title: Modulatory effects of Zn2+ions on the toxicity of citrate- and PVP-capped gold nanoparticles towards freshwater algae, Scenedesmus obliquus.
abstract: Gold nanoparticles (GNPs) are widely used for medical purposes, both in diagnostics as well as drug delivery, and hence are prone to release and distribution in the environment. Thus, we have explored the effects of GNPs with two distinct surface capping (citrate and PVP), and three different sizes (16, 27, and 37 nm) at 0.01-, 0.1-, and 1-mg L-1concentrations on a predominant freshwater alga Scenedesmus obliquus in the sterile freshwater matrix. We have also investigated how an abundant metal ion from freshwater, i.e., Zn2+ions may modulate the effects of the selected GNPs (40 nm, citrate, and PVP capped). Preliminary toxicity results revealed that gold nanoparticles were highly toxic in comparison to zinc ions alone. A significant modulation in the toxicity of Zn ions was not noticed in the presence of GNPs. In contrast, zinc ions minimized the toxicity produced by GNPs (both CIT-37 and PVP-37), despite its individual toxicity. Approximately, about 42, 33, and 25% toxicity reduction was noted at 0.05-, 0.5-, and 5-mg L-1Zn ions, respectively, for CIT-37 GNPs, while 31% (0.05 mg L-1), 24% (0.5 mg L-1), and 9% (5 mg L-1) of toxicity reduction were noted for PVP-37 GNPs. Maximum toxicity reduction was seen at 0.05 mg L-1of Zn ions. Abbott modeling substantiated antagonistic effects offered by Zn2+ions on GNPs. Stability and sedimentation data revealed that the addition of zinc ions gradually induced the aggregation of NPs and in turn significantly reduced the toxicity of GNPs. Thus, the naturally existing ions like Zn2+have an ability to modulate the toxicity of GNPs in a real-world environment scenario.
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
authors.forename: V
authors.initials: V
authors.lastname: Iswarya
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
authors.forename: J B
authors.initials: JB
authors.lastname: Johnson
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Parashar
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
authors.forename: Mrudula
authors.initials: M
authors.lastname: Pulimi
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
authors.forename: N
authors.initials: N
authors.lastname: Chandrasekaran
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, 632014, India. amit.mookerjea@gmail.com.
authors.forename: Amitava
authors.identifier: http://orcid.org/0000-0001-8682-4278
authors.initials: A
authors.lastname: Mukherjee
mesh_terms: D002413:Cations, Divalent / Q000737:chemistry; D019343:Citric Acid / Q000633:toxicity*; D005618:Fresh Water; D006046:Gold; D053768:Metal Nanoparticles / Q000633:toxicity*; D044444:Scenedesmus / Q000187:drug effects*; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D019343:Citric Acid; D006046:Gold; D015032:Zinc
keywords: Freshwater; Gold nanoparticles (GNPs); Scenedesmus obliquus; Size; Surface capping; Zinc ions