Periodic Reporting for period 1 - HepEDOT (Conductive, self-doping and biodegradable oligoEDOT-heparin biomaterial for improved electromechanical coupling, cardiac cell retention and delivery of paracrine factors)
Reporting period: 2019-04-01 to 2021-03-31
Recent advances in the production of human cardiomyocyte surrogates, particularly those derived from induced-pluripotent stem cells (iPSC-cardiomyocytes), represented a game changer in the field of cell therapy for the treatment of cardiac injury, showing potential reduction in cardiomyocyte apoptosis and infarct size in pre-clinical infarct models. While iPSC-derived cardiomyocyte surrogates do not give rise to ethical concerns and closely resemble the physiology and function of mature cardiomyocytes, their electromechanical activity is still rudimentary. Therefore, the most evident clinical limitations observed in pre-clinical studies using cardiomyocyte surrogates are the absence of cardiac coupling with the host tissue and poor cell retention.
Previously, conductive materials have been used to attempt electrical coupling. Although there is no evidence yet for electrical coupling with cardiomyocytes, these have shown to interact electrically with the myocardial tissue. Also, their limited mechanical performance, biocompatibility and electrical stability need to be addressed to make these materials a feasible clinical approach for cardiac repair. The aim of this project was to achieve cardiomyocyte electrical coupling using conductive hydrogels as scaffolds for iPSC-cardiomyocyte implantation. Since the materials would be intended towards clinical use, I aimed to synthesize a biocompatible material and tune the mechanical properties of the hydrogel to match those of the myocardium. An important objective was to study the electrical properties and stability of the resulting material, followed by the development of an electro-stimulation device to pace and study the electrophysiology of cardiomyocytes interfacing the conductive material.
By the end of this action, a conductive biomaterial based on PEDOT-derivatives was developed, which can be easily injected and form hydrogels in the heart tissue. The mechanical and electrical properties of the material match those reported in the heart. The conductive hydrogels were biocompatible and were deemed to be a suitable material to facilitate pacing of iPSC-cardiomyocytes, compared to conventional hydrogel scaffolds. This project was performed in close collaboration with the British Heart Foundation at Imperial College London, and the outcomes of this project will advance this technology further into clinically relevant infarct models for the implantation of cardiomyocytes surrogates for the treatment of cardiac infarct.
Previously, conductive materials have been used to attempt electrical coupling. Although there is no evidence yet for electrical coupling with cardiomyocytes, these have shown to interact electrically with the myocardial tissue. Also, their limited mechanical performance, biocompatibility and electrical stability need to be addressed to make these materials a feasible clinical approach for cardiac repair. The aim of this project was to achieve cardiomyocyte electrical coupling using conductive hydrogels as scaffolds for iPSC-cardiomyocyte implantation. Since the materials would be intended towards clinical use, I aimed to synthesize a biocompatible material and tune the mechanical properties of the hydrogel to match those of the myocardium. An important objective was to study the electrical properties and stability of the resulting material, followed by the development of an electro-stimulation device to pace and study the electrophysiology of cardiomyocytes interfacing the conductive material.
By the end of this action, a conductive biomaterial based on PEDOT-derivatives was developed, which can be easily injected and form hydrogels in the heart tissue. The mechanical and electrical properties of the material match those reported in the heart. The conductive hydrogels were biocompatible and were deemed to be a suitable material to facilitate pacing of iPSC-cardiomyocytes, compared to conventional hydrogel scaffolds. This project was performed in close collaboration with the British Heart Foundation at Imperial College London, and the outcomes of this project will advance this technology further into clinically relevant infarct models for the implantation of cardiomyocytes surrogates for the treatment of cardiac infarct.
The following summarizes the main research tasks and results from this fellowship:
1. Novel conductive PEDOT-derivative polymers required for hydrogel fabrication were synthesized and characterized. I have studied the polymerization kinetics to determine the best conditions for high yield and purity.
2. Fabrication of conductive hydrogels was done using imine-based crosslinking to provide injectability. Hydrogels inherit optical and electrical properties of the PEDOT-derivatives. Gelation kinetics and mechanical properties of the conductive materials are similar to the original non-conductive hydrogel counterparts. Hydrogel gelation time can be tuned with both pH and concentration. Hydrogel stiffness can be tuned with polymer concentration.
3. The electrical properties of conductive hydrogels were studied. PEDOT-derivatives with short-chains (oligomers) have been found to be electroactive rather than conductive. PEDOT-derivatives with long-chain segments conferred hydrogels with conductive properties. In addition, hydrogels exhibited both ionic and electric conductivity, which were stable in physiological conditions.
4. These hydrogels were also shown to retain cardiac growth factors and cytokines. Loading and release studies showed efficient protein loading, in which the release ratio can be controlled by tuning the hydrogel composition and concentration. I studied the cardioprotective effects of cardiac conditioned media on injured cardiomyocytes. Released conditioned media was shown to mitigate cardiomyocyte apoptosis on injured cardiomyocytes. These preliminary results have been used for a British Heart Foundation (BHF) Grant application for further studies.
5. In vitro studies with iPSC-derived cardiomyocytes have shown that conductive hydrogels are non-cytotoxic and can be used for cell encapsulation, preserving cardiomyocyte viability and functionality. I have prototyped and fabricated in-house devices for electrostimulation of cardiomyocytes. Results showed that conductive hydrogels facilitated the pacing of iPSC-derived cardiomyocyte, compared to non-conductive hydrogels.
