DOX-loaded Vesicles Research Articles

In-depth study of anticancer drug diffusion through a cross-linked ­pH-responsive polymeric vesicle membrane

Post-encapsulation and release of the anticancer drug doxorubicin hydrochloride (DOX·HCl) through cell-like transmission functions of polymeric vesicles were studied using cross-linked pH-responsive polymeric vesicles. The vesicles were fabricated for the first time via the redox-initiated reversible addition-fragmentation chain transfer dispersion polymerization in ethanol-water mixture, using 2-(diisopropylamino)ethyl methacrylate and glycidyl methacrylate, and the vesicle membrane was modified post-cross-linking by using ethylenediamine. A phase diagram was constructed for reproducible fabrication of the polymeric vesicles, and well-shaped vesicles were formed when the target degree of polymerization of the hydrophobic polymer chains was equal to or higher than 50 with solid content in the range of 10–30 wt%. The cross-linked vesicle membrane served as a gate enabling “open” and “closed” states in response to pH stimulation. Up to 50% drug loading efficiency and 39% drug loading content could be achieved, and in vitro release of the DOX-loaded vesicles in aqueous buffer solutions showed a much faster DOX release rate at pH 5.0 than at pH 6.5. The polymeric vesicles were of very low cytotoxicity to A549 cells up to the concentration of 2 mg/mL, and the IC50 of DOX-loaded vesicles were higher than that of the free DOX. The intracellular DOX release study indicated higher cellular uptake capability for DOX-loaded vesicles than that of free DOX.

A pH-Responsive Supramolecular Drug Delivery System Constructed by Cationic Pillar[5]arene for Enhancing Antitumor Activity.

Drug delivery systems have good biocompatibiliy and low side effects for cancer treatment, but overcoming high efficiency of drug-loading and the drug-targeting controlled release still remains challenging. In this work, supramolecular vesicles, with pH-triggering effect, have been successfully constructed for drug delivery, which are fabricated by the complexation between a cationic pillar[5]arene (DAWP5) and a sodium dodecyl sulfonate (SDS) in aqueous solution. Drug-loading and releasing results demonstrated that anticancer drug doxorubicin (DOX) could be loaded efficiently by such cationic vesicles in neutral condition, and the drug release could be controlled in the simulated weak acid environment of tumor cells. Moreover, the vesicles had low cytotoxicity to normal human cell (L02), while the DOX-loaded vesicles could significantly enhance the cytotoxicity of free DOX for normal cell L02 and four tested tumor cells (Hela, HepG2, MGC-803 and T24). Especially for HepG2, after 24 h incubation time, IC50 of DOX-loaded vesicles was only 0.79 μM, about 23% of that of DOX (3.43 μM). These results suggested that such novel vesicles have promising potential to construct nano-drug delivery systems for various biomedical applications.

Reversible Self-Assembly Nanovesicle of UCST Response Prepared with Multi-l-arginyl-poly-l-aspartate Conjugated with Polyethylene Glycol.

Multi-L-arginyl-poly-L-aspartate (MAPA), also known as cyanophycin, containing a backbone of polyaspartate with arginine and lysine as side chains, was prepared with recombinant Escherichia coli. The insoluble part (iMAPA) was conjugated with polyethylene glycol (PEG) at two different levels, high (iMAPA(PEG)h) and low (iMAPA(PEG)l). Both levels of conjugation exhibited UCST (upper critical solution temperature)-type responses in the pH range of 3-10 at a concentration of 2 mg/mL. The cloud-point temperature of each conjugate also showed a positive correlation with concentration in PBS, falling between 20 to 58 °C at a concentration from 0.1 to 3 mg/mL. Hysteresis was observed to follow approximate paths under the same condition during repeated heating and cooling. Notably, the reversible formation of core-shell vesicles appeared at room temperature in PBS with a size of around 25 to 60 nm, as measured by DLS and observed under TEM. The reversibility was further employed to encapsulate doxorubicin (Dox) at different weight ratios of Dox to iMAPA(PEG)h. An encapsulation efficiency could reach as high as 70% with an equivalent loading capacity of 1.5 mg Dox/mg iMAPA(PEG)h. The Dox-loaded vesicles stayed stable at 4 °C for up to 4 weeks, with a minimal leakage below 2% and a slightly dilated morphology. Temperature-triggered release of Dox from the vesicles could be achieved by a step change of 5 °C successively from 37 to 62 °C in an effort to induce an initial 10% release at 37 °C gradually to complete release at 62 °C.

