Bovine serum albumin – persistent nanoparticle interactions: Luminescence and Raman data

• Cr-doped ZGO particles (10–20 nm) were synthesized via the hydrothermal method. • Oleic acid enables a negative surface charge on NPs, reaching up to −50 mV. • Adding NPs to the BSA solution has minimal influence on NPs' optical properties. • Raman shows that BSA is less folded after interaction with negatively charged NPs. Persistent luminescence nanoparticles (PersL NPs) are of considerable interest for their use in the visualization of biological molecules. Meanwhile, the interaction of the PersL NPs with biomolecules, particularly proteins, remains poorly investigated. In the present work, ZnGa₂O₄:Cr³⁺ (ZGO:Cr³⁺) PersL NPs, including surface modifications with oleic acid (OA) and their interactions with the model protein bovine serum albumin (BSA) were investigated. Transmission electron microscopy revealed nanoparticles with sizes ranging from 10 to 20 nm, with OA-functionalized particles exhibiting a characteristic shell-like halo. Modification with OA resulted in a significant increase in surface charge from approximately –2 mV to –50 mV. Fluorescence lifetime measurements of BSA showed only a slight increase upon interaction with the nanoparticles, indicating negligible energy transfer. Raman spectroscopy, focusing on the amide I region, revealed small conformational changes in BSA following interaction with the nanoparticles. Notably, the alpha-helix content increased when interacting with ZGO:Cr³⁺ nanoparticles calcined at 650 °C, suggesting protein stabilization. In contrast, a reduction in alpha-helix content was observed with OA-modified nanoparticles, indicating partial protein unfolding. These findings provide valuable insights into the structural integrity, surface properties, and bio-interactions of ZGO:Cr³⁺ PersL NPs, with implications for bioimaging and nanobiotechnology applications.