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  • 101.
    Asp, Vendela
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
    In Vitro Studies of Adrenocorticolytic DDT Metabolites, with Special Focus on 3-methylsulfonyl-DDE2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The DDT metabolite 3-methylsulfonyl-DDE (3-MeSO2-DDE) is bioactivated by cytochrome P450 11B1 (CYP11B1) in the adrenal cortex of mice and forms irreversibly bound protein adducts, reduces glucocorticoid secretion, and induces cell death selectively in cortisol-producing adrenocortical cells. 3-MeSO2-DDE has therefore been proposed as a lead compound for an improved adrenocortical carcinoma (ACC) therapy.

    The aims of this thesis were to (1) develop in vitro test systems based on murine and human adrenocortical cell lines and to (2) investigate the mechanisms behind 3-MeSO2-DDE toxicity in adrenocortical cells.

    The cytotoxic and endocrine-modulating effects of 3-MeSO2-DDE were compared to those of o,p′-DDD (mitotane), the current ACC therapy, and to those of several structurally analogous compounds in both murine and human cell lines. 3-MeSO2-DDE bioactivation and cytotoxicity proceeded in a similar manner in the murine adrenocortical Y-1 cell line as in mice in vivo. The effects were highly structure-specific. Moreover, 3-MeSO2-DDE formed irreversibly bound protein adducts and caused cell death also in the human H295R cell line, and was slightly more cytotoxic than o,p′-DDD. However, 3-MeSO2-DDE toxicity in human cells was not affected by the CYP11B1 inhibitor etomidate, suggesting that bioactivation in human cells is performed by additional/other enzyme(s) than CYP11B1. 3-MeSO2-DDE generated biphasic responses in cortisol and aldosterone secretion and in expression levels of the steroidogenic genes CYP11B1, CYP11B2, and StAR. Such hormesis-like responses were not seen for o,p′-DDD or the precursor DDT metabolite p,p′-DDE.

    In addition, the two o,p′-DDD enantiomers (R)-(+)-o,p′-DDD and (S)-(-)-o,p′-DDD exhibited slight differences in cytotoxic and endocrine-modulating activity in H295R cells.

    In conclusion, this thesis  provides  extended  knowledge  on  the  mechanisms  of  action  of 3-MeSO2-DDE and points out important differences in effects between murine and human cells. Lead optimisation studies of 3-MeSO2-DDE using the herein presented in vitro test systems are ongoing.

     

    List of papers
    1. Cytotoxicity and decreased corticosterone production in adrenocortical Y-1 cells by 3-methylsulfonyl-DDE and structurally related molecules
    Open this publication in new window or tab >>Cytotoxicity and decreased corticosterone production in adrenocortical Y-1 cells by 3-methylsulfonyl-DDE and structurally related molecules
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    2009 (English)In: Archives of Toxicology, ISSN 0340-5761, E-ISSN 1432-0738, Vol. 83, no 4, p. 389-396Article in journal (Refereed) Published
    Abstract [en]

    The persistent environmental pollutant 3-methylsulfonyl-DDE (3-MeSO2-DDE) undergoes bioactivation by cytochrome P450 11B1 (CYP11B1) in the adrenal cortex of several animal species in vivo and causes decreased glucocorticoid production and cell death in the zona fasciculata. This study presents extended investigations of the cytotoxic and endocrine disrupting effects of 3-MeSO2-DDE and some structurally related molecules in the mouse adrenocortical cell line Y-1. Both 3-MeSO2-DDE and, to a lesser extent, 3,3'(bis)-MeSO2-DDE decreased corticosterone production and produced CYP11B1-dependent cytotoxicity in Y-1 cells. Neither 2-MeSO2-DDE nor p,p'-DDE had any significant effect on either cell viability or corticosterone production, indicating that the presence and position of the methylsulfonyl moiety of 3-MeSO2-DDE is crucial for its biological activity. The adrenocortical toxicant o,p'-DDD decreased corticosterone production but was not cytotoxic in this cell line. None of the compounds altered Cyp11b1 gene expression, indicating that 3-MeSO2-DDE inhibits CYP11B1 activity on the protein level.

    Keywords
    Adrenal cortex, Metabolic activation, Toxicity, Corticosterone, DDE, CYP11B1
    National Category
    Biological Sciences
    Research subject
    Ecotoxicology
    Identifiers
    urn:nbn:se:uu:diva-100855 (URN)10.1007/s00204-008-0342-6 (DOI)000264883800012 ()18651133 (PubMedID)
    Available from: 2009-04-08 Created: 2009-04-08 Last updated: 2017-12-13Bibliographically approved
    2. Comparative CYP-dependent binding of the adrenocortical toxicants 3-methylsulfonyl-DDE and o,p′-DDD in Y-1 adrenal cells
    Open this publication in new window or tab >>Comparative CYP-dependent binding of the adrenocortical toxicants 3-methylsulfonyl-DDE and o,p′-DDD in Y-1 adrenal cells
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    2007 (English)In: Archives of Toxicology, ISSN 0340-5761, E-ISSN 1432-0738, Vol. 81, no 11, p. 793-801Article in journal (Refereed) Published
    Abstract [en]