Designed construction of tween 60@2β-CD self-assembly vesicles as drug delivery carrier for cancer chemotherapy

We report a simple strategy to prepare Tween 60@2β-CD self-assembly vesicles in aqueous solution as a new drug delivery carrier for cancer chemotherapy. The spherical shape of vesicles was confirmed by transmission electron microscopy (TEM) and mean particle sizes were about 33.7 nm, as measured by dynamic light scattering, micro-IR results indicated that the self-assembly vesicles was driven by hydrogen bonding. Hydrophilic doxorubicin (DOX) was successfully loaded into the self-assembly vesicles with drug loading content of 7.85% and loading efficiency of 42%. In addition, an in vitro cytotoxicity study and cellular uptake assays demonstrated that the DOX-loaded Tween 60@2β-CD vesicles markedly enhanced the cellular uptake and cytotoxicity of DOX toward the Hela cells. Furthermore, when used to evaluate the in vivo therapeutic efficacy in mice bearing the breast cell line (4T1), DOX-loaded vesicles exhibited superior inhibition of tumor growth compared with the DOX solutions.

Dual-Responsive Bola-Type Supra-Amphiphile Constructed from Water-Soluble Pillar[5]arene and Naphthalimide-Containing Amphiphile for Intracellular Drug Delivery.

Supramolecular construction of multistimuli platform for drug delivery is a challenging task. In this work, a pH and GSH (glutathione) dual-responsive bola-type supramolecular amphiphile was successfully fabricated by the complexation between a water-soluble pillar[5]arene (WP5) and a bolaform naphthalimide guest (G) in water. The resulting bola-type amphiphile further self-assembled into supramolecular binary vesicles, which could be disassembled by low pH, a high-GSH-concentration environment, or both. Furthermore, the results of drug loading and releasing tests showed that doxorubicin (DOX), the hydrophobic anticancer drug, could be successfully encapsulated into the Stern region of the obtained supramolecular vesicles and generated the DOX-loaded vesicles with good drug-loading efficiency. Moreover, the obtained DOX-loaded vesicles displayed efficient and rapid DOX release at a simulated tumor microenvironment with low-pH or excess-GSH conditions or both. Significantly, cytotoxicity experiments revealed that the DOX-loaded supramolecular vesicles could obviously improve the anticancer efficiency of free DOX for tumor cells while remarkably reducing its side effects for normal cells. In vitro cellular uptake and subcellular localization assays further proved that these smart drug nanovehicles, entering cancer cells mainly via endocytosis, could cause excellent drug accumulation in cancer cells. The present study provides a successful example with which to rational design an effective bola-type stimuli-responsive supramolecular nanocarrier, which might have wide potential applications in the construction of various controlled drug-delivery systems.

ATP-responsive codelivery of doxorubicin and nucleic acids for the synergistic cancer therapy

Polymer vesicles have wide applications in drug delivery, antibacterial and water remediation, etc. Theranostic polymer vesicles that can simultaneously deliver diagnostic and therapeutic agents, have been developed for more accurate diagnosis and more efficient cancer chemotherapy. Magnetic resonance imaging (MRI) is one of the most powerful and non-invasive clinical imaging modalities with high spatial resolution. Traditional T1 MRI contrast agents such as diethylene triamine pentacetatic acid (DTPA) chelated gadolinium [Gd(III)] have poor sensitivity, leading to a risk of accumulated toxicity in vivo. To significantly improve the sensitivity of a T1 MRI contrast agent and to enhance the efficacy of cancer chemotherapy, herein for the first time we report a noncytotoxic asymmetrical cancer targeting polymer vesicle based on R-poly(l-glutamic acid)-block-poly(caprolactone) [R is folic acid (FA) or DTPA]. Such asymmetrical vesicles have a cancer-targeting outer corona and a Gd(III)-chelating and drug-loading-enhancing inner corona, exhibiting an extremely high T1 relaxivity (42.39 mM −1 s, 8-fold better than DTPA-Gd) and anticancer drug loading efficiency (52.6% for doxorubicin hydrochloride, DOX · HCl). Moreover, the DOX-loaded vesicles exhibited excellent antitumor activity (two-fold better than free DOX). This “chelatingjust-inside” strategy for synthesizing asymmetrical polymer vesicles provided promising potential theranostic applications in magnetic resonance imaging and cancer-targeted drug delivery.

