Cell-penetrating peptides transport therapeutics into cells

Effect of HIV-1 TAT Peptide Fusion on 5' mRNA Cap Analogs Cell Membrane Permeability and Translation Inhibition

The development of targeted anticancer drugs has been one of the most challenging goals of current research. Eukaryotic translation initiation factor 4E (eIF4E) is an oncogene that stimulates mRNA translation via binding to the 5' endcap structure. It is well documented that eIF4E is overexpressed in many cancers including breast, prostate, head and neck, and stomach malignancies and leads to oncogenic transformation and metastasis. One approach to block eIF4E function in cancer cells is based on the disruption of the interaction between eIF4E and the 5' mRNA cap structure using cap analog inhibitors. Since analogs are cell-impermeable due to their anionic nature, we used a cell penetrating peptide (CPP) for delivery of model cap analogs into cancer cells. The human immunodeficiency virus I (HIV-1) transactivator of transcription derived peptide (TAT) was conjugated with the analogs m⁷GMP and m⁷GpppG using click chemistry methodology. We observed that both conjugates (m⁷GMP-TAT and m⁷GpppG-TAT), contrary to TAT alone, did not translocate through the artificial phospholipid membrane of giant unilamellar vesicles. This suggests that passive transport is not the mechanism by which translocation of cap analogs occurs. In contrast, synthesized fluorescently labeled m⁷GpppG-TAT translocated into the human breast adenocarcinoma cancer cell line MCF-7. Furthermore, we demonstrated that m⁷GMP-TAT and m⁷GpppG-TAT inhibited cap-dependent translation up to 30% both in vivo and in vitro while simultaneously not affecting cell growth and viability. These results demonstrate the usefulness of cell penetration peptides as carriers for the internalization of cap analogs.

Deciphering the internalization mechanism of WRAP:siRNA nanoparticles

Gene silencing mediated by double-stranded small interfering RNA (siRNA) has been widely investigated as a potential therapeutic approach for a variety of diseases and, indeed, the first therapeutic siRNA was approved by the FDA in 2018. As an alternative to the traditional delivery systems for nucleic acids, peptide-based nanoparticles (PBNs) have been applied successfully for siRNA delivery. Recently, we have developed amphipathic cell-penetrating peptides (CPPs), called WRAP allowing a rapid and efficient siRNA delivery into several cell lines at low doses (20 to 50 nM). In this study, using a highly specific gene silencing system, we aimed to elucidate the cellular uptake mechanism of WRAP:siRNA nanoparticles by combining biophysical, biological, confocal and electron microscopy approaches. We demonstrated that WRAP:siRNA complexes remain fully active in the presence of chemical inhibitors of different endosomal pathways suggesting a direct cell membrane translocation mechanism. Leakage studies on lipid vesicles indicated membrane destabilization properties of the nanoparticles and this was supported by the measurement of WRAP:siRNA internalization in dynamin triple-KO cells. However, we also observed some evidences for an endocytosis-dependent cellular internalization. Indeed, nanoparticles co-localized with transferrin, siRNA silencing was inhibited by the scavenger receptor A inhibitor Poly I and nanoparticles encapsulated in vesicles were observed by electron microscopy in U87 cells. In conclusion, we demonstrate here that the efficiency of WRAP:siRNA nanoparticles is mainly based on the use of multiple internalization mechanisms including direct translocation as well as endocytosis-dependent pathways.

Peptides derived from the C-terminal domain of HIV-1 Viral Protein R in lipid bilayers: Structure, membrane positioning and gene delivery

Viral protein R (Vpr) is a small accessory protein of 96 amino acids that is present in Human and simian immunodeficiency viruses. Among the very different properties that Vpr possesses we can find cell penetrating capabilities. Based on this and on its capacity to interact with nucleic acids we previously investigated the DNA transfection properties of Vpr and subfragments thereof. We found that fragments of the C-terminal helical domain of Vpr are able to deliver efficiently plasmid DNA into different cell lines. As the amphipathic helix may play a role in the interactions with membranes, we investigated whether insertion of a proline residue in the α-helix modifies the transfection properties of Vpr. Unexpectedly, we found that the resulting Vpr55-82 Pro70 peptide was even more efficient than wild type Vpr55-82 in the gene delivery assays. Using circular dichroism, light scattering and solid-state NMR techniques, we characterized the secondary structure and interactions of Vpr and several mutants with model membranes. A model is proposed where the proline shifts the dissociation equilibrium of the peptide-cargo complex and thereby its endosomal release.