    The environmental pollutant 3-MeSO2–DDE [2-(3-methylsulfonyl-4-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethene] is an adrenocortical toxicant in mice, specifically in the glucocorticoid-producing zona fasciculata, due to a cytochrome P450 11B1 (CYP11B1)-catalysed bioactivation and formation of covalently bound protein adducts. o,p′-DDD [2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethane] is toxic and inhibits steroidogenesis in the human adrenal cortex after bioactivation by unidentified CYPs, but does not exert any toxic effects on the mouse adrenal. As a step towards determining in vitro/in vivo relationships for the CYP-catalysed binding and toxicity of 3-MeSO2–DDE and o,p′-DDD, we have investigated the irreversible protein binding of these two toxicants in the murine adrenocortical cell line Y-1. The irreversible binding of 3-MeSO2–DDE previously demonstrated in vivo was successfully reproduced and could be inhibited by the CYP-inhibitors etomidate, ketoconazole and metyrapone. Surprisingly, o,p′-DDD reached similar levels of binding as 3-MeSO2–DDE. The binding of o,p′-DDD was sensitive to etomidate and ketoconazole, but not to metyrapone. Moreover, GSH depletion increased the binding of 3-MeSO2–DDE, but not of o,p′-DDD, indicating an important role of GSH conjugation in the detoxification of the 3-MeSO2–DDE-derived reactive metabolite. In addition, the specificity of CYP11B1 in activating 3-MeSO2–DDE was investigated using structurally analogous compounds. None of the analogues produced histopathological lesions in the mouse adrenal in vivo following a single i.p. injection of 100 mg/kg body weight, but two of the compounds were able to decrease the irreversible binding of 3-MeSO2–DDE to Y-1 cells. These results indicate that the bioactivation of 3-MeSO2–DDE by CYP11B1 is highly structure-dependent. In conclusion, both 3-MeSO2–DDE and o,p′-DDD bind irreversibly to Y-1 cells despite differences in binding and adrenotoxicity in mice in vivo. This reveals a notable in vitro/in vivo discrepancy, the contributing factors of which remain unexplained. We consider the Y-1 cell line as appropriate for studies of the cellular mechanisms behind the adrenocortical toxicity of these substances.

    Keywords
    Adrenal cortex, Cytochrome P450, Metabolic activation, Toxicity, Y-1
    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-14330 (URN)10.1007/s00204-007-0206-5 (DOI)000250537400006 ()17487473 (PubMedID)
    Available from: 2008-05-15 Created: 2008-05-15 Last updated: 2017-12-11Bibliographically approved
    3. Biphasic hormonal responses to the adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE in human cells
    Open this publication in new window or tab >>Biphasic hormonal responses to the adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE in human cells
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    2010 (English)In: Toxicology and Applied Pharmacology, ISSN 0041-008X, E-ISSN 1096-0333, Vol. 242, no 3, p. 281-289Article in journal (Refereed) Published
    Abstract [en]

    The DDT metabolite 3-methylsulfonyl-DDE (3-MeSO(2)-DDE) has been proposed as a lead compound for an improved adrenocortical carcinoma (ACC) treatment. ACC is a rare malignant disorder with poor prognosis, and the current pharmacological therapy o,p'-DDD (mitotane) has limited efficacy and causes severe adverse effects. 3-MeSO(2)-DDE is bioactivated by cytochrome P450 (CYP) 11B1 in mice and causes formation of irreversibly bound protein adducts, reduced glucocorticoid secretion, and cell death in the adrenal cortex of several animal species. The present study was carried out to assess similarities and differences between mice and humans concerning the adrenocorticolytic effects of 3-MeSO(2)-DDE. The results support previous indications that humans are sensitive to the adrenocorticolytic actions of 3-MeSO(2)-DDE by demonstrating protein adduct formation and cytotoxicity in the human adrenocortical cell line H295R. However, neither the irreversible binding nor the cytotoxicity of 3-MeSO(2)-DDE in H295R cells was inhibited by the CYP11B1 inhibitor etomidate. We also report biphasic responses to 3-MeSO(2)-DDE in cortisol and aldosterone secretion as well as in mRNA levels of the steroidogenic genes StAR, CYP11B1 and CYP11B2. Hormone levels and mRNA levels were increased at lower concentrations of 3-MeSO(2)-DDE, while higher concentrations decreased hormone levels. These biphasic responses were not observed with o,p'-DDD or with the precursor DDT metabolite p,p'-DDE. Based on these results, 3-MeSO(2)-DDE remains a viable lead compound for drug design, although the adrenocorticolytic effects of 3-MeSO(2)-DDE in human cells seem more complex than in murine cells.

    Keywords
    Adrenocorticolytic DDT metabolites, Endocrine disruption, Adrenocortical cancer (ACC), Biphasic responses, Steroidogenesis, H295R
    National Category
    Pharmacology and Toxicology
    Research subject
    Ecotoxicology
    Identifiers
    urn:nbn:se:uu:diva-112583 (URN)10.1016/j.taap.2009.10.018 (DOI)000273832500006 ()19900470 (PubMedID)
    Available from: 2010-01-15 Created: 2010-01-15 Last updated: 2018-01-12
    4. Chiral effects in adrenocorticolytic action of o,p'-DDD (mitotane) in human adrenal cells
    Open this publication in new window or tab >>Chiral effects in adrenocorticolytic action of o,p'-DDD (mitotane) in human adrenal cells
    2010 (English)In: Xenobiotica, ISSN 0049-8254, E-ISSN 1366-5928, Vol. 40, no 3, p. 177-183Article in journal (Refereed) Published
    Abstract [en]

    Adrenocortical carcinoma (ACC) is a rare malignant disease with poor prognosis. The main pharmacological choice, o,p'-DDD (mitotane), produces severe adverse effects. Since o,p'-DDD is a chiral molecule and stereoisomers frequently possess different pharmacokinetic and/or pharmacodynamic properties, we isolated the two o,p'-DDD enantiomers, (R)-(+)-o,p'-DDD and (S)-(-)-o,p'-DDD, and determined their absolute structures. The effects of each enantiomer on cell viability and on cortisol and dehydroepiandrosterone (DHEA) secretion in the human adrenocortical cell line H295R were assessed. We also assayed the o,p'-DDD racemate and the m,p'- and p,p'-isomers. The results show small but statistically significant differences in activity of the o,p'-DDD enantiomers for all parameters tested. The three DDD isomers were equally potent in decreasing cell viability, but p,p'-DDD affected hormone secretion slightly less than the o,p'- and m,p'-isomers. The small chiral differences in direct effects on target cells alone do not warrant single enantiomer administration, but might reach importance in conjunction with possible stereochemical effects on pharmacokinetic processes in vivo.

