Targeted near-IR QDs-loaded micelles for cancer therapy and imaging

The use of water-soluble, functionalized quantum dots (QDs) that are highly stable against oxidation for biological and biomedical applications is currently one of the fastest growing fields of nanotechnology. Polymer-based nanoparticles are now widely used for drug delivery and targeted therapy. We modified the surface of near Infrared QDs by the solid dispersion method using PEG–PCDA and PCDA–Herceptin conjugates to demonstrate water-solubility and target-specific properties. Upon UV irradiation, QD cores located within nanoprobes were further stabilized by intramicellar cross-linking between neighboring PCDA–Herceptin moieties. These cross-linked nanoprobes showed higher stability and less toxicity. Near-IR QDs-loaded micelles were spherical with diameters of around 130–150 nm. The anti-tumor effect of near-IR QDs-loaded micelles against MDA-MB-231 tumors was remarkably better than that of control. Mice treated with the near-IR QDs-loaded micelles had a tumor volume of about 285 mm3, indicating shrinkage in initial tumor volume and inhibition of tumor growth by 77.3% compared to that of control group (saline injection). In addition, near-IR QDs-loaded micelles were injected intravenously into tumor-bearing nude mice for simultaneous tumor therapy and imaging. We observed that the targeted near-IR QDs-loaded micelles distributed rapidly throughout the animal body including the tumor in real time. These multi-functional nanoprobes could therefore be used for both active and passive targeting, imaging and treatment of cancers in the early stage.