Attaching chains of PEG (a inert polymer) to a peptide to make it last longer in the body and be less likely to cause an immune reaction.Polyethylene glycol attachment reduces renal clearance (by increasing molecular size), decreases immunogenicity (by shielding the peptide from immune recognition), and extends plasma half-life. PEG-MGF is pegylated mechano growth factor, developed to extend MGF’s plasma half-life for potential systemic delivery. Limitations: PEGylation can reduce receptor binding affinity by sterically hindering the active binding site, and theoretical concerns about PEG accumulation with chronic dosing exist. PEG-related hypersensitivity reactions have been documented with pegylated biologics.