    National Category
    Pharmaceutical Sciences Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-112582 (URN)10.3109/00498250903470230 (DOI)000274882900002 ()20044879 (PubMedID)
    Available from: 2010-01-15 Created: 2010-01-15 Last updated: 2018-01-12
  • 102.
    Asplund, Basse
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry.
    Biodegradable Thermoplastic Elastomers2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A novel strategy for synthesising segmented poly(urethane urea) (PUU) without using a chain extender but nevertheless with the opportunity to vary the hard segment content has been developed. The strategy is based on amine formation from isocyanate upon reaction with water. By adding a dissolved soft segment to an excess of diisocyanate followed by the addition of water in the gas phase, amines are formed in situ. Urea linkages are then formed when these amines react with the excess of isocyanate groups. The gas phase addition facilitates addition in a slow and continuous manner. The hard segment content can easily altered by varying the diisocyanate/soft segment ratio. Even though the strategy is shown to be applicable to different diisocyanates, the focus has been on the potentially biodegradable methyl-2,6-diisocyanatehexanoate (LDI) and 1.4-butanediisocyanate (BDI) and various well known biodegradable polyesters and polycarbonates.

    All the synthesised materials exhibited pronounced phase separation and hydrogen bonding within the hard domains. However, a major increase in hydrogen bonding strength was seen when a symmetric diisocyanate was used instead of an asymmetric. Based on FTIR measurements, PUUs with BDI and a polydisperse hard segment can exhibit the same degree of phase separation and hydrogen bonding as the monodisperse product.

    The elastic properties of this new group of PUUs were exceptional with an elongation at break from 1600% to almost 5000% and the elastic modulus could be varied from a few MPa up to a couple of hundreds.

    Hydrolytic degradation was greater in the polyester-based than in the polycarbonate-based PUUs due to the more reactive ester bonds. Low mass loss but a considerable loss in molecular weight was seen in the polyester PUUs. The tensile strength decreased dramatically due to the loss of strain hardening.

    An MTT seeding assay using human fibroblasts and an in vivo biocompatibility study were performed and no signs of cytotoxicity were seen and the inflammatory response was comparable to other inert polymers.

    A biodegradable PUU with properties that can be tailored through an easy synthesis is here presented.

    List of papers
    1. Effect of hydrolysis on a new biodegradable co-polymer
    Open this publication in new window or tab >>Effect of hydrolysis on a new biodegradable co-polymer
    2006 In: Journal of biomaterials science. Polymer edition, ISSN 0920-5063, Vol. 17, no 6, p. 615-630Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-95332 (URN)
    Available from: 2007-01-08 Created: 2007-01-08Bibliographically approved
    2. Variable Hard Segment Length in Poly(urethane urea) through Excess of Diisocyanate and Vapor Phase Addition of Water
    Open this publication in new window or tab >>Variable Hard Segment Length in Poly(urethane urea) through Excess of Diisocyanate and Vapor Phase Addition of Water
    2006 In: Macromolecules, ISSN 0024-9297, Vol. 39, no 13, p. 4380-4385Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-95333 (URN)
    Available from: 2007-01-08 Created: 2007-01-08Bibliographically approved
    3. Synthesis of highly elastic biodegradable poly(urethane urea)
    Open this publication in new window or tab >>Synthesis of highly elastic biodegradable poly(urethane urea)
    2007 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 3, p. 905-911Article in journal (Refereed) Published
    Abstract [en]

    Linear poly(urethane urea) containing a biodegradable soft segment and a hard segment built solely from methyl-2,6-diisocyanatehexanoate (LDI) is presented, using a procedure where no chain extender is required. By having LDI in excess, together with a soft segment, and adding water in the vapor phase continuously creates amines in situ resulting in hard segments containing multiple LDI units linked via urea linkages. As soft segments, polymers of trimethylene carbonate (TMC) and copolymers of TMC, ε-caprolactone, and d,l-lactic acid (DLLA) were used. High inherent viscosity, 0.95−1.65 dL/g, was afforded even when DLLA-containing soft segments were used, which usually undergo aminolysis. With a hard segment content between 12% and 18%, all of the materials showed very high elongation at breakage, ranging from 1600% to 4700%, and an elastic modulus from 2.1 to 140 MPa. This one-pot synthesis is simple and has now been shown to be applicable to a large number of systems.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95334 (URN)10.1021/bm061058u (DOI)000244798600019 ()
    Available from: 2007-01-08 Created: 2007-01-08 Last updated: 2017-12-14Bibliographically approved
    4. In vitro degradation and in vivo biocompatibility study of a new linear poly(urethane urea)
    Open this publication in new window or tab >>In vitro degradation and in vivo biocompatibility study of a new linear poly(urethane urea)
    Show others...
    2008 (English)In: Journal of biomedical materials research. Part B: Applied biomaterials, ISSN 1552-4973, Vol. 86B, no 1, p. 45-55Article in journal (Refereed) Published
    Abstract [en]

    Segmented poly(urethane urea)s (PUUs) with hard segments derived only from methyl 2,6-diisocyantohexanoate (LDI) without the use of a chain extender have previously been described. These materials, which contain hard segments with multiple urea linkages, show exceptionally high strain capability (1600-4700%). In the study reported here, the rate and effect of hydrolysis of these materials were determined for gamma-sterilized and nonsterilized samples. Materials investigated contained PCL, PTMC, P(TMC-co-CL), P(CL-co-DLLA), or P(TMC-co-DLLA) as soft segments and, as well as their mechanical properties, changes in mass, inherent viscosity (IN.), and thermal properties were studied over 20 weeks. Results showed that the degradation rate was dependant on the soft segment structure, with a higher rate of degradation for the polyester-dominating PUUs exhibiting a substantial loss in IN. A tendency of reduction of tensile strength and strain hardening was seen for all samples. Also, loss in elongation at break was detected, for PUU-P(CL-DLLA) it went from 1600% to 830% in 10 weeks. Gamma radiation caused an initial loss in I.V. and induced more rapid hydrolysis compared with nonsterilized samples, except for PUU-PTMC. A cytotoxicity test using human fibroblasts demonstrated that the material supports cell viability. In addition, an in vivo biocompatibility study showed a typical foreign body reaction after I and 6 weeks.

