Taxol-loaded block copolymer nanospheres composed of methoxy poly(ethylene glycol) and poly(epsilon-caprolactone) as novel anticancer drug carriers

Janus nanogels of PEGylated Taxol and PLGA-PEG-PLGA copolymer for cancer therapy

Nanogels are promising carriers for the delivery of anti-cancer drugs for cancer therapy. We report in this study on a Janus nanogel system formed by mixing a prodrug of Taxol (PEGylated Taxol) and a copolymer of PLGA-PEG-PLGA. The Janus nanogels have good stability over months in aqueous solutions and the freeze-dried powder of nanogels can be re-dispersed instantly in aqueous solutions. The Janus nanogels show an enhanced inhibition effect on tumor growth in a mice breast cancer model probably due to the enhanced uptake of the nano-sized materials by the EPR effect. What is more, the nanogels can also serve as physical carriers to co-deliver other anti-cancer drugs such as doxorubicin to further improve the anti-cancer efficacy. The results obtained from H&E staining and TUNEL assay also support the observation of tumor growth inhibition. These results suggest the potential of this novel delivery system for cancer therapy.

Biphasic magnetic nanoparticles-nanovesicle hybrids for chemotherapy and self-controlled hyperthermia

AIM

The aim was to develop magnetic nanovesicles for chemotherapy and self-controlled hyperthermia that prevent overheating of tissues.

MATERIALS & METHODS

Magnetic nanovesicles containing paclitaxel and a dextran-coated biphasic suspension of La0.75Sr0.25MnO3 and Fe3O4 nanoparticles (magnetic nanoparticles) were developed.

RESULTS

Encapsulation efficiencies of magnetic nanoparticles and paclitaxel were 67 ± 5 and 83 ± 3%, respectively. Sequential release performed at 37°C for 1 h followed by 44°C for another 1 h (as expected for intratumoral injection), showed a cumulative release of 6.6% (109.6 µg), which was above the IC50 of the drug. In an alternating current magnetic field, the temperature remained controlled at 44°C and a synergistic cytotoxicity of paclitaxel and hyperthermia was observed in MCF-7 cells.

CONCLUSION

Magnetic nanovesicles containing biphasic suspensions La0.75Sr0.25MnO3 and Fe3O4 nanoparticles encapsulating paclitaxel have potential for combined self-controlled hyperthermia and chemotherapy.

A review of block copolymer-based biomaterials that control protein and cell interactions

Block copolymers posses the ability to phase separate into micro and nanoscale patterns resulting in nonhomogeneous surfaces and solids. This nonhomogeneity has been harnessed to improve mechanical properties, control degradation, and add functionality to biomaterials. The ability of block copolymers to generate a wide variety of surface chemistries and morphologies can also be harnessed to control protein adsorption, protein conformation, and cell adhesion. Proteins and cells will respond to periodically structured surfaces, so block copolymers have a great deal of potential as biomaterials. This review will explore the ability of block copolymers to control specific biological responses such as cell adhesion, protein adsorption and conformation, parameters that govern the overall host response to a material. In addition, some of the specific applications of block copolymer, antithrombogenic materials and their ability to pattern proteins, will be discussed.

Specific targeting of cancer cells by multifunctional mitoxantrone-conjugated magnetic nanoparticles

