Colorimetric Lateral Flow Assay Using Unique Hollow Nanoparticles as Labels

Test strip assay is an accessible in-home or point-of-care testing technology. At-home COVID-19 antigen tests are one example of this type of testing, which is also called colorimetric lateral flow assay (CLFA). CLFA can be used outside the laboratory, performed by a non-skilled person, and results can be read with the human eye, without the need of any equipment. Despite the simplicity of CLFA, its detection sensitivity is relatively low compared to other equipment-based diagnostic technologies. The goal of this project is to substantially improve the sensitivity of CLFA technology while retaining its simplicity through the development of a unique type of nanoparticle. This project will engage high school, undergraduate and graduate students in research. Activities include mentored research experiences for undergraduate students, research experiences for high school students through the "Highschool Summer Research Internship" program, and the implementation of a new course "Chemical Synthesis of Biomaterials." Colorimetric lateral flow assay (CLFA) is one of a handful of diagnostic techniques that can be used outside the laboratory without requiring skilled personnel and equipment. The current bottleneck for CLFA development is its relatively low detection sensitivity due to the weak color signals from colorimetric labels. For decades, gold nanoparticles (AuNPs) have been extensively used as colorimetric labels for CLFA because of their good physicochemical properties, including the display of a characteristic red color due to their plasmonic activities. Nevertheless, it remains a challenge to substantially enhance the intensity of the red color and thus the detection sensitivity of AuNPs-based CLFAs. This project aims to break through the detection limit barrier of CLFA by developing Au/Ag (gold/silver) alloyed hollow nanoparticles (Au/Ag HNPs) that can be used as alternatives to AuNPs. Compared to conventional AuNPs, the Au/Ag HNPs possess much stronger plasmonic activities. In addition, they have lower densities because of the hollow interiors, which facilitates smooth migration of particles in CLFA test strip. These distinct features of Au/Ag HNPs enable them to be sensitive labels for CLFA that can significantly advance the power of the assay without compromising its simplicity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.