Doctor of Philosophy (PhD)


Cain Department of Chemical Engineering

Document Type



The bioanalytical industry is projected to generate $36 billion by 2025, with the United States currently holding 80.9% of the consumers’ market. Among the bioanalytical platforms, point-of-care (POC) and point-of-use diagnosis (POU) have gained a lot of attention due to their emphasis on decentralized testing and providing low-cost solutions in resource-limited regions. While Traditional bioanalytical tools such as enzyme-linked immunosorbent assay and flow cytometry can sensitively detect biomolecules and screen single-cell response, they suffer from multiple drawbacks such as the high cost of antibodies and time-intensive procedures, which limit their ability to expand to POC/POU applications. Rapid developments in microtool technologies and nanoscience over the past decade have resulted in the integration of biocompatible rare earth (RE)-based nanoparticles (NPs) in microfluidics systems as alternatives to traditional analytical methods. Therefore, this work aims to utilize RE-doped NPs for two biomedical applications, single-cell analysis, and biosensing, that can benefit from POC/POU testing systems.

For the single-cell screening application, the use of spectrally independent RE-doped NPs as droplet trackers in a microfluidic trapping array has been described with potential POC applications in personalized medicine. The synthesized RE-doped b-NaYF4 NPs were successfully characterized for structure, morphology, spectral properties, and biocompatibility. A series of single-cell and NP co-encapsulation studies were performed in a microfluidic droplet trapping array to confirm the spectral independence of RE-doped NPs with green fluorescent protein (GFP), red fluorescent protein (RFP), and ethidium homodimer-1 (EthD-1). The droplet microfluidic system was then upgraded to a multi-input design to add the multiplex capability to the screening platform. Simultaneous generation of monodisperse droplets was achieved through the characterization of the fluid flow from each inlet. A gravity-driven flow was incorporated for droplet generation in three separate T-junctions to bypass the need for multiple syringe pumps. The relation between the droplet size and the oil-to-water flow ratio (F) was assessed in both gravity-driven flow and syringe pumps, where the droplets' size was inversely proportional to F. The fully characterized multi-input droplet microfluidic platform combined with spectrally independent RE-doped NPs has the potential to be employed in single-cell drug screening applications in POC settings.

To develop a biosensing platform suitable for POU applications, this work started with designing a RE-doped core-shell YVO4 nanoarchitecture to understand the underlying physical principles of energy transfer harnessed as a new biosensing approach. The effects of separating Bi3+ from Eu3+ ions were studied to develop nanomaterials responsive to the changes in the surface electric dipoles. Depending on the nature of the electric field, it was demonstrated that the energy levels of Bi3+/VO43- ions at the surface of the NPs could be modified to achieve dynamic optical properties. This physical phenomenon was then utilized in developing a fluorescent NP biosensor for sensitive detection of avidin. Using the specific interactions between biotinylated NP biosensor and avidin, the detection technique offered high selectivity and sensitivity without analyte labeling. The NP biosensor also exhibited good resistivity to complex biological matrix effects, and it was able to predict the avidin concentration using the generated calibration curve. It is believed that the label-free and low-cost NP biosensor can be easily functionalized with a variety of receptors for sensitive detection of small biomolecules in POU diagnosis settings.

Committee Chair

Melvin, Adam T.