Search Results (256)

Approximately 30% of tumors contain an activating mutation in the oncogene KRAS, leading to increased cell proliferation that often promotes non-small cell lung cancers, colorectal adenocarcinomas, pancreatic ductal adenocarcinomas (PDAC), and other cancers. Among the most common point mutations in KRAS is G12D, an example of an oncogenic sequence present in tumor cells but not normal cells. We developed peptide nucleic acid (PNA) oligomers that selectively bind KRAS G12D sequences and fused them with novel cell-penetrating peptide flanking regions (CPP-PNA-G12D) then evaluated them. Electrophoretic mobility shift assays demonstrated in vitro binding to and selectivity for KRAS G12D over wild-type KRAS and KRAS G12C. Cells and nuclei were able to uptake CPP-PNA-G12D at high efficiency as shown by fluorescent microscopy and flow cytometry. Cell viability assays showed a striking dose-response effect in on-target cells expressing KRAS G12D, while relatively sparing off-target cells expressing KRAS G12C. CPP-PNA-G12D constructs were effective against a panel of PDAC cell lines and in female Balb/c mice bearing patient-derived xenografts. These results show promise for an enhanced PNA-delivery peptide conjugate strategy as a potential therapeutic strategy to selectively target KRAS mutant cancer cells, with the potential to expand this technology to additional cancer-derived mutant oncogenes. Full article

The intracellular delivery of large macromolecules remains a significant challenge in both therapeutic and research contexts. This study investigates two novel chimeric cell-penetrating peptides, Nucleolaron1511 (Nuc1511) and Nucleolaron1510 (Nuc1510), with the aim of evaluating their capacities to deliver the fluorescent protein Azami Green (AG) into HeLa cells via genetic fusion. Cellular uptake of TAMRA-labeled Nuc1510 was assessed by fluorescence microscopy at multiple time points. Delivery efficiency of AG–Nuc1511 and AG–Nuc1510 fusion proteins was evaluated by fluorescence microscopy and flow cytometry, and cytotoxicity was assessed across a range of concentrations using the MTT assay. TAMRA–Nuc1510 successfully penetrated HeLa cells within one hour of treatment, with signal detected in both cytoplasmic and nuclear compartments. Flow cytometry quantification revealed that fusion with Nuc1511 increased intracellular AG fluorescence by over 80-fold relative to unconjugated AG, while Nuc1510 fusion yielded approximately a 9-fold increase. Neither peptide exhibited significant cytotoxicity at concentrations used in the delivery assays. These findings establish Nuc1511 and Nuc1510 as effective CPPs capable of facilitating intracellular protein delivery via genetic fusion, with favorable safety profiles, representing promising candidates for protein-based intracellular delivery in research and therapeutic applications. Full article

Skin barrier dysfunction and pruritus, central to inflammatory dermatoses, are closely associated with impaired epidermal structural proteins and persistent inflammatory signaling. To address these pathological features, this study aimed to explore the potential anti-inflammatory, barrier-restorative, and anti-pruritic effects of DualPep-ATO, a human-derived cell-penetrating peptide (CPP), using integrated in vitro, ex vivo, and exploratory clinical approaches. Allergic and inflammatory responses were evaluated in rat basophilic leukemia cells and lipopolysaccharide-stimulated macrophages, while barrier-repair properties were partially assessed in ultraviolet B (UVB)-irradiated human epidermal keratinocytes and ex vivo human skin tissue. Mechanistically, DualPep-ATO exhibited no cytotoxicity and successfully suppressed β-hexosaminidase release, nitric oxide production, and pro-inflammatory cytokine expression. Furthermore, it contributed to mitigating skin barrier damage by restoring key epidermal structural proteins, specifically filaggrin, loricrin, and involucrin. Translating these findings clinically, a four-week topical application of a DualPep-ATO cream in adults with compromised skin significantly decreased transepidermal water loss and itch severity. With high participant satisfaction and no reported adverse events, this peptide may serve as a promising peptide-based topical strategy for inflammatory skin conditions associated with barrier dysfunction and pruritus. Full article

