Recent Advances in Designing Electroconductive Biomaterials for Cardiac Tissue Engineering

Abstract

Implantable cardiac patches and injectable hydrogels are among the most promising therapies for cardiac tissue regeneration following myocardial infarction. Incorporating electrical conductivity into these patches and hydrogels is found to be an efficient method to improve cardiac tissue function. Conductive nanomaterials such as carbon nanotube, graphene oxide, gold nanorod, as well as conductive polymers such as polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate are appealing because they possess the electroconductive properties of semiconductors with ease of processing and have potential to restore electrical signaling propagation through the infarct area. Numerous studies have utilized these materials for regeneration of biological tissues that possess electrical activities, such as cardiac tissue. In this review, recent studies on the use of electroconductive materials for cardiac tissue engineering and their fabrication methods are summarized. Moreover, recent advances in developing electroconductive materials for delivering therapeutic agents as one of emerging approaches for treating heart diseases and regenerating damaged cardiac tissues are highlighted.

Keywords: cardiac patches; cardiac regeneration; conductivity; drug delivery; injectable hydrogels.

Figure 1.. Electroconductive biomaterials designed for cardiac tissue engineering.

Examples of the biomaterials used for MI repair including: conductive agents such as conductive polymers (e.g. PANI, PPy), gold- and carbon- based nanomaterials, ionic liquids, conductive metal (oxide) NPs and nanowires, and therapeutic agents such as siRNA, miRNA, growth factors, and small molecule inhibitors (e.g. 3i-1000), incorporated in hydrogel/polymer scaffolds (e.g. GelMA, PEG, PCL); and strategies used to apply biomaterials for cardiac tissue regeneration including: injectable hydrogels, and cardiac patches produced by different methods such as molding, 3D printing, electrospinning, and transplanted into the damaged area in the heart. Created with BioRender.com Abbreviations: 3D: three-dimensional; GelMA: gelatin methacryloyl; MI: myocardial infarction; miRNA; micro ribonucleic acid; NPs: nanoparticles; PANI: polyaniline; PCL: polycaprolactone; PEG: polyethylene glycol; PPy: polypyrrole; siRNA: small interfering ribonucleic acid.

Figure 2.. Examples of electroconductive and electrospun cardiac patches used for MI repair.

(A) Engineering cardiac patches containing an AF layer and an EH layer; (i) Diagram summarizing the experimental procedure for in vivo implantation of the cardiac patches in an MI mouse heart model. The patches were glued to the left ventricular wall, using fibrin glue, (ii) Representative macro images of an AuNPs-containing cardiac patch, (iii) FAC during 35 days post-MI in mice treated with different samples, (iv) LVEF over time after treatment in MI mice (Implantation took place at day 7 post-MI). Experimental groups included nontreated animals (control), EH, EH + AF, and EH + AF-AuNPs, (v) Representative images of Masson-Trichrome staining of the mice hearts at day 28 post-implantation. Reproduced with permission.^[47a] Copyright 2018, ACS applied materials & interfaces. (B) Engineering cardiac patches using electrospun GelMA fibrous sheet and Bio-IL; (i) Schematic illustration of the cardiac patch preparation, (ii) standard wound closure test using rat heart to test the adhesion strength of GelMA/Bio-IL cardiac patches, (iii) schematic illustration of interaction between cardiac tissue and engineered patches containing acrylated Bio-IL, (iv) quantification of the tissue adhesion strength of cardiac patches fabricated with 10% (w/v) GelMA and varying concentrations of acrylated Bio-IL on heart tissue, (v) electrical conductivity of cardiac patches fabricated with varying GelMA and Bio-IL concentrations, demonstrating the electrical conductivity of patches increased by increasing acrylated Bio-IL concentrations. Reproduced with permission.^[43a] Copyright 2019, Biomaterials. Abbreviations: AF: aligned Col fiber; AuNPs: gold nanoparticles; Bio-IL: bio-ionic liquid; EH: elastic hydrogel; FAC: Fractional area change; GelMA: gelatin methacryloyl; LVEF: left ventricular ejection fraction; MI: myocardial infarction.

Figure 3.. Examples of 3D printed electroconductive cardiac patches for MI repair.

(A) Engineering cardiac patches designed by using G-GNR/GelMA and Alg bioink; (i) Schematic illustration of the 3D bioprinting process, (ii) Printability of different Alg concentrations and different CaCl₂ concentrations (the concentrations of GelMA and G-GNRs were kept as 7% (w/v) and 0.1 mg/mL, respectively), (iii) Live/dead assay of CFs grown within G-GNR nanocomposite bioink printed constructs after printing with different extrusion speed (*P<0.05) (iv) Rheological characterization of 7% (w/v) GelMA prepolymer solution, GelMA/Alg bioink (7% (w/v) GelMA, 2% (w/v) Alg), and G-GNR nanocomposite bioink (0.1 mg/mL G-GNR, 7% (w/v) GelMA, 2% (w/v) Alg). Reproduced with permission.^[59] Copyright 2017, Adv Funct Mater. (B) Engineering 3D printing conductive (Ti₃C₂T_x) MXene in pre-designed patterns on PEG hydrogels using an aerosol jet printing; (i) Schematic illustration of the 3D printing process as well as a representative Live/dead image from the stem cell-derived CMs on Hilbert’s curve pattern, (ii) Live cell percentage on days 2, 4 and 7 after seeding the Ti₃C₂Tx MXene-PEG composite hydrogels, (iii) Quantification for the western blotting for the expressions of MYH7, SERCA2, GJA1, and TNNT2 proteins (n = 2). Reproduced with permission.^[37] Copyright 2020, Acta biomaterialia. Abreviations: 3D: three-dimensional; Alg: alginate; CaCl₂: calcium chloride; CFs: cardiac fibroblasts; CMs: cardiomyocytes; GelMA: gelatin methacryloyl; G-GNR/GelMA: GelMA coated GNR incorporated GelMA; GJA1: gap junction alpha-1; GNR: gold nanorod; MYH7: beta myosin heavy chain 7; PEG: polyethylene glycol; SERCA2: sarco/endo plasmic reticulum calcium ATPase 2; Ti₃C₂T_x: titanium carbide; TNNT2: cardiac troponin T type 2.

