In vivo and in vitro characteristics for insulin-loaded PLA microparticles prepared by w/o/w solvent evaporation method with electrolytes in the continuous phase

Insulin-loaded poly(lactide) (PLA) microparticles were successfully prepared by 6% w/v PLA in the organic phase, 10% w/v PVP and varied types of 5%w/v electrolytes in the continuous phase, by using a water-in-oil-in-water emulsion/ solvent extraction technique. Addition of electrolytes such as NaCl, CaCl2 into the external phase significantly improved insulin entrapment efficiency compared to the case of no additives. NaCl was the most effective for obtaining high entrapment efficiency, with microparticle yield 81.2%, trapping efficiencies 49%, insulin-loading level 5.5% w/w and mean particle size 14.8 microm. The distribution (%) of insulin on the PLA microparticles surface, outer layer and core were 8, 37 and 43%, respectively. The cumulative release of insulin had an upper limit of approximately 24% of the insulin load at 24 days. A steady release rate was 0.5 microg insulin/mg microparticles/day of insulin release maintained for 24 days. Total protein-leaking amount was reduced after addition of electrolytes in the continuous aqueous phase. Rabbit glucose levels were evaluated after subcutaneous 20 mg insulin-loaded PLA microparticles or PLA blank microparticles. Study results show that the insulin-loaded PLA microparticles significantly reduced the glucose level than PLA blank microparticles. The insulin-loaded PLA microparticles, physicochemical characterization data and the animal result obtained in this study may be relevant in optimizing the PLA microparticle formulation incorporation and delivery insulin carriers.     

The mechanism of PLA microparticle formation by waterin-oil-in-water solvent evaporation method

Microparticles containing ovalbumin as a model protein drug were prepared using poly(L-lactide; PLA) with a water-in-oil-in-water emulsion/solvent evaporation technique. The dispersed phase was PLA dissolved in dichloromethane (DCM), and the continuous phase was water-containing polyvinyl pyrolidone (PVP) as stabilizer with sodium chloride. Microparticle characteristics, loading efficiencies, protein distribution in microparticles, and in-vitro release properties were investigated. The OVA leaking into the continuous phase during the formation of microparticle by DCM evaporation was also evaluated. Results show that OVA was successfully entrapped in the microparticles with trapping efficiencies up to 72%, loading level 8.7% w/v, and particle size 14 #181;m. The semi-solid suspension changes to a solid particle happened during a 10-min period. Total protein-leaking amount was reduced after addition of NaCl in the continuous aqueous phase, which resulted from reducing the solidification time and protein-leaking rate. Using 5% w/v NaCl in the continuous phase resulted in higher loading content (87.2 1.0 #181;g/mg), and loading efficiency (72.2%), which resulted from more protein in the deeper layer (50.2 2.3 #181;g/mg) and higher microparticle yield (75.2%) than without NaCl (loading content: 74.0 1.0 #181;g/mg; loading efficiency 51.8%; deeper layer content: 18.3 3.5 #181;g/mg; yield: 63.6%). These results constitute a step forward in the improvement of existing technology in controlling protein encapsulation and delivery from microparticles prepared by the multiple emulsion solvent evaporation method.     

Patent Briefing

Japanese encephalitis virus (JEV)-loaded poly(lactide) (PLA) lamellar and poly(DL-lactide-co-glycolide) (PLG) microparticles were successfully prepared with low molecular weight PLA by the precipitate method and with 6% w/v PLG in the organic phase, 10% w/v PVP and 5% w/v NaCl in the continuous phase, by using a water-in-oil-in-water emulsion/solvent extraction technique, respectively. JEV was entrapped in the PLG microparticles by a solvent extraction technique with trapping efficiencies up to 98%, loading level 5.5% w/w, and mean particle size 3.8 #181;m. The distribution (%) of JEV on the PLG microparticles surface, outer layer, and core were 11.2, 41.7 and 46.4%, respectively. The cumulative release of JEV had an upper limit of ~ 58% of the JEV load at 24 days. The steady release rate was 1.33 #181;g JEV/mg microparticles/day of JEV release maintained for 24 days. The corresponding virus loading of the PLA lamellae is ~ 0.78% w/w and the loading efficiency (77.8%), JEV content (7.84 #181;g/mg), and yield (96.3%), respectively. The distribution (%) of JEV on the microparticles surface, outer layer, and core were 82.1, 13.3 and 2.2%, respectively. The live JEV challenge in mice test, in which mice received one dose of 20 mg JEV-loaded PLG microparticles, 20 mg JEV-loaded PLA lamellar in comparison with JEV or PBS solution, was evaluated after IP immunization of BALB/c mice. The study results show that the greatest survival was observed in the group of mice immunized with 20 mg JEV-loaded PLG microparticles and 20 mg JEV-loaded PLA microparticles group (80%). The JEV incorporation, physicochemical characterization data, and the animal results obtained in this study may be relevant in optimizing the vaccine incorporation and delivery properties of these potential vaccine targeting carriers.     

