Anticancer Properties of Lipidated Peptide Drug Supramolecular Self-Assemblies with Enhanced Stability

Cholesterol as an inbuilt immunoadjuvant for a lipopeptide vaccine against group A Streptococcus infection

Peptide-based vaccines can trigger highly specific immune responses, although peptides alone are usually unable to confer strong humoral or cellular immunity. Consequently, peptide antigens are administered with immunostimulatory adjuvants, but only a few are safe and effective for human use. To overcome this obstacle, herein a peptide antigen was lipidated to effectively anchor it to liposomes and emulsion. A peptide antigen B cell epitope from Group A Streptococcus M protein was conjugated to a universal T helper epitope, the pan DR-biding epitope (PADRE), alongside a lipidic moiety cholesterol. Compared to a free peptide antigen, the lipidated version (LP1) adopted a helical conformation and self-assembled into small nanoparticles. Surprisingly, LP1 alone induced the same or higher antibody titers than liposomes or emulsion-based formulations. In addition, antibodies produced by mice immunized with LP1 were more opsonic than those induced by administering the antigen with incomplete Freund's adjuvant. No side effects were observed in the immunized mice and no excessive inflammatory immune responses were detected. Overall, this study demonstrated how simple conjugation of cholesterol to a peptide antigen can produce a safe and efficacious vaccine against Group A Streptococcus - the leading cause of superficial infections and the bacteria responsible for deadly post-infection autoimmune disorders.

Designing Peptide-Based Nanoinhibitors of Programmed Cell Death Ligand 1 (PD-L1) for Enhanced Chemo-immunotherapy

The combination of immune checkpoint blockade (ICB) and chemotherapy has shown significant potential in the clinical treatment of various cancers. However, circulating regeneration of PD-L1 within tumor cells greatly limits the efficiency of chemo-immunotherapy and consequent patient response rates. Herein, we report the synthesis of a nanoparticle-based PD-L1 inhibitor (FRS) with a rational design for effective endogenous PD-L1 suppression. The nanoinhibitor is achieved through self-assembly of fluoroalkylated competitive peptides that target PD-L1 palmitoylation. The FRS nanoparticles provide efficient protection and delivery of functional peptides to the cytoplasm of tumors, showing greater inhibition of PD-L1 than nonfluorinated peptidic inhibitors. Moreover, we demonstrate that FRS synergizes with chemotherapeutic doxorubicin (DOX) to boost the antitumor activities via simultaneous reduction of PD-L1 abundance and induction of immunogenic cell death in murine colon tumor models. The nano strategy of PD-L1 regulation present in this study is expected to advance the development of ICB inhibitors and overcome the limitations of conventional ICB-assisted chemo-immunotherapy.

Fatty acid modification of casein bioactive peptides nano-assemblies, synthesis, characterization and anticarcinogenic effect

In this study, the nano-assemblies of bovine casein hydrolyzed peptides (HP) modified by fatty acids with various alkyl chain lengths (C8, C10, C12 and C14) were synthesized. The physicochemical properties of HP-C8-HP-C14 nano-assemblies were characterized using spectra, laser particle size analyzer, contact angle meter, scanning electron microscope (SEM) and cryo-transmission electron microscope (Cryo-TEM). HP-C8 and HP-C10 self-assembled into a hollow cube cage with an average size of ~500 nm, and the assembly of HP-C12 showed a flower-shaped morphology with more dispersed behavior, and droplet size was observed as ~20 nm. The in vitro cytotoxicity against human breast cancer cells MCF-7 was tested using CCK-8 assay and flow cytometry analysis. HP-C12 showed the highest cytotoxicity for MCF-7 cells with an inhibition rate of 66.03 % ± 0.35 % with an IC50 value of 7.4 μM among HP-Cn. HP-C8, HP-C10 and HP-C12 significantly affected on the migration, invasion and apoptosis of MCF-7 cells. The apoptosis mechanism may depend on the upregulation of anti-apoptotic protein Bcl-2 as well as pro-apoptotic proteins Bax and caspase-8. The dead MCF-7 cells were analyzed with UHPLC-MS/MS using untargeted metabolomics, revealing key metabolic pathways.