Figure 4.. Examples of injectable and electroconductive hydrogels for cardiac tissue engineering.

(A) Coadministration of a conductive and adhesive hydrogel patch composed of GelDA and DA-PPy and an injectable hydrogel made of HA-CHO and HHA to the infarcted myocardium; (i) A schematic showing the preparation/applying process, (ii) Gelation time for hydrogels, (iii) Rheological analysis of hydrogels in a time-sweep mode at 37 °C. Reproduced with permission.^[68] Copyright 2019, ACS applied materials & interfaces. (B) Engineering of a thermosensitive conductive hydrogel using CS and AuNPs; (i) Schematic illustration of the hydrogel preparation and in vitro seeding, (ii) Images of the CS solution (left) and gel (right) following a change in temperature, (iii) Gelation time assessment based on the test-tube-inverting method (n= 3, *P<0.05, ***P<0.001), (iv) Four-point probe conductivity of CS hydrogel that contained different concentrations of AuNPs (n = 3, ***P<0.001). AuNPs/CS (% w/w) = 0, 0.5, 1, and 1.5 in CS, CS-1AuNP, CS-2AuNP, and CS-3AuNP respectively. Reproduced with permission.^[70] Copyright 2016, Materials science & engineering C. Abbreviations: AuNPs: gold nanoparticles; CS: chitosan; DA-PPy: dopamine functionalized polypyrrole; GelDA: dopamine-gelatin; HA-CHO: oxidized sodium hyaluronic acid; HHA: hydrazided hyaluronic acid.

Figure 5.. Examples of electroconductive patches for delivery of therapeutic agents for MI repair.

(A) An injectable conductive hydrogel developed for delivery of plasmid DNA-eNOs and ADSCs for MI treatment; (i) Schematic demonstrating the conception to construct a conductive injectable hydrogel, which was employed to load plasmid DNA-eNOs NPs and ADSCs to treat myocardial infarction, (ii) NOx concentration in a 4 week time period in normal and MI hearts, and in the MI hearts with TA-PEG/HA-SH/ADSCs/Gene hydrogel treatment, (iii) The expression of mRNA of eNOs characterized by qRT-PCR in a 4 week time period in normal and MI hearts, and in the MI hearts with TA-PEG/HA-SH/ADSCs/Gene hydrogel treatment. Reproduced with permission.^[88] Copyright 2018, Journal of Biomaterials. (B) Conductive H₂S-releasing hydrogel encapsulating ADSCs for myocardial infarction treatment; (i) A schematic presenting the ADSC-loaded conductive H₂S releasing hydrogel for damaged cardiac treatment; (ii) H₂S-releasing profile in vitro, (iii) sulfide concentration of the cardiac tissue in the MI area. Reproduced with permission.^[89] Copyright 2019, ACS applied materials & interfaces. (C) PPy incorporated PAM/CS IPN loaded with dexamethasone; (i) A schematic of the synthesis process of PAM/CS IPN, (ii) the role of electrostimulation on the Dexamethasone release, (iii) Releasing of the dexamethasone by the redox process when the negative potential was applied. Reproduced with permission.^[93] Copyright 2018, ACS applied materials & interfaces. (D) Engineering of CNTs integrated MN patch; (i) Schematic illustration of applying the engineered patches on the infarcted myocardium, (ii) Confocal laser scanning microscope image of the aligned hiPSC-derived CMs cultured on the conductive MN array patch (Scale bars: 20 μm), (iii) The beating performance of the cells cultured on the conductive patch. Reproduced with permission.^[94] Copyright 2021, Chemical Engineering Journal. Abbreviations: ADSCs: adipose-derived stem cells; CNTs: carbon nanotubes; DNA-eNOs: deoxyribonucleic acid- endothelial nitric oxide synthase; HA-SH: Thiol modified hyaluronic acid; H₂S: hydrogen sulfide; hiPSC-derived CMs: human induced pluripotent stem cell derived cardiomyocytes; MI: myocardial infarction; MN: integrated microneedle; NPs: Nanoparticles; PAM/CS IPN: polyacrylamide/chitosan interpenetrating hydrogels; PEGDA: poly(ethylene glycol) diacrylate; PPy: polypyrrole; qRT-PCR: Quantitative Reverse Transcription-Polymerase Chain Reaction; TA: Tetraaniline.