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Fluorescent probes are extensively used in oncology for diagnostic applications, particularly for intra-operative tumor delineation. However, one of the biggest challenges of fluorescent contrast agents is the need for high signal-to-noise ratio in order to overcome background autofluorescence and be able to identify the tumor from surrounding normal tissue. Here we present a novel core-shell nanoparticle contrast agent, based on perovskite quantum dots (PQDs), which are gaining popularity due to their high quantum yield (<90%), size tunability and the ability to alter the emission spectrum by changing the halide ion. However, the biological applications of perovskites are almost non-existent due to their vulnerability in aqueous environment, as they rapidly disintegrate, even in the presence of moisture. Our approach involves developing nanoparticles with hydrophobic matrix containing a high density of PQDs in its core. We explore the efficiency of different hydrophobic polymers including polystyrene, silica and poly(lactic-co-glycolic acid) in protecting the PQDs from water and compared their long term effectiveness, observed over a period of two months. The feasibility of utilizing these nanoparticles as contrast agents was tested on breast cancer cells. The small size of the nanoparticles, which is typically ~60-70 nm, facilitate their intake inside cells via receptor-mediated endocytosis, thereby selectively lighting up the cancer cells green. This method will open new applications of perovskite nanocrystals in biomedical imaging including tumor detection, both pre- and intra-operatively, as well as therapy monitoring by aiding in tracking of drugs/nanoparticles.
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