<i>In vitro</i>photoacoustic sensing of calcium dynamics with arsenazo III

Abstract

Imaging of cellular electric potential via calcium-ion sensitive contrast agents is a useful tool, but current it lacks sufficient depth penetration. We explore contrast-enhanced photoacoustic (PA) imaging, using Arsenazo III dye, to visualize cardiac myocyte depolarization <i>in vitro</i>. Phantom results show strong linearity of PA signal with dye concentration (<i>R</i> ^<i>2</i> > 0.95), and agree spectrally with extinction measurements with varying calcium concentration. Cell studies indicate a significant (> 100-fold) increase in PA signal for dye-treated cells, as well as a 10-fold increase in peak-to-peak variation during a 30-second window. This suggests contrast-enhanced PA imaging may have sufficient sensitivity and specificity for depth-resolved visualization of tissue depolarization in real-time.