Acrylate-PEG-Maleimide (MAL-PEG-Acrylate, ACRL-PEG-MAL) is a cross-linking agent with a PEG spacer, with maleimide groups and acrylate groups at both ends, and one end The acrylate can be polymerized with UV light or a free radical initiator, and the maleimide at the other end can react with a thiol-containing group. PEG derivatives with acrylate functional groups can be used to prepare hydrogels by radical polymerization process. Because polyethylene glycol can increase its solubility and reduce the immunogenicity of peptides and proteins.