Hiromitsu Yamamoto

Improved cellular uptake of chitosan-modified PLGA nanospheres by A549 cells.

The authors have previously developed poly(DL-lactic-co-glycolic acid) (PLGA) nanospheres (NSs) as a nanoparticulate drug carrier for pulmonary administration. The present study demonstrates that chitosan (CS)-modified PLGA NSs (CS-PLGA NSs) are preferentially taken up by human lung adenocarcinoma cells (A549). PLGA NSs prepared using a water-oil-water emulsion solvent evaporation method were surface-modified by adsorption of CS. The physicochemical parameters of PLGA NS, including average size and surface charge, were measured to identify which parameter influenced cellular uptake of PLGA NS. Uptake was confirmed using fluorescence spectrophotometry and was visualized in A549 cells with confocal laser scanning microscopy (CLSM). The cytotoxicities of non- and CS-PLGA NS systems were compared in vitro by MTS assay. Cellular uptake of PLGA NS increased with decreasing diameter to the submicron level and with CS-mediated surface modification. Cellular uptake of PLGA NS was energy dependent, as shown by a reduction in uptake at lower incubation temperatures and in hypertonic growth medium used as an inhibitor of clathrin-coated pit endocytosis. CS-PLGA NSs were taken up by A549 cells in an energy-dependent manner, suggesting a clathrin-mediated endocytic process. CS-PLGA NS demonstrated low cytotoxicity, similar to non-PLGA NS.

Establishing chitosan coated PLGA nanosphere platform loaded with wide variety of nucleic acid by complexation with cationic compound for gene delivery

The purpose of this paper was to establish the surface modified poly(d,l-lactide-co-glycolide) (PLGA) nanosphere platform with chitosan (CS) for gene delivery by using the emulsion solvent diffusion (ESD) method. The advantages of this method are a simple process under mild conditions without sonication. This method requires essentially dissolving both polymer and drug in the organic solvent. Therefore a hydrophilic drug such as nucleic acid is hardly applied to the ESD method. Nucleic acid can easily form an ion-complex with cationic compound, which can be dissolved in the organic solvent. Thereafter, nucleic acid solubility for organic solution can increase by complexation with cationic compound. We used DOTAP as a cationic compound to increase the loading efficiency of nucleic acid. By coating the PLGA nanospheres with CS, the loading efficiency of nucleic acid in the modified nanospheres increased significantly. The release profile of nucleic acid from PLGA nanospheres exhibited sustained release after initial burst. The PLGA nanospheres coated with chitosan reduced the initial burst of nucleic acid release and prolonged the drugs releasing at later stage. Chitosan coated PLGA nanosphere platform was established to encapsulate satisfactorily wide variety of nucleic acid for an acceptable gene delivery system.

Oral nuclear factor-κB decoy oligonucleotides delivery system with chitosan modified poly(D,L-lactide-co-glycolide) nanospheres for inflammatory bowel disease.

Chitosan (CS)-modified poly(D,L-lactide-co-glycolide) (PLGA) nanospheres (NS) were developed and evaluated for use with a nuclear factor kappa B (NF-κB) decoy oligonucleotide (ODN) oral delivery system in an experimental model of ulcerative colitis (UC). Decoy ODN-loaded PLGA NS were prepared by an emulsion solvent diffusion method, and the physicochemical properties of NS were investigated. CS-modified PLGA NS (CS-PLGA NS) showed positive zeta potential, while unmodified PLGA NS (plain-PLGA NS) were negatively charged. Decoy ODN uptake studies with Caco-2 cells using confocal laser scanning microscopy (CLSM) indicated that CS-PLGA NS were more effectively taken up by the cells than plain-PLGA NS. Decoy ODN-loaded CS-PLGA NS were able to improve the stability of ODN against DNase I or an acidic medium, such as gastric juice. Daily oral administration of CS-PLGA NS in a rat model significantly improved dextran sulfate sodium-induced diarrhea, bloody feces, shortening of colon length, and myeloperoxidase activity. Furthermore, decoy ODN-loaded CS-PLGA NS were specifically deposited and adsorbed on the inflamed mucosal tissue of the UC model rat. These results suggested that CS-PLGA NS provide an effective means of colon-specific oral decoy ODN delivery in UC.

