Self-Assembled Magnetic-Fluorescent Nanocluster for Highly Sensitive Rotavirus Detection

Rotaviruses are well-known pathogenic agents of severe gastroenteritis responsible for acute diarrhea and vomiting, leading to dehydration and death in young children. The appropriate treatment can avoid the death of patients; however, due to late diagnosis, morbidity is still increasing. Point-of-care testing, especially lateral flow assay (LFA), has received much attention because of its rapid, simple, and inexpensive detection method [1]. Unfortunately, the present LFA kits have poor sensitivities and specificities compared to other immunoassay methods. Recently, magnetic antigen enrichment incorporating both magnetic and fluorescent nanoparticles has dramatically enhanced the sensitivity of the target antigens [2]. However, a significant challenge is the creation of a magnetic-fluorescent nanoconstruct with high magnetic responsivity, strong light emission, and structural uniformity [3].<br/>Here, we developed a facile strategy to synthesize magnetic-fluorescent CdSe-CdS/Fe₃O₄ nanoclusters (CFNCs) for highly sensitive and specific rotavirus detection. The interparticle distance between nanoclusters can be enlarged by regulating solvent polarity, allowing other nanoparticles to penetrate the nanoclusters. We coupled quantum dots to as-synthesized Fe₃O₄ nanoclusters by the above method. Massive CdSe-CdS integration allows for reducing the fluorescent quenching effect. Furthermore, we functionalized CFNCs with biocompatible poly(acrylate sodium salt) on the surface to improve water dispersity and facilitate antibody conjugation. Finally, we evaluated the CFNCs-based LFA performance by detecting the rotavirus as a target antigen, comparing the unconcentrated condition and the magnetic enrichment in fluorescence intensity and detection limit.<br/><br/>[1] G. Rosati et al., <i>ACS Nano 15</i>, 17137 (2021)<br/>[2] L. Huang et al., <i>Small 17</i>, e2100862 (2021)<br/>[3] S. K. Pahari et al., <i>Chem. Mater. 30</i>, 775 (2018)