Micromechanical resonators pick up mass differences between X and Y chromosomes to sort sperm cells. Mass differences between bovine sperm bearing X or Y chromosomes have been measured by researchers in Italy. The findings could be used to develop a gentle sperm sexing technique.
A microbridge sensor developed by Marco Mauro and his team at Novaetech, Napoli, in collaboration with the Italian Experimental Institute, Lazarro Spallanzani in Cremona, is a non-invasive alternative for sorting live sperm cells.
The sensor, able to measure picogram masses, is a microcantilever consisting of a resonating micrometric capillary that is fixed at both ends and connected to an external fluidic system. The flow of a fluid containing suspended sperm is controlled to allow a single sperm cell to enter the capillary at any one time. As the sperm flows through a sensitive area of the capillary a variation in the forced vibration is detected. The signal is proportional to the buoyant mass of the sperm. ‘This is the first direct measurement of a single sperm’s mass,’ says Mauro. These preliminary results provide evidence of measurable differences in the mass of sperm cells bearing X or Y chromosomes.