BIOSENSOR FOR THE SELECTIVE DETECTION OF BIOMOLECULES

Abstract

Cancer remains a leading cause of death in Qatar. Arab Nationals, including Qatar, develop breast cancer (BC) at least a decade earlier than their counterparts in other countries. Breast cancer accounts for one-third of malignancy among Qatari women, and its incidence is increasing progressively. Early diagnosis and monitoring have a substantial impact on cancer patients. It can ensure a fast and successful treatment that increases survival rates. An innovative cancer diagnostic device that provides sensitive, specific, and accountable quantitative results, is a gap that needs to be researched. Nanotechnology provides rapid, reproducible, and highly sensitive cell detection. That can detect various targets, including protein biomarkers, nucleic acids, and cancer cells. Single-molecule detection continues to transform sensing technologies. This work uses blood-based biomarkers (exosomes) in a biosensor. Nano-sized enclosed microscopic particles known as exosomes are used as a novel diagnostic tool in cancer detection techniques. Exosomes can be found in the blood circulation; thus, it serves as a cargo carrier of molecular constituents of their cell of origin. It can accurately distinguish between patients with precursor forms of cancer. The biosensor that uses mesoporous gold film (MPG) and magnetic beads (MB) can overcome conventional cancer diagnosis limitations. Mesoporous gold (MPG) is a plasmonic metallic nanostructure that amplifies the targeted molecules' signal. Magnetic Beads (MB) have high affinity and specificity, and they have been widely used to isolate, separate, and purify many types of proteins. Thus, it was used in this study as an effective technique to detect exosomes. This thesis aims to develop a reliable diagnostic device that can frequently detect potential breast cancer biomarkers. The proposed device can, efficiently, and at low cost, identifies MCF-7 exosomes from a cell culture media. The research is divided into three main parts; first, the separation of the exosomes; next, the fabrication of the mesoporous gold substrate (MPG) and the preparation of the magnetic beads (MB); lastly, the integration of the exosomes with the mesoporous gold substrate (MPG) and the magnetic beads (MB). This work showed that fabricated porous gold substrates could capture biomolecules of size less than 150 nm. SEM results showed exosomes' presence as a circular shape with a size between ~ 30-150 nm. Specific detection of MCF-7 exosomes occurs because of specific binding between specific antibodies and the target exosomes. The average number of exosomes in the porous gold substrates treated with nitric acid for 10 min was almost doubled than the one treated with nitric acid for 5 min due to the increase in the pore's sizes. The pore size relationship and the fluorescence intensity showed that porous gold substrates had more captured exosomes than the nonporous substrate. Moreover, when using the different antibodies in the control substrate, fewer exosomes were captured. When using magnetic beads, we were able to quantify the fluorescence intensity changes from the fluorescent probes' interaction with the analyte and compare it with the initial concentration. The exosomes’ sensitivity and quantitative detection were achieved by measuring the change in the fluorescence intensity. The fluorescence intensity was proportional to the immobilized exosomes’ concentration. However, in the absence of exosomes, the fluorescence intensity was lower. Moreover, the fluorescence intensity rate correlates with the concentrations of the magnetic beads. Our results indicated a quantitative selectivity for biomolecules detection.

Date of Award	2022
Original language	American English
Awarding Institution	HBKU College of Science and Engineering