Chitosan-modified poly(d,l-lactide-co-glycolide) nanospheres for improving siRNA delivery and gene-silencing effects

Abstract Chitosan (CS) surface-modified poly(d,l-lactide-co-glycolide) (PLGA) nanospheres (NS) for a siRNA delivery system were evaluated in vitro. siRNA-loaded PLGA NS were prepared by an emulsion solvent diffusion (ESD) method, and the physicochemical properties of NS were investigated. The level of targeted protein expression and siRNA uptake were examined in A549 cells. CS-modified PLGA NS exhibited much higher encapsulation efficiency than unmodified PLGA NS (plain-PLGA NS). CS-modified PLGA NS showed a positive zeta potential, while plain-PLGA NS were negatively charged. siRNA uptake studies by observation with confocal leaser scanning microscopy (CLSM) indicated that siRNA-loaded CS-modified PLGA NS were more effectively taken up by the cells than plain-PLGA NS. The efficiencies of different siRNA preparations were compared at the level of targeted protein expression. The gene-silencing efficiency of CS-modified PLGA NS was higher and more prolonged than those of plain-PLGA NS and naked siRNA. This result correlated with the CLSM studies, which may have been due to higher cellular uptake of CS-modified PLGA NS due to electrostatic interactions. It was concluded that CS-modified PLGA NS containing siRNA could provide an effective siRNA delivery system.

A novel method for measuring rigidity of submicron-size liposomes with atomic force microscopy.

There are many useful colloidal drug delivery systems that use liposomes. The rigidity of the carrier particle is one of the most important properties affecting drug delivery effectiveness, assessed by particle stability, release profile of encapsulated drug, and blood circulation time. However, it is difficult to evaluate the rigidity of such fine particles; so far, no useful methods have been reported. We demonstrate a unique method to evaluate the rigidity of liposomes using atomic force microscopy (AFM) and dynamic light scattering (DLS) in this report. We showed that the combination of two types of particle-size measurements, tapping mode AFM in buffer solution with another conventional method such as DLS, is useful for evaluating the rigidity of submicron-size particles such as liposomes.

Engineering of poly(DL-lactic-co-glycolic acid) nanocomposite particles for dry powder inhalation dosage forms of insulin with the spray-fluidized bed granulating system

The objective of the present research is to develop a new particulate preparation process for dry powder inhalation by which peptide-loaded poly(DL-lactic-co-glycolic acid) nanospheres are granulated with sugar alcohol (mannitol, around 4 μm in diameter). A spray-drying fluidized bed granulator was used to form soft matrix composite granules. A nanosphere suspension can be readily obtained by dispersing the composite granules in distilled water. The composite granules showed inhalation performance superior to that of freeze-dried nanosphere powder. More than 50% of composite granules were delivered to the bronchioles and alveoli of a rat. The composite granules of insulin-loaded nanosphere have a strong and prolonged pharmacological effect compared to the inhalation of insulin solution.

Brain targeting with surface-modified poly(D,L-lactic-co-glycolic acid) nanoparticles delivered via carotid artery administration.

In this study, we investigated surface-modified nanoparticles (NP) formulated using a biodegradable polymer, poly(D,L-lactide-co-glycolide) (PLGA), for targeting central nervous system (CNS) diseases. Polysorbate 80 (P80), poloxamer 188 (P188), and chitosan (CS) were used to modify the surfaces of PLGA NP to improve the brain delivery of NP. Surface-modified PLGA NP were formulated using an emulsion solvent diffusion method. 6-Coumarin was used as a fluorescent label for NP. The different formulations of 6-coumarin-loaded PLGA NP were injected into rats via carotid arteries. NP remaining in the brain were evaluated quantitatively, and brain slices were observed using confocal laser scanning microscopy (CLSM). Carotid artery administration was more effective for delivering NP into the brain compared to intravenous administration. After administration, NP concentrations in the brain were increased by NP surface modification, especially CS- and P80-PLGA NP. CLSM observations indicated that P80-PLGA NP could cross the blood-brain barrier and thus serve as a drug delivery system for the CNS. These results indicate that surface-modified PLGA NP have a high potential for use in CNS delivery systems.

