the objective of this present study was to investigate the therapeutic efficacy of Pluronic polymeric micelles encapsulating paclitaxel (PTX) in both B16F10 melanoma subcutaneous mice model and pulmonary metastatic mice model. Herein, we developed a PTX-loaded polymeric micelles (PF-PTX) consisting of Pluronic P 123 and F127 block copolymers with small particle size (～25 nm), high encapsulation efficiency (>90%), good stability in lyophilized form and pH-dependent in vitro release. Furthermore, influence of PF-PTX on in vitro cytotoxicity was determined by MTT assay using B16F10 melanoma cell line, while cellular distribution of PF-PTX was detected by confocal microscopy. Additionally, C57BL/6 mice bearing subcutaneous or pulmonary B16F10 melanoma tumors were treated with Taxol or PF-PTX, and antitumor effect was compared. It was found that antitumor efficacy of PF-PTX in both tumor models showed significant tumor growth delay and increased survival. In summary, the simple Pluronic-based nanocarrier could be harnessed for the delivery of anticancer drug to melanoma, with increased therapeutic index.     

Synergistic effect of folate-mediated targeting and verapamil-mediated P-gp inhibition with paclitaxel -polymer micelles to overcome multi-drug resistance

Multidrug resistance (MDR) in tumor cells is a significant obstacle for successful cancer chemotherapy. Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) is a key factor contributing to the development of tumor drug resistance. Verapamil (VRP), a P-gp inhibitor, has been reported to be able to reverse completely the resistance caused by P-gp. For optimal synergy, the drug and inhibitor combination may need to be temporally colocalized in the tumor cells. Herein, we investigated the effectiveness of simultaneous and targeted delivery of anticancer drug, paclitaxel (PTX), along with VRP, using DOMC-FA micelles to overcome tumor drug resistance. The floate-functionalized dual agent loaded micelles resulted in the similar cytotoxicity to PTX-loaded micelles/free VRP combination and co-administration of two single-agent loaded micelles, which was higher than that of PTX-loaded micelles. Enhanced therapeutic efficacy of dual agent micelles could be ascribe to increased accumulation of PTX in drug-resistant tumor cells. We suggest that the synergistic effect of folate receptor-mediated internalization and VRP-mediated overcoming MDR could be beneficial in treatment of MDR solid tumors by targeting delivery of micellar PTX into tumor cells. As a result, the difunctional micelle systems is a very promising approach to overcome tumor drug resistance.     

Poly(caprolactone)-modified Pluronic P105 micelles for reversal of paclitaxcel-resistance in SKOV-3 tumors

Three poly(caprolactone)-modified Pluronic P105 polymers (P105/PCLs) were synthesized using commercially available ε-caprolactone monomers and Pluronic P105 copolymers. The chemical structures, compositions and molecular weights of the P105/PCLs were confirmed by FT-IR, (1)H NMR and GPC measurements. Three paclitaxel (PTX)-loaded P105/PCL polymeric micelles were then prepared, and they showed average diameters in the range of 30-150 nm, drug-loading coefficients of 0.15%-5.43%, and encapsulation ratios of 2.1%-76.53%. The in vitro cytotoxicity assay demonstrated that three PTX-loaded P105/PCL micelles were able to sensitize the resistant SKOV-3/PTX tumor cells. The PTX-loaded P105/PCL(50) micelle was then selected for an in vivo antitumor efficacy study. The tumor volumes in nude mice bearing s.c. resistant SKOV-3/PTX carcinoma treated with this micellar PTX were significantly less than the control group treated with Taxol. It was demonstrated that three PCL-modified P105 monomers and micelles inhibited P-gP efflux activity in the resistant SKOV-3/PTX cells via at least three intracellular events: 1) inhibition of ATPase of P-gP, 2) decrease of membrane microviscosity and 3) a loss of mitochondrial membrane potential and subsequent decrease of ATP levels at the concentration of monomers (0.001%) and/or micelles (0.01-1.0%). Considering other favorable characteristics, such as sustained PTX release in vitro, long-circulating time in vivo and increased PTX concentration in the tissues of ovaries and uterus in mice, the PCL-modified Pluronic P105 polymeric micelle system could have important clinical implications for delivery of paclitaxel and treatment of the resistant ovarian tumors.     

