Synthesis and characterization of cecropin peptide-based silver nanocomposites: Its antibacterial activity and mode of action.

Novel antimicrobial agents with a low propensity to develop resistance by microorganisms have contemporary relevance. In this perspective, the present study reports the green synthesis and characterization of cecropins peptides (D2A21, D2A10, and D4E1) based silver nanocomposites. The effect of pH and concentration of peptides on the formation of nanocomposite material was studied using UV-Vis spectroscopy. The particle size was determined by transmission electron microscopy, which indicated the size in the range of 3 ±â€¯0.4 to 20 ±â€¯5 nm. Fourier-transform infrared spectroscopy studies suggested the involvement of peptides as a capping and reducing agent. Zeta potential analysis suggested that nanocomposite material was more cationic in nature than its native peptides. Nanocomposite material exhibited significantly enhanced antibacterial activity as compared to native peptides and silver nanoparticles with minimum inhibitory concentration (MIC) ranging from 1 to 3 µg mL-1 against both gram-positive and negative test bacteria; whereas the MICs of native peptides were found to be in the range of 4-6 µg mL-1. The mode of action of P-AgNPs was evaluated using scanning electron microscopy, membrane potential, and membrane integrity studies; wherein the nanocomposite material was found to act at the cell membrane level, causing complete loss of membrane potential and resulting in compromised membrane integrity with irreversible damage to the cell as shown by the rapid loss of viability due to membrane disruption, resulting in lysis. Among the three peptides tested, D2A21-silver nanocomposite had maximal antibacterial activity. Taken together; our experimental findings suggested that the peptide-based-silver nanocomposites can be considered as potential antibacterial agents for various biomedical applications.

Cecropin-P17, an analog of Cecropin B, inhibits human hepatocellular carcinoma cell HepG-2 proliferation via regulation of ROS, Caspase, Bax, and Bcl-2.

Cecropin-P17 is a peptide derived from Cecropin B. In this study, we investigated the effects and relative mechanisms of Cecropin-P17 in a human liver cancer cell line (HepG-2) in vitro and in vivo. A cell viability assay, Annexin V/propidium iodide assay, western blot, flow cytometry, quantitative real-time polymerase chain reaction, and a tumor-xenograft model were applied to elucidate the mechanism exerted by Cecropin-P17 on HepG-2 cells. Cecropin-P17 significantly inhibited the proliferation of HepG-2 cells and demonstrated low cytotoxicity to normal liver cells in vitro. The apoptotic rate of HepG-2 cells was increased after Cecropin-P17 treatment together with increased production of reactive oxygen species. Moreover, Cecropin-P17 stimulated caspase-3, caspase-9, and Bax and inhibited Bcl-2 on both the transcriptional and translational levels. Finally, Cecropin-P17 significantly suppressed tumor growth in a HepG-2-bearing nude mouse model. All of these results indicated that Cecropin-P17 could be a potential agent for the treatment of liver cancer.

Anionic C-terminal proregion of nematode antimicrobial peptide cecropin P4 precursor inhibits antimicrobial activity of the mature peptide.

Recently, an anionic proregion was found to be conserved at the C terminus of the antimicrobial peptide, nematode cecropin. Our results suggest that the antimicrobial activity of mature peptide is suppressed by the proregion in its precursor and is released from inhibition after processing. Inhibition is not likely to be due to direct suppression of membrane disruption.