Posted on 02/01/2010 1:29:34 PM PST by neverdem
Scientists in the United States have produced a simple dipstick test for detecting lead levels in paints.
Easy-to-use biosensors are important for detection of highly toxic trace metal ions in the environment. Cross-linked gold nanoparticles modified with metal-specific DNAzymes have been used in solution to create highly sensitive and selective colorimetric metal sensors based on the colour change between aggregated (blue) and dispersed (red) gold nanoparticles. However, in solution the colour change can be difficult to distinguish and nanoparticle stability is poor, explains Yi Lu at the University of Illinois at Urbana Champaign.
Lu and colleagues have developed a sensor that uses non-cross-linked gold nanoparticle-DNA conjugates, bound to a lead-activated DNAzyme mounted on a solid dipstick platform. Lead ions in paint samples catalyse the enzymatic cleavage of the DNA-nanoparticle conjugates which are captured on the dipstick by a complementary DNA sequence. If the levels of lead are present, a red line forms across the dipstick - similar to a pregnancy test kit.
The dipstick is designed to give a positive result for lead levels over 1mg per cm2 - the value the U.S. Department of Housing and Development classifies paint to be lead-based. Lu demonstrated that the dipstick test produced the correct results on paint taken from walls even if the lead-based paint had been coated several times, simulating conditions in many households.
Lu says that the detection range can be tuned to the exact threshold defined for lead in different materials like dust and water simply by using different DNA strands.
Duncan Graham at the University of Strathclyde, Glasgow, UK, an expert in nanoparticle sensor systems, says, 'this nanoparticle based approach offers advantages in terms of ease of use and performance. The design to generate a positive signal is highly innovative and the combination of nanoparticles and DNAzyme is attractive for instrument-free quantitative analysis.'
'This technique makes bionanotechnology easy to use and applicable to everyday life,' concludes Lu. He adds that the team are interested in expanding on this technique to detect other metal ions and also bacterial viruses and other toxins in water.
Easy-to-use dipstick tests for detection of lead in paints using non-cross-linked gold nanoparticle–DNAzyme conjugates
Debapriya Mazumdar, Juewen Liu, Geng Lu, Juanzuo Zhou and Yi Lu, Chem. Commun., 2010
DOI: 10.1039/b917772h
It's not free access to the original article from the abstract. I got RSC Publishing restricted content.
It does a great job of inhibiting mold in humid climates.
Also great at inhibiting rust in saltwater applications. Will expand and contract (and so not crack) with the surface it is applied to. Still used in some commercial paints for bridges and other steel structures. Lots of “red lead” in metal products for off-shore structures (shipyards in S. Tex. get a lot of painted components for offshore rig construction) coming from Brazil. Contractors remove lead paint and replace it with lead paint.
OSHA does not use the HUD standard of 0.5% (5000 ppm). OSHA uses the term “lead containing paint”, which is any lead content. If it’s not below the detection limit, it’s regulated. A lot of contractors get caught on this.
That’s thinking with your dipstick, Jimmy!
Of swine, birds and men -- pandemic H1N1 flu
National Jewish Health researchers discover how virulent bacteria
Compound found that targets wide range of viruses
FReepmail me if you want on or off my health and science ping list.
If only we had this around when you were little.....:o)
Hell, I would’ve gone hungry!
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.