Polymeric Membrane Potentiometric Ion Sensors with Dual Biocompatible Functionality

Polymeric membrane ion-selective electrodes (ISEs) have been routinely used to detect clinically important ions in physiological samples. However, the development of biocompatible potentiometric ion sensors for long-term measurements remains a significant challenge. Herein, a polymeric membrane Ca²⁺-ISE with dual biocompatible functionality (i.e., antibiofouling and low-cytotoxicity properties) is proposed. It is based on a semifluorinated, plasticizer-free sensing membrane with an immobilized ionophore. A new semifluorinated copolymer, 1H,1H,2H,2H-perfluorooctyl methacrylate-lauryl methacrylate (PFMA-LMA), has been synthesized. The low surface energy of the semifluorinated membrane could effectively prevent the surface adsorption of foulants such as lipids, proteins, and blood cells from biological samples. The immobilization of the sensing component and the plasticizer-free approach could significantly reduce the physiological toxicity of the sensor. Compared to the conventional plasticized poly(vinyl chloride) (PVC)-based membrane Ca²⁺-ISE, the bifunctional, biocompatible PFMA-LMA membrane electrode exhibits significantly reduced blood cell adhesion and cytotoxicity. The present sensor could be used for continuous real-time monitoring of Ca²⁺ in human blood for at least 3 days. The proposed strategy of dual biocompatible functionality has promising potential for the development of implantable and wearable polymeric membrane-based electrochemical and optical sensors.