Biosensors for Clinical Diagnosis and Mechanistic Study of Brain Injury
Creators: name: Khetani, Sultan Noorddin
Publisher: name: Schulich School of Engineering
Year: 2021
Subjects: subject: Biosensor
subject: Electrochemical Sensors
subject: Biomarkers
subject: point-of-care
subject: Traumatic Brain Injury (TBI)
subject: Concussion
subject: CNS-injury
subject: spinal cord injury (SCI)
subject: stroke
subject: organ-on-a-chip.
subject: Engineering--Biomedical
subject: Engineering--Chemical
subject: Biology--Neuroscience

description: Bodily fluid biomarkers predicting the type and level of central nervous system injury (CNS) have been extensively studied. However, these biomarkers would be helpful to practitioners and patients if appropriate detection tools are developed. The existing clinical procedure for diagnosing CNS injuries includes qualitative assessments, predominantly questionnaire-based tests, and various imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI). These techniques are available only in tertiary care centers, and the cost of owning such is not affordable in lower or medium income countries and smaller clinics. Additionally, there is a wait time, sometimes stretching over a week, and it costs several hundred dollars. Conventional fluid-biomarker detection and monitoring techniques such as enzyme-linkedimmunosorbent assays (ELISA), Single-Molecule Array (SIMOA), as well as label-free biosensors, take longer time to compute the biochemical signals, thereby making them ineffective for point-of-care (POC) diagnostic. These technologies take a longer time (&gt;1 hour) and require multiple biological sample processing steps. To address these technological challenges, the thesis focuses on inventing newer electrochemical biosensors capable of performing rapid detection and quantification of CNS injury biomarkers and use them for clinical CNS diagnosis and management as well as and in vitro modelling of CNS injury. Five different electrochemical biosensors were developed to detect CNS injury biomarkers, including S100 calcium-binding protein B (S100?), Glial fibrillary acidic protein (GFAP), Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), Cleaved Tau-Protein (C-Tau), Neuron filament light protein (NFL), and Total-Tau (T-Tau) within the blood samples of patients and three-(3D)- in-vitro neuron-injury-on-a-chip (NIOC) model. Conductive graphene, carbon, gold (Au)-electrodes were modified by various surface modification techniques such as electrochemical grafting of amine groups, drop-casting of amine-rich polymers, covalent polymerization of amine groups, and a self-assembled monolayer of carboxylic and amine groups to increase the biomarker detection range and reduce the sensor preparation steps. The biosensors were developed on these modified electrode surfaces by creating specific chemistries to tether target-specific antibodies. A ferrocene redox reporter molecule was used to measure the concentration of target biomarkers in an equivalent electrical signal. These biosensors detected the target biomarkers within the physiologically relevant range of 100 fg/mL – 1 ?g/mL. A field-ready device, ?Drop, was developed, and the dimensions of the biosensors were modified to be used as a true PoC, remotely sensing device, addressing the clinical and technological gaps. Overall, these findings show that electrochemical biosensors can reliably detect, monitor, and quantify CNS injuries from biomarkers. This thesis:(i) Reports a class of electrochemical biosensors that are better and sensitive in performance compared to existing biomolecular analysis techniques and others in the same category, (ii) Developed a portable hand-held device for detecting CNS injuries using a blood-test, (iii) Demonstrated the PoC and the field-study use by undertaking a clinical study, and(iv) Integrated the biosensors with in-vitro neuron injury model and investigated dynamic secretion of CNS injury biomarkers while comparing these biomarkers in human clinical studies. Together, this thesis demonstrates promising clinical and research outcomes of novel electrochemical biosensors.