| 1. |
- Westas, Emma, 1982, et al.
(författare)
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Bactericidal effect of photocatalytically-active nanostructured TiO2 surfaces on biofilms of the early oral colonizer, Streptococcus oralis
- 2017
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 105:8, s. 2321-2328
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the photocatalytic bactericidal effect of nanostructured anatase-rich titanium dioxide (TiO2) on microbial biofilms. Commercially pure titanium discs were spin-coated with photocatalytic TiO2 nanoparticles (P25). Uncoated discs were used as control (CTRL). Half of the CTRL and half of the P25-coated surfaces were coated with purified saliva (SAL) to give four different groups (CTRL, CTRL + SAL, P25 and P25 + SAL). Streptococcus oralis were allowed to form biofilms on the discs for 18 h and non-adherent cells were rinsed off. Bacterial viability was assessed at time 0 with Live/Dead BacLight staining and epifluorescence microscopy. The remaining discs were divided into a non-UV group and UVA-irradiated (1UV) group (irradiation time, 6 or 24 h). Thereafter, viability was assessed as above. Viability at time 0 was high and no dead cells were seen on any of the surfaces, even after 24 h, in the absence of UVA. However, after 24 h of exposure, the proportion of viable cells was reduced by 40% on the P25 discs compared to 0 and 6 h, and this effect was enhanced with a salivary pellicle. Members of mixed species biofilms differ in their susceptibility to the bactericidal effect of the surfaces tested and further investigations are needed to optimize the conditions.
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| 2. |
- Westas, Emma, 1982, et al.
(författare)
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Biofilm formation on nanostructured hydroxyapatite-coated titanium
- 2014
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 102:4, s. 1063-1070
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Tidskriftsartikel (refereegranskat)abstract
- Biofilm formation on medical devices is a common cause of implant failure, especially regarding implants that breach the epithelial tissue, so-called transcutaneous implants. Nanotechnology and the development of new nanomaterials have given the opportunity to design nanotextured implant surfaces. Such surfaces have been studied using various in vitro methods showing that nanosized features strongly benefit bone cell growth. However, little is known on how nanostructured features affect biofilm formation. The aim of this study was therefore to examine the shape- and chemical-dependent effect of a nanostructured hydroxyapatite (HA) coating on the degree of Staphylococcus epidermidis biofilm formation. Three different types of nanosized HA particles having different shapes and calcium to phosphate ratios were compared to uncoated turned titanium using safranin stain in a biofilm assay and confocal laser scanning microscopy (CLSM) for assessment of biofilm biomass and bacterial volume, respectively. No difference in biofilm biomass was detected for the various surfaces after 6 h incubation with S. epidermidis. Additionally, image analysis of CLSM Z-stacks confirmed the biofilm assay and showed similar results. In conclusion, the difference in nanomorphology and chemical composition of the surface coatings did not influence the adhesion and biofilm formation of S. epidermidis.
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| 3. |
- Westas, Emma, 1982, et al.
(författare)
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Curvature-dependent effects of nanotopography on classical immune complement activation
- 2018
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 74, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate how the size of nanosized surface features affect classical immune complement activation through adsorption of IgG and the following binding of C1q. By using model surfaces with immobilized SiO2nanoparticles of different sizes (8, 32 and 68 nm in diameter), three different curvatures with the same chemistry was systematically studied and analyzed using the acoustic sensing technique; Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). Circular Dichroism (CD) was employed to study any changes in the secondary structure of IgG using a methodology with stacked functionalized substrates. Our results show that the amount of IgG adsorption increased slightly with nanoparticle size, but also showed a strong size/curvature-dependent effect on the following C1q binding, with the highest binding to IgG adsorbed on the largest nanoparticles and a smooth control surface, indicating that classical immune complement activation possibly increase with decreasing curvature. We conclude that the difference in C1q binding was not due to changes in the secondary structure of IgG, suggesting that geometrical arrangement of adsorbed IgG is the determining factor. Statement of Significance: We have shown that small changes at the topographical nanoscale can give large effects on the initiation of the classical immune complement cascade, an important immunological reaction that take place when a foreign material is inserted in the body. By developing a methodology using silicon dioxide nanoparticles with three different sizes, to systematically study their impact on the secondary structure and binding of human immunoglobulin G (IgG) to the initiator protein C1q of the classical complement cascade, we have shown that the initiation of the classical immune complement is hampered by the sharp curvature of the smaller nanoparticles. We conclude that this is not mediated by changes in the secondary structure of the adsorbed proteins, but rather an effect of curvature-induced spatial mismatch. The results provide a possible mechanistic explanation on how nanotopography may effect protein adsorption and protein cascade events.
