Arsenic biosenseor: a step further
© French et al; licensee BioMed Central Ltd. 2007
Published: 8 May 2007
Arsenic poisoning affects some 100 million people worldwide. The problem is greatest in Bangladesh, one of the world's poorest countries. One well in four contains arsenic levels above the World Health Organisation's (WHO) recommended guidelines, however, the geographical distribution is completely arbitrary. One well in a village could be clean, while another could be heavily contaminated. Efforts taken by various organisations to mitigate the damage are ineffectual due to the immense scale of the problem. There are over 10 million wells that need to be tested at least twice a year. Even filtration systems need to be periodically tested to maintain reliability. The long-term effects of arsenic poisoning are severe with 1% of the affected population developing cancers of the skin, kidney and bladder.
The current field technology, the Gutzeit method, is a chemical assay. The reagents used are harmful (and include mercury as a by-product), hence tests need to be conducted by a qualified field technician in order to safely produce reliable and accurate results. When conducted optimally, the lower limit of the sensitivity is 50 ppb, which is the WHO guideline maximum concentration, but the assay still reports roughly 33% of tests as false negatives.
The first part is the arsenic responsive promoter from E. coli. The ArsR gene and the LacZ operon were ligated into plasmid vector pSB1A2 and introduced into E. coli JM109.
Once the arsR – lacZ construct had been assembled, we needed to characterise what we had built. This was done by adding decreasing concentrations of arsenic to drinking water and measuring the pH over time.
In conclusion, we successfully designed and modelled the complex device. We proved a measurable pH response could be obtained with As concentration to WHO standards. We successfully biobricked a variety of parts and submitted them to the Registry of Standard Biological Parts at MIT. We feel that with further work, our device could potentially help millions worldwide.
This article is published under license to BioMed Central Ltd.