Development of new coronavirus detection method using fluorescence enhancement by quantum dot-gold nanoparticle complex interaction

Nanomaterial-based immunoassay has been emerging and focused on a huge interest due to the intrinsic properties and its utilization in transducing and amplifying the signal for determining the presence of the target analytes. Localized surface plasmon resonance (LSPR)-enhanced fluorescent detection in immunoassay has been developed using gold nanoparticles (AuNPs) with various shapes and sizes s as the detection probe pair. In this work, a new approach is developed to enhance the LSPR effect to the fluorescent of the quantum dots (QDs) by deposition of islands of AuNPs on the core AuNPs, forming AuNPs@AuNPs. The prepared AuNPs@AuNPs and QDs were conjugated to antibodies specific to SARS-CoV-2 spike protein (S protein). The detection was simply initiated by mixing both nanomaterials to the S protein as analyte. After incubation, the fluorescent was measured and the fluorescent peak of the QDs was used as the signal for quantifying the concentration of the S protein in the sample. The detection limit (LOD) was estimated around 6.69 fg/mL in buffer and 12.5 fg/mL in spike sample. In addition, the AuNPs@AuNPs-based immunoassay showed better signal enhancement compared to only AuNPs-based immunoassay. Further study will be conducted to show the stability of the detection.