| 1. |
- Erikson, Arne, et al.
(författare)
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Quantification of the second-order nonlinear susceptibility of collagen I using a laser scanning microscope
- 2007
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Ingår i: Journal of Biomedical Optics. - : SPIE-Intl Soc Optical Eng. - 1083-3668 .- 1560-2281. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- Characteristic changes in the organization of fibrillar collagen can potentially serve as an early diagnostic marker in various pathological processes. Tissue types containing collagen I can be probed by pulsed high-intensity laser radiation, thereby generating second harmonic light that provides information about the composition and structure at a microscopic level. A technique was developed to determine the essential second harmonic generation (SHG) parameters in a laser scanning microscope setup. A rat-tail tendon frozen section was rotated in the xy-plane with the pulsed laser light propagating along the z-axis. By analyzing the generated second harmonic light in the forward direction with parallel and crossed polarizer relative to the polarization of the excitation laser beam, the second-order nonlinear optical susceptibilities of the collagen fiber were determined. Systematic variations in SHG response between ordered and less ordered structures were recorded and evaluated. A 500µm-thick z-cut lithiumniobate (LiNbO3) was used as reference. The method was applied on frozen sections of malignant melanoma and normal skin tissue. Significant differences were found in the values of d22, indicating that this parameter has a potential role in differentiating between normal and pathological processes.
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| 2. |
- Lilledahl, Magnus B., et al.
(författare)
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Structural Analysis of Articular Cartilage Using Multiphoton Microscopy : Input for Biomechanical Modeling
- 2011
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Ingår i: IEEE Transactions on Medical Imaging. - 0278-0062 .- 1558-254X. ; 30:9, s. 1635-1648
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Tidskriftsartikel (refereegranskat)abstract
- The 3-D morphology of chicken articular cartilage was quantified using multiphoton microscopy (MPM) for use in continuum-mechanical modeling. To motivate this morphological study we propose aspects of a new, 3-D finite strain constitutive model for articular cartilage focusing on the essential load-bearing morphology: an inhomogeneous, poro-(visco) elastic solid matrix reinforced by an anisotropic, (visco) elastic dispersed fiber fabric which is saturated by an incompressible fluid residing in strain-dependent pores. Samples of fresh chicken cartilage were sectioned in three orthogonal planes and imaged using MPM, specifically imaging the collagen fibers using second harmonic generation. Employing image analysis techniques based on Fourier analysis, we derived the principal directionality and dispersion of the collagen fiber fabric in the superficial layer. In the middle layer, objective thresholding techniques were used to extract the volume fraction occupied by extracellular collagen matrix. In conjunction with information available in the literature, or additional experimental testing, we show how this data can be used to derive a 3-D map of the initial solid volume fraction and Darcy permeability.
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| 3. |
- Shanbhag, Siddharth, et al.
(författare)
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Spheroid Coculture of Human Gingiva-Derived Progenitor Cells With Endothelial Cells in Modified Platelet Lysate Hydrogels
- 2021
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media S.A.. - 2296-4185. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Cell coculture strategies can promote angiogenesis within tissue engineering constructs. This study aimed to test the angiogenic potential of human umbilical vein endothelial cells (HUVEC) cocultured with gingiva-derived progenitor cells (GPC) as spheroids in a xeno-free environment. Human platelet lysate (HPL) was used as a cell culture supplement and as a hydrogel matrix (HPLG) for spheroid encapsulation. HUVEC and HUVEC + GPC (1:1 or 5:1) spheroids were encapsulated in various HPLG formulations. Angiogenesis was assessed via in vitro sprouting and in vivo chick chorioallantoic membrane (CAM) assays. HUVEC revealed characteristic in vitro sprouting in HPL/HPLG and this was significantly enhanced in cocultures with GPC (p < 0.05). A trend for greater sprouting was observed in 5:1 vs 1:1 HUVEC + GPC spheroids and in certain HPLG formulations (p > 0.05). Both HUVEC and HUVEC + GPC spheroids in HPLG revealed abundant and comparable neoangiogenesis in the CAM assay (p > 0.05). Spheroid coculture of HUVEC + GPC in HPLG represents a promising strategy to promote angiogenesis.
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| 4. |
- Snipstad, Sofie, et al.
(författare)
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Labeling nanoparticles : Dye leakage and altered cellular uptake
- 2017
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Ingår i: Cytometry Part A. - : John Wiley & Sons. - 1552-4922 .- 1552-4930. ; 91:8, s. 760-766
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Tidskriftsartikel (refereegranskat)abstract
- In vitro and in vivo behavior of nanoparticles (NPs) is often studied by tracing the NPs with fluorescent dyes. This requires stable incorporation of dyes within the NPs, as dye leakage may give a wrong interpretation of NP biodistribution, cellular uptake, and intracellular distribution. Furthermore, NP labeling with trace amounts of dye should not alter NP properties such as interactions with cells or tissues. To allow for versatile NP studies with a variety of fluorescence-based assays, labeling of NPs with different dyes is desirable. Hence, when new dyes are introduced, simple and fast screening methods to assess labeling stability and NP-cell interactions are needed. For this purpose, we have used a previously described generic flow cytometry assay; incubation of cells with NPs at 4 and 37C. Cell-NP interaction is confirmed by cellular fluorescence after 37C incubation, and NP-dye retention is confirmed when no cellular fluorescence is detected at 4C. Three different NP-platforms labeled with six different dyes were screened, and a great variability in dye retention was observed. Surprisingly, incorporation of trace amounts of certain dyes was found to reduce or even inhibit NP uptake. This work highlights the importance of thoroughly evaluating every dye-NP combination before pursuing NP-based applications. © 2016 International Society for Advancement of Cytometry.