    Keywords
    polyurethane, LDI, biodegradable, mechanical properties, hydrolysis
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95335 (URN)10.1002/jbm.b.30986 (DOI)000256891600006 ()
    Available from: 2007-01-08 Created: 2007-01-08 Last updated: 2009-10-30Bibliographically approved
    5. Pronounced phase separation for poly(urethane urea) with polydispersed multiple urea hard segments
    Open this publication in new window or tab >>Pronounced phase separation for poly(urethane urea) with polydispersed multiple urea hard segments
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:uu:diva-95336 (URN)
    Available from: 2007-01-08 Created: 2007-01-08 Last updated: 2010-01-13Bibliographically approved
  • 103.
    Asplund, Teo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Precise Image-Based Measurements through Irregular Sampling2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mathematical morphology is a theory that is applicable broadly in signal processing, but in this thesis we focus mainly on image data. Fundamental concepts of morphology include the structuring element and the four operators: dilation, erosion, closing, and opening. One way of thinking about the role of the structuring element is as a probe, which traverses the signal (e.g. the image) systematically and inspects how well it "fits" in a certain sense that depends on the operator.

    Although morphology is defined in the discrete as well as in the continuous domain, often only the discrete case is considered in practice. However, commonly digital images are a representation of continuous reality and thus it is of interest to maintain a correspondence between mathematical morphology operating in the discrete and in the continuous domain. Therefore, much of this thesis investigates how to better approximate continuous morphology in the discrete domain. We present a number of issues relating to this goal when applying morphology in the regular, discrete case, and show that allowing for irregularly sampled signals can improve this approximation, since moving to irregularly sampled signals frees us from constraints (namely those imposed by the sampling lattice) that harm the correspondence in the regular case. The thesis develops a framework for applying morphology in the irregular case, using a wide range of structuring elements, including non-flat structuring elements (or structuring functions) and adaptive morphology. This proposed framework is then shown to better approximate continuous morphology than its regular, discrete counterpart.

    Additionally, the thesis contains work dealing with regularly sampled images using regular, discrete morphology and weighting to improve results. However, these cases can be interpreted as specific instances of irregularly sampled signals, thus naturally connecting them to the overarching theme of irregular sampling, precise measurements, and mathematical morphology.

    List of papers
    1. Mathematical morphology on irregularly sampled data in one dimension
    Open this publication in new window or tab >>Mathematical morphology on irregularly sampled data in one dimension
    2017 (English)In: Mathematical Morphology - Theory and Applications, ISSN 2353-3390, Vol. 2, no 1, p. 1-24Article in journal (Refereed) Published
    National Category
    Computer Sciences
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-337288 (URN)10.1515/mathm-2017-0001 (DOI)
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2017-12-29 Created: 2017-12-21 Last updated: 2019-10-17Bibliographically approved
    2. Mathematical Morphology on Irregularly Sampled Signals
    Open this publication in new window or tab >>Mathematical Morphology on Irregularly Sampled Signals
    2017 (English)In: Computer Vision – ACCV 2016 Workshops. ACCV 2016, Springer, 2017, Vol. 10117, p. 506-520Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper introduces a new operator that can be used to approximate continuous-domain mathematical morphology on irregularly sampled surfaces. We define a new way of approximating the continuous domain dilation by duplicating and shifting samples according to a flat continuous structuring element. We show that the proposed algorithm can better approximate continuous dilation, and that dilations may be sampled irregularly to achieve a smaller sampling without greatly compromising the accuracy of the result.

    Place, publisher, year, edition, pages
    Springer, 2017
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 10117
    National Category
    Computer Sciences Computational Mathematics
    Identifiers
    urn:nbn:se:uu:diva-309921 (URN)10.1007/978-3-319-54427-4_37 (DOI)000426193700037 ()978-3-319-54427-4 (ISBN)978-3-319-54426-7 (ISBN)
    Conference
    13th Asian Conference on Computer Vision (ACCV), Taipei, Taiwan, November 20-24, 2016
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2016-12-08 Created: 2016-12-08 Last updated: 2019-10-17Bibliographically approved
    3. Mathematical Morphology on Irregularly Sampled Data Applied to Segmentation of 3D Point Clouds of Urban Scenes
    Open this publication in new window or tab >>Mathematical Morphology on Irregularly Sampled Data Applied to Segmentation of 3D Point Clouds of Urban Scenes
    Show others...
    2019 (English)In: International Symposium on Mathematical Morphology and Its Applications to Signal and Image Processing, 2019Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper proposes an extension of mathematical morphology on irregularly sampled signals to 3D point clouds. The proposed method is applied to the segmentation of urban scenes to show its applicability to the analysis of point cloud data. Applying the proposed operators has the desirable side-effect of homogenizing signals that are sampled heterogeneously. In experiments we show that the proposed segmentation algorithm yields good results on the Paris-rue-Madame database and is robust in terms of sampling density, i.e. yielding similar labelings for more sparse samplings of the same scene.

