German researchers have developed a new way of measuring the quality of human sperm cells by creating a chemical 'signature'.

Using Raman microspectroscopy, a fast and non-invasive technique, they were able to image the specialised regions of sperm and distinguish between unhealthy and healthy fertile cells following radiation damage.

This novel method therefore incorporates chemical information into the diagnostic tests of male fertility, rather than the current method of relying solely on morphological characteristics.

The scientists looked at detailed maps of the sperm, particularly focussing on the middle section, which contains the mitochondria (mitochondria produce the energy the sperm need for motility). They then exposed the sperm cells to ultraviolet (UV) radiation, which can damage DNA. When changes in the cells were subsequently examined it was the middle sections that were most severely affected - visible prior to the overall shape of the cell being altered. This damage to the middle section allowed the researchers to easily identify the radiation-damaged sperm among the intact, healthy cells.

Worldwide, there has been a 50 per cent reduction in the sperm count of men over the last 50 years. The current World Health Organisation (WHO) Manual for Andrology Laboratories presents strict criteria for classifying the fertility of human sperm, based on their morphology (structure and form). However, the new findings highlight the importance of also monitoring the chemical components and structures within the cells when assessing their quality. Such analyses could potentially be used to improve the current standards of fertility testing.

Raman microspectroscopy uses the scattering of light from a laser to examine the characteristic vibrations of molecules and provide a chemical analysis of the components within the cell. This technique overcomes some of the disadvantages of current microscopy methods as it allows living cells to be analysed without being damaged, and also allows the structure and chemical composition of cells to be seen simultaneously.

The work was published in the journal The Analyst.