Development of semiconductor metal oxide-based sensors functionalized by catalytic nanoparticle provided in an Apo-Ferritin for detection of biomarkers in exhaled breath

Abstract

The importance of developing simple and accurate diagnostic technologies for daily monitoring of patients’ physical conditions is gaining more attention every year. Exhaled breath analysis is a very powerful tool for clinical diagnostics, given that it is non-invasive, painless, easily repeated and generally agreeable to patients. Chemoresistive sensors, based on semiconducting metal oxides (SMOs), are receiving a great deal of attention for exhaled breath analysis due to their facile, rational design, low cost and ability to detect a large number of gases. However, because the human breath is fully humidified and contains thousands of interfering gas species, it becomes very challenging to adopt SMO-based sensing layers exhibiting both high sensitivity and selectivity in the detection of sub part per billion (p.p.b.) level trace target biomarker gases. Given that the gas sensing mechanism is strongly associated with surface reactions between trace target gases and sur-face chemisorbed oxygen species on the sensing layers, maximization of the surface reaction sites of SMOs combined with optimized catalytic functionalization are the foremost criteria needed to address these challenges. In this thesis, facile and rational method were proposed for synthesizing bio-inspired noble metallic (Pt,Pd, and Rh) and bimetallic (PtM where M=Pd, Rh and Ni) NPs via protein cage encapsulating route as new class of active catalyst in the SMO based sensor and propose their potential applications in accurate breath sensing. Using the nanoscale cavity of protein i.e. apoferritin, we achieve the well-dispersed catalytic nanoparticles (NPs) with very small mean size (less than 3 nm). More importantly, by employing electrospinning, the bio-inspired catalytic NPs are well-decorated without aggregation on one dimensional porous WO3 nanofibers (NFs) that assures a high surface area, good gas accessibility. Thus, this unique sensing material with bio-inspired catalytic NPs can be obtained, enabling ultrasensitive and highly selective detection even toward p.p.b. level of biomarker gases and providing sensor arrays to discriminatively identify individual breath samples, consisting of simulated biomarker and controlled breath. Moreover, wearable breath sensing module that can be integrated with mobile devices was developed for application in portable and real-time diagnosis. This thesis propose high potential of SMO-based sensing layer functionalized with bio-inspired catalysts for application in breath analysis.