Amino acid-mPEGs: Promising excipients to stabilize human growth hormone against aggregation

Objective(s): Today, the non-covalent PEGylation methods of protein pharmaceuticals attract more attention and possess several advantages over the covalent approach. In the present study, Amino Acid-mPEGs (aa-mPEGs) were synthesized, and the human Growth Hormone (hGH) stability profile was assessed in their presence and absence.Materials and Methods: aa-mPEGs were synthesized with different amino acids (Trp, Glu, Arg, Cys, and Leu) and molecular weights of polymers (2 and 5 KDa). The aa-mPEGs were analyzed with different methods. The physical and structural stabilities of hGH were analyzed by SEC and CD spectroscopy methods. Physical stability was assayed at different temperatures within certain intervals. Molecular dynamics (MD) simulation was used to realize the possible mode of interaction between protein and aa-mPEGs. The cell-based method was used to evaluate the cytotoxicity.Results: HNMR and FTIR spectroscopy indicated that aa-mPEGs were successfully synthesized. hGH as a control group is known to be stable at 4 °C; a pronounced change in monomer degradation is observed when stored at 25 °C and 37 °C. hGH:Glu-mPEG 2 kDa with a molar ratio of 1:1 to the protein solution can significantly increase the physical stability. The CD spectroscopy method showed that the secondary structure of the protein was preserved during storage. aa-mPEGs did not show any cytotoxicity activities. The results of MD simulations were in line with experimental results.Conclusion: This paper showed that aa-mPEGs are potent excipients in decreasing the aggregation of hGH. Glu-mPEG exhibited the best-stabilizing properties in a harsh environment among other aa-mPEGs

Symmetrical ammonium dibromide as an efficient promoter for the ultrasonic irradiation multi-component preparation of pyrrolidine derivatives

In this work, a method has been developed for the formal, multi-component reaction of cyclopropyl dicarboxylates, aldehydes, and amines under ultrasonic irradiation. The symmetrical dibromide salt (A) was prepared from the reaction of 1,2-bis(2-bromoethoxy)ethane with 2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine in toluene under reflux condition. CeCl3 and compound (A) were used as catalyst and promoter and showed a good potential for application in the synthesis of a range of structurally diverse pyrrolidine rings in short reaction times (3–5 h) and excellent yields (89–97 %)