| 1. |
- Chieng, Norman, et al.
(författare)
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Formation Kinetics and Stability of Carbamazepine−Nicotinamide Cocrystals Prepared by Mechanical Activation
- 2009
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Ingår i: Crystal Growth & Design. - : American Chemical Society. - 1528-7483 .- 1528-7505. ; 9:5, s. 2377-2386
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Tidskriftsartikel (refereegranskat)abstract
- Co-milling of various carbamazepine (CBZ) polymorphic forms (form I, III and dihydate) with nicotinamide (NIC) was performed in this study to investigate the formation kinetics of carbamazepine−nicotinamide cocrystals (CBZ−NIC) and to evaluate their physical stability. Milling was carried out at room temperature using an oscillatory ball mill at a 1:1 molar ratio of CBZ and NIC for various times up to 60 min. A freshly prepared sample was used for each milling. In the stability study, the milled samples (4, 10, 15, and 30 min) were stored under four conditions (20 and 40 °C; 33 and 75%RH) for up to four weeks. Samples were analyzed by X-ray powder diffraction (XRPD) and differential scanning calorimetry. XRPD showed that all CBZ forms used in this study formed cocrystals when co-milled with NIC (characteristic XRPD peaks at 6.6, 8.9, 10.1, 20.4, and 26.5 °2θ). Cocrystal formation was qualitatively found to be fastest for CBZ dihydrate (CBZ DH, ∼1 min), followed by CBZ form I (∼6 min), and CBZ form III (∼15 min). Upon storage, cocrystals formed from CBZ DH were found to be physically stable under all conditions studied, regardless of a small amount of impurity. For the two anhydrous forms (CBZ I and III), the physical stability of the co-milled CBZ−NIC samples was dependent on the duration of milling, the relative humidity, and temperature of the storage conditions. Under “mild” storage conditions (i.e., 20 °C/33%RH), either partially or fully formed CBZ−NIC cocrystals were found to revert back to pure CBZ and NIC. Under “moderate” storage conditions (i.e., 20 °C/75%RH and 40 °C/33%RH), CBZ−NIC cocrystals reverting to pure CBZ and NIC would occur initially, followed by cocrystal formation with increasing storage time. On the other hand, “stress” storage conditions (i.e., 40 °C/75%RH) were found to be ideal for cocrystal formation and stability. Moisture has been found to favor cocrystallization. Water molecules appear to have a significant effect on the formation (water molecules from CBZ DH) and the stability (high humidity) of the CBZ−NIC cocrystal. The “purity” of the cocrystal samples (i.e., presence of CBZ and/or NIC seeds) can affect the physical stability of CBZ−NIC cocrystals prepared by mechanical activation.
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| 2. |
- Craig, Alexander J., et al.
(författare)
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Antimicrobial Peptides Incorporating Halogenated Marine-Derived Amino Acid Substituents
- 2023
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Ingår i: ACS Medicinal Chemistry Letters. - : American Chemical Society (ACS). - 1948-5875. ; 14:6, s. 802-809
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Tidskriftsartikel (refereegranskat)abstract
- Small synthetic mimics of cationic antimicrobial peptides represent a promising class of compounds with leads in clinical development for the treatment of persistent microbial infections. The activity and selectivity of these compounds rely on a balance between hydrophobic and cationic components, and here, we explore the activity of 19 linear cationic tripeptides against five different pathogenic bacteria and fungi, including clinical isolates. The compounds incorporated modified hydrophobic amino acids inspired by motifs often found in bioactive marine secondary metabolites in combination with different cationic residues to probe the possibility of generating active compounds with improved safety profiles. Several of the compounds displayed high activity (low mu M concentrations), comparable with the positive controls AMC-109, amoxicillin, and amphotericin B. A higher activity was observed against the fungal strains, and a low in vitro off-target toxicity was observed against erythrocytes and HeLa cells, thereby illustrating effective means for tuning the activity and selectivity of short antimicrobial peptides.
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| 3. |
- Geh, Katharina J., et al.
