Drug-loaded Mixed Micelles Research Articles

PH-Sensitive Mixed Micelles Assembled from PDEAEMA-PPEGMA and PCL-PPEGMA for Doxorubicin Delivery: Experimental and DPD Simulations Study.

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.

Pharmacokinetics and brain targeting of trans-resveratrol loaded mixed micelles in rats following intravenous administration

Trans-Resveratrol (T-RES) is a compound with wide therapeutic applications that shows low bioavailability and distribution across blood-brain barrier. The purpose of our study was to develop T-RES loaded mixed micelle (T-RES-MM) for its enhanced systemic availability and targeting to the brain. T-RES-MMs were formulated using Pluronic F-127 (PF-127) and d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) by using film hydration process. Formulations were characterized for size of particles, zeta potential, drug efficiency of entrapment, drug loading, and hemolytic study. Further in vivo pharmacokinetic and brain distribution study carried out in Sprague Dawley rats. The nano ranged size for drug-loaded mixed micelles was 21.55 ± 2.15 nm for optimized formulation with PF-127:TPGS (4:1). Formulation with maximum drug loading and entrapment efficiency of 8.4 ± 0.37% and 94.37 ± 1.01% respectively were further used for in vivo study. Percent hemolysis by micelles at all concentrations indicates the biocompatibility and safety for administration by i.v. route. The AUC0-t for T-RES-MM was 460.98 ± 158.99 h*ng/ml while for T-RES it was 276.27 ± 174.05 h*ng/ml. Drug targeting index suggests successful targeting of T-RES to the brain. Overall findings conclude in prepared T-RES-MM exhibit superiority of formulation as compared to T-RES solution.

Poloxamer 407/TPGS Mixed Micelles as Promising Carriers for Cyclosporine Ocular Delivery.

Cyclosporine is an immunosuppressant agent approved for the treatment of dry eye disease and used off-label for other ocular pathologies. Its formulation and ocular bioavailability present a real challenge due to the large molecular weight (1.2 kDa), high lipophilicity, and low water solubility. The aim of the work was to develop an aqueous micellar formulation for an efficient cyclosporine delivery to the ocular tissues, using a water-soluble derivative of vitamin E (TPGS: d-α-tocopheryl polyethylene glycol 1000 succinate) and poloxamer 407 (Pluronic ®F127) as excipients. The mixed micelles were characterized in terms of particle size, zeta potential, rheology, and stability upon dilution and freeze-drying. Additionally, the enzymatic-triggered release of vitamin E and vitamin E succinate from TPGS was investigated in vitro in the presence of esterase. Compared to the commercially available ophthalmic formulation, the poloxamer 407:TPGS 1:1 molar ratio micellar formulation significantly improved cyclosporine solubility, which increased proportionally to surfactant concentration reaching 0.4% (w/v) for 20 mM surfactant total concentration. Cyclosporine-loaded mixed micelles efficiently retained the drug once diluted in simulated lachrymal fluid and, in the presence of a 20 mM surfactant concentration, were stable upon freeze-drying. The drug-loaded mixed micelles were applied ex vivo on porcine cornea and compared to Ikervis®. Drug accumulation in the cornea resulted proportional to drug concentration (6.4 ± 1.9, 17.6 ± 5.4, and 26.9 ± 7.4 μgdrug/gcornea, after 3 h for 1, 2.5, and 4 mg/mL cyclosporine concentration respectively). The formulation containing cyclosporine 4 mg/mL (20 mM surfactant) was also evaluated on the sclera, with a view to targeting the posterior segment. The results demonstrated the capability of mixed micelles to diffuse into the sclera and sustain cyclosporine delivery (28 ± 7, 38 ± 10, 57 ± 9, 145 ± 27 μg/cm2 cyclosporine accumulated after 3, 6, 24, and 48 h respectively). Reservoir effect experiments demonstrated that the drug accumulated in the sclera can be slowly released into the underlying tissues. Finally, all the formulations developed in this work successfully passed the HET-CAM assay for the evaluation of ocular irritability.

Comparison of bile salt/phosphatidylcholine mixed micelles in solubilization to sterols and stability.

