Photodynamic Inactivation: How Singlet Oxgen Dismantles a Virus
Singlet oxygen has been shown in scientific literature to affect all three structural layers of a virus 1,2,3
A virus is a microscopic infectious agent that cannot reproduce on its own and must invade a living host cell to replicate. It is considered active as long as its structure is intact and it can infect a host cell; once it loses that ability, it is considered inactive. A virus particle – also known as a virion – consists of genetic material (either RNA or DNA) encased in a protective protein shell called a capsid. Some viruses also have an outer lipid envelope that helps them enter host cells. Singlet oxygen has been shown to be effective against all three of these components.
Viruses like SARS-CoV-2 and Influenza are surrounded by a lipid (fat) envelope that protects them and helps them infect host cells. Singlet oxygen repeatedly attacks and oxidizes this outer layer – much like how salt causes metal on a car to rust and weaken over time. As the envelope breaks down, the virus loses its ability to bind to cells and becomes more vulnerable to additional damage.4 5
The next layer – the protein shell, or capsid – gives the virus its shape and protects its genetic material. In some viruses, additional surface proteins – such as the spike proteins on SARS-CoV-2 – help the virus attach to and enter host cells. Singlet oxygen disrupts vulnerable but essential regions of these proteins – like breaking a support pole in a tent or dropping a phone in water – where even a small amount of damage can cause the entire system to fail.6
At the core is the viral genome – its RNA or DNA – the instruction manual for replication. Singlet oxygen can damage this genetic material too, disrupting strands like ripping pages from a book, making it impossible for the virus to reproduce.7
Scale, Speed, and Precision
Viruses are incredibly small – typically 100 to 250 nanometers, far smaller than a speck of dust – and singlet oxygen molecules are even smaller, at just 0.12 nanometers (roughly 700 to 1,000 times smaller than a virus like H1N1).8
A single photosensitizer molecule can generate 10,000 to 100,000 singlet oxygen molecules over its lifetime. On a theoretical surface area similar to that of a mask, more than a trillion singlet oxygen molecules can be generated every second when exposed to typical ambient indoor light.2 5 9
Each singlet oxygen molecule is short-lived – lasting less than 10 microseconds before returning to ordinary oxygen – and acts only in its immediate vicinity. But together, they form a relentless, invisible army. It’s like an endless wave of ants swarming a much larger intruder – each encounter may be small, but the cumulative effect can overwhelm and dismantle viral structures.5 9
Why It Works Broadly
Because a virus becomes non-infectious (inactive) if even one of its structural layers is dismantled, singlet oxygen is considered a broad-spectrum antiviral mechanism in the scientific literature.1 2 While different viruses have evolved unique ways to shield themselves, it is unlikely that all three structural layers – envelope, proteins, and genome – can be fully protected, making singlet oxygen an effective mode of action studied in numerous disinfection technologies.3 6 7
References
1. Tardivo JP et al. Photodiagnosis Photodyn Ther. 2005;2(3):175–191.
2. Hudson JB et al. Photochem Photobiol. 1997;65(5):723–729.
3. Wieding JU et al. Ann Hematol. 1993;67(6):259–266.
4. Córdoba-Lanús E et al. BMC Infect Dis. 2021;21(1):1169.
5. Lendvay TS et al. Infect Control Hosp Epidemiol. 2022;43(7):876–885.
6. Wigginton KR et al. Environ Sci Technol. 2012;46(3):12079–12087.
7. Ravanat JL et al. J Biol Chem. 2000;275(51):40601–40604.
8. Lobo CS et al. Photochem Photobiol Sci. 2022;21(6):1101–1109.
9. Dougherty TJ. Adv Photochem. 1992;17:275–311.