In this dissertation, three types of paper-based analytical devices for point-of-care biosensing, a potentiometric method for analyzing percent hemoglobin A1c (%HbA1c) and a PDMS-glass microelectrochemical device for highly reproducible amperometric measurement in microdroplet, are described. The first paper-based sensing device is fabricated using the principles of origami (paper folding). The three-dimensional origami paper analytical device (oPAD) is fabricated on a single sheet of flat paper in a single photolithographic step and assembled by simply folding the paper by hand. Following analysis, the device can be unfolded to reveal each layer for optical and fluorescent read-out. The second type of paper-based device has an integral aluminum/air battery as the power source and reports its output using Prussian blue as an electrochromic indicator. The integrated aluminum/air battery powers both the electrochemical sensor and the electrochromic read-out. The applicability of the device to point-of-care sensing is demonstrated by qualitative detection of glucose and H2O2 in artificial urine. The third type of paper-based device (oPAD 2) uses an aptamer to recognize the analyte, adenosine, a glucose oxidase tag to modify the relative concentrations of an electroactive redox couple, and a digital multimeter to transduce the result of the assay. Adenosine is quantitatively determined using this device with a detection limit of 11.8 uM. The method for measuring HbA1c concentration, hemoglobin concentration, and thus %HbA1c in human blood is based on potentiometry. We use Alizarin red s (ARS) as a redox indicator. The potential shift of ARS owing to diol-boronic acid complexation is used to determine the HbA1c, which is a competitor of ARS for the complexation reaction. The concentration of Hb is determined by reacting it with Fe(CN)₆³⁻ and measuring the potential shift arising from the reduction of Fe(CN)₆³⁻ by Hb. The results obtained for %HBA1c in human blood are in good agreement with those determined using a reference method. The method for highly reproducible chronoamperometric analysis of the contents of microdroplets is developed. Aqueous microdroplets (~ 1 nL) and separated by a fluorocarbon solvent are generated within a microfluidic device using a T-shaped junction. Highly reproducible quasi-steady-state currents (relative standard deviations = ~ 2%) are observed when the microdroplets are stretched by a factor of 10 in a narrowed segment of a microchannel, which leads to desirable intradroplet mass transfer characteristics. Importantly, the design of the microelectrochemical device ensures direct contact between intradroplet redox molecules and the electrode surface to study inner-sphere electrocatalytic processes such as the oxygen reduction reaction. Finite-element simulations are presented that are in accord with the experimental findings. / text

archives@tulane.edu / This dissertation is rooted in clinical pathology research, and the main character is addressing limitations in current pathology evaluation workflows. Diagnostic procedures for cancer are typically conducted via core needle biopsy procedures; however, tissue sampling limitations often result in a low yield of samples containing cancer – there are no reliable intraoperative methods to determine if the “lesion is in the needle”. If biopsy procedures result in a diagnosis of cancer, surgical removal of the tumor is often the frontline curative therapy for many cancers. Importantly, histologic evaluation following the whole resected organ is necessary to determine the presence of residual cancer, yet current methods do not allow efficient determination of tumor removal completeness intraoperatively. To address limitations of current histopathology methods, what is critically needed is a point-of-procedure fresh tissue evaluation system that facilitates 1) rapid on-site imaging and evaluation, 2) less destruction, and 3) more complete assessment of tumor content in fresh specimens. A novel microscopy system using video-rate structured illumination (VR-SIM), has been developed with the intent of rapid, point-of-procedure histological screening of intact biopsy and whole surgical specimens. VR-SIM leverages widefield imaging, rapid acting fluorescent stains, and optical sectioning to provide high contrast digital images of tissue with histological relevance. The method is to replicate the standard approach as closely as possible, but replace the physical section with an optically sectioned digital image. The overall goal of this work is to perform technological and methodological refinements necessary to translate VR-SIM as a clinical tool for histologic evaluation of fresh tissue in diagnostic procedures, biobanking, and tumor margin assessment. This project will lay the groundwork for quantitative evaluation of VR-SIM as a clinical tool – with the goal of leading toward industrial design of a VR-SIM as a medical device for hospital use. Developing a new framework for integration of high throughput microscopy into the clinical and research workflow, as well as developing new methods for quantification and evaluation of clinical effectiveness these tools will be presented and discussed in the context of patient outcomes and economic impact. / 1 / David Tulman

