Holly Goodson, Department of Chemistry and Biochemistry (UND)
As described earlier (see the Lieberman project), paper analytical devices provide a powerful platform for performing analytical tasks in low-resource environments. However, one challenge with the PADs is that each chemical assay requires a sensitive and specific colorimetric test. In some cases, appropriate tests do not exist for desired compounds and/or at the desired sensitivity. To meet this challenge, we are developing bioPADs. bioPADs will allow us to expand the library of sensor options by harnessing the sensitivity and specificity of biological systems. Our initial focus is on developing BioPADs to detect counterfeit drugs, but we envision the bio-PADs as being particularly useful for detecting toxins such as arsenic that are problematic in many developing areas, and for which there are no testing methods that are low cost, portable, and suitable for use by the people who are at risk.[i]
Technology: We are developing genetically-engineered baker’s yeast strains that respond to the presence of specific water contaminants by producing a visible pigment (presently b-gal, but we are working on other pigments); we then encapsulate these yeast in hydrogels along with growth media, bond this mixture to the paper, and dry it to form a bioPAD. The genetic engineering aspects of the technology are based on an established synthetic biology gene circuits,[ii] while the yeast entrapment technology is based on established approaches for long-term encapsulation of yeast in PVA and calcium alginate matrices for industrial fermentation.[iii]We presently have tetracycline-responsive bioPADs that are stable for more than 180 days at room temperature, and will be working with REU students to expand the technology to other analytes. Results could be presented at synthetic biology meetings such as SynBio, or in analytical sessions at a national ACS meeting.
[i] Ng JC. “Environmental contamination of arsenic and its toxicological impact on humans,” 2005, Env. Chem, 2: 146-160.
[ii] e.g., Ajo-Franklin CM, Drubin DA, Eskin JA, et al. “Rational design of memory in eukaryotic cells,” 2007, Genes and Development, 21:2271-2276.
[iii] a) Willaert RG, Baron GV “Gel entrapment and micro-encapsulation: Methods, applications and engineering principles,” 1996, Rev. Chem. Eng., 12:5-205. b) Baptista CMSG, Coias JMA, Oliveira ACM, et al. “Natural immobilisation of microorganisms for continuous ethanol production,” 2006, Enz. Microbial. Tech. 40: 127-131