Researchers have developed ultrathin, nanoscale films composed of DNA and water-soluble polymers that allow controlled release of DNA from surfaces to target treatment in gene therapy.
Prof. David Lynn and his colleagues at the University of Wisconsin School of Medicine and Public Health created the films which can be used to coat implantable medical devices, offering a novel way to route useful genes to exactly where they could do the most good.
When placed in or near a body tissue, the films are designed to degrade and release the DNA. Large strands of DNA cannot normally penetrate cells, so
The research team creates the films one layer at a time using a dip-coating method, dunking first in one solution, then another. The individual layers are so thin it would take roughly 10,000 of them to equal the thickness of a single sheet of paper.
The researchers alternate layers of DNA with layers of a polymer that is stable when dry but that degrades when exposed to water. Because the polymers carry a positive electric charge that is attractive to DNA, each polymer layer also ‘primes’ the surface to accept the next layer of DNA. While electrostatic forces between the layers keep the film stable in dry, room-temperature conditions, the polymers break down easily in a wet biological environment — like the inside of a patient’s body.
Using the layering method, the team can control the amount of DNA by adding more layers, or can even layer multiple ingredients in a specific order. Tweaking the polymer structure slightly can change how quickly the films erode and thus how long cells are exposed to the gene therapy.
The films start to break down when they come into contact with water. ‘The architecture of the film determines the manner in which [DNA] is released,’
More recent designs erode like a bar of soap, with the effect that outer layers are released before inner layers. By placing one gene in the outer layers and another in the inner layers, they can deliver different products sequentially. ‘This kind of control is extremely difficult to achieve using conventional materials,’
In addition to delivering DNA from stents,