MS, University of Cincinnati, 2015, Engineering and Applied Science: Environmental Engineering

Obtaining and transmitting real-time microbial detection data in a dynamic surface water environment requires a qualitative advancement in the field of bio-sensing. A dynamic problem requires a dynamic answer, and hydrogels have proven to be one of the more dynamic materials in research due to a number of characteristics. In this work, we harnessed a hydrogels capability to undergo volume phase transitions to prove that hydrogels are capable of mobility in free-floating environments. In this experiment, we remotely induced volume phase transitions in a hydrogel in a manner that mimicked peristaltic motion. Additionally, we functionalized the surface of a hydrogel to capture microbe cells suspended in solution. This functionalization was achieved by exploring a hydrogel's ability to adsorb cationic solutes out of solution and using those molecules as a foundation for conjugation chemistry. Finally, we incorporated electron-producing bacteria into a hydrogel to synthesize a hydrogel/bacteria hybrid biomaterial by electro-polymerizing a hydrogel over an existing bacterial biofilm on a carbon electrode. This series of proof-of-principle experiments has added valuable contributions to the decades-long research field of hydrogels while setting a foundation for a mobile autonomous hydrogel-based biosensor – a necessity for fully addressing water quality and microbial contamination concerns moving forward.

Committee: Lilit Yeghiazarian Ph.D. (Committee Chair); Margaret Kupferle Ph.D. P.E. (Committee Member); Vasille Nistor Ph.D. (Committee Member); George Sorial Ph.D. (Committee Member) Subjects: Environmental Engineering

PhD, University of Cincinnati, 2010, Engineering and Applied Science: Electrical Engineering

In this research, a new method for the self-assembly of carbon nanotubes (CNTs) using magnetic capturing and fluidic alignment has been developed and characterized. In this new method, the residual iron (Fe) catalyst at one end of the CNT was utilized as a self-assembly driver to attract and locate the CNT using magnetic forces, while the assembled CNT was aligned by the shear force induced from the fluid flow through the assembly channel. The self-assembly principles and procedures were successfully developed and the electrical properties of the assembled multi-walled carbon nanotube (MWNT) and single-walled carbon nanotube (SWNT) were fully characterized. The new assembly method developed in this work shows its feasibility for the precise self-assembly of parallel CNTs for electronic devices and nano-biosensors. In order to prepare the electrodes for the assembly of CNTs, a self-aligned nano-scale gap between multiple metal layers has been fabricated using a technique of controlled undercut and metallization and has been applied to the massive assembly of the individual CNT. The new method enables conventional optical lithography to fabricate nanogap electrodes and self-aligned patterns with nano-scale precision. The self-aligned Ni pattern on the nanogap electrode provides an assembly spot where the residual Fe catalyst at the end of the CNT is magnetically captured. The captured CNT is aligned parallel to the flow direction by fluidic shear force. The combined forces of magnetic attraction and fluidic alignment achieve the massive self-assembly of CNTs at target positions. Single walled nanotubes (SWNTs) were successfully assembled between the nanogap electrodes and their electrical responses were fully characterized, showing stable current-voltage (I-V) responses. As an application of the CNT-assembled electrode to a functional device, an on-chip optical immunosensor using CNTs with a photovoltaic polymer coating has been proposed, developed, characterized an (open full item for complete abstract)

Committee: Chong Ahn PhD (Committee Chair); Vesselin Shanov PhD (Committee Member); Marc Cahay PhD (Committee Member); Mark Schulz PhD (Committee Member); Jason Heikenfeld PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2024, Department of Civil/Environmental and Chemical Engineering

