Fluorometric estimation of amino acids interaction with colloidal suspension of FITC functionalized graphene oxide nanoparticles

A hydrosol approach developed to synthesize fluorescence quenched fluorescein isothiocyanate ( FITC) functionalized colloidal suspension of graphene oxide nanoparticles ( GONP). UV-vis spectroscopic measurements showed characteristic peak at 236 nm and 300 nm due to pi-pi* interaction in C=C and n-pi* transition in C=O bond of GONP, respectively. Attenuated total reflectance-Fourier transform infrared ( ATR-FTIR) spectra showed reduced intensity of 1429 cm(-1) IR band of GONP due to the electrostatic and pi-pi interactions of FITC with GONP in FITC-GONP. ATR-FTIR spectra of different amino acid cofunctionalised FITC-GONP showed an increase in the FTIR band intensity at 1429 cm(-1) which was significantly reduced due to electrostatic/pi-pi interactions of FITC with GONP in the absence of the amino acids. A peak at 1084 cm(-1) in ATR-FTIR spectra appears which confirms the interaction between amine group of amino acids and COO-groups at GONP surface. The FITC interaction with GONP lead to fluorescence resonance energy transfers ( FRET) and resulted in a liner decrease in the FITC fluorescence with an increase of GONP concentration. An increase in the reappearance of FITC fluorescence observed while the amino acid concentration was increased in co-functionalised FITC-GONP. The quantified amount of reappeared fluorescence of FITC in amino acid co-functionalised FITC-GONP depends on the concentration, polar and non-polar nature of amino acids. The reappearance of FITC from the surface of FITC-GONP with the addition of amino acid was found to be consistent with the organic substitute, size of amino acids and their functionalities. Therefore, FRET based method using FITC-GONP colloidal suspension may have potential application in determining the binding nature of biomolecules with GONP for biomedical applications. (C) 2016 Elsevier B. V. All rights reserved.