Polyhydroxybutyrate-phospholipid hybrid nanoparticles containing 5-fluorouracil as innovative nanomedicine

Polyhydroxybutyrate (PHB), a microbial polyester of the polyhydroxyalkanoate family, was combined with different phospholipids to design stable nanosystems for the delivery of 5-fluorouracil (5-FU). Among the tested stabilizers, the anionic phospholipid dimyristoylphosphatidylglycerol (DMPG) demonstrated to be the most effective, promoting the development of nanoparticles of ∼190 nm, characterized by a narrow size distribution, a negative Zeta potential and stability across pH variations, temperature changes and after lyophilization. FT-IR analysis confirmed the successful encapsulation of the bioactive compound within the polymer–lipid matrix and. The drug encapsulation was concentration-dependent, with 1 mg/mL of the 5-FU identified as the optimal concentration to be employed as a consequence of the uniform morphology of obtained nanosystems. The nanoformulations were characterized by an initial burst release of 5-FU followed by a sustained leakage of the active compound up to 168 h. Biological assays confirmed the safety of blank nanoparticles, while drug-loaded formulations enhanced cytotoxicity in a cell-dependent manner: in detail, 5-FU-loaded nanoparticles exerted a stronger pharmacological effect with the respect to the free drug in MCF-7 breast cancer cells, whereas a similar efficacy was achieved only after prolonged incubation in Caco-2 cells. The most striking results were observed in three-dimensional MCF-7 spheroids, where the nanoparticle formulation showed a strong growth inhibition compared to 5-FU. Overall, these findings demonstrate that PHB/DMPG containing 5-FU nanoparticles combine suitable physico-chemical characteristics and suitable cytotoxic features in physiologically relevant models, supporting their potential as an innovative nanomedicine for the targeted delivery of hydrophilic chemotherapeutics.