Sperm washing process

In order to separate the best sperm from the rest of the sample and ensure that they are free of HIV, it is most common to carry out a double washing process:

• Density gradients: several layers of different concentrations are added to separate the different cellular fractions of the semen. After centrifugation of the sample, the motile sperm are at the bottom of the tube.
• Swim-up: sperm retrieved from density gradients are added to a tube with semen preparation medium and incubated under controlled conditions. The sperm with the best mobility will be found in the upper part of the sample, from where they will be recovered for use in the treatment of assisted reproduction.