Browsing by Subject "Analytical Chemistry"
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Item Detection and Quantitation of Hazardous Chemicals in Environmental Matrices using Paper Spray Mass Spectrometry(2019-08) Dowling, Sarah Naciye; Manicke, Nicholas; Goodpaster, John; Sardar, RajeshPaper spray mass spectrometry (PS-MS) is an ambient ionization technique that has been proven useful in many types of investigative analyses. However, the use of this technique with regards to environmental samples has been largely unexplored since the technique’s development. In this work, paper spray mass spectrometry was utilized to detect and quantify compounds for environmental, forensic and chemical defense applications. Due to the sensitive nature of some projects, the work was split into two volumes. Volume 1 focuses on the detection of pharmaceuticals in soil using paper spray (Chapter 2) and the detection of chemical warfare agent (CWA) simulants and CWA hydrolysis products (Chapter 3). Volume 2 focuses on the detection and quantitation of fentanyl analogs in environmental matrices. Chapter 5 focuses on the rapid analysis of fentanyl analogs in soil matrices. The following chapter evaluates the ability of PS-MS to detect low concentrations of fentanyl analogs in water (Chapter 6). Throughout this work, paper spray has proven to be an effective, rapid alternative to chromatography for the analysis of environmental samples.Item Development of Mass Spectrometry-Based Analytical Assays for Environmental and Chemical Defense Applications(2023-12) Dowling, Sarah Naciye; Manicke, Nicholas; Goodpaster, John; Laulhé, Sébastien; Sardar, RajeshMass spectrometry (MS) is a powerful and versatile technique that is useful for addressing a wide range of complex analytical challenges. In this work, mass spectrometry-based assays were developed to address issues relating to environmental contamination and for detecting analytes of interest to the defense industry. Chapter one is an overview of the history of mass spectrometry, the fundamental operation of a mass spectrometer, as well as, advancements in chromatographic separation and ionization methods. Chapter two focuses on the development of an assay that uses blow flies as environmental sensors of chemical weapon release. In that work, a liquid chromatography – tandem mass spectrometry (LC-MS/MS) method was developed to detect chemical warfare agent simulants and chemical warfare agent hydrolysis products in flies exposed to the chemicals in controlled feeding experiments. The work in chapter three describes the development of a surface enhanced Raman spectroscopy assay coupled to paper spray mass spectrometry for a more fieldable and environmentally friendly approach to detect organophosphorus compounds. Chapter four describes the development of a paper spray mass spectrometry assay for the detection and semi-quantitation of per- and polyfluoroalkyl substances in whole blood without sample cleanup or chromatographic separations. This method would be useful in detecting high levels of these carcinogenic compounds in individuals highly exposed via their occupations. The final chapter (chapter five) returns to using blow flies as environmental sensors, but this time to detect insensitive munitions in the environment. The work focuses on the development of two different liquid chromatography mass spectrometry methods for the detection of insensitive munitions, which are less shock sensitive explosives, and their transformation products in the environment. Controlled feeding experiments were also performed where flies were exposed to contaminated soil and water sources to show the feasibility of this method in a more realistic scenario. The projects detailed herein show the extensive range with which mass spectrometry can be used for the detection of harmful chemistries of environmental concern.Item Optically Switchable Molecular Machine-Inspired Nanoplasmonic Sensing Platforms for Early Cancer Detection(2025-05) Langlais, Sarah R.; Sardar, Rajesh; Naumann, Christoph; Deng, Yongming; Goodpaster, JohnDisease diagnostics enable physicians to diagnose cancer and monitor at-risk disease associated pathology sub-populations enabling implementation of lifesaving treatment at the earliest timepoint to improve patient prognosis. However, limitations in biosensing sensitivity and specificity at the point of disease onset and during the early stages of pathogenic progression have hindered identification of biomarkers capable of early clinical diagnostics. Moreover, it has been well documented in literature that the combination of multiple biomarkers from different bimolecular classes, such nucleic acids, proteins, exosomes and exosomal cargo molecules, increases both