| 1. |
- Arvidsson, Martin, et al.
(author)
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Feeling fine – the effect of topography and friction on perceived roughness and slipperiness
- 2016
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Other publication (other academic/artistic)abstract
- To be able to design materials with specific haptic qualities, it is important to understand not only the contribution of physical attributes from the surfaces of the materials, but also the perceptions that are involved in the haptic interaction with the materials. A series of 16 wrinkled surfaces with two different materials (Young’s modulus of 1,600 and 20,000 psi, respectively) and 8 different wrinkle wavelengths (30‑120 µm, and two unwrinkled reference surfaces) were thus characterized in terms of surface roughness and finger friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using the method of free magnitude estimation. Five of the sixteen participants conducted friction measurements during their perceived slipperiness session, and an experimenter conducted friction measurements in a separate experiment with higher experimental control. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 µm and roughness above 100 µm. In the interval between 30 and 50 µm it is hard to discriminate between the wavelengths, these surfaces also exhibit the highest slipperiness and the lowest roughness. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent; which is also supported by an increased friction between 80‑100 µm that corresponds well with both a change in slipperiness and in roughness. The increased friction in this specific wavelength region is related to an increased contact area between finger and material. Somewhat surprising was the fact that the material with the higher Young’s modulus was perceived as more slippery, especially for the smaller wavelengths, this is also the range where it was difficult to differentiate between the wavelengths. A concluding finding was that the flat (high friction) references surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.
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| 2. |
- Boge, Lukas, 1987, et al.
(author)
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Cubosomes for topical delivery of the antimicrobial peptide LL-37
- 2019
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In: European Journal of Pharmaceutics and Biopharmaceutics. - : Elsevier BV. - 1873-3441 .- 0939-6411. ; 134, s. 60-67
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Journal article (peer-reviewed)abstract
- In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.
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| 3. |
- Boge, Lukas, 1987, et al.
(author)
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Cubosomes post-loaded with antimicrobial peptides: Characterization, bactericidal effect and proteolytic stability
- 2017
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In: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 526:1-2, s. 400-412
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Journal article (peer-reviewed)abstract
- Novel antibiotics, such as antimicrobial peptides (AMPs), have recently attended more and more attraction. In this work, dispersed cubic liquid crystalline gel (cubosomes) was used as drug delivery vehicles for three AMPs (AP114, DPK-060 and LL-37). Association of peptides onto cubosomes was studied at two cubosome/peptide ratios using high performance liquid chromatography, ?-potential and circular dichroism measurements. AMPs impact on the cubosome structure was investigated using small angle x-ray scattering and cryogenic transmission electron microscopy. The antimicrobial effect of the AMP loaded cubosomes was studied in vitro by minimum inhibitory concentration and time-kill assays. Proteolytic protection was investigated by incubating the formulations with two elastases and the antimicrobial effect after proteolysis was studied using radial diffusion assay. Different association efficacy onto the cubosomes was observed among the AMPs, with LL-37 showing greatest association (>60%). AP114 loaded cubosomes displayed a preserved antimicrobial effect, whereas for LL-37 the broad spectrum bacterial killing was reduced to only comprise Gram-negative bacteria. Interestingly, DPK-060 loaded cubosomes showed a slight enhanced effect against S. aureus and E. coli strains. Moreover, the cubosomes were found to protect LL-37 from proteolytic degradation, resulting in a significantly better bactericidal effect after being subjected to elastase, compared to unformulated peptide.
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| 4. |
- Boge, Lukas, et al.
(author)
-
Cubosomes for topical delivery of the antimicrobial peptide LL-37
- 2019
-
In: European journal of pharmaceutics and biopharmaceutics. - : Elsevier BV. - 0939-6411 .- 1873-3441. ; 134, s. 60-67
-
Journal article (peer-reviewed)abstract
- In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.
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| 5. |
- Boge, Lukas, et al.
