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Collagen-Silver Nanowire Composites as Electrically Activeand Antibacterial Scaffolds for Embryonic Cardiac Cell Proliferation
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
Faculty of Medicine and Health, School of Health and Medical Sciences, Örebro University, Örebro, Sweden.
Department of Materials, Imperial College, London, UK.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Electroactive biomaterials are used in a number of applications, including scaffolds for neural and cardiac regeneration. Most electrodes and conductive scaffolds for tissue regeneration are based on synthetic materials that have limited biocompatibility and often display a large mismatch in mechanical properties with the surrounding tissue. In this work, we have developed a nanocomposite material prepared from self-assembled collagen and silver nanowires (AgNW) that display electrical properties analogous to electrodes used in the clinic. The AgNW concentration of the nanocomposites was optimized to stimulate proliferation of isolated embryonic cardiomyocytes. In addition, the AgNWs renders the nanocomposites antimicrobial against both Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis. The mechanical properties of the nanocomposites were further characterized in physiological conditions and showed a dynamic modulus within the lower kPa range, suitable for embryonic cardiomyocyte proliferation. An in depth electrochemical analysis of the materials in the wet state showed a charge storage capacity of 12.28 mC cm-2, and charge injection capacity of 0.33 mC cm-2, comparable to electrode materials, such as iridium oxide and polypyrrole, currently used for electrical stimulation of tissues. The collagen/AgNW composites are thus multifunctional structural scaffolds that promote embryonic cardiomyocyte function, with the ability to store and inject charges, along with providing antimicrobial resistance.

National Category
Clinical Medicine Basic Medicine Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-120770OAI: oai:DiVA.org:liu-120770DiVA: diva2:848294
Available from: 2015-08-24 Created: 2015-08-24 Last updated: 2015-08-24Bibliographically approved
In thesis
1. Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration
Open this publication in new window or tab >>Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nature has had millions of years to perfect the structural components of the human body, but has also produced the dysfunctions that result in the cancers and diseases, which ruin that perfection. Congenital heart defects, and myocardial infarction lead to scarring that remodels heart muscle, decreasing the contractility of the heart, with profound consequences for the host. Regenerative medicine is the study of strategies to return diseased body parts to their evolutionarily optimum structure.

Nature has had millions of years to perfect the structural components of the human body, but has also produced the dysfunctions that result in the cancers and diseases, which ruin that perfection. Congenital heart defects, and myocardial infarction lead to scarring that remodels heart muscle, decreasing the contractility of the heart, with profound consequences for the host. Regenerative medicine is the study of strategies to return diseased body parts to their evolutionarily optimum structure. Cells alone cannot develop into functional tissue, as they require mechanical support and chemical signals from the extracellular matrix in order to play the correct role in the body. In order to imitate the process of tissue formation optimized by nature, scaffolds are developed as the architectural support for tissue regeneration. To mimic the elasticity and strength seen in the heart muscle is one of the major scientific conundrums of our time. The development of new multifunctional materials for scaffolds is an accepted solution for repairing failing heart muscle. In this thesis I accept the notion that endogenous cardiac cells can play a major role in addressing this problem, if we can attract them to the site of defect or injury and make them proliferate. I then proceed to show how improving on a commonly used synthetic polymer was used to develop two new biomaterials.

Polycaprolactone (PCL) fibers and sheets were studied for their ability to adsorb proteins based on their surface energies. We found that although the wettability of the PCL might be similar to positive controls for cell attachment, the large differences in surface energies may account for the increased serum protein adsorption and limit cell adhesion. The effect of fiber morphology was then investigated with respect to proliferation of mesenchymal stem cells and cardiac progenitor cells. PCL was also mechanically enhanced with thiophene conjugated single walled carbon nanotubes (T-CNT); where small concentrations of the T-CNT allowed for a 2.5 fold increase in the percentage of elongation, while retaining the proliferation profile of the cardiac progenitor cells. Although PCL is a well-known implant material, the ability to attract and adhere cardiac cells was limited. Therefore we sought to develop new biomaterials with fiber morphologies similar to the muscle fiber of the heart, but with surface energies similar to positive controls for cell attachment. Poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) was then explored as a ribbon fiber and compared to collagen with embryonic cardiac cells, in vitro, and then implanted into rats for in vivo long term evaluations. The cardiac cells had a preferential adhesion to the TQ1 fibers, and in vivo, the fibers attracted more blood vessels and regrew functional tissue compared to the collagen controls. TQ1 fibers had the added ability to emit light in the near infrared region, which would allow for consistent tracking of the material. Although this material offered the morphological preference for the cardiac cells, it does not degrade and nor did it offer electrical conductivity. The heart muscle is an electrically active muscle. The dead tissue that is formed in the ischemic area loses its ability to  transfer the electrical signals. Hence, I have then developed collagen fibrous materials with silver nanowires to help store and inject charges that would be generated during the contraction of the heart muscle. The silver nanowires served to help carry charges whilst providing resistance to bacterial growth on the material. The collagen/silver nanowires composites were mechanically apt for the culture of embryonic cardiac cells.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 80 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1686
National Category
Physical Sciences Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-120773 (URN)10.3384/diss.diva-120773 (DOI)978-91-7519-021-1 (print) (ISBN)
Public defence
2015-08-28, Planck, Fysikhuset, Campus Valla, Linköping, 09:15 (English)
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Available from: 2015-08-24 Created: 2015-08-24 Last updated: 2015-10-02Bibliographically approved

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