Laser Pulse Application in IVF

Abstract

In-vitro fertilization (IVF) involves the culture and manipulation of gametes and embryos within a laboratory environment. IVF procedures are channeled towards enhancing fertilization and assisting the normal developmental physiology of the growing embryo to increase implantation potential, culminating in the birth of a healthy baby. Laser and its selective application to various steps in the IVF process is an area of growing interest. In this chapter, we review the use of laser technology in the field of assisted reproduction as well as in stem cell research. The first step in the IVF process involves fertilization of the oocyte. For this to occur, sperm must penetrate the outer membrane known as the “zona pellucida” which surrounds the egg. This natural barrier prevents the entry of multiple sperm. Often it is necessary to assist fertilization by directly injecting a single sperm into the oocyte, a technique known as Intracytoplasmic Sperm Injection (ICSI). Laser pulse has been utilized to immobilize the human sperm tail before ICSI and in assisting the injection technique by creating a hole in the zona (laser assisted ICSI). Once successfully fertilized, the resulting embryo undergoes successive cell divisions. To implant on the uterine wall, the embryo must escape from the surrounding zona, a process known as hatching. Laser assisted hatching has been employed to create a controlled opening of the zona and facilitate embryo implantation after transfer to the patient’s uterus. Zona opening through use of a laser pulse has also been used to extract a single cell from the growing embryo for preimplantation genetic diagnosis (PGD). Another application of the laser in reproductive biology has been cellular microsurgery. Embryonic stem cells can be isolated from a blastocyst stage embryo by selective ablation of trophectodermal cells, leaving behind the stem cell source material. More recently, laser has been used to induce fluid loss from the blastocyst stage embryo before cryopreservation. We discuss this novel application of laser and our own work with artificially collapsing blastocysts before freezing to reduce ice crystal damage. This article also documents the evolution of laser pulse in IVF from the first generation of lasers with UV range wavelengths to the newer generation of lasers with emissions in the infrared range. Design characteristics for the ideal laser pulse for clinical IVF use are presented. Finally, safety considerations as regards laser usage at such early stages of development and potential risks to the newborn are discussed. The current FDA classification and approved devices are also reviewed. Numerous engineering devices have been used in biomanipulation and a thorough understanding of both the disciplines of biology and engineering is imperative to develop