Fabrication and fluorescent labeling of guar gum nanoparticles in a surfactant free aqueous environment

Guar gum (GG) is a galactomannan obtained from the seeds of Cyamopsis tetragonoloba. GG polysaccharide is used in a range of technology arenas and its properties in water environment elicited a lot of interest. We report a simple acid hydrolysis technique to derive water dispersible spherical nanoparticles from GG for the first time without any stabilizing surfactant. The particles demonstrated colloidal stability and were observed to carry negative surface charges in aqueous environment. The TEM study of guar gum nanoparticles (GGn) indicated a size range of 30–80 nm with a mean at 48.8 nm. Mineral acid at apposite concentration have apparently solubilized the amorphous regions of the polymer chain leaving the crystalline parts. GGn were further covalently functionalized in aqueous environment with fluorescein isothiocyanate (FITC) using a hydroxy–propyl amine spacer group. Nanoparticle fluorescence intensity can be modulated with pH changes and a significant augmentation in the intensity was noticed at the physiologically relevant range of 6–8. New fluorescently labeled nanoparticles have potential for applications in bioimaging, biomolecular interaction studies and as a pH sensing probe in sub cellular environment.