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Advances in bioelectronic interfaces through controlled polymerization of tri-thiophene monomers
Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-5277-3705
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the domain of conventional electronics which are integrated into our daily lives, electrons predominantly serve as charge carriers. In contrast, biological systems primarily utilize ions and molecules of various sizes for signal transmission. This communication gap has been effectively bridged by the advent of conducting and semiconducting organic polymers, which uniquely exhibit combined electronic and ionic conductivity. These materials have become invaluable in translating signals between electronic and biological systems, giving rise to the field of organic bioelectronics. This field now offers a flexible platform that develops tools for biological recording and regulation, with potential applications extending from life sciences to clinical applications.   

This thesis explores advancements in organic bioelectronics, focusing on the development of organic electrochemical transistors (OECTs) based on conducting polymers and the development of organic conductors composed of conductive hydrogels, through controlled polymerization of tri-thiophene monomers.  

We began by investigating the electrically driven polymerization of the water-soluble tri-thiophene monomer called ETE-S. Our analysis demonstrates how alterations in monomer concentrations can affect the monomer aggregation in solution and the electrical properties of the resultant conducting polymer films, which are crucial for the potential development of neuromorphic devices and other bioelectronic applications. Additionally, we investigated the electrically driven copolymerization of the water-soluble tri-thiophene monomers with two distinct sidechains, including ETE-S and ETE-PC. This study demonstrated that the onset potential of electropolymerization process and threshold voltage of the resultant OECT devices can be influenced by regulating monomer blend ratios, thereby enhancing the functionality of OECTs for bioelectronic applications.  

Furthermore, enzymatic polymerization of a water-soluble tri-thiophene monomer ETE-S was employed to develop electrically conductive hydrogel-based organic conductors for interfacing with biological systems. We developed a novel method to fabricate cytocompatible and conductive hydrogels suitable for three-dimensional (3D) cell culture and 3D bioprinting. These conductive hydrogels possess tissue-like mechanical properties with mixed ionic and electronic conductivity, providing innovative strategies to utilize electrical signals to modulate cell behavior within a native-like microenvironment. To expand our understanding of electrophysiological applications, we also developed electrically conductive hydrogels using enzymatic polymerization of monomer ETE-S suitable for future electrophysiological applications. This conductive hydrogel is ionically crosslinked to enable liquid-to-gel transition that would dynamically conform to skin topographies, facilitating the accuracy and reliability of electrophysiological recordings.  

Overall, this thesis contributes to the field of organic bioelectronics by exploring the potential of OECTs for specialized bioelectronic applications and the development of conductive hydrogels for 3D cell culture and further electrophysiological recordings, achieved through controlled polymerization of tri-thiophene monomers. The findings provide a foundation for future research into advanced bioelectronic interfaces, which have the potential to enhance biomedical technologies and therapeutic methods. 

Abstract [sv]

Inom konventionell elektronik, som är integrerad i vårt dagliga liv, fungerar elektroner huvudsakligen som laddningsbärare. I biologiska system används däremot främst joner och molekyler av olika storlekar för signalöverföring. Denna kommunikationsklyfta har effektivt överbryggats genom tillkomsten av ledande och halvledande organiska polymerer, som på ett unikt sätt uppvisar kombinerad elektronisk och jonisk ledningsförmåga. Dessa material har blivit ovärderliga när det gäller att överföra signaler mellan elektroniska och biologiska system, vilket har gett upphov till området organisk bioelektronik. Detta område erbjuder nu en flexibel plattform som utvecklar verktyg för biologisk registrering och reglering, med potentiella tillämpningar som sträcker sig från biovetenskap till kliniska tillämpningar.   

Denna avhandling utforskar framsteg inom organisk bioelektronik, med fokus på utvecklingen av organiska elektrokemiska transistorer (OECTs) baserade på ledande polymerer och utvecklingen av organiska ledare bestående av ledande hydrogeler, genom kontrollerad polymerisation av tritiofenmonomerer.  

Vi började med att undersöka den elektriskt drivna polymerisationen av den vattenlösliga tritiofenmonomeren ETE-S. Vår analys visar hur förändringar i monomerkoncentrationer kan påverka monomeraggregeringen i lösning och de elektriska egenskaperna hos de resulterande ledande polymerfilmerna, vilket är avgörande för den potentiella utvecklingen av neuromorfiska enheter och andra bioelektroniska applikationer. Dessutom undersökte vi den elektriskt drivna sampolymerisationen av de vattenlösliga tritiofenmonomererna med två distinkta sidokedjor, inklusive ETE-S och ETE-PC. Denna studie visade att startpotentialen för elektropolymeriseringsprocessen och tröskelspänningen för de resulterande OECT-enheterna kan påverkas genom att reglera monomerblandningsförhållandena, vilket förbättrar funktionaliteten hos OECT för bioelektroniska applikationer.

