Non-invasive technique could distinguish fertile and infertile human sperm cells

The findings are published in the journal The Analyst, and are also featured in Highlights in Chemical Biology and in the news section of Chemistry World of the Royal Society of Chemistry in May.

Nature has optimized the main function of sperm cells in a similar way to race cars. These cells consist of sub-cellular organelles that contain, for example, mitochondria. Mitochondria are the power stations supplying energy for sperm motion and mobility -- one of the crucial factors in fertility. The research team has shown that cellular damage on a molecular level in mitochondria can be present although changes in form and morphology are not visible. This stresses that besides morphology, which is a strict criterion by the WHO Manual for Andrology Laboratories to classify human sperm fertility, it is now possible and necessary to improve the test criteria by incorporating chemical signatures.

The RUB researchers obtained detailed 3D chemical maps which do not require the introduction of additional labels or markers. The Raman micro-spectroscopy used in this study detects sub-cellular components using the spectral fingerprints of molecules based on their characteristic vibrations. Different organelles within human sperm are visualized by their chemically unique Raman spectra. In addition to optical and morphological images, it is now possible to directly image the chemical constituents of individual human sperm cells.

This discovery may contribute to the development of new standards for the classification of healthy fertile and damaged infertile human sperm cells. Since the sperm count of human males around the world has dropped an alarming 50 per cent of what it was more than 50 years ago, there is an urgency to investigate human fertility organelles.

The development of innovative spectroscopic and microscopic methods for high resolution imaging of living cells is one of the research areas at the Chair of Physical Chemistry II (Prof. Dr. Martina Havenith-Newen). The work of Konrad Meister, Diedrich A. Schmidt and Erik Bründermann uses confocal Raman microscopy for detailed 3D imaging and identification of organelles of human sperm cells to reveal the origin of infertility on the molecular level. The funding for the Raman microscope used in this study was supported by the Federal Ministry of Education and Research (BMBF 05KS7PC2).