We report on the synthesis of bifunctional mitoxantrone (MTX)-grafted magnetic nanoparticles (MNPs) modified by dopamine-polyethylene glycol-folic acid (DPA-PEG-FA) for targeted imaging and therapy of cancer. MNPs (~7-10 nm) were synthesized using the thermal decomposition reaction of Fe(acac)3. Bromoacetyl (BrAc) terminal polyethylene glycol dopamine (DPA-PEG-BrAc) was synthesized and treated with ethylene diamine to form bifunctional PEG moiety containing dopamine at one end and amino group at the other end (i.e. DPA-PEG-NH2). It was then reacted with Fe3O4 nanoparticles (NPs) to form Fe3O4-DPA-PEG-NH2 NPs. The activated folic acid (FA) was chemically coupled to Fe3O4-DPA-PEG-NH2, forming Fe3O4-DPA-PEG-FA. MTX was then conjugated to Fe3O4-DPA-PEG-FA, forming Fe3O4-DPA-PEG-FA-MTX. Physicochemical characteristics of the engineered MNPs were determined. The particle size analysis and electron microscopy showed an average size of ~35 nm for Fe3O4-DPA-PEG-FA-MTX NPs with superparamagnetic behavior. FT-IR spectrophotometry analysis confirmed the conjugation of FA and MTX onto the MNPs. Fluorescence microscopy, cytotoxicity assay and flow cytometry analysis revealed that the engineered Fe3O4-DPA-PEG-FA-MTX NPs were able to specifically bind to and significantly inhibit the folate receptor (FR)-positive MCF-7 cells, but not the FR-negative A549 cells. Based upon these findings, we suggest the Fe3O4-DPA-PEG-FA-MTX NPs as an effective multifunctional-targeted nanomedicine toward simultaneous imaging and therapy of FR-positive cancers.

Self-assembled photosensitizer-conjugated nanoparticles for targeted photodynamic therapy

An effective tumor-targeted drug delivery system for photodynamic therapy was developed by designing ligand-mediated nanoparticles with stable formulations of a hydrophobic photosensitizer. Novel folic acid (FA)-conjugated amphiphilic block copolymers of polyethylene glycol (PEG) and poly-β-benzyl-L-aspartate (PBLA) with the potential to act as pH-responsive drug release reservoirs were synthesized. The photosensitizer, 2,4-diacetyl deuteroporphyrin IX dimethyl ether (DD-PpIX), was conjugated to the copolymers through pH-sensitive hydrazone linkage. The syntheses and compositions of all copolymers were confirmed by 1H NMR measurement. Photosensitizer-conjugated amphiphilic copolymeric nanoparticles (FA-PEG-P(Asp-Hyd)-DD-PpIX) were prepared by micelle formation in aqueous solution. The particle sizes of the FA-PEG-PBLA and FA-PEG-P(Asp-Hyd)-DD-PpIX nanoparticles were determined by light-scattering measurements. The range was 105–298 nm, depending on copolymer molecular weight and composition. Field emission scanning electron microscopy showed that the FA-PEG-P(Asp-Hyd)-DD-PpIX copolymeric nanoparticles were submicron in size and spherical in shape. The results of in vitro release tests showed that the release profiles of DD-PpIX from the nanoparticles were strongly pH-dependent and influenced by the amount of photosensitizer that was conjugated. In vitro tests using HeLa cells indicated that the FA-PEG-P(Asp-Hyd)-DD-PpIX nanoparticles had low dark-toxicity and showed more than 97% of cellular uptake. Based on our results, the FA-PEG-P(Asp-Hyd)-DD-PpIX nanoparticle system could be a promising approach for developing novel photosensitizer delivery carriers for photodynamic therapy.

Poly(caprolactone)-modified Pluronic P105 micelles for reversal of paclitaxcel-resistance in SKOV-3 tumors