Interdependence of charge and secondary structure on cellular uptake of cell penetrating peptide functionalized silica nanoparticles

The capability of cell-penetrating peptides (CPPs) to enable translocation of cargos across biological barriers shows promising pharmaceutical potential for the transport of drug molecules, as well as nanomaterials, into cells. Herein, we report on the optimization of a CPP, namely sC18, in terms of its translocation efficiency and investigate new CPPs regarding their interaction with silica nanoparticles (NPs). First, alanine scanning of sC18 yielded 16 cationic peptides from which two were selected for further studies. Whereas in the first case, a higher positive net charge and enhanced amphipathicity resulted in significantly higher internalization rates than sC18, the second one demonstrated reduced cellular uptake efficiencies and served as a control. We then attached these CPPs to silica nanoparticles of different sizes (50, 150 and 300 nm) via electrostatic interactions and could demonstrate that the secondary alpha-helical structure of the peptides was preserved. Following this, cellular uptake studies using HeLa cells showed that the tested CPP-NPs were successfully translocated into HeLa cells in a size-dependent manner. Moreover, depending on the CPP used, we realized differences in translocation efficiency, which were similar to what we had observed for the free peptides. All in all, we highlight the high potential of sequential fine-tuning of CPPs and provide novel insights into their interplay with inorganic biologically benign nanoparticles. Given the high cellular permeability of CPPs and their ability to translocate into a wide spectrum of cell types, our studies may stimulate future research of CPPs with inorganic nanocarrier surfaces.

Poly(ethylene glycol) shell-sheddable TAT-modified core cross-linked nano-micelles: TAT-enhanced cellular uptake and lysosomal pH-triggered doxorubicin release

This study aimed to develop sheddable polyethylene glycol (PEG) shells with TAT-modified core cross-linked nanomicelles as drug-delivery carriers of doxorubicin (DOX) to establish a programmed response against the tumor microenvironment, enhanced endocytosis, and lysosomal pH-triggered DOX release. First, poly(L-succinimide) (PSI) underwent a ring-opening reaction with ethylenediamine to generate poly(N-(2-aminoethyl)-l-aspartamide) (P(ae-Asp)). Next, the thiolytic cleavable PEG, 3,4-dihydroxyphenylacetic acid, and TAT were grafted onto P(ae-Asp) to synthesize the amphiphilic graft copolymer of mPEG-SS-g-P(ae-Asp)-MCA-DA-TAT. In aqueous solution, the amphiphilic polymer self-assembled into nanomicelles, encapsulating DOX into the hydrophobic core of micelles. TAT was shielded by the PEG corona during circulation to avoid non-specific transmembrane interaction with normal cells, while the tumor redox environment-responsive shedding of PEG could expose TAT to promote internalization of tumor cells. In order to improve the stability of nanomicelles and achieve pH-triggered drug release, a core cross-linking strategy based on the coordination of catechol and Fe³⁺ was adopted. In vitro studies demonstrated that core cross-linked nanomicelles maintained the nanostructure in 100 times dilution in pH 7.4 phosphate-buffered saline (PBS). Moreover, DOX release from DOX-loaded core cross-linked nanomicelles (DOX-TAT-CCLMs) was favored at simulated lysosomal conditions over simulated plasma conditions, indicating that these nanomicelles demonstrate characteristics of pH-triggered DOX release. The TAT modification considerably enhanced the mean fluorescence intensity of the nanomicelles endocytosed by MCF-7/ADR cells by 8 times, compared with DOX·HCl after 8 h of incubation. Notably, the IC₅₀ value of nanomicelles (11.61 ± 0.95 μg/mL) was nearly 4 times lower than that of DOX·HCl against MCF-7/ADR cells, implying that the nanomicelles could overcome drug resistance observed in MCF-7/ADR cells. Furthermore, the DOX-TAT-CCLMs reported superior tumor growth suppression in a 4T1 tumor-bearing mouse model. Thus, the redox- and pH- stimuli stepwise-responsive novel nanomicelles fabricated from the mPEG-SS-g-P(ae-Asp)-MCA-DA-TAT graft copolymer exhibited multifunctionality and displayed great potential for drug delivery.

