Normal fertilization requires both healthy oocytes and sperm with their respective indicators. Healthy oocytes show normal cytoplasmic morphology, sufficient distribution and potential of mitochondria, low reactive oxygen species, unreleased cortical granules, and a barrel-shape of spindle. On the other side, healthy sperm must have normal morphology from head to tail, intact acrosome and DNA, sufficient number within an ejaculate, and high motility either progressive and hyperactive. If some of those case are not fulfilled, i.e., lacking sperm number/concentration and aged oocytes, normal fertilization would not likely to occur. At this point, ICSI come to an aid.
ICSI is a type of IVF, yet ICSI promotes fertilization through the direct injection of a single sperm into a single egg. The lack of moving ability of sperm to penetrate the oocyte or the release of cortical granules that harden the zona pelucida in aged oocytes, prevents the occurrence of fertilization. The injection needle of the micromanipulator can bypass this barrier. Conventional ICSI uses a sharp injection needle without PIEZO and a blunt needle with PIEZO-assisted.
Photos are personal documentation.