Three poly(caprolactone)-modified Pluronic P105 polymers (P105/PCLs) were synthesized using commercially available ε-caprolactone monomers and Pluronic P105 copolymers. The chemical structures, compositions and molecular weights of the P105/PCLs were confirmed by FT-IR, (1)H NMR and GPC measurements. Three paclitaxel (PTX)-loaded P105/PCL polymeric micelles were then prepared, and they showed average diameters in the range of 30-150 nm, drug-loading coefficients of 0.15%-5.43%, and encapsulation ratios of 2.1%-76.53%. The in vitro cytotoxicity assay demonstrated that three PTX-loaded P105/PCL micelles were able to sensitize the resistant SKOV-3/PTX tumor cells. The PTX-loaded P105/PCL(50) micelle was then selected for an in vivo antitumor efficacy study. The tumor volumes in nude mice bearing s.c. resistant SKOV-3/PTX carcinoma treated with this micellar PTX were significantly less than the control group treated with Taxol. It was demonstrated that three PCL-modified P105 monomers and micelles inhibited P-gP efflux activity in the resistant SKOV-3/PTX cells via at least three intracellular events: 1) inhibition of ATPase of P-gP, 2) decrease of membrane microviscosity and 3) a loss of mitochondrial membrane potential and subsequent decrease of ATP levels at the concentration of monomers (0.001%) and/or micelles (0.01-1.0%). Considering other favorable characteristics, such as sustained PTX release in vitro, long-circulating time in vivo and increased PTX concentration in the tissues of ovaries and uterus in mice, the PCL-modified Pluronic P105 polymeric micelle system could have important clinical implications for delivery of paclitaxel and treatment of the resistant ovarian tumors.

Biodegradable nanoparticles are excellent vehicle for site directed in-vivo delivery of drugs and vaccines

Biodegradable nanoparticles (NPs) are gaining increased attention for their ability to serve as a viable carrier for site specific delivery of vaccines, genes, drugs and other biomolecules in the body. They offer enhanced biocompatibility, superior drug/vaccine encapsulation, and convenient release profiles for a number of drugs, vaccines and biomolecules to be used in a variety of applications in the field of medicine. In this manuscript, the methods of preparation of biodegradable NPs, different factors affecting optimal drug encapsulation, factors affecting drug release rates, various surface modifications of nanoparticles to enhance in-vivo circulation, distribution and multimodal functionalities along with the specific applications such as tumor targeting, oral delivery, and delivery of these particles to the central nervous system have been reviewed.

Nanocapsules based on linear and Y-shaped 3-miktoarm star-block PEO-PCL copolymers as sustained delivery system for hydrophilic molecules

Well-defined amphiphilic Y-shaped miktoarm star-block copolymers of PEO and PCL were synthesized by ring-opening polymerization of ε-caprolactone initiated by a PEO-bound lysine macroinitiator. The copolymers were characterized by (1)H NMR, SEC, DSC, and WAXD techniques. Separate PCL and PEO crystalline phases occur in melt-crystallized copolymers when their segmental lengths were comparable and the PCL content was ≤80 wt %. Self-assembling of these copolymers in aqueous medium led to nanoaggregates with low critical aggregation concentration values (0.35 to 1.6 mg·L(-1)) and size depending on composition. Despite the fact that copolymers were not prone to self-organize in vesicles, once processed by a novel w/o emulsion-melting-sonication technique, they gave nanocapsules with a water core and a hydrophilic surface. A macromolecular fluorescent dye was effectively loaded and released at sustained rate by optimizing nanocapsule formulation. The results demonstrate that amphiphilic block copolymers can be assembled in different kinds of nanomorphologies independently of their hydrophilic/hydrophobic balance and architecture through specifically designed preparation techniques.

Polycaprolactone microspheres as carriers for dry powder inhalers: effect of surface coating on aerosolization of salbutamol sulfate

This study reports the factors controlling aerosolization of salbutamol sulfate (SS) from mixtures with polycaprolactone (PCL) microspheres fabricated using an emulsion technique with polyvinyl alcohol (PVA) as stabilizer. The fine particle fraction (FPF) of SS from PCL measured by a twin-stage impinger was unexpectedly found to be zero, although scanning electron microscopy showed that the drug coated the entire microsphere. Precoating the microspheres with magnesium stearate (MgSt) excipient solutions (1%-2%) significantly increased (p < 0.05, n = 5) the FPF of SS (11.4%-15.4%), whereas precoating with leucine had a similar effect (FPF = 11.3 ± 1.1%), but was independent of the solution concentration. The force of adhesion (by atomic force microscopy) between the PCL microspheres and SS was reduced from 301.4 ± 21.7 nN to 110.9 ± 30.5 nN and 121.8 ± 24.6 nN, (p < 0.05, n = 5) for 1% and 2% MgSt solutions, respectively, and to 148.1 ± 21.0 nN when coated with leucine. The presence of PVA on the PCL microspheres (detected by X-ray photoelectron spectroscopy) affected the detachment of SS due to strong adhesion between the two, presumably due to capillary forces acting between them. Precoating the microspheres with excipients increased the FPF significantly by reducing the drug-carrier adhesion.