(author)
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Lipid-based liquid crystals as carriers for antimicrobial peptides : Phase behavior and antimicrobial effect
- 2016
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:17, s. 4217-4228
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Journal article (peer-reviewed)abstract
- The number of antibiotic-resistant bacteria is increasing worldwide, and the demand for novel antimicrobials is constantly growing. Antimicrobial peptides (AMPs) could be an important part of future treatment strategies of various bacterial infection diseases. However, AMPs have relatively low stability, because of proteolytic and chemical degradation. As a consequence, carrier systems protecting the AMPs are greatly needed, to achieve efficient treatments. In addition, the carrier system also must administrate the peptide in a controlled manner to match the therapeutic dose window. In this work, lyotropic liquid crystalline (LC) structures consisting of cubic glycerol monooleate/water and hexagonal glycerol monooleate/oleic acid/water have been examined as carriers for AMPs. These LC structures have the capability of solubilizing both hydrophilic and hydrophobic substances, as well as being biocompatible and biodegradable. Both bulk gels and discrete dispersed structures (i.e., cubosomes and hexosomes) have been studied. Three AMPs have been investigated with respect to phase stability of the LC structures and antimicrobial effect: AP114, DPK-060, and LL-37. Characterization of the LC structures was performed using small-angle X-ray scattering (SAXS), dynamic light scattering, ζ-potential, and cryogenic transmission electron microscopy (Cryo-TEM) and peptide loading efficacy by ultra performance liquid chromatography. The antimicrobial effect of the LCNPs was investigated in vitro using minimum inhibitory concentration (MIC) and time-kill assay. The most hydrophobic peptide (AP114) was shown to induce an increase in negative curvature of the cubic LC system. The most polar peptide (DPK-060) induced a decrease in negative curvature while LL-37 did not change the LC phase at all. The hexagonal LC phase was not affected by any of the AMPs. Moreover, cubosomes loaded with peptides AP114 and DPK-060 showed preserved antimicrobial activity, whereas particles loaded with peptide LL-37 displayed a loss in its broad-spectrum bactericidal properties. AMP-loaded hexosomes showed a reduction in antimicrobial activity.
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| 6. |
- Boge, Lukas
(author)
-
Lipid-based liquid crystals as drug delivery vehicles for antimicrobial peptides
- 2018
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Doctoral thesis (other academic/artistic)abstract
- The development of antimicrobial resistance is a great challenge within health sectors worldwide. Thus, demand for new, efficient treatments is urgent in order to treat various bacterial infections. Antimicrobial peptides (AMPs) are a group of antibiotics that have gained more and more attraction in the past decade. AMPs suffer from relatively low stability due to proteolytic and chemical degradation. As a consequence, carrier systems to protect the AMPs are highly needed to achieve efficient treatments in the clinic. In this thesis, lipid-based liquid crystalline (LC) structures have been examined as carriers for AMPs. LC structures of polar lipids have potential to be used as carriers and delivery systems in various pharmaceutical applications. This is due to their ability to solubilize and encapsulate hydrophilic, hydrophobic and amphiphilic substances. An important feature of these LC systems is that they can coexist with an excess of water, which enables fragmentation of the highly viscous gels into LC nanoparticles (LCNPs), i.e. cubosomes and hexosomes, in the presence of a suitable stabilizer. Peptides and proteins can be incorporated into the lipid self-assembled structures, thereby protecting them from chemical and proteolytic degradation. Cubosomes and hexosomes were investigated as drug delivery vehicles for the three AMPs: i) AP114, an improved plectasin derivative originating from the fungus Pseudoplectania nigrella, ii) DPK-060, derived from the endogenous human protein kininogen and iii) LL-37, a human AMP found in the cathelicidin family. Phase behavior, different preparation methodologies of the LCNPs, antimicrobial effect and proteolytic protection of the AMPs were studied. Moreover, the interaction between AMP-loaded particles with bacteria and bacterial mimicking membranes was investigated. Formulations aimed for pulmonary and topical administration were also evaluated. Results showed that cubic LC phases were most sensitive to the incorporation of AMPs. Depending on the nature of the AMP, different changes in the curvature of the systems were observed. Cubosomes loaded with AMPs exhibited good antimicrobial activity and were found to protect the proteolytic sensitive LL-37 from enzymatic degradation. Data strongly suggested that the release of AMP from the particles cannot solely be explained by the antimicrobial effect. Cubosomes loaded with LL-37 are thought to adsorb onto bacterial membranes, resulting in cell death.
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| 7. |
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| 8. |
- Boge, Lukas, et al.