The stability of insulin in biodegradable microparticles based on blends of lactide polymers and polyethylene glycol

Insulin-loaded microparticles were produced from blends of poly(ethylene glycol) (PEG) with poly (L-lactide) (PLA) homopolymer and poly (DL-lactide co-glycolide) copolymers (PLG) using a water-in-oil solvent extraction method. The dispersed phase was composed of PLG/PEG or PLA/PEG dissolved in dichloromethane, and the continuous phase was methanol containing 10% PVP. Characteristics, including particle size distribution, insulin loading capacity and efficiencies, in vitro release, degradation and stability, were investigated. The stability of insulin associated with microparticles prepared using PEG and 50:50 PLG and PLA was analysed by HPSEC and quantified by peak area following incubation in PBS at 37 degrees C for up to 1 month. Insulin was successfully entrapped in the PLG/PEG and PLA/PEG microparticles with trapping efficiencies up to 56 and 48%, loading levels 17.8 and 10.6% w/w, and particle sizes 8 and 3 microm, respectively. The insulin-loaded PLG/PEG and PLA/PEG microparticles were capable of controlling the release of insulin over 28 days with in vitro delivery rates of 0.94 and 0.65 microg insulin/mg particles/day in the first 4 days and a steady release with rate of 0.4 and 0.43 microg insulin/mg particles/day over the following 4 weeks, respectively. Extensive degradation of the PLG/PEG microparticles also occurred over 4 weeks, whereas the use of PLA/PEG blends resulted in a stable microparticle morphology and much reduced fragmentation and aggregation of the associated insulin.     

The mechanism of PLA microparticle formation by water-in-oil-in-water solvent evaporation method

Microparticles containing ovalbumin as a model protein drug were prepared using poly(L-lactide; PLA) with a water-in-oil-in-water emulsion/solvent evaporation technique. The dispersed phase was PLA dissolved in dichloromethane (DCM), and the continuous phase was water-containing polyvinyl pyrolidone (PVP) as stabilizer with sodium chloride. Microparticle characteristics, loading efficiencies, protein distribution in microparticles, and in-vitro release properties were investigated. The OVA leaking into the continuous phase during the formation of microparticle by DCM evaporation was also evaluated. Results show that OVA was successfully entrapped in the microparticles with trapping efficiencies up to 72%, loading level 8.7% w/v, and particle size 14 microm. The semi-solid suspension changes to a solid particle happened during a 10-min period. Total protein-leaking amount was reduced after addition of NaCl in the continuous aqueous phase, which resulted from reducing the solidification time and protein-leaking rate. Using 5% w/v NaCl in the continuous phase resulted in higher loading content (87.2 +/- 1.0 microg/mg), and loading efficiency (72.2%), which resulted from more protein in the deeper layer (50.2 +/- 2.3 microg/mg) and higher microparticle yield (75.2%) than without NaCl (loading content: 74.0 +/- 1.0 microg/mg; loading efficiency 51.8%; deeper layer content: 18.3 +/- 3.5 microg/mg; yield: 63.6%). These results constitute a step forward in the improvement of existing technology in controlling protein encapsulation and delivery from microparticles prepared by the multiple emulsion solvent evaporation method.     