EILDV-conjugated, etoposide-loaded biodegradable polymeric micelles directing to tumor metastatic cells overexpressing α4β1 integrin

In the present study, poly(ethylene glycol)-b-poly(ε-caprolactone) micelles loaded with etoposide (ETO) were formulated and further conjugated with pentapeptide Glu-Ile-Leu-Asp-Val (EILDV) to target α4β1 integrin receptor overexpressed on metastatic tumor cell. Using a distinct ratio of carboxyl-terminated poly(ethylene glycol)-block-poly(ε-caprolactone) (HOOC-PEG-b-PCL) to methoxy-poly(ethylene glycol)-block-poly(ε-caprolactone (CH₃O-PEG-b-PCL) polymers, we formulated a series of micellar formulations having different surface densities of EILDV and observed optimum cellular uptake of micelles with 10% EILDV surface density by B16F10 cells. The cytotoxicity of EILDV-conjugated micelles was observed close to 1.5-fold higher than plain ETO after 72 h of drug incubation, demonstrating controlled release of drug inside the cell after enhanced intracellular uptake with the ability to selectively target cancer cells. In addition, EILDV-conjugated micelles inhibited the migration of B16F10 cells effectively compared with plain ETO and non-conjugated micellar formulations when cells were treated with equivalent cytotoxic concentration of the drug, i.e., IC₂₅. B16F10 cells treated with EILDV-conjugated micelles showed a significant reduction in the attachment of cells to the substrate-coated plate compared with non-conjugated micellar formulations, implying retention of the biological activity of EILDV after coupling to micelles. Furthermore, the in vivo experimental metastasis assay conducted on C57BL/6 mice demonstrated significant activity of EIDLV-conjugated micelles in the reduction of pulmonary metastatic nodule formation in both pretreatment and post-treatment methods. In conclusion, EIDLV-conjugated micelles showed higher efficacy in the treatment of metastasis and would be a promising approach in the treatment of metastasis.

A comparison of implicit- and explicit-solvent simulations of self-assembly in block copolymer and solute systems

We have developed explicit- and implicit-solvent models for the flash nanoprecipitation process, which involves rapid coprecipitation of block copolymers and solutes by changing solvent quality. The explicit-solvent model uses the dissipative particle dynamics (DPD) method and the implicit-solvent model uses the Brownian dynamics (BD) method. Each of the two models was parameterized to match key properties of the diblock copolymer (specifically, critical micelle concentration, diffusion coefficient, polystyrene melt density, and polyethylene glycol radius of gyration) and the hydrophobic solute (aqueous solubility, diffusion coefficient, and solid density). The models were simulated in the limit of instantaneous mixing of solvent with antisolvent. Despite the significant differences in the potentials employed in the implicit- and explicit-solvent models, the polymer-stabilized nanoparticles formed in both sets of simulations are similar in size and structure; however, the dynamic evolution of the two simulations is quite different. Nanoparticles in the BD simulations have diffusion coefficients that follow Rouse behavior (D ∝ M(-1)), whereas those in the DPD simulations have diffusion coefficients that are close to the values predicted by the Stokes-Einstein relation (D ∝ R(-1)). As the nanoparticles become larger, the discrepancy between diffusion coefficients grows. As a consequence, BD simulations produce increasingly slower aggregation dynamics with respect to real time and result in an unphysical evolution of the nanoparticle size distribution. Surface area per polymer of the stable explicit-solvent nanoparticles agrees well with experimental values, whereas the implicit-solvent nanoparticles are stable when the surface area per particle is roughly two to four times larger. We conclude that implicit-solvent models may produce questionable results when simulating nonequilibrium processes in which hydrodynamics play a critical role.

