Soft implantable printed bioelectronic system for wireless continuous monitoring of restenosis

Introduction:: Atherosclerosis is the most common underlying condition of cardiovascular disease, which remains the leading cause of death worldwide¹. This disease, where plaque builds on the inner walls of arteries causing blood vessels to narrow, is generally addressed through angioplasty and stenting². While implanting stents is a common procedure, a frequent complication is in-stent restenosis, where the artery re-narrows due to scar tissue. There are limited clinical options when diagnosing in-stent restenosis, as it can be asymptomatic until a severe blockage causes rapid degradation of a patient’s condition. Prior research exists for continuous monitoring of restenosis; however, most devices rely on the use of pressure sensors to indirectly measure stenosis or blockage along an artery. In addition to possible inaccuracies in the correlation of pressure and stenosis depending on stenosis location and blood flow changes, tissue grows over endovascular sensors after implantation, inhibiting the ability of the sensor to monitor pressure^3,4.


Materials and Methods:: To address this major clinical gap, we report an implantable vascular electronic device using a newly developed miniaturized capacitive strain sensor. A microneedle and capillary-based printing system is employed to achieve a high-resolution patterning of a soft, capacitive strain sensor. The sensor is made from alternating layers of polyimide and silver nanoparticle ink, then fully encapsulated in PDMS. Ink and printing parameters are studied to create a fully printed sensor, while sensor design is studied to enhance sensitivity and minimize sensor size. The sensor is integrated with a wireless vascular stent to offer a battery-free, wireless monitoring system compatible with conventional catheterization procedures. The vascular stent is fabricated with enhanced laser cutting and electroplating settings to ensure low resistance and reliable antenna performance.


Results, Conclusions, and Discussions:: The newly optimized sliding strain sensor resulted in an average sensitivity of 18% change in capacitance for 5% strain with a highest measured change at approximately 30% change in capacitance. This sensor successfully fits within the stent to allow for seamless integration within a catheter, ensuring proper deployment into blood vessels. The integrated vascular sensing system is demonstrated in an artery model for monitoring of restenosis progression at 60% and 75% occlusion. Restenosis was successfully diagnosed at these variable restenosis stages using continuous monitoring of resonant frequency changes through pulsatile testing. Collectively, the artery implantable bioelectronic system shows the potential for wireless, real-time monitoring of various cardiovascular diseases and stent-integrated sensing and treatments. This research demonstrates a fully printed, low profile strain sensor with high sensitivity to remotely detect restenosis within a stent. Furthermore, the device has clinical implications to provide high-risk patients with real-time monitoring of their health, providing them with more data to customize and continue their care.


Acknowledgements (Optional): : We acknowledge the support of the National Science Foundation. This study was partially supported by the IEN Center Grant from the Georgia Tech Institute for Electronics and Nanotechnology. Implantable devices in this work were fabricated at the Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (grant ECCS-2025462).



References (Optional): : 1. Atherosclerosis - What Is Atherosclerosis? | NHLBI, NIH. https://www.nhlbi.nih.gov/health/atherosclerosis (2022).

2. Atherosclerosis - Treatment | NHLBI, NIH. https://www.nhlbi.nih.gov/health/atherosclerosis/treatment (2022).

3. Chen, X., Assadsangabi, B., Hsiang, Y. & Takahata, K. Enabling Angioplasty‐Ready “Smart” Stents to Detect In‐Stent Restenosis and Occlusion. Adv Sci (Weinh) 5, 1700560 (2018).

4. Boutry, C. M. et al. Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow. Nat Biomed Eng 3, 47–57 (2019).