Organic Light-Emitting Diode Based Fluorescence-Linked Immunosorbent Assay for SARS-CoV-2 Antibody Detection

Abstract

Immunodiagnostics have been widely used in the detection of disease biomarkers. The conventional immunological tests in central laboratories require expensive equipment and, for non-specialists, the tests are technically demanding and time-consuming, which has prevented their use by the public. Thus, point-of-care tests (POCT), such as lateral flow immunoassays, are being, or have been, developed as more convenient and low-cost methods for immunodiagnostics. However, the sensitivity of such tests is often a concern. Here, a fluorescence-linked immunosorbent assay (FLISA) using organic light-emitting diodes (OLEDs) as excitation light sources was investigated as a way forward for the development of compact and sensitive POCTs. Phycoerythrin (PE) was selected as the fluorescent dye, and OLEDs were designed with different emission spectra. The leakage light of different OLEDs for exciting PE was then investigated to reduce the background noise and improve the sensitivity of the system. Finally, as proof-of-principle that OLED-based technology can be successfully further developed for POCT, antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in human serum was detected by OLED-FLISA.

Keywords: FLISA; OLED; organic semiconductor; point-of-care testing; sensing.

Figure 1

Phycoerythrin (PE) spectra and OLED information. (a) Photoluminescence excitation (PLE) and photoluminescence (PL) spectra of PE. (b) Device structures of OLEDs based on Ir(ppy)₂(acac), TBPe, and DABNA-2 emitters. (c) Electroluminescence (EL) spectra of Ir−OLED, TBPe−OLED and DABNA−OLED. (d) J−V−L characteristics of Ir−OLED, TBPe−OLED and DABNA−OLED.

Figure 2

Fluorescence sensing setup. (a) Schematic diagram of the main components of the fluorescence sensing system. (b) Leakage light response of different OLEDs measured by the fluorescence sensing system in pulsed operation.

Figure 3

Demonstration of FLISA for sensing antibodies to SARS-CoV-2. (a) Schematic diagram of FLISA for sensing antibodies to SARS-CoV-2. (b) Photos of PE fluorescence in a fluorescence microscope. The human serum was diluted in 1:80 and 1:160. Comparisons were made between control and patient groups or non-expressed SARS-CoV-N (- −COVID N) and SARS-CoV-N (+COVID N) groups.

Figure 4

Results of OLED−FLISA (DABNA−OLED) for sensing antibodies to SARS-CoV-2. Each sample was measured three times. (a) Fluorescence intensity of samples tested with 1:80 dilution of human serum under the DABNA−OLED excitation. (b) SNR of samples tested with 1:80 dilution of human serum under the DABNA−OLED excitation. (c) Fluorescence intensity of samples tested with 1:160 dilution of human serum under the DABNA−OLED excitation. (d) SNR of samples tested with 1:160 dilution of human serum under the DABNA−OLED excitation. The error in the fluorescence intensity is shown in (b,d), but is hard to see because it is small compared to the overall fluorescence intensity.