Photoacoustic molecular imaging of ferritin as a reporter gene

S. Ha; A. Carson; K. Kim

doi:10.1117/12.906802

23 February 2012 Photoacoustic molecular imaging of ferritin as a reporter gene

S. Ha, A. Carson, K. Kim

Proceedings Volume 8223, Photons Plus Ultrasound: Imaging and Sensing 2012; 82232N (2012) https://doi.org/10.1117/12.906802
Event: SPIE BiOS, 2012, San Francisco, California, United States

Abstract

Spectral analysis of photoacoustic (PA) molecular imaging (PMI) of ferritin expressed in human melanoma cells (SK-24) was performed in vitro. Ferritin is a ubiquitously expressed protein which stores iron that can be detected by PA imaging, allowing ferritin to act as a reporter gene. To over-express ferritin, SK-24 cells were co-transfected with plasmid expressing Heavy chain ferritin (H-FT) and plasmid expressing enhanced green fluorescent protein (pEGFP-C1) using Lipofectamine^TM 2000. Non-transfected SK-24 cells served as a negative control. Fluorescent imaging of EGFP confirmed transfection and transgene expression in co-transfected cells. To detect iron accumulation in SK-24 cells, a focused high frequency ultrasonic transducer (60 MHz, f/1.5), synchronized to a pulsed laser (<20mJ/cm²), was used to scan the PA signal from 680 nm to 950 nm (in 10 nm increments) from the surface of the 6-well culturing plate. PA signal intensity from H-FT transfected SK-24 cells was not different from that of non-transfected SK-24 cells at wavelengths less than 770 nm, but was over 4 dB higher than non-transfected SK-24 cells at 850 ~ 950 nm. Fluorescent microscopy indicates significant accumulation of ferritin in H-FT transfected SK-24 cells, with little ferritin expression in non-transfected SK-24 cells. The PA spectral analysis clearly differentiates transfected SK-24 cells from nontransfected SK-24 cells with significantly increased iron signal at 850 ~ 950 nm, and these increased signals were associated with transfection of H-FT plasmid. As such, the feasibility of ferritin as a reporter gene for PMI has been demonstrated in vitro. The use of ferritin as a reporter gene represents a new concept for PA imaging, and may provide various opportunities for molecular imaging and basic science research.

Citation Download Citation

S. Ha, A. Carson, and K. Kim "Photoacoustic molecular imaging of ferritin as a reporter gene", Proc. SPIE 8223, Photons Plus Ultrasound: Imaging and Sensing 2012, 82232N (23 February 2012); https://doi.org/10.1117/12.906802

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