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The Modernization of Vitrification

The Modernization of Vitrification

Vitrification has changed how embryos and oocytes are cryopreserved, enabling higher survival rates than previous methods. However, with no significant advances in vitrification media in over a decade, there was a growing need to improve formulations that further reduced stress and improved survival rates. FUJIFILM Irvine Scientific answered this need by developing Vit Kit-NX.

As the latest advancement in vitrification media, Vit Kit-NX brings the vitrification process in line with both the culture and handling steps of IVF. Vit Kit-NX builds on the benefits of human embryo-specific Continuous Single Culture Medium (CSCM) and Multipurpose Handling Medium (MHM) to help minimize stress on oocytes and embryos during the vitrification process. The newly formulated vitrification media delivers consistent results and high oocyte and embryo survival rates while offering effective, flexible, and economical media ideally suited for the modern IVF laboratory.

Human embryo-specific base medium

Many vitrification media feature an M199 base, a formulation initially designed for chick embryo fibroblasts—not human embryos. Though sufficient, FUJIFILM Irvine Scientific determined that a standardized base medium, using a targeted formula to support human embryos and gametes for culture, would reduce stress on embryos and oocytes to achieve high survival rates. The base medium used in Vit Kit - Freeze NX and Vit Kit - Warm NX is Continuous Single Culture Medium (CSCM), a medium formulated specifically for human embryos. For embryos cultured in CSCM, this provides a steady, continuous system that reduces stress and achieves high survival rates.

Founded on a trusted formula

Vit Kit-NX retains the original Vit Kit system's essential benefits, such as DMSO and EG as permeating cryoprotectants, dextran serum supplement as a protein source, and gentamicin as an antibiotic. Key differences include switching to CSCM as a base medium to deliver consistency throughout the in vitro embryo culture environment, and using a dual-buffering system with HEPES and MOPS to protect pH stability. Finally, the addition of trehalose, a non-permeating cryoprotectant, supports higher glass transition temperature and stabilizes the cell membrane.

Consistent survival rates across different vitrification media

Vit Kit-NX works flexibly with different vitrification media and is capable of warming human oocytes frozen in the original Vit Kit and a competitor's vitrification medium.

Figure 1. Vit Kit - Warm NX was capable of warming human oocytes frozen in Vit Kit (A) and a top competitor’s vitrification medium (B)

Previously frozen MII oocytes were re-frozen in different vitrification media with the Cryolock device. MII oocytes were counted towards the survival rate and were recovered in CSCM-NXC (FUJIFILM Irvine Scientific, PN 90168) for the immediate and 2h post-thaw time points. The study was performed in collaboration with World Egg Bank in Phoenix, Arizona, USA.

High implantation and pregnancy rates

Houston Fertility Institute, led by Wei Hua Wang, PhD, evaluated the performance of the Vit Kit-NX Suite, in which the Blastocyst Survival Rate, Implantation Rate, and Clinical Pregnancy Rate were assessed.

Cross-warming evaluation was first conducted using the original Vit Kit - Freeze with the new Vit Kit - Warm NX. The cross-warming evaluation demonstrated that high implantation and pregnancy rates could be achieved, with results equivalent to using Vit Kit - Thaw ("Cross-Warming" in Figure 2).

High implantation rate and clinical pregnancy rate remained consistent when embryos were vitrified using the new Vit Kit - Freeze NX and warmed with the new Vit Kit - Warm NX ("After" in Figure 2). Download the full case study to learn more.

Figure 2. Strong performance of embryos vitrified and warmed with new vitrification media: Vit Kit - Freeze NX and Vit Kit - Warm NX

Embryo Performance Before Cross-warming After
  Vit Kit - Freeze & Vit Kit - Thaw Vit Kit - Freeze & Vit Kit - Warm NX Vit Kit - Freeze NX & Vit Kit - Warm NX
Total Warmed: 2,343 310 229
Survival Rate: 97.7% 99.2% 98.8%
Single Embryo Transfer Rate: 78.4% 81.9% 89.1%
Implantation Rate: 49.6% 54.0% 56.5%
Clinical Pregnancy Rate: 56.0% 60.0% 60.3%


Between November 2019 and January 2020, Dr. Wang's lab evaluated the performance of the Vit Kit-NX Suite. Multiple vitrification devices were utilized with Vit Kit - Freeze (FUJIFILM Irvine Scientific, PN 90133-SO) for 310 cycles, and later with Vit Kit - Freeze NX (FUJIFILM Irvine Scientific, PN 90188) for 229 cycles. Embryos were subsequently warmed in Vit Kit - Warm NX (FUJIFILM Irvine Scientific, PN 90183), starting with 500 µl of thawing solution, one drop of 160 µl of dilution solution, and finally washed in two drops of 80 µl each of washing solution. The embryos were then recovered in a 5mg/mL HSA complete media.

Streamline your process. Safeguard the future.

Protect precious human oocytes and embryos at every stage of the IVF cycle. By building on the benefits of current IVF media and tailoring them specifically for the vitrification process, the formulations of Vit Kit-NX are targeted to support human oocytes and embryos and create a steady, continuous system that reduces stress to achieve better results. To learn more about how a base medium affects vitrification, read an expanded discussion in our white paper.

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