| 1. |
- Ahmed, Mona, et al.
(författare)
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Cellular Uptake of Plain and SPION-Modified Microbubbles for Potential Use in Molecular Imaging
- 2017
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Ingår i: Cellular and Molecular Bioengineering. - : SPRINGER. - 1865-5025 .- 1865-5033. ; 10:6, s. 537-548
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Tidskriftsartikel (refereegranskat)abstract
- Both diagnostic ultrasound (US) and magnetic resonance imaging (MRI) accuracy can be improved by using contrast enhancement. For US gas-filled microbubbles (MBs) or silica nanoparticles (SiNPs), and for MRI superparamagnetic or paramagnetic agents, contribute to this. However, interactions of MBs with the vascular wall and cells are not fully known for all contrast media. We studied the in vitro interactions between three types of non-targeted air-filled MBs with a polyvinyl-alcohol shell and murine macrophages or endothelial cells. The three MB types were plain MBs and two types that were labelled (internally and externally) with superparamagnetic iron oxide nanoparticles (SPIONs) for US/MRI bimodality. Cells were incubated with MBs and imaged by microscopy to evaluate uptake and adhesion. Interactions were quantified and the MB internalization was confirmed by fluorescence quenching of non-internalized MBs. Macrophages internalized each MB type within different time frames: plain MBs 6 h, externally labelled MBs 25 min and internally labelled MBs 2 h. An average of 0.14 externally labelled MBs per cell were internalized after 30 min and 1.34 after 2 h; which was 113% more MBs than the number of internalized internally labelled MBs. The macrophages engulfed these three differently modified new MBs at various rate, whereas endothelial cells did not engulf MBs. Polyvinyl-alcohol MBs are not taken up by endothelial cells. The MB uptake by macrophages is promoted by SPION labelling, in particular external such, which may be important for macrophage targeting.
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| 2. |
- Brismar, Torkel B., et al.
(författare)
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Magnetite Nanoparticles Can Be Coupled to Microbubbles to Support Multimodal Imaging
- 2012
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 13:5, s. 1390-1399
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Tidskriftsartikel (refereegranskat)abstract
- Microbubbles (MBs) are commonly used as injectable ultrasound contrast agent (UCA) in modern ultrasonography. Polymer-shelled UCAs present additional potentialities with respect to marketed lipid-shelled UCAs. They are more robust; that is, they have longer shelf and circulation life, and surface modifications are quite easily accomplished to obtain enhanced targeting and local drug delivery. The next generation of UCAs will be required to support not only ultrasound-based imaging methods but also other complementary diagnostic approaches such as magnetic resonance imaging or computer tomography. This work addresses the features of MBs that could function as contrast agents for both ultrasound and magnetic resonance imaging. The results indicate that the introduction of iron oxide nanoparticles (SPIONs) in the poly(vinyl alcohol) shell or on the external surface of the MBs does not greatly decrease the echogenicity of the host MBs compared with the unmodified one. The presence of SPIONs provides enough magnetic susceptibility to the MBs to accomplish good detectability both in vitro and in vivo. The distribution of SPIONs on the shell and their aggregation state seem to be key factors for the optimization of the transverse relaxation rate.
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| 3. |
- Härmark, Johan, et al.
(författare)
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Investigation of the elimination process of a multimodal polymer-shelled contrast agent in rats using ultrasound and transmission electron microscopy
- 2015
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Ingår i: Biomedical Spectroscopy and Imaging. - 2212-8794. ; 4:1, s. 81-93
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A novel polymer-shelled contrast agent (CA) with multimodal imaging and target specific potential was developed recently and tested for its acoustical properties using different in-vitro setups.OBJECTIVE: The aim of this study was to investigate the elimination of three types of the novel polymer-shelled CA, one unmodified and two shell modified versions, in rats.METHODS: The blood elimination time was estimated by measuring the image intensity, from ultrasound images of the common carotid artery, over time after a bolus injection of the three types of the novel CA. The commercially available CA SonoVue was used as a reference. The subcellular localization of the three CAs was investigated using transmission electron microscopy.RESULTS: The ultrasound measurements indicated a blood half-life of 17–85 s for the different types of the novel CA, which was significant longer than the blood half-life time for SonoVue. Additionally, CAs were exclusively found in the circulatory system, either taken up by, or found in the vicinity of macrophages.CONCLUSIONS: Compared to the commercially available CA SonoVue, the blood circulation times for the three types of the novel polymer-shelled CA were prolonged. Moreover, macrophages were suggested to be responsible for the elimination of the CA.
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| 4. |
- Härmark, Johan, et al.