Japanese encephalitis virus vaccine formulations using PLA lamellar and PLG microparticles

Japanese encephalitis virus (JEV)-loaded poly(lactide) (PLA) lamellar and poly(DL-lactide-co-glycolide) (PLG) microparticles were successfully prepared with low molecular weight PLA by the precipitate method and with 6% w/v PLG in the organic phase, 10% w/v PVP and 5% w/v NaCl in the continuous phase, by using a water-in-oil-in-water emulsion/solvent extraction technique, respectively. JEV was entrapped in the PLG microparticles by a solvent extraction technique with trapping efficiencies up to 98%, loading level 5.5% w/w, and mean particle size 3.8 microm. The distribution (%) of JEV on the PLG microparticles surface, outer layer, and core were 11.2, 41.7 and 46.4%, respectively. The cumulative release of JEV had an upper limit of approximately 58% of the JEV load at 24 days. The steady release rate was 1.33 microg JEV/mg microparticles/day of JEV release maintained for 24 days. The corresponding virus loading of the PLA lamellae is approximately 0.78% w/w and the loading efficiency (77.8%), JEV content (7.84 microg/mg), and yield (96.3%), respectively. The distribution (%) of JEV on the microparticles surface, outer layer, and core were 82.1, 13.3 and 2.2%, respectively. The live JEV challenge in mice test, in which mice received one dose of 20 mg JEV-loaded PLG microparticles, 20 mg JEV-loaded PLA lamellar in comparison with JEV or PBS solution, was evaluated after IP immunization of BALB/c mice. The study results show that the greatest survival was observed in the group of mice immunized with 20 mg JEV-loaded PLG microparticles and 20 mg JEV-loaded PLA microparticles group (80%). The JEV incorporation, physicochemical characterization data, and the animal results obtained in this study may be relevant in optimizing the vaccine incorporation and delivery properties of these potential vaccine targeting carriers.     

The mechanism of surface-indented protein-loaded PLGA microparticle formation: the effects of salt (NaCl) on the solidification process

The purpose of this study was to evaluate ovalbumin (OVA) leakage pathways and to explore the mechanism of the surface-indented microparticle formation in the preparation of OVA-loaded microparticles. OVA-loaded poly (D,L-lactic-co-glycolic acid) (PLGA) microparticles were prepared by a water-in oil-in water (w/o/w) solvent evaporation method associated with varied NaCl (NaCl) concentrations and adjusted with urea at 1240?mOsm?kg^?1 in the external aqueous phase. To evaluate dichloromethane (DCM)-related OVA leakage, three stirring rates, 600, 800, 1000?rpm at 25° C were carried out during the solvent evaporation stage. Both DCM and OVA levels in the external phase medium and total dispersion were sampled and measured. The time course of particle characteristics was evaluated by microscopy or SEM photography. The surface adsorptive capacities of the prepared microparticles were measured by using bovine serum albumin conjugated with fluorescein isothiocyanate (FITC-BSA). The findings were that the DCM-related OVA leakage accounted for ～34% of the total leakage. By combining NaCl in the external phase, a faster solidifying crust-like structure was formed as a barrier to remarkably reduce OVA loss and improve OVA content from 40.1 to 72.8?µg?mg^?1. The yield and OVA content for formulations containing NaCl were much improved by the ionic effect, in addition to the osmotic effect. The total entrapment efficiency was also highly increased from 43 to 72%. The formations of the crust-like surface structure of the microparticle were affected by entrapped drugs, salt content in the external phase and aqueous volume in the inner phase. A scheme was proposed to interpret the formation mechanism of the surface-indented microparticles. In comparison to the surface-smooth microparticles, the surface adsorptive capacities of the surface-indented microparticles were highly improved from 26.6 to 87.0%, determined by the adsorption of FITC-BSA.     

Melatonin releasing PLGA micro/nanoparticles and their effect on osteosarcoma cells

Melatonin loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles and microparticles in the diameter of ～200?nm and 3.5?μm, respectively, were prepared by emulsion–diffusion–evaporation method. Melatonin entrapment into the particles was significantly improved with the addition of 0.2% (w/v) melatonin into the aqueous phase and encapsulation efficiencies were found as 14 and 27% for nanoparticles and microparticles, respectively. At the end of 40 days, ～70% of melatonin was released from both of particles, with high burst release. Both blank and melatonin loaded PLGA nanoparticles caused toxic effect on the MG-63 cells due to their uptake by the cells. However, when 0.05?mg microparticle that is carrying ～1.7?μg melatonin was added to the cm² of culture, inhibitory effect of melatonin on the cells were obviously observed. The results would provide an expectation about the usage of melatonin as an adjunct to the routine chemotherapy of osteosarcoma by encapsulating it into a polymeric carrier system.     

