From small molecules to entire organisms, evolution has refined biological structures at the nanoscale, microscale and macroscale to be chiral-that is, mirror dissymmetric. Chirality results in biological, chemical and physical properties that can be influenced by circularly polarized electromagnetic fields. Chiral nanoscale materials can be designed that mimic, refine and advance biological chiral geometries, to engineer optical, physical and chemical properties for applications in photonics, sensing, catalysis and biomedicine. In this Review, we discuss the mechanisms underlying chirality transfer in nature and provide design principles for chiral nanomaterials. We highlight how chiral features emerge in inorganic materials during the chemical synthesis of chiral nanostructures, and outline key applications for inorganic chiral nanomaterials, including promising designs for biomedical applications, such as biosensing and immunomodulation. We conclude Nature Reviews Bioengineering Review article nanostructures). We describe hierarchical multiscale chirality in biological systems (for example, cytoskeleton hypothesis and chirality in biominerals), and analyse the most abundant chirality transfer mechanisms in biology, including enantioselective interaction between surfaces and chiral molecules, template-induced synthesis and chirality transfer, and photon-induced chiral nanomaterials. However, as in many natural systems 54 , these transfer mechanisms cannot be analysed separately because a concomitance of effects is responsible for the resulting chiral morphologies, in particular for highly crystalline nanomaterials, for which template-induced and photon-induced syntheses cannot be entirely decoupled from enantioselective interactions at high Miller index surfaces. Finally, we present potential applications in photonics (for example, polarization-control, non-linear optics), sensing (enantiomer discrimination), catalysis (chemical and pharmaceutical) and biomedicine (for example, photothermal and photodynamic therapies).
Chirality in biologyChirality exists across multiple size scales in biological entities, dictating their geometries, properties and behaviour. For example, aminoacyl-tRNA synthases, enzymes involved in the selection of amino acids in protein synthesis, preferentially bind to l-amino acids by steric exclusion of d-amino acids 55 . Peptide elongation of d-amino acids at the ribosomes is slow owing to the large distance between the reaction sites 56 , limiting the production of peptides with incorporated d-amino acids 57,58 . The incorporation of some d-amino acids, such as d-Asp and d-Ser, has been linked to amyloid-β peptides present in the brains of patients with Alzheimer disease 59 , indicating that chirality at the molecular level could extend its influence to the organism and its behaviour.Chirality also offers survival advantage(s) for organisms. Fan-like petal arrangements of mutated Arabidopsis thaliana show left-handed chirality and clockwise twisting. The handedness of their asymmetric g...