(författare)
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Optimisation of one-step desolvation and scale-up of gelatine nanoparticle production
- 2016
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Ingår i: Journal of Microencapsulation. - : Taylor & Francis. - 0265-2048 .- 1464-5246. ; 33:7, s. 595-604
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Tidskriftsartikel (refereegranskat)abstract
- Gelatine nanoparticles (GNPs) are biodegradable and biocompatible drug delivery systems with excellent clinical performances. A two-step desolvation is commonly used for their preparation, although this methodology has several shortcomings: lack of reproducibility, small scales and low yields. A straightforward and more consistent GNP preparation approach is presented here focusing on the development of a one-step desolvation with the use of a commercially available gelatine type. Controlled stirring conditions and ultrafiltration are used to achieve large-scale production of nanoparticles of up to 2.6g per batch. Particle size distributions are conserved and comparable to those determined for two-step desolvation on small scale. Additionally, a range of cross-linking agents is examined for their effectiveness in stabilising GNPs as an alternative to glutaraldehyde. Glyceraldehyde demonstrated outstanding properties, which led to high colloidal stability. This approach optimises the manufacturing process and the scale-up of the production capacity, providing a clear potential for future applications.
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| 4. |
- Geh, Katharina J., et al.
(författare)
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Progress in formulation development and sterilisation of freeze-dried oligodeoxynucleotide-loaded gelatine nanoparticles
- 2018
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Ingår i: European journal of pharmaceutics and biopharmaceutics. - : Elsevier. - 0939-6411 .- 1873-3441. ; 129, s. 10-20
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Tidskriftsartikel (refereegranskat)abstract
- Oligodeoxynucleotide (ODN)-loaded gelatine nanoparticles (GNPs) have proven their outstanding potential in the treatment of allergic diseases such as equine asthma and canine atopic dermatitis, which are appropriate models for the corresponding human diseases. To encourage the development of a marketable product, long term stability and sterility needs to be ensured. In this work, we aimed to advance freeze-drying options to stabilise ODN-loaded GNPs. Matrix-assisted laser desorption/ionisation mass spectrometry time-of-flight was implemented as a versatile tool to assess ODN stability. With this method long-term storage stability of lyophilised ODN-loaded GNPs formulated in sucrose or trehalose was achieved. Controlled nucleation was further introduced to optimise the lyophilisation approach. This allowed shortening of the process in comparison to standard freeze-drying procedures. Particle sizes, polydispersity indices, ODN stability, residual moisture and glass transition temperature were maintained upon storage. Excipient portfolio was enlarged by novel amino acid containing formulations for lyophilisates. His emerged as an excellent excipient in stabilising lyophilised ODN-loaded GNPs, whereas addition of Arg and Gly revealed to be inadequate at accelerated conditions. Lastly, gamma irradiation was evaluated as a suitable sterilisation method of ODN-loaded GNPs.
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| 5. |
- Holst, Mikkel Roland, et al.
(författare)
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Clathrin-Independent Endocytosis Suppresses Cancer Cell Blebbing and Invasion
- 2017
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Ingår i: Cell Reports. - : Cell Press. - 2211-1247. ; 20:8, s. 1893-1905
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Tidskriftsartikel (refereegranskat)abstract
- Cellular blebbing, caused by local alterations in cellsurface tension, has been shown to increase the invasiveness of cancer cells. However, the regulatory mechanisms balancing cell-surface dynamics and bleb formation remain elusive. Here, we show that an acute reduction in cell volume activates clathrinindependent endocytosis. Hence, a decrease in surface tension is buffered by the internalization of the plasma membrane (PM) lipid bilayer. Membrane invagination and endocytosis are driven by the tension- mediated recruitment of the membrane sculpting and GTPase-activating protein GRAF1 (GTPase regulator associated with focal adhesion kinase-1) to the PM. Disruption of this regulation by depleting cells of GRAF1 or mutating key phosphatidylinositol- interacting amino acids in the protein results in increased cellular blebbing and promotes the 3D motility of cancer cells. Our data support a role for clathrin-independent endocytic machinery in balancing membrane tension, which clarifies the previously reported role of GRAF1 as a tumor suppressor.
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| 6. |
- Hubert, Madlen, et al.
(författare)
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Caveolae biogenesis and lipid sorting at the plasma membrane
- 2022
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Ingår i: Plasma membrane shaping. - : Academic Press. - 9780323899116 - 9780323899192 ; , s. 219-228
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Bokkapitel (refereegranskat)abstract
- The plasma membrane of many cell types, in particular, endothelia, smooth muscle cells, and adipocytes, contains numerous small invaginations termed caveolae. In nonmuscle cells, caveolae are formed by lipid-driven assembly of the integral membrane protein caveolin 1 (Cav1) and the peripherally attached protein cavin1. Accessory proteins such as Eps15 homology domain-containing 2 (EHD2) control the cell surface association of caveolae, together providing a unique invaginated membrane structure with distinct dynamics and protein and lipid compositions. These features enable caveolae to survey the plasma membrane integrity and to adjust membrane tension, and sort lipids according to the cellular requirements. Currently, characteristics of the protein and lipid interface of caveola are being unraveled, and this chapter is focused on the present knowledge of caveolae biogenesis and dynamics and describes methods that are being used to study the role of caveolae in lipid flux and lipid composition at the cell surface.