[Chlorine e6 in phospholipid nanoparticles with specific targeting and penetrating peptides as prospective composition for photodynamic therapy of malignant neoplasms]

Cytotoxic and photoinduced activity of chlorine e6 (Ce6) in phospholipid nanoparticles with specific tumor targeting and cell-penetrating peptides was studied in vitro using human fibrosarcoma cells HT-1080. It was shown, that the binding of cell-penetrating peptide R7 - alone or combined with the peptide containing specific targeting motif NGR (Asn-Gly-Arg) - resulted in 3-fold decrease of Ce6 photoinduced activity as compared with that in nanoparticles without peptides (IC50 values were 0.7 μg/ml and 2.1 μg/ml, respectively). The NGR influence was unexpectedly low - less than 20% (IC50 1.7 μg/ml). This suggests the more importance of Ce6 cell penetration in this case, than of NGR-mediated targeting. The effect of inclusion of both peptides on the total cytotoxicity of Ce6 was minimal (10-16 times less than on the specific photoinduced activity). The obtained results - together with earlier shown effects on improvement of the pharmacokinetics of Ce6 in vivo after its embedding into phospholipid nanoparticles - indicate the prospects of using the obtained phospholipid nanoparticles system for photodynamic therapy.

Abiotic Factors Promote Cell Penetrating Peptide Permeability in Enterobacteriaceae Models

Conventionally, the delivery of biomolecules into bacteria for the generation of characterized or functional mutants has relied greatly on horizontal gene transfer techniques. However, the low compatibility of these techniques with novel or hard-to-transform bacteria currently serves as a challenge to the bioengineering field. Here, we explored the use of cell penetrating peptides (CPPs) as an alternative biomolecule delivery approach by investigating the effects of the abiotic factors during CPP permeation. Using the (KFF)₃K-FAM conjugate and Escherichia coli as models, we evaluated four abiotic factors where two of these factors, temperature and solution tonicity, promoted (KFF)₃K-FAM permeation efficiency. Our data show that optimal (KFF)₃K-FAM permeation efficiency was achieved for E. coli at approximately 98.1% under conditions of 37°C (growth optimal temperature) and 50% PBS concentration. Based on these conditions, we subsequently tested the applicability of CPP permeation in various bacterial strains by treating 10 bacterial strains from the Enterobacteriaceae family among which seven strains have no CPP permeation records with (KFF)₃K-FAM. Interestingly, when compared with non-optimized conditions, all 10 strains showed a marked increase in CPP permeation ranging between 20 and 90% efficiency. Although using strains within Enterobacteriaceae that are phylogenetically close, our results hinted on the possibility that with proper optimization of the abiotic factors, CPPs could be compatible with a broad range of bacterial strains. Our efforts suggest that CPP could serve as an effective alternative approach for mutant generation and for biomolecule delivery into novel or hard-to-transform bacteria.

Nano-Inspired Technologies for Peptide Delivery

Nano-inspired technologies offer unique opportunities to treat numerous diseases by using therapeutic peptides. Therapeutic peptides have attractive pharmacological profiles and can be manufactured at relatively low costs. The major advantages of using a nanodelivery approach comprises significantly lower required dosages compared to systemic delivery, and thus reduced toxicity and immunogenicity. The combination of therapeutic peptides with delivery peptides and nanoparticles or small molecule drugs offers systemic treatment approaches, instead of aiming for single biological targets or pathways. This review article discusses exemplary state-of-the-art nanosized delivery systems for therapeutic peptides and antibodies, as well as their biochemical and biophysical foundations and emphasizes still remaining challenges. The competition between using different nanoplatforms, such as liposome-, hydrogel-, polymer-, silica nanosphere-, or nanosponge-based delivery systems is still "on" and no clear frontrunner has emerged to date.

Considerations on the Rational Design of Covalently Conjugated Cell-Penetrating Peptides (CPPs) for Intracellular Delivery of Proteins: A Guide to CPP Selection Using Glucarpidase as the Model Cargo Molecule

