Enhanced growth inhibition of hepatic multicellular tumor spheroids by lactosylated poly(ethylene glycol)-siRNA conjugate formulated in PEGylated polyplexes

PEGylated polyplexes (lac-PEGylated polyplexes) composed of poly(L-lysine) and lactosylated poly(ethylene glycol)-small interfering RNA conjugate, which inhibits the RecQL1 gene product, were revealed to show an appreciable growth inhibition of multicellular HuH-7 spheroids (human hepatocarcinoma cell lines) for up to 21 days (IC(50)=6 nM); this system used as an in vitro three-dimensional (3D) model mimicking the in vivo biology of tumors. The PEGylated polyplexes thus prepared had a size of approximately 110 nm with clustered lactose moieties on their periphery as targeting ligands for the asialoglycoprotein-receptor-expressing HuH-7 cells. In contrast, OligofectAMINE/siRNA (cationic lipoplex) was observed to have almost no growth-inhibitory effect against HuH-7 spheroids, even though the lipoplex showed a stronger growth-inhibitory effect than the lac-PEGylated polyplexes on conventional monolayer-cultured HuH-7 cells. The FITC-tagged conjugate in the lac-PEGylated polyplexes showed smooth penetration into the HuH-7 spheroids compared with that in the lipoplexes, as observed by confocal fluorescence-scanning microscopy. This indicates that the small size of approximately 100 nm and the reduced nonspecific interaction due to the nonionic and hydrophilic lactosylated PEG layer contributes to the smooth penetration of the PEGylated polyplexes into the spheroid interior, eventually facilitating their uptake into the cells composing the spheroids. Cellular apoptosis indicating programmed cell death was also observed in the HuH-7 spheroids treated with the PEGylated polyplexes, revealing that the observed growth inhibition was indeed induced by the RNAi of the RecQL1 siRNA. These data suggest that the smart PEGylated polyplexes can indeed penetrate into the multiple cell layers of 3D tumor masses in vivo, exerting therapeutic effects through the RNAi.     

Fabrication of reduction-degradable micelle based on disulfide-linked graft copolymer-camptothecin conjugate for enhancing solubility and stability of camptothecin

This research is aimed to develop a reduction-degradable micelle delivery system based on polymer-camptothecin (CPT) conjugate in order to enhance the solubility and stability of CPT in aqueous media. Firstly, disulfide-linked poly(amido amine) (SS-PAA) containing alkyne groups was synthesized by Michael addition polymerization between propargyl amine and N,N′-bis(acryloyl) cystamine (BAC). And then, azide-functionalized CPT derivatives were conjugated with SS-PAA by click cycloaddition. Further grafting of residual alkyne groups in SS-PAA with azide-terminated poly(ethylene glycol) methyl ether (mPEG) gave mPEG-g-SS-PAA-CPT conjugate. At last, micelles with size of ca. 88 nm were fabricated from mPEG-g-SS-PAA-CPT conjugate, suggesting their passive targeting potential to tumor tissue. It was worthy of note that the drug-loaded system of mPEG-g-SS-PAA-CPT micelles improved the solubility and stability of CPT in aqueous media. Owing to the reduction degradability of disulfide linker in main chain of mPEG-g-SS-PAA-CPT, the CPT sustainably release from micelles together with the gradual cleavage of polymer in the presence of dithiothreitol (DTT) at the concentration of simulating the intracellular condition while almost no change occurred at the level of DTT corresponding to extracellular condition. Furthermore, the cell viability results showed the essential decrease of cytotoxicity to L929 cell line. These results present a strategy in designing anti-tumor CPT-polymer conjugates for highly selective delivery to tumor cells.     

