Novel particulate spin probe for targeted determination of oxygen in cells and tissues.
The synthesis and characterization of a new lithium octa-n-butoxy-substituted naphthalocyanine radical probe (LiNc-BuO) and its use in the determination of concentration of oxygen (oximetry) by electron paramagnetic resonance (EPR) spectroscopy are reported. The probe is synthesized as a needle-shaped microcrystalline particulate. The particulate shows a single-line EPR spectrum that is highly exchange-narrowed with a line-width of 210 mG. The EPR line-width is sensitive to molecular oxygen showing a linear relationship between the line-width and concentration of oxygen (pO(2)) with a sensitivity of 8.5 mG/mmHg. We studied a variety of physicochemical and biological properties of LiNc-BuO particulates to evaluate the suitability of the probe for in vivo oximetry. The probe is unaffected by biological oxidoreductants, stable in tissues for several months, and can be successfully internalized in cells. We used this probe to monitor changes in concentration of oxygen in the normal muscle and RIF-1 tumor tissue of mice as a function of tumor growth. The data showed a rapid decrease in the tumor pO(2) with increase of tumor volume. Human arterial smooth muscle cells, upon internalization of the LiNc-BuO probe, showed a marked oxygen gradient across the cell membrane. In summary, the newly synthesized octa-n-butoxy derivative of lithium naphthalocyanine has unique properties that are useful for determining oxygen concentration in chemical and biological systems by EPR spectroscopy and also for magnetic tagging of cells.
Center for Biomedical EPR Spectroscopy and Imaging, Department of Internal Medicine, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.
Ramasamy P
RP
Pandian
Narasimham L
NL
Parinandi
Govindasamy
G
Ilangovan
Jay L
JL
Zweier
Periannan
P
Kuppusamy
D000818:Animals; D045744:Cell Line, Tumor; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D005354:Fibrosarcoma / Q000378:metabolism* / Q000473:pathology; D005720:Gamma Rays; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008809:Mice, Inbred C3H; D015394:Molecular Structure; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis* / Q000737:chemistry; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry; D013113:Spin Labels; D013696:Temperature; D013997:Time Factors
D011166:Porphyrins; D013113:Spin Labels; C487013:lithium octa-n-butoxynaphthalocyanine; D010100:Oxygen