Stable nanoconjugates of transferrin with alloyed quaternary nanocrystals Ag–In–Zn–S as a biological entity for tumor recognition

One way to limit the negative effects of anti-tumor drugs on healthy cells is targeted therapy employing functionalized drug carriers. Here we present a biocompatible and stable nanoconjugate of transferrin anchored to Ag-In-Zn-S quantum dots modified with 11-mercaptoundecanoic acid (Tf-QD) as a drug carrier versus typical anticancer drug, doxorubicin. Detailed investigations of Tf-QD nanoconjugates without and with doxorubicin by fluorescence studies and cytotoxic measurements showed that the biological activity of both the transferrin and doxorubicin was fully retained in the nanoconjugate. In particular, the intercalation capabilities of free doxorubicin versus ctDNA remained essentially intact upon its binding to the nanoconjugate. In order to evaluate these capabilities, we studied the binding constant of doxorubicin attached to Tf-QDs with ctDNA as well as the binding site size on the ctDNA molecule. The binding constant slightly decreased compared to that of free doxorubicin while the binding site size, describing the number of consecutive DNA lattice residues involved in the binding, increased. It was also demonstrated that the QDs alone and in the form of a nanoconjugate with Tf were not cytotoxic towards human non-small cell lung carcinoma (H460 cell line) and the tumor cell sensitivity of the DOX-Tf-QD nanoconjugate was comparable to that of doxorubicin alone.