Conventional antibiotics are facing strong microbial resistance that has recently reached critical levels. This situation is leading to significantly reduced therapeutic potential of a huge proportion of antimicrobial agents currently used in clinical settings. Antimicrobial peptides (AMPs) could provide the medical community with an alternative strategy to traditional antibiotics for combating microbial resistance. However, the development of AMPs into clinically useful antibiotics is hampered by their relatively low stability, toxicity, and high manufacturing costs. In this study, a novel in-house-designed potent ultrashort AMP named RBRBR was encapsulated into chitosan-based nanoparticles (CS-NPs) based on the ionotropic gelation method. The encapsulation efficacy reported for RBRBR into CS-NPs was 51.33%, with a loading capacity of 10.17%. The release kinetics of RBRBR from the nanocarrier exhibited slow release followed by progressive linear release for 14 days. The antibacterial kinetics of RBRBR-CS-NPs was tested against four strains of Staphylococcus aureus for 4 days, and the developed RBRBR-CS-NPs exhibited a 3-log decrease in the number of colonies when compared to CS-NP and a 5-log decrease when compared to control bacteria. The encapsulated peptide NP formulation managed to limit the toxicity of the free peptide against both mammalian cells and human erythrocytes. Additionally, the peptide NPs demonstrated up to 98% inhibition of biofilm formation when tested against biofilm-forming bacteria. Loading RBRBR into CS-NPs could represent an innovative approach to develop delivery systems based on NP technology for achieving potent antimicrobial effects against multidrug-resistant and biofilm-forming bacteria, with negligible systemic toxicity and reduced synthetic costs, thereby overcoming the obstructions to clinical development of AMPs.

Introduction: As the development of new antimicrobial agents faces a historical decline, the issue of bacterial drug resistance has become a serious dilemma that threatens the human population worldwide. Antimicrobial peptides (AMPs) represent an attractive and a promising class of antimicrobial agents. Aim: The hybridization of AMPs aimed at merging two individual active fragments of native peptides to generate a new AMP with altered physicochemical properties that translate into an enhanced safety profile. Materials and methods: In this study, we have rationally designed a new hybrid peptide via combining two individual α-helical fragments of both BMAP-27 and OP-145. The resultant peptide, was evaluated for its antimicrobial and antibiofilm activity against a range of microbial strains. The resultant peptide was also evaluated for its toxicity against mammalian cells using hemolytic and anti proliferative assays. Results: The antimicrobial activity of H4 revealed that the peptide is displaying a broad spectrum of activity against both Gram-positive and Gram-negative bacteria including standard and multidrug-resistant bacterial strains in the range of 2.5–25 μM. The new hybrid peptide displayed potent activity in eradicating biofilm-forming cells, and the reported minimum biofilm eradication concentrations were equal to the minimum inhibitory concentration values reported for planktonic cells. Additionally, H4 exhibited reduced toxicity profiles against eukaryotic cells. Combining H4 peptide with conventional antibiotics has led to a dramatic enhancement of the antimicrobial activity of both agents with synergistic or additive outcomes. Conclusion: Overall, this study indicates the success of both the hybridization and synergism strategy in developing AMPs as potential antimicrobial therapeutics with reduced toxicity profiles that could be efficiently employed to eradicate resistant bacterial strains and enhance the selectivity and toxicity profiles of native AMPs.

There is great interest in the development of antimicrobial peptides as a potentially novel class of antimicrobial agents. Several structural determinants are responsible for the antimicrobial and cytolytic activity of antimicrobial peptides. In our study, a new synthetic peptide analog, AamAP1-Lysine from the naturally occurring scorpion venom antimicrobial peptide AamAP1, was designed by modifying the parent peptide in order to increase the positive charge and optimize other physico-chemical parameters involved in antimicrobial activity. AamAP1-Lysine displayed potent antibacterial activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration was in the range of 5 to 15 µM with a 10 fold increase in potency over the parent peptide. The hemolytic and antiproliferative activity of AamAP1-Lysine against eukaryotic mammalian cells was minimal at the concentration range needed to inhibit bacterial growth. The antibacterial mechanism analysis indicated that AamAP1-Lysine is probably inducing bacterial cell death through membrane damage and permeabilization determined by the release of β-galactosidase enzyme from peptide treated E. coli cells. DNA binding studies revealed that AamAP1-Lysine caused complete retardation of DNA migration and could display intracellular activities in addition to the membrane permeabilization mode of action reported earlier. In conclusion, AamAP1-Lysine could prove to be a potential candidate for antimicrobial drug development in future studies.