Access of proteins to their intracellular targets is limited by a hydrophobic barrier called the cellular membrane. Conjugation with cell-penetrating peptides (CPPs) has been shown to improve protein transduction into the cells. This conjugation can be either covalent or non-covalent, each with its unique pros and cons. The CPP-protein covalent conjugation may result in undesirable structural and functional alterations in the target protein. Therefore, we propose a systematic approach to evaluate different CPPs for covalent conjugations. This guide is presented using the carboxypeptidase G2 (CPG2) enzyme as the target protein. Seventy CPPs -out of 1155- with the highest probability of uptake efficiency were selected. These peptides were then conjugated to the N- or C-terminus of CPG2. Translational efficacy of the conjugates, robustness and thermodynamic properties of the chimera, aggregation possibility, folding rate, backbone flexibility, and aspects of in vivo administration such as protease susceptibility were predicted. The effect of the position of conjugation was evaluated using unpaired t-test (p < 0.05). It was concluded that N-terminal conjugation resulted in higher quality constructs. Seventeen CPP-CPG2/CPG2-CPP constructs were identified as the most promising. Based on this study, the bioinformatics workflow that is presented may be universally applied to any CPP-protein conjugate design.

A Perspective on the Development of TGF-β Inhibitors for Cancer Treatment

Transforming growth factor (TGF)-β is a secreted multifunctional cytokine that signals via plasma membrane TGF-β type I and type II receptors and intercellular SMAD transcriptional effectors. Aberrant inter- and intracellular TGF-β signaling can contribute to cancer progression. In normal cells and early stages of cancer, TGF-β can stimulate epithelial growth arrest and elicit a tumor suppressor function. However, in late stages of cancer, when the cytostatic effects of TGF-β in cancer cells are blocked, TGF-β signaling can act as tumor promoter by its ability to stimulate epithelial-to-mesenchymal transition of cancer cells, by stimulating angiogenesis, and by promoting evasion of immune responses. In this review, we will discuss the rationale and challenges of targeting TGF-β signaling in cancer and summarize the clinical status of TGF-β signaling inhibitors that interfere with TGFβ bioavailability, TGF-βreceptor interaction, or TGF-β receptor kinase function. Moreover, we will discuss targeting of TGF-β signaling modulators and downstream effectors as well as alternative approaches by using promising technologies that may lead to entirely new classes of drugs.

A Perspective on the Development of TGF-β Inhibitors for Cancer Treatment

Transforming growth factor (TGF)-β is a secreted multifunctional cytokine that signals via plasma membrane TGF-β type I and type II receptors and intercellular SMAD transcriptional effectors. Aberrant inter- and intracellular TGF-β signaling can contribute to cancer progression. In normal cells and early stages of cancer, TGF-β can stimulate epithelial growth arrest and elicit a tumor suppressor function. However, in late stages of cancer, when the cytostatic effects of TGF-β in cancer cells are blocked, TGF-β signaling can act as tumor promoter by its ability to stimulate epithelial-to-mesenchymal transition of cancer cells, by stimulating angiogenesis, and by promoting evasion of immune responses. In this review, we will discuss the rationale and challenges of targeting TGF-β signaling in cancer and summarize the clinical status of TGF-β signaling inhibitors that interfere with TGF−β bioavailability, TGF-β/receptor interaction, or TGF-β receptor kinase function. Moreover, we will discuss targeting of TGF-β signaling modulators and downstream effectors as well as alternative approaches by using promising technologies that may lead to entirely new classes of drugs.

Cell penetrating peptides: the potent multi-cargo intracellular carriers

Introduction: Cell penetrating peptides (CPPs) known as protein translocation domains (PTD), membrane translocating sequences (MTS), or Trojan peptides (TP) are able to cross biological membranes without clear toxicity using different mechanisms, and facilitate the intracellular delivery of a variety of bioactive cargos. CPPs could overcome some limitations of drug delivery and combat resistant strains against a broad range of diseases. Despite delivery of different therapeutic molecules by CPPs, they lack cell specificity and have a short duration of action. These limitations led to design of combined cargo delivery systems and subsequently improvement of their clinical applications. Areas covered: This review covers all our studies and other researchers in different aspects of CPPs such as classification, uptake mechanisms, and biomedical applications. Expert opinion: Due to low cytotoxicity of CPPs as compared to other carriers and final degradation to amino acids, they are suitable for preclinical and clinical studies. Generally, the efficiency of CPPs was suitable to penetrate the cell membrane and deliver different cargos to specific intracellular sites. However, no CPP-based therapeutic approach has approved by FDA, yet; because there are some disadvantages for CPPs including short half-life in blood, and nonspecific CPP-mediated delivery to normal tissue. Thus, some methods were used to develop the functions of CPPs in vitro and in vivo including the augmentation of cell specificity by activatable CPPs, specific transport into cell organelles by insertion of corresponding localization sequences, incorporation of CPPs into multifunctional dendrimeric or liposomal nanocarriers to improve selectivity and efficiency especially in tumor cells.

