Protein-loaded poly(dl-lactide-co-glycolide) microparticles for oral administration: formulation, structural and release characteristics

Rafati, Hasan; Coombes, Allan G.A.; Adler, Jeremy; Holland, Julie; Davis, S.S.

doi:10.1016/s0168-3659(96)01475-7

Cited by 192 publications

(102 citation statements)

References 26 publications

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“…Encapsulation efficiency increases with increasing polymer concentration (Mehta et al, 1996;Rafati et al, 1997;Li et al, 1999). For example, the encapsulation efficiency increased from 53.1 to 70.9% when concentration of the polymer increased from 20.0 to 32.5% (Mehta et al, 1996).…”

Section: Polymer Concentrationmentioning

confidence: 95%

“…First, when highly concentrated, the polymer precipitates faster on the surface of the dispersed phase and prevents drug diffusion across the phase boundary (Rafati et al, 1997). Second, the high concentration increases viscosity of the solution and delays the drug diffusion within the polymer droplets (Bodmeier and McGinity, 1988).…”

Section: Polymer Concentrationmentioning

confidence: 99%

“…First, burst release occurs mainly due to the heterogeneous drug distribution. Proteins that are either loosely associated with the surface or embedded in the surface layer are responsible for the burst release (Sah et al, 1994;O'Hagan et al, 1994;Igartua et al, 1997;Rafati et al, 1997). Second, morphology of the microparticles causes initial burst: The drugs escape from the polymeric matrices through the pores and cracks that form during the microparticle fabrication process (Huang and Brazel, 2001;Yang et al, 2001).…”

Section: Causes Of Initial Burst Releasementioning

confidence: 99%

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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: Polymer Concentrationmentioning

confidence: 95%

Section: Polymer Concentrationmentioning

confidence: 99%

Section: Causes Of Initial Burst Releasementioning

confidence: 99%

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Control of encapsulation efficiency and initial burst in polymeric microparticle systems

2004

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“…These patterns of enhanced entrapment efficiency are attributed to the higher viscosity of the DCM phase as more polymer amount is present and the ensuing larger size of the primary emulsion droplets. Furthermore, higher polymer concentrations give rise to more rapid polymer deposition as the DCM is removed from the system, which is expected to retard any unwanted insulin dissolution into the continuous phase of the secondary emulsion (Rafati et al, 1997).…”

Section: Effect Of Polymer Concentrationmentioning

confidence: 99%

Preparation and in vivo evaluation of insulin-loaded biodegradable nanoparticles prepared from diblock copolymers of PLGA and PEG

Haggag

Abdel-Wahab

Ojo

et al. 2016

International Journal of Pharmaceutics

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A B S T R A C TThe aim of this study was to design a controlled release vehicle for insulin to preserve its stability and biological activity during fabrication and release. A modified, double emulsion, solvent evaporation, technique using homogenisation force optimised entrapment efficiency of insulin into biodegradable nanoparticles (NP) prepared from poly (DL-lactic-co-glycolic acid) (PLGA) and its PEGylated diblock copolymers. Formulation parameters (type of polymer and its concentration, stabiliser concentration and volume of internal aqueous phase) and physicochemical characteristics (size, zeta potential, encapsulation efficiency, in vitro release profiles and in vitro stability) were investigated. In vivo insulin sensitivity was tested by diet-induced type II diabetic mice. Bioactivity of insulin was studied using Swiss TO mice with streptozotocin-induced type I diabetic profile. Insulin-loaded NP were spherical and negatively charged with an average diameter of 200-400 nm. Insulin encapsulation efficiency increased significantly with increasing ratio of co-polymeric PEG. The internal aqueous phase volume had a significant impact on encapsulation efficiency, initial burst release and NP size. Optimised insulin NP formulated from 10% PEG-PLGA retained insulin integrity in vitro, insulin sensitivity in vivo and induced a sustained hypoglycaemic effect from 3 h to 6 days in type I diabetic mice..

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“…Furthermore, RG 503H has a higher inherent viscosity than RG 502H (0.38 vs 0.19 dl/g). Consequently, the increase in the polymer solution viscosity led to a higher entrapment of the protein because it limits the migration of the protein from the inner phase towards the outer one [34].…”

Section: Gdnf Encapsulation Efficiencymentioning

confidence: 99%

Sustained release of bioactive glycosylated glial cell-line derived neurotrophic factor from biodegradable polymeric microspheres

Garbayo

Ansorena

Lanciego

et al. 2008

European Journal of Pharmaceutics and Biopharmaceutics

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Protein-loaded poly(dl-lactide-co-glycolide) microparticles for oral administration: formulation, structural and release characteristics

Cited by 192 publications

References 26 publications

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Preparation and in vivo evaluation of insulin-loaded biodegradable nanoparticles prepared from diblock copolymers of PLGA and PEG

Sustained release of bioactive glycosylated glial cell-line derived neurotrophic factor from biodegradable polymeric microspheres

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