Wearable biosensors have become a valuable tool for their promising applications in personalized medicine. Cortisol is a biomarker for various diseases and plays a key role in metabolism, blood pressure regulation, and glucose levels. In this study, we fabricated an interdigitated laser-induced graphene (LIG) biosensor for the non-faradaic impedimetric detection of cortisol in sweat. A direct laser writing technique was used to produce the LIG. Gold nanoparticles (AuNPs) were electrochemically deposited onto the surface to enhance impedance response. A Self-Assembled Monolayer (SAM) was formed with on the AuNPs via 3-Mercaptopropionic acid (MPA) thiol chemistry. The carboxylic acid (-COOH) groups of the MPA were activated using EDC/NHS chemistry. Following activation, anti-cortisol antibodies were immobilized on the surface. Lastly, the LIG was incubated in the blocking agent bovine serum albumin (BSA) to avoid unwanted detection. Surface characterization of the LIG was performed at each step of modification by Electrochemical impedance spectroscopy (EIS) in a phosphate buffered saline (PBS) solution containing a 5 mM Fe(CN)3-/4- (1:1) redox couple. Further characterization of the modified LIG electrode was achieved through Fourier transform infrared (FT-IR), surfaced-enhanced Raman spectroscopy (SERS), and X-ray diffraction (XRD). The detection experiment using EIS was conducted in increasing concentrations of cortisol (0.1 pM-100 nM) in PBS. The ZMod decreased logarithmically (R2=0.97) with a 0.0085 nM limit of detection. Reproducibility was examined by percent change of ZMod at 100 nM and a 5.93%RSD (n=5) was observed. Additional analysis of sensor specificity and interference studies showed no substantial effect on detection. This research establishes the feasibility of using the gold nanoparticle decorated LIG electrode for flexible, wearable cortisol sensing devices, which would pave the way towards an end-user easy-to-handle biosensors as point-of-care diagno (open full item for complete abstract)

Committee: Byung-Wook Park PhD (Advisor); Frank Li PhD (Committee Member); Jonathan Caguiat PhD (Committee Member) Subjects: Biochemistry; Chemical Engineering; Chemistry; Engineering

Doctor of Philosophy, The Ohio State University, 2024, Materials Science and Engineering

This dissertation presents biochemical sensing systems for wearable, implantable, and high-resolution chemical sensing applications. By integrating biorecognition elements, sensing interfaces, and wireless communication strategies, we aim to provide a low-cost, reliable, and highly accurate platform for real-time biochemical monitoring in clinical and experimental settings. We first demonstrate a wireless sensing system that is miniaturized, lightweight, and compatible with common biochemical sensing interfaces. Inspired by RF tuning circuits, our simple circuit design allows battery-free operation and accurate monitoring of multiple biomarkers. The modular design separates the inductive coupling unit and the electrochemical sensing interface, minimizing strain-induced changes and ensuring accurate recording. This system is compatible with common electrochemical sensing methods, including ion-sensitive membranes (ISM), aptamer-based sensors, and enzymatic interfaces. And allow for the detection of ions, neurotransmitters, and metabolites across different application scenarios. For instance, a "smart necklace" consists of glucose sensors, that are capable of wirelessly detecting sweat glucose during exercise. A wearable skin patch monitored cortisol levels in sweat showcases the functional adaptability for stress-related biomarker detection. Additionally, a miniaturized implant prototype illustrated the potential for continuous in vivo monitoring. Our work also introduces a portable vector network analyzer (pVNA) designed to overcome the size limitations of traditional VNAs. This research provides the design and working principle for a wearable reader, which allows for real-time monitoring of resonance frequency and Q factor of the inductive coupling wireless sensor. Furthermore, we introduce “NeuroThread”, a neurotransmitter-sensing platform that utilizes the cross-section of commercially available ultrathin microwires to serve as microelectrode. This cost (open full item for complete abstract)

Committee: Jinghua Li (Advisor); Heather Powell (Committee Member); Pelagia-Irene Gouma (Committee Member) Subjects: Engineering; Materials Science; Nanoscience; Neurosciences

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2024, Photochemical Sciences

This study explores advanced methodologies in biosensing and protein labeling, focusing on the synergistic application of gold nanoparticles (AuNPs), surface plasmon resonance (SPR), and site-specific protein labeling using Fluorescein isothiocyanate (FITC) conjugation facilitated by aptamers. The use of AuNPs coated with DNA aptamers enables label-free colorimetric assays for specific proteins, including PD-L1, lysozyme, and the S1/S2 spike proteins of SARS-CoV-2, leveraging AuNPs' optical properties to detect binding events through observable color changes. Surface plasmon resonance (SPR) is critically examined for its role in real-time, label-free analysis of biomolecular interactions, emphasizing its capacity to quantify binding kinetics and affinity constants essential for biosensor development. Additionally, the method for site-specific FITC labeling of proteins, exemplified with lysozyme, demonstrates novel aptamer-mediated strategies to selectively block non-target lysine residues, ensuring precise and reproducible labeling necessary for fluorescence-based assays. These integrated approaches showcase significant advancements in molecular diagnostics and therapeutic monitoring, offering versatile tools for enhancing sensitivity, specificity, and reliability in biomedical research and clinical applications

