No More IVF Mix-ups: Barcode Your Sperm And Eggs

It may sound like something out of science fiction, but researchers in Barcelona have found a way to attach unique barcodes to sperm and egg cells in order to eliminate in vitro fertilization mix-ups. Though said mix-ups are rare, the consequences can be emotionally devastating for those involved. Scientists have now created microscale polysilicon chips that attach to individual sex cells allowing a foolproof means of identification with no apparent health side-effects.

Human spermatozoa: these 50 micron long cells can now be given a unique barcode to prevent IVF mix-ups. Image by Bobjgalindo.Human spermatozoa: these 50 micron long cells can now be given a unique barcode to prevent IVF mix-ups. Image by Bobjgalindo.

Generally, cell identification is carried out by labelling the sample container – a method that is undeniably simple and cost-effective. But it leaves the door open for human error in a field where errors are truly unacceptable. Recall the case last year in which a couple only detected the sperm bank’s mistake when their child was born with an unexpected skin color. For this reason, the idea of labelling the sample itself instead of simply the test tube is very compelling.

The polysilicon tags measure just 10 by 6 microns and are one micron thick. For comparison, a human hair has a diameter of approximately 100 microns, a sperm cell is around 50 microns long and an egg cell is on the order of 120 microns across. The barcodes were fabricated cheaply and easily using traditional silicon processing technology. Because silicon is already used in the vast majority of electronic devices, and because the dimensions of the bar codes are quite large as compared with many electronic components, the manufacturing was relatively simple – an important consideration as mass quantities will likely be required. Indeed, when tagging sperm, 120,000 barcodes were employed for a single sample.

The first iteration of the barcodes consists of a start-read marker and eight code-able bits allowing for 28 or 256 unique codes. The researchers are quick to note, however, that changes to the shape or number of bits could exponentially increase the number of combinations.

The actual tagging of the cells is carried out differently depending on the type of cell. In the case of spermatozoa, hundreds of thousands of the microscopic barcodes were simply added to semen and mixed to yield a homogeneous mixture. For the egg cells, oocytes, the polysilicon chips were biofunctionalized with a wheat germ-derived protein lectin known to bind cell membranes. In either case, a simple microscope is all that is needed to conclusively identify each material.

The most important consideration in this research is of course not efficacy, but rather safety. To gain insight into this area, the scientists conducted rigorous testing. The samples were first analyzed in the laboratory and compared with un-tagged control cells. Absolutely no difference in cell development, lifetime, cryopreservation or viability was observed. In reference to male and female sex cells, respectively, the authors state “all semen samples analysed showed normal values of pH, volume, concentration, motility and morphology, according to the World Health Organization laboratory manual for the examination and processing of human semen” and “the development rates of tagged and control embryos were equivalent at all stages”. To further test the results in a true human model, coded cells were used in the artificial insemination of rabbits and neither pregnancy rate nor offspring viability was impacted. 

Despite its proven safety record, this technology has not yet been approved for use in human cells; though this is a likely outcome in the near future. Even now there is a market for the procedure, however, in industries like livestock farming or show-animal breeding where the sperm of certain males can command a very high price.

Via: New Scientist, Reprodctive BioMedicine, and Human Reproduction.