| dc.description.abstract | In the previous study, Indolicidin (IL) was added a cystein to its N- and C- terminus, which were denoted as CIL and ILC, respectively. Using molecular dynamics simulations, we found that the grafted IL inserted into the cell membrane mainly related to their tryptophan residues. In order to validate these simulation results, the fourth and eighth tryptophans in the ILC sequence and the eighth and ninth tryptophans in the CIL sequence were replaced with glycine, which were denoted as ILC48 and CIL89, respectively. The hemolysis assay demonstrated that ILC and CIL were highly hemolytic. In contrast, hemolysis caused by ILC48 or CIL89 was low. This trend was consistent to the results of MTT assay, suggesting the reduction of tryptophan should be beneficial to biosaftey. For gene delivery purpose, these peptides were combined with PEI either as conjugates or as mixture to deliver plasmid DNA. In the conjugation form, different from PEI-ILC and PEI-CIL which demonstrated good transfection efficiency, PEI-ILC48 and PEI-CIL89 were unable to transfect cell. Then, we mixed peptides and PEI with DNA as ternary nanocomplexes for transfection. These cysteine-containing peptides can form as dimers through disulfide bond formation. Compared to the monomeric form, dimeric peptides demonstrated superior transfection efficiency. Especially, ILC48 and CIL89 were capable of promoting PEI-mediated gene delivery. We deduced that the dimeric peptide owned more positive charges and larger molecular weights, which increased their complexing ratio to DNA. In addition, their cleavage also facilitated DNA release from peptides intracellularly. Through this comprehensive study, we can determine the importance of tryptophan in peptide for gene delivery. And these results may provide useful information to design a safe and efficient non-viral vector. | en_US |