Committee: Xiaohong Tan Ph.D (Committee Chair); H Peter Lu Ph.D (Committee Member); Malcolm Forbes Ph.D (Committee Member); James Metcalf Ph.D (Other) Subjects: Biochemistry; Biophysics

Doctor of Philosophy, University of Toledo, 2022, Physics

In this thesis we consider two different types of all-optical sensors which may be used to determine a biological sample's composition by accurately measuring its refractive index (RI). In particular, we present and discuss the design of a novel planar geometry directional coupler which may be tuned to maximize its sensitivity over a given range of values of the sample's refractive index (RI). We also discuss the design of a long-range surface plasmon sensor whose parameters may also be tuned to maximize sensitivity for a given range of values of RI. We then present theoretical calculations of the sensitivity of each device for several different ranges of RI corresponding to different biological samples. Our results indicate that while the directional coupler device appears to have somewhat greater sensitivity, the surface plasmon device has the advantage of linear behavior for a given RI range of interest. However, in both cases we find that - in the case of a homogeneous sample - the proposed devices can be designed to accurately measure a refractive index change on the order of 10−5 - 10−4 refractive index units. This thesis is organized as follows. In Chapter 1, we briefly review the use of optical devices as biosensors. In Chapter 2 we develop the basic theory of propagation in a waveguide and its applications to the propagation of surface plasmons. In Chapter 3 we discuss the basic theory and allowed modes of a directional coupler and derive an expression for the coupling length of a symmetric directional coupler. In Chapter 4, we discuss the details of our directional coupler design and also present results - obtained via numerical simulations carried out using BeamProp software - for the device sensitivity for several different cases. In Chapter 5 we discuss the design of our surface plasmon device and also present theoretical expressions for the dependence of the reflectance on the sample RI. We then present results for the sensitiv (open full item for complete abstract)

Committee: Jacques Amar (Committee Chair); Robert Deck (Committee Member); Arunan Nadarajah (Committee Member); Aniruddha Ray (Committee Member); Richard Irving (Committee Member) Subjects: Optics; Physics

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Physics

We performed single-molecule studies to investigate the impact of several prominent small molecules (the oxazole telomestatin derivative L2H2-6OTD, pyridostatin, and Phen-DC 3) on intermolecular G-quadruplex (i-GQ) formation between two guanine-rich DNA strands that have 3-GGG repeats in one strand and 1-GGG repeat in the other (3+1 GGG), or 2-GGG repeats in each strand (2+2 GGG). Such structures are not only physiologically significant but have recently found use in various biotechnology applications, ranging from DNA-based wires to chemical sensors. Understanding the extent of stability imparted by small molecules on i-GQ structures has implications for these applications. The small molecules resulted in different levels of enhancement in i-GQ formation, depending on the small molecule and arrangement of GGG repeats. The largest enhancement we observed was in the 3+1 GGG arrangement, where i-GQ formation increased by an order of magnitude, in the presence of L2H2-6OTD. On the other hand, the enhancement was limited to three-fold with Pyridostatin (PDS) or less for the other small molecules in the 2+2 GGG case. By demonstrating detection of i-GQ formation at the single-molecule level, our studies illustrate the feasibility to develop more sensitive sensors that could operate with limited quantities of materials. In another study, although its mesomorphic properties have been studied for many years, only recently has the molecule of life begun to reveal the true range of its rich liquid crystalline (LC) behavior. End-to-end interactions between concentrated, ultra-short DNA duplexes – self-assembling to form longer aggregates that then organize into LC phases – and the incorporation of flexible single-stranded “gap” regions in otherwise fully-paired duplexes – leading to the first convincing evidence of an elementary lamellar (smectic-A) phase in DNA solutions – are two exciting developments that have opened new avenues for discovery. In this dissertation, w (open full item for complete abstract)

Committee: Hamza Balci (Committee Chair); Samuel Sprunt (Committee Member); Michael Tubergen (Committee Member); Sanjaya Abeysirigunawardena (Committee Member); Antal Jákli (Committee Member) Subjects: Physics

PhD, University of Cincinnati, 2021, Engineering and Applied Science: Electrical Engineering