Background/Objectives: Longer oligoarginines are very effective cell-penetrating peptides. It has been shown that a minimal number of positively charged side chains is necessary for efficient cellular uptake. But a highly positively charged peptide may interact with its cargo molecule, thereby reducing its efficiency. Several chemical modifications were tested to improve the internalization of short tetraarginine derivatives. Aromatic groups, such as Dabcyl at the N-terminus, Trp in the sequence, and AMBA or PABA in the backbone, were used to improve internalization. The other useful modification was the aza-glycine substitution in the case of penetratin. Methods: In this study, the effect of aza-glycine insertion into the peptide Dabcyl-RRRRK(Cf) on internalization was studied and compared with that of the Trp-modified peptide Dabcyl-RRWRRK(Cf). To explain the noticed difference in the biological activity of peptides, DFT calculations and the prediction of membrane-binding free energy (ΔΔF) from a peptide sequence were performed. Results: It turned out that the position of the aza-glycine moiety does not have an influence on the cellular uptake. The aza-glycine-containing peptide showed higher internalization than the Dabcyl-RRRRK(Cf) peptide. Besides this, these peptides have similar or higher cellular uptake than that of octaarginine at lower concentrations (c < 2 µM). The aza-glycine affected not only cellular uptake but also the entry mechanism. The structure of peptides depended on the amino acids (Trp, Gly, or azaGly) in their sequences and their positions. Conclusions: These may result in the different amphiphilicity of peptides, and thus changes in the hydrophobic moment and in the binding affinity of peptides to the negatively charged membrane surface. Full article

Background/Objectives: Investigating the modified derivatives of known cell-penetrating peptides can highlight the important residues in the peptide sequence and help understand the cellular uptake mechanism better. Moreover, comparing peptides with different fluorescent-dye positions can highlight the importance of the conjugation site. Earlier, it was demonstrated that the fluorescence quencher 4-((4-(dimethylamino)phenyl)azo)benzoyl (Dabcyl) group can enhance the internalization efficiency of highly cationic oligoarginine peptides. However, its effect in the case of arginine-rich penetratin, a secondary amphipathic cationic CPP, remains undiscovered. Methods: Here, several penetratin derivatives were studied in which the aromatic residues were substituted and the effect of Dabcyl modification was also studied on the cellular uptake of peptides by flow cytometry. Results: The triple Nal-substituted penetratin and dodeca-penetratin with N-terminally positioned carboxyfluoresein (Cf) dye demonstrated remarkable internalization efficiency compared to penetratin. Moreover, almost all the Dabcyl-modified peptides were superior to penetratin except two peptides with C-terminal Cf-labelling. This result highlights the importance of the structure of the conjugate. The position of the cargo molecule may have a high impact on internalization ability. The relatively low cellular uptake of the Trp48 residue-substituted Dabcyl-Pen12 points to the importance of this residue in the cellular uptake of dodeca-penetratin. The confocal microscopic studies revealed that, besides the greater penetration efficiency of Dabcyl penetratin derivatives, these peptides enter the cytoplasm of cells in an increased manner. Conclusions: We identified several intriguing derivatives and expanded the applicability of Dabcyl, while also highlighting its limitations. Additionally, the critical role of Trp48 in the penetratin sequence was reaffirmed, along with the importance of the fluorescent molecule’s position. Full article

Peptide therapeutics occupy a unique chemical space between small molecules and biologics, combining high target specificity with structural programmability and favorable safety profiles. Recent regulatory approvals and expanding clinical pipelines underscore the growing therapeutic and commercial relevance of peptide-based drugs. This review outlines chemical modification approaches and contemporary design strategies, and evaluates their impact on proteolytic stability, pharmacokinetics, membrane permeability, and target engagement. We then highlight recent advances in artificial intelligence (AI)-guided peptide drug design, including machine learning models, protein language models, and generative architectures that enable high-throughput activity prediction, property optimization, and de novo sequence generation. These approaches collectively accelerate the traditional discovery–design–validation cycle while reducing experimental attrition through data-driven, structure-informed modeling frameworks. Among these applications, AI also enables the rational design of cell-penetrating peptides (CPPs) to enhance intracellular delivery and biological activity. Building on these methodological advances, we further examine their application to peptide therapeutics, with particular emphasis on AI-based predictive models for CPPs as well as on therapeutic applications within the central nervous and pulmonary systems. We conclude by outlining future perspectives and emphasize that the systematic integration of AI-enabled sequence design with rational chemical engineering and advanced delivery technologies, supported by rigorous experimental validation, will be critical for developing robust and clinically durable peptide-based medicines. Full article