    National Category
    Signal Processing
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-388524 (URN)10.1007/978-3-030-20867-7_29 (DOI)978-3-030-20866-0 (ISBN)978-3-030-20867-7 (ISBN)
    Conference
    International Symposium on Mathematical Morphology (ISMM 2019)
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2019-07-01 Created: 2019-07-01 Last updated: 2019-10-17
    4. Adaptive Mathematical Morphology on Irregularly Sampled Signals in Two Dimensions
    Open this publication in new window or tab >>Adaptive Mathematical Morphology on Irregularly Sampled Signals in Two Dimensions
    (English)In: Article in journal (Refereed) Submitted
    National Category
    Signal Processing
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-395204 (URN)
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-10-25
    5. Estimating the Gradient for Images with Missing Samples Using Elliptical Structuring Elements
    Open this publication in new window or tab >>Estimating the Gradient for Images with Missing Samples Using Elliptical Structuring Elements
    (English)In: Article in journal (Refereed) Submitted
    National Category
    Signal Processing
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-395200 (URN)
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-10-25
    6. A Faster, Unbiased Path Opening by Upper Skeletonization and Weighted Adjacency Graphs
    Open this publication in new window or tab >>A Faster, Unbiased Path Opening by Upper Skeletonization and Weighted Adjacency Graphs
    2016 (English)In: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 25, no 12, p. 5589-5600Article in journal (Refereed) Published
    Abstract [en]

    The path opening is a filter that preserves bright regions in the image in which a path of a certain length L fits. A path is a (not necessarily straight) line defined by a specific adjacency relation. The most efficient implementation known scales as O(min(L, d, Q)N) with the length of the path, L, the maximum possible path length, d, the number of graylevels, Q, and the image size, N. An approximation exists (parsimonious path opening) that has an execution time independent of path length. This is achieved by preselecting paths, and applying 1D openings along these paths. However, the preselected paths can miss important structures, as described by its authors. Here, we propose a different approximation, in which we preselect paths using a grayvalue skeleton. The skeleton follows all ridges in the image, meaning that no important line structures will be missed. An H-minima transform simplifies the image to reduce the number of branches in the skeleton. A graph-based version of the traditional path opening operates only on the pixels in the skeleton, yielding speedups up to one order of magnitude, depending on image size and filter parameters. The edges of the graph are weighted in order to minimize bias. Experiments show that the proposed algorithm scales linearly with image size, and that it is often slightly faster for longer paths than for shorter paths. The algorithm also yields the most accurate results- as compared with a number of path opening variants-when measuring length distributions.

    Keywords
    graph theory, image filtering, transforms, 1D openings, H-minima transform, filter parameters, graph edges, grayvalue skeleton, image analysis, image filtering, image size, unbiased path opening, upper skeletonization, weighted adjacency graphs, Approximation algorithms, Gray-scale, Image edge detection, Length measurement, Periodic structures, Skeleton, Transforms, Path opening, granulometry, image analysis, length distribution, line segment, mathematical morphology, unbiased
    National Category
    Other Computer and Information Science
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-309087 (URN)10.1109/TIP.2016.2609805 (DOI)000388205100007 ()
    Funder
    Swedish Research Council, 2014-5983
    Available from: 2016-12-02 Created: 2016-12-02 Last updated: 2019-10-17Bibliographically approved
  • 104.
    Atluri, Rambabu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Novel Syntheses, Structures and Functions of Mesoporous Silica Materials2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The field of mesoporous silica has been studied for about 20 years but it is still an area attracting a lot of attention. The use of novel templating molecules and several issues related to the synthesis and fine structural details are still poorly understood. These aspects are of special relevance to the theme of this thesis, which includes novel work on three fronts; the synthesis, characterization and applications of mesoporous materials.

    The work described in this thesis aims to contribute to the mesoporous field by developing novel methods of mesoporous silica synthesis without relying on surfactant micelles as the templating agent but focusing instead on the stacking arrangement of aromatic molecules such as folic acid. The novel route presented here leads to 2D hexagonal structures with p6mm symmetry possessing high mesoporosity and large surface areas. The versatility of this route at various synthesis temperatures and using hydrothermal treatments has also been investigated.

    A novel strategy is also proposed for the synthesis of mesocaged materials with Pm3n symmetry structures. The mechanism relies on the penetration of the neutral propylamino moiety of a co-structure directing agent into the hydrophobic core of the surfactant micelles. Beside these novel pathways, the effect of hydrothermal treatment (HT) at 100 oC on the 3D cubic Ia3d structure (AMS-6) over a long period of time was also examined, and the results show a phase transformation from a 3D cubic Ia3d to a 2D hexagonal p6mm structure and a return to the 3D cubic Ia3d structure at a later stage in the synthesis. This unexpected result is discussed.

    In this work, the detailed structural characterization of mesoporous materials using electron microscopy techniques is an important task. In particular, to extend previous knowledge, the fine structural details of mesocaged materials possessing Pm3n symmetry prepared with various amphiphilic surfactants under acidic and alkaline conditions has been investigated using electron crystallography and sorption studies. The results show subtle fine structural differences with materials prepared under alkaline conditions exhibiting the largest mesocage sizes. The cage and window sizes are primarily determined by the charge density of the surfactant and the thickness of the hydration layer surrounding the surfactant micelles.

    The relationship between the mesoporous structure and its function has been investigated by evaluating the rate of release of amphiphilic molecules, used as model molecules, from the internal pore structures of mesoporous materials with different pore geometries. In a similar study, the rate of proton diffusion from a liquid surrounding the mesoporous nanoparticles into the pore system of AMS-n was also assessed. The results show that the diffusion coefficients for the proton absorption process are higher than those for the release of the surfactant template molecules, with more complex 3D mesocaged particles showing the highest diffusion coefficients in both cases.

    Finally, the quantity of CO2 adsorption was measured by modifying the internal surfaces of mesocaged material with n-propylamino groups. Results show that the cage-connecting window sizes limit the surface coverage of n-propylamino groups by pore blocking and affect the volume of CO2 adsorption. In addition, at the molecular level, CO2 adsorption shows physisorption or chemisorption depending on the localized distribution of n-propylamino groups, as studied by in-situ infrared spectroscopy.