Insulin-S.O (sodium oleate) complex-loaded PLGA nanoparticles: Formulation, characterization and in vivo evaluation

S.O (sodium oleate) is an anionic surfactant, which is able to forman ionic complex with positively charged insulin at suitable pH. In a previous study, the insulin-S.O (Ins-S.O) complex was prepared by a hydrophobic ion pairing (HIP) method to improve the apparent liposolubility of insulin. The formation of the complex was further confirmed by Zeta potential and X-ray method. Based on the preliminary study, poly(lactide-co-glycolide) (PLGA) nanoparticles harbouring Ins-S.O complex was prepared via an emulsion solvent diffusion method. The effects of key parameters such as concentration of PVA, concentration of PLGA and initial-loaded drug on the properties of the nanoparticles were investigated. The insulin encapsulation efficiency (EE(%)) reached up to 91.2% and mean diameter of the nanoparticles was sized ∼160 nm under optimal conditions. The pharmacological effects of the nanoparticles made of PLGA (75/25, Av Mw 15 000) were further evaluated to confirm their potential suitability for oral delivery. In order to evaluate hyperglycaemic effect of the nanoparticles for oral administration, Ins-S.O complex-loaded PLGA nanoparticles (20 IU/Kg) were administered orally by force-feeding to diabetic rats. In the case of the nanoparticles, the plasma glucose level reduced to 23.85% from the initial one 12 h post-administration and this continued for 24 h. The results showed that the use of Ins-S.O complex-loaded PLGA nanoparticles is an effective method of reducing plasma glucose levels. The insulin nanoparticles also improved the glycaemic response to an oral glucose challenge.

Cellular uptake mechanisms and intracellular distributions of polysorbate 80-modified poly (d,l-lactide-co-glycolide) nanospheres for gene delivery

We previously developed chitosan (CS)-modified poly (D,L-lactide-co-glycolide) (PLGA) nanospheres (NS) by an emulsion solvent diffusion method as a gene delivery system. In this study, PLGA NS were modified using polysorbate 80 (P80) to improve their cellular uptake. We investigated the cellular uptake, intracellular distribution, and transfection efficiency of P80-modified PLGA NS (P80-PLGA NS) for a plasmid DNA delivery system in A549 cells. The cellular uptake and transfection efficiency of P80-PLGA NS were greater than CS-modified PLGA NS (CS-PLGA NS). The uptake of unmodified NS and CS-PLGA NS was mediated, predominantly, by clathrin-mediated endocytosis. In contrast, a specific endocytic pathway could not be determined for the cellular uptake of P80-PLGA NS. The intracellular distributions of PLGA NS depended on their surface properties. P80-PLGA NS were not cytotoxic for A549 cells. Thus, P80-PLGA NS could be used as an effective gene delivery system; the surface properties of PLGA NS are key parameters for optimal intracellular uptake and distribution.

Effectiveness of submicronized chitosan-coated liposomes in oral absorption of indomethacin

The plasma profile of indomethacin (IMC) after oral administration of IMC-loaded submicronized chitosan-coated liposomes (ssCS-Lip) was evaluated to reveal the effectiveness of the mucoadhesive function for improving the absorption of this poorly absorbable drug. The stomach and small intestine were removed from rats after 1, 2, and 4 hours of oral administration of submicron-sized liposomes (ssLip) or ssCS-Lip containing fluorescent dye, and the retentive properties were confirmed by measuring the amount of dye in each part of the gastrointestinal (GI) tract. Results showed that ssCS-Lip tended to be better retained in the upper part of the GI tract, compared with ssLip, at 1, 2, and 4 hours after administration, and was significantly better retained in the small intestine at 4 hours. The plasma profile and bioavailability of IMC after oral administration of both types of liposomes were improved, compared with oral administration of IMC solution. The maximum residence time of ssCS-Lip was significantly longer than those of ssLip. The extended plasma profile of ssCS-Lip was attributed to its prolonged retention in the upper region of the GI tract, and its delayed migration to the lower part of the intestine, the neutral pH of which is more soluble for IMC, an acidic drug. Therefore, the chitosan-coated ssLip, with its higher retention in the GI tract, is a promising drug carrier for the oral administration of poorly absorbed compounds.