Cell-penetrating peptide (CPP) conjugation represents a promising strategy for enhancing the biological activity of therapeutic peptides. In this study, three analogues were designed by conjugating the trypsin inhibitory loop (TIL) derived from a Bowman–Birk-type inhibitor with the transactivator of transcription (TAT) peptide to improve their bioactivity. All TAT-TIL conjugates exhibited significantly enhanced antimicrobial activity compared with the parent peptide. Notably, the analogue containing a glycine linker (-GG-) showed further improvement in antiproliferative activity against cancer cells, indicating the potential role of linker design in optimizing peptide function. All analogues exhibited low hemolytic activity at the highest tested concentrations, although increased cytotoxicity toward normal HaCaT cells was observed, suggesting the need for further optimization of selectivity. Interestingly, comparable antimicrobial activities were observed regardless of protease inhibitory capacity, indicating that protease inhibition is not essential for the enhanced biological effects. Overall, TAT conjugation significantly improves the biological activity of Bowman–Birk-type inhibitor-derived peptides, and the incorporation of a glycine linker further enhances their functional properties. These findings support CPP-mediated peptide modification as an effective strategy for developing potential antimicrobial and anticancer peptide candidates. Full article

Adeno-associated viruses (AAVs) are a promising gene therapy technology, but major technical challenges remain. One problem is that commonly used AAVs have a low efficiency in penetrating the blood–brain barrier (BBB) and the blood–retina barrier (BRB). Consequently, gene delivery to the nervous system has limitations. Another problem is that AAVs induce immune reactions that cause serious side effects. To avoid immune reactions, the AAV dose must be reduced to lower levels that may result in insufficient gene delivery. Researchers have been modifying viral capsid protein sequences and searching for effective peptide sequences to solve these problems. As a result, Cell-Penetrating Penta-Peptides (CPP5s) have been shown to be effective in improving the BBB/BRB penetration of AAVs and suppressing immune reactions against AAVs. CPP5s were originally developed from peptide sequences of the Bax (a pro-apoptotic protein) binding domain of Ku70 (a DNA repair protein) and from negative control cell-penetrating peptides without Bax-binding activity. This article will discuss the background science of CPP5s and future directions of CPP5s for AAV-mediated gene delivery to the nervous system as well as other organs. Full article

Skeletal muscle is the largest metabolic demanding organ in human body. Alterations of skeletal muscle in shape and size significantly affect its biological functions. Botulinum neurotoxin type A1 (BoNT/A1) has been successfully used in clinics to treat masseter, trapezius and gastrocnemius hypertrophy. Here, we used a healthy rat-based skeletal muscle hypertrophy model to evaluate the muscle-reducing activity of recombinant BoNT/A1 (rBoNT/A1) with genetically fused cell-penetrating peptides (CPPs), which was previously reported to increase the cellular uptake of BoNT/A1. Analyses of treated muscle sections using hematoxylin–eosin and immunofluorescence staining showed that both wild-type rBoNT/A1 without modification (WT-rBoNT/A1) and rBoNT/A1 with CPP fusion (CPP-rBoNT/A1) could induce myocomma atrophy and altered gastrocnemius muscle fiber proportions as a result of denervation and reinnervation. Importantly, rBoNT/A1 with the fusion of a specific CPP, zinc finger protein (ZFP), resulted in the highest degree of muscle atrophy and greatest increase in the ratio of type I muscle fibers over type II fibers. An examination of gastrocnemius muscle cells at the subcellular levels using TEM staining revealed swelled mitochondria and diminished mitochondrial crista upon rBoNT/A1 administration. Transcriptomic RNA sequencing (RNA-Seq) analysis followed by RT-qPCR validation showed that rBoNT/A1 treatment also caused changes in mitochondrial biogenesis and mitophagy. Collectively, our results demonstrated that rBoNT/A1 proteins could alleviate skeletal muscle hypertrophy, with associated alterations of mitochondrial homeostasis. Full article

