Beyond the passive interactions at the nano-bio interface: evidence of Cu metalloprotein-driven oxidative dissolution of silver nanoparticles

Abstract

BackgroundIn a biological system, an engineered nanomaterial (ENM) surface is altered by adsorbed proteins that modify ENM fate and toxicity. Thus far, protein corona characterizations have focused on protein adsorption, interaction strength, and downstream impacts on cell interactions. Given previous reports of Ag ENM disruption of Cu trafficking, this study focuses on Ag ENM interactions with a model Cu metalloprotein, Cu(II) azurin. The study provides evidence of otherwise overlooked ENM-protein chemical reactivity within the corona: redox activity.ResultsCitrate-coated Ag ENMs of various sizes (10–40 nm) reacted with Cu(II) azurin resulted in an order of magnitude more dissolved ionic silver (Ag(I)(aq)) than samples of Ag ENMs only, ENMs mixed Cu(II) ions, or control proteins such as cytochrome c and horse radish peroxidase. This dramatic increase in ENM oxidative dissolution was observed even when Cu(II) azurin was combined with a diverse mixture of Escherchia coli proteins to mimic the complexity of the cellular conona. SDS PAGE results confirm that the multiprotein ENM corona includes azurin. A Cu(I)(aq) colorimetric indicator confirms Cu(II) azurin reduction upon interaction with Ag ENMs, but not with the addition of ionic silver, Ag(I)(aq).ConclusionsCu(II) azurin and 10–40 nm Ag ENMs react to catalyze Ag ENM oxidative dissolution and reduction of the model Cu metalloprotein. Results push the current evaluation of protein-ENM characterization beyond passive binding interactions and enable the proposal of a mechanism for reactivity between a model Cu metalloprotein and Ag ENMs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0160-6) contains supplementary material, which is available to authorized users.

<p>Targeted delivery of doxorubicin to HER2 positive tumor models</p>

“…The enhanced effect of doxorubicin entrapped in targeted exosomes can be explained by a higher dosage of doxorubicin accumulated in the tumor tissue using targeted exosomes for delivery 24. We confirmed that exo-DOX significantly increases the anti-cancer effect of doxorubicin against TUBO cells, by increasing the stability and/or uptake of this drug compared to the free DOX at 72 hours in vitro (Figure 5B).…”

“…As one of the most effective chemotherapeutic drugs,6 doxorubicin causes cytotoxicity via several mechanisms, including intercalation into DNA and/or cell membrane damaging by free radicals 24. On the other hand, doxorubicin has been associated with low bioavailability and adverse side-effects such as cardiotoxicity and myelosuppression,6 as well as kidney, liver, and indirect brain toxicity 25…”

“…The rHER2/neu proto-oncogene was driven by the mouse mammary tumor virus (MMTV) promoter 28–30. Although this tumor model may help to predict a reaction in the body, subcutaneous injection cannot reproduce the real tumor microenvironment, which is one of the disadvantages for these models 24…”

Interaction of silver nanoparticles with antioxidant enzymes

“…In the case of copper protein, the redox interaction between AgNPs and CuIJII) cofactors have been previously reported. 23 It could be suggested that, while SOD is adsorbed at the AgNP surface, its active site was not in a favourable position for electronic transfer to occur.…”

“…20 The link between AgNP stability and enzymatic activity was also reported in other studies. [21][22][23] Motivated by these outputs, we focused on CAT and SOD due to their differences in the tertiary structure, tetramer vs. dimer, and the nature of their native metallic cofactors. CAT is a globular protein of 250 kDa comprised of 4 subunits, and each monomer contains an Fe-heme center.…”