Nanoassembled fluorescent microshells as biochemical sensors

Hollow microshells are being fabricated for potential use as versatile sensors for real-time measurements of biochemicals. These shells are assembled using Layer-by-Layer (LBL) assembly of polyions onto colloidal polymer template particles. The latex particles are subsequently dissolved leaving behind stable, hollow shells into which analyte-sensitive and reference dyes are introduced. Fundamental studies have been performed to determine optical and chemical characteristics of these shells. Tests have been performed to determine the integrity of shells with respect to leaching and structural stability and robustness. The microshells were then loaded with an assay composed of a sodium sensitive fluorophore (SBFI) or a potassium sensitive fluorophore (PBFI), along with an analyte insensitive reference dye. It has been shown that the dye-loaded capsules retain their sensitivity to ion concentration with fluorescence characteristics similar to those of the dyes in liquid-phase, and that the sensor response to increasing ion concentration is linear over a physiologically significant range. In addition, preliminary results have demonstrated the ability of these capsules to be "loaded" with other sensor chemistry, including Ruthenium/Glucose-oxidase, and a FITC-dextran/TRITC-ConA competitive binding assay for glucose sensing based on fluorescent resonance energy transfer (FRET) methods.