Effect of dehydrocholic acid conjugated with a hydrocarbon on a lipid bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine

The effects of bile acids, dehydrocholic acid (DHA) and DHA conjugated with a hydrocarbon (6-aminohexanoate; 6A-DHA) were evaluated using a lipid bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). DOPC formed a homogenous thin membrane in presence or absence of the DHA, while 20 mol% 6A-DHA induced phase separation on the DOPC thin membrane. It was observed formation of a stomatocyte-like liposomes when these membranes were suspended in a basic solvent. Generally, liposome formation can be prevented by some bile acids. It was found that DHA and 6A-DHA did not disrupt liposome formation, while DHA and 6A-DHA perturbed the liposomal membrane, resulting in increased local-fluidity due to the bent structure of DHA and 6A-DHA. DHA and 6A-DHA showed completely different effects on the hydrophobicity of the boundary surface of DOPC liposome membranes. The steroidal backbone of DHA was found to prevent the insertion of water molecules into the liposomal membrane, whereas 6A-DHA did not show the same behavior which was attributed to its conjugated hydrocarbon.

Development and screening of brain-targeted lipid-based nanoparticles with enhanced cell penetration and gene delivery properties

Background

The potential of gene therapy for treatment of neurological disorders can be explored using designed lipid-based nanoparticles such as liposomes, which have demonstrated ability to deliver nucleic acid to brain cells. We synthesized liposomes conjugated to cell-penetrating peptides (CPPs) (vascular endothelial-cadherin-derived peptide [pVec], pentapeptide QLPVM and HIV-1 trans-activating protein [TAT]) and transferrin (Tf) ligand, and examined the influence of surface modifications on the liposome delivery capacity and transfection efficiency of encapsulated plasmid DNA. The design of liposomes was based on targeting molecular recognition of transferrin receptor overexpressed on the blood–brain barrier (BBB) with enhanced internalization ability of CPPs.

Methods

CPP-Tf-liposomes were characterized by particle size distribution, zeta potential, protection of encapsulated plasmid DNA, uptake mechanisms and transfection efficiencies. An in vitro triple co-culture BBB model selected the liposomal formulations that were able to cross the in vitro BBB and subsequently, transfect primary neuronal cells. The in vivo biodistribution and biocompatibility of selected formulations were also investigated in mice.

Results

Liposomal formulations were able to protect the encapsulated plasmid DNA against enzymatic degradation and presented low hemolytic potential and low cytotoxicity at 100 nM phospholipid concentration. Cellular internalization of nanoparticles occurred via multiple endocytosis pathways. CPP-Tf-conjugated liposomes mediated robust transfection of brain endothelial (bEnd.3), primary glial and primary neuronal cells. Liposomes modified with Tf and TAT demonstrated superior ability to cross the barrier layer and subsequently, transfect neuronal cells compared to other formulations. Quantification of fluorescently labeled liposomes and in vivo imaging demonstrated that this system could efficiently overcome the BBB and penetrate the brain of mice (7.7% penetration of injected dose).

Conclusion

In vitro screening platforms are important tools to enhance the success of brain-targeted gene delivery systems. The potential of TAT-Tf-liposomes as efficient brain-targeted gene carriers in vitro and in vivo was suggested to be related to the presence of selected moieties on the nanoparticle surface.

How to evaluate the cellular uptake of CPPs with fluorescence techniques: Dissecting methodological pitfalls associated to tryptophan-rich peptides

Cell-penetrating peptides (CPP) are broadly recognized as efficient non-viral vectors for the internalization of compounds such as peptides, oligonucleotides or proteins. Characterizing these carriers requires reliable methods to quantify their intracellular uptake. Flow cytometry on living cells is a method of choice but is not always applicable (e.g. big or polarized cells), so we decided to compare it to fluorescence spectroscopy on cell lysates. Surprisingly, for the internalization of a series of TAMRA-labeled conjugates formed of either cationic or amphipathic CPPs covalently coupled to a decamer peptide, we observed important differences in internalization levels between both methods. We partly explained these discrepancies by analyzing the effect of buffer conditions (pH, detergents) and peptide sequence/structure on TAMRA dye accessibility. Based on this analysis, we calculated a correction coefficient allowing a better coherence between both methods. However, an overestimated signal was still observable for both amphipathic peptides using the spectroscopic detection, which could be due to their localization at the cell membrane. Based on several in vitro experiments modeling events at the plasma membrane, we hypothesized that fluorescence of peptides entrapped in the membrane bilayer could be quenched by the tryptophan residues of close transmembrane proteins. During cell lysis, cell membranes are disintegrated liberating the entrapped peptides and restoring the fluorescence, explaining the divergences observed between flow cytometry and spectroscopy on lysates. Overall, our results highlighted major biases in the fluorescently-based quantification of internalized fluorescently-labeled CPP conjugates, which should be considered for accurate uptake quantification.

