Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions
<b>Background/Objectives</b>: This study investigates the impact of high humidity (25 °C, 75% relative humidity) on gelatin and hydroxypropyl methylcellulose (HPMC) capsules used in dry powder inhalers (DPIs), focusing on moisture dynamics, structural responses, and mechanical performanc...
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2025-07-01
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| Online Access: | https://www.mdpi.com/1999-4923/17/7/877 |
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| author | Sabrina Magramane Nikolett Kállai-Szabó Dóra Farkas Károly Süvegh Romána Zelkó István Antal |
| author_facet | Sabrina Magramane Nikolett Kállai-Szabó Dóra Farkas Károly Süvegh Romána Zelkó István Antal |
| author_sort | Sabrina Magramane |
| collection | DOAJ |
| description | <b>Background/Objectives</b>: This study investigates the impact of high humidity (25 °C, 75% relative humidity) on gelatin and hydroxypropyl methylcellulose (HPMC) capsules used in dry powder inhalers (DPIs), focusing on moisture dynamics, structural responses, and mechanical performance, with an emphasis on understanding how different capsule types respond to prolonged exposure to humid conditions. <b>Methods</b>: Capsules were exposed to controlled humidity conditions, and moisture uptake was measured via thermal analysis. Visual observations of silica bead color changes were performed to assess moisture absorption, while surface wettability was measured using the sessile drop method. Hardness testing, mechanical deformation, and puncture tests were performed to evaluate structural and mechanical changes. Positron annihilation lifetime spectroscopy (PALS) was used to analyze free volume expansion. <b>Results</b>: HPMC capsules exhibited rapid moisture uptake, attributed to their lower equilibrium moisture content and ability to rearrange dynamically, preventing brittleness. In contrast, gelatin capsules showed slower moisture absorption but reached higher equilibrium levels, resulting in plasticization and softening. Mechanical testing showed that HPMC capsules retained structural integrity with minimal deformation, while gelatin capsules became softer and exhibited reduced puncture resistance. Structural analysis revealed greater free volume expansion in HPMC capsules, consistent with their amorphous nature, compared with gelatin’s semi-crystalline matrix. <b>Conclusions</b>: HPMC capsules demonstrated superior humidity resilience, making them more suitable for protecting moisture-sensitive active pharmaceutical ingredients (APIs) in DPI formulations. These findings underline the importance of appropriate storage conditions, as outlined in the Summary of Product Characteristics, to ensure optimal capsule performance throughout patient use. |
| format | Article |
| id | doaj-art-29971c8bfb0c499593be2c52eec780d4 |
| institution | Kabale University |
| issn | 1999-4923 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Pharmaceutics |
| spelling | doaj-art-29971c8bfb0c499593be2c52eec780d42025-08-20T03:56:45ZengMDPI AGPharmaceutics1999-49232025-07-0117787710.3390/pharmaceutics17070877Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity ConditionsSabrina Magramane0Nikolett Kállai-Szabó1Dóra Farkas2Károly Süvegh3Romána Zelkó4István Antal5Department of Pharmaceutics, Semmelweis University, Hőgyes Str. 7, H-1092 Budapest, HungaryDepartment of Pharmaceutics, Semmelweis University, Hőgyes Str. 7, H-1092 Budapest, HungaryDepartment of Pharmaceutics, Semmelweis University, Hőgyes Str. 7, H-1092 Budapest, HungaryDepartment of Analytical Chemistry, Eötvös Loránd University, Pázmány Péter Sétány 1/a, H-1117 Budapest, HungaryCenter for Pharmacology and Drug Research & Development, Semmelweis University, 1085 Budapest, HungaryDepartment of Pharmaceutics, Semmelweis University, Hőgyes Str. 7, H-1092 Budapest, Hungary<b>Background/Objectives</b>: This study investigates the impact of high humidity (25 °C, 75% relative humidity) on gelatin and hydroxypropyl methylcellulose (HPMC) capsules used in dry powder inhalers (DPIs), focusing on moisture dynamics, structural responses, and mechanical performance, with an emphasis on understanding how different capsule types respond to prolonged exposure to humid conditions. <b>Methods</b>: Capsules were exposed to controlled humidity conditions, and moisture uptake was measured via thermal analysis. Visual observations of silica bead color changes were performed to assess moisture absorption, while surface wettability was measured using the sessile drop method. Hardness testing, mechanical deformation, and puncture tests were performed to evaluate structural and mechanical changes. Positron annihilation lifetime spectroscopy (PALS) was used to analyze free volume expansion. <b>Results</b>: HPMC capsules exhibited rapid moisture uptake, attributed to their lower equilibrium moisture content and ability to rearrange dynamically, preventing brittleness. In contrast, gelatin capsules showed slower moisture absorption but reached higher equilibrium levels, resulting in plasticization and softening. Mechanical testing showed that HPMC capsules retained structural integrity with minimal deformation, while gelatin capsules became softer and exhibited reduced puncture resistance. Structural analysis revealed greater free volume expansion in HPMC capsules, consistent with their amorphous nature, compared with gelatin’s semi-crystalline matrix. <b>Conclusions</b>: HPMC capsules demonstrated superior humidity resilience, making them more suitable for protecting moisture-sensitive active pharmaceutical ingredients (APIs) in DPI formulations. These findings underline the importance of appropriate storage conditions, as outlined in the Summary of Product Characteristics, to ensure optimal capsule performance throughout patient use.https://www.mdpi.com/1999-4923/17/7/877gelatinHPMCcapsulesdry powder inhalers (DPIs)stabilitypositron annihilation lifetime spectroscopy (PALS) |
| spellingShingle | Sabrina Magramane Nikolett Kállai-Szabó Dóra Farkas Károly Süvegh Romána Zelkó István Antal Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions Pharmaceutics gelatin HPMC capsules dry powder inhalers (DPIs) stability positron annihilation lifetime spectroscopy (PALS) |
| title | Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions |
| title_full | Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions |
| title_fullStr | Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions |
| title_full_unstemmed | Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions |
| title_short | Comparative Evaluation of Gelatin and HPMC Inhalation Capsule Shells Exposed to Simulated Humidity Conditions |
| title_sort | comparative evaluation of gelatin and hpmc inhalation capsule shells exposed to simulated humidity conditions |
| topic | gelatin HPMC capsules dry powder inhalers (DPIs) stability positron annihilation lifetime spectroscopy (PALS) |
| url | https://www.mdpi.com/1999-4923/17/7/877 |
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