ABSTRACT
Periodontal disease is triggered by surface bacterial biofilms where bacteria are less susceptible to antibiotic treatment. The development of liposome-based delivery mechanisms for the therapeutic use of antimicrobial peptides is an attractive alternative in this regard. The cationic antimicrobial peptide LL-37 (human cathelicidin) is well-known to exert antibacterial activity against P orphyromonas gingivalis, a keystone oral pathogen. However, the antibacterial activity of the 16-amino acid fragment (LL17-32) of LL-37, is unknown. In addition, there are still gaps in studies using liposomal formulations as delivery vehicles of antibacterial peptides against this pathogen. This study was designed to examine the influence of the different types of liposomal formulations to associate and deliver LL17-32 to act against P. gingivalis. Chitosans of varying Mw and degree of acetylation (DA) were adsorbed at the surface of soya lecithin (SL) liposomes. Their bulk (average hydrodynamic size, ζ-potential and membrane fluidity) and ultrastructural (d-spacing, half-bilayer thickness and the water layer thickness) biophysical properties were investigated by a panel of techniques (DLS, SAXS, M3-PALS, fluorescence spectroscopy and TEM imaging). Their association efficiency, in vitro release, stability, and efficacy in killing the periodontal pathogen P. gingivalis were also investigated. All liposomal systems possessed spherical morphologies and good shelf-life stabilities. Under physiological conditions, chitosan formulations with a high DA demonstrated enhanced stability in comparison to low DA-chitosan formulations. Chitosans and LL17-32 both decreased SL-liposomal membrane fluidity. LL17-32 exhibited a high degree of association with SL-liposomes without in vitro release. In biological studies, free LL17-32 or chitosans alone, demonstrated microbicidal activity against P. gingivalis, however this was attenuated when LL17-32 was loaded onto the SL-liposome delivery system, presumably due to the restrained release of the peptide. A property that could be harnessed in future studies (e.g., oral mucoadhesive slow-release formulations).
ABSTRACT
Objective To reconstruct the proteinic sequence of human cathelicidin LL-37 to increase the bactericidal activity of LL-37 and to express the reconstructed LL-37 (rLL-37) in bacterium. Methods The two dimensional structure, three dimensional structure and chemical characteristic of LL-37 were analyzed by Soft Ware Anthepro 5.0 and SWISS-MODEL. Without the three dimensional changes of LL-37, some negative amino acids of human cathelicidin LL-37 were replaced by positive amino acids and the positive charge of LL-37 was increased. According to the proteinic sequence changes of rLL-37, the DNA sequence of rLL-37 was reconstructed by Touch-Down PCR and recombined with vector pET-28a (+), thus rLL-37 was expressed in E.coli. BL21 (DE3) by the induction of IPTG and was purified by chromatography. Results Glu~ 16 , Asp~ 26 , Glu~ 36 of LL-37 were replaced by Gln~ 16 , Asn~ 26 , Gln~ 36 and the static charge of LL-37 was increased from +5.8 to +9.0 at pH 7.4. The DNA sequence of rLL-37 was reconstructed and inserted into vector pET-28a (+), the rLL-37 was expressed in E.coli. BL21 (DE3) and purified by strong cation exchange supports Macro-Prep High S successfully. The rLL-37 was proved by the means of inhibitory zone to be able to kill Gram-negative bacteria and Gram-positive bacteria. Conclusion It is feasible to reconstruct human cathelicidin LL-37 and express the protein in bacteria by fusion, which make it possible to produce more rLL-37 and study its biological function deeply.
ABSTRACT
Objective To employ 2 approaches to construct and express reconstructed LL-37 (rLL-37) in procaryotic system, and to explore a better preparation method. Methods The first method: the rLL-37 was inserted into vector pET-28a (+), then was induced to express in E.coli. BL21 (DE3) and purified by chromatography; the second method: the rare codons in the rLL-37 gene sequence were substituted by the preferred codons of procaryotic cell, and a fragment of carrier protein molecule (CPM) was added to the N termination of the objective sequence to construct expression plasmid pET-30a(+)-CPM-rLL-37, then the rLL-37 was expressed in E.coli. BL21 Star(DE3) and purified by chromatography. The productive rates of the 2 methods were compared and the antimicrobial effects of obtained rLL-37 was studied. Results The first method: the DNA sequence of rLL-37 was obtained successively by Touch-Down PCR. The expression plasmid pET-30a(+)-CPM-rLL-37 was expressed with fusion protein in E.coli BL21 (DE3). The expression rate accounted for 20% of total bacterio-protein, then the expressed product was purified by using high positive ion exchange column Macro-Prep High S; The second method: a fragment of carrier protein molecule was designed that contained 28 amino-acid residue and its pHi was 2.7, net charge was-6.0 at pH 7.4. After the expression plasmid pET-30a(+)-CPM-rLL-37 was constructed successively, it was expressed in E.coli BL21 Star (DE3). The expressed fusion protein accounted for 35% of total bacterio-protein, then the expressed product was purified by using affinity binding chromatography with TALON resins successfully. The obtained 2 kinds of rLL-37 were able to kill both Gram-negative and-positive bacteria by the means of inhibitory zone. Conclusion It’s feasible to prepare efficiently rLL-37 in procaryotic system, which founds the basis for the further research on bactericidal activity of rLL-37.