Roles of ligand and TPGS of micelles in regulating internalization,penetration and accumulation against sensitive or resistant tumor and therapy for multidrug resistant tumors

There are several obstacles in the process of successful treatment of malignant tumors, including toxicity to normal cells, inefficiency of drug permeation and accumulation into the deep tissue of solid tumor, and multidrug resistance (MDR). In this work, we prepared docetaxel (DTX)-loaded hybrid micelles with DSPE–PEG and TPGS (TPGS/DTX-M), where TPGS serves as an effective P-gp inhibitor for overcoming MDR, and active targeting hybrid micelles (FA@TPGS/DTX-M) with targeting ligand of folate on the hybrid micelles surface offering active targeting to folate receptor-overexpressed tumor cells. A systematic comparative evaluation of these micelles on cellular internalization, sub-cellular distribution, antiproliferation, mitochondrial membrane potential, cell apoptosis and cell cycle, permeation and inhibition on 3-dimensional multicellular tumor spheroids, as well as antitumor efficacy and safety assay in vivo were well performed between sensitive KB tumors and resistant KBv tumors, and among P-gp substrate or not. We found that the roles of folate and TPGS varied due to the sensitivity of tumors and the loaded molecules in the micelles. Folate and folate receptor-mediated endocytosis played a leading role in internalization, permeation and accumulation for sensitive tumors and non-substrates of P-gp. On the contrary, TPGS played the predominant role which dramatically decreased the efflux of drugs both when the tumor is resistant and for P-gp substrate. These findings are very meaningful for guiding the design of carrier delivery system to treat tumors. The antitumor efficacy in xenograft nude mice model and safety assay showed that the TPGS/DTX-M and FA@TPGS/DTX-M significantly exhibited higher antitumor activity against resistant KBv tumors than the marketed formulation and normal micelles owing to the small size (approximately 20 nm), hydrophilic PEGylation, TPGS inhibition of P-gp function, and folate receptor-modified endocytosis, permeation and accumulation in solid tumor, as well as synergistic effects of DTX-induced cell division inhibition, growth restraint and TPGS-triggered mitochondrial apoptosis in tumor cells. In conclusion, folate-modified TPGS hybrid micelles provide a synergistic strategy for effective delivery of DTX into KBv cells and overcoming MDR.     

The mechanism of enhancement on oral absorption of paclitaxel by N-octyl-O-sulfate chitosan micelles

The overall objective of the present investigation was to demonstrate the effect of N-octyl-O-sulfate chitosan (NOSC) micelles on enhancing the oral absorption of paclitaxel (PTX) in vivo and in vitro, and identify the mechanism of this action of NOSC. In vivo, the oral bioavailability of PTX loaded in NOSC micelles (PTX-M) was 6-fold improved in comparison with that of an orally dosed Taxol(?). In the Caco-2 uptake studies, NOSC micelles brought about a significantly higher amount of PTX accumulated in Caco-2 cells via both clathrin- and caveolae-mediated endocytosis, and NOSC had the effect on inhibiting PTX secreted by P-glycoprotein (P-gp), which was also proved by the studies on rhodamine 123 incorporated in NOSC micelles, fluorescence labeled micelles. The mechanism of NOSC on P-gp inhibition was demonstrated in connection with interfering the P-gp ATPase by NOSC rather than reducing the P-gp expression. Moreover, NOSC with the concentration approaching the critical micellar concentration (CMC) had the strongest effect on P-gp inhibition. In the Caco-2 transport studies, the presence of verapamil and NOSC both improved the transport of Taxol(?), which further certified the effect of NOSC on P-gp inhibition, and PTX-M enhanced the permeability of PTX compared with Taxol(?). The apparent permeability coefficient (Papp) of PTX-M decreased significantly at 4 °C in comparison with at 37 °C, which indicated a predominant active endocytic mechanism for the transport of PTX-M, a P-gp-independent way. Furthermore, the transcytosis of PTX-M was via clathrin-mediated rather than caveolae-mediated. In addition, the transepithelial electrical resistance (TEER) of Caco-2 cell monolayers had no significant change during the transport study, which pointed out that NOSC had no effect on opening the intercellular tight junctions. Based on the obtained results, it is suggested that NOSC micelles might be a potentially applicable tool for enhancing the oral absorption of P-gp substrates.     

