~7Be-recoil radiolabelling of industrially manufactured silica nanoparticles

摘要

Radiolabelling of industriallymanufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industriallymanufactured species. Inmany cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties.We describe here a process whereby in such cases nanoparticles can be labelled with ~7Be, which exhibits a physical half-life of 53.29 days and emits c-rays of 478 keV energy, and is suitable formost radiotracer studies. ~7Be is produced via the proton-induced nuclear reaction ~7Li(p,n)~7Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of ~7Be atoms gives them a range that allows the ~7Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered fromthe mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO_2 nanoparticles. The process can be controlled in such a way that no alterations of the ~7Belabelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotronswithmaximumproton energies of 17-18 MeV that are available in most medical research centres could be used for this purpose.