Thermosensitive biotinylated hydroxypropyl cellulose-based polymer micelles as a nano-carrier for cancer-targeted drug delivery

In this article, we report the synthesis of a novel amphiphilic hydroxypropyl cellulose-based polymer (HPC-PEG-Chol) that contained poly (ethylene glycol) and cholesterol-containing moieties with specific degrees of substitution. The resulting polymer was subsequently converted to a biotin conjugate (HPC-PEG-Chol-biotin), to develop a new potential cancer-targeted drug delivery system. The biotin conjugate was used to prepare micelles via the dialysis method. The polymeric micelles in aqueous solution presented a lower critical solution temperature (LCST) of 39.8 ^oC. The critical micelle concentration (CMC) values of the polymeric micelles at 25 and 45 °C were evaluated to be about 0.32 and 0. 25 g/L, respectively. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses of the micelles revealed the spherical shapes of the micelles, with 84 nm mean diameters that increased with the increase of the temperature above LCST. The hydrophobic anticancer drug paclitaxel (PTX) was loaded in the micelles and the in vitro release behaviors of PTX were investigated at different temperatures. The release profile of PTX from the polymeric micelles revealed a thermosensitivity, since its release rate was higher at 41 °C than at 37 °C. Fluorescent microscopy analyses confirm that the PTX-loaded HPC-PEG-Chol-biotin is superior in cellular uptake, with very strong adsorption to both HeLa and MDA-MB-231 cancer cell lines. MTT assay in normal cells indicated that HPC-PEG-Chol-biotin micelles have great potential to be safely used in tumor-targeting chemotherapy.     

Synthesis and physicochemical characterization of amphiphilic block copolymers bearing acid-sensitive orthoester linkage as the drug carrier

Amphiphilic block copolymers bearing an acid-sensitive orthoester linkage, composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(γ-benzyl L-glutamate) (PBLG), were prepared as the carrier capable of selectively releasing the hydrophobic drug at the mildly acidic condition. Diblock copolymers with various lengths of PBLG were synthesized via ring opening polymerization of benzyl glutamate NCA in the presence of the acid-labile PEG as a macroinitiator. Owing to their amphiphilicities, the copolymers formed spherical micelles in aqueous conditions, and their particle sizes (22-106 nm in diameter) were dependent on the block length of PBLG. These nanoparticles were stable in the physiological buffer (pH 7.4), whereas they were readily decomposed under the acidic condition. In particular, the block copolymer with a smaller hydrophobic portion was rapidly disassembled under the acidic condition. Doxorubicin (DOX), chosen as the model anti-cancer drug, was effectively encapsulated into the hydrophobic core of the micelles using the solvent casting method. The loading efficiency depended on the hydrophobic block length of the copolymer; i.e., the longer hydrophobic block allowed for loading of larger amounts of the drug. In vitro release studies demonstrated that DOX was slowly released from the pH-sensitive micelles in the physiological buffer (pH 7.4), whereas the release rate of DOX significantly increased under the acidic condition (pH 5.0). From the in vitro cytotoxicity test, it was found that DOX-loaded pH-sensitive micelles showed higher toxicity to SCC7 cancer cells than DOX-loaded micelles without the orthoester linker. These results suggest that the amphiphilic block copolymer bearing the orthoester linkage is useful for pH-triggered delivery of the hydrophobic drug.     

Self-Assembled Polymeric Micellar Nanoparticles as Nanocarriers for Poorly Soluble Anticancer Drug Ethaselen

A series of monomethoxy poly(ethylene glycol)-poly(lactide) (mPEG-PLA) diblock copolymers were synthesized, and mPEG-PLA micelle was fabricated and used as a nanocarrier for solubilization and delivery of a promising anticancer drug ethaselen. Ethaselen was efficiently encapsulated into the micelles by the dialysis method, and the solubility of ethaselen in water was remarkably increased up to 82 μg/mL before freeze-drying. The mean diameter of ethaselen-loaded micelles ranged from 51 to 98 nm with a narrow size distribution and depended on the length of PLA block. In vitro hemolysis study indicated that mPEG-PLA copolymers and ethaselen-loaded polymeric micelles had no hemolytic effect on the erythrocyte. The enhanced antitumor efficacy and reduced toxic effect of ethaselen-loaded polymeric micelle when compared with ethaselen-HP-β-CD inclusion were observed at the same dose in H₂₂ human liver cancer cell bearing mouse models. These suggested that mPEG-PLA polymeric micelle nanoparticles had great potential as nanocarriers for effective solubilization of poorly soluble ethaselen and further reducing side effects and toxicities of the drug.     

