Professor Liu Runhui, East China University of science and technology research group: rapid NCA polymerization to prepare protein protective amino acid polymer

The author: Zhang Junyu protein, a master's student, is widely used in biochemical experimental research and disease treatment However, natural protein will aggregate and denature under extreme conditions such as freezing, dehydration and drying, resulting in reduced activity and increased dosage In order to maintain the stability of protein under extreme conditions, many protein protectors came into being, such as amino acids, sugars, surfactants, liposomes, polymers, etc., but some proteins will lose most of their activities under freeze-drying conditions Therefore, it is urgent to find a cheap, effective, non-toxic and degradable protective agent to protect the protein in the process of freeze-drying Recently, the amino acid polymer synthesized by Professor Liu Runhui of East China University of science and technology through LiHMDS rapid NCA ring opening polymerization can protect β - galactosidase (β - gal) in the process of freeze-drying, so that its activity relative to the original protein can be increased from 40% without adding a protective agent to 80% This achievement was recently published on Biomaterials Science (DOI: 10.1039 / c9bm00484j) In order to find a protective agent that can effectively protect protein during freeze-drying process, this study synthesized and studied the protein protection function of L-glutamic acid homopolymer and L-glutamic acid and L-Lysine copolymer by using the method of rapid NCA polymerization initiated by LiHMDS recently reported by our research group (NAT Commun 2018, 9, 5297) In this study, researchers synthesized a series of amino acid polymers with different chain length and different proportion of internal units These polymers have good biocompatibility and are expected to be used as protein protectors The polymerization can be completed in 5 minutes as soon as possible, and the operation is simple It is suitable for the preparation of parallel sample molecules, and it is convenient for the rapid screening of suitable protein protectors In this study, poly (L-glutamic acid) (PLG), the best amino acid polymer for comprehensive evaluation of biological activity, has good protein protection effect under freeze-drying conditions, and has low cytotoxicity and hemolytic activity for NIH3T3 fibroblasts After freezing cycle, the activity of β - gal showed that there was no significant difference in the protection of protein among the amino acid polymers plg1 (41 MER), plg2 (58 MER), plg3 (150 MER) and plg4 (270 MER) with different chain lengths, which had good protection effect on protein The activity of the unprotected protein was only 40% after the freezing cycle, and the activity of the unprotected protein increased to 80% after the polymer was added Cytotoxic test and hemolytic activity test show that (Fig 2) the chain length of PLG has no effect on cytotoxic and hemolytic activity, indicating that PLG is a potential protective agent for in vivo protective proteins In addition, DLS and TEM showed that after freeze-drying, the protein agglomerated obviously, and the particle size became larger; with the protective agent PLG, the protein basically remained in the natural dispersion state, and the protein activity was obviously protected This shows that PLG, an amino acid polymer, can prevent protein aggregation during freeze-drying, thus maintaining protein activity (Fig 3) Fig 1 Activity of β - gal after freezing cycle (source: Biomaterials Science) Fig 2 (a) cytotoxicity test of PLG polymer with different chain length, (b) hemolytic activity test (source: Biomaterials Science) Fig 3 Schematic diagram of protective protein during freeze-drying process of polymer (source: Biomaterials Science) Li Bing, a graduate student of East China University of science and technology, is the first author and main finisher of the achievement, and Professor Liu Runhui is the corresponding author The research was supported by NSFC and the Ministry of science and technology Review of previous reports: Professor Liu Runhui of East China University of science and technology research group: biomedical materials based on β - polypeptide polymer antibacterial surface modification Professor Liu Runhui of East China University of science and technology research group: simulate host defense peptide fast, efficient and broad-spectrum antibacterial β - polypeptide polymer