title: Synthesis of Co3O4nanoparticles with block and sphere morphology, and investigation into the influence of morphology on biological toxicity.
abstract: In the present study, cobalt oxide (Co3O4) magnetic nanoparticles with block and sphere morphologies were synthesized using various surfactants, and the toxicity of the particles was analyzed by monitoring biomarkers of nanoparticle toxicity in zebrafish. The use of tartarate as a surfactant produced highly crystalline blocks of Co3O4nanoparticles with pores on the sides, whereas citrate lead to the formation of nanoparticles with a spherical morphology. Co3O4structure, crystallinity, size and morphology were studied using X-ray diffractogram and field emission scanning electron microscopy. Following an increase in nanoparticle concentration from 1 to 200 ppm, there was a corresponding increase in nitric oxide (NO) generation, induced by both types of nanoparticles [Co3O4-NP-B (block), r=0.953; Co3O4-NP-S (sphere), r=1.140]. Comparative analyses indicated that both types of nanoparticle produced significant stimulation at ≥5 ppm (P<0.05) compared with a control. Upon analyzing the effect of nanoparticle morphology on NO generation, it was observed that Co3O4-NP-S was more effective compared with Co3O4-NP-B (5 and 100 ppm, P<0.05; 200 ppm, P<0.01). Exposure to both types of nanoparticles produced reduction in liver glutathione (GSH) activity with corresponding increase in dose (Co3O4-NP-B, r=-0.359; Co3O4-NP-S, r=-0.429). However, subsequent analyses indicated that Co3O4-NP-B was more potent in inhibiting liver GSH activity compared with Co3O4-NP-S. Co3O4-NP-B proved to be toxic at 5 ppm (P<0.05) and GSH activity was almost completely inhibited at 200 ppm. A similar toxicity was observed with both types of Co3O4-NPs against brain levels of acetylcholinesterase (AChE; Co3O4-NP-B, r=-0.180; Co3O4-NP-S, r=-0.230), indicating the ability of synthesized Co3O4-NPs to cross the blood-brain barrier and produce neuronal toxicity. Co3O4-NP-B showed increased inhibition of brain AChE activity compared with Co3O4-NP-S (1,5, and 10 ppm, P<0.05; 50, 100 and 200 ppm, P<0.01). These results suggested that the morphology of nanoparticle and surface area contribute to toxicity, which may have implications for their biological application.
authors.affiliation: Department of Bioengineering, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India.
authors.forename: Venkataramanan
authors.initials: V
authors.lastname: Raman
authors.affiliation: Department of Bioengineering, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India.
authors.forename: Shruthi
authors.initials: S
authors.lastname: Suresh
authors.affiliation: Department of Chemistry, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India.
authors.forename: Philip Anthony
authors.initials: PA
authors.lastname: Savarimuthu
authors.affiliation: Department of Bioengineering, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India; Department of Centre for Research on Infectious Diseases, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India.
authors.forename: Thiagarajan
authors.initials: T
authors.lastname: Raman
authors.affiliation: Department of Forensic Sciences and Toxicology, Medical School, University of Crete, Heraklion 71003, Greece; Scientific Educational Center of Nanotechnology, Far Eastern Federal University, Vladivostok 690990, Russian Federation.
authors.forename: Aristides Michael
authors.initials: AM
authors.lastname: Tsatsakis
authors.affiliation: Scientific Educational Center of Nanotechnology, Far Eastern Federal University, Vladivostok 690990, Russian Federation.
authors.forename: Kiril Sergeevich
authors.initials: KS
authors.lastname: Golokhvast
authors.affiliation: Department of Chemistry, School of Chemical & Biotechnology, SASTRA University, Thanjavur 613401, India.
authors.forename: Vinod Kumar
authors.initials: VK
authors.lastname: Vadivel
keywords: cobalt nanoparticles; morphology; nanotoxicology; oxidative stress; toxicology; zebrafish