The present work is focused on the long-term stability and in vitro cellular internalization of newly designed biocompatible polyester nanocapsules prepared via nanoprecipitation approach with mean diameter <165 nm and narrow size distribution, dedicated to theranostic applications. We monitored the optical, morphological, and biological properties of the nanocarriers loaded by multifunctional cargo, i.e., paclitaxel (PTX) and a fluorescent marker: coumarin-6 (CR-6) or Nile Red (NR), by fluorescence and UV-vis spectroscopy (encapsulation efficiency), dynamic light scattering (average size expressed as hydrodynamic diameter, DH), zeta potential (ζ, colloidal stability), atomic force microscopy (AFM, imaging), and confocal laser scanning microscopy (CLSM, nanocapsule visualization, and cellular internalization in vitro by human breast cancer MCF-7/WT cells). The fabricated nanocapsules with optimal composition of oleic phase, i.e., coconut oil, palm oil, and Capmul MCM, as well as polymeric shell, i.e., polylactic acid (PLA), poly (ε-caprolactone) (PCL), and poly (lactide-co-glycolide) (PLGA), showed high loading capacity, long-term stability, and improved localization of the active cargo in studied tumor cells. Therefore, our results prove that the studied polyester oil core nanocapsules provide lifelong and biocompatible nanocarriers suitable for in vivo administration and for diagnostic applications.
Keywords: Breast cancer cells; Cellular internalization; Colloidal stability; Coumarin-6; Cytostatic drug; Nile Red; Polyester nanocarriers.