载紫杉醇PLGA/F68纳米粒逆转多药耐药用于乳腺癌的治疗

目的载紫杉醇聚乳酸聚羟基乙酸共聚物（PLGA）/F68纳米粒逆转耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞多药耐药的可行性研究。方法使用超声乳化溶剂挥发法分别制备载紫杉醇PLGA和载紫杉醇PLGA/F68纳米粒（10%）,并对载紫杉醇纳米粒进行表征。载紫杉醇纳米粒的体外释放研究使用高效液相色谱进行分析。最后研究载紫杉醇纳米粒在耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞的细胞摄取和细胞毒性（PLGA/F68组、PLGA组和泰素组）。结果纳米粒呈球形,表面粗糙多孔,平均粒径250 nm左右,粒径分布比较窄,体外药物释放呈双相释放模型。载紫杉醇PLGA/F68纳米粒能够被耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞摄取。载紫杉醇PLGA/F68纳米粒比载紫杉醇PLGA纳米粒（P〈0.05）和泰素（TaxolR）（P〈0.05）有更高的细胞毒性。结论载紫杉醇PLGA/F68纳米粒能够逆转耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞的多药耐药,药用辅料Pluronic F68在乳腺癌治疗中具有潜在的应用前景。     

A functional drug delivery platform for targeting and imaging cancer cells based on Pluronic F127

Functional polymeric micelles play an important role in the efficient delivery of therapeutic drugs into tumours. In this study, a functional drug delivery platform with ligands for targeting and fluorescent imaging was designed based on Pluronic F127 (PF127). Using folic acid (FA) and fluorescein isothiocyanate (FITC) to chemically conjugate with PF127, two functional polymers, Pluronic F127-FA (PF127-FA) and Pluronic F127-FITC (PF127-FITC), were synthesized. Solasodine-loaded micelles were then prepared via the thin-film hydration method. By employing A549 and HeLa cells, the results of in vitro cell assays performed using confocal laser scanning microscopy and flow cytometry suggested that the proposed micelles could provide the desired specific targeting and fluorescent imaging functions. In addition, the results of in vitro cytotoxicity experiments showed that the growth inhibition rates of A549 and HeLa cells treated with solasodine-loaded micelles were remarkably higher than those of cells treated with free solasodine. Solasodine-loaded micelles exhibited a more distinct inhibitory effect against HeLa cells than against A549 cells. Thus, an effective drug delivery system for targeting and imaging cancer cells was developed.     

Reversing multidrug resistance by intracellular delivery of Pluronic P85 unimers

Pluronics have been demonstrated as excellent multidrug resistance (MDR) reversal agent in the form of unimers rather than micelles. However, the effective intracellular delivery of Pluronic^® unimers to MDR cancer cells still remains a big challenge. To address this issue, a mixed micellar system based mainly on the pH-sensitive copolymer of poly (l-histidine)-poly (d,l-lactide)-polyethyleneglycol-poly (d,l-lactide)-poly (l-histidine) (PHis-PLA-PEG-PLA-PHis) and Pluronic^® F127, some of which was conjugated with folate, was constructed to intracellularly deliver the unimers of Pluronic^® P85 to MDR cells. The folate-mediated endosomal pH-sensitive mixed micelles (pH_endoSM-P85/f) were prepared by a thin-film hydration method, by which Pluronic^® P85 unimers and doxorubicin (DOX) were incoporated into the mixed micelles. The incorporation of Pluronic^® P85 unimers was investigated by the surface tension test. The results indicated that the Pluronic^® P85 unimers probably first inserted into the binary mixed micelles and then formed a triple-component mixed micelles with Pluronic^® F127 and PHis-PLA-PEG-PLA-PHis as the loading content increased. Further analyzed with flow cytometry, confocal laser scanning microscopy (CLSM) and MTT assay, the micelles with inserted Pluronic^® P85 unimers demonstrated much more cellular uptake and higher cytotoxicity against MDR cells than the triple-component mixed micelles and plain Pluronic^® micelles. The enhanced MDR reversal effect was attributed to the successful intracellular delivery of Pluronic^® P85 unimers to the MDR cells, which was confirmed by the subcellular colocalization of Pluronic^® P85 unimers with mitochondria, the decreased ATP energy and mitochondrial membrane potential (MP) in the MCF-7/ADR cells. The pH_endoSM-P85/f/DOX also demonstrated more dramatic antitumor efficiency and remarkable reduction of ATP energy in the MDR cells in tumors than the control formulations. The intracellular delivery of Pluronic^® P85 unimers to the MDR cells based on the targeted and endosomal pH triggerd release mixed micelles has been demonstrated as a promising approach to reverse MDR.     

