Background / Aims
ClO2, the so-called “ideal biocide”, could also be applied as an antiseptic if it
was understood why the solution’s rapid killing of microbes does not cause any harm
to humans or to animals.
Our aim was to study both theoretically and experim entally its reaction-diffusion
mechanism to find the source of that selectivity.
Methods
ClO2 permeation measurements through protein membranes were performed and the time
delay of ClO2 transport due to reaction and diffusion was determined. To calculate
ClO2 penetration depths and estimate bacterial killing times, approximate solutions
of the reaction-diffusion equation were derived. Additionally, as a preliminary test,
three patients with infected wounds were treated with a 300 ppm high purity ClO
2 solution and the healing process was documented.
Results
The rate law of the reaction-diffusion model predicts that the killing time is proportional
to the square of the characteristic size (e.g. diameter) of a body, thus, small ones
will be killed extremely fast. For example, the killing time for a bacterium is on
the order of milliseconds in a 300 ppm ClO
2 solution. Thus, the few minutes of contact time (owing to the volatility of ClO2)
is quite enough to kill all bacteria, but short enough to keep ClO2 penetration into
the living tissues safely below 0.1 mm, minimizing cytotoxic effects.
Pictures of successful wound healings confirm these considerations. Various properties
of ClO2, advantageous for an antiseptic, are also discussed. Most importantly, bacteria
are not able to develop resistance against ClO2 as it reacts with biological thiols
which play a vital role in a ll living organisms.
Conclusion
Selectivity of ClO2 between humans and bacteria is based not on their different biochemistry,
but on their different size. Preliminary clinical results encourage further research
with this promising local antiseptic.
