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Assessment of Residual Solvent and Drug in PLGA Microspheres by Derivative Thermogravimetry.

ABSTRACT: Thermogravimetry does not give specific information on residual organic solvents in polymeric matrices unless it is hyphenated with the so-called evolved gas analysis. The purpose of this study was to apply, for the first time, derivative thermogravimetry (DTG) to characterize a residual solvent and a drug in poly-d,l-lactide-co-glycolide (PLGA) microspheres. Ethyl formate, an ICH class 3 solvent, was used to encapsulate progesterone into microspheres. DTG provided a distinct peak, displaying the onset and end temperatures at which ethyl formate started to evolve from to where it completely escaped out of the microspheres. DTG also gave the area and height of the solvent peak, as well as the temperature of the highest mass change rate of the microspheres. These derivative parameters allowed for the measurement of the amount of residual ethyl formate in the microspheres. Interestingly, progesterone affected not only the residual solvent amount but also these derivative parameters. Another intriguing finding was that there was a linear relationship between progesterone content and the peak height of ethyl formate. The residual solvent data calculated by DTG were quite comparable to those measured by gas chromatography. In summary, DTG could be an efficient and practical quality control tool to evaluate residual solvents and drugs in various polymeric matrices.

SUBMITTER: Shim H

PROVIDER: S-EPMC7407183 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Assessment of Residual Solvent and Drug in PLGA Microspheres by Derivative Thermogravimetry.

Shim Hyunjin H Sah Hongkee H

Pharmaceutics 20200704 7

Thermogravimetry does not give specific information on residual organic solvents in polymeric matrices unless it is hyphenated with the so-called evolved gas analysis. The purpose of this study was to apply, for the first time, derivative thermogravimetry (DTG) to characterize a residual solvent and a drug in poly-<i>d,l</i>-lactide-<i>co</i>-glycolide (PLGA) microspheres. Ethyl formate, an ICH class 3 solvent, was used to encapsulate progesterone into microspheres. DTG provided a distinct peak, ...[more]

PMID: 32635484

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Project description:Herein, we describe the detailed development of a simple and effective method to microencapsulate vaccine antigens in poly(lactic-co-glycolic acid) (PLGA) by simple mixing of preformed active self-microencapsulating (SM) PLGA microspheres in a low concentration aqueous antigen solution at modest temperature (10-38 °C). Co-encapsulating protein-sorbing vaccine adjuvants and polymer plasticizers were used to "actively" load the protein in the polymer pores and facilitate polymer self-healing at a temperature>the hydrated polymer glass transition temperature, respectively. The microsphere formulation parameters and loading conditions to provide optimal active self-healing microencapsulation of vaccine antigens in PLGA was investigated. Active self-healing encapsulation of two antigens, ovalbumin and tetanus toxoid (TT), in PLGA microspheres was adjusted by preparing blank microspheres containing different vaccine adjuvants (aluminum hydroxide (Al(OH)?) or calcium phosphate). Active loading of vaccine antigen in Al(OH)?-PLGA microspheres was found to: a) increase with an increasing loading of Al(OH)? (0.88-3 wt.%) and addition of porosigen, b) decrease when the inner Al(OH)?/trehalose phase to 1 mL outer oil phase and size of microspheres was respectively >0.2 mL and 63 ?m, and c) change negligibly by PLGA concentration and initial incubation (loading) temperature. Encapsulation of protein sorbing Al(OH)? in PLGA microspheres resulted in suppression of self-healing of PLGA pores, which was then overcome by improving polymer chain mobility, which in turn was accomplished by coincorporating hydrophobic plasticizers in PLGA. Active self-healing microencapsulation of manufacturing process-labile TT in PLGA was found to: a) obviate micronization- and organic solvent-induced TT degradation, b) improve antigen loading (1.4-1.8 wt.% TT) and encapsulation efficiency (~97%), c) provide nearly homogeneous distribution and stabilization of antigen in polymer, and d) provide improved in vitro controlled release of antigenic TT.

Dataset Information

Assessment of Residual Solvent and Drug in PLGA Microspheres by Derivative Thermogravimetry.

Publications

Assessment of Residual Solvent and Drug in PLGA Microspheres by Derivative Thermogravimetry.

Similar Datasets

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