When we first implemented trophectoderm biopsy, making a slit in the zona pellucida and harvesting cells were part of the same procedure.
But we were never fully satisfied with this approach because blastocysts collapse at a different and unpredictable rate. Some blastocysts require additional laser shots and aggressive manipulations to induce the collapse leading to undesirable collateral damage.
Hatching embryos on day 3 made the cells harvesting quicker and cleaner.
However, we observed that manipulations with day 3 embryos may slow down their development. Also, sometimes the embryo hatches by the inner cell mass, making biopsy difficult.
Recently we tried a new technique, which we named Minimal Impact Biopsy or MIB.
The critical element of this technique is a fixed waiting period between a single laser shot for collapsing the blastocyst and trophectoderm cells harvesting. This makes biopsy process more predictable and standart.
[video:https://youtu.be/vqcpBBP5FZo]
Minimal impact biopsy begins with collapsing all expanding blastocysts with a single laser shot in the HEPES buffered medium.
Even though you may not see any immediate reaction or changes, this single shot will suffice to trigger the collapse.
Immediately after the laser treatment, embryos are returned into the culture.
15-20 minutes later the blastocysts are once again transferred into the droplets of the HEPES buffered medium.
At this point they will be partially collapsed, and yet you will be able to clearly see inner cell mass.
With an ample space between zona Pellucida and the embryo, you can make the slit in the location you like and the size you need safely and quickly.
Then proceed with the biopsy in your custom fashion.
Here we use ZilosTK laser, which has worked very well for us for many years and custom biopsy pipettes made in our embryology facility. We also use Nikon microscope with Narishige micromanipulators, along with an air injectors from Narishige and Research instruments.
True to its name, MIB minimizes biopsy impact on the embryo and hopefully will also save you time and stress.