Cross-linked, self-fluorescent gold nanoparticle/polypeptide nanocapsules comprising dityrosine for protein encapsulation and label-free imaging

Cross-linked, self-fluorescent Au nanoparticle/polypeptide nanocapsules comprising dityrosine are prepared by the self-assembly of the random copolypeptides comprising L-lysine and L-tyrosine upon subsequent cross-linking of tyrosine residues by chloroaurate reduction. These nanocapsules are demonstrated be useful as encapsulants for protein encapsulation and as optical probes for label-free cell imaging. The reduction process is so mild that the protein can still retain its function.