Dr. Malcolm Forbes, University of North Carolina-Chapel Hill

October 8, 2014
1:30 – 2:30 pm
C-121

*Pizza to be served at 3pm

“Photodynamic Therapy, Toils and Troubles: Problems Solved With Tiny Bubbles”

Abstract: Photodynamic therapy (PDT) uses visible light, a sensitizer such as a porphyrin, and oxygen gas to create singlet oxygen (1O2), a reactive oxygen species that can kill cancer cells. Historically, PDT has remained a non-invasive treatment, using red light and ambient oxygen after intravenous administration of the sensitizer. Here we describe an invasive methodology for PDT that uses highly efficient blue light coupled with localized microbubble-based delivery of sensitizer and oxygen. Lipid- based air bubbles with stabilizers are administered via a teflon or stainless steel catheter containing a concentrically placed fiber-optic cable. Ultrasound transducers are used to acoustically image the catheter and bubbles. Ultrasound can also be used to manipulate the bubbles (moving or popping). The kinetics and topology of singlet oxygen production can be studied quantitatively by reacting secondary amines with the 1O2 to produce stable nitroxide radicals, detectable at μM concentrations by electron paramagnetic resonance (EPR) spectroscopy. The sensitivity of nitroxide EPR spectra to local order in heterogeneous structures such as bubbles, vesicles, and micelles will also be presented and discussed.