Multifunctional Complexes Based on Photoluminescent Upconversion Nanoparticles for Theranostics of the HER2-Positive Tumors

Combining diagnostic and therapeutic functions in one agent is a promising strategy in the development of personalized approaches to the treatment of cancer. The opportunity to combine diagnostics and therapy appeared with the development of nanobiotechnologies and was realized in the concept of theranostics. To date, a number of promising agents based on nanomaterials capable of diagnosing, targeted therapeutic effects, and monitoring the response of tumor cells were obtained within the approach of theranostics. In this work, a new type of theranostic complexes based on upconversion nanoparticles coated with polyethylene glycol and functionalized with the DARPin–LoPE recombinant targeted toxin was developed. Selective binding of complexes to human breast adenocarcinoma cells overexpressing the HER2 receptor and specific toxicity to them were shown.