Lateral flow assay (LFA) has been demonstrated as a promising point-of-care biosensor due to its facile use and low cost. These immunoassays utilize nanoparticles as a colorimetric label to conjugate with the antibody and create a colored signal for antigen detection. Typically, gold or silver nanoparticles are used for this procedure. However, the sensitivity of these materials is not high enough to detect certain biomarkers such as the prostate specific antigen (PSA) which is a biomarker for prostate cancer. Replacing the nanoparticles with dual metal nanocages with a hollow interior has potential to improve the state of the flow test. Dual metal nanocages generated through galvanic replacement have been studied for their unique plasmonic and catalytic properties. In this study, silver-palladium nanocages were synthesized using a galvanic replacement reaction to create dual-metal, hollow nanocages. The particles were characterized for their bimetallic nature with x-ray photoelectron spectroscopy, their hollow structure with transmission electron microscopy, and their plasmonic properties with UV-Vis spectroscopy. Particles of three different sizes were created to investigate a size effect on antigen detection. The nanocages were used to as the label for immunoassay which produced a black, colored signal, and the medium and large AgPd NPs improved the tests’ naked eye limit of detection against standard 40 nm gold nanoparticles by tenfold and twenty-fivefold respectively. The medium and large AgPd NPs also had a considerable increase in calibration sensitivity when converting qualitative measurement into quantitative signal. With this work, it is our hope to improve the sensitivity of lateral flow assay and sustain the procedure as a reliable form of point-of-care testing.

<p dir="ltr">Small volume entities, such as aerosols, microdroplets, and cells, hold many truths of nature that are only recently being discovered. For example, researchers are finding that the reaction rates of certain entities are orders of magnitude larger in microdroplets than in bulk solutions, and that this effect scales with droplet size. Thus, the heterogeneity within populations of each of these environments require analysis at the single entity level. In order to probe these systems, new measurement tools must be developed. To this end, electrochemistry offers a sensitive, rapid, and affordable platform with which to make these kinds of measurements. In addition, electrochemistry can be adapted to detect a vast array of analytes, from environmental contaminants like per- and polyfluoroalkyl substances (PFAS, <i>i.e.</i> “Forever Chemicals”), to heavy metals like lead, to energetics like 2,4,6-trinitrotoluene (TNT). Aerosol sampling can be performed using a modified technique called Particle-Into-Liquid Sampling for Nanoliter Electrochemical Reactions (PILSNER). Building upon this, entire electrochemical cells can be miniaturized into a single probe (10s-100s of micrometers in diameter) for single aerosol detection, as well as single cell and microdroplet electroanalysis. Using fundamental principles and mathematical solutions, these probes can also be used to investigate temperature change and ice nucleation in microdroplets. This dissertation demonstrates the utility of electrochemistry to probe a wide range of small volume entities.</p>

QCM sensor is a response to a kind of broad spectrum, high sensitivity, and simple structure, low-cost detection device, and particularly its quality as a type of gas sensor is widely used. With the successful oscillation in liquid phase, QCM sensor has been involved in the application analytical chemistry, surface chemistry, biochemistry and environmental monitoring side and many other scientific fields. With sensitive surface film as the sensitive element, AT-cut quartz crystal as energy transducer components by changes of the relationship between mass of surface film and frequency of QCM sensor transduces signals of mass or concentration into output frequency signal of sensor, thus achieve changes of mass or concentration detection. This paper mainly states how to design a low-cost QCM system platform with Arduino microcontroller board based on QCM sensor specific properties. For the oscillator circuit selection and differential frequency circuit design, the shield board has properly matched Arduino Mega2560, then by programming code to make Arduino acquire frequency of QCM sensor in real-time. Meanwhile, the interface and data store are corresponding convenient for real- time observing and data post-processing. By the tests of anhydrous ethanol evaporation, QCM system platform was calibrated and Sauerbrey equation verification. Moreover, this paper studies that photocatalytic degradation processing of Rhodamine B (RB) and methyl orange solution at the Surface of nanocrystalline TiO2 by QCM sensor.

Detecting lung cancer is di cult as it is hidden in the body, and current clinical methods are not elective at an early stage; the one-year survival rate after diagnosis in the World is just 29-33%. Acetyl amantadine (AcAm) is recognised as an exogeneous cancer biomarker because it is the product of a metabolic process known to be significantly up-regulated in cancerous cells. After ingestion, the an-tiparkinson and antiviral drug amantadine is acetylated in the body by the enzyme spermidine/spermine N1 acetyltransferase to give AcAm, which can be detected in patient’s urine. However, techniques previously used to quantify AcAm in urine, such as liquid chromatography-mass spectrometry (LC-MS), are undesirable for clin- ical adoption due to high costs and long run times. Further costs and delays result from the requirement for solid phase extraction (SPE). Therefore, it is highly desired to lower the costs and delays in processing by exploring different quantification approaches, ideally without the need for SPE processing. In this thesis, I investigate the use of surface enhanced Raman spectroscopy (SERS) to quantify AcAm in urinalysis. I prepare two kinds of Raman substrates with hydrophobic pocket surface capture agents beta -cyclodextrin (beta -CD) that work to extract the AcAm from the urine, followed by the surface enhanced Raman measurement using two kinds of Raman systems. The detection strategy is more economical than the currently used LC-MS approach, and enables development of an easy-to-use point-of-care tool that should provide a more rapid turnaround to the health care provider. The next step will be to use real samples. If it is achieved, it will be a promising step in early cancer diagnostics. / Graduate

