PH-Responsive Micelles Assembled by Three-Armed Degradable Block Copolymers with a Cholic Acid Core for Drug Controlled-Release.
ABSTRACT: One of the most famous anticancer drugs, paclitaxel (PTX), has often been used in drug controlled-release studies. The polymers derived from bio-compound bile acids and degradable poly(ε-caprolactone) (PCL) form a reservoir and have been used as a drug delivery system with great advantages. Herein, we grafted poly(N,N-diethylaminoethyl methacrylate) and poly(poly(ethylene glycol) methyl ether methacrylate) into the bile acid-derived three-armed macroinitiator CA-(PCL)₃, resulting in the amphiphilic block copolymers CA-(PCL-b-PDEAEMA-b-PPEGMA)₃. These pH-responsive three-armed block copolymers self-assembled into micelles in aqueous solution and PTX was encapsulated into the micellar core to form PTX-loaded micelles with a drug loading of 29.92 wt %. The micelles were stable in PBS at pH 7.4 and showed a pH-triggered release behavior of PTX under acidic environments, in which 55% of PTX was released at pH 5.0 in 80 h. These cholic acid-based functionalized three-armed block polymers present good biocompatibility, showing great potential for drug controlled-release.
Project description:The differences in micro-environment between cancer cells and the normal ones offer the possibility to develop stimuli-responsive drug-delivery systems for overcoming the drawbacks in the clinical use of anticancer drugs, such as paclitaxel, doxorubicin, and etc. Hence, we developed a novel endosomal pH-sensitive paclitaxel (PTX) prodrug micelles based on functionalized poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) diblock polymer with an acid-cleavable acetal (Ace) linkage (mPEG-PCL-Ace-PTX). The mPEG-PCL-Ace-PTX₅ with a high drug content of 23.5 wt % was self-assembled in phosphate buffer (pH 7.4, 10 mM) into nanosized micelles with an average diameter of 68.5 nm. The in vitro release studies demonstrated that mPEG-PCL-Ace-PTX₅ micelles was highly pH-sensitive, in which 16.8%, 32.8%, and 48.2% of parent free PTX was released from mPEG-PCL-Ace-PTX₅ micelles in 48 h at pH 7.4, 6.0, and 5.0, respectively. Thiazolyl Blue Tetrazolium Bromide (MTT) assays suggested that the pH-sensitive PTX prodrug micelles displayed higher therapeutic efficacy against MCF-7 cells compared with free PTX. Therefore, the PTX prodrug micelles with acetal bond may offer a promising strategy for cancer therapy.
Project description:Stimuli-responsive drug delivery systems (DDSs) are expected to realize site-specific drug release and kill cancer cells selectively. In this study, a pH-responsive micelle was designed utilizing the pH-sensitivity of borate bonds formed between dopamine and boronic acid. First, methyl (polyethylene glycol)-block-polycaprolactone (mPEG-PCL) was conjugated with 4-cyano-4-(thiobenzoylthio)pentanoic acid (CTP) to obtain a macroinitiator. Two different segments poly(dopamine methacrylamide) (PDMA) and poly(vinylphenylboronic acid) (PVBA) were then grafted to the end of mPEG-PCL. Two triblock copolymers, mPEG-PCL-PDMA and mPEG-PCL-PVBA, were then obtained by reversible addition-fragmentation transfer (RAFT) polymerization. These copolymers and their mixture self-assembled in aqueous solution to form micelles that were able to load hydrophobic anticancer drug doxorubicin (DOX). These two-component micelles were found to be pH-sensitive, in contrast to the one-component micelles. Furthermore, MTT studies showed that the micelles were almost nontoxic. The DOX-loaded micelles showed cytotoxicity equivalent to that of DOX at high concentration. In vivo antitumor experiments showed that this pH-sensitive polymeric micellar system had an enhanced therapeutic effect on tumors. These two-component boronate-based pH micelles are universally applicable to the delivery of anticancer drugs, showing great potential for cancer therapy.