(författare)
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Shell thickness determination of polymer-shelled microbubbles using transmission electron microscopy
- 2016
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Ingår i: Micron. - : Elsevier. - 0968-4328 .- 1878-4291. ; 85, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- Intravenously injected microbubbles (MBs) can be utilized as ultrasound contrast agent (CA) resulting in enhanced image quality. A novel CA, consisting of air filled MBs stabilized with a shell of polyvinyl alcohol (PVA) has been developed. These spherical MBs have been decorated with superparamagnetic iron oxide nanoparticles (SPIONs) in order to serve as both ultrasound and magnetic resonance imaging (MRI) CA. In this study, a mathematical model was introduced that determined the shell thickness of two types of SPIONs decorated MBs (Type A and Type B). The shell thickness of MBs is important to determine, as it affects the acoustical properties. In order to investigate the shell thickness, thin sections of plastic embedded MBs were prepared and imaged using transmission electron microscopy (TEM). However, the sections were cut at random distances from the MB center, which affected the observed shell thickness. Hence, the model determined the average shell thickness of the MBs from corrected mean values of the outer and inner radii observed in the TEM sections. The model was validated using simulated slices of MBs with known shell thickness and radius. The average shell thickness of Type A and Type B MBs were 651nm and 637nm, respectively.
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| 5. |
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| 6. |
- Härmark, Johan, 1984-
(författare)
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Structural studies of microbubbles and molecular chaperones using transmission electron microscopy
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ultrasound contrast agents (CAs) are typically used in clinic for perfusion studies (blood flow through a specific region) and border delineating (differentiate borders between tissue structures) during cardiac imaging. The CAs used during ultrasound imaging usually consist of gas filled microbubbles (MBs) (diameter 1-5 μm) that are injected intravenously into the circulatory system. This thesis partially involves a novel polymer-shelled ultrasound CA that consists of air filled MBs stabilized by a polyvinyl alcohol (PVA) shell. These MBs could be coupled with superparamagnetic iron oxide nanoparticles (SPIONs) in order to serve as a combined CA for ultrasound and magnetic resonance imaging. The first three papers (Paper A-C) in this thesis investigate the structural characteristic and the elimination process of the CA.In Paper A, two types (PVA Type A and PVA Type B) of the novel CA were analyzed using transmission electron microscopy (TEM) images of thin sectioned MBs. The images demonstrated that the SPIONs were either attached to the PVA shell surface (PVA Type A) or embedded in the shell (PVA Type B). The average shell thickness of the MBs was determined in Paper B by introducing a model that calculated the shell thickness from TEM images of cross-sectioned MBs. The shell thickness of PVA Type A was determined to 651 nm, whereas the shell thickness of PVA Type B was calculated to 637 nm. In Paper C, a prolonged blood elimination time was obtained for PVA-shelled MBs compared to the lipid-shelled CA SonoVue used in clinic. In addition, TEM analyzed tissue sections showed that the PVA-shelled MBs were recognized by the macrophage system. However, structurally intact MBs were still found in the circulation 24 h post injection. These studies illustrate that the PVA-shelled MBs are stable and offer large chemical variability, which make them suitable as CA for multimodal imaging.This thesis also involves studies (Paper D-E) of the molecular chaperones (Hsp21 and DNAJB6). The small heat shock protein Hsp21 effectively protects other proteins from unfolding and aggregation during stress. This chaperone ability requires oligomerization of the protein. In Paper D, cryo-electron microscopy together with complementary structural methods, obtained a structure model which showed that the Hsp21 dodecamer (12-mer) is kept together by paired C-terminal interactions.The human protein DNAJB6 functions as a very efficient suppressor of polyglutamine (polyQ) and amyloid-β42 (Aβ42) aggregation. Aggregation of these peptides are associated with development of Huntington’s (polyQ) and Alzheimer’s (Aβ42) disease. In Paper E, a reconstructed map of this highly dynamic protein is presented, showing an oligomer with two-fold symmetry, indicating that the oligomers are assembled by two subunits.
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| 7. |
- Loureiro, A., et al.
(författare)
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Size controlled protein nanoemulsions for active targeting of folate receptor positive cells
- 2015
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Ingår i: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 135, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- Bovine serum albumin (BSA) nanoemulsions were produced by high pressure homogenization with a tri-block copolymer (Poloxamer 407), which presents a central hydrophobic chain of polyoxypropylene (PPO) and two identical lateral hydrophilic chains of polyethylene glycol (PEG). We observed a linear correlation between tri-block copolymer concentration and size - the use of 5. mg/mL of Poloxamer 407 yields nanoemulsions smaller than 100. nm. Molecular dynamics and fluorescent tagging of the tri-block copolymer highlight their mechanistic role on the size of emulsions. This novel method enables the fabrication of highly stable albumin emulsions in the nano-size range, highly desirable for controlled drug delivery. Folic Acid (FA)-tagged protein nanoemulsions were shown to promote specific folate receptor (FR)-mediated targeting in FR positive cells. The novel strategy presented here enables the construction of size controlled, functionalized protein-based nanoemulsions with excellent characteristics for active targeting in cancer therapy.