Functionalized liposomal nanoparticles for efficient gene delivery system to neuronal cell transfection

Liposome based delivery systems provide a promising strategy for treatment of neurodegenerative diseases. A rational design of brain-targeted liposomes can support the development of more efficient treatments with drugs and gene materials. Here, we characterized surface modified liposomes with transferrin (Tf) protein and penetratin (Pen), a cell-penetrating peptide, for efficient and targeted gene delivery to brain cells. PenTf-liposomes efficiently encapsulated plasmid DNA, protected them against enzymatic degradation and exhibited a sustained in vitro release kinetics. The formulation demonstrated low cytotoxicity and was non-hemolytic. Liposomes were internalized into cells mainly through energy-dependent pathways especially clathrin-mediated endocytosis. Reporter gene transfection and consequent protein expression in different cell lines were significantly higher using PenTf-liposomes compared to unmodified liposomes. The ability of these liposomes to escape from endosomes can be an important factor which may have likely contributed to the high transfection efficiency observed. Rationally designed bifunctional targeted-liposomes provide an efficient tool for improving the targetability and efficacy of synthesized delivery systems. This investigation of liposomal properties attempted to address cell differences, as well as, vector differences, in gene transfectability. The findings indicate that PenTf-liposomes can be a safe and non-invasive approach to transfect neuronal cells through multiple endocytosis pathways.

Optimization of Polyarginine-Conjugated PEG Lipid Grafted Proliposome Formulation for Enhanced Cellular Association of a Protein Drug

The purpose of this study was to develop an oral proliposomal powder of protein using poly-l-arginine-conjugated 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol) (DSPE-PEG) (PLD) for enhancing cellular association upon reconstitution and to compare its effects with a non-grafted and PEGylated formulation. Cationic proliposome (CATL), PLD-grafted CATL (PLD-CATL), PEGylated CATL (PEG CATL), and PLD grafted-PEG CATL (PLD-PEG CATL) were prepared and compared. Successful conjugation between poly-l-arginine and DSPE-PEG was confirmed by ¹H NMR and FT-IR. PLD was successfully grafted onto the proliposomal powder during the slurry process. Although reconstituted liposomal sizes of CATL and PLD-CATL were increased by agglomeration, PEGylation reduced the agglomeration and increased the encapsulation. The viabilities of cells treated with both CATL and PLD-CATL formulations were low but increased following PEGylation. With regard to cellular association, PLD-CATL enhanced cellular association/uptake more rapidly than did CATL. Upon PEGylation, PEG CATL showed a lower level of cellular association/uptake compared with CATL while PLD-PEG CATL did not exhibit the rapid cellular association/uptake as seen with PLD-CATL. However, PLD-PEG CATL still enhanced the higher cellular association/uptake than PEG CATL did without PLD. In conclusion, proliposomes with PLD could accelerate cellular association/uptake but also caused high cellular toxicity. PEGylation reduced cellular toxicity and also changed the cellular association pattern of the PLD formulation.

Codelivery of Plasmid and Curcumin with Mesoporous Silica Nanoparticles for Promoting Neurite Outgrowth

