Development of AS1411 aptamer-conjugated chitosan-carbon dot nanocarriers for targeted drug delivery and fluorescent imaging in breast cancer therapy.

Theranostic nanomedicine, combining therapy with diagnostic imaging, offers a powerful strategy for real-time monitoring and targeted treatment of cancer. In the current study, we developed a pH-sensitive delivery system based on chitosan (CS) and poly caprolactone-poly ethylene glycol- poly caprolactone (PCL-PEG-PCL) copolymer, which was conjugated to the AS1411 Aptamer and tagged with carbon dots (CDs), abbreviated as DOX/P/CS-CD-Apt. Then, the theranostic potential of DOX/P/CS-CD-Apt in carrying DOX to MCF-7 breast cancer cells was evaluated both in vitro and in vivo. CDs were synthesized via a one-step hydrothermal method and chemically conjugated to the CS backbone along with AS1411 using EDC/NHS chemistry. On the other hand, DOX is encapsulated into the final carrier through the double emulsion-solvent evaporation method. The nanocarrier was characterized using FT-IR, FESEM, XPS, XRD, TEM, DLS, and zeta potential. Our results represented that DOX/P/CS-CD-Apt were uniform spherical morphology, high drug encapsulation, and controlled release under acidic conditions. Fluorescence microscopy revealed cytoplasmic entrance of DOX/P/CS-CD-Apt in MCF-7 cells, indicating effective nucleolin-mediated uptake. MTT assays and apoptosis evaluation demonstrated the higher cytotoxicity and apoptotic effects compared to free DOX or non-targeted formulations. Moreover, in vivo PET imaging confirmed the selective accumulation of nanoparticles at the tumor site in a 4T1 breast cancer model, along with a notable reduction in tumor size. These findings highlight DOX/P/CS-CD-Apt as a promising theranostic platform for targeted breast cancer therapy with integrated imaging capability.