Research team moves towards on-site DNA fingerprinting

Crime-scene investigators could soon have the ability to perform DNA fingerprinting on site without the need for lengthy post-analysis in a lab.

Currently, forensic swab samples obtained at a crime scene are sent off for analysis where a specific part of the sequence, containing blocks of repeating elements that vary between individuals, are amplified and then read out.

This can take days and, in some cases, errors can be introduced or insufficient signals obtained to get a definitive match.

Now, a team from University College London and Southampton University is taking a different approach by using nanopores, which naturally occur in cell membranes coupled to an electrical circuit.

The idea would be to feed a string of DNA through the pore, which would change the electrical current according to which of the four letters of the DNA code — A, C, G or T — went through.

‘If you embed these nanopores into an artificial membrane you can apply a voltage and see a current flowing through these pores. When something enters those pores it blocks them and you see a drop in the current — but to translate that into a DNA sequence is the difficult part; a lot of people are working on it now,’ said project co-investigator Dr Eugen Stulz of Southampton University.

The team has recently performed some preliminary studies where it was able to thread a large piece of DNA directionally through the pore — an important step if the output sequence is to be coherent. Stulz also said that the team’s method should be much more sensitive than existing approaches.

‘The idea would be that we don’t need to amplify, because ultimately we would like to go down to single-molecule sequencing, so one single DNA molecule would be enough — that would really be the holy grail,’ Stulz said.

He envisages a device that could get a read-out from a crime scene in minutes, which could then be checked against a database on a laptop, all in the field.