1. Selective and Sensitive Sensing of
L-Aspatic Acid and L-Glutamic Acid Employing Dansyl Functionalized Dextran
Weerachai Nasomphan1, Srung Smanmoo2 and Pramuan Tangboriboonrat1*
1Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
2Bioresources Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC) Thailand Science Park, Klong luang, Pathumthani, Thailand

2. Advantages of L-Asp & L-Glu
Biological roles
Acidic amino acid
Biosynthesis precursor
Amino acid metabolism
Human nutrition
Identifying diseases
L-Aspatic acid
L-Glutamic acid
(L-Asp)
(L-Glu)
High level
in blood
Diabetic
Stroke
Okamoto H. et al. J Sep Sci 2005; 28: Yen K. et al. Talanta 2007; 71: 2007.

3. Standard Method Vs Chemosensor
Disadvantages:
Expensive
Complicate
Skillful
Time consuming
UV-Vis
HPLC
ICP-MS
Fluorescence
Chemosensor
Advantages:
High selectivity*
High sensitivity**
Low cost
Simple-to-use
Naked-eye diagnostic tools
*,** depend on chemical property of sensor

4. Binding subunit “Ionophore” Fluorescence quenching/enhancement
Design of Chemosensor
Signaling subunit
Binding subunit “Ionophore”
Amino
Acid
Fluorescence quenching/enhancement
Color change
Fluorophore
Acid-base interaction
Hydrogen bonding
Metal-ligand coordination
Van der Waals and physical interaction
Interactions
Ramon M. et al. Chem Rev 2003; 103: 11.
Suslick KS. et al. Tetrahedron 2004; 60:

5. Molecular Vs Polymeric Chemosensors Polymeric chemosensor
Signal
Enhancement
Polymeric chemosensor
Molecular chemosensor
Conjugated system
Advantages
High sensitivity
Solubility enhancement
Non-Conjugated system
Long Y. et al. Macromolecules 2009; 42: 6501.
Malashikhin S. et al. J Am Chem Soc 2008; 130:

6. Non-Conjugated Polymer: Dextran Probe
Polymeric template: Dextran
(Water soluble
template)
Binding
Unit
Dansyl Dextran Conjugate
(DD)
Acidic amino acids (AAs)
L-Asp
L-Glu
Fluorophore
Signaling
Unit
(Acidic Sensitive)

7. Internal Charge Transfer (ICT) Process
Interaction of Dextran Probe & Amino Acid
Hydrogen bonding DD
Charge-Charge interaction
ICT
“ Fluorescent on ”
Internal Charge Transfer (ICT) Process
“ Fluorescent off ”
Ohtake K. et al. J Control Release 2002; 82: 263.
Yen K. et al. Talanta 2007; 71: 2007.

8. Objective To synthesize a polymeric chemosensor for L-Asp and L-Glu
based on dansyl hydrazine dextran conjugate (DD)
via fluorescence quenching

9. Synthetic scheme of dextran dansylhydrazine conjugate
Non-Conjugated Polymer: DD
Synthetic scheme of dextran dansylhydrazine conjugate
Molecular weight (kDa) = 2600
Polydispersity index (Mw/Mn) = 1.33

10. Fluorescence (FL) spectra of DD upon the addition of 20 amino acids
Selectivity of DD
Fluorescence (FL) spectra of DD upon the addition of 20 amino acids
Conditions:
[DD] = 5 × 10-6 mol L-1
[Amino Acids] = 25 × 10-3 mol L-1
1% PBS buffer
Ex = 275 nm.
(L-Asp)
(L-Glu) DD
Fluorescence image

11. DD Sensitivity to L-Asp
DD + L-Asp DD
FL change of DD in the presence
of various concentrations of L-Asp
Limit of detection (LOD)
10 µM
Conditions:
[DD] = 5 µM (1% PBS buffer)
[Amino Acids] = mM

12. DD Sensitivity to L-Glu
DD + L-Glu DD
FL change of DD in the presence
of various concentrations of L-Glu
Limit of detection (LOD)
50 µM
Conditions:
[DD] = 5 µM (1% PBS buffer)
[Amino Acids] = mM

13. Conclusions
A new FL sensor, Dansyl Hydrazine dextran conjugate (DD) was prepared to use as a selective polymeric chemosensor for amino acids.
The FL quenching of DD exhibited excellent degree of selectivity towards L-Asp and L-Glu.
DD is highly soluble in water, it prompts the application for the intracellular sensing of L-Asp and L-Glu.

14. Acknowledgements Prof. Dr. Pramuan Tangboriboonrat, Mahidol University
Dr. Srung Smanmoo, BIOTEC
Faculty of Science, Mahidol University
Bioresources Research Unit (BRU)

15. Thank you for
your kind attention