Development of Functional Material Scaffolds for Sensing Applications
Type of Degreedissertation
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Developments in the field of chemical and biological sensors call for sensitive and selective sensing surfaces to provide consistent information about target analytes. Since such sensors are mostly operating in complex multi-component environments, their interaction with interferent can have deleterious effects on their activity. Thus, stable sensing surfaces form the most critical aspect of a biosensor design and their development requires reliable surface morphology and chemistry for allocation of chemical and bio-recognition elements. Studies in this dissertation were aimed at developing modified titanium dioxide nanoparticles using techniques such as silanization and cross-linking to act as scaffolds for stable immobilization of proteins via direct covalent bonding or encapsulation in silica particles during its bio-inspired lysozyme mediation. Spatially defined presence of protein-reporter agents, on transparent titania nanoparticles coated on glass slides, enabled the development of fluorimetric array biosensors for simultaneous detection of multiple analytes. The different approaches used to develop the functional layers were compared in terms of biosensor sensitivity and stability. Organophosphorus hydrolase (OPH) was used as the model biosensing enzyme to show the potential application of the above chemistries for the detection of organophosphate (OP) neurotoxins. Reporter pH responsive fluorophores conjugated to enzyme transduced the catalytic hydrolysis of OPs by OPH, into a measurable optical signal. The developed sensor has potential applications for the detection of OP pesticides in environmental samples. As an extension to OP detection, the principle of molecular recognition based on thermodynamic-complex formation of fluoride ions with aluminum(III) octaethylporphyrin contained in a plasticized film with chromoionophore was exploited for the detection of organophosphofluoridates like Diisopropyl Fluorophosphate (structural analogue of Sarin and Soman chemical nerve agents). Studies also included the activation of magnesium silicate (florisil) particles with reactive chemicals for the development chemical sensors. Modified Nash reagent was utilized in the form of fluoral-P and adsorbed onto florisil micro-particles. These pre-activated particles were attached to the glass slide surface via tape and via dispersion in polydimethyl siloxane (PDMS) matrix. Fluorimetric quantification of photoluminescent product of formaldehyde and fluoral-P activated florisil, namely, 3,5-diacetyl-1,4-dihydrolutidine (DDL) allowed for the detection of formaldehyde.