[Optimization of unnatural amino acid incorporation in collagen and the cross-linking through thioether bond]

The source of recombinant collagen is clean, and it has the advantages of flexible sequence design, high yield and high purity, so it has a wide application prospect as biomaterials in tissue engineering and other fields. However, how to promote the cross-linking of recombinant collagen molecules and make them form a more stable spatial structure is the difficulty to be overcome in the design of recombinant collagen nanomaterials. Unnatural amino acid O-(2-bromoethyl)-tyrosine was incorporated into collagen by two-plasmid expression system. The results showed that high-purity collagen incorporated with unnatural amino acid could be obtained by induction with final concentration of 0.5 mmol/L IPTG and 0.06% arabinose at 25 °C for 24 hours. The intermolecular cross-linking through thioether bond was formed between collagen molecule incorporated with unnatural amino acid and collagen molecule with cysteine mutation in pH 9.0 NH4HCO3 buffer, which formed aggregates with the largest molecular size up to 1 micrometre. The results pave the way for the design of recombinant collagen biomaterials.