To understand synaptic plasticity, it is vital to delve into the foundational mechanism that drives such phenomena. Fundamentally, synaptic transmission depends on the alteration of neurochemical receptors, the quantity of such neurotransmitters, postsynaptic Ca2+ release, postsynaptic neuronal responses to active secretion/reuptake, and modulation of excitatory or inhibitory behavior. It is crucial to isolate and decipher each basis above for complex behavioral analysis in an individual. Overall, an in vitro implementation was attempted here for the detection of synthetic Dopamine neurotransmitter in a purely electronic manner through AOS TFTs. This provides a base for future in vivo lab-to-patient adaptations of such a platform. For this purpose, initially, non-passivated binary ZnO TFTs were developed through a physical sputter deposition and wet etch process, and their pristine electrical behavior was analyzed. Previously designed and optimized Tobramycin ssDNA aptamers were surface tethered and anchored to ZnO channel substrates through crosslinker immobilization chemistry. Such biosensors were used to detect small-molecule Tobramycin in a low dynamic range of 1nM-100nM concentration with a saturated maximum current change of ˜0.667nA and aptamer-target dissociation constant of ˜0.534×10-9mol/liter or M as a proof-of-concept study with previously standardized Tobramycin target. The complications that were encountered with ZnO motivated the exploration of other compound material systems and immobilization chemistries. From multiple iterations and preliminary data, the quaternary compound semiconductor IGZO was selected as the channel layer. Altogether, a low-thermal budget combination of physical sputter/PLD and chemical ALD deposition was used with a wet etch process to pattern Schottky source/drain contacts over the non-passivated channel. As anticipated, in deep subthreshold electrical analysis, these short channel devices exhibited high r0 =1012Ω and A (open full item for complete abstract)

Committee: Rashmi Jha Ph.D. (Committee Chair); Vidya Chidambaran (Committee Member); Ryan White (Committee Member); Tao Li Ph.D. (Committee Member); Kevin Leedy Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2021, Materials Science and Engineering

Monitoring oxygen and glucose levels in vivo is crucial to ensuring human health, especially amidst the ongoing COVID-19 pandemic. Using blends of biodegradable polycaprolactone (PCL) and gelatin – along with an oxygen-sensitive porphyrin, Pd-MABP – implantable, biodegradable, electrospun oxygen sensors were fabricated. These sensors were first injected into horse hide and then into live horses to determine the effectiveness of oxygen monitoring system in mammalian tissue. Two different sensor experiments took place, both indicating oxygen contents behavior that did not correlate to simultaneous blood gas measurements. In vitro testing in 37°C PBS was also conducted and the data displayed linear Stern-Volmer behavior over the period of one month and that could be correlated to the induced oxygen concentrations. These electrospun oxygen sensors were also used as a basis for glucose sensors. By adding glucose oxidase (GOx) to the polymeric fibers, it was reasonable to expect that the sensors should be able to detect changes in glucose levels by the corresponding localized consumption of oxygen. GOx was incorporated through various methods including incorporation into the sensing fibers and as a post-spinning coating. These techniques showed varying degrees of success suggesting that a previously unknown interaction between the Pd-MABP and the gelatin was occurring. This mechanism was explored in some detail along with the impact of storage solution conditions.

Committee: Teresa Burns (Committee Member); Jinghua Li (Committee Member); John Lannutti (Advisor) Subjects: Materials Science

PhD, University of Cincinnati, 2020, Engineering and Applied Science: Environmental Engineering

Cyanobacteria harmful algal blooms (Cyano-HABs) are increasing in frequency and cyanotoxins have become an environmental and public concern in the U.S. and worldwide. In this dissertation, a thorough literature search was undertaken, and the state of knowledge is presented. The majority of reported studies and developments of electrochemical affinity biosensors for cyanotoxins are critically reviewed and discussed. Essential background information about electrochemical biosensors is combined with the rapidly moving development of electrochemical biosensors for these toxins. Current issues and future challenges for the development of useful electrochemical biosensors for cyanotoxin detection that meet the demands for applications in field freshwater samples are discussed. Electrochemical impedance spectroscopy (EIS), an extremely sensitive analytical technique, is a widely used signal transduction method for the electrochemical detection of target analytes in a broad range of applications. The use of nucleic acids (aptamers) for sequence-specific or molecular detection in electrochemical biosensor development has been extensive, and the field continues to grow. While nucleic-acid based sensors using EIS offer exceptional sensitivity, signal fidelity is often linked to the physical and chemical properties of the electrode-solution interface. The goal of this study is to improve our understanding of the effect of multiple factors on EIS signal response and to optimize the experimental conditions for development of sensitive and reproducible sensors. The presented data in this dissertation demonstrate a need for rigorous control experiments to ensure that the measured change in impedance is unequivocally a result of a specific interaction between the target analyte and nucleic recognition element. We demonstrate the successful development of an electrochemical aptamer-based sensor for point-of-use detection and quantification of the highly potent microcystin-LR (MC-LR (open full item for complete abstract)

