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Pharmaceutics
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Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!
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Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!

A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Drug Delivery and Controlled Release".

Deadline for manuscript submissions: closed (20 January 2022) | Viewed by 22220

Special Issue Editor

Dr. Susanne Florin-Muschert

E-Mail Website
Guest Editor
Advanced Drug Delivery Systems – Inserm, CHU Lille, Lille University, U1008, F-59000 Lille, France
Interests: solid dosage forms; controlled drug delivery

Special Issue Information

Dear colleagues,

This Special Issue collects publications elucidating the power of versatile imaging techniques to explain mass transport mechanisms from drug delivery devices of any kind.

Drug release mechanisms can be highly complex especially with controlled delivery devices, such as coated or matrix systems for delayed and sustained release or drug delivery devices for improved bioavailability of insoluble drugs. Understanding the underlying mass transport mechanisms can often be misinterpreted when only theoretical methods are applied. A profound understanding of the fate of the drug molecule within the dosage form during dissolution can be gained by rendering the drug visible during its way out of the device. Analytical spectroscopic, microscopic, tomographical, or other imaging techniques can be used to do so, for example. They allow to paint a clear picture on what is going on within diverse drug delivery devices during dissolution and thus help development of reliable dosage forms.

Dr. Susanne Muschert
Guest Editor

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Keywords

  • Controlled drug release devices
  • Drug release mechanisms
  • Dosage forms
  • Spectroscopic methods
  • Raman spectroscopy
  • Electron microscopy
  • Laser scanning confocal microscopy
  • Atomic force microscopy
  • Tomography
  • Magnetic resonance imaging
  • Terahertz imaging
  • Imaging techniques

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Published Papers (6 papers)

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Editorial

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3 pages, 623 KiB  
Editorial
Drug-Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!
by Susanne Florin-Muschert
Pharmaceutics 2022, 14(6), 1165; https://doi.org/10.3390/pharmaceutics14061165 - 30 May 2022
Viewed by 1609
Abstract
Imaging techniques such as Raman spectroscopy, electron microscopy, laser scanning confocal microscopy, atomic force microscopy, tomography, magnetic resonance imaging, and terahertz are powerful tools to elucidate drug-release mechanisms from different types of delivery devices [...] Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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Research

