Improving the Properties of Optical Anion Sensors using Transmembrane Transporters and Extracting Agents

With the support of the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, Dr. Nathalie Busschaert of Tulane University is studying a novel way to improve the selectivity and sensitivity of optical anion sensors. Anions play an important role in life, from storing the genetic code on the polyanion DNA, to being the active ingredient in agricultural fertilizers and acting as a precursor to other chemicals of high value to industrial processes.

Consequently, chemists have been designing systems that can sense anionic species through a variety of methods. However, one of the biggest challenges in sensor development is the detection of only the anion of interest (selectivity) in the concentration range that is relevant for the anion of interest (sensitivity). Dr.

Busschaert will use a combination of molecule-based ion transporters or extracting agents with molecules whose color changes upon anion exposure to generate highly selective and sensitive anion sensors. The fundamental principles to be discovered are poised to have an impact on light-based sensor development, as well as isolation or enrichment of anions by their transportation through membranes.

The project is anticipated to provide highly selective anion sensors whose sensing signal changes a great deal with tiny changes in the amount of anion present. The outcomes are anticipated to lay the groundwork for applications that can have a broader impact on the numerous applications of anion sensors, such as measurements in the medical diagnostics and environmental fields.

This work is expected to have a further broader impact on the participation of women in STEM (Science, Technology, Engineering, Mathematics) fields, as Dr. Busschaert will be actively involved in a variety of professional development activities with female undergraduate and graduate students at Tulane University, as well as with those resulting from interactions with national professional societies.

The central hypothesis of the project is that transmembrane transport or liquid-liquid extraction can provide a ‘double selectivity filter’, whereby only those analytes that are transported/extracted and cause an optical change in a liposome-encapsulated chromophore will be sensed by the system. This means that neither the transporter nor the fluorophore needs to be highly selective by themselves and are therefore structurally simple, and as a result, inexpensive.

In addition, transmembrane anion transport has the potential to enrich the concentration of the desired anion inside the liposome, leading to an increase in the sensitivity of the response of the encapsulated chromophore. The hypothesis will be tested by performing a series of ultraviolet-visible and fluorescence spectroscopy measurements to determine the selectivity and sensitivity of a carefully selected group of transport- and extraction-based optical sensors against a variety of anionic species.

This project is jointly funded by the Chemical Measurement and Imaging Program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), with partial support from the Chemical, Bioengineering, Environmental and Transport Systems (CBET) Division of the Engineering Directorate.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.