AN ELECTRONIC ID tag that works even when cryogenically frozen could help prevent some of the mix-ups in IVF clinics that can cause heartbreak for would-be parents.
Last week, when they revealed that their last viable embryo had been taken from cryogenic storage at an IVF clinic in Cardiff and mistakenly implanted into another woman. The recipient, on learning of the bungle, terminated her pregnancy.
鈥淭heir last viable embryo was taken from cryogenic storage and implanted in the wrong woman鈥�
Advertisement
There were eight similar 鈥渃lass A鈥� IVF mix-ups in 2008 in the UK fertility industry, according to its regulator, the Human Fertilisation and Embryology Authority. Class A means the wrong eggs, sperm or embryo were used in an IVF procedure. Such mix-ups occur when eggs, sperm or embryos are mislabelled due to slips in a lab鈥檚 verification procedures.
Part of the solution is a system called IVF Witness, which constantly monitors the identity of the gamete and embryo containers that are brought near to each other on the IVF lab bench 鈥� sounding an alarm if eggs about to be introduced to sperm, say, have come from the wrong woman.
The system, made by (RI) of Falmouth, UK, is installed in 16 of the nation鈥檚 90 IVF clinics. It uses 15-millimetre- square, sticky-backed plastic to label any dishes or vials that eggs, sperm or embryos are placed into. The tags house a memory chip and a coiled copper radio antenna. Each tag鈥檚 memory is programmed with a unique ID code that is transmitted by its antenna when an ultra-low-power radio pulse interrogates the chip.
As a sample moves through the IVF process, the ID code of every container it is placed in is logged, providing a secure ID audit trail. So, in theory, only sperm and eggs from the right couples can be brought together, and the resulting embryos will be implanted into the right woman.
There鈥檚 just one problem: the RFID tags do not work at -196 掳C 鈥� the temperature of liquid nitrogen 鈥� and so cannot be used with gametes and embryos that are cryogenically stored.
The reason is twofold, says RI鈥檚 technical director David Lansdowne. The low temperature raises the conductivity of the copper antenna, shifting its working frequency beyond that of the RFID reader. And as the temperature drops, the voltage needed by the RFID chip鈥檚 transistors to switch on and off (to 鈥渟quawk鈥� out its ID code) increases until it cannot draw enough power from the field generated by the reader鈥檚 signal.
So RI has developed a new type of tough plastic RFID tag that works at cryogenic temperatures. Its antenna 鈥� a copper coil wrapped around a piece of ferrite 鈥� maintains its low-temperature frequency in the readable range. And the chip is built from novel, enlarged transistors with many more charge carriers, enabling it tap enough wireless power from the reader鈥檚 signal.
Andy Glew, director of embryology at the Herts and Essex Fertility Centre in Cheshunt, Hertfordshire, UK, welcomes the idea: 鈥淏y tracking the gametes and embryos through every step of the process, the risk of disaster can be avoided.鈥�
