Structure formation in injectable poly(lactide–co-glycolide) depots

Wang, Liwei; Kleiner, Lothar W.; Venkatraman, Subbu S.

doi:10.1016/s0168-3659(03)00198-6

Cited by 43 publications

(21 citation statements)

References 17 publications

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“…11 The enthalpy associated with this peak increases with aging time. On a temporal level, this increase parallels that of the dynamic viscosity obtained from rheological experiments.…”

Section: Differential Scanning Calorimetry (Dsc) Observationsmentioning

confidence: 98%

“…In the previous articles, 11,12 we had shown that the Resomer RG502/BB solution exhibited a complex flow behavior influenced by both gelation and degradation during aging and in vitro (upon injection into buffer). In this article, we report on the flow behavior of different polymers with different L/G ratios and from different manufacturers.…”

Section: Rheological Propertiesmentioning

confidence: 99%

“…In our previous work, 11,12 we studied a novel thermoreversible gel. This gel was formed from a solution of poly-(lactide-co-glycolide) (PLGA) with an L/G ratio of 50:50 dissolved in benzyl benzoate (BB).…”

Section: Introductionmentioning

confidence: 99%

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Structure formation in injectable poly(lactide‐co‐glycolide) depots. II. Nature of the gel

et al. 2004

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The benzyl benzoate solutions of poly(D,L-lactide-co-glycolide), a random oriented synthesized copolymer with L/G ratio of 50:50, have been shown to form gels during aging and upon injection into buffer or water. The gelation properties influence drug release kinetics for these injectable, depot-forming solutions. In this article, we report on the mechanism of gelation. We find that only polymers that have a certain average block length of glycolide units form gels during aging as well as depots upon in vitro. Thus, gel formation is likely due to the formation of ordered solvated aggregates of blocky glycolide units. Rheometry, differential scanning calorimetry, and nuclear magnetic resonance were used to investigate the gelation kinetics and the polymer molecular parameters. Of all the polymers used, poly(lactide-coglycolide)s with glycolide average block length <2.9 did not show any gelation behavior. The details of the gelation process are also solvent dependent.

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“…11 The enthalpy associated with this peak increases with aging time. On a temporal level, this increase parallels that of the dynamic viscosity obtained from rheological experiments.…”

Section: Differential Scanning Calorimetry (Dsc) Observationsmentioning

confidence: 98%

Section: Rheological Propertiesmentioning

confidence: 99%

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Structure formation in injectable poly(lactide‐co‐glycolide) depots. II. Nature of the gel

et al. 2004

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“…The most popular and biocompatible solvent used is N-methyl-2-pyrrolidone (NMP). [9][10][11][12][13] Poly(d,l-lactide-co-glycolide) (PLGA) is the most successfully used biodegradable and biocompatible polymer because of its two biodegradable hydrolysis products, lactic and glycolic acids (Figure 1). 14 The properties of PLGA that affect drug release, including its molecular weight (MW), lactide/glycolide ratio, and thermal properties, have been thoroughly investigated.…”

Section: Introductionmentioning

confidence: 99%

Application of hydroxyapatite nanoparticles in development of an enhanced formulation for delivering sustained release of triamcinolone acetonide

Koocheki

Madaeni²,

Niroomandi³

2011

IJN

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We report an analysis of in vitro and in vivo drug release from an in situ formulation consisting of triamcinolone acetonide (TR) and poly( d , l -lactide-co-glycolide) (PLGA) and the additives glycofurol (GL) and hydroxyapatite nanoparticles (HA). We found that these additives enhanced drug release rate. We used the Taguchi method to predict optimum formulation variables to minimize the initial burst. This method decreased the burst rate from 8% to 1.3%. PLGA-HA acted as a strong buffer, thereby preventing tissue inflammation at the injection site caused by the acidic degradation products of PLGA. Characterization of the optimized formulation by a variety of techniques, including scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and Fourier transform near infrared spectroscopy, revealed that the crystalline structure of TR was converted to an amorphous form. Therefore, this hydrophobic agent can serve as an additive to modify drug release rates. Data generated by in vitro and in vivo experiments were in good agreement.

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“…The solvents used for the polymer phase can be N-methyl-2-pyrrolidont (NMP), triacetin, glycofurol, dimethylsulfoxide (DMSO), benzyl alcohol and benzyl benzoate, which are all water-miscible and acceptably biocompatible. [7][8][9] As for the polymer, (D,L-lactide) (PLA) and poly(D,L-lactide-co-glycolide) (PLGA) are most widely used.…”

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confidence: 99%

Optimized Preparation of in Situ Forming Microparticles for the Parenteral Delivery of Vinpocetine

Chen

et al. 2008

CHEMICAL & PHARMACEUTICAL BULLETIN

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A spherical symmetric design-response surface methodology was applied to optimize the preparation of vinpocetine-loaded poly(D,L-lactide-co-glycolide) PLGA in situ forming microparticles (ISM system). The influence of the ratio of PLGA to vinpocetine (w/w), the concentration of Tween 80 (w/v) and the volume of propylene glycol on the burst release, medium particle diameter and size distribution was evaluated. Scan electron microscopy of the optimized in situ microparticles exhibited spherical shape, and vinpocetine-loading mainly inside the microparticles. The data showed that the release of vinpocetine from in situ microparticles in vitro and in vivo lasted about 40 d. In vivo pharmacokinetic characteristics of the optimized in situ microparticles was assessed after they were intramuscularly injected into rats. HPLC method was used to determine the plasma concentration of vinpocetine. The absolute bioavailability of vinpocetine in the microparticles was 27.6% in rats, which suggested that PLGA in situ microparticles were a valuable system for the delivery of vinpocetine.

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Structure formation in injectable poly(lactide–co-glycolide) depots

Cited by 43 publications

References 17 publications

Structure formation in injectable poly(lactide‐co‐glycolide) depots. II. Nature of the gel

Structure formation in injectable poly(lactide‐co‐glycolide) depots. II. Nature of the gel

Application of hydroxyapatite nanoparticles in development of an enhanced formulation for delivering sustained release of triamcinolone acetonide

Optimized Preparation of in Situ Forming Microparticles for the Parenteral Delivery of Vinpocetine

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