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In this study, we report, for the first time, the synthesis of two original nanosystems, based on gold Au(III) and copper Cu(II): simple gold-copper nanoparticles (Cu 0 AuNPs) and enriched monopicolinate cyclam (L1)-Cu(II)-Au(III)-complex (L1@Cu 2+ AuNPs). The two nanomaterials differ substantially by the chelation or not of the Cu(II) ions during the NPs synthesis process. The two hybrid nanoparticles (Cu 0 AuNPs; L1@Cu 2+ AuNPs) were deeply studied from the chemical and physical point of view, using many different analytical techniques such as Raman and UV-vis spectroscopy, electron transmission microscopy, and dynamic light scattering. Both nanosystems show morphological and good chemical stability at pH 4 values and in physiological conditions during 98 h. Undifferentiated and neural differentiated murine embryonic stem cells were used as a model system for in vitro experiments to reveal the effects of NPs on these cells. The comparative study between Cu 0 AuNPs and L1@Cu 2+ AuNPs highlights that copper chelated in its +2 oxidation state in the NPs is more functional for biological application., Competing Interests: The authors declare no competing financial interest.

A colorimetric immunosensor based on local surface plasmon resonance by gold nanoparticles is presented, and its application for the detection of human immunoglobulin G (IgG) is demonstrated. The color change of the colloidal solution is produced by nanoparticle aggregation, a process that can be tuned by the presence of the analyte once the nanoparticles are functionalized. In comparison to common functionalization techniques, the procedure described here is simpler, low-cost, and effective in binding antibodies upright on the gold surface. The dose-response curve is similar to that resulting in typical immunoassay platforms and is satisfactorily described by the proposed theoretical model. Human IgG at concentration levels of few hundreds of nanograms per milliliter can be detected by eyes within a few minutes, thereby making the colorimetric immunosensor proposed here a powerful tool in several areas, with urine test in medical diagnostics being the most immediate., Competing Interests: The authors declare no competing financial interest.