Self-aggregated pegylated poly (trimethylene carbonate) nanoparticles decorated with c(RGDyK) peptide for targeted paclitaxel delivery to integrin-rich tumors

Cyclic RGD peptide-decorated polymeric micellar-like nanoparticles (MNP) based on PEGylated poly (trimethylene carbonate) (PEG-PTMC) were prepared for active targeting to integrin-rich cancer cells. An amphiphilic diblock copolymer, α-carboxyl poly (ethylene glycol)-poly (trimethylene carbonate) (HOOC-PEG-PTMC), was synthesized by ring-opening polymerization. The c(RGDyK) ligand, a cyclic RGD peptide that can bind to the integrin proteins predominantly expressed on the surface of tumor cells with high affinity and specificity, was conjugated to the NHS-Activated PEG terminus of the copolymer. The c(RGDyK)-functionalized PEG-PTMC micellar nanoparticles encapsulating PTX (c(RGDyK)-MNP/PTX) was fabricated by the emulsion/solvent evaporation technique and characterized in terms of morphology, size and zeta potential. Cellular uptake of c(RGDyK)-MNP/PTX was found to be higher than that of MNP/PTX due to the integrin protein-mediated endocytosis effect. In vitro cytotoxicity, cell apoptosis and cell cycle arrest studies also revealed that c(RGDyK)-MNP/PTX was more potent than those of MNP/PTX and Taxol. Pharmacokinetic study in rats demonstrated that the polymeric micellar nanoparticles significantly enhanced the bioavailability of PTX than Taxol. In vivo multispectral fluorescent imaging indicated that c(RGDyK)-MNP/PTX had high specificity and efficiency in tumor active targeting. Therefore, the results demonstrated that c(RGDyK)-decorated PEG-PTMC MNP developed in this study could be a potential vehicle for delivering hydrophobic chemotherapeutic agents to integrin-rich tumors.     

Role of cellular uptake in the reversal of multidrug resistance by PEG-b-PLA polymeric micelles

Understanding the processes involved in the cellular uptake of nanoparticles is critical for developing effective nano drug delivery systems. In this paper we found that PEG-b-PLA polymeric micelles firstly interacted with cell membrane using atomic force microscopy (AFM) and then released their core-loaded agents into the cell membrane by fluorescence resonance energy transfer (FRET). The released agents were internalized into the cells via lipid raft/caveolae-mediated endocytosis using total internal reflection fluorescence microscopy (TIRFM) and endocytic inhibitors. Further studies revealed that paclitaxel (PTX)-loaded PEG-b-PLA micelles (M-PTX) increased the cellular accumulation of PTX in PTX-resistant human ovarian cell line A2780/T which resulted in more apoptosis as measured by flow cytometry and the cleavage of poly (ADP-ribose) polymerase (PARP) compared with free PTX. PEG-b-PLA micelles inhibited P-glycoprotein (Pgp) function and Pgp ATPase activity but had no effect on Pgp protein expression. The membrane microenvironment studies showed that PEG-b-PLA micelles induced cell membrane depolarization and enhanced membrane microviscosity. These results suggested that PEG-b-PLA micelles might inhibit Pgp function to reverse multidrug resistance (MDR) via interaction with cell membrane to affect the membrane microenvironment. This study provides a foundation for understanding the mechanism of reversing MDR by nanoparticles better and designing more effective nano drug carriers.     