sensitivity and specificity while mitigating false responses for early cancer diagnostics when marker concentrations and concentration changes occur at extremely low levels. However, to date, scientists have been limited in this endeavor to combining various laboratory techniques in order to pool assay results of a diverse groups of biomarkers from various bimolecular classes. For example, modern bioanalytical techniques such as drop digital or quantitative reverse transcription polymerase chain reaction (ddPCR, qRT-PCR), next generation sequencing (NGS), mass spectrometry (MS) and electrochemistry have been used to assay nucleic acids, while lateral flow assay (LFA), western blot (WB), SERS and enzyme-linked immunosorbent assay (ELISA) are routinely utilized for detection and quantification of proteins. Furthermore, exosomes and exosomal cargo molecules have been assayed using nanopores, microarrays, immunoassays and fluorescence. However, these techniques are also hindered with high occurrences of false positive responses, are extremely labor intensive, require amplification and/or fluorescent labeling, and have extensive sample processing requirements. To overcome these challenges and improve accuracy, diagnostic technology has sought to develop a single platform with multiplex functionality that is also capable of adaptive detection of multiple types of biomarkers simultaneously using a single instrument. Current literature for multiplexed and multiparametric assay capability has been limited to microRNA and Protein detection with nanopores, plasmonics, PCR or mass spectrometry and detection of exosomes and exosomal cargo molecules achieved using microfluidic devices and fluorescence. Unfortunately, there has yet to be a single platform capable for adaptively assaying microRNA, proteins, exosomes and exosomal cargo molecules simultaneously, under identical device constructs in addition to, a device capable of achieving the unprecedented sensitivity and specificity needed for early cancer diagnostics. In this dissertation, a novel localized surface plasmon resonance (LSPR)-based sensing mechanism is introduced and utilized in the development of a photo-switchable molecular machine-inspired diagnostic platform. LSPR is a highly studied nanoscale phenomenon resulting from the oscillations of free electrons on the surface of metallic noble metal nanostructures when irradiated with light. These oscillations can be collected to produce dipole spectral absorption peaks and result in strong electromagnetic near-field enhancements ideal for developing optoelectronic devices. Consequently, this property is highly dependent, and tunable, based on the size, shape and composition of the nanostructure employed. Sensing mechanisms utilizing this phenomenon are conducted by observing a change in absorbance, bulk refractive index, and local refractive index. In this dissertation, a fourth novel mechanism is identified involving the dipole-dipole coupling interactions between the free electrons on the surface of the nanostructure and a zwitterionic spiropyran/merocyanine-based surface ligand. This innovative mechanism is utilized for the fabrication of an optically switchable molecular machine-inspired nanoplasmonic sensor (OSMINS)-based diagnostic platform capable of highly sensitive and specific adaptable assays for multiparametric analysis of patient biofluids. Additionally, the multiplex functionality on the OSMINS platform is ideal for rapid, and both label and amplification-free sample processing. The work presented in this dissertation is presented in five chapters, including: (1) Introduction. (2) Methods. (3) Dipole-dipole coupling mechanism elucidation and utilization in optoelectronic device fabrication to detect microRNA and protein for bladder cancer diagnosis. In this chapter, a new LSPR-based sensing mechanism was identified and explored through the development of a novel single nanostructure-zwitterionic organic molecule coupled plasmonic ruler (PR). A dipole-dipole coupling mechanism is hypothesized and supported through theoretical calculations on dipole polarizability using an inorganic-organic heterodimer model and experimentally by determining work function and interfacial dipole values. A PR is first fabricated utilizing different Au nanostructures (triangular nanoprisms (TNPs), bipyramids (BiPs) and rods (NR)) and then when TNPs and BiPs are found to generate a superior LSPR response, further optimization of the spiropyran (SP) surface concentration via SP-spacer self-assembled monolayer (SAM) ratios is investigated. Given the synergistic relationship between LSPR-based optoelectronic device fabrication and light activated molecular machines, the new dipole-dipole coupling mechanism and PR