Chemical imaging by mass spectrometry is a powerful approach by which to map spatial distributions of molecules to better understand their function in the system of interest. Over the last thirty years, MSI has evolved into a very powerful analytical tool for the investigation of chemically-complex samples including biological tissues, catalytic surfaces and thin layer chromatography plates, among many others. The work in this dissertation aimed to characterize existing MSI methods, while also developing novel instrumentation able to overcome the challenges found in a variety of applications. Different sample preparation and ionization techniques were evaluated to maximize detection of lipid species in brain tissues subjected to traumatic injury to better understand the biological processes involved. Next, differential mobility separation was coupled to an ambient MSI system that resulted in increased signal-to-noise ratios and image contrast. Third, bulky catalytic granite surfaces were imaged to determine specific mineral reactivity and demonstrate the ability of desorption electrospray ionization to image such samples. Fourth, a novel technique was developed names Robotic Plasma Probe Ionization (RoPPI), which uses a vision system-guided robotic arm to probe irregular surfaces for three dimensional surface imaging. Finally, a software program was developed to automatically screen MSI datasets acquired from thin layer chromatography separations for spot-like shapes corresponding to mixture components; this program was named DetectTLC. This research resulted in instrumentation advances for MSI that have enabled increased chemical diversity, enhanced sensitivity and image contrast, imaging of bulky or irregularly-shaped surfaces, and multivariate tools to facilitate data interpretation.

<p> X-ray absorption spectromicroscopy combines microscopy and spectroscopy to provide rich information about the chemical organization of materials down to the nanoscale. But with richness also comes complexity: natural materials such as biological or environmental science specimens can be composed of complex spectroscopic mixtures of different materials. The challenge becomes how we could meaningfully simplify and interpret this information. Approaches such as principal component analysis and cluster analysis have been used in previous studies, but with some limitations that we will describe. This leads us to develop a new approach based on a development of non-negative matrix approximation (NNMA) analysis with both sparseness and spectra similarity regularizations. We apply this new technique to simulated spectromicroscopy datasets as well as a preliminary study of the large-scale biochemical organization of a human sperm cell. NNMA analysis is able to select major features of the sperm cell without the physically erroneous negative weightings or thicknesses in the calculated image which appeared in previous approaches.</p>

This thesis discusses the preliminary development of a microfluidic system for low concentration vapour analysis incorporating a novel analyte preconcentration method to extend vapour detection limits. The topicality of this subject is evidenced by the urgent requirement to detect vapours released by explosives or their manufacturing byproducts, allied to recent reports of gas phase detection of pathogen-related chemical markers. Commercially available, non-microfluidic, sensitive, delayed response, broadly specific, gasphase analysis methods have been developed recently. However microfluidic analysis offers the prospect of both the improved specificity of liquid phase analytical methods and increased sensitivity with fast response times. The necessary conditions to achieve a viable microfluidic vapour analysis system are discussed from collection, sampling, assay and measurement perspectives. Efficient, rapid, vapour collection into a liquid phase is predicated by large surface area to volume ratio phase-interfaces, as occur within microfluidic devices. Accordingly, research has focussed on stable, segmented gas and liquid microflows. The literature has concentrated on fixed structures and precise flow rate control to produce such segmented flow. In contrast, we have investigated pressure driven flow and small active valves in combination with precision patterned passive valves to provide deterministic control over flow and thus define gas and liquid segment sizes. This has allowed introduction of larger, precise gas volumes and hence gas/liquid ratios while still maintaining more stable flow patterns than those previously reported in the literature. Ethanol was employed as a completely soluble, volatile, ‘model’ analyte to assess collection efficiency. Research into detection focussed on a number of optical methods utilising either ‘wet’ or enzymatic chemistries. The Phase-to-Phase Extraction via a Chemical Reaction to give Lower Limits of Chemical Detection hypothesis (for the purpose of brevity this is shortened to ‘Chemical Amplification’ within this dissertation) was proposed. Thorough testing of the hypothesis using an enzyme catalysed reaction scheme has demonstrated its validity, and potential value if applied to ‘real world’ systems, particularly those for detecting low solubility analytes such as the explosive 2,4,6-trinitrotoluene (TNT) or its byproduct 2,4- dinitrotoluene (2,4-DNT).

