PhD candidate The George Washington University Arlington, Virginia, United States
Introduction:: Transparent microelectrode arrays (MEAs) that can allow multimodal study of the spatiotemporal cardiac characteristics are critical in studying and treating heart disease. However, existing implantable devices are designed to support long-term operational lifetimes and require surgical extraction when they malfunction or are no longer needed. At the same time, bioresorbable systems that can self-eliminate after performing temporary functions are increasingly attractive, since they can avoid the costs/risks of surgical extraction. However, developing soft transparent MEAs that exhibit bioresorbable functionality remain challenging and limited. Here, we report the design, fabrication, characterization, and validation of a soft, fully bioresorbable, and transparent MEA platform for bidirectional cardiac interfacing over a clinically relevant period.
Materials and Methods:: The devices are composed of entirely Food and Drug Administration approved materials that can completely disappear through natural biological processes in body after a certain period of use. Key components include a transparent and flexible poly(lactic-co-glycolic acid) (PLGA) substrate, an electron-beam lithography (EBL) patterned transparent molybdenum (Mo) nanogrid MEA, a photolithography determined interconnect layer, and a soft lithography defined transparent PLGA encapsulation layer.
Results, Conclusions, and Discussions:: Here, we report materials, device designs, fabrication strategies, performance characteristics, ex vivo and in vivo demonstrations, and systematic biocompatibility evaluation of a fully bioresorbable, implantable, flexible, and transparent MEA technology that provides organ conformal cardiac interfacing over clinically relevant temporary timescales. Studies on rat and human hearts highlight the function, form factor, durability, and capability of the devices for (1) co-localized multi-parameter spatiotemporal electrical/optical mapping of critical cardiac physiological parameters, including heart rhythm, biopotentials, oxygenation, metabolic state, calcium homeostasis, activation propagation pattern, and myocardial conduction and contraction; (2) real-time demand-based site-specific cardiac pacing to control the propagations of cardiac waves and provide therapeutic solutions such as treating bradycardia and atrioventricular (AV) block on soft heart tissue surfaces. The MEAs are stable for several days when immersed in phosphate-buffered saline (PBS), which is comparable to many postoperative care cycles, followed by complete bioresorption via hydrolysis within 6 weeks in vivo. Taken together, this work establishes the foundations of a soft bioresorbable transparent MEA technology to greatly expand the landscape for bioresorbable transient electronics and complement traditional approaches, with the potential to address the unmet needs in fundamental and translational cardiac research (e.g., ablation and surgical intervention procedures, postoperative recovery monitoring, post-infarction recovery, post-transcatheter aortic valve replacement (TAVR) recovery) where transient mapping and control of cardiac physiological parameters and functions are needed.