Effect of vortex-induced physical stress on fluorescent properties of dye-containing poly(ethylene glycol)-block-poly(lactic acid) micelles

The effect of vortex-induced mechanical stresses on the fluorescent properties of dye-containing poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) block copolymer micelles has been investigated. PEG-b-PLA block copolymer micelles containing fluorescent dyes, 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO) and/or 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI), are prepared by a simple one-step procedure that involves the self-assembly of block copolymers and spontaneous incorporation of hydrophobic dyes into the core of the micelles. Upon vortexing, the micelle dispersion samples showed a decrease in fluorescence intensity in a rotational speed- and time-dependent manner. The results demonstrated that the vortexing can alter the fluorescent properties of the dye-containing PEG-b-PLA block copolymer micelle dispersion samples, suggesting the potential utility of block copolymer micelles as a mechanical stress-responsive nanomaterial.     

Structure investigation of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsulfate complexes in concentrated poly((2-dimethylamino)ethyl methacrylate) solutions using small angle neutron scattering

The structure of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsulfate complexes in water was investigated as a function of poly((2-dimethylamino)ethyl methacrylate) concentration at a fixed sodium dodecylsulfate concentration using small angle neutron scattering. When either hydrogenated or deuterated sodium dodecylsulfate was added to poly((2-dimethylamino)ethyl methacrylate) solutions in D₂O, a peak was observed in the small angle neutron scattering which was characteristic of charged micelles. This peak shifted to higher q in both cases as poly((2-dimethylamino)ethyl methacrylate) concentration increased, indicating that the size and shape of micelles changed due to favorable interactions between poly((2-dimethylamino)ethyl methacrylate) and sodium dodecylsulfate. The small angle neutron scattering intensity of the micelles in the polymer/surfactant solutions was measured at the condition where poly((2-dimethylamino)ethyl methacrylate) was contrast-matched. It was possible to obtain information about the structure of the micelles using the Hayter–Penfold model. Based on the results from the fit of the SANS data, it was found that partial shielding provided by poly((2-dimethylamino)ethyl methacrylate) monomers being incorporated into the micelle shell significantly influenced both the form factor and the structure factor of micelles in the polymer/surfactant solutions. This led to a decrease in the micelle size and an increase in the number of micelles. It was found that any increased repulsive potential resulting from a smaller distance between the charged micelles was relieved by a decrease in the surface charge.     

TPE‐conjugated biomimetic and biodegradable polymeric micelle for AIE active cell imaging and cancer therapy

Smart nanocarrier for simultaneous drug delivery and cellular imaging is ideal for both cancer therapy and diagnosis. In this work, polymeric micelles based on the tetraphenylethene (TPE) conjugated poly(N6‐carbobenzyloxy‐l ‐lysine)‐block‐poly(2‐methacryloyloxyethyl phosphorylcholine) (TPE‐PLys‐b‐PMPC) copolymer are successfully prepared. Such biomimetic and biodegradable TPE‐PLys‐b‐PMPC micelles exhibit remarkable aggregation‐induced emission (AIE) feature and great biocompatibility, showing great potential for bioimaging application. In addition, anticancer drug doxorubicin (DOX) can be incorporated into the core of micelles and the intracellular release of DOX can be furthermore traced through the fluorescent imaging of these AIE micelles. As expected, this DOX‐loading polymeric micelle shows significant growth inhibition against HeLa cells and 4T1 cells and such TPE‐PLys‐b‐PMPC micelles would be a promising drug carrier for potential cancer therapy and bioimaging. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45651.     