The recent upsurge of multidrug resistant bacteria (MDRB) among global communities has become one of the most serious challenges facing health professionals and the human population worldwide. Cationic ultrashort antimicrobial peptides (USAMPs) are a promising group of molecules that meet the required criteria of novel antimicrobial drug development. UP-5, a novel penta-peptide, displayed significant antimicrobial activities against various standard and clinical isolates of MDRB. UP-5 displayed MICs values within the range of (10–15 μM) and (55–65 μM) against Gram-positive and Gram-negative bacteria, respectively. Furthermore, UP-5 displayed antibiofilm activity with minimum biofilm eradication concentration (MBEC) value as equal to twofold higher than MIC value. At the same inhibitory concentrations, UP-5 exhibited very low or negligible toxicity toward human erythrocytes and mammalian cells. Combining UP-5 with conventional antibiotics led to a synergistic or additive mode of action that resulted in the reduction of the MIC values for some of the antibiotics by 99.7% along a significant drop in MIC values of the peptide. The stability profile of UP-5 was evaluated in full mouse plasma and serum with results indicating a more stable pattern in plasma. The present study indicates that USAMPs are promising antimicrobial agents that can avoid the negative characteristics of conventional antimicrobial peptides. Additionally, USAMPs exhibit good to moderate activity against MDRB, negligible toxicity, and synergistic outcomes in combination with conventional antimicrobial agents.

Within this study, a unique 3D structure-based pharmacophore model of the enzyme glyoxalase-1 (Glo-1) has been revealed. Glo-1 is considered a zinc metalloenzyme in which the inhibitor binding with zinc atom at the active site is crucial. To our knowledge, this is the first pharmacophore model that has a selective feature for a “zinc binding group” which has been customized within the structure-based pharmacophore model of Glo-1 to extract ligands that possess functional groups able to bind zinc atom solely from database screening. In addition, an extensive 2D similarity search using three diverse similarity techniques (Tanimoto, Dice, Cosine) has been performed over the commercially available “Zinc Clean Drug-Like Database” that contains around 10 million compounds to help find suitable inhibitors for this enzyme based on known inhibitors from the literature. The resultant hits were mapped over the structure based pharmacophore and the successful hits were further docked using three docking programs with different pose fitting and scoring techniques (GOLD, LibDock, CDOCKER). Nine candidates were suggested to be novel Glo-1 inhibitors containing the “zinc binding group” with the highest consensus scoring from docking.

Background: The glyoxalase system including two thiol-dependent enzymes, glyoxalase I (Glo-I) and glyoxalase II, plays an important role in a ubiquitous metabolic pathway involved in cellular detoxification of cytotoxic 2-oxoaldehydes. Tumor cells have high glycolytic activity, leading to increased cellular levels of these toxic metabolites. The increased activity of the detoxification system in cancerous cells makes this pathway a viable target for developing novel anticancer agents. In this study, we examined the potential utility of non-glutathione-based inhibitors of the Glo-I enzyme as novel anticancer drugs. Methods: Computer-aided drug design techniques, such as customized pharmacophoric features, virtual screening, and flexible docking, were used to achieve the project goals. Retrieved hits were extensively filtered and subsequently docked into the active site of the enzyme. The biological activities of retrieved hits were assessed using an in vitro assay against Glo-I. Results: Since Glo-I is a zinc metalloenzyme, a customized Zn-binding pharmacophoric feature was used to search for selective inhibitors via virtual screening of a small-molecule database. Seven hits were selected, purchased, and biologically evaluated. Three of the seven hits inhibited Glo-I activity, the most effective of which exerted 76.4% inhibition at a concentration of 25 µM. Conclusion: We successfully identified a potential Glo-I inhibitor that can serve as a lead compound for further optimization. Moreover, our in silico and experimental results were highly correlated. Hence, the docking protocol adopted in this study may be efficiently employed in future optimization steps.