Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires

Abstract

Myocardial infarction causes 7.3 million deaths worldwide, mostly for fibrillation that electrically originates from the damaged areas of the left ventricle. Conventional cardiac bypass graft and percutaneous coronary interventions allow reperfusion of the downstream tissue but do not counteract the bioelectrical alteration originated from the infarct area. Genetic, cellular, and tissue engineering therapies are promising avenues but require days/months for permitting proper functional tissue regeneration. Here we engineered biocompatible silicon carbide semiconductive nanowires that synthetically couple, via membrane nanobridge formations, isolated beating cardiomyocytes over distance, restoring physiological cell-cell conductance, thereby permitting the synchronization of bioelectrical activity in otherwise uncoupled cells. Local in-situ multiple injections of nanowires in the left ventricular infarcted regions allow rapid reinstatement of impulse propagation across damaged areas and recover electrogram parameters and conduction velocity. Here we propose this nanomedical intervention as a strategy for reducing ventricular arrhythmia after acute myocardial infarction.

Fig. 1. Growth of silicon carbide nanowires (SiC-NWs): physicochemical and biocompatibility characterizations.

a Representative bright-field SEM (top) and TEM (bottom) images of SiC-NWs detached from the substrate (n = 50 experiments repeated with similar results). b Viability of HL1 cardiomyocytes at 24 h (blue) and 48 h (pink) in control (no SiC-NWs) and SiC-NWs conditions (n = 3 biologically independent experiments in each group). Data are represented as mean ± SD. Unpaired two-sided Student’s t-test (statistical significance set at p < 0.05). Source data are provided as a Source Data file. c Same as b for intracellular ATP concentration. d Total intracellular uptake of SiC-NWs by HL1 cells (n = 3 experiments repeated with similar results). SS Lin Side scatter on a linear scale. e 60 min of reactive oxygen species (ROS) production from HL1 cells cultured w or w/o 50 µg/ml of SiC-NWs (n = 3 experiments repeated with similar results). DCFDA dichlorodihydrofluorescein diacetate. f Cell cycle characteristics of control (no SiC-NWs) HL1 cells (n = 3 experiments repeated with similar results). PI propidium iodide. g Same as f after 48 h of exposure to 50 µg/ml SiC-NWs.

Fig. 2. Synthetic cell–cell communication via coupling with SiC-NWs.

a Topographical imaging of HL1 cells with Hopping probe scanning ion conductance microscopy (HPICM): biological cell–cell coupling (Control, left); synthetic cell–cell MNB-based coupling obtained with SiC-NWs (SiC-NW, middle); quantification at the purple and pink lines of the middle image (right) (n = 5 experiments repeated with similar results). b Representative dual patch-clamp traces from biologically and synthetically coupled HL1 cell pairs. Voltage gradient applied to the cell source (left); and junctional conductance in biologically connected (middle) and SiC-NW-connected (right) cell pairs (n = 5 experiments repeated with similar results). c Cell–cell conductance (left) and contact length (right) for biologically coupled and synthetic SiC-NW-coupled HL1 cell pairs. n = 12 for biological coupled cells, black circles; n = 10 for SiC-NW coupled cells, black squares. Data are represented as mean ± SD. Unpaired two-sided Student’s t-test. *p = 0.046 vs. biological coupled cells; **p = 0.0017 vs. biological coupled cells. Source data are provided as a Source Data file.

Fig. 3. Interaction of SiC-NWs with membranes in HL1 cells.

a Top Left. SEM image of NWs forming an MNB physically coupling two distant cells. Top Middle. A blow-up of the purple box in the left image, showing partial internalization of SiC-NWs (blue arrowheads). Top Right. A focused Ion Beam was used to cut the MNB at the pink line in the left image (blue arrowhead points to SiC-NW). Bottom Left. Same as a, showing multicellular synthetic coupling created by SiC-NWs. Bottom Middle. A blow-up of the yellow box in the left image, showing that several SiC-NWs can form branches connecting multiple cells. Bottom Right. A blow-up of the blue rectangle, showing that several NWs can form a single MNB(n = 5 experiments repeated with similar results). b Time-lapse recording of the biodynamic interface an HL1 cell live-stained for actin (green) and SiC-NW (red). Images were acquired every 2 min for a 30 min period; Scale bars: 2 µm. Blue arrowhead indicates the position of the SiC-NW (n = 17 biological independent cells). c MNB formation triggered by actin for SiC-NWs partial internalization (n = 5). Legend numbers indicate SiC-NW lengths. Source data are provided as a Source Data file.

