pH-Responsive Bovine Serum Albumin Nanoparticles Encapsulating Doxorubicin-Based Complexes Induce Cuproptosis in Lung Cancer Cells

Background/Objectives: This study investigates the induction of cuproptosis in A549 lung cancer cells by doxorubicin (DOX) complexes and the development of pH-responsive bovine serum albumin (BSA)-based nanocarriers for their delivery. We successfully synthesized and characterized two novel complexes: DOX–Cu, where DOX acts as a ligand for Cu(II), and DOX–BTZ, a conjugate formed between DOX and the proteasome inhibitor bortezomib (BTZ). Methods: Spectroscopic and NMR analyses were performed to confirm the formation of the complexes. In vitro assays were conducted to evaluate cytotoxicity in A549 cells, alongside assessment of DLAT aggregation as a marker of cuproptosis. The formulation of DOX into BSA nanoparticles (DOX–Cu@BSA NPs and DOX–BTZ@BSA NPs) was carried out to evaluate potential alleviation of DOX-induced cytotoxicity in cardiomyocytes in vitro. Fluorescence quenching and molecular docking studies were employed to investigate the binding interactions between the complexes and BSA. Cellular uptake experiments were performed to assess nanoparticle internalization into A549 cells. Results: Both complexes exhibited superior cytotoxicity against A549 cells compared to individual components. This enhanced cell death was associated with significant aggregation of dihydrolipoamide S-acetyltransferase (DLAT), a key marker of cuproptosis, suggesting the involvement of this copper-dependent cell death pathway. The BSA nanoparticles displayed favorable characteristics, including uniform size (~190 nm), high encapsulation efficiency (~75–79%), and colloidal stability. Crucially, they exhibited a pH-responsive drug release profile, with significantly accelerated release under acidic conditions (pH 5.7) mimicking the tumor microenvironment. Fluorescence quenching and molecular docking studies revealed strong, spontaneous binding between the complexes and BSA, primarily driven by hydrophobic interactions. Cellular uptake experiments confirmed efficient internalization of the nanoparticles into A549 cells. Conclusions: Collectively, this work offers a proof-of-concept for a strategy of utilizing BSA-based multidrug delivery systems for cuproptosis induction, offering a potential avenue to enhance therapeutic efficacy while reducing systemic toxicity in lung cancer treatment.