| 1. |
- Huttu, Mari, et al.
(författare)
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Effects of medium and temperature on cellular responses in the superficial zone of hypo-osmotically challenged articular cartilage.
- 2012
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Ingår i: Journal of Functional Biomaterials. - Basel, Switzerland : MDPI AG. - 2079-4983. ; 3:3, s. 544-555
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Tidskriftsartikel (refereegranskat)abstract
- Osmotic loading of articular cartilage has been used to study cell-tissue interactions and mechanisms in chondrocyte volume regulation in situ. Since cell volume changes are likely to affect cell's mechanotransduction, it is important to understand how environmental factors, such as composition of the immersion medium and temperature affect cell volume changes in situ in osmotically challenged articular cartilage. In this study, chondrocytes were imaged in situ with a confocal laser scanning microscope (CLSM) through cartilage surface before and 3 min and 120 min after a hypo-osmotic challenge. Samples were measured either in phosphate buffered saline (PBS, without glucose and Ca(2+)) or in Dulbecco's modified Eagle's medium (DMEM, with glucose and Ca(2+)), and at 21 °C or at 37 °C. In all groups, cell volumes increased shortly after the hypotonic challenge and then recovered back to the original volumes. At both observation time points, cell volume changes as a result of the osmotic challenge were similar in PBS and DMEM in both temperatures. Our results indicate that the initial chondrocyte swelling and volume recovery as a result of the hypo-osmotic challenge of cartilage are not dependent on commonly used immersion media or temperature.
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| 2. |
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| 3. |
- Kulmala, Katariina, et al.
(författare)
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Diffusion of ionic and non-ionic contrast agents in articular cartilage with increased cross-linking : contribution of steric and electrostatic effects
- 2013
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Ingår i: Medical Engineering and Physics. - : Elsevier. - 1350-4533 .- 1873-4030. ; 35:10, s. 1415-20
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the effect of threose-induced collagen cross-linking on diffusion of ionic and non-ionic contrast agents in articular cartilage.DESIGN: Osteochondral plugs (Ø=6mm) were prepared from bovine patellae and divided into two groups according to the contrast agent to be used in contrast enhanced computed tomography (CECT) imaging: (I) anionic ioxaglate and (II) non-ionic iodixanol. The groups I and II contained 7 and 6 sample pairs, respectively. One of the paired samples served as a reference while the other was treated with threose to induce collagen cross-linking. The equilibrium partitioning of the contrast agents was imaged after 24h of immersion. Fixed charge density (FCD), water content, contents of proteoglycans, total collagen, hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent) cross-links were determined as a reference.RESULTS: The equilibrium partitioning of ioxaglate (group I) was significantly (p=0.018) lower (-23.4%) in threose-treated than control samples while the equilibrium partitioning of iodixanol (group II) was unaffected by the threose-treatment. FCD in the middle and deep zones of the cartilage (p<0.05) and contents of Pent and LP (p=0.001) increased significantly due to the treatment. However, the proteoglycan concentration was not systematically altered after the treatment. Water content was significantly (-3.5%, p=0.007) lower after the treatment.CONCLUSIONS: Since non-ionic iodixanol showed no changes in partition after cross-linking, in contrast to anionic ioxaglate, we conclude that the cross-linking induced changes in charge distribution have greater effect on diffusion compared to the cross-linking induced changes in steric hindrance.
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| 4. |
- Myllymaa, Katja, et al.
(författare)
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Improved adherence and spreading of Saos-2 cells on polypropylene surfaces achieved by surface texturing and carbon nitride coating.
- 2009
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Ingår i: Journal of materials science. Materials in medicine. - : Springer. - 0957-4530 .- 1573-4838. ; 20:11, s. 2337-2347
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Tidskriftsartikel (refereegranskat)abstract
- The adhesion and contact guidance of human primary osteogenic sarcoma cells (Saos-2) were characterized on smooth, microstructured (MST) and micro- and nano-structured (MNST) polypropylene (PP) and on the same samples with a silicon-doped carbon nitride (C(3)N(4)-Si) coating. Injection molding was used to pattern the PP surfaces and the coating was obtained by using ultra-short pulsed laser deposition (USPLD). Surfaces were characterized using atomic force microscopy and surface energy components were calculated according to the Owens-Wendt model. The results showed C(3)N(4)-Si coated surfaces to be significantly more hydrophilic than uncoated ones. In addition, there were 86% more cells in the smooth C(3)N(4)-Si coated PP compared to smooth uncoated PP and 551%/476% more cells with MST/MNST C(3)N(4)-Si coated PP than could be obtained with MST/MNST uncoated PP. Thus the adhesion, spreading and contact guidance of osteoblast-like cells was effectively improved by combining surface texturing and deposition of osteocompatible C(3)N(4)-Si coating.
