Lasers in Micromanipulation of Preimplantation Embryos and Gametes

Cut out or poke in--the key to the world of single genes: laser micromanipulation as a valuable tool on the look-out for the origin of disease

The optical micromanipulation systems UV(ultraviolet)-Laser Microbeam and Optical Tweezers Trap, already proven to be powerful tools for 'non-contact' micro-manipulation of gametes, cells and organelles, have now made their way into the nanocosmos of genes and molecules. Force measurements of DNA transcription have been performed and selective DNA molecule micromanipulation gives insight into single molecule behaviour. Retrievement of selected single cells without contamination is an import prerequisite for further processing with modern methods of molecular biology. Laser micro-dissection allows to precisely eliminate any unwanted material or to isolate pieces of chromosomes or single cells of interest with high accuracy and efficiency. This enables the cell or chromosome specific molecular analysis of genes and genetic defects underlying disease, such as cancer or infection. This review article gives an overview of current topics of laser microbeam application in biological or medical research and advanced molecular diagnosis.

Fertilization of bovine oocytes induced solely with combined laser microbeam and optical tweezers

PURPOSE

Our purpose was to show that fertilization of oocytes can be obtained solely by laser light-mediated manipulation of gametes.

METHOD

A small channel was drilled into the zona pellucida of bovine oocytes using an ultraviolet (UV)-laser microbeam. Highly diluted cattle sperm were not able to fertilize the laser drilled oocytes.

RESULTS

Fertilization was achieved only when three to five cattle sperm were trapped with optical tweezers and inserted directly through the laser drilled hole into the perivitelline space. After 20 hr, 3 of 79 (3.8%) oocytes revealed two pronuclei and a sperm tail within their cytoplasm. Cattle sperm are difficult to catch. Therefore, the gametes had to remain for about 20 min in room atmosphere, which might be the reason for the low fertilization results.

CONCLUSIONS

The results indicate that a combined UV-laser microbeam and optical tweezers trap can be used successfully for "noncontact" microinsemination procedures.