Label-free colorimetric detection of lead ions with a nanomolar detection limit and tunable dynamic range by using gold nanoparticles and DNAzyme

A method is presented to design a label-free colorimetric sensor based on DNAzyme for real-time detection of lead. The study used Gold nanoparticles (AuNPs) and un-labeled DNAzymes to detect lead with nanomolar detection limit and tunable dynamic range. The label free DNAzyme colorimetric sensor is based on 8-17 DNAzyme composed of a substrate strand and an enzyme strand. The DNAzyme complex was prepare in 10 mN Tris buffer pH 7.2 with 100 mM NaCl with various concentrations of lead. The sensor has a detection limit of 3nM and can be tuned by controlling the pH. The colorimetric sensors can be used to detect other metal ions and non-metal targets by using aptamers and aptazymes. The study used an UV-vis spectroscopy to investigate the plasmon resonance peak of AuNPs and found a slowness in kinetics of the reaction at lower pH.