Multiphoton induced fluorescence and second harmonic imaging of drug-eluted arterial walls for non-invasive photo-polymerizable stents (Conference Presentation)

We developed a spectrally-resolved multi-photon imaging system, based on a closed loop piezoelectric sample scanning stage, a transmission grating and an EMCCD. The method allows detailed analysis of the spectrally-resolved signals, including deconvolution of the resulting emission peaks, and precise differentiation of the resulting signals. The system also makes available the possibility of using point spread function analyses, such as pixel reassignment, Airy scan and full three-dimensional, spectral imaging. We present multi-photon induced fluorescence, second harmonic and fluorescence lifetime imaging analysis supporting the development of non-invasive photo-polymerizable scaffolds for treatment of peripheral artery disease. Currently, the technology, developed by Alumend, LLC, is undergoing clinical trials and is licensed by Alucent Medical. In this work we report a comparison of the second harmonic generation and two photon induced fluorescence imaging in drug-infused arteries, and compare these to fluorescence lifetime images obtained using our commercial (Picoquant) fluorescence lifetime imaging system. Primary signals from the endogenous fluorescence from the drug and the second harmonic generation, prevalent in collagen, are compared. Of particular interest, we observe the photo-chemical modification of the drug fluorescence emission energy and lifetime in the adventitia, composed primarily of collagen. The drug aids in cross-linking the compressed collagen fibrils in the arterial wall during the light activation step, which leads to formation of the stent.