Hydrocarbon staple constructing highly efficient α-helix cell-penetrating peptides for intracellular cargo delivery

Palindromic peptide foldamers: a strategy for structural stability and cellular uptake

Mid-sized peptide therapeutics have gained significant attention for their potential to overcome the limitations of small molecules and biologics. However, their clinical application is often hindered by poor stability and low cellular permeability. In this study, we designed a palindromic peptide foldamer composed of L-leucine and L-arginine residues to investigate its structural and functional properties. CD spectroscopy confirmed that the designed peptide adopts a stable α-helical conformation, even under denaturing conditions. Cellular uptake studies using LC-MS/MS and flow cytometry indicated efficient intracellular delivery, suggesting that the peptide's amphiphilic structure enhances membrane permeability. These findings provide valuable insights into the rational design of structurally stable and functionally enhanced peptide therapeutics.

De Novo Engineering of Pd-Metalloproteins and Their Use as Intracellular Catalysts

The development of transition metal-based catalytic platforms that promote bioorthogonal reactions inside living cells remains a major challenge in chemical biology. This is particularly true for palladium-based catalysts, which are very powerful in organic synthesis but perform poorly in the cellular environment, mainly due to their rapid deactivation. We now demonstrate that grafting Pd(II) complexes into engineered β-sheets of a model WW domain results in cell-compatible palladominiproteins that effectively catalyze depropargylation reactions inside HeLa cells. The concave shape of the WW domain β-sheet proved particularly suitable for accommodating the metal center and protecting it from rapid deactivation in the cellular environment. A thorough NMR and computational study confirmed the formation of the metal-stapled peptides and allowed us to propose a three-dimensional structure for this novel metalloprotein motif.

Innovative peptide architectures: advancements in foldamers and stapled peptides for drug discovery

INTRODUCTION

Peptide foldamers play a critical role in pharmaceutical research and biomedical applications. This review highlights recent (post-2020) advancements in novel foldamers, synthetic techniques, and their applications in pharmaceutical research.

AREAS COVERED

The authors summarize the structures and applications of peptide foldamers such as α, β, γ-peptides, hydrocarbon-stapled peptides, urea-type foldamers, sulfonic-γ-amino acid foldamers, aromatic foldamers, and peptoids, which tackle the challenges of traditional peptide drugs. Regarding antimicrobial use, foldamers have shown progress in their potential against drug-resistant bacteria. In drug development, peptide foldamers have been used as drug delivery systems (DDS) and protein-protein interaction (PPI) inhibitors.

EXPERT OPINION

These structures exhibit resistance to enzymatic degradation, are promising for therapeutic delivery, and disrupt crucial PPIs associated with diseases such as cancer with specificity, versatility, and stability, which are useful therapeutic properties. However, the complexity and cost of their synthesis, along with the necessity for thorough safety and efficacy assessments, necessitate extensive research and cross-sector collaboration. Advances in synthesis methods, computational modeling, and targeted delivery systems are essential for fully realizing the therapeutic potential of foldamers and integrating them into mainstream medical treatments.

Development of a Decafluorobiphenyl Cyclized Peptide Targeting the NEMO-IKKα/β Interaction that Enhances Cell Penetration and Attenuates Lipopolysaccharide-Induced Acute Lung Injury

Aberrant canonical NF-κB signaling has been implicated in diseases, such as autoimmune disorders and cancer. Direct disruption of the interaction of NEMO and IKKα/β has been developed as a novel way to inhibit the overactivation of NF-κB. Peptides are a potential solution for disrupting protein-protein interactions (PPIs); however, they typically suffer from poor stability in vivo and limited tissue penetration permeability, hampering their widespread use as new chemical biology tools and potential therapeutics. In this work, decafluorobiphenyl-cysteine SNAr chemistry, molecular modeling, and biological validation allowed the development of peptide PPI inhibitors. The resulting cyclic peptide specifically inhibited canonical NF-κB signaling in vitro and in vivo, and presented positive metabolic stability, anti-inflammatory effects, and low cytotoxicity. Importantly, our results also revealed that cyclic peptides had huge potential in acute lung injury (ALI) treatment, and confirmed the role of the decafluorobiphenyl-based cyclization strategy in enhancing the biological activity of peptide NEMO-IKKα/β inhibitors. Moreover, it provided a promising method for the development of peptide-PPI inhibitors.

