Optimizing double emulsion process to decrease the burst release of protein from biodegradable polymer microspheres

Nanomaterial-dependent immunoregulation of dendritic cells and its effects on biological activities of contraceptive nanovaccines

Nanovehicles are promising delivery systems for various vaccines. Nevertheless, different biophysicochemical properties of nanoparticles (NPs), dominating their in vitro and in vivo performances for vaccination, remain unclear. We attempted to elucidate the effects of NPs and their pH-sensitivity on in vitro and in vivo efficacy of resulting prophylactic nanovaccines containing a contraceptive peptide (FSHR). To this end, pH-responsive and non-responsive nanovaccines were produced using acetalated β-cyclodextrin (Ac-bCD) and poly(lactic-co-glycolic acid) (PLGA), respectively. Meanwhile, FSHR derived from an epitope of the follicle-stimulating hormone receptor was used as the model antigen. FSHR-containing Ac-bCD and PLGA NPs were successfully prepared by a nanoemulsion technique, leading to well-shaped nanovaccines with high loading efficiency. The pH-sensitivity of Ac-bCD and PLGA nanovaccines was examined by in vitro hydrolysis and antigen release studies. Nanovaccines could be effectively engulfed by dendritic cells (DCs) via endocytosis in both dose and time dependent manners, and their intracellular trafficking was closely related to the pH-sensitivity of the carrier materials. Furthermore, nanovaccines could induce the secretion of inflammatory cytokines by DCs and T cells co-cultured with the stimulated DCs. In vivo evaluations demonstrated that nanovaccines were more potent than that based on the complete Freund's adjuvant, with respect to inducing anti-FSHR antibody, reducing the sperm count, inhibiting the sperm motility, and increasing the teratosperm rate. Immunization of male mice with nanovaccines notably decreased the parturition incidence of the mated females. Consequently, both in vitro and in vivo activities of FSHR could be considerably augmented by NPs. More importantly, our studies indicated that the pH-responsive nanovaccine was not superior over the non-responsive counterpart for the examined peptide antigen.

Multiple noncovalent interactions mediated one-pot therapeutic assemblies for the effective treatment of atherosclerosis

Therapeutic microspheres are engineered by multiple noncovalent interactions mediated one-pot assembly, which may serve as effective and safe therapeutics for atherosclerosis.

Inhibition of hypoxia-induced proliferation of pulmonary arterial smooth muscle cells by a mTOR siRNA-loaded cyclodextrin nanovector

The proliferation of pulmonary arterial smooth muscle cells (PASMCs) is a key pathophysiological component of vascular remodeling in pulmonary arterial hypertension (PAH), an intractable disease, for which pharmacotherapy is limited and only slight improvement in survival outcomes have achieved over the past few decades. RNA interference provides a highly promising strategy to the treatment of this chronic lung disease, while efficient delivery of small interfering RNA (siRNA) remains a key challenge for the development of clinically acceptable siRNA therapeutics. With the aim to construct useful nanomedicines, the mammalian target of rapamycin (mTOR) siRNA was loaded into hybrid nanoparticles based on low molecular weight (Mw) polyethylenimine (PEI) and a pH-responsive cyclodextrin material (Ac-aCD) or poly(lactic-co-glycolic acid) (PLGA). This hybrid nanoplatform gave rise to desirable siRNA loading, and the payload release could be modulated by the hydrolysis characteristics of carrier materials. Fluorescence observation and flow cytometry quantification suggested that both Ac-aCD and PLGA nanovectors (NVs) may enter PASMCs under either normoxia or hypoxia conditions as well as in the presence of serum, with uptake and transfection efficiency significantly higher than those of cationic vectors such as PEI with Mw of 25 kDa (PEI25k) and Lipofectamine 2000 (Lipo 2k). Hybrid Ac-aCD or PLGA NV containing siRNA remarkably inhibited proliferation and activated apoptosis of hypoxic PASMCs, largely resulting from effective suppression of mTOR signaling as evidenced by significantly lowered expression of mTOR mRNA and phosphorylated protein. Moreover, these hybrid nanomedicines were more effective than commonly used cationic vectors like PEI25k and Lipo 2k, with respect to cell growth inhibition, apoptosis activation, and expression attenuation of mTOR mRNA and protein. Therefore, mTOR siRNA nanomedicines based on hybrid Ac-aCD or PLGA NV may be promising therapeutics for diseases related to hypoxic abnormal growth of PASMCs.

