Colorimetric Identification of Proteins Using Gold Nanoparticles
Rogowski, Jacob Laurence
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Proteins are the principal executive biomolecules of life. Their existence is required to drive and regulate countless physiological and biochemical activities within the cell. The study of biochemistry and biology are therefore frequently concerned with monitoring the presence, distribution, and function of proteins. Conventional protein identification assays are often labour-intensive and rely on the use of expensive antibodies. The development of new protein biosensors that incorporate nanotechnology, specifically gold nanoparticles (AuNPs), may allow for facile detection, identification, and quantification of proteins due to their colorimetric output. Unlike other strategies that use antibody-functionalized gold nanoparticles, the pairing of non-functionalized nanoparticles with spectroscopic analysis may further reduce the cost of analysis and make this technology viable for consumer-level applications. This thesis focuses on the development of a gold nanoparticle biosensor for the detection, identification, and quantification of proteins. The underlying principle is based on the aggregation of non-functionalized gold nanoparticles in the presence of proteins. The physicochemical characteristics of these gold nanoparticles can be manipulated to alter their response to different proteins. In order to achieve identification based on non-specific interactions, a “chemical nose” strategy is followed, whereby different gold-nanoparticles produce different individual responses, and their collective response defines a unique signature for a given protein. A review of current literature presents the variety of biological, chemical, and physical factors that can affect protein-nanoparticle interactions, and their resultant effect on colloidal stability. This review also highlights the complexity with which these factors can interact and identifies key considerations for maintaining or controlling colloidal stability in various applications. The experiments herein address the role of shape and surfactant-type on aggregation of gold nanoparticles. Shape has previously been shown to affect protein-nanoparticle interactions, but to our knowledge has not been exploited for protein sensing applications. The role of surfactant on protein-gold nanoparticle interactions is not well studied and provides a novel avenue for investigation. This work demonstrates that both these parameters can be used to alter protein-nanoparticle interactions, thereby permitting “chemical nose”-type detection of proteins. Overall, these studies highlight how modifying protein-nanoparticle interactions can be used for the benefit of biosensing in research and clinical settings. In addition to biosensing, this manner of investigation can serve as a powerful tool to study protein-nanoparticle interactions, with widespread implications in medicine, environmental protection, and water treatment.