Amino‐terminated polylactide micelles with an external poly(ethylene oxide) corona as carriers of drug‐loaded anionic liposomes

Micelles were prepared from a mixture of NH₂‐terminated poly(l ‐lactide) and poly(d ,l ‐lactide)‐block‐poly(ethylene oxide) (molar ratio of 3:7). The micelles were complexed with bilayer lipid vesicles (liposomes) composed of anionic palmitoyloleoylphosphatidylserine and zwitterionic dioleoylphosphatidylcholine in a molar ratio of 3:7. The micelles and micelle–liposome complexes were characterized using dynamic light scattering, laser electrophoresis, fluorimetry, transmission electron microscopy, enzymatic hydrolysis and cell viability with the following main findings. (i) Average diameter of micelle cores was found to be 70 ± 10 nm. (ii) Each micelle carried ca 20 000 amino groups. (iii) In a pH 7 solution the impact of the protonated NH₂ groups in the total surface of micelles was negligible owing to their screening by bulky poly(ethylene oxide) blocks. (iv) The micelles were stable in slightly acidic and neutral aqueous solutions, but aggregated in slightly alkaline solutions. (v) The micelles showed no cytotoxicity up to 0.04 mg mL^?1 concentration (the maximum concentration in the experiment). (vi) Each micelle adsorbed ca 30 anionic liposomes loaded with the antitumor antibiotic doxorubicin; the liposomes retained their integrity upon binding with micelles. (vii) The initial micelles and the micelle–liposome complexes showed two‐week stability to enzymatic hydrolysis. © 2018 Society of Chemical Industry     

Thermal modulation of intracellular drug distribution using thermoresponsive polymeric micelles

Intracellular distribution of free doxorubicin (DOX) or DOX-loaded in polymeric micelles with thermoresponsive outer shells of poly(N-isopropylacrylamide) or its copolymers in cultured human breast cancer cells (MCF-7) were investigated by fluorescence and confocal laser scanning microscopy. Free DOX accumulated rapidly and selectively in cell nuclei, independent of temperature changes. In contrast to free drugs, the intracellular distribution of DOX-loaded in the thermoresponsive polymeric micelles was significantly affected by temperature changes across lower critical solution temperature (LCST) of the micelles. Above the micelle LCST, DOX delivered by the micelles was localized uniformly inside of MCF-7 cells. By contrast, the amount of DOX delivered to MCF-7 cells drastically decreased below the micelle LCST due to minimal interaction of the micelles with cell membrane surfaces. These results clearly showed that the mechanism of the intracellular drug localization was different between free drugs and DOX-loaded in the micelles. The thermoresponsive micelles aggressively interacted with the cells and carried DOX into the cells via triggered phase transition of the outer shells. In addition, much lower accumulation of free DOX was observed in the resistant cells compared to its parent sensitive MCF-7 due to the resistant mechanism. Of interest, DOX accumulation in the resistant cells was almost in the same level as with MCF-7 (sensitive) cells for the micelle system above the LCST.     

A biodegradable triblock copolymer poly(ethylene glycol)-b-poly(l-lactide)-b-poly(l-lysine): Synthesis,self-assembly,and RGD peptide modification

