Peptide functionalisation and characterisation of gold (nano) surfaces

• Main Author: Aitken, Lynsey A.
• Published: University of Strathclyde 2016
• Subjects: 572
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687050

This work describes the successful preparation and characterisation of peptide functionalised gold surfaces, with a focus towards developing enzyme response applications. The serine protease, elastase, was the primary focus of this work; however, all of the systems described herein have the utility to be modified for alternative proteolytic enzymes. 1.0 provides background and context to the work presented in this thesis and additionally describes the layout of the work to be presented. 2.0 reviews the literature on enzyme responsive nanomaterials (ERNMs), providing a brief overview of the design considerations, routes to functionalisation and characterisation techniques which must be taken into account when developing such materials. 3.0 describes the development of a method for the step-wise functionalisation of planar gold surfaces with short peptide derivatives, which contained elastase cleavable moieties. (±)-α-lipoic acid was utilised to provide an anchor to the gold surface and conventional Fmoc chemistry used to prepare the peptide sequences. The fluorenyl functional group provided a convenient marker for surface analysis, enabling the verification of each synthetic step by ToF-SIMS, XPS and LDI-ToF MS. Step-wise solid-phase synthesis on the gold surface is a facile means of preparing peptide-conjugates, providing a method whereby no additional purification or final “grafting-on” steps are required. The use of LDI-ToF MS and ToF-SIMS in tandem ensured confidence in the stepwise synthesis method. These techniques provided complimentary data to one another through the analysis of both the fully desorbed peptide derivative and molecular fragments respectively. 4.0 presents investigations into the use of SERS as a technique to follow the elastase responsive system developed in 3.0. The nanostructure surface of Klarite, a commercially available SERS substrate, was functionalised using the same methodology and proof-of-concept work towards a SERS-active system was detailed. 5.0 discusses the development of the first elastase detection system found on gold nanoparticles, progressing on from the work on flat surfaces presented in 3.0 and 4.0. The remainder of the work presented in the chapter focuses on the development of a potentially more robust system, with several target molecules successfully synthesised; however, none of these molecules provided an elastase responsive system. 6.0 then provides conclusions of the work carried out, followed by a description of potential future investigations that could be carried out. Finally, 7.0 provides a detailed description of the experimental methodology followed, providing evidence for the findings and conclusions presented in 3.0-6.0.