Ion Density Deviations in Polyelectrolyte Microcapsules: Influence on Biosensors

TL;DR

This study uses nonlinear Poisson-Boltzmann theory to analyze how charge density in polyelectrolyte microcapsules affects local ion concentrations and pH, impacting their effectiveness as biosensors.

Contribution

It provides a systematic theoretical investigation of ion density deviations caused by charged microcapsules, informing biosensor design and accuracy.

Findings

Ion density deviations depend on capsule charge density and salt concentration.

Charged microcapsules can cause local pH deviations affecting sensor readings.

Results are relevant for improving biosensor reliability.

Abstract

Polyelectrolyte microcapsules loaded with fluorescent dyes have been proposed as biosensors to monitor local pH and ionic strength for diagnostic purposes. In the case of charged microcapsules, however, the local electric field can cause deviations of ion densities inside the cavities, potentially resulting in misdiagnosis of some diseases. Using nonlinear Poisson-Boltzmann theory, we systematically investigate these deviations induced by charged microcapsules. Our results show that the microcapsule charge density, as well as the capsule and salt concentrations, contribute to deviations of local ion concentrations and pH. Our findings are relevant for applications of polyelectrolyte microcapsules with encapsulated ion-sensitive dyes as biosensors.