Layers of inorganic clay could smuggle helpful DNA into cells needing gene therapy, Korean researchers claim. In laboratory tests, they showed that the clay 'vectors' could transport therapeutic DNA strands into cancerous cells and restrict their growth.

Gene therapy delivers helpful genes or repaired DNA sequences to cells. Viruses that stick to cells and inject DNA are often used, but it is difficult to stop them triggering the body's immune response -- sometimes with tragic consequences. 18-year-old gene therapy patient Jesse Gelsinger died last year during a trial. There are alternative, non-viral vectors based on fatty globules, but these tend not to work as well.

Now, Jin-Ho Choy and his colleagues at Seoul National University propose a totally new type of non-viral vector. The researchers layer a material based on magnesium and aluminium hydroxides into clays called 'layered double hydroxides'. Between the layers are negatively charged ions; these can be replaced with negatively charged molecules like DNA.

Many cells repel negatively charged molecules with their similarly charged cell membranes. The clay layers shield DNA from these opposing forces, helping it to slip through. Once inside the cell, the outer clay layers dissolve to expose the DNA. The team reports its results in the journal Angewandte Chemie International Edition1.

The new technique represents a "paradigm shift in thinking for non-viral vectors," says David Curiel, director of the gene therapy program at the University of Alabama at Birmingham, USA.

Choy's group showcased the clay vectors in two experiments. In the first, they sneaked fluorescent molecules into cells. In the second, they clay-wrapped a DNA sequence designed to impede a specific gene of leukaemia cells grown in the laboratory. The treatment reduced the growth of the cancerous cells by 65 per cent.

The dissolved clay is not poisonous, say Choy and his co-workers; they also suggest their new vectors could carry and deliver medicines to precise locations.

Still, Curiel is cautious: "I can name you fifty things that you can mix with DNA to enhance gene transfer in vitro [in cells outside the body]". "People will only take note if the new technique works when used in living animals," he says.