Encapsulation of FITC to monitor extracellular pH: A step towards the development of red blood cells as circulating blood analyte biosensors

Sarah C. Ritter, Mark A. Milanick, Kenith E. Meissner

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

A need exists for a long-term, minimally-invasive system to monitor blood analytes. For certain analytes, such as glucose in the case of diabetics, a continuous system would help reduce complications. Current methods suffer significant drawbacks, such as low patient compliance for the finger stick test or short lifetime (i.e., 3-7 days) and required calibrations for continuous glucose monitors. Red blood cells (RBCs) are potential biocompatible carriers of sensing assays for long-term monitoring. We demonstrate that RBCs can be loaded with an analyte-sensitive fluorescent dye. In the current study, FITC, a pH-sensitive fluorescent dye, is encapsulated within resealed red cell ghosts. Intracellular FITC reports on extracellular pH: fluorescence intensity increases as extracellular pH increases because the RBC rapidly equilibrates to the pH of the external environment through the chloride-bicarbonate exchanger. The resealed ghost sensors exhibit an excellent ability to reversibly track pH over the physiological pH range with a resolution down to 0.014 pH unit. Dye loading efficiency varies from 30% to 80%. Although complete loading is ideal, it is not necessary, as the fluorescence signal is an integration of all resealed ghosts within the excitation volume. The resealed ghosts could serve as a long-term (>1 to 2 months), continuous, circulating biosensor for the management of diseases, such as diabetes.

Original languageEnglish (US)
Pages (from-to)2012-2021
Number of pages10
JournalBiomedical Optics Express
Volume2
Issue number7
DOIs
StatePublished - 2011

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Atomic and Molecular Physics, and Optics

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