A novel biodegradable triblock copolymer poly(ethylene glycol)-b-poly(l-lactide)-b-poly(l-lysine) (PEG–PLA–PLL) was synthesized by acidolysis of poly(ethylene glycol)-b-poly(l-lactide)-b-poly(ɛ-benzyloxycarbonyl-l-lysine) (PEG–PLA–PZLL) obtained by the ring-opening polymerization (ROP) of ɛ-benzyloxycarbonyl-l-lysine N-carboxyanhydride (ZLys NCA) with amino-terminated PEG–PLA–NH₂ as a macroinitiator, and the pendant amino groups of the lysine residues were modified with a peptide known to modulate cellular functions, Gly-Arg-Gly-Asp-Ser-Tyr (GRGDSY, abbreviated as RGD) in the presence of 1,1′-carbonyldiimidazole (CDI). The structures of PEG–PLA–PLL/RGD and its precursors were confirmed by ¹H NMR, FT-IR, amino acid analysis and XPS analysis. The cell adhesion and cell spread on the PEG–PLA–PLL/RGD film were enhanced compared to those on pure PLA film. Therefore, the novel RGD-grafted triblock copolymer is promising for cell or tissue engineering applications. Both copolymers PEG–PLA–PZLL and PEG–PLA–PLL showed an amphiphilic nature and could self-assemble into micelles of homogeneous spherical morphology. The micelles were determined by fluorescence technique, dynamic light scattering (DLS), and field emission scanning electron microscopy (ESEM) and could be expected to find application in drug and gene delivery systems.     

Liquid crystalline polyethers based on conformational isomerism

Summary Nonradiative singlet energy transfer has been used to monitor the formation of micelles by diblock copolymers of poly(styrene) and poly(oxyethylene). The acceptor is placed at the junction between the two blocks in sample A1. The donor is placed either at the junction point between the blocks (D1) or free end of the block of poly(styrene) (D2). The experiment finds similar efficiencies of nonradiative singlet energy transfer in micelles formed by D1 and A1, and micelles formed by D2 and A1. This result implies that the free ends of the insoluble blocks do not seek out the center of mass of the micelle, but instead have a distribution throughout the micelle that is similar to the distribution of the junction points. Therefore the result confirms a crucial prediction from a recent simulation of the internal structure of the micelle formed by diblock copolymers in a selective solvent.     

Self-Assembled Glucose and Thermo Dual-Responsive Micelles of an Amphiphilic Graft Copolymer

Amphiphilic copolymers P(PBA)-g-P(PEG) containing poly(phenylboronic acid) (PPBA) and poly(ethylene glycol) (PEG) side chains were synthesized by copolymerization of 4-vinylphenylboronic acid (PBA) and poly(ethylene glycol) methyl ether methacrylate. The surface tension results showed that the critical micelle concentration (CMC) of P(PBA)-g-P(PEG) was 0.09 g/L. TEM revealed that these copolymers self-assembled into regular sphere micelles above CMC. The photon correlation spectroscopy suggested that they had unique performance of thermo-induced self-assembly. Above critical micelle temperature, they self-assembled into monodisperse micelles with thermosensitivity. Hydrodynamic diameters of these micelles increased dramatically in the presence of glucose. The glucose-regulated drug release behavior was observed through UV-vis spectroscopy.     

Synthesis of pH-Responsive Multilayer Micelles for Sustained Release of Folic Acid

Two novel triblock copolymers poly(hydroxypropyl acrylate)-b-poly (methyl methacrylate)-b-poly(N,N-dimethylaminoethyl methacrylate) and poly(hydroxypropyl acrylate)-b-poly(methyl methacrylate)-b-poly(acrylic acid) were successfully synthesized. In acetone media, using the electrostatic interactions between N,N-dimethylaminoethyl methacrylate and acrylic acid units, they could form spherically shaped multilayer micelles with pH-responsive, and have a mean diameter around 110 nm. The critical micelle concentration of it was determined to be 2.42 mg/L. In vitro release experiments, the folic acid-loaded micelles exhibited sustained release behavior and the drug release rate was affected by the pH value of release media. These results indicate that the multilayer micelles may serve as a novel intelligent drug delivery system.     

