<title>Optical imaging of green fluorescent protein markers for tracking vascular gene expression: a feasibility study in human tissue-like phantoms</title>

Abstract

Vascular gene therapy is an exciting approach to the treatment of cardiovascular diseases. However, to date, there are no imaging modalities available for non-invasive detection of vascular gene expression. We have developed an optical imaging method to track vascular gene expression by detecting fluorescent signals emitted from arterial walls following gene transfer. To investigate the feasibility of this new technique, we performed experiments on a set of human tissue-like phantoms using a common biological marker in gene therapy, the green fluorescent protein (GFP). The phantoms were constructed to mimic the arterial geometry beneath a tissue layer. Human smooth muscle cells transfected with GFP were embedded in a capillary tube in the phantom. Monte Carlo modeling of the phantom experiment was performed to optimize the performance of the optical imaging system. We compared the fluence rates among three types of light beams, including ring beam, Gaussian beam, and flat beam. The results showed that our optical imaging system was able to detect fluorescent signals up to 5-mm depth in the phantom, and that flat beam geometry would produce the optimum fluorescence remittance. This study provides valuable insights for improvements to the optical imaging system and refinement of the new technique to non-invasively detect/track vascular gene expression.