Conducting polymers have emerged as a promising material for optoelectronics and chemical sensing application. Polyaniline (PANI) is a conductive polymer which can be easily functionalized to be specific for various biomolecules and has ideal sensor characteristics. The protonation and deprotonation of the polyaniline’s backbone by derivatization can result in color and conductive change responses. This makes it ideal for the construction of a real time, naked eye sensor. Derivatized polyaniline has previously been reported as a colorimetric sensor in solution. We plan to create a more practical sensor by synthesizing hydroxyl functionalized polyaniline thin films. In this study, we designed a process to functionalize polyaniline and deposit it as a thin film on quartz or silicon substrate via a dip coating process. To demonstrate the use of derivatized PANI in biosensing applications, derivatized and underivatized PANI thin films were treated with solutions of L-aspartic (Asp) acid at concentrations ranging from 10-8 mM to 103 mM and monitored utilizing UV-Vis spectroscopy. We found that the derivatized thin films change from deep blue to green color upon addition of Asp solution and showed a decrease in the characteristic quinoid ring peak at 600nm and the appearance of a new polaron peak at 425nm. The underivatized PANI films showed no colorimetric response indicating the hydroxyl functionalized PANI films are a more ideal material for a biosensing and naked eye detection. The polyaniline derivative was characterized using FT-IR spectroscopy, 1H NMR spectroscopy, UV-VIS spectroscopy, and Scanning Electron Microscopy. Additionally, conductivity studies were utilized to explore the material’s effectiveness as an electronic sensor using a 4-point probe to measure resistance.

Since the tragedy of the drug Thalidomide® in the late 1950 to early 1960’s, chirality has been recognized as an important aspect that must be controlled in the drug development process in the pharmaceutical industry. Since then, there has been a considerable movement towards single enantiomer drugs. This demand has presented many challenges for the synthetic organic chemist. Chiral catalysts offer one solution to this problem, as they afford the unique ability to preferentially synthesize one enantiomer. Unfortunately, the design of new chiral catalysts is often empirical, with luck and trial and error necessary due to factors that govern enantioselectivity. Therefore, it would be highly beneficial to develop a method that is capable of screening multiple chiral catalysts early in the catalyst development cycle. Using a modified ion-trap mass spectrometer, the chiral environment of various chiral catalysts may be examined, free from solvent and ion-pairing affects. Thus, the catalyst’s inherent asymmetric environment (enantioselectivity) may be probed using simple chiral molecules, including alcohols, ethers, and epoxides of various steric demands. Using these probes, various C2-symmetric bis-oxazolines and di-imines catalysts were examined. Use of the binaphthyl-based diamine, BINAM, condensed with various 3,5-disubstituted benzaldehydes, provided selectivity close to the privileged catalyst, bis-oxazoline. In general, the chiral probes 1-phenyl-2-propanol, 1-mehtoxyethylbenzene, and styrene oxide offer the best look at the catalyst’s enantioselectivity potential. With the use of the ion-trap mass spectrometer as a mass filter, the purity of the catalyst is not paramount, thus, multiple catalysts may be screened simultaneously, with the constraint that the catalysts must be of different m/z. This thesis presents results found during the exploration of various C2 and C1-symmetric chiral catalysts, in the development of the new chiral screening method utilizing various chiral probes.

Oxidative stress can result in changes to many biomolecules and also affect their activities. We are interested in protein carbonylation, a type of unnatural oxidation which has been associated with numerous degenerative disease states and is also a consequence of the natural aging process. Protein carbonyls are stable species, but countless analytical barriers exist in terms of their identification. Thus, the main goal of this work was to develop and optimize analytical methods that could be used to help us better understand which, where, and how proteins are being carbonylated. Initial studies involved method validation for carbonylating, tagging, and enriching the model protein human serum albumin (HSA). We have developed a reproducible method of producing carbonylated protein in vitro in which HSA is treated with acrolein to carbonylate cysteines, histidines, and lysines. Protein carbonyls are compatible with various affinity labels and enrichment techniques. We strived to learn more about the efficiencies of various biotin affinity labels and avidin enrichment techniques using quantitative assays and mass spectrometry. Results showed a preference for different affinity labels based on their chemical properties and suggested that monomeric columns are selective for particular peptides. Most recently, method development and validation work was done involving a cleavable biotin tag that enables both enrichment and identification of protein carbonylation modification sites. This affinity tag offered the highest labeling efficiency of all tags tested in the past and greater coverage of modification sites than biotin hydrazide reagents. We applied our analytical methods to two sets of human blood samples. The first sample set was plasma taken from chronic kidney disease (CKD) patients. No carbonylation patterns were elucidated, but this project marked the beginning of blood analyses in which existing protocols were adapted to blood samples. The second sample set was serum/plasma taken from patients with traumatic injuries. We effectively applied our analytical methods to these sample sets and were able to visualize and quantitate temporal protein carbonylation patterns via Western blotting and iTRAQ-based mass spectrometry experiments. ProteoMiner experiments proved successful in that we were able to identify a larger and more diverse amount of carbonylated proteins via mass spectrometry.