Quantum Dots: Proteomics characterization of the impact on biological systems

Over the past few years, Quantum Dots have been tested in most biotechnologicalapplications that use fluorescence, including DNA array technology, immunofluorescenceassays, cell and animal biology. Quantum Dots tend to be brighter than conventional dyes,because of the compounded effects of extinction coefficients that are an order of magnitudelarger than those of most dyes. Their main advantage resides in their resistance to bleachingover long periods of time (minutes to hours), allowing the acquisition of images that are crispand well contrasted. This increased photostability is especially useful for three-dimensional(3D) optical sectioning, where a major issue is bleaching of fluorophores during acquisition ofsuccessive z-sections, which compromises the correct reconstruction of 3D structures. Thelong-term stability and brightness of Quantum Dots make them ideal candidates also for liveanimal targeting and imaging. The vast majority of the papers published to date have shown norelevant effects on cells viability at the concentration used for imaging applications; higherconcentrations, however, caused some issues on embryonic development. Adverse effects aredue to be caused by the release of cadmium, as surface PEGylation of the Quantum Dotsreduces these issues. A recently published paper shows evidences of an epigenetic effect ofQuantum Dots treatment, with general histones hypoacetylation, and a translocation to thenucleus of p53. In this study, mice treated with Quantum Dots for imaging purposes wereanalyzed to investigate the impact on protein expression and networking. Differential monoandbidimensional electrophoresis assays were performed, with the individuation ofdifferentially expressed proteins after intravenous injection and imaging analysis; further, asseveral authors indicate an increase in reactive oxygen species as a possible mean of damagedue to the Quantum Dots treatment, we investigated the signalling pathway of APE1/Ref1, aprotein involved in the response to oxidative stress. Our results, although preliminary, suggestseveral interesting point of discussion on Quantum Dots imaging for in vivo diagnosticapplication, but also for a new therapeutic approach.