Gold nanoparticles based colorimetric assay for bacterial enzyme identification and inhibitors screening

We present a simple and specific colorimetric assay for real time identification of bacterial enzymes and inhibitors screening. In the presence of ß-lactamases, the lactam amide bond in cephem nucleus was cleaved following the release of thiol modified linker which induce the cross-link of gold nanoparticles. Upon aggregation, gold nanoparticles changed color from red to purple-blue significantly. The colorimetric assay was easily monitored with naked eyes and associated with red-shift of surface plasmon resonance of gold nanoparticles. This approach is much more sensitive and may offer an alternative platform to rapidly evaluate the enzymatic activities and efficiently high throughput screen the inhibitors of ß-lactamases in real time. It may also provide the practical application for rapid and specific detection of antibiotic resistant bacteria in clinical settings.