SHORT COMMUNICATION Selective Fluorescent Detection of Aspartic Acid and Glutamic Acid Employing Dansyl Hydrazine Dextran Conjugate Weerachai Nasomphan & Pramuan Tangboriboonrat & Sutipa Tanapongpipat & Srung Smanmoo Received: 7 May 2013 / Accepted: 14 July 2013 / Published online: 15 August 2013 # Springer Science+Business Media New York 2013 Abstract Highly water soluble polymer (DD) was prepared and evaluated for its fluorescence response towards various amino acids. The polymer consists of dansyl hydrazine unit conjugated into dextran template. The conjugation enhances higher water solubility of dansyl hydrazine moiety. Of screened amino acids, DD exhibited selective fluorescence quenching in the presence of aspartic acid (Asp) and glutamic acid (Glu). A plot of fluorescence intensity change of DD against the concentration of corresponding amino acids gave a good linear relationship in the range of 1×10 -4 M to 25 × 10 -3 M. This establishes DD as a potential polymeric sensor for selective sensing of Asp and Glu. Keyword Dextran polymer . Amino acid (AA) sensor . Aspartic acid (Asp) and glutamic acid (Glu) . Dansyl hydrazine Introduction Over the past decade, the development of water-soluble dye conjugated polymer has found their various applications, e.g. sensing biological probe [1], chemotherapeutic agent [2], drug carrier [3], and sensor [4]. Due to the unique property of conjugated polymer such as increasing solubility and stability in an aqueous environment. This makes a conjugat- ed polymer applicable and practical in the field of analytical research [5–8]. Recently, we have demonstrated the applica- tion of luminol conjugated dextran as a selective fluorescent probe for arginine (Arg). The tethering of luminol moiety into the dextran template does not only increase the water solubility of luminol unit, it also provides a unique confor- mation for selective recognition of Arg [9]. Despite the importance of techniques and methods for determination of amino acids (AA), only a handful of AA sensors have been reported [10, 11]. Of all essential amino acids, aspartic acid (Asp) and glutamic acid (Glu) play important roles in many biological and physiological pathways. Acute ischemic stroke is known with the correlation with the elevated level of Glu in blood. Glu is well known for the biosynthesis of butyric acid, an important compound in the central nervous system [12, 13]. Asp is recognized for its facilitating in the tricarboxylic acid (TCA) cycle. Research studies demonstrate the use of potas- sium salt of Asp as a remedy for the treatment of heart, liver diseases and diabetes [14, 15]. In this work, we reported a novel dansyl hydrazine dex- tran conjugate (DD) as a selective polymeric sensor for Asp and Glu. The tethering of dansyl hydrazine moiety into the polymeric dextran framework enhanced the water solubility of incorporated dansyl hydrazine units. DD was employed as a selective fluorescence polymeric sensor for amino acids. In the presence of Asp and Glu, the fluorescence intensity of DD was significantly inhibited. The proposed sensing mech- anism of DD towards Asp and Glu is originated from the selective binding of either Asp or Glu to dextran. Then, the internal charge process (ICT) is inhibited, which triggers the S. Tanapongpipat : S. Smanmoo (*) Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Thailand Science Park, Phaholyothin Road, Klong Luang, Pathumthani 12120, Thailand e-mail: srung.sma@biotec.or.th W. Nasomphan : P. Tangboriboonrat Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Phyathai, Bangkok 10400, Thailand J Fluoresc (2014) 24:7–11 DOI 10.1007/s10895-013-1269-8