Structure-directing star-shaped block copolymers: Supramolecular vesicles for the delivery of anticancer drugs

Amphiphilic polycarbonate/PEG copolymer with a star-like architecture was designed to facilitate a unique supramolecular transformation of micelles to vesicles in aqueous solution for the efficient delivery of anticancer drugs. The star-shaped amphipilic block copolymer was synthesized by initiating the ring-opening polymerization of trimethylene carbonate (TMC) from methyl cholate through a combination of metal-free organo-catalytic living ring-opening polymerization and post-polymerization chain-end derivatization strategies. Subsequently, the self-assembly of the star-like polymer in aqueous solution into nanosized vesicles for anti-cancer drug delivery was studied. DOX was physically encapsulated into vesicles by dialysis and drug loading level was significant (22.5% in weight) for DOX. Importantly, DOX-loaded nanoparticles self-assembled from the star-like copolymer exhibited greater kinetic stability and higher DOX loading capacity than micelles prepared from cholesterol-initiated diblock analogue. The advantageous disparity is believed to be due to the transformation of micelles (diblock copolymer) to vesicles (star-like block copolymer) that possess greater core space for drug loading as well as the ability of such supramolecular structures to encapsulate DOX. DOX-loaded vesicles effectively inhibited the proliferation of 4T1, MDA-MB-231 and BT-474 cells, with IC50 values of 10, 1.5 and 1.0mg/L, respectively. DOX-loaded vesicles injected into 4T1 tumor-bearing mice exhibited enhanced accumulation in tumor tissue due to the enhanced permeation and retention (EPR) effect. Importantly, DOX-loaded vesicles demonstrated greater tumor growth inhibition than free DOX without causing significant body weight loss or cardiotoxicity. The unique ability of the star-like copolymer emanating from the methyl cholate core provided the requisite modification in the block copolymer interfacial curvature to generate vesicles of high loading capacity for DOX with significant kinetic stability that have potential for use as an anti-cancer drug delivery carrier for cancer therapy.

An Asymmetrical Polymer Vesicle Strategy for Significantly Improving T1 MRI Sensitivity and Cancer-Targeted Drug Delivery

Traditional T1 magnetic resonance imaging (MRI) contrast agents such as diethylenetriaminepentacetatic acid (DTPA) chelated gadolinium [Gd(III)] have poor sensitivity, leading to a risk of accumulated toxicity in vivo. To significantly improve the sensitivity of a T1 MRI contrast agent and to enhance the efficacy of cancer chemotherapy, herein for the first time we report a noncytotoxic asymmetrical cancer targeting polymer vesicle based on R-poly(l-glutamic acid)-block-poly(ε-caprolactone) [R is folic acid (FA) or DTPA]. Such asymmetrical vesicles have a cancer-targeting outer corona and a Gd(III)-chelating and drug-loading-enhancing inner corona, exhibiting an extremely high T1 relaxivity (42.39 mM–1 s–1, 8-fold better than DTPA-Gd) and anticancer drug loading efficiency (52.6% for doxorubicin hydrochloride, DOX·HCl). Moreover, the DOX-loaded vesicles exhibited excellent antitumor activity (2-fold better than free DOX). This “chelating-just-inside” strategy for synthesizing asymmetrical polymer vesicles demonstrated promising potential theranostic applications in magnetic resonance imaging and cancer-targeted drug delivery.

Multistimuli-responsive supramolecular vesicles based on water-soluble pillar[6]arene and SAINT complexation for controllable drug release.

Supramolecular binary vesicles based on the host-guest complexation of water-soluble pillar[6]arene (WP6) and SAINT molecule have been successfully constructed, which showed pH-, Ca(2+)-, and thermal-responsiveness. These supramolecular vesicles can efficiently encapsulate model substrate calcein, which then can be efficiently released either by adjusting the solution pH to acidic condition due to the complete disruption of vesicular structure, or particularly, by adding a certain amount of Ca(2+) due to the Ca(2+)-induced vesicle fusion and accompanied by the structure disruption. More importantly, drug loading and releasing experiments demonstrate that an anticancer drug, DOX, can be successfully encapsulated by the supramolecular vesicles, and the resulting DOX-loaded vesicles exhibit efficient release of the encapsulated DOX with the pH adjustment or the introduction of Ca(2+). Cytotoxicity experiments suggest that the resulting DOX-loaded supramolecular vesicles exhibit comparable therapeutic effect for cancer cells as free DOX and the remarkably reduced damage for normal cells as well. The present multistimuli-responsive supramolecular vesicles have great potential applications in the field of controlled drug delivery. In addition, giant supramolecular vesicles (~3 μm) with large internal volume and good stability can be achieved by increasing the temperature of WP6 ⊃ SAINT vesicular solution, and they might have potential applications for bioimaging.

