product photo of KnockOut Serum Replacement for Cell Culture bottle

KnockOut Serum Replacement (SR) is a defined, FBS-free supplement optimized for the maintenance, expansion and differentiation of human and mouse pluripotent stem cells (PSCs).

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KnockOut SR key features

  • Defined, FBS-free formulation—Designed specifically to replace fetal bovine serum (FBS) in feeder-dependent human and mouse PSC cultures.
  • Improves maintenance of undifferentiated PSCs—Cultures using KnockOut SR exhibit more compact colony morphology and lower rates of spontaneous differentiation compared to FBS-based supplementation (Figures 1 and 2).
  • Lot-tested for PSC support—Unlike typical FBS lots, each lot of KnockOut SR is verified for performance with PSCs, helping reduce variability in culture outcomes.
  • Supports multiple stem-cell workflows—Includes applications such as feeder-dependent expansion of ESCs/iPSCs, cryopreservation, embryoid body formation, differentiation, and derivation of new lines.
  • Stable supply and cost-predictability—Eliminates supply fluctuations and pricing volatility commonly associated with FBS, helping with budget planning and reagent consistency.
  • Xeno-reduced and clinically compatible options available—CTS KnockOut SR XenoFree Medium is available for research translation toward clinical applications.
Bar graph showing the percent undifferentiated mouse ESCs observed when cultured in various combinations of traditional and KnockOut DMEM and ESC-qualified FBS and KnockOut SR. Highest percentage of undifferentiated was achieved with the KnockOut DMEM plus KnockOut Serum Replacement combination

Figure 1. Undifferentiated ESC growth with KnockOut SR. Murine D3 ESCs were cultured at low density in DMEM or KnockOut DMEM supplemented with ESC-Qualified FBS or KnockOut SR and traditional supplements. No LIF (leukocyte inhibitory factor) was used. After 7 days, colonies were fixed and stained for alkaline phosphatase, a marker for undifferentiated ESC. Undifferentiated colonies were scored based on morphology and staining characteristics.

Phase contrast image shows iPSC colonies with normal morphology, surrounded by MEFs

Figure 2. iPSCs grown in KnockOut SR exhibit compact colony morphology. iPSC colonies were grown in 20% KnockOut SR, DMEM/F-12 with GlutaMAX supplement, 4 ng/mL Gibco bFGF, and 100 µM 2-mercaptoethanol on mitotically inactivated mouse embryonic fibroblasts. iPSC were passaged with the StemPro EZPassage Disposable Stem Cell Passaging Tool.


Complete media system for serum replacement cell culture

SupplementBasal mediumRecommended reagent
KnockOut Serum Replacement
DMEM/F-12 or KnockOut DMEM
bFGF or LIF

Serum replacement cell culture resources

Protocols

For Research Use Only. Not for use in diagnostic procedures.

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