A more efficient way to test SARS-CoV-2 virus was recently developed by a research team led by Prof. WANG Junfeng from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences. The novel nano-immune magnetic bead (Mal-IMB) they developed can be efficiently bound to SARS-CoV-2 pseudovirus in the study of protein biomimetic mineralization and synthesized into magnetic nanoparticles.

The results were published in Analytical Chemistry.

The novel coronavirus pneumonia caused by the highly contagious SARS-CoV-2 virus has had a significant impact on public health. A convenient and rapid method for virus separation is needed. IMBs, which use magnetic microspheres with specific probes to bind targets, have shown significant advantages. However, the use of IMBs in biological separations presents challenges that need to be overcome, such as low target substance concentration and complex biological environments. Small-sized magnetic beads that can penetrate contaminants and reduce non-specific binding have been proposed.

In this study, based on previous work on biomimetic mineralization synthesis, the research team modified the surface of ultra-small cluster magnetic nanobeads and combined them with ultra-small single-chain antibody fragments (RBD-scFv) targeting the RBD region of the S protein. In this way, they successfully obtained highly efficient ultra-small immune magnetic beads for identifying RBD antigens and attached them to SARS-CoV-2 pseudovirus.

"This innovative bead is designed to address the challenges of enrichment and detection of the novel coronavirus in complex biological environments," said MA Kun, a member of the team.

The cluster magnetic beads exhibited excellent magnetic properties, high homogeneity, and chemical stability. Furthermore, due to their small size, they demonstrated stable capture capacity and superior binding efficiency, making them a potential solution for the rapid and efficient enrichment and detection of COVID-19.

Compared to commercial beads, Mal-IMB showed a maximum virus loading capacity of 83 μg/mg in complex biological environments and could effectively enrich pseudoviruses as low as 70 copies/ml.

In addition, immunofluorescence and transmission electron microscopy experiments further elucidated the mechanism of ultra-small magnetic bead enrichment in complex biological environments, which not only demonstrated the efficacy of the novel immune magnetic beads, but also provided valuable insights for improving their performance in complex biological environments.

Ultra-small Mal-IMB immune magnetic beads demonstrate efficient magnetic enrichment of COVID-19 and schematic illustration of its mechanism. (Image by MA Kun) 

The smaller cluster magnetic beads exhibited excellent magnetic properties, high homogeneity, and chemical stability. (Image by MA Kun)