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.