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Title: Engineering of oligopeptide-modified surface for metal ion adsorption and sensing applications
Authors: BI XINYAN
Keywords: oligopeptide, immobilization, surface chemistry, metal ion adsorption, chemical sensor, biosensor
Issue Date: 7-Aug-2009
Citation: BI XINYAN (2009-08-07). Engineering of oligopeptide-modified surface for metal ion adsorption and sensing applications. ScholarBank@NUS Repository.
Abstract: Surfaces presenting unique functionalities have found tremendous applications, such as separation and sensor design. Unlike traditional self-assembled monolayers (SAMs) offering limited choices, the surfaces modified with custom-made oligopeptides are versatile, because the sequences of oligopeptides can be tailored for binding metal ions and biomolecules with high specificity. First, past studies have demonstrated that oligopeptides with particular side groups are able to complex metal ions with high sensitivity and selectivity, hence, silica gel modified with Gly-Gly-Gly or Gly-Gly-His can adsorb Cu2+ with high selectivity, even in the presence of Zn2+. This principle was also applied to modify silicon nanowire (SiNW) to create a sensitive Cu2+ sensor. Secondly, it is known that to fabricate metal ion sensors, the oligopeptides with specific sequences need to be immobilized on the surface with a well-defined orientation to keep their functions. In this thesis, we demonstrated that an N-terminal cysteine label lead to well-oriented immobilized oligopeptides. Thus, SiNWs modified with a Pb2+-sensitive oligopeptide can be used to detect Pb2+ in the presence of Cu2+. Finally, we exploited interactions between liquid crystals (LCs) and immobilized oligopeptide for creating real-time enzyme biosensors. The detection principle is based on the changes of the anchoring of LCs supported on surfaces, because the anchoring of LCs can be easily affected by the chemical compositions and molecular-level structures of surfaces. Our results show that the enzymatic cleavages of oligopeptide substrates can lead to changes in the optical appearance of LCs. Moreover, because anchoring of LCs is controlled by a fine scale of energetics, it is possible to couple the orientations of LCs to surfactants, lipids, proteins, and synthetic polymers adsorbed at the aqueous/LC interface. Based on this principle, we sought to design a new LC based pH sensor and study the feasibility of using theLC based pH sensor for monitoring H+ released from enzymatic reactions in real time. These new principles may offer tremendous opportunities for developing next-generation biosensors.
Appears in Collections:Ph.D Theses (Open)

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