99mTc-phytate as a diagnostic probe for assessing inflammatory reaction in malignant tumors

OBJECTIVEOnce administered intravenously, technetium-99m (Tc)-labeled phytate binds to calcium in the serum and behaves as a nanoparticle. On the basis of the high permeability of the tumor vasculature, Tc-phytate is expected to leak and accumulate specifically in inflammatory cells. The aim of this study was to evaluate the potential of Tc-phytate in assessing the degree of inflammation in Ehrlich solid tumors in mice. MATERIALS AND METHODSTc-phytate was prepared by adding pertechnetate to a solution containing phytic acid and stannous chloride. The blood half-life of this particle following intravenous injection was determined using blood samples from healthy animals, whereas its size was measured by photon correlation spectroscopy. Scintigraphic imaging and biodistribution studies were carried out in tumor-bearing mice at 30 min and 2 h after injection. RESULTSThe average size of the particles was in the range of 200 nm, suggesting that they are capable of passively passing through fenestrations in tumor vessels, which are 200–2000 nm in size. The blood half-life for Tc-phytate was found to be 2.1 min, a result that is in agreement with previous studies. Data from tumor-bearing mice showed high tumor uptake at 2 h after Tc-phytate administration. As a result, a high tumor-to-muscle ratio was achieved (T/M=25.9±7.54). CONCLUSIONThese findings indicate that Tc-sodium phytate has promising properties for identifying the type of tumor. This approach will have significant implications for characterizing tumor biology and treatment of malignant lesions.