Figure 2. Synthesis and applications of ECHs formed by using conductive NPs.

Schematic for the formation of alginate hydrogels and gold nanowires (NW)-alginate ECHs. Cardiomyocytes are cultured in alginate hydrogels formed small clusters and beated asynchronously. However, cardiomyocytes cultured in alginate-NW ECHs formed organized cardiac-like tissue and beat synchronously. Components of engineered cardiac tissue are shown: cardiac cells (red), alginate pore walls (blue), NW (yellow) (a). Current/Potential graph of alginate hydrogels and alginate-NW ECHs showing higher electrical conductivity exhibited by the ECHs (b). Hematoxylin and eosin (H&E) staining images based on in vitro studies showed thick tissue in the NW-alginate ECHs (ci, cii), whereas the samples containing pure alginate showed non-continuous tissue separated by pore walls (di, dii). [57] Synthesis of ECHs by coating graphene oxide (GO) with methacryloyl-substituted tropoelastin (MeTro) (e). Elastic modulus of MeTro hydrogels and MeTro/GO ECHs demonstrating that the addition of GO significantly increases the elastic modulus (f). Torsion test on MeTro hydrogel and MeTro/GO ECH was conducted by twisting scaffolds for multiple rounds. Significant deformation was observed in MeTro hydrogel, however, MeTro/GO ECHs did not display any deformation (g). Overall impedance of MeTro hydrogels, MeTro/GO ECHs, and MeTro/reduced GO (rGO) ECHs shows that electrical resistance was the lowest for ECHs fabricated with rGO (h). [58] Schematic for the fabrication of CNT-embedded GelMA ECHs using dielectrophoresis force to align CNTs in GelMA. Highly aligned CNTs were observed in under 1 min, and the GelMA prepolymer was photocrosslinked using UV light (i). Young’s modulus of GelMA hydrogels, and ECHs containing GelMA and both randomly arranged and aligned CNTs. Results showed that the alignment of CNTs in GelMA-based ECHs resulted in a stiffer material as compared to ECHs fabricated with randomly dispersed CNTs (j). Electrical evaluation of these ECHs demonstrated that the incorporation of CNTs into hydrogels resulted in lower impedance compared to pristine GelMA hydrogels. Further the conductivity of these ECHs could be finely tuned by adjusting the concentration of CNTs in the system (k). [59] Scale bar= 200 µm (ci, di), 20 µm (cii, dii).

Sources:

[57], Copyright 2011. Reproduced with permission from Springer Nature

[58], Copyright 2016. Reproduced with permission from John Wiley and Sons

[59], Copyright 2016. Reproduced with permission from Elsevier Inc.