Targeted and intracellular delivery of paclitaxel using multi-functional polymeric micelles

Natural paclitaxel (Taxol) is an effective anti-cancer drug, although a critical disadvantage is its non-targeting nature. To address this issue, cholesterol-grafted poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-co-undecenoic acid) was synthesized with different starting monomer ratios via a free radical copolymerization route. Folate was subsequently attached to the hydrophilic segment of the polymer in order to target folate receptors-overexpressing cancer cells. The success of synthesis was confirmed with 1H-NMR carried out in CDCl3/D2O. Using a membrane dialysis method, the polymer was then self-assembled into micelles whose hydrophobic cores could be utilized to encapsulate paclitaxel, an extremely hydrophobic compound. The polymer had a low CMC of approximately 20 mg/L in water. Dynamic light scattering further showed that the sizes of blank micelles formed from the polymer were below 180 nm at different pH values tested and approximately 220 nm upon drug incorporation. More importantly, it was demonstrated that the micelles exhibited a useful pH-induced thermo-sensitivity, such that drug was released more rapidly at pH 5.0 (acidic endosomal/lysosomal environment) than at pH 7.4 (normal extracellular pH). In vitro cytotoxicity assays performed against KB cells then provided concluding evidences that the cellular uptake of micelles surface-functionalised with folate was indeed enhanced due to a receptor-assisted endocytosis process. This novel polymeric design thus has the potential to be a useful paclitaxel vehicle for the treatment of folate-receptor positive cancers.     

Folate-functionalized polymeric micelles for tumor targeted delivery of a potent multidrug-resistance modulator FG020326

To overcome multidrug resistance (MDR) existing in tumor chemotherapy, polymeric micelles encoded with folic acid on the micelle surface were prepared with the encapsulation of a potent MDR modulator, FG020326. The micelles were fabricated from diblock copolymers of poly(ethylene glycol) (PEG) and biodegradable poly(epsilon-caprolactone) (PCL) with folate attached to the distal ends of PEG chains. The folate-conjugated copolymers, folate-PEG-PCL, were synthesized by multistep chemical reactions. First, allyl-terminated copolymer (allyl-PEG-PCL) was synthesized through a ring-opening polymerization of epsilon-caprolactone in bulk employing monoallyl-PEG as a macroinitiator. Second, the allyl terminal groups of copolymers were converted into primary amino groups by a radical addition reaction, followed by conjugation of the carboxylic group of folic acid. In vitro studies at 37 degrees C demonstrated that FG020326 release from micelles at pH 5.0 was faster than that at pH 7.4. Cytotoxicity studies with MTT assays indicated that folate-functionalized and FG020326-loaded micelles resensitized the cells approximately five times more than their folate-free counterparts (p < 0.01) in human KB(v200) cells treated with vincristine (VCR). The in vitro Rhodamine 123 efflux experiment using MDR KB(v200) cells revealed that when cells were pretreated with folate-attached and FG020326-loaded micelles, the P-glycoprotein (P-gp) drug efflux function was significantly inhibited.     

Shell-crosslinked Pluronic L121 micelles as a drug delivery vehicle

Pluronic block copolymers (PBCs) have been shown to reverse multidrug resistance (MDR) by inhibiting the P-glycoprotein (P-gp) pump in cancer cells. One of the problems encountered with the use of PBCs is that the micelles disassociate at low concentrations. The study focused on the stabilization of PBC L121 micelles by the formation of crosslinks within their outer shells. To form crosslinks, the two terminal alcohols on L121 were first chemically converted into aldehydes (L121-CHO) using the Dess-Martin periodinane. Diamine compounds were then used to bridge the converted aldehyde termini on L121-CHO via conjugated Schiff bases. After crosslinking, the morphology of the L121 micelles remained spherical in shape and the mean particle sizes of the micelles before and after crosslinking were comparable (100nm). After exposure of MDR KBv cells to free rhodamine-123 (R123), the accumulation of R123 in cells was limited due to the function of P-gp. In contrast, crosslinking of L121 micelles within their outer shells significantly reduced their critical micelle concentration and greatly enhanced their stability, while maintaining their ability to inhibit P-gp function in resistant cells. The results indicated that the L121 micelles with shell crosslinks may be useful as a drug delivery vehicle for cancer chemotherapy.     