    List of papers
    1. Structural variations in mesoporous materials with cubic Pm3n symmetry
    Open this publication in new window or tab >>Structural variations in mesoporous materials with cubic Pm3n symmetry
    2010 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 133, no 1-3, p. 27-35Article in journal (Refereed) Published
    Abstract [en]

    The fine structural details of mesoporous materials possessing Pm3n symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity-windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity-windows. Results support that whilst attainment of Pm3n cubic packing is due to the overall surfactant geometry, the formation of cavity-windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall.  The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.

    Keywords
    Amphiphilic surfactants, Mesoporous materials, Electron microscopy, Structural solutions, Gas separation
    National Category
    Materials Engineering
    Research subject
    Materials Science
    Identifiers
    urn:nbn:se:uu:diva-121984 (URN)10.1016/j.micromeso.2010.04.007 (DOI)000279061000004 ()
    Available from: 2010-04-06 Created: 2010-04-03 Last updated: 2017-12-12Bibliographically approved
    2. Nonsurfactant Supramolecular Synthesis of Ordered Mesoporous Silica
    Open this publication in new window or tab >>Nonsurfactant Supramolecular Synthesis of Ordered Mesoporous Silica
    2009 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 9, p. 3189-3191Article in journal (Refereed) Published
    Abstract [en]

    Hoogsteen-bonded tetrads and pentamers are formed by a large variety of organic molecules through H-donor and acceptor groups capable of inducing self-organization to form columnar and hexagonal mesophases. The biological importance of such macromolecular structures is exemplified by the assembly of guanosine-rich groups of telomere units and their implication in chromosomal replication. Folic acid is composed of a pterin group, chemically and structurally similar to guanine, conjugated to an l-glutamate moiety via a p-amino benzoic acid. Our aim has been to develop a delivery vehicle for folic acid and at the same time provide a novel synthetic route for ordered mesoporous materials without the use of amphiphilic surfactants. We present a new nonsurfactant route for the synthesis of highly ordered mesoporous materials, based on the supramolecular templating of stacked arrays of the tetramer-forming pterin groups of folic acid under a variety of synthetic conditions. This method leads to hexagonally ordered mesoporous structures with gyroid, spherical, and chiral morphologies with pores on the order of 25−30 Å in diameter and surface areas above 1000 m2/g. More importantly circular dichroism studies reveal that the folate template possesses a chiral signature within the pores in the as-synthesized solid and that chirality is transferred from the folate template to the pore surface via the aminopropyl triethoxysilane costructure directing agent used in the supramolecular assembly. This novel templating approach for ordered mesoporous materials breaks the hegemony of surfactant micellar systems for the preparation of these exciting high surface area solids and opens new opportunities for structural control, design of pore geometry, and novel applications.

    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Nanotechnology and Functional Materials
    Identifiers
    urn:nbn:se:uu:diva-99093 (URN)10.1021/ja8096477 (DOI)000264792400033 ()19220057 (PubMedID)
    Available from: 2009-03-06 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    3. Hydrothermal Phase Transformation of Bicontinuous Cubic Mesoporous Material AMS-6
    Open this publication in new window or tab >>Hydrothermal Phase Transformation of Bicontinuous Cubic Mesoporous Material AMS-6
    2008 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, no 12, p. 3857-3866Article in journal (Refereed) Published
    Abstract [en]

    The controlled synthesis of ordered anionic surfactant templated mesoporous silica with cubic Ia3 structure (AMS-6) is reported via prolonged periods of hydrothermal treatment (HT). The cubic Ia3 mesophase transforms to hexagonal p6mm after 8 days of HT at 100 °C. Surprisingly, the hexagonal phase is stable only for a limited period after which a reversal to the cubic Ia3 mesostructure is observed. Characterization methods such as powder X-ray diffraction (XRD), electron microscopy (SEM, TEM), N2-isotherms, magic-angle spinning (MAS) 29Si NMR spectroscopy, and thermogravimetric analysis (TGA) have been employed to follow structural and textural changes of the materials prepared. Data show that the resultant mesostructure and its textural properties are highly dependent on the period of HT with less unit-cell shrinkage on calcination after extensive HT. Furthermore, evidence of two different solid−solid phase mechanisms during HT is presented. The initial transition is consistent with a restructuring of the surfactant packing and a depletion of the organic moieties from the organo-silica wall as evident from 29Si NMR spectroscopy. The return to the bicontinuous cubic phase is driven by changes in charge matching at the organic−inorganic interface as a result of increases in the polymerization of the silica wall. The textural properties, and in particular the presence or absence of surface porosity, has been controlled through variations in hydrothermal treatment. These are associated with specific growth directions of cubic AMS-6 crystals. The synthetic method described allows us to easily prepare phase pure and intermediate mesostructured nanoparticles.

    National Category
    Other Materials Engineering
    Research subject
    Engineering Science with specialization in Nanotechnology and Functional Materials
    Identifiers
    urn:nbn:se:uu:diva-98531 (URN)10.1021/cm702440n (DOI)000256854800015 ()
    Available from: 2009-02-25 Created: 2009-02-25 Last updated: 2017-12-13Bibliographically approved
    4. Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials
    Open this publication in new window or tab >>Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials
    2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 5, p. 3189-3195Article in journal (Refereed) Published
    Abstract [en]

    The synthesis of cubic Pmn mesocaged solid templated by cetyltrimethyl ammonium bromide (C16TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C16TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pmn symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 Å) and ellipsoidal cages (B-cages, 48 × 43 Å) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 Å. Finally, a mechanism is proposed, denoted S+NoI, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pmn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.

