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Antiviral activity of chitosan-based bioactive polymers against bacteriophage Phi6

The antiviral properties of chitosans, in contrast to chitosan derivatives, have been little considered. For this reason, the study presented here investigated the antiviral activity of three chitosans against the SARS-CoV-2 surrogate, bacteriophage phi6.


Plohl O, Fric K, Filipić A, Kogovšek P, Tušek Žnidarič M, Zemljič LF. First Insights into the Antiviral Activity of Chitosan-Based Bioactive Polymers towards the Bacteriophage Phi6: Physicochemical Characterization, Inactivation Potential, and Inhibitory Mechanisms. Polymers (Basel). 2022 Aug 17;14(16):3357. doi: 10.3390/polym14163357. PMID: 36015613; PMCID: PMC9413598.

The 2019 outbreak of Covid-19 virus has infected more than 500 million people by August 2022 and is transmitted partly via surfaces along with aerosols. One way to prevent contagions from Covid-19, as well as other viral diseases such as norovirus, is the availability and use of antiviral materials for personal protection. Antiviral coatings could thus prevent contamination and infection with viruses and other microorganisms.

So far, synthetic, inorganic or photocatalytic coatings, for example, have been used for this purpose, but they have limited efficiency, negative environmental impact and high toxicity.

An alternative to this may be the development of antiviral coatings based on natural polymers such as chitosan. Chitosan has excellent antibacterial properties. However, little is known about the antiviral properties due to the poor solubility of chitosan at neutral pH. These have been studied in more detail only for chitosan derivatives.

For this reason, the antiviral properties of three chitosans were investigated in the present study. In addition to a low and a high molecular weight chitosan (LMW-CS and HMW-CS), quaternized low molecular weight chitosan was also analyzed. Due to the similar size, the rsRNA bacteriophage phi6 was used as an equivalent to SARS-cov-2.


  • Use of chitosans at the same mass concentration (1.25 mg/ml) to prevent influence concentration on virus inactivation
  • High virus inactivation against phi6 at low pH (4.5) for LMW-CS and HMW-CS (100% and 99.9995%), significantly lower for quart-LMW-CS (78.76%)
  • Completely different behavior at neutral pH of 7.4: no virus inactivation of LMW-CS and HMW-CS while quart-LMW-CS showed an inactivation rate of 97.15 %
  • reduction of phi6 diameter from approx. 85 nm to approx. 63 nm after contact with CS
  • Change in morphology of virus particles due to dissolution of lipid envelope
  • Incubation of phi6 for 2 h with LMW-CS: changes in FTIR indicates elementary structural changes
  • Negligible changes in zeta potentials of chitosans before and after contact with virus
  • pH 4.5: increase in hydrodynamic diameters upon interaction between phi6 and CS especially in LMW-CS and HMW-CS → indication of electrostatic interaction likely damaging virus envelope
  • No increase in hydrodynamic diameters at neutral pH
  • No influence molecular weight and deacetylation on virus inactivation

Conclusions: In summary, the presented study demonstrated the inactivation potential of different chitosans against bacteriophage phi6, a surrogate for SARS-CoV-2. In addition, inactivation was shown to be pH dependent, although independent of molecular weight and degree of deacetylation. CS and phi 6 interacted with each other via electrostatic interactions, which likely led to lipid envelope dissolution.

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chitosan, antiviral drugs, SARS-CoV-2

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