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Geetha Bai, Renu (2017) Strategies in the fabrication of modified graphene nanomaterials: prospects in the electrochemical sensing of biomolecules and anticancer effects. PhD thesis, University of Nottingham.

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Abstract

Being one of the highly explored nanomaterials, graphene and derivatives are in the limelight of scientific research. The quest of mass production of graphene in a fast, eco-friendly and economical way lead to different greener synthesis approaches with reduced risk and harm to the environment. Here through this investigation, different greener approaches in the preparation of graphene and its derivatives were analysed. Moreover, the biocompatibility of the product is analysed for ensuring the safety while introducing as a biomaterial to a living system.

The initial part of the study, a hydrothermal reduction method was utilized to reduce graphene oxide (GO) to create reduced graphene oxide (RGO) without using any toxic reducing agents. Following this, with the use of a variety of ultrasonic cavitation, a profoundly stable (>2 year) few layer thick RGO nanodispersion was generated without employing any stabilizers. The excellent stability at physiological pH promotes its utilization of RGO dispersion as a carrier of Paclitaxel (Ptx) – an anticancer drug. The in vitro cytotoxicity analysis of the Ptx loaded RGO nanodispersion revealed the potential of the nanodispersion as a suitable drug carrier. RGO dispersion is also utilized in combination with glucose oxidase (GOD) enzyme, for the detection of glucose. RGO-GOD modified working glassy carbon (GC) electrode was evaluated to analyze the redox reaction in the presence of oxygen. This investigation demonstrated the potential of the exceptionally stable RGO nanodispersion in nano drug delivery and electrochemical sensing applications.

Development of RGO nanodispersion through ultrasonication lead to the idea of creating graphene (G) sheets from graphite through ultrasonic exfoliation. Upon success of the G production, the next part of the research focused on the sonochemical development of graphene-gold (G-Au) nanocomposite through simultaneous exfoliation of graphite as well as the reduction of gold chloride. The G-Au nanocomposite was well characterized and utilized to fabricate an electrochemical sensor for the selective detection of nitric oxide (NO), a critical biomarker associated with numerous physiological and pathological abnormalities. The cytotoxic effects of the sonochemically synthesized G, AuNPs and G-Au nanocomposite were conducted on mammalian cell lines revealed the selective cytotoxic effects towards cancer cells and biocompatible nature towards normal cells. Biocompatibility results supported the use of the G-Au nanocomposite system for anticancer applications such as drug delivery, imaging, etc.

Next part of the research used a natural reducing agent for reducing GO to RGO, utilizing a medicinal mushroom- Ganoderma lucidum (G.l.) extract. Similarly reduced graphene oxide-silver (RGO-Ag) nanocomp osite also was prepared by the facile one-step synthesis method. The properties of RGO-Ag obtained were well characterized and tested for sensing of hydrogen peroxide (H2O2), a cancer biomarker. Similarly, the antimicrobial potential of RGO-Ag was tested on different bacterial species. Furthermore, the cytotoxicity of RGO-Ag was tested on mammalian cell lines exhibited good biocompatibility. The sensing studies revealed the potential of RGO-Ag in H2O2detection. The antibacterial studies of RGO-Ag displayed comparable results with standard antibiotic Chloramphenicol. The antibacterial effects, sensing potential and selective toxicity towards cancer and normal cells make this RGO-Ag nanocomposite a promising candidate for future health care industry.

Last part of the study focused on an electrochemical biosensor for the detection of cancer. Nanomaterials in combination with biomolecules are used in drug delivery, imaging and sensing applications by targeting the overexpressed cancer proteins such as folate receptors (FR), to control the disease from progressing to advanced levels. Here, a biocompatible RGO nanosheets (produced using G.l. extract) in combination with folic acid (FA), a vitamin with high bio-affinity to FR, is utilized for the development of an electrochemical sensor for the detection of cancer. The formation of RGO-FA nanocomposite was confirmed by various characterization techniques. The RGO-FA modified GC electrode was analysed by differential pulse voltammetry (DPV) for its accurate detection towards FR. This RGO-FA modified electrode showed good specificity and reliability when tested against similar interfering biomolecules. This RGO-FA sensor offers a great promise to the future medical industry through its highly sensitive detection of FR in a fast, reliable and in an economical way.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Sivakumar, Manickam Muthoosamy, Kasturi
Keywords:	graphene, carbon, nanomaterials, Nanocomposite, electrochemical sensors, anticancer, biocompatibility, green chemistry, folic acid, reduced graphene oxide, silver, gold, ultrasonication
Subjects:	T Technology > TP Chemical technology
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Engineering > Department of Chemical and Environmental Engineering
Item ID:	39647
Depositing User:	GEETHA BAI, RENU
Date Deposited:	15 Nov 2017 07:08
Last Modified:	18 Feb 2021 04:30
URI:	https://eprints.nottingham.ac.uk/id/eprint/39647

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