Project description:Polymeric micelles are promising carriers for anti-cancer agents due to their small size, ease of assembly, and versatility for functionalization. A current challenge in the use of polymeric micelles is the sensitive balance that must be achieved between stability during prolonged blood circulation and release of active drug at the tumor site. Stimuli-responsive materials provide a mechanism for triggered drug release in the acidic tumor and intracellular microenvironments. In this work, we synthesized a series of dual pH- and temperature-responsive block copolymers containing a poly(?-caprolactone) (PCL) hydrophobic block with a poly(triethylene glycol) block that were copolymerized with an amino acid-functionalized monomer. The block copolymers formed micellar structures in aqueous solutions. An optimized polymer that was functionalized with 6-aminocaproic acid (ACA) possessed pH-sensitive phase transitions at mildly acidic pH and body temperature. Doxorubicin-loaded micelles formed from these polymers were stable at blood pH (~7.4) and showed increased drug release at acidic pH. In addition, these micelles displayed more potent anti-cancer activity than free doxorubicin when tested in a tumor xenograft model in mice.
Project description:Well-defined novel, linear, biodegradable, amphiphilic thermo-responsive ABA-type triblock copolymers, poly[2-(2-methoxyethoxy) ethyl methacrylate-co-oligo(ethylene glycol) methacrylate]-b-poly(ε-caprolactone)-b-poly[2-(2-methoxyethoxy) ethyl methacrylate-co-oligo(ethylene glycol) methacrylate] [P(MEO₂MA-co-OEGMA)-b-PCL-b-P(MEO₂MA-co-OEGMA)] (tBPs), were synthesized via a combination of ring-opening polymerization (ROP) of ε-caprolactone (εCL) and reversible addition-fragmentation chain transfer polymerization (RAFT) of MEO₂MA and OEGMA comonomers. The chemical structures and compositions of these copolymers were characterized using Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (¹H NMR). The molecular weights of the copolymers were obtained using gel permeation chromatography (GPC) measurements. Thermo-responsive micelles were obtained by self-assembly of copolymers in aqueous medium. The temperature sensitivity and micelllization behavior of amphiphilic triblock copolymers solutions were studied by transmittance, fluorescence probe, surface tension, dynamic light scattering (DLS) and transmission electron microscopy (TEM). A hydrophobic drug, anethole, was encapsulated in micelles by using the dialysis method. The average particle sizes of drug-loaded micelles were determined by dynamic light scattering measurement. In vitro, the sustained release of the anethole was performed in pH 7.4 phosphate-buffered saline (PBS) at different temperatures. Results showed that the triblock copolymer's micelles were quite effective in the encapsulation and controlled release of anethole. The vial inversion test demonstrated that the triblock copolymers could trigger the sol-gel transition which also depended on the temperature, and its sol-gel transition temperature gradually decreased with increasing concentration. The hydrogel system could also be used as a carrier of hydrophobic drugs in medicine.
Project description:We report a red-fluorescent drug delivery system formed by biodegradable and biocompatible amphiphilic A-B-A block copolymers. Each polymer consists of a red fluorescent dye covalently bonded in the middle of hydrophobic block (B) of polylactone, tethered at both ends with poly[(oligo ethylene glycol) methyl ether methacrylate] (POEGMA) as the hydrophilic block. Two types of polylactones, i.e., semicrystalline poly(ε-caprolactone) (PCL) and amorphous poly(δ-decalactone) (PDL), respectively, were incorporated as the hydrophobic segment in the block copolymers. Using transmission electron microscopy, we characterized the self-assembled nanostructures formed by these amphiphilic block copolymers in mixtures of water/tetrahydrofuran or water/dimethylformamide. All of these polymers remained highly fluorescent in water, although some extent of aggregation-induced fluorescence quenching was still observed. Among the three types of polymers presented here, the polymer (RPO-3) containing an amorphous block of PDL showed the highest drug-loading capacity and the largest extent of drug release in acidic media. RPO-3 micelles loaded with doxorubicin as a model of anticancer drug showed sustainable intracellular release and cytotoxicity against HeLa cells.
