Chinese scientists have developed fluorescent drug delivery vehicles that can be used to monitor drug release.

DNA hydrogels are gel-like networks of DNA chains that are insoluble in water but can absorb liquids like a sponge. Because they are biocompatible, they have been widely studied as drug delivery vehicles. Fluorescent hydrogels are useful because scientists can monitor the fluorescence during in vitro experiments to determine how much drug the hydrogel is likely to release when it is used in humans. Until now, the only way to make them fluoresce has been to stain them with DNA-specific fluorescent dyes. Shu Wang and colleagues at the Beijing National Laboratory for Molecular Science, China, have made the first examples of inherently fluorescent DNA hydrogels.

Wang made a DNA-conjugated polymer composite hydrogel by joining together the polymer's building blocks on a DNA template. The conjugated polymer's delocalised electronic structure caused the hydrogel to fluoresce. Wang loaded the hydrogel with a drug designed to combat high blood pressure. He showed that the drug quenched the hydrogel's fluorescence but after the hydrogel released the drug, the fluorescence returned. Wang also found that by changing the pH of the medium surrounding the hydrogel, he could control the release of the drug and so the hydrogel's fluorescence.

'It is amazing that these DNA-conjugated polymer hydrogels could be exploited to monitor drug release driven by media pH,' says Wang. 'The challenges include working out how to use these new hydrogels to monitor drug delivery to cells and demonstrating that they actually improve our ability to monitor drug delivery.'

Vikki Chapman

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