Real-time confocal Raman imaging of a drug delivery system on cardiac leads

Drug delivery systems incorporated onto the end of cardiac leads are used to reduce inflammation and fibrosis at the lead-tissue interface and enable optimal lead performance. In this research, confocal Raman microscopy was used to capture chemical images of the drug delivery system on pacemaker leads in different elution media in real-time. Raman images in ambient air showed that drug was dispersed in the polymer matrix as discrete particles with size ranging from 1 to 3 microm. Upon immersion into an aggressive elution medium, drug near the surface dissolved immediately and solvent started to penetrate into the polymer matrix through channels from which drug was eluted. The drug depletion depth was a function of time, which was consistent with the drug release profiles obtained by HPLC. Comparing the drug elution in aggressive solvent and biorelevant solvent, a mechanism of drug release is proposed.