Committee: Dionysios Dionysiou Ph.D. (Committee Chair); Armah de la Cruz Ph.D. (Committee Member); William Heineman Ph.D. (Committee Member); Margaret Kupferle Ph.D. (Committee Member); George Sorial Ph.D. (Committee Member); Ryan White Ph.D. (Committee Member) Subjects: Environmental Engineering

Master of Science in Biological Sciences, Youngstown State University, 2020, Department of Biological Sciences and Chemistry

Conventional hybridoma technology has been used for the selection and production of proteins for biosensor development. However, hybridoma technology is typically a slower and more costly procedure than phage display and produces a less durable end-product. Quicker and more efficient production of a small peptide using phage display has been studied at Youngstown State University for use in a blood biosensor. A heptapeptide BR-1 had been selected to bind to human serum albumin (HSA) with high specificity and was sequenced and inserted into a pMAL-c5X expression vector. In this study, biotinylation with biotin-PEG4-hydrazide and EDC chemistry, indirect enzyme-linked immunosorbent assays (ELISAs) with HSA target and biotinylated peptide (B-BR-1), and competitive inhibition peptide ELISAs with HSA target, soluble or bound Inhibition HSA, and B-BR-1 were used to confirm peptide specificity for HSA. The pMAL-c5X protein production and purification system, amylose resin affinity chromatography, 8–16% and 16.5% SDS-PAGE, and UV-Vis spectrophotometry were used to evaluate BR-1 production and purity. Binding of 2 µg B-BR-1 to 1 µg HSA target was significantly reduced by 0.01 and 0.1 µg bound Inhibition HSA (p < 0.05). Bound Inhibition HSA was found to inhibit B-BR-1 more strongly than soluble HSA. A fusion of maltose binding protein to BR-1 was produced and purified by affinity chromatography with a high yield of 2.23 mg/mL MBP/BR-1. However, evaluation of protein cleavage by SDS-PAGE and UV-Vis spectrophotometry was unable to detect soluble BR-1 peptide after cleavage. Optimization of BR-1 production and purification methods will enable future mass production of a small, durable peptide to develop a wearable blood biosensor to save the lives of military and law enforcement personnel.

Committee: Diana Fagan PhD (Advisor); Jonathan Caguiat PhD (Committee Member); David Asch PhD (Committee Member) Subjects: Biology; Chemical Engineering; Experiments; Immunology; Microbiology; Nanoscience; Nanotechnology

Master of Science, The Ohio State University, 0, Chemical Engineering

Liquid Crystal (LC), a phase between crystal solid and isotropic liquid, is a versatile material. Based on its sensitivity and visualization, it has been applied for several research fields, such as Liquid Crystal Display (LCD), thermo sensor, biosensor, so on and so forth. The long-range orientational and positional ordering gives it special properties on the functional surfaces. The first aim for our work is using bio-inspired material as a wonderful strategy to confine the lubricant under the water droplet. The second aim for our work is using sensitivity of liquid crystal to give us extreme sensitivity of DNA sequence.

Committee: Xiaoguang Wang (Advisor) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

Two research areas in the field of biomedical engineering that have progressed significantly and garnered a great deal of interest in recent years are electroporation and biosensors. Electroporation has found wide usage in microbiology and cellular manipulation. Conventional or “bulk” electroporation (BEP) is the most commonly employed electroporation technique, and while it is easy to use and able to transfect a large cell population, it suffers a variety of drawbacks such as high voltage levels (resulting in low transfection efficiency due to cellular damage) and non-uniform biasing applied to the target cell population. 2D Micro-electroporation (MEP) and its successor 2D nano-electroporation (NEP) allow for control over delivery dosage and uniform biasing of target cell populations, but at low throughput. The first portion of this Ph. D. research uses Bosch etching process, which is optimized and characterized with respect to etch rate, etching parameters, and feature size to create a 3D NEP silicon platform that conserves the best attributes of both 2D NEP and BEP. Before device fabrication, a Bosch etching process is optimized and characterized with respect to etch rate, etching parameters, and feature size. The 3D NEP device is evaluated to ensure it possesses the “hallmark” benefits of NEP such as dosage control, good transfection uniformity, and high cell viability in a high throughput system. Simulations are performed and corresponding experiments are run to determine the ideal voltage for optimizing these parameters. As a result of this research the following have been achieved, (1) a tracked-etched membrane (which suffered from randomized nano-channel locations and thus poor throughput) is no longer the only available 3D NEP-style system. (2) The design and creation of this 3D NEP device allows the user to have dosage control, high cell viability, and uniform transfection for a large cell population. (3) A high-throughput 3D NEP system is (open full item for complete abstract)

