Enzyme-regulated unmodified gold nanoparticle aggregation: a label free colorimetric assay for rapid and sensitive detection of adenosine deaminase activity and inhibition.

Based on enzyme-regulated unmodified gold nanoparticle aggregation, a visual and homogeneous assay of adenosine deaminase (ADA) activity without any other coupling enzymes, aptamers or additional modifications has been developed. The present strategy is simple, cost-effective, high throughput, selective and sensitive for ADA with a detection limit of 0.8227 U L(-1).