Core-Shell Semiconducting Polymer Nanoparticles for Detection and Photothermal Ablation of Breast Cancer

Triple negative breast cancer (TNBC) is one of the deadliest among other subtypes of breast cancers due to its absence of standard biomarker expressions, and the aggressive nature of TNBC leads to low patient survival. Current treatment strategies include surgery, chemotherapy, and radiation therapy, although photothermal therapy is an evolving treatment strategy. It has recently been shown that breast cancer can harbor intracellular bacteria, which may impact therapeutic responses. Here we present the use of semiconducting theranostic polymer nanoparticles composed of a photothermal poly[4,4-bis(2-ethylhexyl)- cyclopenta[2,1-b;3,4-b′]-dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe) core with a fluorescent poly[(9,9-dihexylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole (PFBTDBT10) shell for detection and treatment of TNBC cells harboring Staphylococcus aureus bacteria. These dual polymer core-shell nanoparticles (CSNPs) had absorption maxima at 450 nm and 740 nm corresponding to PCPDTBSe and DBT10 respectively. The quantum yield was 9.64% The core diameter was 83 nm and the CSNPs were 125 nm, both with negative zeta potential. Exposure of TNBC cells (MDA MB 231) to the CSNPs for 24 h resuslted in a 50% reduction in viability, wheras non-tumorigenic breast epitherlial cells (MCF 10A) were not impacted at 250 ug/ml in the absence of infrared light. Exposure to 800 nm resulted in a temperature change of 15°C at 250 ug/ml of CSNPs exposed to 3W of 800 nm light for 60 s. This led to a 75% reduction in uninfected MCF 10A cells, but only a 60% reduction when this cell line was infected. Uninfected MDA MB 231 cells subjected to 250 ug/ml of CSNPs and 800 nm (3W for 60 s had a 40% reduction in viability, and the infected cells had a 70% reduction. Differences in cell response to PTT whether the cells were infected or not indicates that infected TNBC cells may be preferentially more sensitive to CSNP-induced PTT. The CSNPs could be imaged within the cells, setting the stage for using this CSNPs for detection of breast cancer and precision photothermal ablation.