Date of Award

5-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Committee Chair/Advisor

Jeffrey N. Anker

Committee Member

Stephen Creager

Committee Member

Zhi Gao

Committee Member

Jason McNeill

Abstract

A novel method uses buoyant microbubbles and magnetic microspheres to label, separate, and detect SARS-CoV-2 N-protein in patient saliva at the best reported limit of detection to date. The equipment needed is remarkably simple and inexpensive: a flashlight, digital camera, magnet, and cuvette holder, which facilitates point-of-care deployment. In our method, saliva is mixed with lysis buffer, antibody-functionalized ∼15 µm buoyant gas-filled silica microbubbles, and 2.7 µm antibody-functionalized polystyrene magnetic microspheres, forming buoyant-analyte-magnetic (BAM) complexes. A magnet pulls the BAM complexes to the bottom of the cuvette while unbound microbubbles float upwards. Removing the magnet releases the buoyant BAM complexes, which appear as bright rising dots under flashlight illumination. A camera counts the BAM complexes, with an analytical detection limit of ∼37 SARS-CoV-2 N-protein molecules in 5 µL of saliva. The assay provided positive results for all tested PCR-positive saliva specimens, with concentrations ranging from 0.7 to 2.5×105 RNA copies/µL.

Building upon this ultra-sensitive foundation, we developed the BAM Point-of-Care (POC) system to resolve the fundamental conflict between speed, sensitivity, and deployability in conventional high-sensitivity diagnostics. By integrating multiple innovative methods, we reduced the total detection time from an initial 55 minutes to 3.5 minutes. This represents a significant speedup compared to existing laboratory methods. This speedup is achieved through enhanced buoyancy and a simplified protocol. A novel syringe separation step increases the microbubble diameter to 26.85 µm with 8-fold faster rising speed. This reduces the signal release time to 8 seconds. Simultaneously, a 15-second manual tube squeeze replaces the complex incubation process. Then a semi-automated quantification to processing the video is provided by MATLAB. The stability of the POC shows high consistency across calibration curves, demonstrating that the system can be transferred to use after minimal training.

Author ORCID Identifier

0009-0005-7450-3561

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