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| 4. |
- Westas, Emma, 1982
(författare)
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Protein and Cell Interactions with Nanostructured Surfaces
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A great challenge of today’s implant development is to construct a surface that promotes tissue integration and avoids bacterial colonization. To avoid implant related infections, many argue that a surface promoting strong cell adhesion and tissue integration in favour for bacterial adhesion would solve the problem, the so-called race for the surface concept. However, important factors for tissue integration, such as roughness and surface chemistry, also affect the adhesion of bacteria and many surface features promoting tissue integration have been found to promote biofilm formation. Nanotechnology and the development of nanomaterials have resulted in the opportunity to design tailor made nanostructured implants with novel topographical and chemical surface properties. Such surface features have demonstrated its effect on protein adsorption, cellular interactions, tissue integration and bacterial accumulation. The development of using nanomaterials in medical device applications has only just begun and there is a large need for fundamental studies on the biological response to nanostructured biomaterials. The main objective of this thesis was to use nanoparticles to modify implant surfaces and study its effect on biomolecules, human cells, bacteria and immune reactions. More specifically, we wanted to investigate if surface modifications created by introducing nanotopography, favourable chemical species and crystal structure using different nanoparticles would alter the surface properties and subsequent impact on protein adsorption, human cell attachment and bacteria. In order to achieve these objectives, nanostructured surfaces were constructed using hydroxyapatite, titanium dioxide and silica nanoparticles with the use of three different approaches for immobilizing the nanoparticles onto the underlying substrate. Hydroxyapatite (HA) nanoparticles were applied to titanium substrates by spin coating, titanium dioxide nanoparticles were attached to titanium substrates using an alkoxide thin film as adhesive and silica nanoparticles were immobilized on silica substrates using self-assembly strategies and electrostatic interactions. The surfaces were characterized using various analytical techniques, such as SEM, AFM and XPS etc. It was found that HA nanoparticles applied on titanium substrates did not affect the attachment and spreading of fibroblasts compared to uncoated titanium. Additionally, HA nanoparticles of different shapes and chemistry, coated onto titanium discs, did not increase Staphylococcus epidermidis biofilm formation compared to uncoated titanium. The developed TiO2 nanoparticle coating was photocatalytically active and found to elicit bactericidal properties upon UV irradiation. Studying the effect of silica nanoparticle curvature on immune complement activating proteins, it was found that smaller nanoparticles/high curvature significantly reduced the binding of complement protein C1q. Additionally, NMR was used to study the adsorption of human serum metabolites onto silica nanoparticles of various sizes and surprisingly, a curvature-dependent effect on the adsorption of several small metabolic molecules was found.
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| 5. |
- Westas, Emma, 1982, et al.
(författare)
-
Using QCM-D to study the adhesion of human gingival fibroblasts on implant surfaces
- 2015
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 103:10, s. 3139-3147
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Tidskriftsartikel (refereegranskat)abstract
- Sealing the soft tissue-implant interface is one of the key issues in preventing transcutaneous implant-associated infections. A promising surface modification for improving osseointegration and possibly soft tissue integration is to coat the implant surface with hydroxyapatite (HA) nanoparticles. When new implant materials are developed, their ability to facilitate cell attachment and spreading are commonly investigated in vitro to establish their potential for good in vivo performance. However, commonly used techniques, such as microscopy methods, are time consuming, invasive, and subjective. This is the first study using quartz crystal microbalance with dissipation monitoring, where the real-time adhesion of biopsy-derived human gingival fibroblasts onto titanium and nanostructured HA was investigated. Experiments were performed for at least 16 h, and we found that cellular attachment and spreading kinetics can be followed in situ by observing the change in dissipation and frequency with time. Interestingly, a correlation between cell coverage and the magnitude of dissipation shift reached at the end of the experiment was found, but no such trend was observed for the frequency. Furthermore, the level of cell coverage was found to influence the cellular attachment and spreading behavior. No difference in cell response to the two surface types, Ti and nanostructured HA, was found.
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