Green synthesized cerium oxide nanoparticle: A prospective drug against oxidative harm
Graphical abstract
Introduction
Oxidative stress has been implicated as a cause of different diseases like arthritis, cardiac disorder, diabetes, Alzheimer’s and Parkinson’s diseases, macular and retinal degeneration etc. [1], [2]. Cellular oxidative damage is mediated by ‘reactive oxygen species’ (ROS), which include free radicals such as superoxide anion (O2−), hydroxyl radical (OH), singlet oxygen (1O2) and non-free radical species like hydrogen peroxide (H2O2). Usually, antioxidants protect cells from oxidative stress, by neutralizing ROS. Most of the antioxidants are exhausted to neutralize ROS; however, cerium oxide (CeO) has an exclusive uninterrupted antioxidant activity, because cerium can cycle between the cerous (Ce3+) and ceric (Ce4+) oxidation states. CeO(III) is fast oxidized to CeO(IV) by ROS and by that CeO(III) successfully neutralizes ROS. Again CeO(IV) is slowly reduced by ROS to slip back to CeO(III), leaving oxygen vacancies in the CeO crystal lattice that becomes further reactive towards ROS [3], [4]. Thus, cycling of CeO between +3 and +4 states can uninterruptedly break down ROS.
Over the past few years there has been increasing research to explore the therapeutic capacity of nanoscale cerium oxide [5], [6], [7], [8], [9]. Thermal history of synthesis of CeO2 nanoparticles is suggested to be a factor that strongly influences the biological impact of nano-ceria. Synthesis methods, involving high temperature exposure, produce CeONP of pro-oxidative inflammatory response; on the other hand, methods requiring low heat or room temperature form particles of anti-oxidative response [10], [11]. Moreover, various chemical processes of synthesis produce nanoparticles with undesirable functionality. We, therefore, ventured to synthesize biocompatible CeONP of potential antioxidant activity.
In this communication we report about a simple, green method of preparation of CeONP at room temperature, using cerium nitrate [Ce(NO3)3] as the prime precursor and Aloe vera leaf extract as the stabilizing agent. Important physico-chemical characteristics of the synthesized CeONP have also been reported here. The organic layer of Aloe vera on the CeONP surface made it prone to interact with biological cell surface and thereby facilitated its internalization into the cell. Our CeONP has high pharmacological potential to neutralize the H2O2-induced oxidative stress in mouse neuroblastoma cells (N2A).
Section snippets
Preparation of aloe vera leaf extract
Fresh leaf pulp (30 g) of Aloe vera was boiled in 100 ml distilled water for 10 min. The aqueous extract was then filtered through Whatman filter paper-40 (GE Healthcare, UK). The filtrate was centrifuged at 15000 RPM for 15 min to remove any un-dissolved substance; the supernatant was collected and stored at −20 °C.
Synthesis of CeONP
For preparation of 10 ml CeONP suspension, 1 ml cerium nitrate (10 mM), 1 ml aqueous Aloe vera leaf extract and 7 ml Milli-Q water were first mixed at room temperature (28 °C); 1 ml of sodium
Preparation of CeONP
In the process of synthesis of the NPs, addition of cerium nitrate to Aloe vera extract made the pH of the mixture 6.0. By the subsequent addition of NaOH, pH of the mixed solution initially increased to 8.5, but after 48 h of consumption of OH− ions, it finally became 7.5 with formation of cerium oxide. Such slow oxidation might be due to the fact that NaOH was a poor oxidizing agent. In order to check whether the Aloe-Vera extract acted as the stabilizing agent, we tried to synthesize CeONP,
Conclusion
This communication reports about a new, green method of preparation of biocompatible cerium oxide nanoparticles from cerium nitrate at room temperature, using Aloe vera extract as oxidizing as well as stabilizing agent. Major amount of cerium present in CeONP was in the Ce(III) oxidation state. Incubation of CeONP with H2O2 oxidized Ce(III) to Ce(IV) quickly in the time scale of minutes, whereas prolonged incubation converted Ce(IV) to Ce(III) slowly in time scale of days, signifying the
Acknowledgements
We are indebted to the a) University of Kalyani, for supporting the first author with fellowship and some contingency, b) Department of Science and Technology, Govt. of India for the ‘FIST’ and ‘PURSE’ Programs, and University Grants Commission, Govt. of India for the SAP Program of the department, for providing different instrumental and infrastructural support and c) Mr. Goutam Sarkar, scientific assistant of Saha Institute of Nuclear Physics for the help in taking the XPS data.
References (36)
- et al.
Auto-catalytic ceria nanoparticles offer neuroprotection to adult rat spinal cord neurons
Biomaterials
(2007) - et al.
Simple, fast and cost-effective method of synthesis of cupric oxide nanoparticle with promising antibacterial potency: unraveling the biological and chemical modes of action
Biochim. Biophys. Acta
(2015) Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays
J. Immunol. Methods
(1983)- et al.
A phosphate-dependent shift in redox state of cerium oxide nanoparticles and its effects on catalytic properties
Biomaterials
(2011) - et al.
The role of cerium redox state in the SOD mimetic activity of nanoceria
Biomaterials
(2008) - et al.
Free radicals, antioxidants in disease and health
Int. J. Biomed. Sci.
(2008) - et al.
Antioxidants and prevention of chronic disease
Crit. Rev. Food Sci. Nutr.
(2004) - et al.
Influence of aging and environment on nanoparticle chemistry—implication to confinement effects in nanoceria
J. Phys. Chem. C
(2012) - et al.
Antioxidant properties of cerium oxide nanocrystals as a function of nanocrystal diameter and surface coating
ACS Nano
(2013) - et al.
Ceria nanoparticles that can protect against ischemic stroke
Angew. Chem. Int. Ed. Engl.
(2012)
Cardioprotective effects of cerium oxide nanoparticles in a transgenic murine model of cardiomyopathy
Cardiovasc. Res.
Synthesis of biocompatible dextran-coated nanoceria with pH-dependent antioxidant properties
Small
Vacancy engineered ceria nanostructures for protection from radiation-induced cellular damage
Nano Lett.
Preparation and characterization challenges to understanding environmental and biological impacts of ceria nanoparticles
Surf. Interface Anal.
Direct room temperature synthesis of valence state engineered ultra-small ceria nanoparticles: investigation on the role of ethylenediamine as a capping agent
J. Phys. Chem. C
Blue shift in ultraviolet absorption spectra of monodisperse CeO2-x nanoparticles
J. Appl. Phys.
Application of free radical diphenylpicrylhydrazyl (DPPH) to estimate the antioxidant capacity of food samples
Anal. Methods
Flow cytometric studies of oxidative product formation by neutrophils: a graded response to membrane stimulation
J. Immunol.
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