Stable, polyvalent aptamer-conjugated near-infrared fluorescent nanocomposite for high-performance cancer cell-targeted imaging and therapy

Early diagnosis and targeted therapy are two important ways to improve cancer treatment survival. In this work, via a simple DNA hybridization reaction, DNA-templated fluorescent silver nanoclusters (AgNCs) were successfully assembled around a DNA-modified gold nanoparticle (AuNP) to construct a novel nanocomposite with the functions of cancer cell-specific imaging and targeted therapy. The as-prepared AuNP@(AS1411-AgNCs)n nanocomposite shows strong near-infrared fluorescence emission and improved biostability, and carries a high density of AS1411-the first anticancer aptamer targeting nucleolin protein, which is over-expressed not only on the surface but also in the cytoplasm of cancer cells. The synergy of multivalent AS1411-nucleolin binding promotes accumulation of the nanocomposite towards cancer cells and subsequent internalization in them. This results in highly specific cancer cell-targeted imaging and selective killing in a low AuNP@(AS1411-AgNCs)n concentration range. The prepared nanocomposite also shows great potential as a carrier of doxorubicin to further promote the selective killing of cancer cells.