On the interface between biomaterials and two-dimensional materials for biomedical applications

Aromatic Amino Acid-Dependent Surface Assembly of Amphiphilic Peptides for One-Step Graphite Exfoliation and Graphene Functionalization

Amphiphilic peptides show great potential for exfoliating graphite and functionalizing graphene. However, the variety of amino acids complicates our understanding of the underlying mechanisms. In this study, we designed four peptides (C6W1, C6W2, C6W4, and C6W6) with different amounts of aromatic tryptophan amino acids and two additional peptides (C6F4 and C6Y4) by substituting tryptophan with aromatic phenylalanine or tyrosine. This allowed us to investigate the processes and mechanisms of graphite exfoliation and graphene functionalization. Using experimental and computational methods, we discovered that peptides containing tryptophan demonstrated higher exfoliation efficiency and increased tryptophan content further improved this efficiency, resulting in more peptide-functionalized graphene layers. Significantly, the primary driving force for the surface-assisted assembly of peptides on graphite is the π-π stacking interaction between the aromatic ring contributed by aromatic amino acids and the hexagonal rings of the graphite surface. This interaction leads to a layer-by-layer exfoliation mechanism. Our research offers valuable insights into peptide design strategies for one-step graphite exfoliation and graphene functionalization in aqueous environments.

Nanotoxicity of two-dimensional nanomaterials on human skin and the structural evolution of keratin protein

Two-dimensional (2D) materials have been increasingly widely used in biomedical and cosmetical products nowadays, yet their safe usage in human body and environment necessitates a comprehensive understanding of their nanotoxicity. In this work, the effect of pristine graphene and graphene oxide (GO) on the adsorption and conformational changes of skin keratin using molecular dynamics simulations. It is found that skin keratin can be absorbed through various noncovalent driving forces, such as van der Waals (vdW) and electrostatics. In the case of GO, the oxygen-containing groups prevent tighter contact between skin keratin and the graphene basal plane through steric effects and electrostatic repulsion. On the other hand, electrostatic attraction and hydrogen bonding enhance their binding affinity to positively charged residues such as lysine and arginine. The secondary structure of skin keratin is better preserved in GO system, suggesting that GO has good biocompatibility. The charged groups on GO surface perform as the hydrogen bond acceptors, which is like to the natural receptors of keratin in this physiological environment. This work contributes to a better knowledge of the nanotoxicity of cutting-edge 2D materials on human health, thereby advancing their potential biological applications.

In the View of Electrons Transfer and Energy Conversion: The Antimicrobial Activity and Cytotoxicity of Metal-Based Nanomaterials and Their Applications

The global pandemic and excessive use of antibiotics have raised concerns about environmental health, and efforts are being made to develop alternative bactericidal agents for disinfection. Metal-based nanomaterials and their derivatives have emerged as promising candidates for antibacterial agents due to their broad-spectrum antibacterial activity, environmental friendliness, and excellent biocompatibility. However, the reported antibacterial mechanisms of these materials are complex and lack a comprehensive understanding from a coherent perspective. To address this issue, a new perspective is proposed in this review to demonstrate the toxic mechanisms and antibacterial activities of metal-based nanomaterials in terms of energy conversion and electron transfer. First, the antimicrobial mechanisms of different metal-based nanomaterials are discussed, and advanced research progresses are summarized. Then, the biological intelligence applications of these materials, such as biomedical implants, stimuli-responsive electronic devices, and biological monitoring, are concluded based on trappable electrical signals from electron transfer. Finally, current improvement strategies, future challenges, and possible resolutions are outlined to provide new insights into understanding the antimicrobial behaviors of metal-based materials and offer valuable inspiration and instructional suggestions for building future intelligent environmental health.