    National Category
    Other Materials Engineering
    Research subject
    Engineering Science with specialization in Nanotechnology and Functional Materials
    Identifiers
    urn:nbn:se:uu:diva-99092 (URN)10.1021/la803727u (DOI)000263770800097 ()
    Available from: 2009-03-06 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    5. Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines
    Open this publication in new window or tab >>Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines
    2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 12, p. 10013-10024Article in journal (Refereed) Published
    Abstract [en]

    Adsorption-mediated CO2 separation can reduce the costs of carbon capture and storage. The reduction in cost requires adsorbents with high capacities for CO2 sorption and high CO2-over-N2 selectivity. Amine-modified sorbents are promising candidates for carbon capture. To investigate the details of CO2 adsorption in such materials, we studied mesocaged (cubic, Pm3n symmetry) silica adsorbents with tethered propylamines using Fourier transform infrared (FTIR) spectroscopy and volumetric uptake experiments. The degree of heterogeneity in these coatings was varied by either co-synthesizing or post-synthetically introducing the propylamine modification. In situ FTIR spectroscopy revealed the presence of both physisorbed and chemisorbed CO2 in the materials. We present the first direct molecular evidence for physisorption using FTIR spectroscopy in mesoporous silica sorbents modified with propylamines. Physisorption reduced the CO2-over-N2 selectivity in amine-rich sorbents. Samples with homogenous coatings showed typical CO2 adsorption trends and large quantities of IR-observable physisorbed CO2. The uptake of CO2 in mesocaged materials with heterogeneous propylamine coatings was higher at high temperatures than at low temperatures. At higher temperatures and low pressures, the post-synthetically modified materials adsorbed more CO2 than did the extracted ones, even though the surface area after modification was clearly reduced and the coverage of primary amine groups was lower. The principal mode of CO2 uptake in post-synthetically modified mesoporous silica was chemisorption. The chemisorbed moieties were present mainly as carbamate–ammonium ion pairs, resulting from the quantitative transformation of primary amine groups during CO2 adsorption as established by NIR spectroscopy. The heterogeneity in the coatings promoted the formation of these ion pairs. The average propylamine–propylamine distance must be small to allow the formation of carbamate–propylammonium ion pairs.

    Keywords
    carbon dioxide, propylamine, adsorption, IR, FTIR, silica, mesoporous
    National Category
    Materials Engineering
    Research subject
    Materials Science
    Identifiers
    urn:nbn:se:uu:diva-121987 (URN)10.1021/la1001495 (DOI)000278427600114 ()
    Available from: 2010-04-06 Created: 2010-04-03 Last updated: 2017-12-12Bibliographically approved
    6. Sustained Release from Mesosporous Nanoparticles: evaluation of structural properties associated with controlled release rate
    Open this publication in new window or tab >>Sustained Release from Mesosporous Nanoparticles: evaluation of structural properties associated with controlled release rate
    2008 (English)In: Current Drug Delivery, ISSN 1567-2018, E-ISSN 1875-5704, Vol. 5, no 3, p. 177-185Article in journal (Refereed) Published
    Abstract [en]

    We present here a detailed study of the controlled release of amino acid derived amphiphilic molecules from the internal pore structure of mesoporous nanoparticle drug delivery systems with different structural properties; namely cubic and hexagonal structures of various degrees of complexity. The internal pore surface of the nanomaterials presented has been functionalised with amine moieties through a one pot method. Release profiles obtained by Alternating Ionic Current measurements are interpreted in terms of specific structural and textural parameters of the porous nanoparticles such as pore geometry and connectivity. Results indicate that diffusion coefficients are lower by as much as four orders of magnitude in 2-dimensional structures in comparison to 3-dimensional mesoporous solids. A fast release in turn is observed from mesocaged materials AMS-9 and AMS-8 where the presence of structural defects is thought to lead to a slightly lower diffusion coefficient in the latter. Amount of pore wall functionalisation and number of binding sites on the model drug are found to have little effect on the drug release rate.

    National Category
    Nano Technology
    Research subject
    Engineering Science with specialization in Nanotechnology and Functional Materials
    Identifiers
    urn:nbn:se:uu:diva-17498 (URN)10.2174/156720108784911686 (DOI)18673261 (PubMedID)
    Available from: 2008-08-07 Created: 2008-08-07 Last updated: 2017-12-08Bibliographically approved
    7. Proton Absorption in As-Synthesized Mesoporous Silica Nanoparticles as a Structure-Function Relationship Probing Mechanism
    Open this publication in new window or tab >>Proton Absorption in As-Synthesized Mesoporous Silica Nanoparticles as a Structure-Function Relationship Probing Mechanism
    Show others...
    2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 8, p. 4306-4310Article in journal (Refereed) Published
    Abstract [en]

    A new method to investigate the effect of pore geometry on diffusion processes in mesoporous silica nanoparticles and other types of micro- and mesoporous structures is put forward. The method is based onthe study of proton diffusion from a liquid surrounding the mesoporous particles into the particle pore system. The proton diffusion properties are assessed for a variety of as-synthesized mesoporous nano- and microparticles with two-dimensional and three-dimensional connectivity. Results show that the diffusion coefficients are higher for the proton absorption process than for the release of surfactant template molecules, and that they overall follow the same trend with the more complex three-dimensional mesocaged particles showing the highest diffusion coefficients. The pore geometry (cylindrical pores versus cage-type pores) and structure connectivity are found to play a key role for the effects observed. The results put forward in the present work should offer a valuable tool in the development of porous nanomaterials in a range of applications including the use as catalysis and separation enhancers in the petrochemical industry, as scaffolds for hydrogen storage, and as drug delivery vehicles for sustained release and gene transfection.

    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Nanotechnology and Functional Materials
    Identifiers
    urn:nbn:se:uu:diva-100974 (URN)10.1021/la900105u (DOI)000265281700015 ()19281159 (PubMedID)
    Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2017-12-13Bibliographically approved
  • 105.
    Atthoff, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Tailoring of Biomaterials using Ionic Interactions: Synthesis, Characterization and Application2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The interactions between polymers and components of biological systems are an important area of interest within the fields of tissue engineering, polymer chemistry, medicine and biomaterials. In order to create such a biomimetic material, it must show the inherent ability to reproduce or elicit a biological function. How do we design synthetic materials in order to direct their interactions with biological systems?

