A Concept in Bactericidal Materials: The Entrapment of Chlorhexidine within Silver

Abstract

A new concept in bactericidal agents is described: the entrapment of an organic biocidal agent within a bactericidal metal, which leads to synergism between the two components. Specifically this concept is demonstrated for the entrapment of chlorhexidine digluconate (CHD) within an aggregated silver matrix, a metal known for its own biocidal qualities, forming the CHD@silver composite. The bactericidal efficacy against E. coli is evaluated and compared with the separate components. While the bactericidal efficacy of the individual ingredients (CHD and metallic silver) is very low, CHD@silver exhibits a markedly enhanced efficacy. This enhanced bactericidal effect is partially attributed to the simultaneous release and presence of the active biocidal ingredients CHD and Ag+ in the solution. Detailed composite characterization is provided.

Random peptide mixtures entrapped within a copper-cuprite matrix: new antimicrobial agent against methicillin-resistant Staphylococcus aureus

“…The absence of detectable peptide release from the composites also suggests the formation of strong interactions between the LK RPMs and copper, in addition to their physical entrapment. This is in accord with reports that large molecules such as Nafion 31 and the enzyme acid phosphatase 30 are not released from similar composites, although it is possible for small molecules 8,27,29 . According to the results of the TGA and elemental analysis, the LK 20-mer RPM was entrapped more efficiently than the LK 10-mer RPM.…”

Bioactive doped metals: high synergism in the bactericidal activity of chlorhexidine@silver towards wound pathogenic bacteria

“…4a (1 h) and b (26 h); and it is seen that they are quite different: 60% of the entrapped CH molecules (based on thermogravimetric analysis) are rapidly released at a rate of 16.0% of the entrapped CH/min (in short, here and below, %CH/min), while a slow release process occurs at a rate of 0.2%CH/min. The phenomenon of having two distinct entrapped populations, one which is easily accessible by the solvent, and the other which is held much more tightly was seen also in our earlier studies both with CH 7 and with dyes@copper. 10 Pressing the powder changes this behavior: The initial rate of release drops to 1.8%CH/min and after 15 min only 27%CH is released.…”

“…2) shows that the synergistic effect relies on the simultaneous presence of both active components. It may come as a surprise, but as already noted in our preliminary study with E. coli, 7 we have not encountered in the literature antibacterial synergism which is due to the co-administration of the separate ingredients-CH and metallic silver. Since such administration causes rapid killing of the bacteria, one can envisage future applications which use in the same formulation both CH@Ag and free CH.…”

Antibacterial activity of silver-killed bacteria: the "zombies" effect

“…Very recently, Said et al showed25 that Ag + is both bacteriostatic and bactericidal in growth medium at comparable silver concentrations, and that in simulated wound fluid, bactericidal activity is still possible but at higher concentrations. It follows therefore that prolonged action of silver ion releasing formulations2627 benefit, at least in part, from the phenomenon we describe here. We also believe that this phenomenon is potentially general, and may exist in other antibacterial agents, particularly in those that are stable and undergo minimal degenerative transformations (quaternary ammonium compounds, copper, and metal oxides).…”