Inhibition of MDR1 gene expression and enhancing cellular uptake for effective colon cancer treatment using dual-surface-functionalized nanoparticles

Nanomedicine options for colon cancer therapy have been limited by the lack of suitable carriers capable of delivering sufficient drug into tumors to cause lethal toxicity. To circumvent this limitation, we fabricated a camptothecin (CPT)-loaded poly(lactic-co-glycolic acid) nanoparticle (NP) with dual-surface functionalization—Pluronic F127 and chitosan—for inhibiting multi-drug resistant gene 1 (MDR1) expression and enhancing tumor uptake. The resultant spherical NPs-P/C had a desirable particle size (∼268 nm), slightly positive zeta-potential, and the ability to efficiently down-regulate the expression of MDR1. In vitro cytotoxicity tests revealed that the 24 and 48 h IC₅₀ values of NPs-P/C1 were 2.03 and 0.67 μm, respectively, which were much lower than those for free CPT and other NPs. Interestingly, NPs-P/C1 showed the highest cellular uptake efficiency (approximately 85.5%) among the different drug formulations. Most importantly, treatment of colon tumor-bearing mice with various drug formulations confirmed that the introduction of Pluronic F127 and chitosan to the NP surface significantly enhanced the therapeutic efficacy of CPT, induced tumor cell apoptosis, and reduced systemic toxicity. Collectively, these findings suggest that our one-step-fabricated, dual-surface-functionalized NPs may hold promise as a readily scalable and effective drug carrier with clinical potential in colon cancer therapy.     

紫杉醇聚合物胶束及其抗肿瘤活性研究

目的 以聚己内酯-聚乙二醇-聚己内酯（PCL-PEG-PCL）为载体材料,制备载紫杉醇聚合物胶束,并评价其对EMT-6乳腺癌的抗肿瘤效果.方法 采用薄膜-超声法制备载紫杉醇聚合物胶束并对其进行表征;采用差示扫描热分析法（DSC）分析紫杉醇在载药聚合物胶束中的分散状态;采用MTT法研究紫杉醇聚合物胶束对EMT-6乳腺癌细胞的细胞毒性;建立荷EMT-6乳腺癌小鼠模型,以市售紫杉醇注射液为对照,研究紫杉醇聚合物胶束的体内抗肿瘤活性.结果 紫杉醇聚合物胶束为表面粗糙的球形,具有明显核壳结构,平均粒径为93nm;DSC研究结果表明,将紫杉醇制成缓释纳米粒后其结晶状态发生了变化,以无定型状态存在于聚合物胶束中;MTT研究表明,在相同紫杉醇含量下,紫杉醇聚合物胶束的细胞毒性低于市售紫杉醇／聚氧乙烯蓖麻油注射剂;体内抗肿瘤活性研究表明,紫杉醇聚合物胶束对小鼠EMT-6乳腺癌具有明显抑制作用,相同给药剂量下其抑瘤效果优于紫杉醇注射剂（肿瘤抑制率：85.79％ vs 63.37％,P＜0.05）.结论 制备的载紫杉醇聚合物胶束高效低毒,是一种有潜力的可用于肿瘤治疗的纳米载药体系.     