Development and in vitro/in vivo evaluation of Zn-pectinate microparticles reinforced with chitosan for the colonic delivery of progesterone

The colon is a promising target for drug delivery owing to its long transit time of up to 78?h, which is likely to increase the time available for drug absorption. Progesterone has a short elimination half-life and undergoes extensive first-pass metabolism, which results in very low oral bioavailability (～25%). To overcome these shortcomings, we developed an oral multiparticulate system for the colonic delivery of progesterone. Zn-pectinate/chitosan microparticles were prepared by ionotropic gelation and characterized for their size, shape, weight, drug entrapment efficiency, mucoadhesion and swelling behavior. The effect of cross-linking pH, cross-linking time and chitosan concentration on progesterone release were also studied. Spherical microparticles having a diameter of 580–720?µm were obtained. Drug entrapment efficiency of ～75–100% was obtained depending on the microparticle composition. Microparticle mucoadhesive properties were dependent on the pectin concentration, as well as the cross-linking pH. Progesterone release in simulated gastric fluids was minimal (3–9%), followed by burst release at pH 6.8 and a sustained phase at pH 7.4. The in vivo study revealed that the microparticles significantly increased progesterone residence time in the plasma and increased its relative bioavailability to ～168%, compared to the drug alone. This study confirms the potential of Zn-pectinate/chitosan microparticles as a colon-specific drug delivery system able to enhance the oral bioavailability of progesterone or similar drugs.     

Vibrio cholerae -loaded poly(DL lactide co-glycolide) microparticles

Vibrio cholerae (VC)-loaded microparticles were prepared using poly(DL lactide-co-glycolide) with a water-in-oil-in-water emulsion/solvent extraction technique. Particle characteristics including size distribution, VC-loading efficiencies, and in-vitro release pattern were investigated. The dispersed phase was PLG dissolved in dichloromethane, and the continuous phase was water containing PVP as a stabilizer with varied sodium chloride concentrations. VC was successfully entrapped in the microparticles with trapping efficiencies up to 97.8%, a loading level of 55.4 g/mg, and particle size of 3.8 #181;m. Using 10% w/v PVP with 5% w/v NaCl in the continuous phase resulted in a higher loading level (55.4 #45 6.9 g/mg), loading efficiency (97.8%), core region content (25.7 #45 1.9 g/mg) and lower surface content (6.2 #45 0.9 g/mg) than without NaCl (loading content: 40.7 #45 5.1 g/mg; loading efficiency 52.1%; core region content: 8.3 #45 0.5 g/mg; surface content: 19.5 #45 1.1 g/mg). A linear release profile from VC-loaded microparticles was found. A preliminary animal oral administration study indicated that the VC-loaded microparticles, as an oral delivery system, have shown effective immunogencity in rats for 2 months. The VC incorporation and physicochemical characterization data obtained in this study may be relevant in optimising the vaccine incorporation and delivery properties of these potential vaccine targeting carriers.     

Improved bioavailability of orally delivered insulin using Eudragit-L30D coated PLGA microparticles

Large porous microparticles of PLGA entrapping insulin were prepared by solvent evaporation method and evaluated in diabetes induced rat for its efficacy in maintaining blood sugar level from a single oral dose. Incorporation of Eudragit L30D (0.03% w/v) in the external aqueous phase resulted in formation of pH responsive enteric coated polymer particles which release most of the entrapped insulin in alkaline pH. At acidic pH, release of insulin from uncoated PLGA microparticles and Eudragit L30D coated PLGA microparticles was 31.62?±?1.8% and 17.5?±?1.29%, respectively, for initial 30 min. However, in 24 h, in vitro released insulin from uncoated PLGA and Eudragit coated particles was 96.29?±?1.01% and 88.30?±?1%, respectively. Released insulin from composite polymer particles were mostly in monomer form without aggregation and was stable for a month at 37°C. Oral administration of insulin loaded PLGA (50 : 50) and Eudragit L30D coated PLGA (50 : 50) microparticles (equivalent to 25 IU insulin/kg of animal weight) in alloxan induced diabetic rats resulted in 37.3?±?11% and 62.7?±?3.8% reduction in blood glucose level, respectively, in 2 h. This effect continued up to 24 h in the case of Eudragit L30D coated PLGA microparticles. Results demonstrate that use of stabilizers during PLGA particle formulation, large porous particle for quick release of insulin and coating with Eudragit L30D resulted in a novel oral formulation for once a day delivery of insulin.     

