We are looking for the most effective way to reprogram factor free iPS cells.

Answer

Currently, the most efficient non-integrating system is Sendai virus. For effective reprogramming, the reprogramming system and the reprogramming medium are both important variables. TeSR™-E7™(http://www.stemcell.com/en/Products/All-Products/TeSRE7.aspx) is an optimized xeno-free and defined reprogramming medium that enables the generation of high quality iPS cell colonies with reduced differentiation and fibroblast growth.