| 1. |
- Haberska, Karolina, et al.
(författare)
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Activity of lactoperoxidase when adsorbed on protein layers
- 2008
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Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 76:5, s. 1159-1164
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Tidskriftsartikel (refereegranskat)abstract
- Lactoperoxidase (LPO) is an enzyme, which is used as an antimicrobial agent in a number of applications, e.g., food technology. In the majority of applications LPO is added to a homogeneous product phase or immobilised on product surface. In the latter case, however, the measurements of LPO activity are seldom reported. In this paper we have assessed LPO enzymatic activity on bare and protein modified gold surfaces by means of electrochemistry. It was found that LPO rapidly adsorbs to bare gold surfaces resulting in an amount of LPO adsorbed of 2.9 mg/m2. A lower amount of adsorbed LPO is obtained if the gold surface is exposed to bovine serum albumin, bovine or human mucin prior to LPO adsorption. The enzymatic activity of the adsorbed enzyme is in general preserved at the experimental conditions and varies only moderately when comparing bare gold and gold surface pretreated with the selected proteins. The measurement of LPO specific activity, however, indicate that it is about 1.5 times higher if LPO is adsorbed on gold surfaces containing a small amount of preadsorbed mucin in comparison to the LPO directly adsorbed on bare gold.
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| 2. |
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| 3. |
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| 4. |
- Lindh, Liselott, et al.
(författare)
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The salivary mucin MUC5B and lactoperoxidase can be used for layer-by-layer film formation
- 2007
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Ingår i: Journal of Colloid Interface Science. - : Elsevier BV. - 0021-9797. ; 310:1, s. 74-82
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Tidskriftsartikel (refereegranskat)abstract
- Abstract In situ ellipsometry was used to study layer-by-layer film formation on hydrophilic and hydrophobized silica surfaces by alternating sequential adsorption of human mucin MUC5B and cationic proteins lysozyme, lactoferrin, lactoperoxidase or histatin 5, respectively. The stability of the multilayers was investigated by addition of sodium dodecyl sulfate solution (SDS). Atomic force microscopy was employed to investigate morphological structures on the surfaces during the layer-by-layer film build-up. It was clearly shown that, on both hydrophilic and hydrophobized silica, only MUC5B and lactoperoxidase showed the ability for multilayer formation, resulting in an approximately linear increase in adsorbed amount and film thickness with each deposition cycle. The net increase in amounts per cycle was larger on the hydrophilic silica. Further, MUC5B needs to be adsorbed first on the hydrophilic substrates to obtain this fast build-up behavior. Generally, addition of SDS solution showed that a large fraction of the adsorbed film could be desorbed. However, films on the hydrophobized silica were more resistant to surfactant elution. In conclusion, MUC5B–cationic protein multilayers can be formed on hydrophilic and hydrophobized silica, depending on the choice of the cationic protein as well as in which order the build-up is started on hydrophilic silica. Additionally, SDS disrupts the layer-by-layer film formed by MUC5B and lactoperoxidase.
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| 5. |
- Svensson, Olof, et al.
(författare)
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Interactions between chitosan-modified particles and mucin-coated surfaces
- 2008
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier Inc.. - 0021-9797 .- 1095-7103. ; 2:325, s. 346-350
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Tidskriftsartikel (refereegranskat)abstract
- Lipid-based particles (Cubosome® particles) were surface-modified by chitosan and the ratio between particles and chitosan was optimized to minimize the free chitosan concentration in the dispersion. The modified particles were characterized by electrophoretic measurements and the pH dependence of the zeta potential could be directly related to the protonation of chitosan. Interaction between the modified particles and mucin-coated silica surfaces were subsequently investigated in situ by ellipsometry to assess the mucoadhesive properties at physiologically relevant conditions. The result showed that a substantial amount of modified particles was adsorbed to mucin-coated silica surfaces at both pH 4 and pH 6, probably due to electrostatic interactions between amino groups in chitosan and negatively charged groups in mucin. Furthermore, the amount of bound particles decreased by less than 15% upon rinsing indicating relatively strong interactions. This investigation demonstrates that ellipsometry is a useful tool to study mucoadhesive properties of particles in the submicrometer range. Moreover, the novel chitosan-modified particles may be of interest for mucosal drug delivery applications.
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| 6. |
- Svensson, Olof, et al.
(författare)
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Interactions between Drug Delivery Particles and Mucin in Solution and at Interfaces
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24, s. 2573-2579
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Tidskriftsartikel (refereegranskat)abstract
- Cubosome particles were produced by fragmenting a cubic crystalline phase of glycerol monooleate and water in the presence of a stabilizing poly(ethylene oxide)-based polymer. The aim of our investigation was to study the interaction between these particles and mucin to gain information on how they would perform as a vehicle for mucosal drug delivery. Particle electrophoresis was used to investigate the interactions between particles and mucin in solution, and ellipsometry was utilized to study the interactions between particles and mucin-coated silica surfaces. The interaction studies were performed at relevant physiological conditions, and the pH and ionic strength were varied to gain more information about the driving forces for the interaction. The results from electrophoretic measurements showed that mucin in solution adsorbed to the particles at pH 4, whereas at pH 6 no clear interaction was detected. From ellipsometric measurements it was evident that the particles adsorb reversibly to a mucin-coated silica surface at pH 4, while no adsorption of particles could be detected at pH 6. The overall conclusion is that the interaction between these particles and mucin is weak and pH-dependent. These findings are in agreement with other investigations of the interactions between mucin and poly(ethylene oxide) chains.
