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Although I do not know of specific recipes for iPSCs freezing medium that don’t use DMSO here is a web link to a site with a good protocol that I know works with DMSO as the freezing adjuvent (http://www.lifetechnologies.com/us/en/home/references/protocols/cell-culture/stem-cell-protocols/ipsc-protocols/reprogramming-fibroblasts-with-cytotune-ips-reprogramming-it.html). An alternative to DMSO is glycerol and can be substituted at the same concentration as DMSO. Recently people have been having success at reducing the level of DMSO from the standard 10% to 7.5% or even 5% without problems. This may work for you. Also, if you are finding toxicity with DMSO or glycerol, make sure you are using cell culture grade reagents from small volumes that are purged with nitrogen gas. Old and oxidized DMSO or glycerol can be toxic to animal cells.