A Colorimetric Lead Biosensor Using DNAzyme-Directed Assembly of Gold Nanoparticles

TLDR

The study reports a highly sensitive, selective colorimetric biosensor for lead that uses DNAzyme‑directed assembly of gold nanoparticles. The sensor relies on a DNAzyme and its substrate hybridizing to 5′‑thio‑modified DNA on gold nanoparticles, causing nanoparticle aggregation and a blue color; lead‑induced cleavage of the DNAzyme prevents aggregation, yielding red individual nanoparticles. The sensor’s detection range can be tuned from 100 nM to over 200 µM by adding an inactive DNAzyme variant, and the approach offers a general strategy for designing simple colorimetric biosensors for analytes amenable to in‑vitro selection.

Abstract

A highly sensitive and selective colorimetric lead biosensor based on DNAzyme-directed assembly of gold nanoparticles is reported. It consists of a DNAzyme and its substrate that can hybridize to a 5'-thio-modified DNA attached to gold nanoparticles. The hybridization brings gold nanoparticles together, resulting in a blue-colored nanoparticle assembly. In the presence of lead, the DNAzyme catalyzes specific hydrolytic cleavage, which prevents the formation of the nanoparticle assembly, resulting in red-colored individual nanoparticles. The detection level can be tuned to several orders of magnitude, from 100 nM to over 200 μM, through addition of an inactive variant of the DNAzyme. The concept developed here can be applied to the design of nucleic acid enzyme/nanoparticle sensors for analytes that are subject to in vitro selection, and thus can significantly expand the scope of nanomaterial applications and provide a novel approach to designing simple colorimetric biosensors.