Application of Cell Surface Engineering to Biosensing System

Abstract

Organophosphorus compounds (OPs) such as pesticides, fungicides, and herbicides are highly toxic but are nevertheless extensively used worldwide. To detect OPs, we constructed a yeast strain that co-displays organophosphorus hydrolase (OPH) and enhanced green fluorescent protein (EGFP) on the cell surface using a Flo1p anchor system. The strain with highest activity showed 20-fold greater OPH activity than Escherichia coli using the ice nucleation protein anchor system. OPs degradation releases protons and causes a change in pH. This pH change results in structural deformation of EGFP, which triggers quenching of its fluorescence, thereby making this cell useful for visual detection of OPs (20 mM paraoxon) in a microchamber chip. The authors also report the real-time detection of OPs using a sol–gel silica planar waveguide doped with EGFP and OPH on a yeast-cell surface display. The waveguide was pumped at 488 nm, and it emitted green fluorescence at the far field. The green fluorescent light at 550 nm changed by 50% from the original power 1 min after application of OPs.