RESUMEN
The aim of our study was to evaluate the efficiency of 4 density gradient media for motile cryopreserved spermatozoa selection to Percoll (Kabi Pharmacia, Uppsala, Sweden) and to Puresperm (J.C.D. International Laboratory, L'Aigle, France). Puresperm was the new medium chosen in our laboratory in 1996 as the substitute for Percoll. The solutions tested were 3 colloidal silane-coated silica particle media (Isolate, SpermGrad-100, Sil-Select Plus) and iodixanol (Optiprep). Semen parameters analyzed after selection were concentration, motility, and morphology. Semen parameters after Puresperm gradient had similar values compared to Percoll. Optiprep was less efficient with a poor concentration. Isolate had a comparatively better concentration, but the capacity of selection was not satisfactory. SpermGrad-100 and Sil-Select Plus were less effective than Puresperm. In conclusion, Puresperm could be considered a better alternative to Percoll for cryopreserved spermatozoa migration.