A pH-responsive cyclodextrin-based hybrid nanosystem as a nonviral vector for gene delivery

The absence of safe, efficient, cost-effective, and easily scalable delivery platforms is one of the most significant hurdles and critical issues that limit the bench to bedside translation of oligonucleotides-based therapeutics. Acid-labile materials are of special interest in developing nonviral vectors due to their capability of intracellularly delivering therapeutic payload. In this study, a nanovector was designed by integrating a pH-responsive cyclodextrin material and low molecular weight polyethylenimine (PEI). Antisense oligonucleotide (ASON) Bcl-xl could be encapsulated into this hybrid nanosystem with extremely high loading efficiency by a nanoemulsion technique. The developed pH-responsive ASON nanotherapeutics could be efficiently transfected into human lung adenocarcinoma cells in a time- and dose-dependent manner, resulting in effective cell growth inhibition, significant suppression on the expression of Bcl-xl mRNA/protein, and efficient cell apoptosis. Importantly, the new nanovector showed drastically higher efficacy and lower cytotoxicity when compared with PLGA-based counterpart and commonly used cationic vectors like branched PEI (25,000 Da) and Lipofectamine 2000. This pH-responsive hybrid nanosystem may serve as a safe and efficient nonviral vector that may find wide applications in gene therapy.

Modification of the release characteristics of estradiol encapsulated in PLGA particles via surface coating

Background: Drug-loaded poly(lactide-co-glycolide) particles (100–4500 nm in diameter) were prepared via the electrospraying method. An extensive study was then carried out to determine the parameters affecting the release profile of estradiol (the drug or active pharmaceutical ingredient) in order to facilitate minimum initial burst release of estradiol. Results and discussion: The three most important factors affecting estradiol release were identified as: particle size, coating of the particles with chitosan/gelatin and the concentration of the coating agent. It was shown that coating the particles with chitosan significantly reduced the burst and initial release without affecting the subsequent release profile. Conclusions: This work demonstrates a powerful method of generating drug-loaded polymeric particles with modified release behavior and control over the initial release phase. The surface-modified particles may be useful in controlled therapeutic delivery systems to minimize undesirable side effects.

Effect of PLGA hydrophilia on the drug release and the hypoglucemic activity of different insulin-loaded PLGA microspheres

The effects of viscosity and hydrophilic characteristics of different PLGA polymers on the microencapsulation of insulin have been studied in vitro and in vivo after subcutaneous administration to hyperglycemic rats. Hydrophilic PLGA polymers produced a higher burst effect than the hydrophobic ones. Moreover, an incomplete insulin release was observed with the hydrophilic PLGA polymers in comparison with the hydrophobic ones. An explanation for that incomplete release can be the development of polymer-insulin interactions associated to the polymer hydrophilic/hydrophobic character, as detected by DSC analysis. Differences in the release rate of microsphere formulations lead to differences in the hypoglycemic action and the weight of animals. Hydrophobic PLGA was able to prolong the hypoglycemic action up to 4 weeks which is at least double than that obtained with hydrophilic PLGA of a similar viscosity. Comparing insulin microspheres with an immediate release formulation, microspheres can increase insulin relative bioavailability up to four times.

Preparation of Protein-Loaded Poly(L-Lactide) Microspheres by Solution-Enhanced Dispersion by Supercritical CO2

SiO2-hemoglobin-poly(L-lactide) (SiO2-Hb-PLLA) microspheres were prepared in a process of solution-enhanced dispersion by supercritical CO2 (SEDS). SiO2 nanoparticles were loaded with Hb by adsorption firstly and then the Hb-SiO2 nanoparticles were further coated with PLLA by the SEDS process. The resulted microcapsules were characterized by scanning electron microscope (SEM), laser diffraction particle size analyser and Fourier transform infrared spectrometer (FTIR). The drug release profiles were also determined. The Hb-SiO2-PLLA microspheres have a narrow particle size distribution (PDI 0.189) with a mean particle size of 897nm and a drug loading of 7.1%. After coating with PLLA, the drug release from SiO2-Hb-PLLA showed a sustained process mainly in zero-order kinetics; only 3.7% drug was released in the first 24 hours, versus 51.9% for those without coating, which revealed that the coating of PLLA significantly retarded the drug release. The results also indicate that the SEDS process is a typical physical process to produce protein-loaded polymer microspheres without changing the molecular structure of proteins, which is potential in the application of designing proteins drug delivery system.

