Fertilisation involves bringing sperm and eggs together in the lab, termed insemination. If semen analyses or previous IVF treatment shows that the sperm is of good quality, insemination can be performed by simply mixing a prepared volume of sperm with eggs in tiny wells of culture media within a Petri dish and allowing the sperm to fertilise the egg on its own. This is often referred to as standard IVF.
The other method for fertilising the egg is called Intra Cytoplasmic Sperm Injection or ICSI. This procedure is typically used when sperm quality is low, which reduces the chances of it being able to fertilise the egg on its own. During ICSI, a single sperm is selected and, using a high-powered microscope, the sperm is injected into the egg’s substance (known as cytoplasm) using a very fine needle that punctures the eggs outer layers.
The movie below depicts mouse eggs being microinjected with a solution of RNA in Prof Homer’s research laboratory. The process is very similar to ICSI and involves stabilising the egg by applying suction through a tiny glass holding pipette (left) and introducing the sharp injection needle through the egg’s outer layers and into the egg substance (right). A pulse of pressure is then applied into the injection needle to expel its contents into the egg.