Stretchable, Multiplexed pH Sensors With Demonstrations on Rabbit and Human Hearts Undergoing Ischemia

TLDR

Stable pH is a key biomarker across tissues, yet monitoring it in the heart is difficult because of the organ’s soft mechanics, complex geometry, and continuous motion. The authors aim to create stretchable, multiplexed pH sensors for use in biological research, surgical tools, and long‑term implants. They fabricated arrays of IrOₓ pH sensors on thin elastomers and employed a thirty‑channel custom data acquisition system with a single potentiostat to map pH, demonstrated on balloon catheters and stretchable membranes. The arrays achieved super‑Nernstian sensitivity (~70 mV/pH), temperature‑linear response, and negligible ion interference, and enabled real‑time pH mapping on rabbit and human hearts during ischemia–reperfusion, demonstrating conformal, noninvasive monitoring.

Abstract

Abstract Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces, and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrO x pH sensors encapsulated in thin, low‐modulus elastomers to yield conformal monitoring systems capable of noninvasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In vitro testing reveals super‐Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (−1.6 mV °C −1 ), and minimal influence of extracellular ions (<3.5 mV). Device examples include sensor arrays on balloon catheters and on skin‐like stretchable membranes. Real‐time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia–reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long‐term implants.