Biodistribution studies of nanoparticles using fluorescence imaging: a qualitative or quantitative method?
OBJECTIVE
The biodistribution of Lipid/Calcium/Phosphate (LCP) nanoparticles (NPs) in tumor-bearing mice was investigated using fluorescence imaging. A quantitative validation of this method was done by (3)H and (111)In labeling of the nanoparticles.


METHODS
The biodistribution of LCP NPs containing oligonucleotides was investigated using three different probes: Texas-Red labeled oligonucleotides, (3)H-labeled oligonucleotides, and (111)In-labled calcium phosphate.


RESULTS
A discrepancy was found between the radioactivity and the fluorescence signals. Signals from (3)H and (111)In exhibited very similar distribution patterns, suggesting that liver and spleen were the major accumulation sites. However, fluorescence imaging indicated that tumor accumulation was predominant. We further confirmed that the fluorescence signals in both liver and spleen were greatly attenuated compared with those in the tumor due to the intrinsic tissue absorption and scattering. Near-infrared (NIR) dye Cy5.5 also suffered from the same problem, in that the quantitative data from whole organs was dramatically affected by absorption and scattering properties of the tissue.


CONCLUSIONS
Careful attention must be paid to the quantification and interpretation of fluorescence imaging measurements when comparing different tissues.
Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, 1315 Kerr Hall CB# 7571, Chapel Hill, North Carolina 27599-7571, USA.
Yang
Y
Liu
Yu-Cheng
YC
Tseng
Leaf
L
Huang
D000818:Animals; D002130:Calcium Phosphates; D005453:Fluorescence; D008055:Lipids; D008168:Lung / Q000473:pathology; D008175:Lung Neoplasms / Q000175:diagnosis*; D051379:Mice; D008819:Mice, Nude; D053758:Nanoparticles / Q000737:chemistry; D009841:Oligonucleotides / Q000737:chemistry; D061848:Optical Imaging / Q000379:methods; D014018:Tissue Distribution; D014966:Xanthenes / Q000737:chemistry
D002130:Calcium Phosphates; D008055:Lipids; D009841:Oligonucleotides; D014966:Xanthenes; C034657:Texas red