Influence of the Composition of Plasticizer-Free Silicone-Based Ion-Selective Membranes on Signal Stability in Aqueous and Blood Plasma Samples

Brian D. Spindler, Katerina I. Graf, Xin I.N. Dong, Minog Kim, Xin V. Chen, Philippe Bühlmann, Andreas Stein

Research output: Contribution to journalArticlepeer-review

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Abstract

Solid-contact ion-selective electrodes (SC-ISEs) in direct long-term contact with physiological samples must be biocompatible and resistant to biofouling, but most wearable SC-ISEs proposed to date contain plasticized poly(vinyl chloride) (PVC) membranes, which have poor biocompatibility. Silicones are a promising alternative to plasticized PVC because of their excellent biocompatibility, but little work has been done to study the relationship between silicone composition and ISE performance. To address this, we prepared and tested K+ SC-ISEs with colloid-imprinted mesoporous (CIM) carbon as the solid contact and three different condensation-cured silicones: a custom silicone prepared in-house (Silicone 1), a commercial silicone (Dow 3140, Silicone 2), and a commercial fluorosilicone (Dow 730, Fluorosilicone 1). SC-ISEs prepared with each of these polymers and the ionophore valinomycin and added ionic sites exhibited Nernstian responses, excellent selectivities, and signal drifts as low as 3 μV/h in 1 mM KCl solution. All ISEs maintained Nernstian response slopes and had only very slightly worsened selectivities after 41 h exposure to porcine plasma (log KK,Na values of −4.56, −4.58, and −4.49, to −4.04, −4.00, and −3.90 for Silicone 1, Silicone 2, and Fluorosilicone 1, respectively), confirming that these sensors retain the high selectivity that makes them suitable for use in physiological samples. When immersed in porcine plasma, the SC-ISEs exhibited emf drifts that were still fairly low but notably larger than when measurements were performed in pure water. Interestingly, despite the very similar structures of these matrix polymers, SC-ISEs prepared with Silicone 2 showed lower drift in porcine blood plasma (−55 μV/h, over 41 h) compared to Silicone 1 (−495 μV/h) or Fluorosilicone 1 (−297 μV/h).

Original languageEnglish (US)
Pages (from-to)12419-12426
Number of pages8
JournalAnalytical Chemistry
Volume95
Issue number33
DOIs
StatePublished - Aug 22 2023

Bibliographical note

Funding Information:
The authors declare the following competing financial interest(s): This work was funded in part by Medtronic PLC. A.S., P.B., and the University of Minnesota (UMN) have a patent and a patent application (U.S. patent no. 9,874,539; US2020/059979) relating to the use of CIM carbon in ion-selective and reference electrodes. The UMN and the inventors are entitled to standard royalties should licensing revenue be generated from these inventions. Acknowledgments

Publisher Copyright:
© 2023 American Chemical Society.

MRSEC Support

  • Shared

PubMed: MeSH publication types

  • Journal Article
  • Research Support, U.S. Gov't, Non-P.H.S.

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