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| 5. |
- Myllymaa, Katja, et al.
(författare)
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Interactions between Saos-2 cells and microtextured amorphous diamond or amorphous diamond hybrid coated surfaces with different wettability properties
- 2009
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Ingår i: Diamond and Related Materials. - : Elsevier. - 0925-9635. ; 18:10, s. 1294-1300
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous diamond (AD) has been shown to be a potential coating material for biomedical devices, such as hip prostheses. In the current study, we have investigated the adhesion and contact guidance of human primary osteogenic sarcoma cells (Saos-2) on AD, AD-titanium-hybrid (AD-Ti-h) and AD-polydimethylsiloxane-hybrid (AD-PDMS-h) with different water contact angles i.e. 72.4°, 81.9° and 100.0°. Microtextured arrays were fabricated onto silicon wafers by using ultraviolet lithography and ultra short pulsed laser deposition (USPLD) of AD coatings. The surface energy parameters were calculated in order to understand the influence of Ti or PDMS on wettability of AD. Saos-2 cells were cultured on the arrays for 24 and 48 h. Environmental scanning electron microscope (ESEM), confocal laser scanning microscopy and MTT assays were used to analyze cell attachment. The results suggest that AD and its hybrids are good coating material candidates with respect to their interactions with osteoblast-like cells. The efficiency of microtexturing in contact guidance was also demonstrated. MTT staining revealed that AD-PDMS-h had the lowest proliferation rate of osteoblast-like cells compared to AD (p < 0.01) or AD-Ti-h (p < 0.05). Pure AD evoked the highest proliferation rate of cells, though it was not significantly different from AD-Ti-h coating.
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| 6. |
- Myllymaa, Sami, et al.
(författare)
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Surface characterization and in vitro biocompatibility assessment of photosensitive polyimide films.
- 2010
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Ingår i: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 76:2, s. 505-511
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Tidskriftsartikel (refereegranskat)abstract
- Polyimide (PI) is a commonly used polymer in microelectronics. Recently, numerous PI-based flexible neural interfaces have been developed for reducing mechanical mismatch between rigid implant and soft neural tissue. Most approaches employ non-photosensitive PI, which has been proven earlier to be biocompatible. However, photosensitive polyimide (PSPI) would simplify device fabrication remarkably, but its biocompatibility has been only sparsely reported. In this study, cytotoxicity of spin-coated PSPI (HD Microsystems PI-2771) and conventional PI (HD Microsystems PI-2525) films were evaluated in vitro using BHK-21 fibroblasts according to the ISO-10993-5 standard. PSPIs were tested as cured at a temperature of 200 degrees C (PI-2771-200) and 350 degrees C (PI-2771-350). The PI film surfaces were characterized in terms of their roughness, energy and zeta potential which are hypothesized to affect cell-material interactions. The values of the total surface free energy (SFE), and its polar and dispersive component, were significantly (p<0.001) greater for the PI-2525 film (SFE: 47.3 mJ/m2) than for the PI-2771-200 (25.6 mJ/m2) or PI-2771-350 films (26.2 mJ/m2). The curing temperature of the PI-2771 had a significant effect on the zeta potential values (p<0.001), but not on surface energy (p=0.091) or roughness (p=0.717). The results from the MTS proliferation assays and live/dead staining revealed that PSPI is almost as non-cytotoxic as conventional PI and polyethylene (negative control). The morphology and spreading of BHK-21 cells were similar on all the PI materials tested. In conclusion, PSPI seems to be a promising biocompatible material, while further studies in vitro and in vivo are needed to clarify the long-term effects.
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| 7. |
- Puhakka, Pia, et al.
(författare)
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Dependence of light attenuation and backscattering on collagen concentration and chondrocyte density in agarose scaffolds
- 2014
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Ingår i: Physics in Medicine and Biology. - : Institute of Physics Publishing (IOPP). - 0031-9155 .- 1361-6560. ; 59:21, s. 6537-6548
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Tidskriftsartikel (refereegranskat)abstract
- Optical coherence tomography (OCT) has been applied for high resolution imaging of articular cartilage. However, the contribution of individual structural elements of cartilage on OCT signal has not been thoroughly studied. We hypothesize that both collagen and chondrocytes, essential structural components of cartilage, act as important light scatterers and that variation in their concentrations can be detected by OCT through changes in backscattering and attenuation. To evaluate this hypothesis, we established a controlled model system using agarose scaffolds embedded with variable collagen concentrations and chondrocyte densities. Using OCT, we measured the backscattering coefficient (µb) and total attenuation coefficient (µt) in these scaffolds. Along our hypothesis, light backscattering and attenuation in agarose were dependent on collagen concentration and chondrocyte density. Significant correlations were found between µt and chondrocyte density (ρ = 0.853, p < 0.001) and between µt and collagen concentration (ρ = 0.694, p < 0.001). µb correlated significantly with chondrocyte density (ρ = 0.504, p < 0.001) but not with collagen concentration (ρ = 0.103, p = 0.422) of the scaffold. Thus, quantitation of light backscattering and, especially, attenuation could be valuable when evaluating the integrity of soft tissues, such as articular cartilage with OCT.
