Yanxia Zhou

Novel Mixed Polymeric Micelles for Enhancing Delivery of Anticancer Drug and Overcoming Multidrug Resistance in Tumor Cell Lines Simultaneously

ABSTRACTPurposeTo evaluate novel mixed polymeric micelles based on monomethoxy poly(ethylene glycol)-poly(D,L-lactic acid) (mPEG-PLA) and Pluronic L61 for delivery of paclitaxel (PTX) to circumvent unfavorable effects resulting from Cremophore EL in Cremophore EL-based PTX formulation and overcoming multidrug resistance (MDR) in tumor cells at the same time.MethodsPTX-loaded plain micelles and mixed micelles were prepared and characterized by determining PTX release in vitro, MDR reversal effect in human breast cancer MDR MCF-7/ADR cell sublines and pharmacokinetics in vivo.ResultsBoth PTX-loaded plain micelles and mixed micelles had similar in vitro release profile. Mixed micellar PTX significantly reduced IC50 of PTX in MCF-7/ADR cells compared to free PTX and plain micellar PTX, and mixed micelles substantially enhanced cellular accumulation of R 123 in MCF-7/ADR cells compared to free R123 and plain micelles. PTX-loaded mixed micelles with lower content of L61 exhibited comparable cytotoxicity to that observed with Cremophore EL-based PTX formulation in inhibiting the growth of MCF-7/ADR cells. Moreover, plain micelles and mixed micelles retained the pharmacokinetic characteristics of PTX in rats compared with Cremophore EL-based PTX formulation.ConclusionThis study suggested that the mixed micelles could enhance delivery of PTX and cell-killing effect for MDR MCF-7/ADR cells.

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 H22human 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.

Preparation and evaluation of novel mixed micelles as nanocarriers for intravenous delivery of propofol

Novel mixed polymeric micelles formed from biocompatible polymers, poly(ethylene glycol)-poly(lactide) (mPEG-PLA) and polyoxyethylene-660-12-hydroxy stearate (Solutol HS15), were fabricated and used as a nanocarrier for solubilizing poorly soluble anesthetic drug propofol. The solubilization of propofol by the mixed micelles was more efficient than those made of mPEG-PLA alone. Micelles with the optimized composition of mPEG-PLA/Solutol HS15/propofol = 10/1/5 by weight had particle size of about 101 nm with narrow distribution (polydispersity index of about 0.12). Stability analysis of the mixed micelles in bovine serum albumin (BSA) solution indicated that the diblock copolymer mPEG efficiently protected the BSA adsorption on the mixed micelles because the hydrophobic groups of the copolymer were efficiently screened by mPEG, and propofol-loaded mixed micelles were stable upon storage for at least 6 months. The content of free propofol in the aqueous phase for mixed micelles was lower by 74% than that for the commercial lipid emulsion. No significant differences in times to unconsciousness and recovery of righting reflex were observed between mixed micelles and commercial lipid formulation. The pharmacological effect may serve as pharmaceutical nanocarriers with improved solubilization capacity for poorly soluble drugs.

Development of Silymarin Self-Microemulsifying Drug Delivery System with Enhanced Oral Bioavailability

The objective of this work was to develop a self-microemulsifying drug delivery system (SMEDDS) for improving oral absorption of poorly water-soluble drug, silymarin. The pseudo-ternary phase diagrams were constructed using ethyl linoleate, Cremophor EL, ethyl alcohol, and normal saline to identify the efficient self-microemulsification region. The particle size and its distribution of the resultant microemulsions were determined using dynamic light scattering. The optimal formulation with the best self-microemulsifying and solubilization ability consisted of 10% (w/w) of ethyl linoleate, 30% of Cremophor EL, and 60% of ethyl alcohol. The release of silymarin from SMEDDS was significantly faster than that from the commercial silymarin preparation hard capsule (Legalon®). The bioavailability results indicated that the oral absorption of silymarin SMEDDS was enhanced about 2.2-fold compared with the hard capsule in fasted dogs. It could be concluded that SMEDDS would be a promising drug delivery system for poorly water-soluble drugs by the oral route.

pH-responsive polymeric micelles based on poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) for tumor-targeting and controlled delivery of doxorubicin and P-glycoprotein inhibitor

The combination of a chemotherapeutic drug with a P-glycoprotein (P-gp) inhibitor has emerged as a promising strategy for treating multidrug resistance (MDR) cancer. To ensure that two drugs can be co-delivered to the tumor region and quickly released in tumor cells, tumor-targeted and pH-sensitive polymeric micelles were designed and prepared by combining cationic ring-opening polymerization of 2-ethyl-2-oxazoline (EOz) with anionic ring-opening polymerization of D,L-lactide (LA), and then encapsulating doxorubicin (DOX) and D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS1000) into the micelles self-assembled by poly(2-ethyl-2-oxazoline)-poly(D,L-lactide) (PEOz-PLA) and DSPE-PEG-folate. PEOz-PLA exhibited a low critical micelle concentration and negligible cytotoxicity. The micelles enabled the rapid release of DOX when pH decreased from 7.4 to 5.0. The targeting ability of the micelles was demonstrated by in vitro flow cytometry in KBv cells and in vivo real time near-infrared fluorescence imaging in KBv tumor-bearing nude mice. The efficiency of MDR reversion for the micelles was testified by enhancement of intracellular DOX accumulation and cytotoxicity. The efficient drug delivery by the micelles was attributed to synergistic effects of folate-mediated targeting, pH-triggered drug release and TPGS1000-aroused P-gp inhibition. Therefore, the designed multifunctional polymeric micelles may have significant promise for therapeutic application of MDR cancer.