Androst-3β,5α,6β-triol (Triol) is a promising neuroprotective agent, but its poor solubility restricts its development into parenteral preparations. In this study, Triol is significantly solubilized by bile salt/phosphatidylcholine mixed micelles (BS/PC-MM). All BS/PC-MM systems are tested to remarkably improve the drug solubility with various stabilities after drug loading. Among them, the sodium glycocholate (SGC)/egg phosphatidylcholine (EPC) system with 2:1 ratio in weight and the total concentration of SGC and EPC of 100 mg/mL is proved to produce stable mixed micelles with high drug loading. It is found that the stability of drug-loaded mixed micelles is quite different, which might be related to the change in critical micelle concentration (CMC) after incorporating drugs. SGC/EPC and SGC/soya phosphatidylcholine (SPC) remain transparent under accelerated conditions and manifest a decreased CMC (dropping from 0.105 to 0.056 mg/mL and from 0.067 to 0.024 mg/mL, respectively). In contrast, swine bile acid-sodium salt (SBA-Na)/PC and sodium deoxycholate (SDC)/PC are accompanied by drug precipitation and reached the maximum CMC on the first and the third days, respectively. Interestingly, the variation of CMC under accelerated testing conditions highly matches the drug-precipitating event in the primary stability experiment. In brief, the bile salt/phosphatidylcholine system exists as a potential strategy of improving sterol drug solubility. CMC variation under accelerated testing conditions might be a simple and easy method to predict the stability of drug-loaded mixed micelles.

Pluronic-based functional polymeric mixed micelles for co-delivery of doxorubicin and paclitaxel to multidrug resistant tumor

Although doxorubicin (DOX) and paclitaxel (PTX) are widely used in clinic as chemotherapeutics, both drug substances are found to be glycoprotein P (P-gp) substrates which are liable to develop the multidrug resistance (MDR). Additionally, the use of single chemotherapeutic drug has known limitations such as high toxicity profile due to the relatively high doses and limited regimen of clinical application. To this end, Pluronic P105–DOX conjugate was successfully designed and developed which can be further used as a hydrophobic core to entrap another anti-cancer drug PTX with Pluronic F127 to form the dual drug-loaded mixed micelles (PF–DP) in our study, which would offer great advantages over conventional micelles, including easy fabrication, high loading capacity, and co-delivery of hydrophilic DOX and hydrophobic PTX to achieve synergistic effect of these two drug substances. Results showed that PF–DP possessed a good polydispersity and sustained release profile for both DOX and PTX in vitro. Studies on cellular uptake demonstrated both anti-cancer drugs in PF–DP can effectively accumulate in MDR cancer cells. Furthermore, in vitro cytotoxicity, cell apoptosis and cell cycle arrest studies indicated that PF–DP had better antitumor efficacy in MDR cancer cells compared to those of single-drug loaded micelles. It was also found that PF–DP can suppress the growth of tumor cells more efficiently than single drug formulations at the equivalent drug concentrations, suggesting synergistic effect could be achieved. More importantly, a much stronger antitumor efficacy in MCF-7/ADR tumor-bearing mice was observed in PF–DP group than that of combined administration of free DOX and PTX. Collectively, the dual drug-loaded Pluronic-based functional mixed micelles developed in this study might be a potential nano-drug delivery system for MDR cancer chemotherapy.

Controlled co-delivery nanocarriers based on mixed micelles formed from cyclodextrin-conjugated and cross-linked copolymers

The combination of multiple drugs within a single nanocarrier can provide significant advantages for disease therapy and it is desirable to introduce a second drug based on host–guest interaction in these co-delivery systems. In this study, a core-stabilized mixed micellar system consisting of β-cyclodextrin-conjugated poly(lactic acid)-b-poly(ethylene glycol) (β-CD-PLA-mPEG) and DL-Thioctic acid (TA) terminated PLA-mPEG (TA-PLA-mPEG) was developed for the co-delivery of DOX and fluorescein isothiocyanate labeled adamantane (FA). DOX can be loaded within the hydrophobic segment of PLA and FA may form stable complexation with β-CD in the core. The mixed micelles (MM) are based on well-accepted medical materials and can be easily cross-linked by adding 1,4-dithio-d,l-threitol (DTT), which can enhance the stability of the system. Drug-loaded MM system was characterized in terms of particle size, morphology, drug loading and in vitro release profile. Cytotoxicity test showed that blank MM alone showed negligible cytotoxicity whereas the drug-loaded MM remained relatively high cytotoxicity for HeLa cancer cells. Confocal laser scanning microscopy (CLSM) demonstrated that the MM could efficiently deliver and release DOX and FA in the same tumor cells to effectively improve drugs’ bioavailability. These results suggested that the core-stabilized MM are highly promising for intracellular co-delivery of multiple drugs.