A novel approach to prepare insulin-loaded poly(lactic-co-glycolic acid) microcapsules and the protein stability study

The purpose of this study was to propose a new preparation method to fabricate insulin-loaded poly(lactic-coglycolic acid) (PLGA) microparticles satisfying protein loading, release profiles, burst release, and particularly stability of the encapsulated protein. Insulin-loaded microcapsules were produced by a single phase o/o solvent evaporation method. The characteristics of the microcapsules were determined by various methods: the surface morphology and size of microparticles by atomic force microscopy and scanning electron microscopy, insulin crystalinity and drug-polymer interactions by XRD, DSC, and FTIR, chemical integrity and aggregation of insulin using HPLC and SDS-PAGE, the protein secondary structure by far ultraviolet-circular dichroism (CD), the antigenicity activity of insulin with ELISA techniques. PLGA microparticles showed smooth surfaces with microcapsule. Encapsulation efficiency of 51% and constant insulin release rate with initial insulin burst release of 24% was obtained. Encapsulated and released insulin was in the intact form and it was dispersed in crystalline state in the polymer matrix. Ease of manufacturing under mild preparation conditions, high level of drug entrapment, desirable release pattern with relatively low initial burst effect and an ability to preserve protein structure are the advantages which are offered by the developed protein encapsulation method.     

Ciclosporin-loaded poly(lactide) microparticles: Effect of TPGS

Abstract

The properties of spray dried PLA microparticles were affected by the choice of solvents, amount of ciclosporin and TPGS added. Ethyl acetate formed microparticle with smooth surface when compared to those produced by dichloromethane. The results of FTIR have not shown chemical interaction amongst PLA, ciclosporin and TPGS while thermal analysis showed physical interactions amongst these components. TPGS was found to lower Tg value of PLA by exerting a plasticizing effect while ciclosporin reverted this effect. When the content of TPGS increased from 2% (w/w) to 10% (w/w), the microparticles tended to agglomerate due to the lowering of the polymer Tg values at the employed spray drying temperature. In addition, a lesser amount of ciclosporin was found at the surface of the microparticle and resulted in smaller initial release of ciclosporin. When 2% (w/w) TPGS was used, the initial release of ciclosporin was enhanced and the microparticles formed were not agglomerated.     

Ciclosporin-loaded poly(lactide) microparticles: effect of TPGS

The properties of spray dried PLA microparticles were affected by the choice of solvents, amount of ciclosporin and TPGS added. Ethyl acetate formed microparticle with smooth surface when compared to those produced by dichloromethane. The results of FTIR have not shown chemical interaction amongst PLA, ciclosporin and TPGS while thermal analysis showed physical interactions amongst these components. TPGS was found to lower Tg value of PLA by exerting a plasticizing effect while ciclosporin reverted this effect. When the content of TPGS increased from 2% (w/w) to 10% (w/w), the microparticles tended to agglomerate due to the lowering of the polymer Tg values at the employed spray drying temperature. In addition, a lesser amount of ciclosporin was found at the surface of the microparticle and resulted in smaller initial release of ciclosporin. When 2% (w/w) TPGS was used, the initial release of ciclosporin was enhanced and the microparticles formed were not agglomerated.     

Preparation and characterization of hCG-loaded polylactide or poly(lactide-co-glycolide) microspheres using a modified water-in-oil-in-water (w/o/w) emulsion solvent evaporation technique

A modified w/o/w emulsion solvent evaporation technique was adopted to prepare human Chorionic Gonadotropin (hCG)-loaded polylactide (PLA) or poly(lactide-co-glycolide) (PLGA) microspheres. The effects of preparative parameters, such as stirring rate, polymer MW and concentration, and the composition of both the inner aqueous phase and oil phase etc., on hCG entrapment efficiency and microsphere characteristics were investigated. It was found that by adding 20% glycerol into the inner aqueous phase and 40% acetone into the oil phase, smooth microspheres 1mum in diameter could be produced with high hCG entrapment efficiency (>90%). In vitro release test showed a burst release of hCG from PLGA (75:25) microspheres, followed by sustained release of 55% hCG over 2 months. The initial hCG burst from PLGA microspheres increased with the glycerol concentration in the inner aqueous phase, but decreased to a low value (ca. 20%) with the addition of acetone into the oil phase, which could beattributed to the associated changes in surface morphology of the microspheres. In vivo experiments demonstrated that a single shot of hCG-loaded PLGA microspheres could produce a comparable antibody response with the inoculation of free hCG four times.     

