Biophotonics Solutions for Quantitative Live Cell Near Infrared Raman Spectral Analysis of DNA Damage in Spermatozoa

Infertility affects at least one in six couples in the UK. The most common cause man infertility. Male factor infertility is usually characterised by sperm which are too weak to swim to the egg or don't swim at all. The genetic material (DNA) held in these unhealthy sperm is highly likely to be damaged.A treatment which is used in these cases is to inject the sperm into the egg in the laboratory. However, there is at present no way to ensure that the DNA which is transferred in this process is of good quality. There is concern in the medical community that this may lead to high rates of disease such as childhood cancer for children conceived by sperm injection.All the currently available tests for DNA damage require the sperm to be broken open and the DNA extracted to be chemically analysed. The proposed work will develop a method to trap a single sperm and measure its DNA integrity without hurting the sperm. A good sperm can then be selected to use to fertilise the egg. The technique developed should greatly reduce the risk of abnormalities in the children conceived by sperm injection. It may also increase the success rates for assisted fertilisation.We propose to combine two methods which use laser light: optical tweezers and Raman spectroscopy. If a beam of laser light is focused very tightly it can create enough force to hold a very small object - this is called optical trapping or optical tweezers. The sperm which may be trying to swim away will be held where we want it by optical trapping. Now we have trapped our very small and wriggling cell we have to characterise its DNA. This will be done by using a different colour of laser to vibrate the molecules of the cell. We can then look at how the vibrations affect the light. By using powerful statistical analysis we can build up knowledge of how damage DNA vibrates compared to good DNA.The work will involve a lot of optical design to create the instrument needed to do this work. We will then have to prove that our lasers themselves are not causing any additional damage to, the sperm. Tweezers and Raman have both been used before on cells without affecting them but we need to be absolutely sure that this is the case for sperm too. Next we'll build statistical models by taking healthy sperm and producing a known level of damage in them with chemicals and teaching our Raman software what that sperm 'looks' like. Finally, we'll take sperm from infertile men which have been sorted into different degrees of healthiness and we'll see if our instrument can tell the difference between them.There is a good chance that this instrument will be able to be used in laboratories around the world which are treating people with infertility or doing research into reproduction.