A Magnetic Sensor Based on Poly(gamma-Glutamic Acid)-Functionalized Iron Oxide Nanoparticles for Cr3+ Detection

Background: The highly sensitive and selective detection of Cr3+ is critical. Objective: We report the development of poly(gamma-glutamic acid) (gamma-PGA)-functionalized iron oxide nanoparticles (gamma-PGA-Fe3O4 NPs) as a magnetic nanosensor for magnetic resonance (MR) detection of trivalent chromium (Cr3+) in aqueous solution. Methods: The gamma-PGA-Fe3O4 NPs with a mean particle size of 7.3 nm, good colloidal stability and ultrahigh r(2) relaxivity (326.8 mM(-1)s(-1)) were synthesized via a facile mild reduction approach in the presence of gamma-PGA, and used for MR detection of Cr3+. Results: Upon exposure to Cr3+, the gamma-PGA-Fe(3)O(4)NPs aggregated into nanoclusters as verified by dynamic light scattering due to the coordination of Cr3+ with gamma-PGA side-chain carboxyl groups, resulting in the decrease in their transverse relaxation time. This MR signal change enables detection of Cr3+ in a concentration range of 0.4-1 nM. We also show that the gamma-PGA-Fe(3)O(4 )NPs have an excellent selectivity toward Cr3+ and a high recovery percentage of 83.8% or above. Conclusion: This study thus demonstrates that the developed y gamma-PGA-Fe3O4 NPs may be used as a nanoprobe for MR sensing of Cr3+ in water environment.