| 1. |
- Petrov, O., et al.
(författare)
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Pore size distributions of biodegradable polymer microparticles in aqueous environments measured by NMR cryoporometry
- 2006
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 309:02-jan, s. 157-162
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Tidskriftsartikel (refereegranskat)abstract
- NMR cryoporometry is a unique method permitting the investigation of pores in the microporous and mesoporous regimes for samples in aqueous environments. Here, we apply the technique to porous biodegradable polymer microparticles designed as devices for drug delivery in depot formulations. The results indicate that structural features too small to be captured in surface and fracture images obtained by SEM are able to be accessed using the technique, and that the evolution of pore structure can be studied for several days as the particles swell and degrade in the aqueous environment.
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| 2. |
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| 3. |
- Badal Tejedor, Maria, et al.
(författare)
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Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure
- 2015
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 486:1-2, s. 315-323
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Tidskriftsartikel (refereegranskat)abstract
- Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.
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| 4. |
- Dahlberg, Carina, et al.
(författare)
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Polymer mobilization and drug release during tablet swelling. A 1H NMR and NMR microimaging study
- 2007
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 122, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to investigate the swelling characteristics of a hydroxypropyl methylcellulose (HPMC) matrix incorporating the hydrophilic drug antipyrine. We have used this matrix to introduce a novel analytical method, which allows us to obtain within one experimental setup information about the molecular processes of the polymer carrier and its impact on drug release. Nuclear magnetic resonance (NMR) imaging revealed in situ the swelling behavior of tablets when exposed to water. By using deuterated water, the spatial distribution and molecular dynamics of HPMC and their kinetics during swelling could be observed selectively. In parallel, NMR spectroscopy provided the concentration of the drug released into the aqueous phase. We find that both swelling and release are diffusion controlled. The ability of monitoring those two processes using the same experimental setup enables mapping their interconnection, which points on the importance and potential of this analytical technique for further application in other drug delivery forms.
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