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| 5. |
- Strand, Sabina P, et al.
(författare)
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Molecular design of chitosan gene delivery systems with an optimized balance between polyplex stability and polyplex unpacking
- 2010
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 31:5, s. 975-987
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan is an attractive gene delivery vehicle, but the criteria and strategies for the design of efficient chitosan gene delivery systems remain unclear. The purpose of this work was to investigate how the strength of the charge-based interaction between chitosan and DNA determines the gene expression levels and to design chitosan vectors with an optimized balance between polyplex stability and polyplex unpacking. Using 21 formulations based on low molecular weight chitosans with constant charge density and a number-average degree of polymerization (DPn) in the range of 21-88 (M(w) 4.7-33kDa), we studied the relationship between the chain length and the formulation properties, cellular uptake of polyplexes and gene transfer efficacy. We were able to identify a narrow interval of DPn31-42 that mediated the maximum level of transgene expression. An increase in chain length and/or the amino-phosphate (A/P) ratio reduced and delayed transgene expression. Compared to DPn31, transfection with the same amount of DPn72 or DPn88 resulted in 10-fold-lower expression levels. The gene transfer pattern correlated with the ability of heparin to release DNA from the polyplexes. As a tool to facilitate the unpacking of the polyplexes, we substituted the chitosans with uncharged oligosaccharides that reduced the interaction with DNA. The substitution of chitosans that originally yielded too stable polyplexes, such as DPn72 and DPn88 resulted in a 5-10-fold enhancement of the expression levels. However, the substitution of chitosans shorter than DP28 completely abolished transfection. Tailoring of the chain length and the substitution of chitosan were shown to be feasible tools to modulate the electrostatic interactions between the chitosan and DNA and to design chitosans with an optimized balance between polyplex stability and polyplex unpacking.
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| 6. |
- Sulheim, Einar, et al.
(författare)
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Contrast Enhanced Magnetic Resonance Imaging of Amyloid-beta Plaques in a Murine Alzheimers Disease Model
- 2023
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Ingår i: Journal of Alzheimer's Disease. - : IOS PRESS. - 1387-2877 .- 1875-8908. ; 93:2, s. 411-419
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Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of amyloid-beta(A beta) aggregates is a critical step to improve the treatment of Alzheimers disease (AD) because neuronal damage by the A beta aggregates occurs before clinical symptoms are apparent. We have previously shown that luminescent conjugated oligothiophenes (LCOs), which are highly specific towards protein aggregates of A beta, can be used to fluorescently label amyloid plaque in living rodents. Objective: We hypothesize that the LCO can be used to target gadolinium to the amyloid plaque and hence make the plaque detectable by T-1-weighted magnetic resonance imaging (MRI). Methods: A novel LCO-gadolinium construct was synthesized to selectively bind to A beta plaques and give contrast in conventional T-1-weighted MR images after intravenous injection in Tg-APPSwe mice. Results: We found that mice with high plaque-burden could be identified using the LCO-Gd constructs by conventional MRI. Conclusion: Our study shows that MR imaging of amyloid plaques is challenging but feasible, and hence contrast-mediated MR imaging could be a valuable tool for early AD detection.
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| 7. |
- Åslund, Andreas K. O., et al.
(författare)
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Nanoparticle delivery to the brain - By focused ultrasound and self-assembled nanoparticle-stabilized microbubbles
- 2015
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 220, s. 287-294
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Tidskriftsartikel (refereegranskat)abstract
- The blood-brain barrier (BBB) constitutes a significant obstacle for the delivery of drugs into the central nervous system(CNS). Nanoparticles have been able to partly overcome this obstacle and can thus improve drug delivery across the BBB. Furthermore, focused ultrasound in combination with gas filled microbubbles has opened the BBB in a temporospatial manner in animal models, thus facilitating drug delivery across the BBB. In the current study we combine these two approaches in our quest to develop a novel, generic method for drug delivery across the BBB and into the CNS. Nanoparticles were synthesized using the polymer poly(butyl cyanoacrylate) (PBCA), and such nanoparticles have been reported to cross the BBB to some extent. Together with proteins, these nanoparticles self-assemble into microbubbles. Using these novel microbubbles in combination with focused ultrasound, we successfully and safely opened the BBB transiently in healthy rats. Furthermore, we also demonstrated that the nanoparticles could cross the BBB and deliver a model drug into the CNS.
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