A novel chitosan-poly(lactide) copolymer and its submicron particles as imidacloprid carriers

BACKGROUND

The aim of the present work was to synthesise novel amphiphilic chitosan-co-(D,L-lactide) (chitosan-PLA) copolymers and to study the formation of pesticide-loaded polymeric submicron particles. These copolymeric submicron particle systems are expected to be potential candidates for applications in pesticide delivery.

RESULTS

The chemical structures of the copolymers were confirmed by Fourier transform infrared spectroscopy (FT-IR), (1) H nuclear magnetic resonance ((1) H NMR) and thermogravimetric analysis (TGA). Imidacloprid as a lipophilic model pesticide can be incorporated into chitosan-PLA submicron particles by nanoprecipitation and the emulsion/solvent evaporation method. Size, the size distribution, the imidacloprid loading content (LC) and the imidacloprid release behaviour were investigated.

CONCLUSION

Conjugation of PLA to chitosan was shown to be an available method for the preparation of submicron particles for lipophilic pesticide delivery. The imidacloprid-loaded submicron particles showed a sustained release process. As the mass ratio of copolymer to imidacloprid increased, the submicron particles size and LC decreased. The chitosan-PLA submicron particles could be useful as pesticide carriers for imidacloprid delivery systems.

Polylactide-co-glycolide nanoparticles for controlled delivery of anticancer agents

The effectiveness of anticancer agents may be hindered by low solubility in water, poor permeability, and high efflux from cells. Nanomaterials have been used to enable drug delivery with lower toxicity to healthy cells and enhanced drug delivery to tumor cells. Different nanoparticles have been developed using different polymers with or without surface modification to target tumor cells both passively and/or actively. Polylactide-co-glycolide (PLGA), a biodegradable polyester approved for human use, has been used extensively. Here we report on recent developments concerning PLGA nanoparticles prepared for cancer treatment. We review the methods used for the preparation and characterization of PLGA nanoparticles and their applications in the delivery of a number of active agents. Increasing experience in the field of preparation, characterization, and in vivo application of PLGA nanoparticles has provided the necessary momentum for promising future use of these agents in cancer treatment, with higher efficacy and fewer side effects.

Nanostructured delivery system for zinc phthalocyanine: preparation, characterization, and phototoxicity study against human lung adenocarcinoma A549 cells

In this study, zinc phthalocyanine (ZnPc) was loaded onto poly-ɛ-caprolactone (PCL) nanoparticles (NPs) using a solvent emulsification–evaporation method. The process yield and encapsulation efficiency were 74.2% ± 1.2% and 67.1% ± 0.9%, respectively. The NPs had a mean diameter of 187.4 ± 2.1 nm, narrow distribution size with a polydispersity index of 0.096 ± 0.004, zeta potential of −4.85 ± 0.21 mV, and spherical shape. ZnPc has sustained release, following Higuchi’s kinetics. The photobiological activity of the ZnPc-loaded NPs was evaluated on human lung adenocarcinoma A549 cells. Cells were incubated with free ZnPc or ZnPc-loaded NPs for 4 h and then washed with phosphate-buffered saline. Culture medium was added to the wells containing the cells. Finally, the cells were exposed to red light (660 nm) with a light dose of 100 J/cm². The cellular viability was determined after 24 h of incubation. ZnPc-loaded NPs and free photosensitizer eliminated about 95.9% ± 1.8% and 28.7% ± 2.2% of A549 cells, respectively. The phototoxicity was time dependent up to 4 h and concentration dependent at 0–5 μg ZnPc. The cells viability decreased with the increase of the light dose in the range of 10–100 J/cm². Intense lysis was observed in the cells incubated with the ZnPcloaded NPs and irradiated with red light. ZnPc-loaded PCL NPs are the release systems that promise photodynamic therapy use.

