关键词: 导电心肌补片, 聚吡咯, 可拉伸, 心肌梗死, 经编补片, 医用纺织品

Abstract:

Objective Conductive cardiac patches play a crucial role in the treatment of myocardial infarction (MI). Anisotropic microstructures such as oriented fiber structures have been designed to mimic the directional structure and electrical conductivity of natural myocardial tissue. However, existing conductive fiber-based myocardial repair materials are non-stretchable and can rupture under deformation, hindering the reconstruction of the conductive microenvironment. Therefore, the development of stretchable conductive myocardial patches with anisotropic properties and stable electrical conduction during heartbeats is crucial for effective myocardial repair.

Method Polypropylene (PP) patches were immersed in a dopamine solution, followed by treatment with pyrrole and FeCl₃·6H₂O to obtain PP/PPy samples. Morphological observation was conducted using a stereomicroscope and scanning electron microscope, while chemical composition analysis was performed using a Fourier-transform infrared spectrometer. Mechanical properties were evaluated using a universal material testing machine, and electrical conductivity was measured using a source meter. The resistance changes of patches under stretching strain were assessed using a multi-modal tester. The viability of human foreskin fibroblast cultured with the patches was evaluated using the CCK-8 assay to evaluate the biotoxicity of the patch.

Results Optical microscopy images of the knitted patches with different mesh structures were shown (single denbigh stitch, double denbigh derivative tricot stitch with lapping and three denbigh weft laid-in stitch). Scanning electron microscopy (SEM) images reveal the surface morphology of the PP monofilaments before and after PPy coating. The untreated PP monofilaments have a smooth surface, while the PPy-coated PP monofilaments showed roughness due to particle deposition, indicating successful PPy coating. The characteristic peak at 1 045 cm^-1, attributing to the absorption peak caused by the in-plane C—H vibration of PPy, also confirmed the successful coating of PPy on the PP patch surface. These mesh structures provided flexibility and stretchability to the patches, with fracture elongation exceeding 100%, making them suitable for cardiac applications. Statistical analysis showed no significant differences in fracture strength and elongation between the PP patches and PP/PPy patches, suggesting that the PPy coating had no significant impact on these properties. The double denbigh derivative tricot stitch structure with lapping showed an increase in Young's modulus for the PP/PPy patches compared to the PP patches, attributed to the higher stiffness of the PPy coating. The single denbigh stitch and three denbigh weft laid-in stitch structures had lower Young's modulus, as more filaments oriented along the stretching axis instead of being stretched. There were no significant differences in Young's modulus between the PP and PP/PPy patches with single denbigh stitch and three denbigh weft laid-in stitch structures. The conductivity range of the patches was consistent with that of native cardiac tissue, indicating their potential to restore the damaged conductive microenvironment in the infarcted area. The anisotropic electrical conduction ability of the PP/PPy patches with three denbigh weft laid-in stitch structure further aligns with the anisotropy ratio range of native cardiac tissue, enhancing their effectiveness in restoring directional conductivity. Furthermore, the conductive patches demonstrated stable electrical conductivity under tensile strain, which is important for maintaining their performance during cardiac contraction. The PP/PPy patches with single denbigh stitch and three denbigh weft laid-in stitch structures exhibited lower relative resistance change compared to the patches with double denbigh derivative tricot stitch structure with lapping, indicating their superior structural deformation capability. Importantly, the conductive patches showed no cytotoxicity in co-culture experiments with HFF-1 cells. This finding provides assurance for their biocompatibility and supports their potential use in cardiac repair and regeneration applications.

Conclusion In conclusion, stretchable conductive patches with different mesh structures were successfully developed using warp knitting technology and in-situ polymerization. The PP/PPy patches with single denbigh stitch and three denbigh weft laid-in stitch structures effectively prevented rigid conductive coatings on the flexible patches, while maintaining good conductivity and stability. Furthermore, the PP/PPy patches exhibited excellent biocompatibility with HFF-1 cells. These findings provide new insights and directions for the design and application of conductive cardiac patches, offering promising options for cardiac repair after myocardial infarction.

Key words: conductive myocardial patch, polypyrrole, stretchable, myocardial infarction, warp knit patch, medical textile