Applied Physics Seminar: Nanophotonic Medicine: From Deep In-vivo Optical Diagnostics of Tumors to Photodynamic Therapy of Heart Diseas

In recent years, our use of nanoparticles has advanced from its original utilization of studying cells under the microscope to application in animal models, for cancer diagnostics and therapy, as well as for treating the number one killer, heart disease. Here we report on in vivo (live animal) photon based diagnostics as well as therapy for these diseases. It is well known that the chemistry of the extracellular tumor environment differs from that of healthy organs in two major respects: oxygen depletion and acidosis, i.e. lower pH. These alterations may affect the efficacy of therapy, whether radiation therapy, chemomotherapy ot photodynamic therapy. It would thus be advantageous for the physician to have this information, so as to achieve precision cancer therapy. We have shown that nanoparticle based photo-acoustic imaging can quantify both tissue oxygen as well as pH, and note that this photon and ultrasound based imaging technique is both non-invasive and relatively inexpensive. Regarding photon based therapy, photodynamic therapy (PDT) has been used clinically for skin cancers. Our previous animal model tests have also indicated its potential use for internal organs and even brain cancer. We now show that PDT can also serve to fix arrhythmia ( irregular heart beat), possibly the most critical aspect in heart disease. Starting with cell microscopy tests, continuing with rodent models and culminating with large animal models (sheep), whose heart resembles the human heart, we have shown that our cell selective photoablation has major advances compared to the traditional, chemical and surgical, modes of treatment. All it takes is 10 sec of a weak cw red laser illumination, preceded by a single shot to the tail. The new, minimally invasive, cardiologic approach is based on the use of a novel design of photoactive nanoparticles. Notably, the latter have to be of a much smaller size (below 10 nm) compared to the photodynamic nanoparticles used for the treatment of cancer (order of 100 nm), and targeted at electrically hyperactive heart cells, rather than tumor cells.