Zeta method: A noninvasive method based on membrane charge for selecting spermatozoa expressing high level of phospholipaseCζ.

Intracytoplasmic sperm injection (ICSI) is a technique developed to help attain successful fertilisation for couples with severe male factor. However, a small percentage of couples confront low or failed fertilisation, mainly due to failed oocyte activation. Several studies have introduced phospholipase C zeta (PLC zeta) as the main sperm factor inducing oocyte activation and thereby has the potential to act as a biomarker for the prediction of ICSI fertilisation outcome. On the other hand, researchers have focused on novel sperm selection procedures based on cellular characteristics of spermatozoa such as surface electrical charge (Zeta potential) to isolate normal sperm subpopulation with intact chromatin. Therefore, we aimed to compare PLC zeta between Zeta method and routine sperm preparation procedure: density gradient centrifugation (DGC). Our results showed that number of PLC zeta-positive spermatozoa was significantly low in the Zeta method, but the intensity of PLC zeta protein in such spermatozoa was significantly higher than DGC procedure. Therefore, the combination of DGC with Zeta procedure may allow selecting the population of spermatozoa with a high percentage of PLC zeta which may also contain a high amount of PLC zeta and with intact chromatin. This sperm selection procedure can open a new approach for infertile men with previously failed fertilisation.