construct is employed to fabricate an adaptable photo-switching (APS) nanoplasmonic biosensor. The singleplex-based APS biosensor is employed to detect microRNA and protein in human plasma and urine, respectively, for bladder cancer diagnosis. This regenerative and reusable APS biosensor is shown to achieve a femtomolar limit of detection (LOD) assaying 10-healthy control (HC) and 10-metastatic bladder cancer patients attaining p values ranging from 0.0002-0.0001. (4) Fabrication and optimization of an optically-switchable molecular machine-inspired nanoplasmonic sensor (OSMINS)-based diagnostic platform is achieved and utilized in performing microRNA and protein singleplexing assays for early diagnosis of pancreatic cancer (PDAC) from at-risk disease associated pathologies. In this chapter, alkylthiol linker length is optimized for SP bound to TNPs to achieve an ultrasensitive attomolar concentration LOD for detecting circulating microRNA and protein. Two-dimensional conditioned cellular media studies and orthotopically implanted PDAC cell NOD scid gamma (NSG) mouse model study is conducted to assess OSMINS diagnostic potential for early PDAC diagnosis. The OSMINS platform is then deployed to assay oncogenic microRNA and protein in 11-PDAC, 20-chronic pancreatitis (CP), 6-intraductal papillary mucinous neoplasm (IPMN), and 20-HC patients achieving p values of 0.0001 (PDAC vs. HC, IPMN vs. HC), 0.0332 (CP vs. HC) and 0.1234 (PDAC vs. CP, IPMN vs. CP). Biostatistical analysis is used to pool biomarker results, meaning microRNA + protein, to improve CP vs. HC, PDAC vs. CP and IPMN vs. CP comparison p values to 0.0001. Cross-validation of the OSMINS platform is also presented using ddPCR and electrochemiluminescence (ECL) for microRNA and protein assays, respectively, showing excellent correlation. (5) Fabrication of a multiplexed and multiparametric OSMINS-based platform with receptor structure engineered molecular machine-enabled fully customizable assays of circulating microRNA, protein, exosomes and exosomal cargo molecules for early pancreatic cancer detection and prediction of Neoadjuvant chemotherapy (NAC) treatment response. Based on the results, a predictive model is developed for early cancer detection and patient monitoring. In this work, the previously presented OSMINS technology from chapter 4 is expanded and deployed to fabricate a 96 multi-well, high-throughput device for simultaneous assays of multiple biomarkers from various biomolecular classes in a single instrument run, allowing for direct comparison of results for the first time. OSMINS development from a singleplex solid-state biosensor into a multiplexed and multiparametric diagnostic platform is reported and assessed via three-dimensional conditioned cellular media study and a PDAC specific Patient-Derived Xenograft (PDX-21) mouse model study. The multiplexed and multiparametric OSMINS platform is then used to analyze 20-PDAC, 14-low grade IPMN, 6-high grade/invasive IPMN and 20-HC patient plasma samples for direct assay of microRNA, protein and exosomes as well as isolation of exosomes and assay of exosomal lysate for protein and microRNA cargo molecules. This work achieved p values ranging from 0.0001 to 0.1234, which is discussed in detail with regard to type of assay and marker biomolecular classes designation. Validation of multiplexed and multiparametric OSMINS platform is conducted via ddPCR, ELISA, and nanoparticle tracking analysis for microRNAs, proteins and exosomes, respectively. Finally, multiplexed and multiparametric OSMINS-based platform is utilized for 15-PDAC patients before and during NAC treatments to evaluate microRNA and protein biomarkers for their effectiveness in predicting NAC treatment response. Taken together, our multifaceted detection approach utilizing a novel multiplexed and multiparametric OSMINS-based sensing platform represents a paradigm shift in accessing the full diagnostic potential of current and future identified circulating biomarkers and their biomolecular cargo for early cancer diagnosis, monitoring of at-risk associated pathogenic conditions, and as predictive markers for patient treatment response.Item Tuning optoelectronic properties of small semiconductor nanocrystals ligand chemistry through surface(2016) Lawrence, Katie Nicole; Sardar, Rajesh; Muhoberac, Barry B.; Mao, Chengde; Simpson, Garth; Long, Eric C.Semiconductor nanocrystals (SNCs) are a class of material with one dimension <100 nm, which display size, shape, and composition dependent photophysical (absorption and emission) properties. Ultrasmall SNCs are a special class of SNCs whose diameter is <3.0 nm and are strongly quantum confined leading to a high surface to volume ratio. Therefore, their electronic and photophysical