PH and redox-responsive mixed micelles for enhanced intracellular drug release

In order to prepare pH and redox sensitive micelles, amphiphilic copolymers of poly (epsilon-caprolactone)-b-poly(2-(diethylamino) ethyl methacrylate) (PCL–PDEA) and disulfide-linked poly(ethyl glycol)-poly(epsilon-caprolactone) (mPEG–SS–PCL) were synthesized. The double-sensitive micelles were prepared simply by solvent-evaporating method with the mixed two copolymers. The pH sensitivity of the mixed micelles was confirmed by the change of micelle diameter/diameter distribution measured by dynamic lighting scattering (DLS) and the redox sensitivity of the mixed micelles was testified by the change of micellar morphous observed by scanning electron microscope (SEM). In vitro drug release showed that drug-loaded mixed micelles (mass ratio 5:5) could achieve above 90% of drug release under low pH and reducing condition within 10h. Moreover, the drug-loaded mixed micelles (mass ratio 5:5) showed the largest cellular toxicity compared with other drug-loaded micelles, while blank mixed micelles exhibited no toxicity. These results meant that the mixed micelles composed by the two amphiphilic copolymers can enhance intracellular drug release. It is concluded that the newly developed mixed micelles can serve as a potential drug delivery system for anticancer drugs.

Co-delivery of thioridazine and doxorubicin using polymeric micelles for targeting both cancer cells and cancer stem cells

In this study, thioridazine (THZ), which was reported to kill cancer stem cells, was used in a combination therapy with doxorubicin (DOX) to eradicate both cancer cells and DOX-resistant cancer stem cells to mitigate the reoccurrence of the disease. Both THZ and DOX were loaded into micelles with sizes below 100 nm, narrow size distribution and high drug content. The micelles were self-assembled from a mixture of acid-functionalized poly(carbonate) and poly(ethylene glycol) diblock copolymer (PEG-PAC) and urea-functionalized poly(carbonate) (PUC) and PEG diblock copolymer (PEG-PUC). The drug-loaded mixed micelles (MM) were used to target both cancer cells and stem cells via co-delivery. Cancer stem cells were sorted by a side population assay from BT-474 and MCF-7 human breast cancer cell lines, and identified by CD44+/CD24− phenotype. The cytotoxicity of various formulations was evaluated on the sorted cancer stem cells (side population SP cells), sorted non-stem-like cancer cells (non-side population NSP cells) and unsorted cancer cells. Antitumor activity was also evaluated on BT-474 xenografts in nude mice. As compared with NSP cells, DOX suppressed SP cell growth less effectively, while THZ and THZ-MM were more effective in the inhibition of SP cells. A stronger inhibitory effect was observed on SP cells with the co-delivery of free DOX and THZ or DOX-MM and THZ-MM as compared to free DOX or DOX-MM. THZ and THZ-MM were capable of lowering the population of SP cells in unsorted cells. In the BT-474 xenografts, the co-delivery of DOX-MM and THZ-MM produced the strongest antitumor efficacy, and both THZ and THZ-MM showed strong activity against cancer stem cells. This combination therapy may provide a promising strategy for breast cancer treatment by targeting both cancer cells and cancer stem cells.

Biotin-Encoded and Fe<sub>3</sub>O<sub>4</sub>-Loaded Polymeric Nano Micelles: Preparation, Optimization and In Vitro Characterization

Diblock copolymers of poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) bearing a biotin ligand, were self-assembled into micelles. Superparamagnetic iron oxide (SPIO) nanoparticles and an anticancer drug methotrexate (MTX) were coencapsulated within the micelles less than 100 nm in diameters. The preparation process was optimized by a systematic multi-objective-optimization approach in terms of the encapsulation ratio (ER %, Y1), drug-loading efficiency (DL %, Y2) and the percentage of MTX precipitated from the drug-loaded mixed micelles after 30min and 6h incubation at 37ºC (MTX precipitated %, Y3 and Y4) of the resulting nanocarriers. A combination of the stirring rate, ultrasonic power and drug/polymer ratio, accounted for nearly 79% of the variation in drug-loading efficiency. The final entrapment ratio, loading efficiency and MTX % precipitated corresponding to the optimal conditions were 70.938, 5.665 and 6.885 respectively. Moreover, in vitro release behavior of MTX was also investigated. The result shows, MTX is physically entrapped inside B-PEG-PCL self-aggregated nanoparticlesis. Keywords: Biotin, Drug delivery, Nano micelle, Optimization, Plackett-Burman, SoCl2.

