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Protein-Resistant Electrode for Biosensing

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Protein-Resistant Electrode for Biosensing Protein-resistant Electrode for Biosensing by Cheng Jiang A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy School of Chemistry, Faculty of Science 2016 PLEASE TYPE THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Jiang First name: Cheng Other name/s: N/A Abbreviation for degree as given in the University calendar: PhD School: School of Chemistry Faculty: Science Title: Protein-resistant electrode for biosensing Abstract 350 words maximum: (PLEASE TYPE) Electrochemical biosensors are of enormous interests in a variety fields including clinical diagnosis and food analysis. However, in biological media the nonspecific adsorption of proteins, referred to as biofouling, interferes with the performance of such devices in terms of reducing sensitivity and selectivity. Hence, antifouling coatings are needed for electrochemical sensors to deliver on their potential when it comes to biologically derived samples. The common effective solutions to the critical issue of biofouling involves using poly(ethyleneglycol) (PEG) or oligo(ethyleneglycol) (OEG)-alkanethiol layers. This is because a highly compressed hydration layer can be formed with these monolayers which is believed to be the reason this chemistry can effectively preventing nonspecific adsorption of protein. However, the use of such long chain self-assembled monolayers (SAMs) or polymeric layers on electrodes is not desirable because such polymers form a high impedance layer on the electrode, effectively passivating the electrode. Surface modifying layers that do not passivate the electrodes typically are also not effective at providing protection against biofouling. In this concern, we have developed an aryldiazonium salt based mixed layer platform. Phenyl phosphorylcholine (PPC) and phenyl butyric acid (PBA) are used for antifouling and bio- recognition component linkage, respectively. Such surface chemistry was demonstrated to be a versatile platform with good antifouling, low impedance and controllable surface composition properties, and was successfully applied to the development of an immunosensor for detecting tumor necrosis factor α in whole blood. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). …………………………………………………………… ……………………………………..……………… ……….……………………...…….… Signature Witness Signature Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: THIS SHEET IS TO BE GLUED TO THE INSIDE FRONT COVER OF THE THESIS i COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed ……………………………………………........................... Date ……………………………………………........................... AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed ……………………………………………........................... Date ……………………………………………........................... ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …………………………………………….............. Date …………………………………………….............. Acknowledgements I would like to express my sincere gratitude to my supervisor Scientia professor Justin Gooding for his support and guidance throughout my PhD life. PhD research experience is like a cruise adventure in ocean of knowledge with so many uncertainties. He is like a light tower, leading my right direction and showing me brightness in heart. His profound knowledge and rigorous scholarship impressed me a lot, always giving me power and confidence to overcome any rainstorms and hurdles. His patient guidance on teaching me how to find a gap between current research work and what we need to achieve so as to design PhD project, how to do scientific writing, how to give good presentation in a conference have taught and encouraged me to continue studious and rigorous work in future career. I would like to acknowledge professor Brynn Hibbert, professor Xuzhi Zhang, professor Guozhen Liu, our postdoctors Muhammad Alam, Nadim Darwish, Xiaoyu Cheng, Stephen Parker, Alexander Soeriyadi, Roya Tavallaie, Abbas Barfidokht and also Xin Chen, Saimon Moraes Silva, Fei Han, Manchen Zhao, Sanjun Fan, Yanfang Wu, Parisa S. Khiabani for their helpful discussions and advices throughout my PhD project. Many thanks to Safura Taufik, Yong Lu, Ying Yang, Maryam Parviz, we accompanied with each other during the past 4-year PhD period and they helped a lot in research work and daily life. Appreciate to Dr. Yuanhui Zheng, who is always with positive energy and willing to share and help me since he came to our group. His optimistic attitude and sharp insights towards research would influence me a lot in my future career. All other Gooding group members are greatly appreciated for their kind help and helpful talk, makes my PhD period meaningful and colorful. My beloved parents, relatives and friends always give selfless mental encouragement. My beloved wife Manchen Deng, who made a great sacrifice to wait until my PhD graduation, she is always encouraging me to be fearless to face any situations and iv problems when studying overseas. Although we are separated thousands of miles from each other but our hearts always keep close without distance, our love passed the 4-year test! Special thanks to Tuition Fee Scholarship (TFS) and China Scholarship Council (CSC) for financial support of my PhD study. v Abstract Electrochemical biosensors are of enormous interests in a variety fields including clinical diagnosis and food analysis. However, in biological media the nonspecific adsorption of proteins, referred to as biofouling, interferes with the performance of such devices in terms of reducing sensitivity and selectivity. Hence, antifouling coatings are needed for electrochemical sensors to deliver on their potential when it comes to biologically derived samples. The common effective solutions to the critical issue of biofouling involves using poly(ethyleneglycol) (PEG) or oligo(ethyleneglycol) (OEG)- alkanethiol layers. This is because a highly compressed hydration layer can be formed with these monolayers which is believed to be the reason this chemistry can effectively preventing nonspecific adsorption of protein. However, the use of such long chain self- assembled monolayers (SAMs) or polymeric layers on electrodes is not desirable because such polymers form a high impedance layer on the electrode, effectively passivating the electrode. Surface modifying layers that do not passivate the electrodes typically are also not effective at providing protection against biofouling. In this concern, an aryldiazonium salt based mixed layer platform have been developed. Phenyl phosphorylcholine (PPC) and phenyl butyric acid (PBA) are used for resistance of nonspecific protein adsorption and linkage of bio-recognition component, respectively. Such surface chemistry was demonstrated to be
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