In our in vitro model, MNPs are taken up by granulocytes through phagocytosis, whereas previously described methods were based on the use of a chelating agent that permit Cu to cross the cell membrane. Moreover, the (64)Cu-engulfed granulocytes showed a high stability of up to 80% of retained radioactivity after 24 h of incubation.

Human b-defensin-3 (HBD-3) is an antimicrobial peptide with bactericidal effects on many gram-positive and gram-negative bacteria and some yeast species and, if radiolabeled, might be used to distinguish bacterial infection from sterile inflammation. The goals of the present study were to develop methods for radiolabeling HBD-3 with 99m Tc and to perform preliminary investigations on 99m Tc-labeled HBD-3 as a means to evaluate induced infection in an animal model. To this purpose, Staphylococcus aureus-induced infection was used to evaluate the capability of 99m Tc-HBD-3 to distinguish infection from aseptic inflammation in rats. Methods: Twenty to 40 mg of recombinant HBD-3 were labeled with 99m Tc 1 hexa-coordinated with 3 molecules of CO and H 2 O and separated by a column from free 99m Tc. 99m Tc-HBD-3 was added to cultures of a bacterial suspension of S. aureus and Escherichia coli to evaluate in vitro antibacterial activity. A bacterial suspension of S. aureus and a carrageenan solution were used to induce infection and sterile inflammation, respectively, in opposite thighs of 9 adult rats. Three separate experiments were performed on groups of 3 rats each. The animals received different doses of 99m Tc-HBD-3 injected through a cannula into the jugular vein. After sacrifice of the animals, tissue samples were obtained from sites of infection, inflammation, and control muscle (left foreleg) at 1, 3, and 5 h after 99m Tc-HBD-3 administration. Tissue samples were weighed and then counted in a well-counter. Simultaneously, 1 mL of a standard solution of 99m Tc-HBD-3 corresponding to each administered dose was counted. Results: 99m Tc-HBD-3 retained antibacterial activity. Radioactivity in tissue samples from the infected sites was significantly higher than that in samples of either induced inflammation or normal control muscle (ratio, ;3:1) at 3 and 5 h after injection, whereas similar radioactivity counts were observed for tissue samples from aseptic inflammation sites and normal control muscle. Conclusion: In this investigation, 99m Tc-HBD-3 retained antibacterial activity and successfully distinguished infection from aseptic inflammation in adult rats.

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IGF-binding proteins (IGFBPs) and their proteases regulate IGFs bioavailability in multiple tissues. Pregnancy-associated plasma protein A (PAPP-A) is a protease acting by cleaving IGFBP2, 4, and 5, regulating local bioavailability of IGFs. We have previously shown that IGFs and IGFBPs are produced by human adult cardiac progenitor cells (haCPCs) and that IGF-1 exerts paracrine therapeutic effects in cardiac cell therapy with CPCs. Using immunofluorescence and enzyme immunoassays, we firstly report that PAPP-A is produced and secreted in surprisingly high amounts by haCPCs. In particular, the homodimeric, enzymatically active, PAPP-A is secreted in relevant concentrations in haCPC-conditioned media, while the enzymatically inactive PAPPA/proMBP complex is not detectable in the same media. Furthermore, we show that both homodimeric PAPP-A and proMBP can be detected as cell associated, suggesting that the previously described complex formation at the cell surface does not occur easily, thus positively affecting IGF signalling. Therefore, our results strongly support the importance of PAPP-A for the IGFs/IGFBPs/PAPP-A axis in CPCs biology.

Among the most interesting applications of ferromagnetic nanoparticles (NPs) in medicine is the potential for localizing pharmacologically or radioactively tagged agents directly to selected tissues selected by an adjustable external magnetic field. This concept is demonstrated by the application external magnetic field on IV Tc-labeled aminosilane-coated iron oxide NPs in a rat model. In a model comparing a rat with a 0.3-T magnet over a hind paw versus a rat without a magnet, a static acquisition at 45 minutes showed that 27% of the administered radioactivity was in the area subtended by the magnet, whereas the liver displays a percentage of binding of 14% in the presence of the magnet and of 16% in the absence of an external magnetic field. These preliminary results suggest that the application of an external magnetic field may be a viable route for the development of methods for the confinement of magnetic NPs labeled with radioactive isotopes targeted for predetermined sites of the body.