Committee: Wu Lu (Advisor); L. James Lee (Committee Member); Jiyoung Lee (Committee Member); Irina Artsimovitch (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Electrical Engineering; Engineering; Environmental Science

Master of Science (MS), Ohio University, 2020, Chemical Engineering (Engineering and Technology)

An electrochemical sensor for detecting the bacterium Escherichia coli (E. coli) in water has been developed. The sensor probe was electrochemically characterized by chronoamperometry to obtain the current responses from different concentrations of E. coli. The presence of E. coli hindered the formation of a locally formed catalyst leading to a drop in current. Current responses specific from standardized microbial concentrations were recorded and a calibration model was developed. Our electrochemical microbial sensor (EMS) can sense the presence/absence of E. coli in less 0.5 seconds, has a detection limit of 10^2 colony forming units per milliliter, and can quantify the microbial concentration within 10 minutes. This sensor was also tested successfully with real wastewater samples for E. coli detection. Thus, EMS shows potential for field applications.

Committee: Valerie Young (Advisor); Ronan Carroll (Committee Member); Howard Dewald (Committee Member); Sumit Sharma (Committee Member); Gerardine Botte (Advisor) Subjects: Biomedical Engineering; Chemical Engineering

PhD, University of Cincinnati, 2020, Arts and Sciences: Physics

Stress is often called “the silent killer” due to its hidden effects on everything from heart disease to psychological health. Therefore, having a stress-monitoring system would be beneficial for the self-management of mental and physical health of individuals within the stressful environment of today's world. In this work, we introduce an improved method for developing a robust and user-friendly point of care (POC) diagnostic device to monitor stress and depression biomarkers (cortisol and dopamine) in non-invasive biofluids (sweat, urine, saliva). Paper-based microfluidics represents a desirable substrate for low cost, easy to store/transport/use diagnostic devices that can be used to analyze bodily fluids (such as blood, sweat or urine) for a variety of conditions. The principle of capillary flow in paper-based microfluidics makes the small sample volume move by capillary action without the need for external pumps and are capable of performing multiple assays simultaneously on a single device. Most POC biomarker monitoring tests are based on immunochemical reactions using antibody recognition. The use of aptamer- functionalized gold nanoparticles as a colorimetric method of detection in strip biosensors is an attractive alternative to overcome the limitations of current methods: immunogenicity, sophisticated laboratory techniques, and time-consuming. A paper-based apata-sensor device is designed to detect the levels of stress biomarkers within 10-15 minutes by providing a red band in the test zone of the biosensor. The color intensity in the test zone of the device indicates the target concentration in the sample. The aptamer-based biosensor for the cortisol detection in sweat successfully exhibited a visual limit of detection of 1 ng/mL under optimized condition, readily covering the normal range of free cortisol in sweat (8–140 ng/mL). No significant cross-reactivity to other stress biomarkers was observed. The detection of dopamine in urine has been invest (open full item for complete abstract)

Committee: Andrew Steckl Ph.D. (Committee Chair); Hans Peter Wagner Ph.D. (Committee Chair); Leyla Esfandiari Ph.D. (Committee Member); Kay Kinoshita Ph.D. (Committee Member) Subjects: Physics

