Proteinized Surface Remodeling Decouples Environmental Stability from Intracellular Degradation in Oxidation-Prone 2D Nanoborophene

Borophene (BPH), a monolayer boron allotrope, exhibits outstanding electrical and mechanical properties but remains intrinsically constrained by its excessive susceptibility to oxidative degradation in aqueous and physiological environments. This study demonstrates that protein-assisted exfoliation using human serum albumin (HSA) establishes a dynamic biointerfacial sheath (BIS) that decouples environmental stability from intracellular degradation. HSA forms a robust BIS via multivalent hydrophobic, electrostatic, and thiol-mediated interactions, driving exfoliation into ultrathin nanosheets while suppressing air- and serum-induced oxidation. Proteinized BPH (PBPH) shows enhanced extracellular colloidal and chemical stability; however, upon cellular uptake, the same interface promotes rapid reactive oxygen species-driven degradation, leading to lattice fragmentation, loss of crystallinity, and conversion into soluble boronate species. Multimodal analyses confirm accelerated degradation kinetics and environmental stability of PBPH. These results highlight the protein corona as an active regulator of nanomaterial fate, enabling programmable decoupling of extracellular persistence from intracellular clearance in oxidation-prone two-dimensional systems.