Vibrio cholerae-loaded poly(DL lactide co-glycolide) microparticles

Vibrio cholerae (VC)-loaded microparticles were prepared using poly(DL lactide-co-glycolide) with a water-in-oil-in-water emulsion/solvent extraction technique. Particle characteristics including size distribution, VC-loading efficiencies, and in-vitro release pattern were investigated. The dispersed phase was PLG dissolved in dichloromethane, and the continuous phase was water containing PVP as a stabilizer with varied sodium chloride concentrations. VC was successfully entrapped in the microparticles with trapping efficiencies up to 97.8%, a loading level of 55.4 g/mg, and particle size of 3.8 microm. Using 10% w/v PVP with 5% w/v NaCl in the continuous phase resulted in a higher loading level (55.4 +/- 6.9 g/mg), loading efficiency (97.8%), core region content (25.7 +/- 1.9 g/mg) and lower surface content (6.2 +/- 0.9 g/mg) than without NaCl (loading content: 40.7 +/- 5.1 g/mg; loading efficiency 52.1%; core region content: 8.3 +/- 0.5 g/mg; surface content: 19.5 +/- 1.1 g/mg). A linear release profile from VC-loaded microparticles was found. A preliminary animal oral administration study indicated that the VC-loaded microparticles, as an oral delivery system, have shown effective immunogencity in rats for 2 months. The VC incorporation and physicochemical characterization data obtained in this study may be relevant in optimising the vaccine incorporation and delivery properties of these potential vaccine targeting carriers.     

Preparation and evaluation of mucinated sodium alginate microparticles for oral delivery of insulin

Effective oral insulin delivery remains a challenge to the pharmaceutical industry. In this study, insulin-loaded microparticles for oral delivery were prepared with mucin and sodium alginate combined at different ratios using a novel method based on polymer coacervation and diffusion filling. Some physical characteristics of the various insulin-loaded microparticles such as particle size, morphology and compressibility indices were determined. The microparticles were filled into hard gelatin capsules and the in vitro insulin release as well as the blood glucose reduction after oral administration to diabetic rabbits were determined. The microparticles formed were generally multi-particulate, discrete and free flowing. Before insulin loading, microparticles were round and smooth, becoming fluffier, less spherical and larger with rough and pitted surface after insulin loading. The insulin content of the microparticles increased with increase in their sodium alginate content. The various insulin-loaded microparticles prepared with the mucinated sodium alginate when encapsulated exhibited lag time before insulin release. The time taken to reach maximum insulin release from the various formulations varied with the mucin–sodium alginate ratio mix. The mean dissolution time of insulin from the microparticles prepared with sodium alginate, mucin, sodium alginate: mucin ratios of 1:1, 3:1 and 1:3 was 11.21 ± 0.75, 3.3 ± 0.42, 6.69 ± 023, 8.52 ± 0.95 and 3.48 ± 0.65 (min.), respectively. The percentage blood glucose reduction for the subcutaneously administered insulin was significantly (p < 0.001) higher than for the formulations. The blood glucose reduction effect produced by the orally administered insulin-loaded microparticles prepared with three parts of sodium alginate and one part of mucin after 5 h was, however, equal to that produced by the subcutaneously administered insulin solution, an indication that it is an effective alternative for the delivery of insulin.     