Formulation and characterization of the microencapsulated entomopathogenic fungus Metarhizium anisopliae MA126

Bioinsecticides are expected to be used for controlling major species of aphids. The present study explored a liquid phase coating technique for the formulation of microencapsulated conidia of the entomopathogenic fungus Metarhizium anisopliae MA126. Various parameters for microencapsulation were investigated. The biopolymers sodium alginate, hydroxypropyl methyl cellulose (HPMC) and chitosan were tested as coating materials. Calcium chloride was used as the cross-linking agent for converting soluble sodium alginate into an insoluble form. To improve the efficiency of microencapsulation, the additives of HPMC, dextrin, chitosan or HPMC/chitosan in various ratios (1 : 1, 1 : 3 and 3 : 1) were used as the coating materials. The particle size of a bare microcapsule was less than 30 microm. Larger size microcapsules were produced using vortex method by comparison with that using homogenization method. The latter method, however, was easy to scale up. The effect of coating materials on the morphology and encapsulation efficiency of the microcapsules was also studied. The best encapsulation efficiency (78%) was using HPMC as the additive of the coating material. The next was dextrin (70%). By measuring the germination rate, the results showed that the activity was approximately 80% of the initial after 6 months of storage at 4 degrees C, while that of the bare conidia was less than 50% stored in identical conditions.

Claudin 4-targeted protein incorporated into PLGA nanoparticles can mediate M cell targeted delivery

Polymer-based microparticles are in clinical use mainly for their ability to provide controlled release of peptides and compounds, but they are also being explored for their potential to deliver vaccines and drugs as suspensions directly into mucosal sites. It is generally assumed that uptake is mediated by epithelial M cells, but this is often not directly measured. To study the potential for optimizing M cell uptake of polymer microparticles in vivo, we produced sub-micron size PLGA particles incorporating a recombinant protein. This recombinant protein was produced with or without a c-terminal peptide previously shown to have high affinity binding to Claudin 4, a protein associated with M cell endocytosis. While the PLGA nanoparticles incorporate the protein throughout the matrix, much of the protein was also displayed on the surface, allowing us to take advantage of the binding activity of the targeting peptide. Accordingly, we found that instillation of these nanoparticles into the nasal passages or stomach of mice was found to significantly enhance their uptake by upper airway and intestinal M cells. Our results suggest that a reasonably simple nanoparticle manufacture method can provide insight into developing an effective needle-free delivery system.

Transplanted bone morphogenetic protein/poly(lactic-co-glycolic acid) delayed-release microcysts combined with rat micromorselized bone and collagen for bone tissue engineering

This study was designed to optimize the preparation of delayed-release microcysts containing bone morphogenetic protein 2 (BMP-2) combined with poly(lactic-co-glycolic acid) (PLGA) and to investigate their osteogenic properties when combined with rat autologous micromorselized bone and collagen. Rat autologous micromorselized bone, collagen and BMP-2/PLGA delayed-release microcysts were implanted in various combinations into the rat gluteus maximus muscle sack model. The following post-operative measurements were made: general observations of the implant site, histological observations, osteogenesis measurements and alkaline phosphatase activity. Autologous micromorselized bone combined with collagen and BMP-2/PLGA delayed-release microcysts demonstrated significantly superior osteogenic properties than any of the other combinations of these three components. These findings suggest that micromorselized bone combined with collagen and BMP-2/PLGA delayed-release microcysts could reduce the quantity of BMP-2 and autologous bone required for these procedures, making their use feasible in human bone restoration.

A study of properties of "micelle-enhanced" polyelectrolyte capsules: Structure, encapsulation and in vitro release

"Micelle-enhanced" polyelectrolyte capsules were fabricated via a layer-by-layer technique, templated on hybrid calcium carbonate particles with built-in polymeric micelles based on polystyrene-b-poly(acrylic acid). Due to the presence of a large number of negatively charged micelles inside the polyelectrolyte capsule, which were liberated from templates, the capsule wall was reconstructed and had properties different to those of conventional polyelectrolyte capsules. This type of capsule could selectively entrap positively charged water-soluble substances. The encapsulation efficiency of positively charged substances was dependent on their molecular weight or size. For some positively charged compounds, such as rhodamine B and lysozyme, the concentration in the capsules was orders of magnitude higher than that in the incubation solution. In addition, in vitro release study suggested that the encapsulated compounds could be released through a sustained manner to a certain degree. All these results point to the fact that these capsules might be used as novel delivery systems for some water-soluble compounds.

