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Chemistry & Chemical Biology Department Theses and Dissertations
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Browsing Chemistry & Chemical Biology Department Theses and Dissertations by Author "Agarwal, Mangilal"
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Item Chemometric Analysis of Volatile Organic Compound Biomarkers of Disease and Development of Solid Phase Microextraction Fibers to Evaluate Gas Sensing Layers(2022-08) Woollam, Mark David; Agarwal, Mangilal; Deiss, Frédérique; Goodpaster, John; Naumann, ChristophCanines can detect different diseases simply by smelling different biological sample types, including urine, breath and sweat. This has led researchers to try and discovery unique volatile organic compound (VOC) biomarkers. The power of VOC biomarkers lies in the fact that one day they may be able to be utilized for noninvasive, rapid and accurate diagnostics at a point of care using miniaturized biosensors. However, the identity of the specific VOC biomarkers must be demonstrated before designing and fabricating sensing systems. Through an extensive series of experiments, VOCs in urine are profiled by solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) to identify biomarkers for breast cancer using murine models. The results from these experiments indicated that unique classes of urinary VOCs, primarily terpene/terpenoids and carbonyls, are potential biomarkers of breast cancer. Through implementing chemometric approaches, unique panels of VOCs were identified for breast cancer detection, identifying tumor location, determining the efficacy of dopaminergic antitumor treatments, and tracking cancer progression. Other diseases, including COVID-19 and hypoglycemia (low blood sugar) were also probed to identify volatile biomarkers present in breath samples. VOC biomarker identification is an important step toward developing portable gas sensors, but another hurdle that exists is that current sensors lack selectivity toward specific VOCs of interest. Furthermore, testing sensors for sensitivity and selectivity is an extensive process as VOCs must be tested individually because the sensors do not have modes of chromatographic separation or compound identification. Another set of experiments is presented to demonstrate that SPME fibers can be coated with materials, used to extract standard solutions of VOCs, and analyzed by GC-MS to determine the performance of various gas sensing layers. In the first of these experiments, polyetherimide (PEI) was coated onto a SPME fiber and compared to commercial polyacrylate (PAA) fibers. The second experiment tuned the extraction efficiency of polyvinylidene fluoride (PVDF) - carbon black (CB) composites and showed that they had higher sensitivity for urinary VOC extraction relative to a polydimethylsiloxane (PDMS) SPME fiber. These results demonstrate SPME GC-MS can rapidly characterize and tune the VOC adsorption capabilities of gas sensing layers.Item Nanoplasmonic efficacy of gold triangular nanoprisms in measurement science: applications ranging from biomedical to forensic sciences(2019-12) Liyanage, Thakshila; Sardar, Rajesh; Goodpaster, John; Naumann, Christoph; Agarwal, MangilalNoble metal nanostructures display collective oscillation of the surface conduction electrons upon light irradiation as a form of localized surface plasmon resonance (LSPR) properties. Size, shape, and refractive index of the surrounding environment are the key features that control the LSPR properties. Surface passivating ligands on to the nanostructure can modify the charge density of nanostructures. Further, allow resonant wavelengths to match that of the incident light. This unique phenomenon called the “plasmoelectric effect.” According to the Drude model, red and blue shifts of LSPR peak of nanostructures are observed in the event of reducing and increasing charge density, respectively. However, herein, we report unusual LSPR properties of gold triangular nanoprisms (Au TNPs) upon functionalization with para-substituted thiophenols (X-Ph-SH, X = -NH2, -OCH3, -CH3, -H, -Cl, -CF3, and -NO2). Accordingly, we hypothesized that an appropriate energy level alignment between the Au Fermi energy and the HOMO or LUMO of ligands allows the delocalization of surface plasmon excitation at the hybrid inorganic-organic interface. Thus, provides a thermodynamically driven plasmoelectric effect. We further validated our hypothesis by calculating the HOMO and LUMO levels and work function changes of Au TNPs upon functionalization with para-substituted thiol. This reported unique finding then utilized to design ultrasensitive plasmonic substrate for biosensing of cancer microRNA in bladder cancer and cardiovascular diseases. In the discovery of early bladder cancer diagnosis platform, for the first time, we have been utilized to analyze the tumor suppressor microRNA for a more accurate diagnosis of BC. Additionally, we have been advancing our sensing platform to mitigate the false positive and negative responses of the sensing platform using surface-enhanced fluorescence technique. This noninvasive, highly sensitive, highly specific, also does not have false positives techniques that provide the strong key to detect cancer at a very early stage, hence increase the cancer survival rate. Moreover, the electromagnetic field enhancement of Surface-Enhanced Raman Scattering (SERS) and other related surface-enhanced spectroscopic processes resulted from the LSPR property. This dissertation describes the design and development of entirely new SERS nanosensors using a flexible SERS substrate based on the unique LSPR property of Au TNPs. The developed sensor shows an excellent SERS activity (enhancement factor = ~6.0 x 106) and limit of detection (as low as 56 parts-per-quadrillions) with high selectivity by chemometric analyses among three commonly used explosives (TNT, RDX, and PETN). Further, we achieved the programmable self-assembly of Au TNPs using molecular tailoring to form a 3D supper lattice array based on the substrate effect. Here we achieved the highest reported sensitivity for potent drug analysis, including opioids and synthetic cannabinoids from human plasma obtained from the emergency room. This exquisite sensitivity is mainly due to the two reasons, including molecular resonance of the adsorbate molecules and the plasmonic coupling among the nanoparticles. Altogether we are highly optimistic that our research will not only increase the patient survival rate through early detection of cancer but also help to battle the “war against drugs” that together are expected to enhance the quality of human life.