Jump to: Editorial

20 pages, 6273 KiB  
Article
Influence of Massage and Skin Hydration on Dermal Penetration Efficacy of Nile Red from Petroleum Jelly—An Unexpected Outcome
by Vasudha Kaushik, Yameera Ganashalingam, Robert Schesny, Christian Raab, Soma Sengupta and Cornelia M. Keck
Pharmaceutics 2021, 13(12), 2190; https://doi.org/10.3390/pharmaceutics13122190 - 18 Dec 2021
Cited by 16 | Viewed by 5233
Abstract
The study aimed at comparing the influence of direct and indirect skin hydration as well as massage on the dermal penetration efficacy of active compounds. Nile red was used as a lipophilic drug surrogate and was incorporated into Vaseline (petroleum jelly). The formulation [...] Read more.
The study aimed at comparing the influence of direct and indirect skin hydration as well as massage on the dermal penetration efficacy of active compounds. Nile red was used as a lipophilic drug surrogate and was incorporated into Vaseline (petroleum jelly). The formulation was applied with and without massage onto either dry skin or pre-hydrated, moist skin. It was expected that the occlusive properties of Vaseline in combination with massage and enhanced skin hydration would cause a superposition of penetration-enhancing effects, which should lead to a tremendous increase in the dermal penetration efficacy of the lipophilic drug surrogate. Results obtained were diametral to the expectations, and various reasons were identified for causing the effect observed. Firstly, it was found that Vaseline undergoes syneresis after topical application. The expulsed mineral oil forms a film on top of the skin, and parts of it penetrate into the skin. The lipophilic drug surrogate, which is dissolved in the mineral oil, enters the skin with the mineral oil, i.e., via a solvent drag mechanism. Secondly, it was found that massage squeezes the skin and causes the expulsion of water from deeper layers of the SC. The expulsed water can act as a water barrier that prevents the penetration of lipophilic compounds and promotes the penetration of hydrophilic compounds. Based on the data, it is concluded that dermal penetration is a complex process that cannot only be explained by Fick’s law. It is composed of at least three different mechanisms. The first mechanism is the penetration of active ingredients with their solvents into the skin (convection, solvent drag), the second mechanism is the penetration of the active ingredient via passive diffusion, and the third mechanism can involve local penetration phenomena, e.g., the formation of liquid menisci and particle-associated penetration enhancement, which occur upon the evaporation of water and/or other ingredients from the formulation on top of the skin. Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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13 pages, 1618 KiB  
Article
The Effect of Capsule-in-Capsule Combinations on In Vivo Disintegration in Human Volunteers: A Combined Imaging and Salivary Tracer Study
by Adrian Rump, Franziska N. Weiss, Louisa Schulz, Marie-Luise Kromrey, Eberhard Scheuch, Mladen V. Tzvetkov, Tyler White, Shane Durkee, Kevin W. Judge, Vincent Jannin, Aouatef Bellamine, Werner Weitschies and Michael Grimm
Pharmaceutics 2021, 13(12), 2002; https://doi.org/10.3390/pharmaceutics13122002 - 25 Nov 2021
Cited by 15 | Viewed by 4433
Abstract
Controlling the time point and site of the release of active ingredients within the gastrointestinal tract after administration of oral delivery systems is still a challenge. In this study, the effect of the combination of small capsules (size 3) and large capsules (size [...] Read more.
Controlling the time point and site of the release of active ingredients within the gastrointestinal tract after administration of oral delivery systems is still a challenge. In this study, the effect of the combination of small capsules (size 3) and large capsules (size 00) on the disintegration site and time was investigated using magnetic resonance imaging (MRI) in combination with a salivary tracer technique. As capsule shells, Vcaps® HPMC capsules, Vcaps® Plus HPMC capsules, gelatin and DRcaps® designed release capsules were used. The three HPMC-based capsules (Vcaps®, Vcaps® Plus and DRcaps® capsules) were tested as single capsules; furthermore, seven DUOCAP® capsule-in-capsule combinations were tested in a 10-way crossover open-label study in six healthy volunteers. The capsules contained iron oxide and hibiscus tea powder as tracers for visualization in MRI, and two different caffeine species (natural caffeine and 13C3) to follow caffeine release and absorption as measured by salivary levels. Results showed that the timing and location of disintegration in the gastrointestinal tract can be measured and differed when using different combinations of capsule shells. Increased variability among the six subjects was observed in most of the capsule combinations. The lowest variability in gastrointestinal localization of disintegration was observed for the DUOCAP® capsule-in-capsule configuration using a DRcaps® designed release capsule within a DRcaps® designed release outer capsule. In this combination, the inner DRcaps® designed release capsule always opened reliably after reaching the ileum. Thus, this combination enables targeted delivery to the distal small intestine. Among the single capsules tested, Vcaps® Plus HPMC capsules showed the fastest and most consistent disintegration. Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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Graphical abstract

19 pages, 9202 KiB  
Article
Towards a Better Understanding of Verapamil Release from Kollicoat SR:IR Coated Pellets Using Non-Invasive Analytical Tools
by Julie Fahier, Branko Vukosavljevic, Laure De Kinder, Hugues Florin, Jean-François Goossens, Maike Windbergs, Florence Siepmann, Juergen Siepmann and Susanne Muschert
Pharmaceutics 2021, 13(10), 1723; https://doi.org/10.3390/pharmaceutics13101723 - 18 Oct 2021
Cited by 5 | Viewed by 3135
Abstract
The aim of this study was to gain deeper insight into the mass transport mechanisms controlling drug release from polymer-coated pellets using non-invasive analytical tools. Pellet starter cores loaded with verapamil HCl (10% loading, 45% lactose, 45% microcrystalline cellulose) were prepared by extrusion/spheronization [...] Read more.
The aim of this study was to gain deeper insight into the mass transport mechanisms controlling drug release from polymer-coated pellets using non-invasive analytical tools. Pellet starter cores loaded with verapamil HCl (10% loading, 45% lactose, 45% microcrystalline cellulose) were prepared by extrusion/spheronization and coated with 5% Kollicoat SR:IR 95:5 or 10% Kollicoat SR:IR 90:10. Drug release was measured from ensembles of pellets as well as from single pellets upon exposure to acetate buffer pH = 3.5 and phosphate buffer pH = 7.4. The swelling of single pellets was observed by optical microscopy, while dynamic changes in the pH in the pellet cores were monitored by fluorescence spectroscopy. Also, mathematical modeling using a mechanistically realistic theory as well as SEM and Raman imaging were applied to elucidate whether drug release mainly occurs by diffusion through the intact film coatings or whether crack formation in the film coatings plays a role. Interestingly, fluorescence spectroscopy revealed that the pH within the pellet cores substantially differed upon exposure to acetate buffer pH = 3.5 and phosphate buffer pH = 7.4, resulting in significant differences in drug solubility (verapamil being a weak base) and faster drug release at lower pH: from ensembles of pellets and single pellets. The monitoring of drug release from and the swelling of single pellets indicated that crack formation in the film coatings likely plays a major role, irrespective of the Kollicoat SR:IR ratio/coating level. This was confirmed by mathematical modeling, SEM and Raman imaging. Importantly, the latter technique allowed also for non-invasive measurements, reducing the risk of artifact creation associated with sample cutting with a scalpel. Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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Graphical abstract