Preparation and in vitro Evaluation of Linear and Star-branched PLGA Nanoparticles for Insulin Delivery

Biodegradable nanoparticles, as drug delivery paradigms, have been extensively used for delivery of a wide range of small molecules as well as macromolecules, such as peptides, proteins, and genes. The morphological modification may improve the physicochemical characteristics of the biodegradable polymers. In the current investigation, the synthesis and characterization of linear, poly(D,L-lactide-co-glycolide) (PLGA)-poly(ethylene glycol) (PEG-PLGA), star-branched β-cyclodextrin-PLGA (β-CD-PLGA), and glucose-PLGA (Glu-PLGA) copolymers containing insulin as a model peptide drug have been reported. Linear and star-branched copolymers of PLGA were synthesized by bulk melt polymerization of the lactones (lactide and glycolide) in the presence of PEG, glucose, or β-CD using Sn-octoate as catalyst. Nanoparticles were prepared by a modified (w1/o/w 2) double emulsion method. Bovine insulin was successfully encapsulated into the linear and star-branched PLGA nanoparticles with retention of insulin stability and the nanoparticles preparation process was optimized to reduce the burst effect and provide in vitro sustained release. The average particle size of samples was 120—355 nm. The cumulative amount of 65—84% insulin was released from the samples after 24 days. The yield of encapsulation of insulin was superior to 95%. Based on these findings, it is suggested that the novel PLGA nanoparticles can be used as a carrier for prolonged delivery of protein—peptide drugs.

Preparation and release characteristics of insulin and insulin-like growth factor-one from polymer nanoparticles

Two methods of preparing polymer nanoparticles containing (a) insulin and (b) insulin-like growth factor-1 were compared and the influence of process parameters on size and release characteristics was determined. Poly(lactide-glycolide)co-polymer (50:50) was used in both methods. Method one used a salting-out process; while method two used a solvent evaporation/double emulsion procedure forming a w/o/w secondary emulsion. Particles were separated by centrifugation and dried under vacuum. Particle size was analysed by scanning electron microscopy and protein release by dissolution and high pressure liquid chromatography. Method one produced particles of diameter 0.3-0.8 microm, whereas method two gave larger particles of 0.76-1.05 microm and in both procedures reducing pH also decreased particle size. Optimal emulsifying speed was below 4 000 rpm and scanning electron micrographs showed smooth spherical particles. Release characteristics of insulin and IGF-1 in method one and two were similar releasing 60% in 10 days but in method one release was diminished to 8% over a similar time period. Method one proved successful in producing spheres of the required size range but hampered protein loading by denaturation resulting in a low release rate. Method two provided an acceptable release rate but produced particles with diameters of about one micron.

Versatile preparation of fluorescent particles based on polyphosphazenes: from micro- to nanoscale

A series of intrinsically fluorescent hydrophobic and amphiphilic polyphosphazenes with ethyl tryptophan (EtTrp) and poly(N-isopropylacrylamide) (PNIPAAm) or poly(ethylene glycol) (PEG) as hydrophobic and hydrophilic segments, respectively, are synthesized. Depending on polymer composition and preparation procedure, particles with diameters ranging from micro- to nanoscale can be prepared successfully, which might be used as a visible tracer, both in vitro or in vivo, in drug- or gene-delivery systems, as well as in other biomedical studies such as diagnostic medicine and brain research. Most importantly, in combination with the flexible synthesis and versatile modification of polyphosphazene, this method provides a general protocol to engineer a broad range of fluorescent particles with different properties based on diverse polymers.

HRP-Loaded Bioresorbable Microspheres: Effect of Copolymer Composition and Molecular Weight on Microstructure and Release Profile

Poly(DL-lactic-co-glycolic acid) microspheres are prepared using a double-emulsion technique and are loaded with the model enzyme horseradish peroxidase (HRP). These microspheres can be used alone or as coatings for bioresorbable fibers that may be used as scaffolds for tissue regeneration applications. The present study focuses on the effect of the copolymer's composition and initial molecular weight on the microsphere structure, encapsulation efficiency, and cumulative protein release for 12 weeks. The release profiles generally exhibits an initial burst effect accompanied by slow release over an extended period of time, during which diffusion rather than degradation controlled HRP release from these structures. An increase in the initial molecular weight or in the copolymer's lactic acid content results in larger microspheres with smoother surfaces, and a decrease in the burst release and in the total HRP release. Molecular weight is found to have a stronger effect than copolymer composition. We demonstrate that it is possible to obtain versatile release profiles, which can be tailored for specific applications by choosing the right initial molecular weight and copolymer composition.