Prevention of postsurgical tissue adhesion by anti-inflammatory drug-loaded pluronic mixtures with sol-gel transition behavior

Sol-gel transition temperature-controllable Pluronic F127/F68 mixtures including mildly crosslinked alginate and nonsteroidal anti-inflammatory drug (ibuprofen) were prepared to evaluate their potential as tissue adhesion barrier gels. The sol-gel transition temperatures of the Pluronic mixtures could be controlled by adjusting F127/F68 ratio and polymer concentration. The mildly crosslinked alginate with still flow property provided the residence stability of Pluronic mixture gels in the body. Ibuprofen was loaded in Pluronic mixtures to reduce inflammatory response in the body and, thus, to prevent tissue adhesion. The gelation temperatures of the Pluronic mixtures were not affected by the alginate but lowered by the addition of ibuprofen. The in vitro drug release behavior and in vivo peritoneal tissue adhesion of the Pluronic mixtures with the sol-gel transition just below body temperatures were investigated. The drug release behavior from the ibuprofen (1 wt%)-loaded Pluronic mixture gels at 37 degrees C was examined using a membrane-less dissolution model. The drug in the mixture gels was released continuously up to about 45-65% of the total loading amount during the first 7 days. For in vivo evaluation of tissue anti-adhesion potential, the Pluronic mixtures with/without drug were coated on the peritoneal wall defects of rats and their tissue adhesion extents and tissue reactions (inflammatory response, granulation tissue formation, and toxicity in organs) were compared. It was observed that ibuprofen has a positive effect for the peritoneal tissue anti-adhesion. The Pluronic F127/F68/alginate/ibuprofen mixture gel (25 wt% of F127/F68 [7/3], 1 wt% ibuprofen) was highly effective for the prevention of peritoneal tissue adhesion and showed a relatively low inflammatory response and non-toxicity, and thus can be a good candidate material as a coatable or injectable tissue adhesion barrier gel.     

Anti-tumor Activity of Biodegradable Polymer-Paclitaxel Conjugate Micelles on Lewis Lung Cancer Mice Models

Two kinds of paclitaxel (PTX) conjugate nanomicelles were prepared for cell apoptosis and anti-tumor activity evaluation on Lewis lung cancer mice models. One (PTX micelles) was prepared by self-assembling the PTX-conjugate co-polymer, poly(ethylene glycol)-b-poly(L-lactide-co-2-methyl-2-carboxyl-propylene carbonate/PTX), and the other (FA–PTX micelles) was by co-assembling a mixture of the folic acid (FA)-carrying co-polymer poly(ethylene glycol)-b-poly(L-lactide-co-2,2-dihydroxylmethyl-propylene carbonate/FA) (PEG-b-P(LA-co-DHP/FA)), and the PTX-conjugate co-polymer. At 7 and 14 days after tail intravenous injection, the mice were killed. The inhibition rates of tumor growth for PTX and FA–PTX micelles were 50 and 90%, respectively, on the day 7, and 33 and 71%, respectively, on the day 14 after drug injection. Flow cytometry analysis showed that the cell apoptosis rates were 43, 54 and 72% for the control group, PTX micelles group and FA–PTX micelles group, respectively, on the day 7, and 16, 25 and 42 on the day 14. With the TUNEL assay, the grey values of PTX micelles and FA–PTX micelles groups were determined to be 61–62% and 43–44%, of that of the control group, on day 7 or day 14, respectively. Therefore, the PTX micelles and the FA–PTX composite micelles significantly inhibited the subcutaneously inoculated Lewis lung cancer and effectively induced the cell apoptosis, and the FA–PTX composite micelles displayed a better efficacy than the PTX-micelles, implying the contribution of the folate-mediated targeting and endocytosis effect.     

Improved reverse thermo-responsive polymeric systems

Novel reverse thermo-responsive (RTG) polymeric systems displaying superior rheological properties were generated by polymerization of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) segments. Two basic synthetic pathways were followed: (1) The bulk polymerization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock (Pluronic(RTM) F127) (MW=12,600, 70wt% PEO) with hexamethylene diisocyanate (HDI) and (2) The covalent binding of poly(ethylene glycol) and poly(propylene glycol) chains, using phosgene as the connecting molecule. While in the former, the basic amphiphilic F127 repeating unit is known for its own RTG behavior, the latter polymers consist of segments unable of exhibiting reverse thermal gelation of their own. These new materials achieved viscosities at least 15 times higher than F127, at 37 degrees C. Dynamic light scattering measurements revealed that the microstructures formed by these novel polymers were markedly larger than those generated by PEO-PPO-PEO triblocks. While the size of Pluronic F127 micelles ranged from 15 to 20nm, the higher molecular weight amphiphiles generated much larger nanostructures (20-400nm). Finally, the ability of reverse thermo-sensitive gels to perform as drug delivery systems was exemplified by releasing an anti-restenosis model drug (RG-13577). A 30% P[F127](4) gel delivered the drug over 40 days, whereas a F127 gel having the same concentration released the drug over a 7 days period.     