Electrostatically Controlled ex Situ and in Situ Polymerization of Diacetylene-Containing Peptide Amphiphiles in Living Cells

Precise control of diacetylene-containing peptide amphiphile (DPA) based supramolecular architectures is important for their in cellulo polymerization behaviors and biomedical applications. Herein, we reported two DPAs (cationic PA-NH₂ and zwitterionic PA-OH) with a similar molecular structure, which exhibited completely opposite polymerization behaviors in aqueous solution and living cells. Specifically, PA-NH₂ was unpolymerizable in aqueous solution but underwent in cellulo polymerization to respond to the intracellular microenvironment. On the contrary, zwitterionic PA-OH was polymerized in solution, rather than inside living cells. Based on the results of cell viability and total internal reflection fluorescent microscopy measurement, PA-OH exhibited higher affinity with cell membranes and lower cytotoxicity than those of PA-NH₂. Therefore, it is suggested that the in cellulo polymerization of PA-NH₂ should be responsive for greater cytotoxicity, rather than the membrane affinity. This study provides an in-depth understanding of the role of charge properties in the polymerization behavior of DPAs and seeks their potential biomedical applications.

Therapeutic peptides for chemotherapy: Trends and challenges for advanced delivery systems

The past decades witnessed an increasing interest in peptides as clinical therapeutics. Rightfully considered as a potential alternative for small molecule therapy, these remarkable pharmaceuticals can be structurally fine-tuned to impact properties such as high target affinity, selectivity, low immunogenicity along with satisfactory tissue penetration. Although physicochemical and pharmacokinetic challenges have mitigated, to some extent, the clinical applications of therapeutic peptides, their potential impact on modern healthcare remains encouraging. According to recent reports, there are more than 400 peptides under clinical trials and 60 were already approved for clinical use. As the demand for efficient and safer therapy became high, especially for cancers, peptides have shown some exciting developments not only due to their potent antiproliferative action but also when used as adjuvant therapies, either to decrease side effects with tumor-targeted therapy or to enhance the activity of anticancer drugs via transbarrier delivery. The first part of the present review gives an insight into challenges related to peptide product development. Both molecular and formulation approaches intended to optimize peptide's pharmaceutical properties are covered, and some of their current issues are highlighted. The second part offers a comprehensive overview of the emerging applications of therapeutic peptides in chemotherapy from bioconjugates to nanovectorized therapeutics.

Challenges of peptide and protein drug delivery by oral route: Current strategies to improve the bioavailability

Advancement in biotechnology provided a notable expansion of peptide and protein therapeutics, used as antigens, vaccines, hormones. It has a prodigious potential to treat a broad spectrum of diseases such as cancer, metabolic disorders, bone disorders, and so forth. Protein and peptide therapeutics are administered parenterally due to their poor bioavailability and stability, restricting their use. Hence, research focuses on the oral delivery of peptides and proteins for the ease of self-administration. In the present review, we first address the main obstacles in the oral delivery system in addition to approaches used to enhance the stability and bioavailability of peptide/protein. We describe the physiochemical parameters of the peptides and proteins influencing bioavailability in the systemic circulation. It encounters, many barriers affecting its stability, such as poor cellular membrane permeability at the GIT site, enzymatic degradation (various proteases), and first-pass hepatic metabolism. Then describe the current approaches to overcome the challenges mentioned above by the use of absorption enhancers or carriers, structural modification, formulation and advance technology.

