Cuprous oxide nanospheres as probes for light scattering imaging analysis of live cells and for conformation identification of proteins

A facile solution-phase synthesis route of highly uniform Cu2O nanospheres (Cu2O NPs) with the size of 57.7 ± 4.7 nm was developed, and then the nanoparticles were applied to live cell imaging under a common dark-field microscope. Starting from copper(II) salts, the synthesis of Cu2O NPs was made in the presence of cetyltrimethylammonium bromide (CTAB) by reducing the copper(II) with sodium borohydride (NaBH4) in aqueous medium and by aging process in the air. Monitoring of morphology evolution process of Cu2O NPs with scanning electron microscopy (SEM) and measuring of the UV–visible spectra showed that the synthesis of Cu2O NPs follows the reduction–oxidation coupled process of Cu2+ into Cu0 species at first and then the resulted Cu0 species into Cu2O NPs in the air. Light scattering (LS) features have been measured with a common spectrofluorometer and a common dark-field microscope, and it was found that the as-prepared Cu2O NPs display strong blue scattering light and can be applied for cell imaging. If incubated with human bone marrow neuroblastoma, transferrin-conjugated Cu2O NPs can get into the cells and show strong pure blue light in cytoplasm. Further investigations showed that the Cu2O NPs could be applied for probes for conformation of proteins.