19 July 2016

It’s that time of year. Sleeves are rolled up, dresses are out, the office is quiet and it’s actually sunny outside. For the next few weeks, Britain has been promised good weather and here at Aptamer Group, the lab has reached a peak of 28oC! This got us thinking – how well will our aptamers perform under the heat?

Most of us are aware that DNA is stable, given the fact we can unearth ancient DNA from dinosaurs and insects fossilised in amber. But how well does that translate through to aptamers? Traditionally, affinity reagents are suspended in an aqueous buffer and require cold storage – either 4oC or -20oC to stop bacterial growth and degradation over time. But what about aptamers?

Aptamers are simple single-stranded oligonucleotide chains that exhibit excellent stability under extreme heat conditions. In our accelerated stability study, we labelled our aptamers with a fluorophore to observe degradation over time and imaged using a standard fluorimeter. In our experience, aptamers maintain their function for over 4 days and will preserve their integratory for substantial amount of time, even at temperatures such as 90oC. Aptamers can be stored indefinitely at any temperature if they are lyophilised and rehydrated upon use. We wanted to make sure that the aptamers were still functional and saw minimal variability between aptamers used before and after heat treatment.

But what if the buffer was a little trickier than simple cell culture media? Many buffers contain specialist enzymes (nucleases) which can digest aptamers.  Is it possible for aptamers to maintain stability in the presence of nucleases? Incorporation of modified nucleotides, including 2’F RNA and phosphorothioate modified nucleotides prevents recognition by many nucleases present in plasma, allowing the aptamer to remain functional and exert its’ effect on the system.

So, in conclusion – aptamers perform well under heat! Using natural nucleotides, aptamers are able to withstand a range of temperatures and conditions that other affinity reagents, including antibodies, cannot. Moreover, even in the presence of complex assay matrices, aptamer stability is not altered significantly meaning that they remain high affinity, high specificity tools.