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| 8. |
- Pulkkinen, Hertta, et al.
(författare)
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Cellulose sponge as a scaffold for cartilage tissue engineering.
- 2006
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Ingår i: Bio-medical materials and engineering. - : IOS Press. - 0959-2989 .- 1878-3619. ; 16:4 Suppl, s. S29-S35
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Tidskriftsartikel (refereegranskat)abstract
- One goal of functional tissue engineering is to manufacture scaffolds infiltrated with chondrocytes which are suitable for transplantation into the lesion areas of articular cartilage. Various research strategies are used to fabricate cartilage transplants which would have the correct phenotype, contain enough extracellular matrix components, and have structural and biomechanical properties equivalent to normal articular cartilage. We have investigated the suitability of viscose cellulose sponges as a scaffold for cartilage tissue engineering. The sponges were tested alone, or with recombinant human type II collagen cross-linked inside the material. Scanning electron microscopy and confocal microscopy were used to study the structure of the scaffold during four weeks of cultivation. Cellulose and cellulose/recombinant type II collagen sponges were biocompatible for at least four weeks in cultivation, and gradual filling of the scaffold was observed. However, the constructs remained soft during the observation period, and were devoid of extracellular matrix composition typical for normal articular cartilage.
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| 9. |
- Pulkkinen, Hertta, et al.
(författare)
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Engineering of cartilage in recombinant human type II collagen gel in nude mouse model in vivo.
- 2010
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Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584 .- 1522-9653. ; 18:8, s. 1077-1087
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Our goal was to test the recombinant human type II collagen (rhCII) material as a gel-like scaffold for chondrocytes in a nude mouse model in vivo.DESIGN: Isolated bovine chondrocytes (6x10(6)) were seeded into rhCII gels (rhCII-cell) and injected subcutaneously into the backs of nude mice. For comparison, chondrocytes (6x10(6)) in culture medium (Med-cell) and cell-free rhCII gels (rhCII-gel) were similarly injected (n=24 animals, total of three injections/animal). After 6 weeks, the tissue constructs were harvested and analyzed.RESULTS: Chondrocytes with or without rhCII-gel produced white resilient tissue, which in histological sections had chondrocytes in lacunae-like structures. Extracellular matrix stained heavily with toluidine blue stain and had strongly positive collagen type II immunostaining. The tissue did not show any evidence of vascular invasion or mineralization. The cell-free rhCII-gel constructs showed no signs of cartilage tissue formation. Cartilage tissue produced by Med-cell was thin and macroscopically uneven, while the rhCII-cell construct was smooth and rounded piece of neotissue. RhCII-cell constructs were statistically thicker than Med-cell ones. However, no statistical differences were found between the groups in terms of glycosaminoglycan (GAG) content or biomechanical properties.CONCLUSIONS: These results show that rhCII-gel provides good expansion and mechanical support for the formation of cartilage neotissue. RhCII material may allow favorable conditions in the repair of chondral lesions.
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| 10. |
- Pulkkinen, Hertta, et al.
(författare)
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Recombinant human type II collagen as a material for cartilage tissue engineering.
- 2008
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Ingår i: International Journal of Artificial Organs. - : Wichtig Editore Srl. - 0391-3988 .- 1724-6040. ; 31:11, s. 960-969
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Collagen type II is the major component of cartilage and would be an optimal scaffold material for reconstruction of injured cartilage tissue. In this study, the feasibility of recombinant human type II collagen gel as a 3-dimensional culture system for bovine chondrocytes was evaluated in vitro.METHODS: Bovine chondrocytes (4x106 cells) were seeded within collagen gels and cultivated for up to 4 weeks. The gels were investigated with confocal microscopy, histology, and biochemical assays.RESULTS: Confocal microscopy revealed that the cells maintained their viability during the entire cultivation period. The chondrocytes were evenly distributed inside the gels, and the number of cells and the amount of the extracellular matrix increased during cultivation. The chondrocytes maintained their round phenotype during the 4-week cultivation period. The glycosaminoglycan levels of the tissue increased during the experiment. The relative levels of aggrecan and type II collagen mRNA measured with realtime polymerase chain reaction (PCR) showed an increase at 1 week.CONCLUSION: Our results imply that recombinant human type II collagen is a promising biomaterial for cartilage tissue engineering, allowing homogeneous distribution in the gel and biosynthesis of extracellular matrix components.
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