properties are fundamentally dictated by their surface chemistry, and as such, even a minute variation of the surface ligation can have a colossal impact on these properties. Since the development of the hot injection-method by Bawendi et al., the synthetic methods of SNCs have evolved from high-temperature, highly toxic precursors to low-temperature, relatively benign precursors over the last 25 years. Unfortunately, optimization of their synthetic methods by appropriate surface ligation is still deficient. The deficiency lies in the incomplete or inappropriate surface passivation during the synthesis and/or post-synthetic modification procedure, which due to the high surface to volume ratio of ultrasmall SNCs, is a significant problem. Currently, direct synthetic methods produce SNCs that are either soluble in an aqueous media or soluble in organic solvents therefore limiting their applicability. In addition, use of insulating ligands hinder SNCs transport properties and thus their potential application in solid state devices. Appropriate choice of surface ligation can provide 1) solubility, 2) stability, and 3) facilitate exciton delocalization. In this dissertation, the effects of appropriate surface ligation on strongly quantum confined ultrasmall SNCs was investigated. Due to their high surface to volume ratio, we are able to highly control their optical and electronic properties through surface ligand modification. Throughout this dissertation, we utilized a variety of ligands (e.g. oleylamine, cadmium benzoate, and PEGn-thiolate) in order to change the solubility of the SNC as well as investigate their optical and electronic properties. First delocalization of the excitonic wave function 1) into the ligand monolayer using metal carboxylates and 2) beyond the ligand monolayer to provide strong inter-SNC electronic coupling using poly(ethylene) glycol (PEG)-thiolate was explored. Passivation of the Se sites of metal chalcogenide SNCs by metal carboxylates provided a two-fold outcome: (1) facilitating the delocalization of exciton wave functions into ligand monolayers (through appropriate symmetry matching and energy alignment) and (2) increasing fluorescence quantum yield (through passivation of midgap trap states). An ~240 meV red-shift in absorbance was observed upon addition of Cd(O2CPh)2, as well as a ~260 meV shift in emission with an increase in PL-QY to 73%. Through a series of control experiments, as well as full reversibility of our system, we were able to conclude that the observed bathochromic shifts were the sole consequence of delocalization, not a change in size or relaxation of the inorganic core, as previously reported. Furthermore, the outstanding increase in PL-QY was found to be a product of both passivation and delocalization effects. Next we used poly(ethylene) glycol (PEG)-thiolate ligands to passivate the SNC and provide unique solubility properties in both aqueous and organic solvents as well as utilized their highly conductive nature to explore inter-SNC electronic coupling. The electronic coupling was studied: 1) as a function of SNC size where the smallest SNC exhibited the largest coupling energy (170 meV) and 2) as a function of annealing temperature, where an exceptionally large (~400 meV) coupling energy was observed. This strong electronic coupling in self-organized films could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device applications. Strong inter-SNC electronic coupling together with high solubility, such as that provided by PEG-thiolate-coated CdSe SNCs, can increase the stability of SNCs during solution-phase electrochemical characterization. Therefore, we utilized these properties to characterize solution-state electrochemical properties and photocatalytic activity of ternary copper indium diselenide (CuInSe2) SNCs as a function of their size and surface ligand chemistry. Electrochemical characterization of our PEG-thiolate-coated SNCs showed that the thermodynamic driving force (-ΔG) for oxygen reduction, which increased with decreasing bandgap, was a major contributor to the overall photocatalytic reaction. Additionally, phenol degradation efficiency was monitored in which the smallest diameter SNC and shortest chain length of PEG provided the highest efficiency. The information provided herein could be used to produce superior SNC photocatalysts for a variety of applications including oxidation of organic contaminants, conversion of water to hydrogen gas, and decomposition of crude oil or pesticides. Therefore, we believe our work will significantly advance quantitative electrochemical characterization of SNCs and allow for the design of highly efficient, sustainable photocatalysts resulting in economic and environmental benefits.