Figure 3 – Powder types of AGXX
microcathode , which generates reactive oxygen species ( ROS ) from water and oxygen . When organic molecules come into contact with the silver microanode , they are oxidised under electron deduction as part of the redox process ( Figure 1 ). Thus , AGXX represents a circular redox system that continuously regenerates and returns into its original state without any material release . It combines multiple mechanisms that damage microorganisms ( Figure 2 ). 3 , 4 First , crucial molecules , lipids , proteins or even the DNA of microbes are oxidised as part of the circular redox reaction induced by AGXX . Secondly , the highly reactive species generated at the microcathode includes superoxide radical anions , hydrogen peroxide , hydroxyl radicals and singlet oxygen . These molecules react quickly with all types of biological matter . They destroy all kinds of microorganisms , including bacteria , viruses , algae and fungi , by first oxidising the lipids in the cell membrane or cell walls , then attacking intracellular proteins and DNA . In the course of their reaction with organic matter , ROS finally decompose into water . Thus , the reaction takes place without the release of any harmful side products . Thirdly , the difference between electrochemical potentials of silver
and ruthenium induces a microelectric field , which further supports the antimicrobial effect of AGXX . If microorganisms fall under the influence of the microelectric field , this induces ion migration through the electrolytically conductible cytosol of the cell , resulting in polarisation of the electrochemically isolating lipid membrane . Consequently , the potential difference is focused on the cellular membrane , which causes an irreversibly widening of the membrane pores and finally leads to cytosol leakage and cell death . 3
Advantages of AGXX
AGXX promises a long-lasting antimicrobial effect , as its mechanism of action is circular and is not based on the leaching of metals or any environmentally harmful substances .
Figure 4 - Antimicrobial efficacy of AGXX in PA 6 & PA 6,6
In addition to its long-lasting effect , the mechanism of action also leads to a broad effect against multiple microorganisms . AGXX has been successfully tested against more than 130 types of microorganisms , including bacteria , viruses , algae and fungi . It was also proven effective against dangerous bacteria , such as silver-resistant E . coli and methicillin-resistant S . aureus ( MRSA ) strains , as well as COVID viruses . 5 Moreover , AGXX prevents biofilm formation . 6 Bacteria organised in biofilms are usually much more resistant to antibiotics and therefore pose a particular health threat . They also form the basis for fouling and biocorrosion , which severely limit the functionality and lifetime of devices continuously exposed to microorganisms , such as water filters . In addition to the advantages derived from its mechanism of action , AGXX also offers regulatory advantages . For example , AGXX particles and products containing them can already be used in compliance with the BPR . To meet the requirements for use in different materials , Heraeus is working on the
32 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981