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Svoboda R, Kozlová K. Thermo-Structural Characterization of Phase Transitions in Amorphous Griseofulvin: From Sub-T g Relaxation and Crystal Growth to High-Temperature Decomposition. Molecules 2024; 29:1516. [PMID: 38611796 PMCID: PMC11013327 DOI: 10.3390/molecules29071516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 03/23/2024] [Accepted: 03/25/2024] [Indexed: 04/14/2024] Open
Abstract
The processes of structural relaxation, crystal growth, and thermal decomposition were studied for amorphous griseofulvin (GSF) by means of thermo-analytical, microscopic, spectroscopic, and diffraction techniques. The activation energy of ~395 kJ·mol-1 can be attributed to the structural relaxation motions described in terms of the Tool-Narayanaswamy-Moynihan model. Whereas the bulk amorphous GSF is very stable, the presence of mechanical defects and micro-cracks results in partial crystallization initiated by the transition from the glassy to the under-cooled liquid state (at ~80 °C). A key aspect of this crystal growth mode is the presence of a sufficiently nucleated vicinity of the disrupted amorphous phase; the crystal growth itself is a rate-determining step. The main macroscopic (calorimetrically observed) crystallization process occurs in amorphous GSF at 115-135 °C. In both cases, the common polymorph I is dominantly formed. Whereas the macroscopic crystallization of coarse GSF powder exhibits similar activation energy (~235 kJ·mol-1) as that of microscopically observed growth in bulk material, the activation energy of the fine GSF powder macroscopic crystallization gradually changes (as temperature and/or heating rate increase) from the activation energy of microscopic surface growth (~105 kJ·mol-1) to that observed for the growth in bulk GSF. The macroscopic crystal growth kinetics can be accurately described in terms of the complex mechanism, utilizing two independent autocatalytic Šesták-Berggren processes. Thermal decomposition of GSF proceeds identically in N2 and in air atmospheres with the activation energy of ~105 kJ·mol-1. The coincidence of the GSF melting temperature and the onset of decomposition (both at 200 °C) indicates that evaporation may initiate or compete with the decomposition process.
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Affiliation(s)
- Roman Svoboda
- Department of Physical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice, Czech Republic;
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Hazt B, Pereira Parchen G, Fernanda Martins do Amaral L, Rondon Gallina P, Martin S, Hess Gonçalves O, Alves de Freitas R. Unconventional and conventional Pickering emulsions: Perspectives and challenges in skin applications. Int J Pharm 2023; 636:122817. [PMID: 36905974 DOI: 10.1016/j.ijpharm.2023.122817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 02/27/2023] [Accepted: 03/06/2023] [Indexed: 03/13/2023]
Abstract
Pickering emulsions are free from molecular and classical surfactants and are stabilized by solid particles, creating long-term stability against emulsion coalescence. Additionally, these emulsions are both environmentally and skin-friendly, creating new and unexplored sensorial perceptions. Although the literature mostly describes conventional emulsions (oil-in-water), there are unconventional emulsions (multiple, oil-in-oil and water-in-water) with excellent prospects and challenges in skin application as oil-free systems, permeation enhancers and topical drug delivery agents, with various possibilities in pharmaceutical and cosmetic products. However, up to now, these conventional and unconventional Pickering emulsions are not yet available as commercial products. This review brings to the discussion some important aspects such as the use of phases, particles, rheological and sensorial perception, as well as current trends in the development of these emulsions.
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Affiliation(s)
- Bianca Hazt
- Chemistry Department, Universidade Federal do Paraná (UFPR), R. Coronel F. H. dos Santos, 210, Curitiba - 81531-980, PR, Brazil.
| | - Gabriela Pereira Parchen
- Department of Pharmacy, Universidade Federal do Paraná (UFPR), Av. Pref. Lothário Meissner, 632, Curitiba - 80210-170, PR, Brazil.
| | | | - Patrícia Rondon Gallina
- Department of Pharmacy, Universidade Federal do Paraná (UFPR), Av. Pref. Lothário Meissner, 632, Curitiba - 80210-170, PR, Brazil
| | - Sandra Martin
- Mackenzie School of Medicine, R. Padre Anchieta, 2770, Curitiba - 80730-000, PR, Brazil
| | - Odinei Hess Gonçalves
- Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253 Bragança, Portugal; Post-Graduation Program of Food Technology, Federal University of Technology - Paraná, Via Rosalina Maria Dos Santos, 1233, Campo Mourão - 87301-899, PR, Brazil.
| | - Rilton Alves de Freitas
- Department of Pharmacy, Universidade Federal do Paraná (UFPR), Av. Pref. Lothário Meissner, 632, Curitiba - 80210-170, PR, Brazil.
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