pH shifts and precipitation associated with metal ions in tissue culture.

Recently there has been interest in tests to assess the physiological response to surgical implant corrosion products. Both cell culturing in metal-bearing solutions and intramuscular injection of such solutions have been carried out. This paper examines the effects of the constraints of multicomponent equilibrium conditions on the characteristics of the solutions used in these biocompatibility tests. It is demonstrated that, unbuffered, they will have pH values shifted from neutral and that, in the buffered state, these solutions may contain both dissolved metal ions and insoluble hydroxides. The implications of these characteristics for the interpretation of the results of biocompatibility tests are discussed.