Assistant Professor Chung-Ang University, United States
Introduction:: Myocardial infarction (MI) is one of the leading causes of death and disability. Recently developed cardiac patches provide mechanical support and additional conductive paths to promote electrical signal propagation in the MI area to synchronize cardiac excitation and contraction. Cardiac patches based on conductive polymers offer attractive features; however, the modest levels of elasticity and high impedance interfaces limit their mechanical and electrical performance.
Materials and Methods:: The Mo serpentine structure was fabricated using a laser cutter (LPKF ProtoLaser R, LPKF Laser & Electronics). The POCO pre-polymer was synthesized according to procedures based on a previous report. Briefly, 1,8-ontandiol (Sigma-Aldrich), citrate acid (Sigma-Aldrich), and octanol (Acros Organics) were mixed and melted at 165 °C, followed by reaction at 140 °C for 3 h. The mixture was then dissolved in ethanol and precipitated in DI water for purification. The precipitate was collected and lyophilized for 24 h to obtain the final product. To fabricate the POCO patch, about 1 mL of the 40% POCO (w/w in ethanol) pre-polymer solution was added to a glass slide (7.5 × 5 cm2) and left at room temperature overnight for solvent evaporation. Then, the slide was placed in an oven set to 80 °C for 4 days to cure the POCO patch. To fabricate the BCEP, the Mo serpentine structure was placed atop a viscous POCO sol after solvent evaporation and cured at 80 °C for 4 days.
The mechanical properties of the samples were evaluated using an Instron universal testing machine. To test the Young’s modulus, samples of dimensions 3 × 1.2 cm2 were stretched at a constant velocity of 15 mm/min, and the force-strain curves were recorded for calculation. To test the fatigue resistance, the BCEP were stretched for 100,000 cycles with 10% strain at 1 Hz to mimic the beating of a human heart. Square BCEPs were fabricated for tensile tests along the longitudinal and transversal axes.
Results, Conclusions, and Discussions:: The bioresorbable, elastic and highly conductive cardiac patch described herein provides simple but useful functions as mechanical and electrical support layers for cardiac tissue regeneration. Compared with recently published studies, the BCEP has a significantly lower resistance and an acceptable modulus with unique bioresorbable properties (Figure 1). For example, phytic-acid-doped PANI on a chitosan substrate shows conductivity comparable to that of the BCEP but is relatively stiffer and non-bioresorbable. The elastic moduli of hydrogel-based cardiac patches ranges are in the kilopascal range, but with low conductivity. Several commercialized patch products (e.g., PeriPatch™ by Neovasc Inc., Edwards bovine pericardial patch by Edwards Lifesciences, SJM™ Pericadial Patch with EnCap™ by St. Jude Medical, Inc.) are attractive for their nontoxicity and bioresorbability, but offer poor electroconductivity. The specific system reported here is a hybrid material structure, consisting of a serpentine structure of Mo as a bioresorbable metal integrated within a stretchable biodegradable POCO substrate. The device provides sufficient elastic behaviors for repeatable deformations to physiologically relevant strains (~10%), to support the contractile function of cardiac tissue, where bioresorption occurs over a relevant time period. The BCEP is biocompatible and can promote maturation of hiPSC-CMs. Synchronized contractions of the hiPSC-CMs indicate that the Mo structure within the BCEP can effectively promote electrical signal propagation. Ex vivo experiments provide further validation of the promising electrical properties of the BCEP and of its potential use as a cardiac patch to improve heart function post-MI.
Acknowledgements (Optional): : This work made use of the NUFAB facility of Northwestern University’s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern’s MRSEC program (NSF DMR-1720139). The Center for Advanced Regenerative Engineering (CARE) provided partial funding support for this study.