Reactive oxygen species (ROS)-induced oxidative stress leads to neuron damage and is involved in the pathogenesis of chronic inflammation in neurodegenerative diseases (NDs), such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis. Researchers, therefore, are looking for antiinflammatory drugs and gene therapy approaches to slow down or even prevent neurological disorders. Combining therapeutics has shown a synergistic effect in the treatment of human diseases. Many nanocarriers could be designed for the simultaneous codelivery of drugs with genes to fight diseases. However, only a few researches have been performed in NDs. In this study, we developed a mesoporous silica nanoparticle (MSN)-based approach for neurodegenerative therapy. This MSN-based platform involved multiple designs in the targeted codelivery of (1) curcumin, a natural antioxidant product, to protect ROS-induced cell damage and (2) plasmid RhoG-DsRed, which is associated with the formation of lamellipodia and filopodia for promoting neurite outgrowth. At the same time, TAT peptide was introduced to the plasmid RhoG-DsRed via electrostatic interaction to elevate the efficiency of nonendocytic pathways and the nuclear plasmid delivery of RhoG-DsRed in cells for enhanced gene expression. Besides, such a plasmid RhoG-DsRed/TAT complex could work as a noncovalent gatekeeper. The release of curcumin inside the channel of the MSN could be triggered when the complex was dissociated from the MSN surface. Taken together, this MSN-based platform combining genetic and pharmacological manipulations of an actin cytoskeleton as well as oxidative stress provides an attractive way for ND therapy.

Pharmacologic Characterization of ALD1910, a Potent Humanized Monoclonal Antibody against the Pituitary Adenylate Cyclase-Activating Peptide

Migraine is a debilitating disease that affects almost 15% of the population worldwide and is the first cause of disability in people under 50 years of age, yet its etiology and pathophysiology remain incompletely understood. Recently, small molecules and therapeutic antibodies that block the calcitonin gene-related peptide (CGRP) signaling pathway have reduced migraine occurrence and aborted acute attacks of migraine in clinical trials and provided prevention in patients with episodic and chronic migraine. Heterogeneity is present within each diagnosis and patient's response to treatment, suggesting migraine as a final common pathway potentially activated by multiple mechanisms, e.g., not all migraine attacks respond to or are prevented by anti-CGRP pharmacological interventions. Consequently, other unique mechanisms central to migraine pathogenesis may present new targets for drug development. Pituitary adenylate cyclase-activating peptide (PACAP) is an attractive novel target for treatment of migraines. We generated a specific, high-affinity, neutralizing monoclonal antibody (ALD1910) with reactivity to both PACAP38 and PACAP27. In vitro, ALD1910 effectively antagonizes PACAP38 signaling through the pituitary adenylate cyclase-activating peptide type I receptor, vasoactive intestinal peptide receptor 1, and vasoactive intestinal peptide receptor 2. ALD1910 recognizes a nonlinear epitope within PACAP and blocks its binding to the cell surface. To test ALD1910 antagonistic properties directed against endogenous PACAP, we developed an umbellulone-induced rat model of neurogenic vasodilation and parasympathetic lacrimation. In vivo, this model demonstrates that the antagonistic activity of ALD1910 is dose-dependent, retaining efficacy at doses as low as 0.3 mg/kg. These results indicate that ALD1910 represents a potential therapeutic antibody to address PACAP-mediated migraine.

Targeting high transcriptional control activity of long mononucleotide A-T repeats in cancer by Argonaute 1

Epigenetic regulatory changes alter the gene regulation function of DNA repeat elements in cancer and consequently promote malignant phenotypes. Some short tandem repeat sequences, distributed throughout the human genome, can play a role as cis-regulatory elements of the genes. Distributions of tandem long (≥10) and short (<10) A-T repeats in the genome are different depending on gene functions. Long repeats are more commonly found in housekeeping genes and may regulate genes in harmonious fashion. Mononucleotide A-repeats around transcription start sites interact with Argonaute proteins (AGOs) to regulate gene expression. miRNA-bound AGO alterations in cancer have been reported; consequently, these changes would affect genes containing mononucleotide A- and T-repeats. Here, we showed an unprecedented hallmark of gene regulation in cancer. We evaluated the gene expression profiles reported in the Gene Expression Omnibus and found a high density of 13-27 A-T repeats in the up-regulated genes in malignancies derived from the bladder, cervix, head and neck, ovary, vulva, breast, colon, liver, lung, prostate, kidney, thyroid, adrenal gland, bone, blood cells, muscle and brain. Transfection of cell-penetrating protein tag AGO1 containing poly uracils (CPP-AGO1-polyUs) to the lung cancer cell lines altered gene regulation depending on the presence of long A-T repeats. CPP-AGO1-polyUs limited cell proliferation and the ability of a cancer cell to grow into a colony in lung cancer cell lines. In conclusion, long A-T repeats up-regulated many genes in cancer that can be targeted by AGO1 to change the expression of many genes and limited cancer growth.

