title: The interaction of polymer-coated magnetic nanoparticles with seawater.
abstract: Laboratory studies were conducted to evaluate the interaction between bare and polymer-coated magnetic nanoparticles (MNPs) with various environmentally relevant carrying solutions including natural oceanic seawater with and without addition of algal exopolymeric substances (EPS). The MNPs were coated with three different stabilising agents, namely gum Arabic (GA-MNP), dextran (D-MNP) and carboxymethyl-dextran (CMD-MNP). The colloidal stability of the suspensions was evaluated over 48 h and we demonstrated that: (i) hydrodynamic diameters increased over time regardless of carrying solution for all MNPs except the GA-coated ones; however, the relative changes were carrying solution- and coat-dependent; (ii) polydispersity indexes of the freshly suspended MNPs are below 0.5 for all coated MNPs, unlike the much higher values obtained for the uncoated MNPs; (iii) freshly prepared MNP suspensions (both coated and uncoated) in Milli-Q (MQ) water show high colloidal stability as indicated by zeta-potential values below -30 mV, which however decrease in absolute value within 48 h for all MNPs regardless of carrying solution; (iv) EPS seems to "stabilise" the GA-coated and the CMD-coated MNPs, but not the uncoated or the D-coated MNPs, which form larger aggregates within 48 h; (v) despite this aggregation, iron (Fe)-leaching from MNPs is sustained over 48h, but remained within the range of 3-9% of the total iron-content of the initially added MNPs regardless of suspension media and capping agent. The environmental implications of our findings and biotechnological applicability of MNPs are discussed.
authors: Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK. Electronic address: enik@pml.ac.uk.
authors: Enikö
authors: E
authors: Kadar
authors: REQUIMTE, Departamento de Química, Faculdade de Ciências e Technologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors: Iris L
authors: IL
authors: Batalha
authors: School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors: Andrew
authors: A
authors: Fisher
authors: REQUIMTE, Departamento de Química, Faculdade de Ciências e Technologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors: Ana Cecília A
authors: AC
authors: Roque
mesh_terms: D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D058185:Magnetite Nanoparticles; D011108:Polymers; D014874:Water Pollutants, Chemical
keywords: Aggregation; Bioavailability; Dissolution; Iron oxide; Magnetic nanoparticles