Issue 23, 2011
From the journal:

Analyst

A ratiometric fluorescent metal ion indicator based on dansyl labeled poly(N-isopropylacrylamide) responds to a quenching metal ion†

Jie Du,a   Shaojun Yao,a   W. Rudolf Seitz,*a   Nicholas E. Bencivenga,a   Justin O. Massing,a   Roy P. Planalp,*a   Randy K. Jackson,b   Daniel P. Kennedyb  and  Shawn C. Burdette*c  

* Corresponding authors

a Department of Chemistry, University of New Hampshire, Durham, NH, USA
E-mail: wrs@cisunix.unh.edu
Fax: +1 603 862 4278
Tel: +1 603 862 2408

b Department of Chemistry, University of Connecticut, Storrs, CT, USA
Fax: +1 860 486 2981
Tel: +1 860 486 6718

c Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
E-mail: scburdette@wpi.edu
Fax: +1 508 831 4116
Tel: +1 508 831 5224

Abstract

The fluorescence emission of poly(N-isopropylacrylamide) (PNIPAM) covalently tagged with a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore and an iminodiacetic acid (IDA) chelator changes with temperature and with Cu(II) complexation. Increasing the temperature above the lower critical solution temperature (LCST) causes the polymer to collapse from a coil to a compact globule. This changes the environment experienced by the fluorophore causing a shift in maximum emission wavelength from 546 to 508 nm and an increase in the ratio of emission intensity at 508 nm to emission intensity at 546 nm from 0.70 to almost 1.40. Metal ions can be sensed by working at a temperature where the uncomplexed polymer is in an expanded state due to the charges on the ligand. Complexation with a metal ion such as Cu(II) neutralizes the charges on the ligand causing the polymer to collapse. At 35 °C, the emission intensity maximum shifted from 535 to 510 nm as Cu(II) concentration was increased and the intensity ratio increased from 0.84 to 1.28. By decoupling complexation from fluorescence, we have prepared a ratiometric fluorescent indicator for a metal ion that normally quenches fluorescence. The affinity for Cu(II) was found to be thermally tunable. The log apparent formation constants for the indicator-Cu(II) complex were estimated as the half way point in the intensity ratio vs. pCu curve. The values were determined to be 4.3 at 35 °C and 3.2 at 34 °C respectively.

Graphical abstract: A ratiometric fluorescent metal ion indicator based on dansyl labeled poly(N-isopropylacrylamide) responds to a quenching metal ion

About
Cited by
Related
Download options Please wait...

Supplementary files

Article information

DOI
https://doi.org/10.1039/C1AN15479F
Article type
Paper
Submitted
09 Jun 2011
Accepted
16 Sep 2011
First published
18 Oct 2011

Analyst, 2011,136, 5006-5011

Permissions

Request permissions

A ratiometric fluorescent metal ion indicator based on dansyl labeled poly(N-isopropylacrylamide) responds to a quenching metal ion

J. Du, S. Yao, W. R. Seitz, N. E. Bencivenga, J. O. Massing, R. P. Planalp, R. K. Jackson, D. P. Kennedy and S. C. Burdette, Analyst, 2011, 136, 5006 DOI: 10.1039/C1AN15479F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements