Fuminori Ito

Effect of polyethylene glycol on preparation of rifampicin-loaded PLGA microspheres with membrane emulsification technique

Monodisperse poly(lactide-co-glycolide) (PLGA) microspheres containing rifampicin (RFP), anti-tubercle drug, as hydrophobic model drug were prepared by solvent evaporation method with a membrane emulsification technique using Shirasu Porous Glass (SPG) membranes. Five kinds of rifampicin-loaded PLGA (RFP/PLGA) microspheres with different sizes were prepared by changing pore size of the membranes. Effect of polyethylene glycol (PEG) added to polyvinyl alcohol (PVA) solution (continuous phase) upon the monodispersity of microspheres was studied. PEG was used as a stabilizer for microspheres dispersing in PVA solution. The most suitable molecular weight of PEG as a stabilizer was 20,000. RFP/PLGA microspheres prepared with PEG20000 were apparently more uniform than those prepared without PEG. The yield of RFP/PLGA microspheres was 100%. The initial burst observed in the release of RFP from RFP/PLGA microspheres was suppressed by the addition of PEG.

Preparation and properties of PLGA microspheres containing hydrophilic drugs by the SPG (shirasu porous glass) membrane emulsification technique

In the present paper, monodisperse poly (lactide-co-glycolide) (PLGA) microspheres containing the hydrophilic model drug, blue dextran (BLD), were manufactured by the solvent evaporation method and the shirasu porous glass (SPG) membrane emulsification technique. In order to prepare PLGA microspheres with a higher drug loading efficiency by the membrane emulsification technique, the test of stability and productivity of the primary emulsion (w(1)/o emulsion) was preliminary examined by change species or concentration of the oil-soluble surfactant and the ratio of water and organic solvent. The primary emulsion (w(1)/o) composed of the BLD aqueous solution and dichloromethane (DCM) dissolved PLGA was prepared with the micro homogenizer. The secondary emulsion (w(1)/o/w(2)) was prepared by the SPG membrane emulsification technique. BLD/PLGA microspheres of various micro level sizes of 2.0-10 microm prepared by variation of pore size of the using SPG membrane. The highly monodisperse BLD/PLGA microspheres were also manufactured by added polyethylene glycol (PEG) into the water phase, as reported in a previous paper. The initial release rate of the drug from such microspheres controlled than the sample manufactured without an additive.

Control of drug loading efficiency and drug release behavior in preparation of hydrophilic-drug-containing monodisperse PLGA microspheres

We prepared monodisperse poly(lactide-co-glycolide) (PLGA) microspheres containing blue dextran (BLD)—a hydrophilic drug—by membrane emulsification technique. The effects of electrolyte addition to the w2 phase and significance of the droplet size ratio between primary (w1/o) and secondary (w1/o/w2) emulsions during the preparation of these microspheres was examined. The droplet size ratio was evaluated from the effect of stirring rate of the homogenizer when preparing the primary emulsion. The drug loading efficiency of BLD in these microspheres increased with stirring rate. It increased to approximately 90% when 2.0% NaCl was added to the w2 phase. Drug release from these microspheres was slower than that when they were prepared without electrolyte addition. Despite the very high efficiency drug release was gradual because BLD was distributed at the microspheres core. Relatively monodisperse hydrophilic-drug-containing PLGA microspheres with controlled drug loading efficiency and drug release behavior were prepared.

Preparation of Biodegradable Polymer Nanospheres Containing Manganese Porphyrin (Mn-Porphyrin)

Herein, poly(lactide-co-glycolide) (PLGA) nanospheres containing Mn-porphyrin, which exhibit chemically versatile and promising superoxide dismutase mimic, were prepared for biomaterial and drug-delivery-system formulations. The particle sizes and Mn-porphyrin-loading efficiencies of the nanospheres were controlled in order to realize breakthrough therapies for the incurable diseases. The sizes of the prepared Mn-porphyrin/PLGA nanospheres increased with the amount of PLGA used during preparation. Furthermore, the w1-to-o-phase volume ratio affected the loading efficiency of the Mn-porphyrin into the nanospheres. Nanospheres prepared from PLGA of lower molecular weight exhibited higher Mn-porphyrin-loading efficiencies. Furthermore, nanospheres prepared from PLGA with a molecular weight of 5000 exhibited a loading efficiency of 60%, which is higher than those generally reported for other nanospheres (~ 10%). Release testing revealed that the molecular weight of the PLGA influenced the release behaviour of the Mn-porphyrin from the nanospheres. Hence, Mn-porphyrin/PLGA nanospheres with controllable particle sizes, loading efficiencies, and release behaviour were prepared.