Abstract

Stem cell therapies promise to allow the blind to see, the lame to walk and those enslaved to thrice weekly dialysis to be free. However, they have not yet fulfilled their potential, partly because we don’t know where stem cells go and what they do deep inside organs of real living humans. We recently identified a general limit of medical imaging which encapsulates the challenge; current technologies do not allow visualization of objects more than 200 times smaller than the depth. For example, cellular details more than c. 1 mm into typical human tissues like the skin cannot be imaged by any technology. The TOMI lab won a €6M EU H2020 grant to develop technologies to see deeper and smaller and with greater sensitivity than ever before. We go beyond the depth/resolution limit by demonstrating nanosensitive OCT to follow structural changes in cells and tissues at the nanoscale. Using a unique star-shaped gold nanoparticle made in Galway, which resonates in the low scattering and absorption window close to 1100 nm, allows us to see deeper and with greater sensitivity than ever before. The combination of long wavelength, tip field enhancement and energy transfer make this particle the brightest ever made. We combine this with photoacoustic imaging, so that we can use diffuse light to illuminate the tissue and ultrasound which is not scattered, to see where it was absorbed. The particle is magnetized by SPION conjugation so that is also visible in MRI. We will demonstrate this enhanced imaging in Cambridge during stem cell therapy for osteoarthritis of the knee. This paper will report the efforts to optimize nanostar guided optoacoustic imaging for stem cell tracking in small and large pre-clinical models.

© 2019 SPIE/OSA