Solid-contaction-selective electrodes (SC-ISEs) in direct long-termcontact with physiological samples must be biocompatible and resistantto biofouling, but most wearable SC-ISEs proposed to date containplasticized poly(vinyl chloride) (PVC) membranes, which have poorbiocompatibility. Silicones are a promising alternative to plasticizedPVC because of their excellent biocompatibility, but little work hasbeen done to study the relationship between silicone composition andISE performance. To address this, we prepared and tested K+ SC-ISEs with colloid-imprinted mesoporous (CIM) carbon as the solidcontact and three different condensation-cured silicones: a customsilicone prepared in-house (Silicone 1), a commercialsilicone (Dow 3140, Silicone 2), and a commercial fluorosilicone(Dow 730, Fluorosilicone 1). SC-ISEs prepared with eachof these polymers and the ionophore valinomycin and added ionic sitesexhibited Nernstian responses, excellent selectivities, and signaldrifts as low as 3 & mu;V/h in 1 mM KCl solution. All ISEs maintainedNernstian response slopes and had only very slightly worsened selectivitiesafter 41 h exposure to porcine plasma (log K (K,Na) values of -4.56, -4.58, and -4.49,to -4.04, -4.00, and -3.90 for Silicone1, Silicone 2, and Fluorosilicone 1, respectively), confirming that these sensors retain the high selectivitythat makes them suitable for use in physiological samples. When immersedin porcine plasma, the SC-ISEs exhibited emf drifts that were stillfairly low but notably larger than when measurements were performedin pure water. Interestingly, despite the very similar structuresof these matrix polymers, SC-ISEs prepared with Silicone 2 showed lower drift in porcine blood plasma (-55 & mu;V/h,over 41 h) compared to Silicone 1 (-495 & mu;V/h)or Fluorosilicone 1 (-297 & mu;V/h).