Glioblastoma, with a 5-year survival rate of just under 7.0%, is the most common form of brain cancer in adults. In this study, we evaluated the antiproliferative activity of the biopolymer p21-ELP1-Bac, a p21-derived peptide delivered via an elastin-like polypeptide (ELP1) carrier and a cell-penetrating peptide (CPP), across three glioblastoma cell lines: U87, GBM43, and GBM6. We assessed proliferation, cell cycle progression, and apoptosis to determine whether ELP-mediated intracellular delivery of p21-ELP1-Bac suppresses glioblastoma growth through cytostatic mechanisms rather than inducing apoptosis. Treatment with the modified protein effectively inhibited proliferation across all three lines, with U87 cells showing the greatest sensitivity and GBM6 cells demonstrating the greatest drug tolerance. Although apoptotic responses were generally low, they appeared more pronounced in GBM6 cells. Confocal microscopy revealed sustained cellular uptake and signal observed in both the cytoplasm and in proximity to the nucleus in all cell lines. Collectively, these findings indicate that p21-ELP1-Bac is efficiently internalized and capable of modulating proliferation across all three glioblastoma cell lines, supporting its further evaluation as a cytostatic delivery platform. Full article

The global rise in antimicrobial resistance (AMR) demands innovative strategies beyond traditional antibiotics. Peptide Nucleic Acids (PNAs), synthetic DNA analogues with peptide-like backbones, act as thermically, chemically, and enzymatically stable sequence-specific agents capable of silencing essential bacterial genes. Through antisense mechanisms, PNAs bind bacterial mRNA or rRNA, blocking translation or ribosome assembly and thereby inducing species-specific growth inhibition. Their programmable design enables precise targeting of multidrug-resistant pathogens while sparing commensal microbiota. Recent advances, including γ-modified backbones, cationic substitutions, and delivery platforms such as cell-penetrating peptides (CPPs), dendron conjugates, and nanoparticles, have improved solubility, stability, and cellular uptake. Studies show promising in vitro and, albeit less frequently, in vivo efficacy against both Gram-positive and Gram-negative bacteria, often with synergistic activity when combined with conventional antibiotics. Although challenges remain in delivery and large-scale production, PNAs represent a promising class of antimicrobials to combat AMR through targeted gene inhibition. Full article

Cell-penetrating peptides (CPPs) have been extensively explored as tools for the intracellular delivery of diverse molecular cargoes. Although substantial progress has been made in elucidating their uptake mechanisms and sequence-dependent functions, limitations in cellular internalization efficiency remain a major challenge, hindering their broader biomedical application. To address this issue, the present study investigated whether microwave (MW) irradiation at 2.45 GHz can enhance CPP-mediated delivery. Using confocal laser scanning microscopy and fluorescence spectroscopy, we examined the effects of MW irradiation on the cellular uptake of arginine-rich peptides. Our results suggested that MW irradiation enhanced the cellular uptake of the peptides. These findings imply that CPP-mediated delivery assisted by MW irradiation is an effective method for improving intracellular transport and may open new avenues for the development of advanced drug delivery systems. Full article

Background: Lactate Dehydrogenase C (LDHC) is a promising therapeutic target due to its highly tumor-specific expression, immunogenicity, and oncogenic functions. We previously showed that LDHC silencing in triple-negative breast cancer (TNBC) cells enhances treatment response to DNA-damage response-related drugs, supporting its therapeutic potential. However, no selective LDHC inhibitors exist, highlighting the need for innovative targeting strategies. Methods: We assessed the physicochemical properties and evaluated the delivery efficiency, anti-tumor activity, and safety of four cell-penetrating peptides (CPPs)—R10, 10R-RGD, cRGD-10R, and iRGD-10R—for siRNA-mediated LDHC silencing in TNBC. Clonogenic assays were used to evaluate effects on olaparib sensitivity, and TNBC zebrafish xenografts were utilized to study in vivo anti-tumor activity. Results: All CPP:siRNA complexes formed uniform nanocomplexes (129–168 nm) with low polydispersity indices (<0.25) and positive zeta potentials (+6.47 to +29.6 mV). Complexes remained stable in human serum for 24 h and showed no significant cytotoxicity in TNBC and non-cancerous cell lines. The 10R-RGD and cRGD-10R:siLDHC complexes achieved 40% LDHC protein knockdown, reduced TNBC clonogenicity by 30–36%, and enhanced olaparib sensitivity. Treatment of TNBC zebrafish xenografts with 10R-RGD or cRGD-10R:siLDHC complexes significantly reduced tumor growth by approximately 50% without major toxicity. Conclusions: These results demonstrate that CPP-mediated siRNA delivery enables selective LDHC silencing with tumor growth inhibition in triple-negative breast cancer models. This approach represents a novel, effective, and safe proof-of-concept therapeutic strategy to target LDHC, with potential translational relevance as a standalone therapy or in combination with common anti-cancer drugs. Full article