Vidare användes enzymatisk polymerisation av en vattenlöslig tritiofenmonomer ETE-S för att utveckla ledande hydrogelbaserade organiska ledare för gränssnitt med biologiska system. Vi utvecklade en ny metod för att tillverka cytokompatibla och ledande hydrogeler som är lämpliga för tredimensionell (3D) cellkultur och 3D-bioprintning. Dessa ledande hydrogeler har vävnadsliknande mekaniska egenskaper med blandad jonisk och elektronisk ledningsförmåga, vilket ger innovativa strategier för att använda elektriska signaler för att modulera cellbeteende i en nativliknande mikromiljö. För att utöka möjligheten för elektrofysiologiska tillämpningar har vi också utvecklat en ledande hydrogel för framtids EEG och EKG tillämpningar med hjälp av enzymatisk polymerisering av monomeren ETE-S. Denna ledande hydrogel är joniskt tvärbunden för att möjliggöra vätska-till-gel-övergång för att dynamiskt anpassa sig till hudtopografier, vilket underlättar noggrannheten och tillförlitligheten hos elektrofysiologiska inspelningar.  

Sammantaget bidrar denna avhandling till området organisk bioelektronik genom att utforska potentialen hos OECTs för specialiserade bioelektroniska applikationer och utvecklingen av ledande hydrogeler för 3D-cellkultur och elektrofysiologiska registreringar, uppnådda genom kontrollerad polymerisation av tritiofenmonomerer. Resultaten utgör en grund för framtida forskning om avancerade bioelektroniska gränssnitt, som har potential att förbättra biomedicinsk teknik och terapeutiska metoder.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2024. , p. 96
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2417
Keywords [en]
Organic Bioelectronics, Conducting Polymers, Conductive Hydrogels, Electropolymerization, Enzymatic Polymerization, Interface, Organic Electrochemical Transistors, Scaffolds, 3D Cell Culture, 3D Bioprinting, Electrophysiological Recordings
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:liu:diva-208729ISBN: 9789180758741 (print)ISBN: 9789180758758 (electronic)OAI: oai:DiVA.org:liu-208729DiVA, id: diva2:1907217
Public defence
2024-11-19, K1, Kåkenhus, Campus Norrköping, Norrköping, 10:00 (English)
Opponent
Supervisors
Available from: 2024-10-22 Created: 2024-10-22 Last updated: 2024-10-22Bibliographically approved
List of papers
1. Engineering Conductive Hydrogels with Tissue-like Properties: A 3D Bioprinting and Enzymatic Polymerization Approach
Open this publication in new window or tab >>Engineering Conductive Hydrogels with Tissue-like Properties: A 3D Bioprinting and Enzymatic Polymerization Approach
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2024 (English)In: SMALL SCIENCE, ISSN 2688-4046Article in journal (Refereed) Epub ahead of print
Abstract [en]

Hydrogels are promising materials for medical devices interfacing with neural tissues due to their similar mechanical properties. Traditional hydrogel-based bio-interfaces lack sufficient electrical conductivity, relying on low ionic conductivity, which limits signal transduction distance. Conducting polymer hydrogels offer enhanced ionic and electronic conductivities and biocompatibility but often face challenges in processability and require aggressive polymerization methods. Herein, we demonstrate in situ enzymatic polymerization of pi-conjugated monomers in a hyaluronan (HA)-based hydrogel bioink to create cell-compatible, electrically conductive hydrogel structures. These structures were fabricated using 3D bioprinting of HA-based bioinks loaded with conjugated monomers, followed by enzymatic polymerization via horseradish peroxidase. This process increased the hydrogels' stiffness from about 0.6 to 1.5 kPa and modified their electroactivity. The components and polymerization process were well-tolerated by human primary dermal fibroblasts and PC12 cells. This work presents a novel method to fabricate cytocompatible and conductive hydrogels suitable for bioprinting. These hybrid materials combine tissue-like mechanical properties with mixed ionic and electronic conductivity, providing new ways to use electricity to influence cell behavior in a native-like microenvironment. This study introduces a novel method to enhance hydrogel conductivity and biocompatibility for biomedical applications. By using in situ enzymatic polymerization of pi-conjugated monomers within a hyaluronan-based hydrogel bioink, followed by 3D bioprinting, the resulting hydrogels exhibit improved stiffness, electroactivity, and cytocompatibility. These conductive hydrogels provide a versatile platform for advanced 3D cell culture and neural engineering.image (c) 2024 WILEY-VCH GmbH

Place, publisher, year, edition, pages
WILEY, 2024
Keywords
3D printing; cell scaffold; conducting polymer; in vitro; polymerization
National Category
Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:liu:diva-207429 (URN)10.1002/smsc.202400290 (DOI)001303017000001 ()
Note

Funding Agencies|European Research Council (AdG 2018) [834677]; Swedish Research Council [2018-06197]; Swedish Foundation for Strategic Research [RMX18-0083]; Knut and Alice Wallenberg Foundation (KAW) [2021.0186]; Swedish Research Council [2022-04807, 2023-03651, 2023-05459]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoeping University [2009-00971]; Grant Agency of the Czech Republic [24-10775S]

Available from: 2024-09-09 Created: 2024-09-09 Last updated: 2024-10-22

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