Encapsulation Efficiency Of Microparticles Research Articles

Engineering porous PLGA microparticles for pulmonary delivery of sildenafil citrate

Orally administered Sildenafil (SDF) is used to treat pulmonary arterial hypertension. However, it has a relatively low bioavailability of approximately 40%. To circumvent such limitations, pulmonary administration emerges as a promising alternative. This study aimed to develop SDF-loaded porous poly (lactic-co-glycolic acid) microparticles for pulmonary administration. Microparticles were obtained by double emulsion with solvent evaporation, using polyethyleneimine (PEI) as a surfactant and ammonium bicarbonate (ABC) as a porogenic agent. The encapsulation efficiency of microparticles was improved up to ≅86% by using PEI at 1% concentration. Aerodynamic diameter, and tappet density of the optimized formulation (0.5% ABC and 1% PEI) were 4.74 ± 0.09 μm, 0.100 ± 0.002 g.cm−3 respectively. The formulations presented a sustained release for up to 72 h in simulated lung fluid. In the human lung adenocarcinoma A549 cell line, porous Microparticles were non-cytotoxic at a concentration of 384 μg.mL−1 at 72 h of incubation.

Fabrication of curcumin encapsulated in casein-ethyl cellulose complexes and its antibacterial activity when applied in combination with blue LED irradiation

Casein and ethyl cellulose (Cas + EC) complexes were fabricated and used for encapsulation of curcumin (Cur). Physicochemical properties of Cas + EC/Cur along with its antibacterial activity when used in combination with blue LED irradiation were investigated. Encapsulation efficiency of microparticles at Cas:EC of 1:1 was the highest at 92.4%, with average particle size of 1.47 μm and ζ-potential of −21.40 mV. Fourier transform infrared spectroscopy revealed that Cur was well encapsulated in Cas + EC by electrostatic interactions; more hydrogen bonds were also formed. At optimal encapsulation condition, Cur exhibited good thermal stability; its water solubility improved 69 folds, while its release rate in oily food mimic reached 76%. Cas + EC/Cur in combination with blue LED irradiation could rapidly inactivate Escherichia coli ATCC 43894, Staphylococcus aureus ATCC 23235 and Pseudomonas aeruginosa MCC-208. Such desirable activities are attributed to the production of reactive oxygen species, which caused increased membrane permeability and reduced bacterial cell integrity.

Optimization of Process Parameters of Osthole-Loaded PLGA Microparticles Prepared Using Emulsification–Solvent Extraction

Osthole-loaded poly(d,l-lactic-co-glycolic) acid (PLGA) microparticles were prepared by oil-in-water (o/w) emulsification. The organic phase in emulsions was extracted by conventional evaporation and supercritical fluid extraction of emulsions. A Box–Behnken experimental design was used to evaluate the effects and to optimize the variables. Results indicated that the effects from two variables, that is, the emulsification stirring speed and the ratio of osthole to PLGA, had statistically significant on the encapsulation efficiency, while another variable, that is, the volume ratio of o/w, has no independent impact on the encapsulation. The interactions exist between the ratio of osthole to PLGA and the stirring speed, and between the volume ratio of o/w and the stirring speed. A second-order polynomial model was well adjusted to predict response variables, and 90.9% encapsulation efficiency could be realized at optimized conditions. The encapsulation efficiency of microparticles obtained with conventional evaporation was higher than that with supercritical fluid extraction of emulsions. The release curve of osthole from the microparticles could be nicely fitted by the Weibull equation and the release follows Fickian diffusion.

Comparison of a novel spray congealing procedure with emulsion-based methods for the micro-encapsulation of water-soluble drugs in low melting point triglycerides

The particle size characteristics and encapsulation efficiency of microparticles prepared using triglyceride materials and loaded with two model water-soluble drugs were evaluated. Two emulsification procedures based on o/w and w/o/w methodologies were compared to a novel spray congealing procedure. After extensive modification of both emulsification methods, encapsulation efficiencies of 13.04% tetracycline HCl and 11.27% lidocaine HCl were achievable in a Witepsol®-based microparticle. This compares to much improved encapsulation efficiencies close to 100% for the spray congealing method, which was shown to produce spherical particles of ∼58 μm. Drug release studies from a Witepsol® formulation loaded with lidocaine HCl showed a temperature-dependent release mechanism, which displayed diffusion-controlled kinetics at temperatures ∼25°C, but exhibited almost immediate release when triggered using temperatures close to that of skin. Therefore, such a system may find application in topical semi-solid formulations, where a temperature-induced burst release is preferred.

Effect of poly(lactide-co-glycolide) molecular weight on the release of dexamethasone sodium phosphate from microparticles

The objective of this study was to investigate the effect of poly(lactide-co-glycolide) (PLGA) molecular weight (Resomer® RG 502H, RG 503H, and RG 504H) on the release behavior of dexamethasone sodium phosphate-loaded microparticles. The microparticles were prepared by three modifications of the solvent evaporation method (O/W-cosolvent, O/W-dispersion, and W/O/W-methods). The encapsulation efficiency of microparticles prepared by the cosolvent- and W/O/W-methods increased from ∼50% to >90% upon addition of NaCl to the external aqueous phase, while the dispersion method resulted in lower encapsulation efficiencies. The release of dexamethasone sodium phosphate from PLGA microparticles (>50 µm) was biphasic. The initial burst release correlated well with the porosity of the microparticles, both of which increased with increasing polymer molecular weight (RG 504H > 503H > 502H). The burst was also dependent on the method of preparation and was in the order of dispersion method > WOW method > consolvent method. In contrast to the higher molecular weight PLGA microparticles, the release from RG 502H microparticles prepared by cosolvent method was not affected by volume of organic solvent (1.5–3.0 ml) and drug loading (4–13%). An initial burst of ∼10% followed by a 5-week sustained release phase was obtained. Microparticles with a size <50 µm released in a triphasic manner; an initial burst was followed by a slow release phase and then by a second burst.