Nanoparticle DNA biosensor detects trace levels of lead in the environment

Citation

(2003), "Nanoparticle DNA biosensor detects trace levels of lead in the environment", Sensor Review, Vol. 23 No. 4. https://doi.org/10.1108/sr.2003.08723dab.009

Nanoparticle DNA biosensor detects trace levels of lead in the environment

Nanoparticle DNA biosensor detects trace levels of lead in the environment

Keywords: DNA, Biosensor, Nanoparticles, Environmental monitoring

Abstract. This article describes a prototype colourimetric biosensor for detecting lead and other metallic pollutants in the environment. It is based on gold nanoparticles and modified DNA molecules and is highly selective and sensitive.

A research group from the American University of Illinois at Urbana-Champaign have developed a colorimetric technique which combines nanotechnology with DNA-based biosensing to detect lead in paint and other metallic environmental contaminants.

The active components of the sensor are 13 nm diameter gold nanoparticles linked to thio-modified DNA, the "DNAzyme" and the DNAzyme's substrate (the compound on which an enzyme acts). DNAzymes are DNA molecules, modified to exhibit enzymatic activity, which are also known as deoxyribozymes or "catalytic DNA". The DNAzyme substrate used here hybridises to a gold nanoparticle at each end, causing the nanoparticles to aggregate into clusters with a characteristic blue colour. In the presence of lead ions the DNAzyme catalyses the cleavage of the substrate, preventing the nanoparticle aggregates from forming and produces a red colour, the intensity of which equates to the concentration of the lead ions.

The sensor is highly selective and does not respond to other metal ions such as magnesium, calcium, manganese, cobalt, nickel, copper, zinc or cadmium. However, a combinatorial biology technique termed "in vitro selection" can produce DNAzymes that are highly specific to a range of other metal ions. According to Illinois University Researcher Yi Lu, "This technique will significantly expand the scope of nanoparticle biosensors to essentially any analyte of choice, because in vitro selection can be used to select DNAzymes that are active in the presence of any desired analytes or concentrations." The research group also found that it was possible to tailor the sensor to respond to lead over several orders of magnitude by introducing a proportion of inactive DNAzymes. For example, an unoptimised sensor detected lead ions with a concentration of 100 nM up to 4 μM, but with inactive DNAzymes present it detected concentrations in the range 10-200 μM.

The sensor is simple to use, potentially inexpensive and appears to offer strong prospects for detecting lead paint in houses, as, according to the US Environmental Protection Agency, the leaded paint test kits currently available show high rates of both false positive and false negative results when compared with laboratory analytical procedures. Other potential applications include detecting lead and other toxic metals in swimming pools and playgrounds; environmental monitoring; clinical toxicology; monitoring industrial and waste-disposal processes; and monitoring and assessment of the bioremediation of contaminated industrial sites.

The group now plans to develop sensors for other toxic metal ions such as arsenic, chromium and mercury, to create similar sensors for aromatic pollutants and to design a family of colorimetric test kits based on this technology.