    This thesis contributes to this research with aspects of how polymers interact with biological materials with the help of ionic interactions. Polyesters, biodegradable or not, may after a hydrolytic cleavage interact ionically with protonated amines by the liberated carboxylate functions. Amines are found in proteins and this fact will help us to anchor proteins to polyester surfaces. Another type of interaction is to culture cells in polymeric materials, i.e. scaffolds. We have been working on compliant substrates, knitted structures, to allow cell culture in three dimensions. A problem that arises here is how to get a high cell seeding efficiency? By working on the interactions between polymers, proteins and finally cells, it is possible to create a polarized protein membrane that allows for very efficient cell seeding, and subsequent three dimensional cell cultures. Finally a synthetic route to taylor interaction was developed. Here a group of polymers known as ionomers were synthesized. In our case ionic end groups have been placed onto biodegradable polycarbonates, we have created amphiphilic telechelic ionomers. Functionalization, anionic or cationic, changes the properties of the material in many ways due to aggregation and surface enrichment of ionic groups. It is possible to add functional groups for a variety of different interactions, for example introducing ionic groups that interact and bind to the complementary charge of proteins or on the other hand one can chose groups to prevent protein interactions, like the phosphorylcholine zwitterionomers. Such interactions can be utilized to modulate the release of proteins from these materials when used in protein delivery applications. The swelling properties, Tg, degradation rate and mechanical properties are among other things that will easily be altered with the choice of functional groups or backbone polymer.

    List of papers
    1. Protein adsorption onto polyester surfaces: Is there a need for surface activation?
    Open this publication in new window or tab >>Protein adsorption onto polyester surfaces: Is there a need for surface activation?
    2007 (English)In: Journal of Biomedical Materials Research - Part B Applied Biomaterials, ISSN 1552-4973, Vol. 80, no 1, p. 121-130Article in journal (Refereed) Published
    Abstract [en]

    Surface hydrolysis of polyester scaffolds is a convenient technique suggested to promote protein adsorption for improving cell attachment. We have, therefore, investigated the effect of hydrolysis of polyester surfaces for protein adsorption to clarify the conditions needed. Three polyesters, poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), and poly(glycolic acid) (PGA), were selected. Adsorption was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and quartz crystal microbalance (QCM). Hydrolyzed PET adsorbed significantly more proteins than nonhydrolyzed. Degradable polymers adsorbed at higher rates when the polymers were hydrolyzed prior to adsorption, but the same amount as noehydrolyzed, suggesting spontaneous hydrolysis during the adsorption. XPS shows that hydrolysis prior to absorption for PET results in a surface nitrogen composition of ∼14%, similar to pure protein (16%). Nonhydrolyzed PET surfaces showed only ∼7% nitrogen, indicating protein layers thinner than ∼10 nm. Adsorption to PLA and PGA shows nitrogen contents of 14-15% in both cases. SEM revealed striking differences in morphology of the protein coating. Hydrolyzed or spontaneously hydrolyzable surfaces display a pronounced fibrous structure while nonhydrolyzed surfaces give smooth structures. In combination, the results show that surface hydrolysis increase adsorption rate, but not the amount of proteins on polyesters that degrades in vivo. Surface treatment of nondegradable polyester increases the total amount of proteins and induces the formation of fibrous protein structures. Post hydrolysis treatment by acetic acid, replacing the counter-ion to a proton, further enhances protein attachment. Finally, cell attachment experiments verifies that protein adsorption increase the cell attachment to polyester surfaces.

    Keywords
    Poly(ethylene terephtalate), Poly(glycolic acid), Poly(lactic acid), Protein adsorption, Surface modification, Surface treatment
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-94592 (URN)10.1002/jbm.b.30576 (DOI)000243018200015 ()16680692 (PubMedID)
    Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2011-02-22Bibliographically approved
    2. Polarized protein membrane for high cell seeding efficiency
    Open this publication in new window or tab >>Polarized protein membrane for high cell seeding efficiency
    2007 (English)In: Journal of Biomedical Materials Research - Part B Applied Biomaterials, ISSN 1552-4973, Vol. 83, no 2, p. 472-480Article in journal (Refereed) Published
    Abstract [en]

    A new type of scaffold for tissue engineering was developed to give enhanced cell seeding in three dimensions. A gradient of either collagen or fibrin protein was prepared, supported by a knitted poly(ethylene terephtalate) PET fabric. The membranes were, after hydrolysis and acetic acid wash, submerged in a protein solution for adsorption followed by immersion into a gelling agent. The immediate contact between the protein solution held by the fabric and the gelling agent resulted in a dense, fibrous protein network with pore sizes around 0.5 μm at the surface, and larger pores of 10-50 μm size throughout the interior of the fabric as observed by scanning electron microscopy. By separating the fabric double layers holding this network, a gradient porosity membrane was produced. To evaluate the fractions of cells trapped in the matrix upon seeding, i.e. the seeding efficiency, 500 μl 3T3 fibroblasts cell suspension containing one million cells was seeded by filtering through the gradient protein membrane. For both the collagen and fibrin membranes, the seeding efficiency was ∼93%, which was significantly higher than that of 28% from the corresponding PET fabric without protein immobilization. Attempt to seed cells from the dense side of the protein networks resulted in no cell penetration into the scaffold. Histology on subsequent culture of the cells in the scaffold demonstrated viability and proliferation in three dimensions throughout the scaffold. This new and simple way of producing scaffolds play an important role when the cells are precious or scarce and cell seeding in three dimensions is important.

    Keywords
    Cell adhesion, Membrane, Protein adsorption, Scaffold
    National Category
    Biological Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-94593 (URN)10.1002/jbm.b.30819 (DOI)000250425400024 ()17443668 (PubMedID)
    Available from: 2006-05-17 Created: 2006-05-17 Last updated: 2011-01-20Bibliographically approved
    3. Biodegradable Ionomers
    Open this publication in new window or tab >>Biodegradable Ionomers