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| 7. |
- Svensson, Olof
(författare)
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Interactions of Mucins with Biopolymers and Drug Delivery Particles
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main components in the mucous gels apart from water are mucins, which are proteins with high molecular weights and an abundance of negatively charged oligosaccharide side chains. The aim of the investigations was to characterize interactions between mucins and other proteins that are present in the mucous gel, and also between mucins and components used in pharmaceutical formulations. More specifically, the main objectives were (I) to investigate the possibility to assemble multilayer films with mucins and oppositely charged polymers or proteins on solid substrates; (II) to evaluate mucoadhesive proper-ties of drug delivery particles by examination of their interactions with mucins. The construction of multilayer films was performed on silica and hydrophobized silica surfaces by alternate adsorption, and the adsorbed amount and thickness of the films were measured in situ by time resolved ellipsometry. It was demonstrated that films could be assembled using mucins in combination with both chitosan and lactoperoxidase. The build-up was characterized by adsorption and redissolution processes, and the extent of redissolution could be explained by taking the charge densities and concentrations of the components into account. It was also demonstrated that the nature of the substrate can be crucial for the possibilities to assemble multilayer films, and from the results it may be concluded that a high amount of mucin in the first step is important for successful layer-by-layer assembly. Furthermore, it was demonstrated that lactoperoxidase is catalytically active when adsorbed to mucin layers, and it may thereby exert its antimicrobial action. The evaluation of mucoadhesive properties of drug delivery particles was performed with lipid nanoparticles stabilized by a poly(ethylene oxide) based polymer and with particles modified by chitosan. Both types of model particles (unmodified and chitosan modified) were investigated by measuring their adsorption to mucin-coated silica surfaces by ellipsometry. It was shown that the binding of unmodified particles to mucin-coated silica surfaces was weak and pH-dependent. Based on the pH and electrolyte dependence of the adsorption, it was proposed that the interaction is mediated by hydrogen bonding between protonated carboxyl groups in the mucin molecule and oxygen atoms in poly(ethylene oxide). Chitosan modified particles, on the other hand, showed a substantial and strong binding to mucin-coated surfaces, which can probably be attributed to interactions between amino groups in chitosan and negatively charged groups in the mucin layer. The findings from the present investigations are in agreement with previous reports on the interaction of mucins with poly(ethylene oxide) and chitosan. It can therefore be concluded that the methodology applied is useful for evaluating mucoadhesive properties of nanoparticles.
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| 8. |
- Svensson, Olof, et al.
(författare)
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Layer-by-layer assembly of mucin and chitosan - Influence of surface properties, concentration and type of mucin
- 2006
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Ingår i: Journal of Colloid and Interface Science. - : Academic Press. - 0021-9797 .- 1095-7103. ; 299:2, s. 608-616
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Tidskriftsartikel (refereegranskat)abstract
- Bovine submaxillary mucin (BSM) and chitosan were used to build layer-by-layer structures on solid substrates. The build-up was monitored using in situ ellipsometry to obtain time resolved values of the thickness and adsorbed amount. Additionally surface morphology during build-up was studied by atomic force microscopy (AFM). It was found that the adsorbed amount of the film increases approximately linearly with each deposition cycle on hydrophobized silica whereas construction on silica was found not to be possible at the experimental conditions used. We conclude that sufficient amount of the first mucin layer is crucial for the subsequent multilayer formation. The complex build-up kinetics on hydrophobized silica is characterized by adsorption and redissolution processes and the overall growth is the sum of both processes. AFM imaging on hydrophobized silica also confirmed the presence of redissolution processes and chitosan addition led to a reduction both in the number of surface aggregates and in the roughness of the surface. The present work also shows that by adjusting the relative concentrations of the polyelectrolytes it is possible to change the growth rate considerably. The final structures after deposition of 8 bilayers were found to have a high content of water and film stability test revealed that a substantial amount dissolves when increasing electrolyte concentration or pH of the ambient solution. Human mucin from saliva (MUC5B) was also used to create multilayers with chitosan on hydrophobized silica and it was revealed that no redissolution appears to be present in this system.
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| 9. |
- Wikström, Per-Olof, et al.
(författare)
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Why are English youths more violent than Swedish youths? A comparative study of the role of crime propensity, lifestyles and their interactions in two cities
- 2008
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Ingår i: European Journal of Criminology. - : SAGE Publications. - 1477-3708 .- 1741-2609. ; 5:3, s. 309-330
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Tidskriftsartikel (refereegranskat)abstract
- Most cross-national studies of crime and violence explore variation in levels of crime without empirically addressing the causes of these variations. Drawing upon the theoretical framework of the situational action theory of crime causation (e.g. Wikström 2006), in this study we aim to explore and test whether the difference in levels of violence among young people in England and Sweden can be explained (fully or partly) by country differences in young people's crime propensities and lifestyles and their interaction. To achieve this we use data from the English Peterborough Youth Study and the Swedish Eskilstuna Youth Study. The findings show that in both cities (1) young people's self-reported violent behaviour is predicted by crime propensity and lifestyle, and their interaction, and (2) a substantial proportion (40 percent) of the difference in the level of violence vanishes when taking into account national differences in young people's crime propensity and lifestyles. We conclude that the findings support the notion that one major cause of the difference in the level of violence among young people in England and Sweden is that more young people in England have a higher crime propensity and are living criminogenic lifestyles than in Sweden.
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