| Long-term cryopreservation of cells is of great significance in the biomedical field.Osmotic injury and ice injury during freezing-thawing are the major factors leading to cell death.Meanwhile,the risk of bacterial infection cannot be ignored.Therefore,in order to fabricate a cryopreservation system with biocompatibility,biodegradability,antibacterial and antifreezing properties,synthesis of functional polypeptides and the related properties were studied in this work,including antibacterial activity,cell membrane-disruptive activity and sheep red blood cells(RBCs)cryopreservation.This thesis consists of three major parts,poly(lysine-co-valine)and its antibacterial activity,hydrophobic amino acid functional poly(aspartic acid)and its membrane-disruptive activity,RBCs cryopreservation by synergistic interaction between hydrophobic amino acid/trehalose functionaized?-polylysine and trehalose,and RBCs cryopreservation by synergistic interaction between trehalose functionized poly(ethylene glycol)(PEG)-b-(lysine-aspartic acid)-phenylalanine and trehalose.Polyhedraloligomericsilsesquioxane-andi-butyl-capped poly(L-lysine-co-L-valine)was synthesized via ring-opening polymerization of lysine and valine N-carboxyanhydride(NCA)monomers,and the polypeptides were facilely doped into poly(?-caprolactone)(PCL)for electrospinning to prepare PCL/polypeptides electrospun membranes.The antibacterial activities of the PCL/polypeptide electrospun membranes were observed against Escherichia coli and Staphylococcus aureus when the content of poly(L-lysine-co-L-valine)was 8%.The PCL/polypeptide electrospun membranes showed trivial cytotoxicity and hemocompatibility.Poly(aspartic acid)-g-phenylalanine-lysine(PFK)was synthesized by chemically tethering L-phenylalanine methyl ester,followed by N?-carbobenzyloxy-L-lysine benzyl ester to the side carboxylic acid groups of poly(aspartic acid).It demonstrated that PFK membrane-disruptive activity was enhanced at p H 7.4,and PFK showed trivial cytotoxicity.It could facilitate entry of calcein into NIH/3T3 fibroblasts and He La cells at the physiological p H,possibly due to locally chemical destabilization of cell membranes by the interaction between the polymer and membrane bilayers.?-Polylysine-g-(4-toluenesulfonyl)-arginine-g-trehalose(PLR8T13)was synthesized by successively tethering N?-(4-toluenesulfonyl)-L-arginine and carboxylated trehalose to the side amino groups of?-polylysine.The specifically synthesized glycopeptide demonstrated enhanced cryosurvival of sheep RBCs up to75.0±2.4%at p H 7.4,along with trehalose molecules.Cryopreservation via membrane stabilization was proposed that PLR8T13 could attach on the cell membrane surface of RBCs to protect the cell membrane from osmotic injury.Meanwhile,Tre could prevent RBCs from ice injury via ice recrystallization inhibition activity.Thus,membrane protection for preventing osmotic stress and ice injury could be boosted via synergistic interaction between PLR8T13 and Tre.PLR8T13 showed trivial cytotoxicity and hemocompatibility.Both RBCs cryopreservation and antibacterial activity could be obtained when 1.0 mg·m L-1 PLR8T13 was mixed with 40.0?g·m L-1?-PL.The PEG-b-poly(lysine-co-aspartic acid)-phenylalanine(PKDF)was synthesized via ring-opening polymerization of lysine,aspartic acid and phenylalanine N-carboxyanhydride(NCA)monomers,and then PKDFT was synthesized by successively tethering Tre-COOH to the side amino groups of PKDF.RBCs cryopreservation could be conducted via synergistic interaction between PKDFT and Tre.What's more,the optimal RBCs post-thawing survival could be up to 87.4±0.3%.PKDFT showed trivial cytotoxicity and homocompatibility. |
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