Master of Sciences, Case Western Reserve University, 2020, Chemical Engineering

Cardiovascular disease (CVD) is the leading cause of death in the United States since the mid-20th century and has many well-established biomarkers such as C-reactive protein and N terminal pro-8 type peptide. Recent studies suggest that detection of a specific enzyme, myeloperoxidase (MPO) can be used for improved risk stratification in CVD, independent of other more established biomarkers. Myeloperoxidase is an enzyme produced by leukocytes, and functions as a catalyst for the creation of reactive oxidants and radical species. The pathways utilizing MPO have been determined to be an important process in phagocytosis. However, these same pathways are identified as potentially proatherogenic biological activities at various stages of CVD development. Measurement of MPO appears to be a valuable tool in the assessment of early stages of CVD, and this study investigated the viability of an electrochemical sensor system to detect MPO. Specifically, this system used a single-use electrochemical sensor prototype, with a bio-recognition mechanism using MPO antibody. The fabrication and preparation of the sensor system explored two separate bioconjugation techniques, 2 iminothiolane (Traut's reagent) and N-succinimidyl S-acetylthioacetate (SATA), to immobilize the MPO antibody to the gold working electrode. Bioconjugation procedures for the immobilization of the MPO antibody were established, and the results of performance of these bioconjugated MPO antibody sensors were presented and discussed. Electrochemical impedance spectroscopy over a frequency range of 0.01 Hz – 10,000 Hz for a bioconjugated MPO antibody electrode was carried out to assess the surface coverage of the electrode element by the antibody. Preliminary measurements of MPO enzyme using this bioconjugated antibody-sensor appeared to be feasible, and a lower detection limit at a concentration of 0.008 µg/ml MPO was observed in this study.

Committee: Chung-Chiun Liu (Advisor); Julie Renner (Committee Member); Heidi Martin (Committee Member) Subjects: Chemical Engineering

PHD, Kent State University, 2019, College of Arts and Sciences / Department of Physics

Organic Electrochemical Transistors (OECTs) are versatile bio-sensors. However, despite their importance for the field of organic bio-electronics, an incomplete understanding of their working mechanism is currently precluding a targeted design of OECTs and it is still challenging to formulate precise design rules guiding materials development in this field. Here, an extensive experimental and theoretical study is presented to clarify the working mechanism of OECTs. It is observed that drift and diffusion of ionic species inside the channel of the transistor lead to systematic discrepancies between experiments and previous device models. A 2D simulation model is implemented to understand the origins of the shortcoming of previous device models and an improved description of the device operation is proposed. It is found that ions move inside the transistor channel to reach an equilibrium state, in which ions are accumulated at the drain contact. The accumulation of ions leads to the large potential drop, which can be described by a voltage dependent contact resistance. This 2D model is validated by a comparison of the calculation results to measured potential profiles inside the channel as well as to transfer characteristics of the OECT for different channel lengths. The voltage dependent contact resistance is extracted from the output characteristics of the OECT in the linear region using transmission line method (TLM), and shown to follow similar trends as the numeric model. It is furthermore proposed that the voltage dependent contact resistance is responsible for the often observed transconductance peak at a particular gate voltage. The stability of the device is studied using a lateral device geometry. A crosslinked ionic liquid is used instead of an aqueous electrolyte. A hysteresis in the transfer characteristic and a shift in the transfer characteristic due to a constant gate bias stress are observed. It is found that these instabilities are due to slowl (open full item for complete abstract)

Committee: Björn Lüssem (Advisor); Oleg D. Lavrentovich (Committee Chair); Jeffrey J. Wenstrup (Committee Member); Almut Schroeder (Committee Member); Hamza Balci (Committee Member) Subjects: Physics

Doctor of Philosophy, University of Toledo, 2019, Biomedical Engineering

The development of detection methods for the novel biomarkers can have a significant impact on the research and clinical applications such as drug discovery, disease diagnosis, and treatment monitoring. Histatin 3 (H3) is an antimicrobial salivary peptide that possesses the capability of being a therapeutic agent against oral candidiasis and has recently been linked to acute stress as a potential novel biomarker. Stress biomarkers reflect the physical and cognitive performance of an individual, and their monitoring in real-time is of vital importance for the high-risk jobs, including military, pilot, and surgeon, where higher vigilance is required for an extended period. The salivary levels of H3 also have been correlated with the HIV-infection and associated oral candidiasis. Therefore, monitoring H3 levels in human saliva can provide essential information about an individual's health status, including HIV-infection, oral candidiasis, and acute stress. Additionally, H3 detection could serve as therapeutic drug monitoring if H3 can be established as an alternative therapeutic agent. The currently available detection techniques for H3 are gel chromatography, high-performance liquid chromatography (HPLC), mass spectrometry (MS), and antibody-based immunoassays. The Chromatographic and mass-spectroscopic methods are laborious, utilize expensive instrumentation, require trained personnel, and time-consuming. Whereas antibody-based immunoassays are not widely validated, expensive, sensitive to temperature, and have a short lifespan. This void in analytical methods is not just for H3 but also applies to several other biomarkers in saliva. Even though saliva is considered as an optimal biofluid, several limitations are impeding its use in diagnostic and research. The major hurdles include the deficient concentration of biomarkers, need of laboratory-based preprocessing to remove mucin and interfering particulate matters, and lack of standard sample collection methods. A (open full item for complete abstract)

