A simulated bodily fluid (SBF) is a solution having ion concentrations comparable to human blood plasma. What should be used to make this solution: DI or millipore water?
I personally would suggest starting with ultrapure millipore water. This will help to ensure you are eliminating as many variables as possible that may be present in your water. My former colleagues and I would make our artificial cerebrospinal fluid with ultrapure millipore water and had great success with our chemoreception studies.
What is the purpose of creating simulated body fluid (SBF)? Is it for an implant to replace bone or for attachment to bone or for any analytical work? however, it is best to use ultra-pure water in simulating body fluid.
For the in-vitro test, simulated body fluid is the best. It provides important information on the compatibility of implants with the body fluid especially how it reacts in a body and its lifespan in the body. You should do the literature survey on this in ACS - Biomaterials, Frontier in Bioengineering 7 Technology, or on Google search searching "in-vitro test for implant". Hope this helps.
Use ultra clean water to wash all water handling equipment and in making SBF for in vitro test and examine implant under high power optical microscope & SEM.