Mild Lipid Extraction and Anisotropic Cell Membrane Penetration of α-Phase Phosphorene Carbide Nanoribbons by Molecular Dynamics Simulation Studies

Systematic understanding of the interactions at the nano-bio interface is critical for the development of bio-functional nanomaterials and nano-agents for medical applications which typically require high safety, biocompatibility and therapeutic efficiency. As a new member of two-dimensional material family, α-phase phosphorene carbide (α-PC) attracts enormous research interests in recent years. Benefitted from the unique buckled structure, and its rich physical and chemical features, future applications of α-PC in biological and medical areas are intuitively intriguing. Using molecular dynamics simulations (MD), here we theoretically explore the interactions of α-PC nanoribbons with cell lipid membrane to evaluate the potential biological toxicity to lipids. Our results clearly demonstrate that the α-PC sheet can only penetrate into the membrane along its zigzag direction by attracting the lipids to the groove regions. The membrane undergoes slight structural distortion, but quickly recovers when penetration happened. Only localized impacts are detected to the membrane after the penetration. In contrast, the intrusion along armchair direction is highly blocked by lipids. Free energy analyses by umbrella sampling method revealed that the fatty acid tails of lipids prefer to bind along the groove regions of α-PC rather than across the grooves, resulting in the highly anisotropic penetration behavior. The overall attraction of α-PC to lipid is weaker than graphene, so that the binding lipids cannot be fully extracted from the membrane environment. The self-equilibration of the membrane is fast enough to prevent the lipids from escaping, leading to the well preserved membrane integrity. Our present findings suggest that α-PC might offer new potentialities as bio-agents with high membrane-penetrating efficiency and lower cytotoxicity. The unique anisotropic behaviors can be further utilized for the design and fabrication of specialized nanomaterials with capability of efficient and template-directed molecule delivery.