Non-invasive tumor detection in small animals using novel functional Pluronic nanomicelles conjugated with anti-mesothelin antibody

In this study QDs were encapsulated in carboxylated PluronicF127 (F127COOH) triblock polymeric micelles and conjugated with anti-mesothelin antibody for the purpose of alleviating potential toxicity, enhancing the stability and improving targeting efficiency of CdTe/ZnS quantum dots (QDs) in tumors. The amphiphilic triblock polymer of F127COOH contains hydrophilic carboxylated poly(ethylene oxide) (PEO) and hydrophobic poly(propylene oxide) (PPO) units. After encapsulating QDs into carboxylated F127 (F127COOH-QD) micelles, the particles were conjugated with anti-mesothelin antibodies to allow targeting of cancerous areas. The size of the monodispersed spherical QD-containing micelles was determined to be ～120 nm by dynamic light scattering (DLS). The critical micelle concentration (CMC) was estimated to be 4.7 × 10(-7) M. In an in vitro study, the anti-methoselin antibody conjugated F127COOH (Me-F127COOH-QD) nanomicelles showed negligible cytotoxicity to pancreatic cancer cells (Panc-1). Confocal microscopy demonstrated that the Me-F127COOH-QD nanomicelles were taken up more efficiently by Panc-1 cells, due to antibody mediated targeting. An in vivo imaging study showed that Me-F127COOH-QD nanomicelles accumulated at the pancreatic tumor site 15 min after intravenous injection. In addition, the low in vivo toxicity of the nanomicellar formulation was evaluated by pathological assays. These results suggest that anti-mesothein antibody conjugated carboxylated F127 nanomicelles may serve as a promising nanoscale platform for early human pancreatic cancer detection and targeted drug delivery.     

Oligonucleotide synthesis onto poly(N‐acryloylmorpholine‐co‐N‐acryloxysuccinimide): Assessment of the resulting conjugates in a DNA sandwich hybridization test

A water‐soluble statistical poly(N‐acryloylmorpholine‐co‐N‐acryloxysuccinimide) [poly(NAM/NAS)] copolymer was studied for polymer–oligonucleotide (ODN) conjugate elaboration and for further use in diagnostic applications. Three different copolymers were first prepared by free‐radical solution polymerization with different N‐acryloylmorpholine (NAM) and N‐acryloxysuccinimide (NAS) molar ratios (80/20, 70/30, and 60/40). Their number‐average molecular weights ranged from 98,000 to 120,000 g/mol, as determined by aqueous size exclusion chromatography with an online light‐scattering detector. Then, polymer–ODN conjugates were obtained via a strategy consisting of the direct synthesis of ODNs onto polymer chains previously grafted onto a controlled pore glass support. Before the grafting of the polymer onto the solid support, a preliminary step was performed to bind a nucleotide starter along the polymer chain (via the reactive NAS units) to initiate automated DNA synthesis. To multiply the number of ODNs growing from starters, a branched phosphoramidite synthon [bearing two O‐dimethoxytrityl groups] was introduced at the first step of ODN elongation as a short sequence of four branched synthons alternated with three thymidine residues. Conjugates were assessed in a DNA sandwich hybridization test developed for hepatitis B virus detection. Sensitivity limits were evaluated and compared to those obtained with an other polymer, poly(maleic anhydride‐alt‐methyl vinyl ether) [poly(MA/MVE)]. A sensitivity limit of 2.6 × 10⁷ DNA copies/mL was reached with the poly(MA/MVE)–ODN conjugate at the capture phase and with the poly(NAM/NAS)–branched ODN conjugate at the detection phase of the test. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3784–3795, 2004     

Micelles formed by self‐assembly of hyperbranched poly[(amine‐ester)‐co‐(D,L‐lactide)] (HPAE‐co‐PLA) copolymers for protein drug delivery