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| 8. |
- Månsson, Cecilia, et al.
(författare)
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DNAJB6 is a peptide-binding chaperone which can suppress amyloid fibrillation of polyglutamine peptides at substoichiometric molar ratios.
- 2014
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Ingår i: Cell Stress & Chaperones. - : Springer Science and Business Media LLC. - 1466-1268 .- 1355-8145. ; 19:2, s. 227-239
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Tidskriftsartikel (refereegranskat)abstract
- Expanded polyglutamine (polyQ) stretches lead to protein aggregation and severe neurodegenerative diseases. A highly efficient suppressor of polyQ aggregation was identified, the DNAJB6, when molecular chaperones from the HSPH, HSPA, and DNAJ families were screened for huntingtin exon 1 aggregation in cells (Hageman et al. in Mol Cell 37(3):355-369, 2010). Furthermore, also aggregation of polyQ peptides expressed in cells was recently found to be efficiently suppressed by co-expression of DNAJB6 (Gillis et al. in J Biol Chem 288:17225-17237, 2013). These suppression effects can be due to an indirect effect of DNAJB6 on other cellular components or to a direct interaction between DNAJB6 and polyQ peptides that may depend on other cellular components. Here, we have purified the DNAJB6 protein to investigate the suppression mechanism. The purified DNAJB6 protein formed large heterogeneous oligomers, in contrast to the more canonical family member DNAJB1 which is dimeric. Purified DNAJB6 protein, at substoichiometric molar ratios, efficiently suppressed fibrillation of polyQ peptides with 45°Q in a thioflavin T fibrillation. No suppression was obtained with DNAJB1, but with the closest homologue to DNAJB6, DNAJB8. The suppression effect was independent of HSPA1 and ATP. These data, based on purified proteins and controlled fibrillation in vitro, strongly suggest that the fibrillation suppression is due to a direct protein-protein interaction between the polyQ peptides and DNAJB6 and that the DNAJB6 has unique fibrillation suppression properties lacking in DNAJB1. Together, the data obtained in cells and in vitro support the view that DNAJB6 is a peptide-binding chaperone that can interact with polyQ peptides that are incompletely degraded by and released from the proteasome.
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| 9. |
- Nogueira, Eugenia, et al.
(författare)
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Liposome and protein based stealth nanoparticles
- 2013
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 166, s. 417-429
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Tidskriftsartikel (refereegranskat)abstract
- Liposomes and protein based nanoparticles were tuned with different polymers and glycolipids to improve stealth and thus decrease their clearance by macrophages. Liposomes were coated with polyethylene glycol (PEG) and brain-tissue-derived monosialoganglioside (GM1). Bovine serum albumin (BSA) nanoparticles were produced incorporating a PEGylated surfactant (PEG-surfactant). All obtained nanoparticles were monodisperse, with sizes ranging from 80 to 120 nm, with a zeta-potential close to zero. The presented stealth strategies lead to a decrease of internalization levels by macrophages. These surface modified nanoparticles could be used for production of new drug delivery nanosystems for systemic administration (e.g. intravenous application).
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| 10. |
- Nogueira, Eugenia, et al.
(författare)
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Peptide Anchor for Folate-Targeted Liposomal Delivery
- 2015
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 16:9, s. 2904-2910
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Tidskriftsartikel (refereegranskat)abstract
- Specific folate receptors are abundantly overexpressed in chronically activated macrophages and in most cancer cells. Directed folate receptor targeting using liposomes is usually achieved using folate linked to a phospholipid or cholesterol anchor. This link is formed using a large spacer like polyethylene glycol. Here, we report an innovative strategy for targeted liposome delivery that uses a hydrophobic fragment of surfactant protein D linked to folate. Our proposed spacer is a small 4 amino acid residue linker. The peptide conjugate inserts deeply into the lipid bilayer without affecting liposomal integrity, with high stability and specificity. To compare the drug delivery potential of both liposomal targeting systems, we encapsulated the nuclear dye Hoechst 34580. The eventual increase in blue fluorescence would only be detectable upon liposome disruption, leading to specific binding of this dye to DNA. Our delivery system was proven to be more efficient (2-fold) in Caco-2 cells than classic systems where the folate moiety is linked to liposomes by polyethylene glycol.
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