Development of a 3D Printed Liquid-Core Hydrogel Platform for Real-Time Carbon Nanotube Sensors: A Breakthrough in Minimally Invasive Health Monitoring

Abstract

The need for minimally invasive, real-time, and low-cost medical sensors holds great potential to revolutionize the healthcare industry. Single-walled carbon nanotube (SWNT)-based near-infrared (nIR) sensors are a relatively new field, able to provide high-quality spatial and temporal information regarding a wide range of cellular signaling molecules, including nitric oxide (NO), and hydrogen peroxide (H2O2). However, their use for in vitro and in vivo applications has been limited due to challenges related to their compatibility with packaging or immobilization techniques. Approaches like surface immobilization on solid substrates and dialysis bag confinement are costly, unstable, and unsuitable for use in settings with limited resources. SWNT sensors have recently been implanted into a large animal model as a proof-of-concept, but the challenge of retaining SWNT is currently restricting the advancement of hydrogel technology in wearable/implantable biosensors. We have developed and optimized a 3D printed liquid-core self-healing hydrogel platform that encapsulates the (AT)15 wrapped-SWNT, a NO sensor, and studied its mechanical and optical characterizations. Notably, after 90-days at 37 °C, the fluorescence intensity exhibited a negligible decrease. Statistical analysis indicates that the change in intensity from day 1 to day 90 was statistically insignificant, highlighting the sensor's robust and stable performance over the extended testing period. A linear calibration curve was obtained when the percent quenching was plotted against the logarithm of NO concentration. Furthermore, a polyvinyl alcohol (PVA) wrapped SWNT, a non-reactive sensor, was implanted into 3D printed liquid-core hydrogel platform and no quenching was observed when it was exposed to NO. Therefore, 3D printed liquid-core hydrogel platforms offer a solution for on-site detection of small-molecule analytes, overcoming a major challenge in real-time medical diagnostics and environmental monitoring.