Synergistic encapsulation of the anti-HIV agent efavirenz within mixed poloxamine/poloxamer polymeric micelles

This study investigated the synergistic performance of mixed polymeric micelles made of linear and branched poly(ethylene oxide)-poly(propylene oxide) for the more effective encapsulation of the anti-HIV drug efavirenz. The co-micellization process of 10% binary systems combining different weight ratios of a highly hydrophilic poloxamer (Pluronic F127) and a more hydrophobic poloxamine counterpart (Tetronic T304 and T904) was investigated by means of dynamic light scattering, cloud point and electronic spin resonance experiments. Then, the synergistic solubilization capacity of the micelles was shown. Findings revealed a sharp solubility increase from 4 μg/ml up to more than 33 mg/ml, representing a 8430-fold increase. Moreover, the drug-loaded mixed micelles displayed increased physical stability over time in comparison with pure poloxamine ones. Overall findings confirmed the enormous versatility of the poloxamer/poloxamine systems as Trojan nanocarriers for drug encapsulation and release by the oral route and they entail a relevant enhancement of the previous art towards a more compliant pediatric HIV pharmacotherapy. From the Clinical Editor In this study, the authors demonstrate the versatility of poloxamer/poloxamine systems as Trojan nanocarriers for anti-HIV drug encapsulation and release by the oral route. A highly relevant stability and solubility enhancement is shown, which may ultimately lead to more compliant anti-HIV pharmacotherapy.

Paclitaxel-loaded Pluronic P123/F127 mixed polymeric micelles: Formulation, optimization and in vitro characterization

The objective of this study was to optimize and characterize a novel polymeric mixed micelle composed of Pluronic P123 and F127 loaded with paclitaxel (PTX). A Doehlert matrix design was utilized to investigate the effect of four variables, namely P123 mass fraction, amount of water, feeding of PTX and hydration temperature on the responses including drug-loading coefficient (DL %), encapsulation ratio (ER %) and the percentage of PTX precipitated from the drug-loaded mixed micelles after 48 h at 37 (PTX precipitated %) for improvement of drug solubilization efficiency and micelle stability. PTX-loaded P123/F127 mixed micelles were prepared by thin-film hydration method. The optimized formulation showed a particle size of about 25 nm with ER % > 90%, and a sustained release behavior compared to Taxol. Micelle formation was confirmed by NMR spectroscopy. The mixed micelles had a low CMC of 0.0059% in water. In addition, micelle stability studies implied that introduction of Pluronic F127 (33 wt%) into P123 micelle system significantly increased the stability of PTX-loaded micelles. More importantly, in vitro cytotoxicity was assessed using human lung adenocarcinoma cell lines SPC-A1 and A-549 and was compared to Taxol and the free drug. The cell viability assay against A-549 cells exhibited the 50% inhibition concentration (IC50) of PTX-loaded P123/F127 mixed micelles (0.1 μg/ml) was much lower than those of Taxol injection (0.4 μg/ml) and the free PTX (1.7 μg/ml). Therefore, PTX-loaded P123/F127 mixed micelles may be considered as an effective anticancer drug delivery system for cancer chemotherapy.

Mixed PEG–PE/vitamin E tumor-targeted immunomicelles as carriers for poorly soluble anti-cancer drugs: Improved drug solubilization and enhanced in vitro cytotoxicity

Two poorly soluble, potent anti-cancer drugs, paclitaxel and camptothecin, were successfully solubilized by mixed micelles of polyethylene glycol–phosphatidyl ethanolamine (PEG–PE) and vitamin E. Drug-containing micelles were additionally modified with anti-nucleosome monoclonal antibody 2C5 (mAb 2C5), which can specifically bring micelles to tumor cells in vitro. The optimized micelles had an average size of about 13–22 nm and the immuno-modification of micelles did not significantly change it. The solubilization of both drugs by the mixed micelles was more efficient than by micelles made of PEG–PE alone. Solubilization of camptothecin in micelles prevented also the hydrolysis of active lactone form of the drug to inactive carboxylate form. Drug-loaded mixed micelles and mAb 2C5-immunomicelles demonstrated significantly higher in vitro cytotoxicity than free drug against various cancer cell lines.