(author)
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Peptide-Loaded Cubosomes Functioning as an Antimicrobial Unit against Escherichia coli
- 2019
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In: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 11:24, s. 21314-21322
-
Journal article (peer-reviewed)abstract
- Dispersions of cubic liquid crystalline phases, also known as cubosomes, have shown great promise as delivery vehicles for a wide range of medicines. Due to their ordered structure, comprising alternating hydrophilic and hydrophobic domains, cubosomes possess unique delivery properties and compatibility with both water-soluble and -insoluble drugs. However, the drug delivery mechanism and cubosome interaction with human cells and bacteria are still poorly understood. Herein, we reveal how cubosomes loaded with the human cathelicidin antimicrobial peptide LL-37, a system with high bacteria-killing effect, interact with the bacterial membrane and provide new insights into the eradication mechanism. Combining the advanced experimental techniques neutron reflectivity and quartz crystal microbalance with dissipation monitoring, a mechanistic drug delivery model for LL-37-loaded cubosomes on bacterial mimicking bilayers was constructed. Moreover, the cubosome interaction with Escherichia coli was directly visualized using super-resolution laser scanning microscopy and cryogenic electron tomography. We could conclude that cubosomes loaded with LL-37 adsorbed and distorted bacterial membranes, providing evidence that the peptide-loaded cubosomes function as an antimicrobial unit.
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| 9. |
- Håkansson, Joakim, et al.
(author)
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Characterization of the in vitro, ex vivo, and in vivo Efficacy of the Antimicrobial Peptide DPK-060 Used for Topical Treatment
- 2019
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In: Frontiers in Cellular and Infection Microbiology. - : Frontiers Media SA. - 2235-2988. ; 9
-
Journal article (peer-reviewed)abstract
- Antimicrobial peptides, also known as host defense peptides, have recently emerged as a promising new category of therapeutic agents for the treatment of infectious diseases. This study evaluated the preclinical in vitro, ex vivo, and in vivo antimicrobial activity, as well as the potential to cause skin irritation, of human kininogen-derived antimicrobial peptide DPK-060 in different formulations designed for topical delivery. We found that DPK-060 formulated in acetate buffer or poloxamer gel caused a marked reduction of bacterial counts of Staphylococcus aureus in vitro (minimum microbicidal concentration <5 μg/ml). We also found that DPK-060 in poloxamer gel significantly suppressed microbial survival in an ex vivo wound infection model using pig skin and in an in vivo mouse model of surgical site infection (≥99 or ≥94% reduction in bacterial counts was achieved with 1% DPK-060 at 4 h post-treatment, respectively). Encapsulation of DPK-060 in different types of lipid nanocapsules or cubosomes did not improve the bactericidal potential of the peptide under the applied test conditions. No reduction in cell viability was observed in response to administration of DPK-060 in any of the formulations tested. In conclusion, the present study confirms that DPK-060 has the potential to be an effective and safe drug candidate for the topical treatment of microbial infections; however, adsorption of the peptide to nanocarriers failed to show any additional benefits.
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| 10. |
- Lindholm-Sethson, Britta, et al.
(author)
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Electrochemical impedance spectroscopy in label-free biosensor applications : multivariate data analysis for an objective interpretation
- 2010
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 398:6, s. 2341-2349
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Research review (peer-reviewed)abstract
- Electrochemical impedance spectroscopy plays an important role in biosensor science thanks to the possibility of finding specific information from processes with different kinetics at a chosen electrode potential in one experiment. In this paper we briefly discuss label-free impedimetric biosensors described in the literature. A novel method for neutral interpretation of impedance data is presented that includes complex number chemometrics. Three examples are given based on impedance measurements on synthetic biomembranes, in this case a lipid monolayer deposited on a mercury electrode. The interaction of various compounds with the monomolecular lipid layer is illustrated with the following: (1) different concentrations of magainin (Geladi et al. in Proc. Int. Fed. Med. Biomed. Eng. 9:219-220, 2005); (2) different derivatives of gramicidin A (Lindholm-Sethson et al. in Langmuir 24:5029-5032, 2007), and (3) an antimicrobial peptide (Ringstad et al. in Langmuir 24:208-216, 2008).
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