Synthesis and antibacterial study of cell-penetrating peptide conjugated trifluoroacetyl and thioacetyl lysine modified peptides

Multi-targeted nanogel drug delivery system alleviates neuroinflammation and promotes spinal cord injury repair

Spinal cord injury (SCI) is significantly hampered by an inflammatory microenvironment, prompting continued efforts in drug development to address inflammation. Research shows that quercetin (Que) exhibits excellent performance in reducing inflammation and neuroprotection. However, its application is limited by poor solubility, notable side effects, and the unique pathophysiology of the spinal cord. In this study, we introduce a novel multifunctional liposome hydrogel drug delivery system (QLipTC@HDM), obtained by incorporating liposomes with blood-spinal cord barrier penetration and injury site targeting properties (LipTC) into a dual-network viscous hydrogel (HDM). Our results demonstrate that encapsulating Que in LipTC (QLipTC) enhances solubility, minimizes toxic side effects, facilitates lesion targeting, and aids in crossing the blood-spinal cord barrier. Moreover, encapsulation in HDM significantly prolongs the retention of QLipTC at the injury site after local administration. Crucially, our findings reveal that QLipTC@HDM induces M2 phenotype transformation in glial cells and in mice with SCI, thereby mitigating inflammation. This intervention additionally preserves the integrity of the blood-spinal cord barrier, optimizes the spinal cord microenvironment, reduces glial scarring, promotes axonal regeneration, and enhances motor function recovery in SCI mice. In summary, our investigations highlight the potential of this disease-specific drug delivery system as a promising therapeutic approach for the treatment and management of SCI.

Cell Penetrating Peptides: Classification, Mechanisms, Methods of Study, and Applications

Cell-penetrating peptides (CPPs) encompass a class of peptides that possess the remarkable ability to cross cell membranes and deliver various types of cargoes, including drugs, nucleic acids, and proteins, into cells. For this reason, CPPs are largely investigated in drug delivery applications in the context of many diseases, such as cancer, diabetes, and genetic disorders. While sharing this functionality and some common structural features, such as a high content of positively charged amino acids, CPPs represent an extremely diverse group of elements, which can differentiate under many aspects. In this review, we summarize the most common characteristics of CPPs, introduce their main distinctive features, mechanistic aspects that drive their function, and outline the most widely used techniques for their structural and functional studies. We highlight current gaps and future perspectives in this field, which have the potential to significantly impact the future field of drug delivery and therapeutics.

Functionalized antibacterial peptide with DNA cleavage activity for enhanced bacterial disinfection

Antibiotics are commonly used to treat bacterial infections, but the misuse and abuse of antibiotics have given rise to a severe problem of the drug resistance of bacteria. Solving this problem has been a vitally important task in the modern medical arena. Antibacterial peptide (AMPs) has become a promising candidate drug to replace antibiotics because of their broad-spectrum antibacterial activity and their difficulty in making bacteria resistant. However, its wider clinical application is limited by the shortcomings of high cytotoxicity and low antibacterial efficiency. In this paper, we constructed an antibacterial peptide (Cu-GGH-KKLRKIAFK, abbreviated as Cu-GGH-AMP) with a DNA cleavage function. The peptide has two functional regions, the C-terminal antibacterial peptide PaDBS1R6F10 (KKLRLKIAFK) and the N-terminal Cu-GGH complex. PaDBS1R6F10 is a unique antibacterial peptide, which shows lower tendency to produce bacterial resistance than traditional antibiotics. Cu-GGG complexes are formed by chelating Cu with the classical amino terminal Cu (II)- and Ni (II) -Binding (ATCUN) motif GGH. In the presence of ascorbic acid, Cu-GGH can efficiently catalyze the oxidative cleavage of bacterial DNA, thus playing a synergistic antibacterial role with antibacterial peptides. The in vitro and in vivo experiments demonstrated this functionalized antibacterial peptide possesses excellent antibacterial and anti-skin infection capability, as well as the activity of promoting wound healing.

Synergy between Human Peptide LL-37 and Polymyxin B against Planktonic and Biofilm Cells of Escherichia coli and Pseudomonas aeruginosa

The rise in antimicrobial resistant bacteria is limiting the number of effective treatments for bacterial infections. Escherichia coli and Pseudomonas aeruginosa are two of the pathogens with the highest prevalence of resistance, and with the greatest need for new antimicrobial agents. Combinations of antimicrobial peptides (AMPs) and antibiotics that display synergistic effects have been shown to be an effective strategy in the development of novel therapeutic agents. In this study, we investigated the synergy between the AMP LL-37 and various classes of antibiotics against E. coli and P. aeruginosa strains. Of the six antibiotics tested (ampicillin, tetracycline, ciprofloxacin, gentamicin, aztreonam, and polymyxin B (PMB)), LL-37 displayed the strongest synergy against E. coli MG1655 and P. aeruginosa PAO1 laboratory strains when combined with PMB. Given the strong synergy, the PMB + LL-37 combination was chosen for further examination where it demonstrated synergy against multidrug-resistant and clinical E. coli isolates. Synergy of PMB + LL-37 towards clinical isolates of P. aeruginosa varied and showed synergistic, additive, or indifferent effects. The PMB + LL-37 combination treatment showed significant prevention of biofilm formation as well as eradication of pre-grown E. coli and P. aeruginosa biofilms. Using the Galleria mellonella wax worm model, we showed that the PMB + LL-37 combination treatment retained its antibacterial capacities in vivo. Flow analyses were performed to characterize the mode of action. The results of the present study provide proof of principle for the synergistic response between LL-37 and PMB and give novel insights into a promising new antimicrobial combination against gram-negative planktonic and biofilm cells.

Antimicrobial and Cell-Penetrating Peptides: Understanding Penetration for the Design of Novel Conjugate Antibiotics

Antimicrobial peptides (AMPs) are short oligopeptides that can penetrate the bacterial inner and outer membranes. Together with cell-penetrating peptides (CPPs), they are called membrane active peptides; peptides which can translocate across biological membranes. Over the last fifty years, attempts have been made to understand the molecular features that drive the interactions of membranes with membrane active peptides. This review examines the features of a membrane these peptides exploit for translocation, as well as the physicochemical characteristics of membrane active peptides which are important for translocation. Moreover, it presents examples of how these features have been used in recent years to create conjugates consisting of a membrane active peptide, called a "vector", attached to either a current or novel antibiotic, called a "cargo" or "payload". In addition, the review discusses what properties may contribute to an ideal peptide vector able to deliver cargoes across the bacterial outer membrane as the rising issue of antimicrobial resistance demands new strategies to be employed to combat this global public health threat.