The use of polyion complex micelles to enhance the oral delivery of salmon calcitonin and transport mechanism across the intestinal epithelial barrier

The objective of the present study was to demonstrate the effect of polyanionic copolymer mPEG-grafted-alginic acid (mPEG-g-AA)-based polyion complex (PIC) micelles on enhancing the oral absorption of salmon calcitonin (sCT) in vivo and in vitro and identify the transepithelial transport mechanism of PIC micelles across the intestinal barrier. mPEG-g-AA was first successfully synthesized and characterized in cytotoxicity. The PIC micelles were approximately of 72 nm in diameter with a narrow distribution. The extremely significant enhancement of hypocalcemia efficacy of sCT-loaded PIC micelles in rats was evidenced by intraduodenal administration in comparison with sCT solution. The presence of mPEG-grafted-chitosan in PIC micelles had no favorable effect on this action in the referred content. In the Caco-2 transport studies, PIC micelles could significantly increase the permeability of sCT across Caco-2 monolayers without significantly affecting transepithelial electrical resistance values during the transport study. No evident alterations in the F-actin cytoskeleton were detected by confocal microscope observation following treatment of the cell monolayers with PIC micelles, which further certified the incapacity of PIC micelles to open the intercellular tight junctions. In addition, TEM observations showed that the intact PIC micelles were transported across the everted gut sac. These suggested that the transport of PIC micelles across Caco-2 cell monolayers involve a predominant transcytosis mechanism via endocytosis rather than paracellular pathway. Furthermore, PIC micelles were localized in both the cytoplasm and the nuclei observed by CLSM. Therefore, PIC micelles might be a potentially applicable tool for enhancing the oral absorption of cationic peptide and protein drugs.

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

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

Preparation and Evaluation of Poly(Ethylene Glycol)–Poly(Lactide) Micelles as Nanocarriers for Oral Delivery of Cyclosporine A

A series of monomethoxy poly(ethylene glycol)–poly(lactide) (mPEG–PLA) diblock copolymers were designed according to polymer–drug compatibility and synthesized, and mPEG–PLA micelle was fabricated and used as a nanocarrier for solubilization and oral delivery of Cyclosporine A (CyA). CyA was efficiently encapsulated into the micelles with nanoscaled diameter ranged from 60 to 96 nm with a narrow size distribution. The favorable stabilities of CyA-loaded polymeric micelles were observed in simulated gastric and intestinal fluids. The in vitro drug release investigation demonstrated that drug release was retarded by polymeric micelles. The enhanced intestinal absorption of CyA-loaded polymeric micelles, which was comparable to the commercial formulation of CyA (Sandimmun Neoral®), was found. These suggested that polymeric micelles might be an effective nanocarrier for solubilization of poorly soluble CyA and further improving oral absorption of the drug.

Cyclosporin A-loaded poly(ethylene glycol)-b-poly(d,l-lactic acid) micelles: preparation, in vitro and in vivo characterization and transport mechanism across the intestinal barrier.

To improve the oral bioavailability of poorly water-soluble cyclosporin A (CyA), polymeric micelles based on monomethoxy poly(ethylene glycol)-b-poly(d,l-lactic acid) (mPEG-PLA) were prepared. In vitro release test showed that the cumulative release percentage, about 85%, of CyA from polymeric micelles within 24 h was comparable to that from Sandimmun Neoral, the currently available oral formulation of CyA. A relative oral bioavailability of 137% in rats compared with Sandimmun Neoral was demonstrated for CyA-loaded polymeric micelles. The other aim of the current work was to study the transport mechanism of mPEG-PLA micelles across the intestinal barrier. It was found that polymeric micelles could significantly increase the permeability of CyA across Caco-2 monolayers without significantly affecting transepithelial electrical resistance values, and the apparent permeation coefficient (P(app)) of CyA was significantly higher in the AP-BL direction compared to that in the BL-AP direction, suggesting that polymeric micelles might undergo an active AP to BL transport that probably involved endocytosis which was confirmed by confocal microscope observation. The permeation of CyA through Caco-2 monolayers showed that the P(app) was significantly increased when CyA was formulated with the copolymer below its critical association concentration (CAC) and no significant difference was found above its CAC, implying that mPEG-PLA monomers affected the intestinal P-gp efflux pumps. Therefore, the mPEG-PLA micelles seemed to be a good candidate for oral delivery of poorly soluble drugs.

Enhanced antitumor efficacy by cyclic RGDyK-conjugated and paclitaxel-loaded pH-responsive polymeric micelles

Cyclic RGDyK (cRGDyK)-conjugated pH-sensitive polymeric micelles were fabricated for targeted delivery of paclitaxel to prostate cancer cells based on pH-sensitive copolymer poly(2-ethyl-2-oxazoline)-poly(D,L-lactide) (PEOz-PLA) and cRGDyK-PEOz-PLA to enhance antitumor efficacy. The prepared micelles with an average diameter of about 28nm exhibited rapid release behavior at endo/lysosome pH, effectively enhanced the cytotoxicity of paclitaxel to PC-3 cells by increasing the cellular uptake, which was correlated with integrin αvβ3 expression in tumor cells. The active targeting activity of the micelles was further confirmed by in vivo real time near-infrared fluorescence imaging in PC-3 tumor-bearing nude mice. Moreover, the active targeting and pH-sensitivity endowed cRGDyK-conjugated micelles with a higher antitumor effect in PC-3 xenograft-bearing nude mice compared with unmodified micelles and Taxol with negligible systemic toxicity. Therefore, these results suggested that cRGDyK-conjugated pH-sensitive polymeric micelles may be a promising delivery system for efficient delivery of anticancer drugs to treat integrin αvβ3-rich prostate cancers.