Mapping Drugs In Human Tissue

Tracking a drug’s destination in human tissue is now possible thanks to mass spectrometry imaging (Anal. Chem., DOI: 10.1021/ac2014349).

Scientists want to track drugs to find out whether they reach their intended targets in specific tissues. Doctors also think such mapping could help them tailor medicine to their patients. Traditional imaging techniques require adding a chemical label to the drug. However, these labels can change the drug’s behavior.

Researchers led by György Marko-Varga from Lund University, in Sweden, wanted to develop a label-free method. So they harnessed matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging to map the fate of an inhaled drug in tissue biopsies from five patients’ lungs.

The patients, who were long-time smokers, reported improved breathing after inhaling ipratropium, a common drug that opens airways in the lungs by binding to receptors in smooth muscle tissue. Researchers analyzed 3,000 0.01-mm2 spots on each tissue sample to create an image showing the drug’s spatial distribution in the tissue. Their maps found that the drug had reached smooth muscle tissue in four of the patients.

The team had previously tested its technique on the tissues of rats given drug doses 100 times greater than those used in this study (Plos One, DOI: 10.1371/journal.pone.0011411). In the two years since then, the team improved the technique’s sensitivity so that they can image therapeutic doses in humans, says Thomas Fehniger, from Tallin University of Technology, in Estonia, who is first author of the study. The technique, he says, could help doctors understand which tissues a drug targets so that they can choose the right drug for each patient’s condition.