Light-controlled Magic Bullet

Targeting diseased tissue directly with the drug to teach it, the so-called magic bullet, came a step closer thanks to work by Senior Lecturer in Pharmaceutics Colin McCoy of Queen’s University Belfast and his colleagues. They have developed a new light-controlled drug-delivery system they claim could minimize side effects.

“This system translates the high degree of control we can exert on light to control over drug dosing, potentially at the level of a single drug molecule,” McCoy told Reactive Reports. The drug is released by the chemical system when light shines on it, but release is closed off in the dark. Administering the drug in this form would mean that it could be released only at the site of disease, by shining bright light only at that part of the patient’s body.

The team synthesized a range of compounds in which a light-sensitive molecule, 3,5-dimethoxybenzoin, is joined, or conjugated to one of the drug molecules, acetyl salicylic acid (aspirin), ibuprofen, or ketoprofen. In the dark these conjugates are stable but shine light of a wavelength of 365 nanometers onto them and a structural change in the 3,5-dimethoxybenzoin makes the conjugate fall apart, releasing the drug molecule. The researchers explain how incorporating the conjugates into a water-soluble hydrogel, comprising a hydrated copolymer of 2-(hydroxyethyl) methacrylate and methyl methacrylate, crosslinked with ethylene glycol dimethacrylate, then provides them with the means to administer the conjugate to a patient, perhaps via a bladder catheter or implant. 365 nm light then releases the drug once the doped-up hydrogel is in place.

The team has carried out successful laboratory tests with three common medications used to treat pain and inflammation—aspirin, ibuprofen, and ketoprofen. One potential use cited in the study would be in the treatment of urinary catheter infections, where the drug is held in the catheter, and is released when needed using a light. The system could be applied for other conditions using an implant under the skin for precisely controlled drug dosing, the researchers suggest.

J Am Chem Soc, 2007, 129, 9572-9573