Project description:Amphiphilic poly(ε-caprolactone)-block-poly[2-(α-d-mannopyranosyloxy) ethyl acrylamide] (PCL-b-PManEA) block copolymers were synthesized via a combination of ring-opening polymerization (ROP), reversible addition-fragmentation chain transfer (RAFT) polymerization and reactive ester-amine reaction. The PCL-b-PManEA block copolymers can self-assemble into micelles and encapsulate anticancer drug doxorubicin (DOX). To enhance mucoadhesive property of the resulting DOX-loaded PCL-b-PManEA micelles, Concanavalin A (ConA) lectin was further conjugated with the micelles. Turbidimetric assay using mucin shows that the DOX-loaded PCL-b-PManEA@ConA micelles are mucoadhesive. DOX release from the DOX-loaded PCL-b-PManEA@ConA micelles in artificial urine at 37 °C exhibits an initial burst release, followed by a sustained and slow release over three days. Confocal laser scanning microscope (CLSM) images indicate that the DOX-loaded PCL-b-PManEA@ConA micelles can be effectively internalized by UMUC3 human urothelial carcinoma cells. The DOX-loaded PCL-b-PManEA@ConA micelles exhibit significant cytotoxicity to these cells.
Project description:To decrease critical micelle concentration (CMC), improve stability, and keep high drug-loading capacity, three pH-sensitive mixed micelles applied for anticancer drug controlled delivery were prepared by the mixture of polymers poly (N,N-diethylaminoethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PDEAEMA-PPEGMA) and polycaprolactone-b-poly (poly(ethylene glycol) methyl ether methacrylate) (PCL-PPEGMA), which were synthesized and confirmed by 1H NMR and gel permeation chromatographic (GPC). The critical micelle concentration (CMC) values of the prepared mixed micelles were low, and the micellar sizes and zeta potentials of the blank mixed micelles demonstrated good pH-responsive behavior. Combined experimental techniques with dissipative particle dynamics (DPD) simulation, the particle sizes, zeta potentials, drug loading content (LC), encapsulation efficiency (EE), aggregation morphologies, and doxorubicin (DOX) distribution of the mixed micelles were investigated, and the high DOX-loading capacity of the mixed micelles was found. Both in vitro DOX release profiles and DPD simulations of the DOX dynamics release process exhibited less leakage and good stability in neutral conditions and accelerated drug release behavior with a little initial burst in slightly acidic conditions. Cytotoxicity tests showed that the polymer PDEAEMA-PPEGMA and the blank mixed micelles had good biocompatibility, and DOX-loaded mixed micelles revealed certain cytotoxicity. These results suggest that the drug-loaded mixed micelles that consisted of the two polymers PDEAEMA-PPEGMA and PCL-PPEGMA can be new types of pH-responsive well-controlled release anticancer drug delivery mixed micelles.