24 pages, 3291 KiB  
Article
A New Validation Methodology for In Silico Tools Based on X-ray Computed Tomography Images of Tablets and a Performance Analysis of One Tool
by Sebastian Bollmann and Peter Kleinebudde
Pharmaceutics 2021, 13(9), 1488; https://doi.org/10.3390/pharmaceutics13091488 - 16 Sep 2021
Cited by 3 | Viewed by 3160
Abstract
In silico tools which predict the dissolution of pharmaceutical dosage forms using virtual matrices can be validated with virtual matrices based on X-ray micro-computed tomography images of real pharmaceutical formulations. Final processed images of 3 different tablet batches were used to check the [...] Read more.
In silico tools which predict the dissolution of pharmaceutical dosage forms using virtual matrices can be validated with virtual matrices based on X-ray micro-computed tomography images of real pharmaceutical formulations. Final processed images of 3 different tablet batches were used to check the performance of the in silico tool F-CAD. The goal of this work was to prove the performance of the software by comparing the predicted dissolution profiles to the experimental ones and to check the feasibility and application of the validation concept for in silico tools. Both virtual matrices based on X-ray micro-computed tomography images and designed by the software itself were used. The resulting dissolution curves were compared regarding their similarity to the experimental curve. The kinetics were analysed with the Higuchi and Korsmeyers–Peppas plot. The whole validation concept as such was feasible and worked well. It was possible to identify prediction errors of the software F-CAD and issues with the virtual tablets designed within the software. Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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Graphical abstract

15 pages, 5436 KiB  
Article
Insights into the Control of Drug Release from Complex Immediate Release Formulations
by Runqiao Dong, James C. DiNunzio, Brian P. Regler, Walter Wasylaschuk, Adam Socia and J. Axel Zeitler
Pharmaceutics 2021, 13(7), 933; https://doi.org/10.3390/pharmaceutics13070933 - 23 Jun 2021
Cited by 11 | Viewed by 3302
Abstract
The kinetics of water transport into tablets, and how it can be controlled by the formulation as well as the tablet microstructure, are of central importance in order to design and control the dissolution and drug release process, especially for immediate release tablets. [...] Read more.
The kinetics of water transport into tablets, and how it can be controlled by the formulation as well as the tablet microstructure, are of central importance in order to design and control the dissolution and drug release process, especially for immediate release tablets. This research employed terahertz pulsed imaging to measure the process of water penetrating through tablets using a flow cell. Tablets were prepared over a range of porosity between 10% to 20%. The formulations consist of two drugs (MK-8408: ruzasvir as a spray dried intermediate, and MK-3682: uprifosbuvir as a crystalline drug substance) and NaCl (0% to 20%) at varying levels of concentrations as well as other excipients. A power-law model is found to fit the liquid penetration exceptionally well (average R2>0.995). For each formulation, the rate of water penetration, extent of swelling and the USP dissolution rate were compared. A factorial analysis then revealed that the tablet porosity was the dominating factor for both liquid penetration and dissolution. NaCl more significantly influenced liquid penetration due to osmotic driving force as well as gelling suppression, but there appears to be little difference when NaCl loading in the formulation increases from 5% to 10%. The level of spray dried intermediate was observed to further limit the release of API in dissolution. Full article
(This article belongs to the Special Issue Drug Release Mechanisms Elucidated by Imaging Techniques: Visualizing the Invisible!)
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