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| 7. |
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| 8. |
- Hubert, Madlen, et al.
(författare)
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Keeping in touch with the membrane; protein- and lipid-mediated confinement of caveolae to the cell surface
- 2020
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Ingår i: Biochemical Society Transactions. - : PORTLAND PRESS LTD. - 0300-5127 .- 1470-8752. ; 48, s. 155-163
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Forskningsöversikt (refereegranskat)abstract
- Caveolae are small Omega-shaped invaginations of the plasma membrane that play important roles in mechanosensing, lipid homeostasis and signaling. Their typical morphology is characterized by a membrane funnel connecting a spherical bulb to the membrane. Membrane funnels (commonly known as necks and pores) are frequently observed as transient states during fusion and fission of membrane vesicles in cells. However, caveolae display atypical dynamics where the membrane funnel can be stabilized over an extended period of time, resulting in cell surface constrained caveolae. In addition, caveolae are also known to undergo flattening as well as short-range cycles of fission and fusion with the membrane, requiring that the membrane funnel closes or opens up, respectively. This mini-review considers the transition between these different states and highlights the role of the protein and lipid components that have been identified to control the balance between surface association and release of caveolae.
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| 9. |
- Hubert, Madlen, et al.
(författare)
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Lipid accumulation controls the balance between surface connection and scission of caveolae.
- 2020
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Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Caveolae are bulb-shaped invaginations of the plasma membrane (PM) that undergo scission and fusion at the cell surface and are enriched in specific lipids. However, the influence of lipid composition on caveolae surface stability is not well described or understood. Accordingly, we inserted specific lipids into the cell PM via membrane fusion and studied their acute effects on caveolae dynamics. We demonstrate that sphingomyelin stabilizes caveolae to the cell surface, whereas cholesterol and glycosphingolipids drive caveolae scission from the PM. Although all three lipids accumulated specifically in caveolae, cholesterol and sphingomyelin were actively sequestered, whereas glycosphingolipids diffused freely. The ATPase EHD2 restricts lipid diffusion and counteracts lipid-induced scission. We propose that specific lipid accumulation in caveolae generates an intrinsically unstable domain prone to scission if not restrained by EHD2 at the caveolae neck. This work provides a mechanistic link between caveolae and their ability to sense the PM lipid composition.
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| 10. |
- Hubert, Madlen, et al.
(författare)
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Physical characterization of synthetic phosphatidylinositol dimannosides and analogues in binary systems with phosphatidylcholine.
- 2014
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Ingår i: Molecular Pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 11:3, s. 913-21
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Tidskriftsartikel (refereegranskat)abstract
- Native phosphatidylinositol mannosides (PIMs) from the cell wall of Mycobacterium bovis (M. bovis) and synthetic analogues have been identified to exert immunostimulatory activities. These activities have been investigated using particulate delivery systems containing native mannosylated lipids or total lipid extracts. Limited work has been carried out examining the incorporation of individual PIM lipids into suitable particulate formulations such as liposomes. The present study explored the possibility of constructing phosphatidylcholine (PC)-based liposomes containing synthetic PIM analogues. A series of six phosphatidylinositol dimannosides (PIM(2)s) and phosphatidylglycerol dimannosides (PGM(2)s) was characterized in this study. Binary Langmuir monolayers are a useful approach for establishing pharmaceutical properties, such as lipid-lipid interactions in mixed monolayers, to facilitate the design of liposome-based delivery systems. In mixed films the phosphoglycolipids were found to be miscible with PC based on evaluation of collapse pressures and deviations of experimental molecular areas from calculated ideal values. Concanavalin A (ConA) agglutination confirmed the presence of mannosylated lipids on the surface of the liposomes. Physicochemical properties of liposomes were affected by the presence of 2% (w/w) of phosphoglycolipids with liposome stability being increased by incorporation of long-chain PIM(2) and PGM2. Overall, while membrane stability of the liposomes was found to be dependent on incorporation of the phosphoglycolipids, all formulations retained proteins in amounts making them suitable for delivery.
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