6. Preliminary testing of conductive hydrogels in vivo was done in rats to evaluate injectability and adhesion. This part of the study is being conducted in collaboration and with the funding support from the BHF Centre of Research Excellence at Imperial College. Conductive hydrogels can be placed onto the myocardium surface as a liquid mixture and turn into a gel in minutes. They adhere to the myocardium and stay there in presence of fluids, not requiring use of suture.
Research activities during this action were presented at international research conferences in the fields of Biomaterials and Tissue Engineering. I have published an article as first-author in Journal of Controlled Release and co-authored publications in Science Advances, Acta Biomaterialia and Journal of Materials Chemistry, which are available as open access and acknowledge MSCA funding. Two further first-author publications are in preparation for submission to high-impact journals for biomaterials and tissue engineering. Intellectual property of the developed technologies was evaluated and concluded that more data on the clinical application will be required for invention disclosure and patentable claims. During the funding period, I participated in outreach activities to disseminate my research to public audiences, including demonstrations for exhibitions, fundraiser events and festivals.
1. Novel conductive PEDOT-derivative polymers required for hydrogel fabrication were synthesized and characterized. I have studied the polymerization kinetics to determine the best conditions for high yield and purity.
2. Fabrication of conductive hydrogels was done using imine-based crosslinking to provide injectability. Hydrogels inherit optical and electrical properties of the PEDOT-derivatives. Gelation kinetics and mechanical properties of the conductive materials are similar to the original non-conductive hydrogel counterparts. Hydrogel gelation time can be tuned with both pH and concentration. Hydrogel stiffness can be tuned with polymer concentration.
3. The electrical properties of conductive hydrogels were studied. PEDOT-derivatives with short-chains (oligomers) have been found to be electroactive rather than conductive. PEDOT-derivatives with long-chain segments conferred hydrogels with conductive properties. In addition, hydrogels exhibited both ionic and electric conductivity, which were stable in physiological conditions.
4. These hydrogels were also shown to retain cardiac growth factors and cytokines. Loading and release studies showed efficient protein loading, in which the release ratio can be controlled by tuning the hydrogel composition and concentration. I studied the cardioprotective effects of cardiac conditioned media on injured cardiomyocytes. Released conditioned media was shown to mitigate cardiomyocyte apoptosis on injured cardiomyocytes. These preliminary results have been used for a British Heart Foundation (BHF) Grant application for further studies.
5. In vitro studies with iPSC-derived cardiomyocytes have shown that conductive hydrogels are non-cytotoxic and can be used for cell encapsulation, preserving cardiomyocyte viability and functionality. I have prototyped and fabricated in-house devices for electrostimulation of cardiomyocytes. Results showed that conductive hydrogels facilitated the pacing of iPSC-derived cardiomyocyte, compared to non-conductive hydrogels.
6. Preliminary testing of conductive hydrogels in vivo was done in rats to evaluate injectability and adhesion. This part of the study is being conducted in collaboration and with the funding support from the BHF Centre of Research Excellence at Imperial College. Conductive hydrogels can be placed onto the myocardium surface as a liquid mixture and turn into a gel in minutes. They adhere to the myocardium and stay there in presence of fluids, not requiring use of suture.
Research activities during this action were presented at international research conferences in the fields of Biomaterials and Tissue Engineering. I have published an article as first-author in Journal of Controlled Release and co-authored publications in Science Advances, Acta Biomaterialia and Journal of Materials Chemistry, which are available as open access and acknowledge MSCA funding. Two further first-author publications are in preparation for submission to high-impact journals for biomaterials and tissue engineering. Intellectual property of the developed technologies was evaluated and concluded that more data on the clinical application will be required for invention disclosure and patentable claims. During the funding period, I participated in outreach activities to disseminate my research to public audiences, including demonstrations for exhibitions, fundraiser events and festivals.
The results from this project have advanced the state-of-the-art in multiple areas of polymer chemistry and biomaterials. First, we have developed synthesis routes to produce new molecules and PEDOT-based polymers that possess distinct optical and electric properties. These syntheses can be done in situ on other pre-made hydrogels and solid scaffolds as well. These materials are highly processable and can be easily used in clinical settings as injectable and minimally invasive materials. The hydrogel has properties that no other conventional conductive materials offer, and are optimal for biomedical and clinical applications, including biocompatibility and compliant mechanical properties with soft tissues.
Compared to conventional conductive materials, where electrical conductivity predominates; the structural properties of PEDOT-based hydrogels provide the material with mixed ionic and electric conductivity. This has facilitated electrostimulation of cardiomyocytes, compared to conventional hydrogels. The improved efficiency in conductivity makes our PEDOT-based hydrogels promising materials for devices and electrodes in bioelectronic and clinical applications in multiple fields including cardiac, neural, soft-electronics and other electric-mediated therapies.
Compared to conventional conductive materials, where electrical conductivity predominates; the structural properties of PEDOT-based hydrogels provide the material with mixed ionic and electric conductivity. This has facilitated electrostimulation of cardiomyocytes, compared to conventional hydrogels. The improved efficiency in conductivity makes our PEDOT-based hydrogels promising materials for devices and electrodes in bioelectronic and clinical applications in multiple fields including cardiac, neural, soft-electronics and other electric-mediated therapies.