Preparation and characterization of hCG-loaded polylactide or poly(lactide-co-glycolide) microspheres using a modified water-in-oil-in-water (w/o/w) emulsion solvent evaporation technique

A modified w/o/w emulsion solvent evaporation technique was adopted to prepare human Chorionic Gonadotropin (hCG)-loaded polylactide (PLA) or poly(lactide-co-glycolide) (PLGA) microspheres. The effects of preparative parameters, such as stirring rate, polymer MW and concentration, and the composition of both the inner aqueous phase and oil phase etc., on hCG entrapment efficiency and microsphere characteristics were investigated. It was found that by adding 20% glycerol into the inner aqueous phase and 40% acetone into the oil phase, smooth microspheres approximately 1 microm in diameter could be produced with high hCG entrapment efficiency (>90%). In vitro release test showed a burst release of hCG from PLGA (75:25) microspheres, followed by sustained release of 55% hCG over 2 months. The initial hCG burst from PLGA microspheres increased with the glycerol concentration in the inner aqueous phase, but decreased to a low value (ca. 20%) with the addition of acetone into the oil phase, which could be attributed to the associated changes in surface morphology of the microspheres. In vivo experiments demonstrated that a single shot of hCG-loaded PLGA microspheres could produce a comparable antibody response with the inoculation of free hCG four times.     

Formulation and optimization of alkaline extracted ispaghula husk microparticles of isoniazid – in vitro and in vivo assessment

Microparticles containing isoniazid were prepared by the emulsification internal ionic gelation method using a novel, alkaline extracted ispaghula husk as a wall forming material. A four-factor three-level Box–Behnken design was employed to study the effect of independent variables on dependent variables. Sodium alginate concentration (X₁), alkaline extraction of ispaghula husk (AEISP) concentration (X₂), concentration of cross-linking agents (X₃) and stirring speed (X₄) were four independent variables considered in the preparation of microparticles, while the particle size (Y₁) and entrapment efficiency (Y₂) were dependent variables. Optimized microparticles exhibited 83.43% drug entrapment and 51.53?µm particle size with 97.80% and 96.37% validity, respectively, at the following conditions – sodium alginate (3.55% w/v), alkaline extracted ispaghula husk (3.60% w/v), cross-linker concentration (7.82% w/v) and stirring speed (1200?rpm). The optimized formulation showed controlled drug release for more than 12?h by following Higuchi kinetics via non-Fickian diffusion. The gamma scintigraphy of the optimized formulation in Wistar rats showed that microparticles could be observed in the intestinal lumen after 1?h and were detectable in the intestine up to 12?h, with decreased percentage of radioactivity (t_1/2 of ^99mTc 4–5?h).     

The preparation of sustained release erythropoietin microparticle

Purpose: Protein microencapsulation in biodegradable polymers is a promising route to provide for sustained release. The erythropoietin (EPO) microparticles are using human serum albumin (HSA) and poly-L-lysine (PK) as the protection complex to increased EPO integrity, entrapped efficiency and active EPO release by w/o/w solvent evaporation techniques. The optimum formulation development process was also reported by using FITC-OVA as a model protein.

Methods: The model protein FITC-ovalbumin and EPO are protected by human serum albumin and poly-L-lysine complex and encapsulated in 50:50 poly(DL-lactide-co-glycolide) by a w/o/w solvent evaporation method. Protein active integrity and degradation compound is measured by size-exclusion chromatography. Protein-loaded microparticle physical properties and in vitro active and degradation compounds release profile are characterized.

Results: High active integrity protein loading efficiency and particle yield of EPO or OVA-HSA/PK-loaded PLG microparticles are successfully produced by a w/o/w solvent evaporation method. Varied protection protein complex formulations and encapsulation processes are investigated. The high OVA model protein loading efficiency (80.2%), FITC-OVA content (0.24?µg?mg^?1) and yield (72.4%) are obtained by adding 100?µg?mL^?1 FITC-OVA complex with 10% HSA/0.05% PK (Mw 1.5–3?kD) in the initial solution to protect the model protein. In vitro release profiles show more active OVA release from HSA/PK OVA-loaded than OVA-loaded only microparticles and also the amount of degraded protein that comes out after 3 weeks incubated in the PBS medium for OVA-loaded only microparticles is observed. The same formulation and preparation process resulted in EPO loading efficiency (68.4%), EPO content (0.23?µg?mg^?1) and yield (76.1%) for HSA/PK EPO-loaded microparticles. In vitro release profiles show active EPO sustained release over 7 days. Using HSA/PK as carried in the primary emulsion of EPO-loaded microparticles resulted in less burst release% than EPO-loaded only microparticles.