Chlamydia trachomatis accounts for 3.6% of blindness worldwide, and is the leading cause of bacterial-induced blindness in the world. With the subtle initial presentation of the disease and the difficulty in clearing the infection without the aid of antibiotics, C. trachomatis can spread rapidly following introduction into a population. This problem is further compounded in resource limited areas due to the lack of trained personnel (i.e. Medical Doctors, Nurses), equipment, and finances to test and treat large portions of the population. A testing method that is both cheap and easy to interpret is necessary. Lateral flow assays (LFA) have been used for years to evaluate pregnancy status in the developed world, and their low cost, ease of use and disposable nature make them a worthwhile candidate, but the current use of visual reporters (i.e. gold or latex nanoparticles) does not allow for adequate sensitivity for true clinical use. Fluorescent reporters, particularly fluorescent nanoparticles, would lower the limit of detection (LOD) and allow for the detection of acute and subclinical infections, which would allow for an effective and objective screening method for trachoma and many other diseases. An effective, rapid, and disposable test would allow for mass screening to be implemented which, in turn, would allow for rapid and targeted treatment. The results in this study show that the use of fluorescent-based reporters greatly improve the LOD of the LFA, with both FITC and RuSNP reporters showing a reduction in the LOD by 1 and 2.5 logs respectively when compared to traditional colorimetric reporters. This substantial improvement in the LOD of the LFA allows for the tests to be used to detect relevant levels of viral pathogens. A similar improvement in the LOD was seen when using FITC-labeled antibodies which improved the sensitivity of LFAs with regards to the detection of C. trachomatis. The use of fluorescent-based reporters in LFAs greatly improves the LOD for both viruses and bacteria, allowing for their detection at clinically relevant levels.

This dissertation discusses the development of inexpensive, easy-to-use, and field-deployable diagnostic techniques and devices for the early detection of various pathogens, commonly found in clinical samples and contaminated food and water. Infectious diseases account for about 90% of world health problems, killing approximately 14 million people annually, the majority of which reside in developing countries. In 2012, the World Health Organization (WHO) published data on the top 10 causes of death across the globe. Although communicable disease is a prevalent cause of fatality, both low-income and high-income countries, pathogen species and transmission are very different. Nearly 60% of deaths in developing countries are caused by food, water, air or blood-borne pathogens. The most prevalent illnesses are diarrheal disease, malaria, and HIV/AIDS. By contrast, the leading causes of death in developed countries (heart disease, cancer, and stroke) are not communicable and are often preventable. However, there is an increasing need for the development of rapid and accurate methods for pathogen identification in clinical samples, due to the growing prevalence of antibiotic-resistant strains. Incorrect, or unneeded antibiotic therapies result in the evolution of extremely aggressive nosocomial (hospital-acquired) infections, such as methicillin- (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA). The implementation of rapid, easy to use and cost-effective diagnostics will reduce the frequency of pathogen-related deaths in underdeveloped countries, and improve targeted antibiotic treatment in hospital settings, thus decreasing the potential development of more treatment-resistant "super bugs". This research includes novel techniques utilizing two major sensing modalities: serological (i.e. immunological), and nucleic acid amplification testing (NAATs). We first developed a highly sensitive (limit-of-detection = 100 CFU mL-1) particle immunoassay that takes advantage of elastic and inelastic light scatter phenomena, for optical detection of target antigens. This assay is performed upon a unique nanofibrous substrate that promotes multiplexing on a user-friendly platform. We then developed a novel technique, termed emulsion loop-mediated isothermal amplification (eLAMP), in which the target amplicon is detected in real-time, again utilizing light scattering detection and quantification. Both techniques require no sample pre-treatments, and can be combined with smartphone imaging for detection of targets in under 15 minutes. These methods have the potential to improve the speed and sensitivity of early pathogenic identification, thus leading to a reduction in preventative deaths and a decrease in global economic costs associated with infectious disease in clinical and other settings.

The clinical evaluation of people with possible myocardial infarction (MI) is often limited by atypical symptoms and inconclusive initial electrocardiograms. A recent consensus from the American College of Cardiology has redefined acute MI to include cardiac markers as central to diagnosis. To address this clinical need, a sensitive microfluidic surface-enhanced Raman spectroscopy (SERS) nanochannel-based optical device is being developed for ultimate use as a point-of-care device for the simultaneous measurement of MI blood biomarkers. The device can provide enhancements of the Raman signal of the analyte measured of up to 1013 using a mechanical aggregation technique at the interface of nanofluidic structures enabling repeatable SERS measurements. Specifically in this research iterations of a sensitive, low volume SERS platform technology were designed that provided quantitative information across a specific range. With the SERS platforms studied, not only were SERS enhancements of up to 1013 achieved but also imprecision values of less than 10% across the 10-50 pM range using a ratiometric approach and qualitative detection down to 100 aM was achieved. Beyond assessment of SERS substrates, assay designs were investigated and characterized including, label-free techniques and competitive immunoassay formats. Lastly, detecting the SERS signal of multiplexed reporter molecules was investigated. By identifying the analyte and assay constraints the design and optimization of future assays will be aided using this SERS platform technology.