Synthesis and antitumor activity of stearate-g-dextran micelles for intracellular doxorubicin delivery

Stearate-g-dextran (Dex-SA) was synthesized via an esterification reaction between the carboxyl group of stearic acid (SA) and hydroxyl group of dextran (Dex). Dex-SA could self-assemble to form nanoscaled micelles in aqueous medium. The critical micelle concentration (CMC) depended on the molecular weight of Dex and the graft ratio of SA, which ranged from 0.01 to 0.08 mg mL(-1). Using doxorubicin (DOX) as a model drug, the drug encapsulation efficiency (EE%) using Dex-SA with 10 kDa molecular weight of Dex and 6.33% graft ratio of SA could reach up to 84%. In vitro DOX release from DOX-loaded Dex-SA micelles (Dex-SA/DOX) could be prolonged to 48 h, and adjusted by a different molecular weight of Dex, the graft ratio of SA, or the drug-loading content. Tumor cellular uptake test indicated that Dex-SA micelles had excellent internalization ability, which could deliver DOX into tumor cells. In vitro cytotoxicity tests demonstrated the Dex-SA/DOX micelles could maintain the cytotoxicity of commercial doxorubicin injection against drug-sensitive tumor cells. Moreover, Dex-SA/DOX micelles presented reversal activity against DOX-resistant cells. In vivo antitumor activity results showed that Dex-SA/DOX micelles treatments effectively suppressed the tumor growth and reduced the toxicity against animal body compared with commercial doxorubicin injection.

Enzyme-assisted formation of nanosphere: a potential carrier for hydrophobic compounds

In this study, we report the use of a phosphatase to catalyze the formation of nanospheres from a hydrophobic compound (Ada-GFFY-OMe, 2) via a unique mechanism. The nanospheres were stable in aqueous solutions for two weeks. Their size could be controlled by both concentrations of the precursor (Ada-GFFY(p)-OMe, 1) and the enzyme and the nanospheres were characterized by SEM and dynamic light scattering (DLS). We then demonstrated that nanospheres could help the cell-impermeable propidium iodine (PI) to penetrate the cells, which implied that the nanospheres have the potential to be developed into useful carriers for hydrophobic drugs. This study offers the first example of using an enzyme to control the formation of nanospheres from a hydrophobic compound. There is thus the potential that nanospheres can be developed into a carrier for hydrophobic drugs.

Self-Assembled Hydrogel Nanoparticles for Drug Delivery Applications

Hydrogel nanoparticles—also referred to as polymeric nanogels or macromolecular micelles—are emerging as promising drug carriers for therapeutic applications. These nanostructures hold versatility and properties suitable for the delivery of bioactive molecules, namely of biopharmaceuticals. This article reviews the latest developments in the use of self-assembled polymeric nanogels for drug delivery applications, including small molecular weight drugs, proteins, peptides, oligosaccharides, vaccines and nucleic acids. The materials and techniques used in the development of self-assembling nanogels are also described.

Biodegradable polymeric nanoparticles based drug delivery systems

Biodegradable nanoparticles have been used frequently as drug delivery vehicles due to its grand bioavailability, better encapsulation, control release and less toxic properties. Various nanoparticulate systems, general synthesis and encapsulation process, control release and improvement of therapeutic value of nanoencapsulated drugs are covered in this review. We have highlighted the impact of nanoencapsulation of various disease related drugs on biodegradable nanoparticles such as PLGA, PLA, chitosan, gelatin, polycaprolactone and poly-alkyl-cyanoacrylates.