Visible colour displacement sensing system for manganese(II)

Abstract

A visible colour displacement system has been developed for the colorimetric and ratiometric detection of Mn(II) ions. The supramolecular displacement system is composed of 2-(5-bromo-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS), which binds Zn^2 +  with a change in colour and binds Mn^2 +  without changing colour, ethylene glycol-bis(2-aminoethylether)-N, N, N ′, N ′-tetraacetic acid (EGTA) and Zn^2 +  at neutral pH. The sensing system exhibits the colour of 5-Br-PAPS itself since EGTA binds Zn^2 +  more strongly than 5-Br-PAPS does. However, upon presentation of Mn^2 + , Zn^2 +  is displaced from EGTA to bind 5-Br-PAPS to produce a pronounced colour change from yellow to purple. The absorbance decreases at 449 nm and increases at 552 nm, both linearly to Mn^2 +  concentration at low micromolar levels. This should be very advantageous since no suitable colorimetric reagent is available for the direct declination of Mn^2 +  at physiological pH.

Keywords:

• manganese(II)
• colorimetric
• sensor
• displacement assay
• ratiometric

Acknowledgements

We gratefully acknowledge the NSF (CTS-0608889), the NIGMS (GM-076202), and the NYU Cancer Centre and Cancer Innovations, Inc. for the financial support. The instrument facility was supported by Research Facilities Improvement Grant No. C06 RR-16572-01 from the National Centre for Research Resources, National Institutes of Health.