Developing non-invasive and accurate diagnostics that are easily manufactured, robust and reusable will provide monitoring of high-risk individuals in any clinical or point-of-care environment, particularly in the developing world. There is currently no rapid, low-cost and generic sensor fabrication technique capable of producing narrow-band, uniform, reversible colorimetric readouts with a high-tuneability range. This thesis aims to present a theoretical and experimental basis for the rapid fabrication, optimisation and testing of holographic sensors for the quantification of pH, organic solvents, metal cations, and glucose in solutions. The sensing mechanism was computationally modelled to optimise its optical characteristics and predict the readouts. A single pulse of a laser (6 ns, 532 nm, 350 mJ) in holographic “Denisyuk” reflection mode allowed rapid production of sensors through silver-halide chemistry, in situ particle size reduction and photopolymerisation. The fabricated sensors consisted of off-axis Bragg diffraction gratings of ordered silver nanoparticles and localised refractive index changes in poly(2-hydroxyethyl methacrylate) and polyacrylamide films. The sensors exhibited reversible Bragg peak shifts, and diffracted the spectrum of narrow-band light over the wavelength range λpeak ≈ 500-1100 nm. The application of the holographic sensors was demonstrated by sensing pH in artificial urine over the physiological range (4.5-9.0), with a sensitivity of 48 nm/pH unit between pH 5.0 and 6.0. For sensing metal cations, a porphyrin derivative was synthesised to act as the crosslinker, the light absorbing material, the component of a diffraction grating, as well as the cation chelating agent. The sensor allowed reversible quantification of Cu2+ and Fe2+ ions (50 mM - 1 M) with a response time within 50 s. Clinical trials of a glucose sensor in the urine samples of diabetic patients demonstrated that the glucose sensor has an improved performance compared to a commercial high-throughput urinalysis device. The experimental sensitivity of the glucose sensor exhibited a limit of detection of 90 µM, and permitted diagnosis of glucosuria up to 350 mM. The sensor response was achieved within 5 min and the sensor could be reused about 400 times without compromising its accuracy. Holographic sensors were also tested in flake form, and integrated with paper-iron oxide composites, dyed filter and chromatography papers, and nitrocellulose-based test strips. Finally, a generic smartphone application was developed and tested to quantify colorimetric tests for both Android and iOS operating systems. The developed sensing platform and the smartphone application have implications for the development of low-cost, reusable and equipment-free point-of-care diagnostic devices.

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Yes / Rapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.

Bioelectronics effectively bridges the gap between the biochemical and the electrical domains, integrating aspects of biology, electronics, physics, and material science to foster innovative solutions and impact the trajectory of human health and environmental science, by translating biological responses into electrical signals for advanced analysis. Despite its transformative potential, current bioelectronic systems face limitations in terms of scalability, sensitivity, and ease of integration. This thesis claims that co-designing Complementary Metal-Oxide-Semiconductor (CMOS) integrated circuits with highly specific and sensitive genetically engineered biosensors is pivotal in bioelectronics evolution, offering high accuracy, reliability, miniaturization, and multiplexed sensing capabilities essential for addressing challenges in healthcare, environmental monitoring, sustainable manufacturing, and beyond. To support this claim, this dissertation highlights two key contributions: a low-power ingestible sensor for gastrointestinal tract monitoring and a hybrid platform technology combining droplet microfluidics and CMOS electronics for impedance spectroscopy and luminescence sensing for rapid screening and optimization of biosensors under different environmental conditions. The first contribution details an ingestible capsule that could transform healthcare diagnostics through a novel threshold-crossing-based detector and CMOS-integrated photodiodes. This innovation exemplifies how hybrid bioelectronic systems can significantly improve the precision and non-invasiveness of real-time health monitoring. Moving beyond the traditional scope of bioelectronics and the sole purpose of health monitoring, the second contribution extends its application by integrating droplet microfluidics with CMOS chips, facilitating high-throughput droplet screening to optimize biosensor performance for application deployment. To achieve this goal, this platform is equipped with a low-noise, high-resolution CMOS impedance spectroscopy chip and a high-resolution CMOS luminescence detector chip. In highlighting these contributions, the thesis reinforces the assertion that hybrid bioelectronic systems are key to addressing a wide range of societal challenges. Moreover, the integration of synthetic biology and microfluidics with CMOS technology, as demonstrated in this work, not only overcomes existing barriers, such as achieving miniaturization, high sensitivity, rapid data processing, and energy efficiency, but also paves the way for future innovations with extensive potential in personalized medicine and environmental sustainability. / 2026-01-17T00:00:00Z

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