In vivostudy of iron oxide-calcium phosphate composite nanoparticles for delivery to atherosclerosis.

Atherosclerosis is a macrophage-related inflammatory disease that remains a leading cause of death worldwide. Magnetic iron oxide (IO) nanocrystals are clinically used as magnetic resonance imaging contrast agents and their application as a detection agent for macrophages in arterial lesions has been studied extensively. We recently fabricated heparin-modified calcium phosphate (CaP) nanoparticles loaded with a large number of IO nanocrystals via coprecipitation from a supersaturated CaP solution supplemented with heparin and ferucarbotran (IO nanocrystals coated with carboxydextran). In this study, we further increased the content of IO nanocrystals in the heparin-modified IO-CaP composite nanoparticles by increasing the ferucarbotran concentration in the supersaturated CaP solution. The increase in nanoparticle IO content caused a decrease in particle diameter without impairing its dispersibility; the nanoparticles remained dispersed in water for up to 2 h due to electrostatic repulsion between particles due to the surface modification with heparin. The nanoparticles were more effectively taken up by murine RAW264.7 macrophages compared to free ferucarbotran without showing significant cytotoxicity. A preliminaryin vivostudy showed that the nanoparticles injected intravenously into mice delivered more IO nanocrystals to macrophage-rich carotid arterial lesions than free ferucarbotran. Our nanoparticles have potential as a delivery agent of IO nanocrystals to macrophages in arterial lesions.

Fabrication of gold-calcium phosphate composite nanoparticles through coprecipitation mediated by amino-terminated polyethylene glycol.

Calcium phosphate (CaP) nanoparticles immobilizing gold (Au) nanocrystals (Au-CaP composite nanoparticles) would be useful in diagnoses and/or treatments with Au nanocrystals. In this study, we achieved the rapid one-pot fabrication of such nanoparticles via coprecipitation in labile supersaturated CaP solutions by using appropriate Au sources, namely, Au nanocrystals coated with amino-terminated polyethylene glycol (PEG). In this process, amino groups at the PEG terminal played a crucial role in the coprecipitation with CaP through affinity interactions, and thus in the formation of Au-CaP composite nanoparticles; however, the molecular weight of the PEG chain was not a controlling factor in the coprecipitation. The important role of the functional groups at the PEG terminal was suggested by comparison with Au nanocrystals coated with carboxyl- and methoxy-terminated PEG, both of which barely coprecipitated with CaP and failed to form Au-CaP composite nanoparticles. Au nanocrystals coated with amino-terminated PEG were immobilized on the CaP nanoparticles, thereby regulating their size (∼140 nm in hydrodynamic diameter) and their dispersion in water. This coprecipitation process and the resulting Au-CaP composite nanoparticles have great potential in biomedical applications.

Facile one-pot fabrication of calcium phosphate-based composite nanoparticles as delivery and MRI contrast agents for macrophages.

We developed a facile one-pot fabrication process for magnetic iron oxide-calcium phosphate (IO-CaP) composite nanoparticles via coprecipitation in labile supersaturated CaP solutions containing IO nanocrystals. All the source solutions used were clinically approved for injection, including water and magnetic IO nanocrystals (ferucarbotran, used as a negative magnetic resonance imaging (MRI) contrast agent). This ensured that the resulting nanoparticles were pathogen- and endotoxin-free. The dispersants used were clinically approved heparin sodium (heparin) or adenosine triphosphate disodium hydrate (ATP), which were added to the IO-containing labile supersaturated CaP solutions. Both heparin and ATP coprecipitated with CaP and ferucarbotran to form heparin- and ATP-modified IO-CaP nanoparticles, respectively, with a hydrodynamic diameter of a few hundred nanometers. Both the resulting nanoparticles exhibited relatively large negative zeta potentials, caused by the negatively charged functional groups in heparin and ATP, which improved the particle dispersibility when compared to non-modified IO-CaP nanoparticles. The heparin-modified IO-CaP nanoparticles were effectively ingested by murine macrophages (RAW264.7) without showing significant cytotoxicity but barely ingested by non-phagocytotic human umbilical vein endothelial cells, indicating the potential of these nanoparticles for targeted delivery to macrophages. The heparin-modified IO-CaP nanoparticles exhibited a negative contrast enhancing ability for MRI. Our results show that IO-CaP nanoparticles have potential as delivery and MRI contrast agents for macrophages.