Project description:UNLABELLED:In order to achieve enhanced and synergistic delivery of paclitaxel (PTX), a hydrophobic anticancer agent, two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks, were synthesized. Both POEG-b-PFTS polymers were able to form micelles with intrinsic antitumor activity in vitro and in vivo. Employing these micelles as a carrier to load PTX, their drug loading capacity, stability, in vivo biodistribution and tumor inhibition effect were evaluated. PTX/POEG15-b-PFTS16 mixed micelles exhibited an excellent stability of 9days at 4°C with a PTX loading capacity of 8.2%, which was more effective than PTX/POEG15-b-PFTS6 mixed micelles. In vivo biodistribution data showed that DiR-loaded POEG-b-PFTS micelles were more effectively localized in the tumor than in other organs. Moreover, both PTX/POEG-b-PFTS micelles showed significantly higher antitumor activity than Taxol in a 4T1.2 murine breast tumor model, and the tumor inhibition and animal survival followed the order of PTX/POEG15-b-PFTS16>PTX/POEG15-b-PFTS6>POEG15-b-PFTS16>Taxol?POEG15-b-PFTS6. Our data suggest that POEG-b-PFTS micelles are a promising anticancer drug carrier that warrants more studies in the future. STATEMENT OF SIGNIFICANCE:Polymerization of drug-based monomer represents a facile and precise method to obtain well-defined polymeric prodrug amphiphiles. Currently, most reports largely focus on the synthesis methods and the biophysical properties. There is limited information about their anti-tumor activity and delivery function as prodrug carriers in vitro and in vivo. In this manuscript, we report the development of two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks. Both POEG-b-PFTS polymers were able to self-assemble into nano-sized micelles with intrinsic antitumor activity in vitro and in vivo. More importantly, POEG-b-PFTS polymers were effective in forming stable mixed micelles with various anticancer agents including PTX, DOX, docetaxel, gefitinib, and imatinib. Delivery of PTX via our new carrier led to significantly improved antitumor activity, suggesting effective PTX/FTS combination therapy. We believe that our study shall be of broad interest to the readers in the fields of biomaterials and drug delivery.
Project description:One of the major obstacles that delay the clinical translation of polymeric micelle drug delivery systems is whether these self-assembled micelles can retain their integrity in blood following intravenous (IV) injection. The objective of this study was to evaluate the impact of core functionalization on the thermodynamic and kinetic stability of polymeric micelles. The combination of ring-opening polymerization of N-carboxyanhydride (NCA) with highly efficient "click" coupling has enabled easy and quick access to a family of poly(ethylene glycol)-block-poly(?-R-glutamate)s with exactly the same block lengths, for which the substituent "R" is tuned. The structures of these copolymers were carefully characterized by (1)H NMR, FT-IR, and GPC. When pyrene is used as the fluorescence probe, the critical micelle concentrations (CMCs) of these polymers were found to be in the range of 10(-7)-10(-6) M, which indicates good thermodynamic stability for the self-assembled micelles. The incorporation of polar side groups in the micelle core leads to high CMC values; however, micelles prepared from these copolymers are kinetically more stable in the presence of serum and upon SDS disturbance. It was also observed that these polymers could effectively encapsulate paclitaxel (PTX) as a model anticancer drug, and the micelles possessing better kinetic stability showed better suppression of the initial "burst" release and exhibited more sustained release of PTX. These PTX-loaded micelles exerted comparable cytotoxicity against HeLa cells as the clinically approved Cremophor PTX formulation, while the block copolymers showed much lower toxicity compared to the cremophor-ethanol mixture. The present work demonstrated that the PEG-b-PPLG can be a uniform block copolymer platform toward development of polymeric micelle delivery systems for different drugs through the facile modification of the PPLG block.
Project description:Amphiphilic A2(BC)2 miktoarm star polymers [poly(?-caprolactone)]2-[poly(2-(diethylamino)ethyl methacrylate)-b- poly(poly(ethylene glycol) methyl ether methacrylate)]2 [(PCL)2(PDEA-b-PPEGMA)2] were developed by a combination of ring opening polymerization (ROP) and continuous activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The critical micelle concentration (CMC) values were extremely low (0.0024 to 0.0043 mg/mL), depending on the architecture of the polymers. The self-assembled empty and doxorubicin (DOX)-loaded micelles were spherical in morphologies, and the average sizes were about 63 and 110 nm. The release of DOX at pH 5.0 was much faster than that at pH 6.5 and pH 7.4. Moreover, DOX-loaded micelles could effectively inhibit the growth of cancer cells HepG2 with IC50 of 2.0 ?g/mL. Intracellular uptake demonstrated that DOX was delivered into the cells effectively after the cells were incubated with DOX-loaded micelles. Therefore, the pH-sensitive (PCL)2(PDEA-b-PPEGMA)2 micelles could be a prospective candidate as anticancer drug carrier for hydrophobic drugs with sustained release behavior.