Committee: Cameron Brent PhD (Advisor); Giovannucci David PhD (Committee Member); Kim Dong-Shik PhD (Committee Member); Pappada Scott PhD (Committee Member); Pirnstill Casey PhD (Committee Member) Subjects: Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Chemical Engineering; Chemistry; Health Care; Health Sciences; Molecular Biology; Nanotechnology

Master of Science in Biological Sciences, Youngstown State University, 2019, Department of Biological Sciences and Chemistry

The goal of this project is to produce a carbon nanotube transistor-biosensor that can detect blood, which can be used by the police or military. This biosensor would be able to detect human serum albumin (HSA) and send a distress signal for help. HSA is the most abundant component of blood plasma, making it an ideal target for detection. The specific goal of this study is to purify an HSA-specific heptapeptide, BR-1, from a M13 filamentous phage that was obtained through phage display. The specificity of BR-1 for HSA was confirmed by performing an Enzyme-linked Immunosorbent Assay (ELISA), however, several peptide ELISAs were performed beforehand in order to find the optimal conditions for the ELISA (biotin amounts on peptide for streptavidin-biotin system and wash and blocking buffers). The BR-1 peptide was previously sequenced in this lab, and this sequence was utilized for this experiment. Primers were designed for a polymerase chain reaction process that incorporated the peptide sequence into the expression vector pMal-c5x. This DNA was then subsequently purified, ligated, and sequenced again to confirm the presence of the peptide sequence in the vector. The majority of the peptide sequence was incorporated into the vector; however, this process will need to be repeated in order to incorporate the complete sequence into the vector. After the peptide sequence is incorporated into the pMal-c5x expression vector, this vector will then be transformed into E. coli, and will be induced to express this peptide fused to a maltose-binding protein (MBP). The peptide will subsequently be purified from the MBP using an amylose resin column. After this process is complete, the specificity of this purified peptide can be tested by performing another ELISA. Future efforts will be to use the peptide that our lab purified and incorporate it into a biosensor that can detect HSA.

Committee: Diana Fagan PhD (Advisor); David Asch PhD (Committee Member); Jonathan Caguiat PhD (Committee Member) Subjects: Biology

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Electrical Engineering

Stress manifests itself in human body through various psycho social, physical, chemical formats. Its integrated effect on human health is detrimental, vital symptoms are depression, neurological disorder, cardio thoracic disease, weight loss or gain, high blood sugar. Primary elements that enable better understanding of stress are several “biomarkers” (hormones and neurotransmitters) present in body fluids. Concentrations of these biomarkers accurately predict the physical and mental state of the individual. Key biomarkers associated with stress and the focus of this research are cortisol, serotonin, dopamine, norepinephrine, epinephrine, neuropeptide Y (NPY), brain-derived neurotropic factor (BDNF). Human bio fluids are a trove of information regarding these biomarkers. Elevated levels of hormones released into the blood stream also diffuse into other body fluids such as sweat, interstitial fluid, saliva, urine. Identification and measurement of concentration of these markers provide a direct pathway for stress assessment. Overall objective of this thesis is to provide its readers with a unified platform of information which can be used to understand physiological effect of these biomarkers and give an insight into various techniques that can be used to develop a smart detection system for these markers. For this research, primary focus has been given to UV-Vis spectroscopy as the detection technique. UV spectroscopy of stress biomarkers performed in the range of 190 – 400 nm reveals presence of primary, secondary, tertiary absorption peaks at near UV wavelengths. Cortisol, lipophilic glucocorticoid hormone (MW: 362 Da) has unique absorption peak at ?max: 247 nm. UV absorption profile of serotonin (MW: 175Da) show four absorption peaks (?1: 201, ?2: 224, ?3: 278 and ?4:298 nm). Amine group of biomarkers collectively termed as Catechols - Dopamine (MW 153 Da), Norepinephrine (MW: 169 Da) and Epinephrine (MW: 183 Da) displays characteristic absorption peaks at ?1: 20 (open full item for complete abstract)

Committee: Andrew Steckl Ph.D. (Committee Chair); Je-Hyeong| Bahk Ph.D. (Committee Member); James Herman Ph.D. (Committee Member); Rashmi Jha Ph.D. (Committee Member); Richard Murdock Ph.D. (Committee Member) Subjects: Engineering