Bioactive vesicles from saccharide- and hexanoyl-modified poly(l-lysine) copolypeptides and evaluation of the cross-linked vesicles as carriers of doxorubicin for controlled drug release

We report the synthesis and self-assembly of an amphiphilic glycopolypeptide through the conjugation of both lactobionolactone, a model targeted ligand to HepG2 liver cells, and hexanoyl groups onto poly(l-lysine) (PLL). The self-assembled glycopolypeptide vesicles were stabilized via genipin-cross-link and evaluated as cell-targeted carriers. The experimental data revealed that the saccharide and hexanoyl substitution can regulate the amphiphilic nature and chain conformation of the glycopolypeptide, and subsequently the size of the assembled vesicles. Taking the advantages of the glycopolypeptide vesicles including stable structure, pH-responsiveness, and cell-targeting ability, the glycopolypeptide was employed for drug encapsulation, i.e. doxorubicin (Dox). A high Dox loading level (45wt.%) can be achieved with the aid of sonication as a pH gradient was applied between the outside and inside of the vesicles. The cross-linked, vesicles loaded with Dox exhibited noticeable pH-sensitive behavior with accelerated Dox release at acidic condition due to the protonation of amino groups and the release rate can be controlled by the genipin to amine feed ratio. The cytocompatibility of the polypeptide was improved upon grafting the saccharide group and cross-link. The Dox-loaded vesicles exhibited a comparable cytotoxicity with respect to free Dox against HepG2 liver cells. These results point to a potential of novel glycopolypeptide vesicles with cross-linkable membrane to be carriers for the delivery of bioactive agents.

Novel Polymeric Vesicles with pH‐Induced Deformation Character for Advanced Drug Delivery

pH-responsive amphiphilic graft macromolecules consisting of a polyphosphazene backbone, hydrophilic PEG branches and pH-sensitive DPA were successfully synthesized and characterized. The copolymer can self-assemble into vesicles in an aqueous solution with unique inner structure and homogeneously encapsulate both lipophilic and hydrophilic molecules. The pH-dependent structure change of vesicles was also observed by DLS and TEM. Dox-loaded vesicles exhibit a sharp pH-responsive drug release profile and dramatically enhance the cytotoxicity of Dox against Dox-resistant MCF-7/adr cells. These results suggest such vesicles based on pH-responsive polyphosphazene hold great potential for specific drug therapy.

Novel Vesicles Self‐Assembled From Amphiphilic Star‐Armed PEG/Polypeptide Hybrid Copolymers for Drug Delivery

A novel amphiphilic four-armed [poly(ε-benzyloxycarbonyl-L-lysine)]₂-block-poly(ethylene glycol)-block-[poly(ε-benzyloxycarbonyl-L-lysine)]₂ hybrid copolymer has been prepared. The cytotoxicity study shows that the copolymer has good biocompatibility with no obvious inhibition effect on cell growth. The amphiphilic copolymers could self-assemble to form vesicles in aqueous solution. DOX · HCl, as a hydrophilic drug, can be loaded into the vesicles, and then successfully internalized by human breast cancer MCF-7 cells. Importantly, the DOX-loaded vesicles show a greatly improved drug release behavior with a zero-order release at the initial stage, suggesting a great potential as the carrier of hydrophilic drugs for controlled drug delivery.

A simple method to achieve high doxorubicin loading in biodegradable polymersomes

Doxorubicin (Dox), an anthracycline anticancer drug, was successfully incorporated into block copolymer vesicles of poly(trimethylene carbonate)- b-poly( l-glutamic acid) (PTMC- b-PGA) by a solvent-displacement (nanoprecipitation) method. pH conditions were shown to have a strong influence on loading capacity and release profiles. Substantial drug loading (47% w/w) was achieved at pH 10.5. After pH neutralization, aqueous dispersions of drug-loaded vesicles were found stable for a prolonged period of time (at least 6 months) without vesicle disruption or drug precipitation. Dox-loaded vesicles exhibited in vitro pH and temperature-dependent drug release profiles: release kinetics fastened in acid conditions or by increasing temperature. These features strongly support the interest of developing PTMC- b-PGA polymersomes as carriers for the controlled delivery of Dox.

Biodegradable vesicular nanocarriers based on poly(ɛ-caprolactone)-block-poly(ethyl ethylene phosphate) for drug delivery

Abstract Biodegradable polymer vesicle for drug delivery is reported. Poly(ɛ-caprolactone)- block -poly(ethyl ethylene phosphate) with well-defined structure (PCL 150 - b -PEEP 30 ) has been prepared by ring-opening polymerization. It forms vesicles in aqueous solution using the thin-film hydration method and further exclusion of the as-formed vesicles results in vesicles at nano-size, demonstrated by confocal laser scanning microscope (CLSM) and transmission electron microscopy observations. Doxorubicin (DOX) has been loaded into the vesicles with a loading content of 4.38% using an acid gradient method. The release of DOX from the vesicles is accelerated in the presence of an enzyme phosphodiesterase I that is known to catalyze the degradation of polyphosphoester, achieving 83.8% release of total loaded DOX in 140 h. The DOX-loaded vesicles can be successfully internalized by A549 cells, and it results in enhanced inhibition to A549 cell proliferation, likely owning to the sustained intracellular release of DOX as observed by CLSM. With these properties, the vesicles based on the block copolymer of PCL and PEEP are attractive as drug carriers for pharmaceutical application.