Acinetobacter baumannii represents a critical-priority organism due to its multidrug resistance. The emergence of carbapenem-resistant strains poses a major clinical challenge, underscoring the urgent need for novel antibacterial agents with alternative mechanisms. As peptide nucleic acids (PNAs) have recently gained attention as antisense therapeutics, we aimed to validate their potential as novel antimicrobial strategies against multidrug-resistant A. baumannii. We synthesized a cell-penetrating peptide (CPP)–PNA conjugate targeting pdxA, an essential gene involved in vitamin B6 biosynthesis. Among several candidate genes tested, the pdxA-targeting PNA exhibited the strongest inhibitory activity, achieving complete growth suppression of A. baumannii at 1.56 μM. Although quantitative real-time polymerase chain reaction did not reveal significant reductions in pdxA transcript levels, ELISA quantification revealed an approximately 80% reduction in intracellular vitamin B6, indicating translational inhibition rather than mRNA degradation. The pdxA-targeting CPP–PNA showed negligible activity against other Gram-negative or Gram-positive species, indicating high target specificity; no detectable cytotoxicity in human cells was observed even at relatively high concentrations. CPP–PNA conjugates targeting pdxA interfere with vitamin B6 biosynthesis, leading to growth inhibition of A. baumannii. These findings support PNA as a promising antisense antimicrobial platform that inhibits multidrug-resistant A. baumannii by blocking vitamin B6 biosynthesis. Full article

Background: Intracellular delivery of high-molecular-weight proteins is limited by the cell membrane. Cell-penetrating peptides (CPPs) offer a potential solution, but effective cytosolic delivery remains hindered by endosomal sequestration. Pas2r12, a CPP-derived peptide, facilitates cytosolic delivery of proteins including immunoglobulin G. Because Pas2r12 internalization occurs via caveolae-dependent endocytosis, we hypothesized that cell-surface receptors contribute to uptake. Methods: HEK293 cells were treated with Pas2r12 alone or complexed with enhanced green fluorescent protein (EGFP). Phosphorylation of insulin receptor (INSR), insulin-like growth factor 1 receptor (IGF1R), and extracellular signal–regulated kinase 1/2 (ERK1/2) was analyzed by Western blot. Linsitinib was used to inhibit INSR/IGF1R kinase activity. Cytosolic delivery was assessed by confocal microscopy, and receptor involvement was evaluated using siRNA-mediated knockdown and receptor overexpression. Results: Pas2r12 alone transiently increased INSR/IGF1R phosphorylation at 2 min (6.6-fold), which was suppressed by linsitinib (1.3-fold), and strongly increased ERK1/2 phosphorylation (6.2-fold), which was not inhibited by linsitinib. Pas2r12–EGFP did not induce detectable INSR/IGF1R phosphorylation in parental cells but increased ERK1/2 phosphorylation (3.4-fold). Linsitinib markedly reduced cytosolic EGFP delivery to 16% of control. INSR knockdown decreased delivery to 13–16%, and IGF1R knockdown to 19–65%. In INSR-overexpressing lines, Pas2r12–EGFP induced INSR/IGF1R phosphorylation (6.0-fold) and enhanced delivery (230–270%). In IGF1R-overexpressing lines, Pas2r12–EGFP did not induce phosphorylation, and delivery decreased to 60–69%. Conclusions: Pas2r12-mediated cytosolic delivery involves both INSR and IGF1R, with INSR contributing more prominently. These findings, including the largely INSR/IGF1R-independent ERK1/2 activation, provide mechanistic insight into Pas2r12-mediated protein delivery. Full article