Synthetic Nanoparticle Blocks COVID-19 by Nearly 99% in Lab Tests

Scientists from Swansea University, Freie Universität Berlin, and Charité–Universitätsmedizin Berlin have developed a synthetic sugar-coated nanoparticle that can almost completely block SARS-CoV-2 from infecting human lung cells.

The tiny particle is coated with polysialosides, chains of a natural sugar called sialic acid found on human cells. Many viruses, including coronaviruses, use these sugars as docking points to start infection.

By mimicking this natural structure, the nanoparticle acts as a decoy, latching onto the virus’s spike protein and preventing it from binding to real cells.

In lab experiments, the most effective version bound to the virus 500 times more strongly than a similar compound made with sulfates instead of sugars.

“The dendritic polyglycerol based polysialosides dPG500SA0.55 and dPG500SA0.25, with a dissociation constant Kd of 4.78 nm and 10.85 nm, respectively, bind ≈500 times stronger than the high density polysulfated analog dPG500S0.55, to intact SARS-CoV-2 virus particles or isolated spike protein.” – Khatri, V., et al.

Even at lower doses, it blocked infection by up to 98.9% and worked against both the original SARS-CoV-2 strain and the more infectious D614G variant.

“In the presence of dPG500SA0.55 SARS-CoV-2 replication was inhibited up to 83.8% at 24 hours post-infection and to 98.9% at 48 hours post-infection at the maximum applied compound concentration of 1 mg ml−1 which is equivalent to 0.5 μm, when compared to untreated Calu-3 cells.” – Khatri, V., et al.

Importantly, it was not toxic to human cells.

“A cell viability assay was conducted to exclude the possibility that the compounds were cytotoxic. The number of viable cells remained at a constant level with increasing compound concentration at the highest dose of 1 mg ml−1 after 24h and 48h post treatment “ – Khatri, V., et al.

Unlike vaccines, which train the immune system, this approach is a physical shield directly stopping the virus from attaching to cells.

Researchers say the technology could lead to new antiviral tools such as nasal sprays, surface disinfectants, or treatments to protect high-risk groups from COVID-19 and potentially other viral threats.

Citation

Khatri, V., et al. (2025). Polysialosides Outperform Sulfated Analogs for Binding with SARS-CoV-2. Small. https://doi.org/10.1002/smll.202500719