Researchers figured out the best way to attach a PEG molecule to a combined LL‑37 and interferon‑α2a protein, which makes the protein stay in the body longer and reduces immune reactions while keeping most of its original activity.

PEGylating is an effective way for prolonging the half-time period and decreasing the immunogenicity of protein drugs. With experiments of single factor, it was proved that the optimal processes for PEGylating the fused protein of LL-37 and interferon (IFN)-α2a were: PEG molecular weight was 5,000, fused protein concentration was 0.6 mg/mL, the mole ratio of protein to mPEG₅₀₀₀-SS was 1:10, the reaction temperature was 4 °C, and the pH was 9.0, respectively. With orthogonal experiments, we proved that the influential order of 3 main factors is: the fused protein concentration > the mole ratio of protein and mPEG₅₀₀₀-SS > pH and the optimal conditions were the fused protein concentration as 0.6 mg/mL, the mole ratio of protein and mPEG₅₀₀₀-SS as 1:10, pH as 8.8. Under these optimal conditions, the average rate of PEGylated protein with 3 times parallel experiments was 86.98%. After PEGylated, the interferon activity and antimicrobial activity of fused protein could be remained higher than 58% and 97%, respectively.