The study, published today in Nature Nanotechnology and funded by BBSRC, Leverhulme Trust and UCL Chemistry, shows how DNA can be used to build stable and predictable pores that have a defined shape and charge to control which molecules can pass through the pore and when.
Lead author, Dr Stefan Howorka (UCL Chemistry), said: “Natural biological pores made of proteins are essential for transporting cargo into and out of biological cells but they are hard to design from scratch. DNA offers a whole new strategy for constructing highly specific synthetic pores that we can open and close on demand. We’ve engineered our pores to act like doors – the door unlocks only when provided with the right key. By building these pores into drug carriers, we think it will allow for much more precise targeting of therapeutics.”
Many therapeutics including anti-cancer drugs can be ferried around the body in tiny carriers called vesicles which are targeted to different tissues using biological markers. Previously, releasing the drugs from inside the vesicles was triggered with temperature-induced leaky vesicle walls or with inserted peptide channels, which are less rigid and predictable than DNA.
Using DNA building blocks, the team designed pores with pre-determined structures and defined properties which were precisely anchored into the walls – or membranes – of vesicles.
“Our pores take the shape of an open barrel made of six DNA staves. We designed a molecular gate to close off one entrance but then re-open the channel when a specific molecule binds. Anchors with high membrane affinity were attached to tether the water-soluble pores into the oily membrane,” said first author, Dr Jonathan Burns (UCL Chemistry).
Using electrophysiology techniques, the researchers verified that the pore vertically spanned the surface of the membrane and was stable with an internal width of 2 nm, which is an appropriate size for small drugs molecules to fit through.
The gate’s lock and release mechanism was then tested with electrophysiology techniques as well as with fluorophores, which are of equivalent size to small molecules. As the DNA pore had a net negative charge, fluorophores with a net negative charge moved through with more ease than those with a net positive charge, showing selectivity for which cargo could exit. Removing the lock with a matching key increased of traffic 140-fold compared to a mismatched key.
Co-author Astrid Seifert who works with Dr Niels Fertig at Nanion Technologies, said: “We were able to precisely analyse the performance of each of the pores we created. We first inserted pores in membranes and then tested the biophysical response of each channel using advanced microchips. We’ve not only developed a new way to design highly specific pores but also an automated method to test their properties in situ, which will be important for testing pores being used for targeted drug delivery in the future.”
The researchers plan on testing the synthetic pores in a variety of scenarios including the release of anti-cancer drugs to cells and the development of pores that release pharmaceutically active biomolecules.
Dr Howorka added: “Our approach is a big step forward in building and using synthetic biological structures and promises a new era in pore design and synthetic biology. We have demonstrated such precise control over the behaviour of the pore, both in terms of selectivity and in terms of responsiveness that we believe that the method paves the way for a wide range of applications from drug delivery to nanosensing.”
Notes to editors
For a copy of the paper or to speak to the researchers, please contact Dr Rebecca Caygill in the UCL press office, tel: +44 20 3108 3846, or email: firstname.lastname@example.org.
Jonathan R. Burns, Astrid Seifert, Niels Fertig, Stefan Howorka, ‘A biomimetic DNA-made channel for the ligand-controlled and selective transport of small-molecule cargo through a biological membrane’ is due to be published in Nature Nanotechnology on 11 January 2016, 4pm London time.
The DOI for the above paper will be 10.1038/nnano.2015.279. Once the paper is published electronically, the DOI can be used to retrieve the abstract and full text from the Nature website by adding it to the following url: http://dx.doi.org/.
About UCL (University College London)
UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world’s top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 35,000 students from 150 countries and over 11,000 staff. Our annual income is more than £1Bn. For more information follow: www.ucl.ac.uk
About Nanion Technologies
Nanion Technologies is a one-stop-shop for ion channel drug discovery and screening technologies as well as sophisticated research instrumentation. Nanion was founded in 2002 as a spin-off from the Center for Nanoscience (CeNS) of the University of Munich. Nanion’s team has developed and successfully established four generations of automated patch clamp instruments for sophisticated and high throughput applications in ion channel research and drug discovery. Product lines for cardiotoxicity screening, parallel bilayer recordings, and parallel membrane transporter protein recordings have also been successfully introduced. Since 2014, Nanion distributes Axion’s multi-electrode array (MEA) systems in Europe and China. In the published study Nanions Orbit 16 was used, a high quality platform for automated formation and recordings from 16 parallel bilayers. It facilitates efficient lipid bilayer recordings of ion channels or nanopores and their effectors. The Orbit uses the Micro Electrode Cavity Array (MECA) chip substrates, which are developed and provided by Ionera Technologies at: www.ionera.de.For more information visit: www.nanion.de
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