Membrane-Active All-Hydrocarbon-Stapled α-Helical Amphiphilic Tat Peptides: Broad-Spectrum Antibacterial Activity and Low Incidence of Drug Resistance

Multidrug resistance against conventional antibiotics has dramatically increased the difficulty of treatment and accelerated the need for novel antibacterial agents. The peptide Tat (47-57) is derived from the transactivating transcriptional activator of human immunodeficiency virus 1, which is well-known as a cell-penetrating peptide in mammalian cells. However, it is also reported that the Tat peptide (47-57) has antifungal activity. In this study, a series of membrane-active hydrocarbon-stapled α-helical amphiphilic peptides were synthesized and evaluated as antibacterial agents against Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. The impact of hydrocarbon staple, the position of aromatic amino acid residue in the hydrophobic face, the various types of aromatic amino acids, and the hydrophobicity on bioactivity were also investigated and discussed in this study. Among those synthesized peptides, analogues P3 and P10 bearing a l-2-naphthylalanine (Φ) residue at the first position and a Tyr residue at the eighth position demonstrated the highest antimicrobial activity and negligible hemolytic toxicity. Notably, P3 and P10 showed obviously enhanced antimicrobial activity against multidrug-resistant bacteria, low drug resistance, high cell selectivity, extended half-life in plasma, and excellent performance against biofilm. The antibacterial mechanisms of P3 and P10 were also preliminarily investigated in this effort. In conclusion, P3 and P10 are promising antimicrobial alternatives for the treatment of the antimicrobial-resistance crisis.

Liposome Deformation Induced by Membrane-Binding Peptides

This paper presents an investigation of liposome deformation and shape distortion using four membrane-binding peptides: TAT and C105Y as cell-penetrating peptides (CPPs), and melittin and ovispirin as antimicrobial peptides (AMPs). Liposome deformation was monitored utilizing fluorescent microscopy, while the binding of peptides to the DOPC membrane was estimated through capacitance measurements. The degree of liposome deformation and shape distortion was found to be higher for the CPPs compared to the AMPs. Additionally, it was observed that C105Y did not induce liposome rupture, unlike the other three peptides. We propose that these variations in liposome distortion may be attributed to differences in secondary structure, specifically the presence of an α-helix or random coil. Our studies offer insight into the use of peptides to elicit control of liposome architecture and may offer a promising approach for regulating the bodies of liposomal molecular robots.

Peptide-Based Supramolecular Hydrogels as Drug Delivery Agents: Recent Advances

Supramolecular peptide hydrogels have many important applications in biomedicine, including drug delivery applications for the sustained release of therapeutic molecules. Targeted and selective drug administration is often preferential to systemic drug delivery, as it can allow reduced doses and can avoid the toxicity and side-effects caused by off-target binding. New discoveries are continually being reported in this rapidly developing field. In this review, we report the latest developments in supramolecular peptide-based hydrogels for drug delivery, focusing primarily on discoveries that have been reported in the last four years (2018-present). We address clinical points, such as peptide self-assembly and drug release, mechanical properties in drug delivery, peptide functionalization, bioadhesive properties and drug delivery enhancement strategies, drug release profiles, and different hydrogel matrices for anticancer drug loading and release.

Application of the All-Hydrocarbon Stapling Technique in the Design of Membrane-Active Peptides

The threats of drug resistance and new emerging pathogens have led to an urgent need to develop alternative treatment therapies. Recently, considerable research efforts have focused on membrane-active peptides (MAPs), a category of peptides in drug discovery with antimicrobial, anticancer, and cell penetration activities that have demonstrated their potential to be multifunctional agents. Nonetheless, natural MAPs have encountered various disadvantages, which mainly include poor bioavailability, the lack of a secondary structure in short peptides, and high production costs for long peptide sequences. Hence, an "all-hydrocarbon stapling system" has been applied to these peptides and proven to effectively stabilize the helical conformations, improving proteolytic resistance and increasing both the potency and the cell permeability. In this review, we summarized and categorized the advances made using this powerful technique in the development of stapled MAPs. Furthermore, outstanding issues and suggestions for future design within each subcategory were thoroughly discussed.