Hybrid poly(ε-caprolactone)–carbon dot nanoparticles as self-tracking theranostic tools for precise docetaxel delivery

Hybrid nanocomposites combining biodegradable polymers with fluorescent nanomaterials offer innovative strategies for theranostic applications. In this work, carbon nanodots (CDs) were successfully incorporated into a polycaprolactone (PCL) matrix to create a hybrid material exhibiting intrinsic multicolor fluorescence and high potential for sustained image-guided anticancer drug release. The resulting PCL–CDs blend was used to fabricate self-tracking biodegradable nanoparticles (NPs) through a green nanoprecipitation process optimized for sustained drug delivery. When loaded with docetaxel (DTX), used as a model hydrophobic drug, the PCL–CDs NPs achieved a high drug-loading capacity (∼16.5%) and an encapsulation efficiency of 98%, while maintaining an average particle size of approximately 200 nm. The NPs exhibited a sustained, pH-responsive release profile and demonstrated significant cytotoxic activity in a triple-negative breast cancer model. Furthermore, the formulation showed excellent colloidal stability in aqueous dispersion for up to 10 days, guaranteeing suitable storage before the administration. We also studied the best cryoprotection strategy to prepare a stable lyophilized powder for long-lasting storage of the PCL-CDs@DTX NPs, identifying L-arginine as the best option to obtain redispersible systems with an appropriate diameter (∼200 nm). By integrating fluorescence-based bioimaging with controlled chemotherapeutic delivery, these PCL–CDs NPs represent a robust, versatile, and sustainable theranostic nanoplatform with strong potential for precision cancer therapy.