Fig. 4. Electrotonic optical action potential synchronization over distance in synthetically coupled cells.

a Color-coded images of an optical action potential spontaneously initiated in the pink HL1 cell (source) and rapidly propagating via SiC-NWs, to the blue HL1 cell (sink); ×20 magnification, scale bar = 10 μm. n = 19 experiments repeated with similar results. b Left Panel. Representative spontaneous APs propagated from a source cell (pink) to a sink cell (blue). n = 19 experiments repeated with similar results. Middle Panel. Optical AP duration calculated at 90% of repolarization in control HL1 cells (no SiC-NWs, n = 10, black dots), source cells (n = 19, pink squares), and sink cells (n = 19, blue triangles). Right Panel. Same as Middle Panel for AP amplitude. c Left Panel. Maximal upstroke velocity (dV/dt_max) calculated in controls (n = 10, black dots), sources (n = 19, pink squares) and sinks (n = 19, blue triangles). Middle Panel. AP amplitude values (n = 19, blue triangles) for cell sinks vs. cell–cell distance. Right Panel. Action Potential duration values (n = 19, blue triangles) for cell sink vs. cell–cell distance. Data are expressed as mean ± SD for the dot plots graphs, real values for the blue triangles graphs. Unpaired two-sided Student’s t-test. Statistical significance set at p < 0.05. *p = 0.01 vs no SiC-NWs. Source data are provided as a Source Data file.

Fig. 5. Synchronization of electrotonic intracellular Ca²⁺ transients over distance in synthetic cell–cell coupling.

a Top. Color-coded time course of Ca²⁺ initiation in two MNB-connected HL1 cells. Pink-dashed circle, source cell; blue-dashed circle, sink cell. Bottom. Relative series of spontaneous intracellular Ca²⁺ transient traces from the source (pink) and sink (blue) cell. n = 35 experiments repeated with similar results. b Intracellular Ca²⁺ transient delay from coupled cell pairs connected by SiC-NWs over distance, showing a linear correlation (n = 15). c Intracellular Ca²⁺ transient duration in control (no SiC-NWs, n = 48, black dots) source cells (n = 35, pink squares), and sink cells (n = 35, blue triangles). d Same as c, but for Ca²⁺ amplitude. Data expressed as mean ± SD. Unpaired two-sided Student’s t-test (significance set at p < 0.05). Source data are provided as a Source Data file.

Fig. 6. Electrophysiological profile of recovered sinus propagation in a cryoinjured portion of the heart via SiC-NWs myocardial injection.

a Timeline of the experimental adopted protocol for providing in situ left ventricular cryoinjury (Cryo) and Vehicle/SiC-NWs injection. EPM: epicardial potential mapping recording. ViKiE Video Kinematic Evaluation recording. b Photographs of the in situ heart for the cryoinjury (1), SiC-NWs injection (2), injected area (3), and epicardial grid (4) covering the injured and the surrounding portion of the ventricle (n = 10 experiments repeated with similar results); Scale bars: 2 mm. c Stereomicroscopy images of the transmural cryoinjured area (pale region left) containing 1 mg of SiC-NWs (yellow arrowheads, right); Scale bars: 500 µm (left), 80 µm (right). d TEM images of the infarcted cardiac tissue with SiC-NWs formed network. Left: macroscopic electron-dense images showing disorganized Z-lines (Zl), mitochondria (Mit), and capillary lumen (L). Middle and right images: area covered by the SiC-NWs network (zoomed in the blue area, purple arrow). n = 20 experiments repeated with similar results. Scale bars: 5 μm (left), 2 μm (middle), and 500 nm (right).

Fig. 7. Electrograms parameters and evaluation of epicardial velocities in the cryoinjury portion of the left ventricle following injection of SiC-NWs.

a Top. Tissue excitability and refractoriness parameters were measured on the epicardial EGs. Pre: before cryoinjury, Post Cryo: after cryoinjury, Post Cryo + SiC-NWs: after cryoinjury and treatment with NWs. Activation time: Pre, n = 66; Post Cryo, n = 58; Post Cryo + SiC-NWs, n = 28. RT interval: Pre, n = 63; Post Cryo, n = 56; Post Cryo + SiC-NWs, n = 35. RR interval: Pre, n = 45; Post Cryo, n = 54; Post Cryo + SiC-NWs, n = 26. QRS complex: Pre, n = 68; Post Cryo, n = 65; Post Cryo + SiC-NWs, n = 33. b Representative color-coded isochrones activation maps obtained from vehicle-treated animals (top) and SiC-NWs treated animals (bottom) showing relief of conduction block (Pink arrow). n = 4 experiments repeated with similar results for Vehicle injection. n = 8 experiments repeated with similar results for SiC-NWs injection. c Phase-map analysis of instantaneous velocity in the selected electrodes for the three conditions: Pre, before cryoinjury (n = 48); Post Cryo, after cryoinjury (n = 47); Post Cryo + SiC-NWs, after cryoinjury and treatment with NWs (n = 22). Data expressed as median and interquartile range. *p < 0.05; **p < 0.01, ***p < 0.001 (Kruskal–Wallis; post-hoc analysis: Dunn’s multiple comparison. C.I. = 95%). Source data are provided as a Source Data file.

Fig. 8. Recovery of epicardial electrograms parameters over time for the MI model used.

a Activation time. b QTc duration. c RT interval duration. d QRS complex duration. e T-wave duration. f RR interval duration. Blue dots: data measured before cryoinjury (Pre). Black dots: Cryo. Orange squares: Cryo + Vehicle. Pink triangles: Cryo + SiC-NWs. Colored lines: linear regression in the three conditions. Data are expressed as mean ± S.E.M. Statistical significance set at p < 0.05 (unpaired two-sided Student’s t-test). g Time-matched EG overlapping of the four different conditions. Source data are provided as a Source Data file.