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Functional Nanosurfaces for Environmental and Toxicological Monitoring in Complex Matrices: Studies with SERS, FRET and MALDI-MS

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Recent advances in carbon- and metallic-based nanosurafces have shown that the unique optical, electrical, and physico-chemical properties of these materials make them exciting platforms for environmental and toxicological monitoring. These surfaces provide additional observational angles and novel experimental tools, further increasing the number of analyte molecules to be monitored under specific and complex sampling conditions. The scope of this dissertation is on nanosubstrate based developments for measurement of a variety of environmentally significant, complex samples with much attention given to high sensitivity and detection throughput.

Chapter One provides a quick review on theories, analytical methods, and nanotechnologies used within this dissertation. Three areas are covered: i) SERS-based trace detection of analytes in aqueous environmental samples, ii) nanotechnology-based delivery of anti-tumor agents to monitor cytotoxic effects on cancer cells, and iii) a MALDI-based omics approach to study aquatic toxicity of herbicides in a high throughput fashion.

Chapter Two describes the development of an environmental sensing technique using Surface Enhanced Raman Spectroscopy (SERS) on substrate fabricated with nanographene oxide and silver nanoprisms. This dual-enhancing silver-nanoprism-SERS and Graphene Enhanced Raman Spectroscopy (GERS) substrate was further modified into a throughput sensing method using graphene oxide assisted lithography (GOAL). Atomic force microscopy (AFM) in combination with a Raman probe (Rhodamine-6G) was used to characterize individual enhancements. The nanoprism-rGO array showed an impressive picomolar limit of detection for model compound, and offered multiplexed and trace detection of legacy aromatic pollutants.

Chapter Three describes the synthesis and characterization of a biocompatible nanographene oxide vehicle for delivery of antitumor agents into cancer cells, protein tracing to monitor chemical exposure, and biosensing on activation of apoptosis. The study on camptothecin showed that the GO-nanocarrier could be assimilated with HeLa cells. Its biocompatibility under apoptotic stress conditions was conserved, demonstrating a temporal drug releasing characteristic in physiological solutions. The protein calpain was targeted for its role in Ca2+ mediated activation, a key component in the activation of chemical induced apoptosis, which was monitored by fluorescence using a calpain sensitive nanocarrier-fluorogenic construct and three apoptosis activators.

Chapter Four describes a novel gold nanofilm array for omics-based assessment of toxicity in a unicellular aquatic species for ecotoxicological characterization of herbicide pollution. The coupling of fluorescence localization and MALDI-MS for untargeted lipidomic analysis in whole cells was accomplished using the nanosurface’s ability to enhance both fluorescence and MS/MS signals. A lipid library consisting of nearly 40 lipid peaks were identified for the test species chlamydomonas reinhardtii. A comprehensive chemometric approach based on fold-change, p-values, and PLS-DA was used to identify significant changes in abundance of TAG, DGDG, DGTS, and MGDG lipids.

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