Preparation and Characterization of Polylactic Acid Microspheres Containing Bovine Insulin by a w/o/w Emulsion Solvent Evaporation Method.

Uchida, Takahiro; Nagareya, Noriko; Sakakibara, Sadako; Konishi, Yuriko; Nakai, Aki; Nishikata, Mayumi; Matsuyama, Kenji; Yoshida, Kazushi

doi:10.1248/cpb.45.1539

Cited by 41 publications

(27 citation statements)

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“…The flow of water from the internal aqueous phase (w 1 ) into the continuous phase (w 2 ) seemed to exert an insignificant effect on the initial release since the BSA, a model drug in this study, was unable to cross the "semi-permeable" polymer phase due to its size. On the other hand, in a different study on insulin-loaded PLA microparticles, the osmotic pressure gradient induced by the addition of NaCl led to diffusion of the w 1 phase into the w 2 phase, compromising the encapsulation efficiency (Uchida et al, 1997). Going back to our discussion on the initial burst, the difference between NaCl and sucrose in their capabilities of reducing the initial burst seems due to their different contributions to the continuous phase (Jiang et al, 2002).…”

Section: Composition Of Continuous Phasementioning

confidence: 89%

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

2004

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Initial burst is one of the major challenges in protein-encapsulated microparticle systems. Since protein release during the initial stage depends mostly on the diffusional escape of the protein, major approaches to prevent the initial burst have focused on efficient encapsulation of the protein within the microparticles. For this reason, control of encapsulation efficiency and the extent of initial burst are based on common formulation parameters. The present article provides a literature review of the formulation parameters that are known to influence the two properties in the emulsion-solvent evaporation/extraction method. Physical and chemical properties of encapsulating polymers, solvent systems, polymer-drug interactions, and properties of the continuous phase are some of the influential variables. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of the dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

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Section: Composition Of Continuous Phasementioning

confidence: 89%

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

2004

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“…biodegradable polymers such as polylactic acid, polyglycolic acids and polylactic-co-glycolic acid [15,16]. These microspheres, however, are not ideal as their degradation products have been observed to cause an inflammatory response [4,5].…”

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 99%

The controlled release of drugs from emulsified, sol gel processed silica microspheres

2009

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Controlled release silica sol gels are room temperature processed, porous, resorbable materials with generally good compatibility. Many molecules including drugs, proteins and growth factors can be released from sol gels and the quantity and duration of the release can vary widely. Processing parameters render these release properties exquisitely versatile. The synthesis of controlled release sol gels typically includes acid catalyzed hydrolysis to form a sol with the molecules included. This is then followed by casting, aging and drying. Additional steps such as grinding and sieving are required to produce sol gel granules of a desirable size. In this study, we focus on the synthesis of sol gel microspheres by using a novel process with only two steps. The novelty is related to acid-base catalysis of the sol prior to emulsification. Sol gel microspheres containing either vancomycin (antibiotic) or bupivacaine (analgesic) were successfully synthesized using this method. Both drugs showed controlled, load dependent and time dependent release from the microspheres. The in vitro release properties of sol gel microspheres were remarkably different from those of sol gel granules produced by grinding and sieving. In contrast to a fast, short-term release from granules, the release from microspheres was slower and of longer duration. In addition, the degradation rate of microspheres was significantly slower than that of the granules. Using various mathematical models, the data reveal that the release from sol gel powder is governed by two distinct phases of release. In addition, the release from emulsified microspheres is delayed, a finding that can be attributed to differences in surface properties of the particles produced by emulsification and those produced by casting and grinding. The presented results represent an excellent data set for designing and implementing preclinical studies. t r a c tControlled release silica sol gels are room temperature processed, porous, resorbable materials with generally good compatibility. Many molecules including drugs, proteins and growth factors can be released from sol gels and the quantity and duration of the release can vary widely. Processing parameters render these release properties exquisitely versatile. The synthesis of controlled release sol gels typically includes acid catalyzed hydrolysis to form a sol with the molecules included. This is then followed by casting, aging and drying. Additional steps such as grinding and sieving are required to produce sol gel granules of a desirable size. In this study, we focus on the synthesis of sol gel microspheres by using a novel process with only two steps. The novelty is related to acid-base catalysis of the sol prior to emulsification. Sol gel microspheres containing either vancomycin (antibiotic) or bupivacaine (analgesic) were successfully synthesized using this method. Both drugs showed controlled, load dependent and time dependent release from the microspheres. The in vitro release properties of sol gel microspher...

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“…ES 100 being a pH-sensitive polymer, is soluble above pH 7.0, thus pH 6.4 was selected for the study because if the microparticles are able to sustain drug release at the borderline pH, these will be able to sustain the release at lower intestinal pH values as well. Another biorelevant consideration is that the transit time of a drug through the absorptive area of the gastrointestinal tract is between 9 and 12 h this includes 2-3 h of gastric residence time (18). Thus the capsulated formulations were initially tested for drug release in the simulated gastric pH for 2 h followed by drug release in simulated intestinal pH.…”

Section: In Vitro Drug Releasementioning

confidence: 99%

Design and In Vitro Performance Evaluation of Purified Microparticles of Pravastatin Sodium for Intestinal Delivery

Garg

Pathak

2011

AAPS PharmSciTech

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Abstract. The purpose of research was to develop a mucoadhesive multiparticulate sustained drug delivery system of pravastatin sodium, a highly water-soluble and poorly bioavailable drug, unstable at gastric pH. Mucoadhesive microparticles were formulated using eudragit S100 and ethyl cellulose as mucoadhesive polymers. End-step modification of w/o/o double emulsion solvent diffusion method was attempted to improve the purity of the product, that can affect the dose calculations of sustained release formulations and hence bioavailability. Microparticles formed were discrete, free flowing, and exhibited good mucoadhesive properties. DSC and DRS showed stable character of drug in microparticles and absence of drug polymer interaction. The drug to polymer ratio and surfactant concentration had significant effect on mean particle size, drug release, and entrapment efficiency. Microparticles made with drug: eudragit S100 ratio of 1:3 (F6) exhibited maximum entrapment efficiency of 72.7% and ex vivo mucoadhesion time of 4.15 h. In vitro permeation studies on goat intestinal mucosa demonstrated a flux rate (1,243 μg/cm 2 /h) that was 169 times higher than the flux of pure drug. The gastric instability problem was overcome by formulating the optimized microparticles as enteric-coated capsules that provided a sustained delivery of the highly water-soluble drug for 12 h beyond the gastric region. The release mechanism was identified as fickian diffusion (n=0.4137) for the optimized formulation F6. Conclusively, a drug delivery system was successfully developed that showed delayed and sustained release up to 12 h and could be potentially useful to overcome poor bioavailability problems associated with pravastatin sodium.

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Preparation and Characterization of Polylactic Acid Microspheres Containing Bovine Insulin by a w/o/w Emulsion Solvent Evaporation Method.

Cited by 41 publications

References 0 publications

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

The controlled release of drugs from emulsified, sol gel processed silica microspheres

Design and In Vitro Performance Evaluation of Purified Microparticles of Pravastatin Sodium for Intestinal Delivery

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