Recent Advances in Late-Stage Construction of Stapled Peptides via C-H Activation

Stapled peptides have been widely applied in many fields, including pharmaceutical chemistry, diagnostic reagents, and materials science. However, most traditional stapled peptide preparation methods rely on prefunctionalizations, which limit the diversity of stapled peptides. Recently, the emergence of late-stage transition metal-catalyzed C-H activation in amino acids and peptides has attracted wide interest due to its robustness and applicability for peptide stapling. In this review, we summarize the methods for late-stage construction of stapled peptides via transition metal-catalyzed C-H activation.

pH-Responsive Self-Assemblies from the Designed Folic Acid-Modified Peptide Drug for Dual-Targeting Delivery

Targeting delivery is a promising technique for the therapy of cancers. A molecule FA-EEYSV-NH₂, which consists of target recognition site folic acid (FA), dipeptide linker, and peptide drug, was designed as a novel anticancer prodrug. The molecules could self-assemble into nanoparticles at pH 7.0 and nanofibers at pH 5.0. By the aid of pH-responsiveness, the self-assemblies were used purposefully as targeted vehicles of self-delivery prodrugs. The results of cell toxicity and internalization assays have proved that the self-assemblies have good cancer cell selectivity. The selection was mainly attributed to the pH-responsive structure transition of self-assemblies and the FA active-targeting effect. We hope that our work could provide a useful strategy for finely tuning the properties and activities of peptide-based supramolecular nanomaterials, thus optimizing nanomedicines with enhanced performance.

Palmitoylation of Membrane-Penetrating Magainin Derivatives Reinforces Necroptosis in A549 Cells Dependent on Peptide Conformational Propensities

Anticancer lipopeptides (ACLPs) are considered promising alternatives to combat resistant cancer cells, but the influence of peptide conformational propensity alone on their selectivity and mechanism remains obscure. In this study, we developed N-palmitoylated MK5E (P1MK5E) and MEK5 (P1MEK5) that have the same composition of 23 residues undergoing the pH-dependent structural alterations but differ in the conformational tendency of their amino acid composites. Nonlipidated peptides were readily accumulated in the A549 cell nucleus by the direct membrane translocation and the heparan sulfate-mediated endocytosis than the lipid-raft-dependent pathway. The increased hydrophobicity favored the amino acid-position-dependent folding of P1MK5E and P1MEK5, respectively, toward the α-helical coiled-coil nanofibrils and amyloidlike β-protofibrils. At the close concentrations (∼7.5 μM) to the toxic effects of doxorubicin (DOX), P1MK5E exhibited (i) an increased anticancer toxicity through a time-dependent S-phase arrest, (ii) enhanced plasma membrane permeability, and (iii) dose-dependent changes in the cell death characteristic features in the A549 cells relative to P1MEK5 that was almost inactive at ∼75 μM. These observations were in accordance with the TNF-α-mediated necroptotic signaling in the c-MYC/PARP1-overexpressed A549 cells exposed to P1MK5E and accompanied by the ultrastructure of plasma membrane protrusions, extensive endoplasmic reticulum (ER) membrane expansion, mitochondrial swelling, and the formation of distinct cytoplasmic vacuolation. The structural results and the bioactivity behaviors, herein, declared the significance of α-helical propensity in the peptide sequence and the nanostructure morphologies of self-assembling ACLPs upon the selectivity and enhanced anticancer effectiveness, which notably holds promise in the design and development of efficient therapeutics for cancer.

Low molecular weight self-assembling peptide-based materials for cell culture, antimicrobial, anti-inflammatory, wound healing, anticancer, drug delivery, bioimaging and 3D bioprinting applications

In this review, we have focused on the design and development of low molecular weight self-assembling peptide-based materials for various applications including cell proliferation, tissue engineering, antibacterial, antifungal, anti-inflammatory, anticancer, wound healing, drug delivery, bioimaging and 3D bioprinting. The first part of the review describes about stimuli and various noncovalent interactions, which are the key components of various self-assembly processes for the construction of organized structures. Subsequently, the chemical functionalization of the peptides has been discussed, which is required for the designing of self-assembling peptide-based soft materials. Various low molecular weight self-assembling peptides have been discussed to explain the important structural features for the construction of defined functional nanostructures. Finally, we have discussed various examples of low molecular weight self-assembling peptide-based materials for cell culture, antimicrobial, anti-inflammatory, anticancer, wound healing, drug delivery, bioimaging and 3D bioprinting applications.