BACKGROUND: The aim of the work presented was to synthesize a series of amphiphilic hyperbranched poly[(amine‐ester)‐co‐(D ,L ‐lactide)] (HPAE‐co‐PLA) copolymers and study the formation of copolymeric micelles. These copolymeric micelle systems are expected to be potential candidates for applications in protein drug delivery. RESULTS: The chemical structures of the copolymers were confirmed by Fourier transform infrared spectroscopy, ¹³C NMR and thermogravimetric analysis. Fluorescence spectroscopy and dynamic light scattering confirmed the formation of copolymeric micelles of the HPAE‐co‐PLA copolymers. The maintenance of stability of bovine serum albumin (BSA) during release from micelles in vitro was also measured using circular dichroism and fluorescence spectrometry. CONCLUSION: Novel hyperbranched HPAE‐co‐PLA copolymers have been synthesized. Conjugation of PLA to HPAE was proved to be an available method for the preparation of micelles for protein delivery. The BSA‐loaded micelles showed enhanced encapsulation efficiency and the structural stability of BSA was retained during the release process. The hyperbranched polymeric micelles could be useful as drug carriers for protein drug delivery systems. Copyright © 2008 Society of Chemical Industry     

Enhanced loading of doxorubicin into polymeric micelles by a combination of ionic bonding and hydrophobic effect,and the pH-sensitive and ligand-mediated delivery of loaded drug

Folate-conjugated micelles were fabricated from amphiphilic diblock copolymers with poly(ethylene glycol) as the hydrophilic block and a random copolymer of n-butyl methacrylate and methacrylic acid as the hydrophobic block. Doxorubicin (DOX), a model drug that contains an amine group and hydrophobic moiety, was loaded with a high loading capacity into micelles by a combination of ionic bonding and hydrophobic effect. The combined interactions imparted a pH-sensitive delivery property to the system. The release rate of loaded DOX was slow at pH 7.4 (i.e., mimicking the plasma environment) but increased significantly at acidic pH (i.e., mimicking endosome/lysosome conditions). Acid-triggered drug release resulted from the carboxylate protonation of poly(methacrylic acid), which dissociated the ionic bonding between the micelles and DOX. Cellular uptake by folate receptor-overexpressing HeLa cells of the DOX-loaded folate-conjugated micelles was higher than that of micelles without folate conjugation. Thus, the DOX-loaded folate-conjugated micelles displayed higher cytotoxicity to HeLa cells.     

Polymerized micelles. Fixation of micelle structure by the core cross-linking

Summary Polymerized micelles of poly(11-acryloylaminoundecanoic acid) were obtained via radical polymerization in micellar state. The structure of micelles was fixed by cross-linking of the micelle core using solubilized diacrylate co-monomer. Hydrodynamic behavior of both cross-linked and non cross-linked polymerized micelles was studied by means of viscometry.     

Diclofenac/biodegradable polymer micelles for ocular applications

In this paper, methoxypoly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelle formulations as promising nano-carriers for poorly water soluble drugs were investigated for the delivery of diclofenac to the eye. Diclofenac loaded MPEG-PCL micelles were prepared by a simple solvent-diffusion method and characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), differential scanning calorimetery (DSC), etc. With the analysis of XRD and DSC, the diclofenac was present as an amorphous state in the formulation. The in vitro release profile indicated a sustained release manner of diclofenac from the micelles. Meanwhile, in vivo studies on eye irritation were performed with blank MPEG-PCL micelles (200 mg ml(-1)). The results showed that the developed MPEG-PCL micelles were non-irritants to the eyes of rabbits. In vitro penetration studies across the rabbit cornea demonstrated that the micelle formulations exhibited a 17-fold increase in penetration compared with that of diclofenac phosphate buffered saline (PBS) solution. The in vivo pharmacokinetics profile of the micelle parent drug in the aqueous humor of the rabbit was evaluated and the data showed that the diclofenac loaded MPEG-PCL micelles exhibited a 2-fold increase in AUC(0-24 h) than that of the diclofenac PBS solution eye drops. These results suggest a great potential of our micelle formulations as a novel ocular drug delivery system to improve the bioavailability of the drugs.