Designing microcapsules with controlled permeation property for capsule-type sensors.

Abstract

A sensor that detects stimuli changes with changes of pigment color or plasmon color called a colorimetric sensor. The sensing performance of colorimetric sensor like metal nanoparticles or chromophore molecules is decreased by non-specific binding of adhesive molecules in pristine samples or dilution by the sample fluids. It is challenging to direct detection from unpurified pristine samples. To overcom this limitations, we came up with the microcapsules-type sensor platform. Due to the core-shell structure of microcapsules, the sensor probe dispersants can encapsulate and maintain its concentration and the molecules can selectively penetrated through the shell. We focused on the permeation property of shell of microcapsules for enhances and expands its usage of microcapsules as a sensor platform. Here, we generated W/O/W/ double emulsion templated microcapsules with hydrophobic shell and applied to pH detection system by introducing pH sensor probe in the core. For enhance molecule transportation through the shell, we generated W/O/W/O triple emulsion templated microcapsules with hydrogel shell and oil shell. The hydrogel shell exhibits size-selective permeation, while the oil shell exhibits ion-selective permeation property that is adequate to heavy-metal ion detection system. Moreover, we reduce the hydrogel shell thickness by induce osmotic-pressure within the triple emulsion droplets. Thinner hydrogel shell shows enhanced permeability to the transportable molecules. And we strengthen the hydrogel shell by introducing double-hydrogel network system. It enhances the mechanical stability of hydrogel microcapsules due to the existence of sacrificial bond. We suggested osmotic-shock driven size-selective alginate shell of microcapsules as a biocompatible sensor applications. Therefore, the microcapsule with size-selective permeation, enhanced permeability and mechanical stability, biocompatibility have a potential as a sensor platform such as pH, toxic molecules detection from pristine samples.