Development of optical-based nanobiosensors for body fluid identification

The detection and identification of body fluids within the context of a crime scene investigation is essential for providing information relating to potential activities which may have taken place within that scene. A crime scene investigator or a forensic scientist needs to recognise and then collect relevant biological evidence at a scene or later in the laboratory. However, most current methods used in the field and within laboratories are presumptive indicative tests which may suffer from low sensitivity, poor selectivity and more importantly, may be destructive for subsequent DNA profiling. The advent of nanotechnology has led to the development of new analytical sensor devices that have found applications in the defence and security sector, medicine, food and in the environmental industry. The fabrication of biosensors with nanomaterials has been extensively used in the development of colorimetric and fluorescence-based detection systems. To overcome the problems associated with existing test methods for body fluid identification, this PhD project sought to develop novel optical-based affinity nanobiosensors for body fluids using nanomaterials and biological recognition receptor elements. This PhD has developed three optical-based nanobiosensors for blood and saliva identification. First was developed a colorimetric aptamer-based magnetic magnetite nanocube-gold nanorod (MNC-AuNR) hybrid nanobiosensor for Hb detection in blood. This nanobiosensor used the catalytic activity of MNC and the high specificity of the anti-Hb aptamer to detect Hb through a colour change reaction. Then a fluorescence aptamer-based ZnSSe alloyed quantum dot-gold nanoparticle (QD-AuNPs) nanobiosensor was fabricated for lysozyme detection in saliva using the plasmonic metal-enhanced fluorescence of the nanohybrid. Lastly, a fluorescence-based molecular imprinted polymer-coated SiO2-shell Au-doped ZnInSeS QDs (QD@MIP) nanobiosensor was developed to detect haemoglobin in the blood through a fluorescence enhancement signal. Quantitative and selectivity studies showed that the three novel nanobiosensors were highly efficient towards haemoglobin and lysozyme detection. The nanoprobes showed that they can be employed for real saliva and blood identification with higher selectivity and sensitivity than current presumptive tests used by forensic practitioners.