Nanocrystalline silver, gelatinases and the clinical implications.

Nanocrystalline silver (NCS) has proven to be an important wound dressing particularly in chronic infected wounds. However, debate still rages around its use in the case of partially epithelialized wounds, particularly when these are non-infected. Much of the debate has revolved around seemingly contradictory research publications that blurred the use of NCS in these clinical situations, primarily based on reported cytotoxic effects of NCS on cell lines in vitro. MMPs, in particular MMP-9 (gelatinase) has been demonstrated to be pivotal in the progression from keratinocyte cleavage, to migration and re-epithelialisation. High levels promote increases in TNF-α; IL-8 and TGFβ, all associated with exaggerated ongoing inflammation and chronicity. Low levels impede the process of keratinocyte migration. Thus, as in so many clinical situations, a balance of MMP level is extremely important. NCS has been demonstrated to decrease these undesirable high levels of MMP-9 making it an ideal dressing for chronic infected wounds, acute inflamed wounds and burn wounds of all types which are associated with protracted raised MMP-9 levels. The converse applies too-NCS used in a situation of minimal inflammation may undesirably decrease the low levels of MMP-9 and adversely affect epithelialisation. NCS would be contra-indicated in conjunction with cell lines in vitro, cell cultured lines in vivo and integrated artificial matrices with added cell lines. Therapeutic decisions for different clinical situations may thus be made more predictably.