Author ORCID Identifier

Document Type


Date of Award


Degree Name

Master of Science (MS)



First Advisor

Steven Wu


Biomarkers serve a key role in illness diagnosis and treatment. Importantly, early detection can boost the therapy success rate greatly. However, traditional approaches to detect biomarkers based on fluorescence intensity changes of individual fluorophores did not completely realize the potential due to several technical problems such as low sensitivity. Ratiometric fluorescent methods use changes in the intensity of two or more emission bands (caused by the analyte) to create an internal reference that improves detection sensitivity. Due to their unique photophysical properties, such as high fluorescence intensity, high quantum yield, and low toxicity, semiconductor quantum dots (Pdots) are an ideal nanomaterial probe for ratiometric fluorescent methods. In this work, we utilized the nanoprecipitation technique to produce two different ratiometric fluorescent probes, Pdots-Pt and Pdots-Eu, for lactate and temperature detection, respectively. At the beginning, the feasibility of these two probes using in ratiometric fluorescent methods was investigated, and the reaction conditions were tweaked to get the best signal-to-noise ratio. After that, both systems' analytical performances were evaluated. The lactate sensing system had a high selectivity and a wide sensitivity range of 0.5 nM to 5.0 μM and 5.0 μM to 50 μM, with a LOD of 0.18 nM. In the physiological temperature range (25-50 °C), the temperature sensing system has an excellent linear response. The Pdots-Pt were applied to a complex biological material for the subsequent application and showed a good recovery rate. The Pdots-Eu were evaluated in vitro and showed good biocompatibility, as well as great bioimaging and sensing abilities. Overall, Pdot-based ratiometric probes can be successfully used to detect lactate and temperature in medical applications.

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University of South Dakota

Available for download on Wednesday, September 25, 2024

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