Self-assembled pH-responsive hyaluronic acid–g-poly(l-histidine) copolymer micelles for targeted intracellular delivery of doxorubicin

Hyaluronic acid (HA) was conjugated with hydrophobic poly(l-histidine) (PHis) to prepare a pH-responsive and tumor-targeted copolymer, hyaluronic acid–g-poly(l-histidine) (HA-PHis), for use as a carrier for anti-cancer drugs. The effect of the degree of substitution (DS) on the pH-responsive behaviour of HA-PHis copolymer micelles was confirmed by studies of particles of different sizes. In vitro drug release studies demonstrated that doxorubicin (DOX) was released from HA-PHis micelles in a pH-dependent manner. In vitro cytotoxicity assays showed that all the blank micelles were nontoxic. However, MTT assay against Michigan Cancer Foundation-7 (MCF-7) cells (overexpressed CD44 receptors) showed that DOX-loaded micelles with a low PHis DS were highly cytotoxic. Cellular uptake experiments revealed that these pH-responsive HA-PHis micelles taken up in great amounts by receptor-mediated endocytosis and DOX were efficiently delivered into cytosol. Moreover, micelles with the lowest DS exhibited the highest degree of cellular uptake, which indicated that the micelles were internalized into cells via CD44 receptor-mediated endocytosis and the carboxylic groups of HA are the active binding sites for CD44 receptors. Endocytosis inhibition experiments and confocal images demonstrated that HA-PHis micelles were internalized into cells mainly via clathrin-mediated endocytosis and delivered to lysosomes, triggering release of DOX into the cytoplasm. These results confirm that the biocompatible pH-responsive HA-PHis micelles are a promising nanosystem for the intracellular targeted delivery of DOX.     

Pharmacokinetics, biodistribution, efficacy and safety of N-octyl-O-sulfate chitosan micelles loaded with paclitaxel

Paclitaxel (Taxol), PTX) is a promising anti-cancer drug and has been successfully used to treat a wide variety of cancers. Unfortunately, serious clinical side effects are associated with it, which are caused by PTX itself and non-aqueous vehicle containing Cremophor EL. Development of new formulation of PTX with better efficacy and fewer side effects is extremely urgent. In the present study, a N-octyl-O-sulfate chitosan (NOSC) micelle was developed and used as the delivery system for PTX. The pharmacokinetics, biodistribution, efficacy and safety of PTX-loaded NOSC micelles (PTX-M) were evaluated. The results showed that NOSC micelles had high drug loading capacity (69.9%) and entrapment efficiency (97.26%). The plasma AUC of PTX-M was 3.6-fold lower than that of Taxol; but the V(d) and CL of PTX-M were increased by 5.7 and 3.5-fold, respectively. Biodistribution study indicated that most of the PTX were distributed in liver, kidney, spleen, and lung and the longest retention effect was observed in the lung. Drug safety assessment studies including acute toxicity, hemolysis test, intravenous stimulation and injection anaphylaxis revealed that the PTX-M was safe for intravenous injection. Furthermore, the comparable antitumor efficacy of PTX-M and Taxol was observed at the same dose of 10 mg/kg in in vivo antitumor mice models inoculated with sarcoma180, enrich solid carcinoma (EC), hepatoma solidity (Heps), Lewis lung cancer cells and A-549 human lung cancer cells. These results clearly showed that PTX-M had the similar antitumor efficacy as Taxol, but significantly reduced the toxicity and improved the bioavailability of PTX.