Recent Advances in Cell Penetrating Peptide-Based Anticancer Therapies

Cell-penetrating-peptides (CPPs) are small amino-acid sequences characterized by their ability to cross cellular membranes. They can transport various bioactive cargos inside cells including nucleic acids, large proteins, and other chemical compounds. Since 1988, natural and synthetic CPPs have been developed for applications ranging from fundamental to applied biology (cell imaging, gene editing, therapeutics delivery). In recent years, a great number of studies reported the potential of CPPs as carriers for the treatment of various diseases. Apart from a good efficacy due to a rapid and potent delivery, a crucial advantage of CPP-based therapies is the peptides low toxicity compared to most drug carriers. On the other hand, they are quite unstable and lack specificity. Higher specificity can be obtained using a cell-specific CPP to transport the therapeutic agent or using a non-specific CPP to transport a cargo with a targeted activity. CPP-cargo complexes can also be conjugated to another moiety that brings cell- or tissue-specificity. Studies based on all these approaches are showing promising results. Here, we focus on recent advances in the potential usage of CPPs in the context of cancer therapy, with a particular interest in CPP-mediated delivery of anti-tumoral proteins.

64Cu and fluorescein labeled anti-miRNA peptide nucleic acids for the detection of miRNA expression in living cells

MiRNAs are single stranded RNAs of 18-22 nucleotides. They are promising diagnostic and prognostic markers for several pathologies including tumors, neurodegenerative, cardiovascular and autoimmune diseases. In the present work the development and characterization of anti-miRNA radiolabeled probes based on peptide nucleic acids (PNAs) for potential non-invasive molecular imaging in vivo of giant cell arteritis are described. MiR-146a and miR-146b-5p were selected as targets because they have been found up-regulated in this disease. Anti-miR and scramble PNAs were synthesized and linked to carboxyfluorescein or DOTA. DOTA-anti-miR PNAs were then labelled with copper-64 (64Cu) to function as non-invasive molecular imaging tools. The affinity of the probes for the targets was assessed in vitro by circular dichroism and melting temperature. Differential uptake of fluorescein and 64Cu labeled anti-miRNA probes was tested on BCPAP and A549 cell lines, expressing different levels of miR-146a and -146b-5p. The experiments showed that the anti-miR-146a PNAs were more effective than the anti-miR-146b-5p PNAs. Anti-miR-146a PNAs could bind both miR-146a and miR-146b-5p. The uptake of fluorescein and 64Cu labeled anti-miR-146a PNAs was higher than that of the negative control scramble PNAs in miRNA expressing cells in vitro. 64Cu-anti-miR-146a PNAs might be further investigated for non-invasive PET imaging of miR-146 overexpressing diseases.

A Nanobody Targeting Viral Nonstructural Protein 9 Inhibits Porcine Reproductive and Respiratory Syndrome Virus Replication

Porcine reproductive and respiratory syndrome (PRRS) is of great concern to the swine industry due to pandemic outbreaks of the disease, current ineffective vaccinations, and a lack of efficient antiviral strategies. In our previous study, a PRRSV Nsp9-specific nanobody, Nb6, was successfully isolated, and the intracellularly expressed Nb6 could dramatically inhibit PRRSV replication in MARC-145 cells. However, despite its small size, the application of Nb6 protein in infected cells is greatly limited, as the protein itself cannot enter the cells physically. In this study, a trans-activating transduction (TAT) peptide was fused with Nb6 to promote protein entry into cells. TAT-Nb6 was expressed as an inclusion body in Escherichia coli, and indirect enzyme-linked immunosorbent assays and pulldown assays showed that E. coli-expressed TAT-Nb6 maintained the binding ability to E. coli-expressed or PRRSV-encoded Nsp9. We demonstrated that TAT delivered Nb6 into MARC-145 cells and porcine alveolar macrophages (PAMs) in a dose- and time-dependent manner, and TAT-Nb6 efficiently inhibited the replication of several PRRSV genotype 2 strains as well as a genotype 1 strain. Using a yeast two-hybrid assay, Nb6 recognition sites were identified in the C-terminal part of Nsp9 and spanned two discontinuous regions (Nsp9_aa454-551 and Nsp9_aa599-646). Taken together, these results suggest that TAT-Nb6 can be developed as an antiviral drug for the inhibition of PRRSV replication and controlling PRRS disease.IMPORTANCE The pandemic outbreak of PRRS, which is caused by PRRSV, has greatly affected the swine industry. We still lack an efficient vaccine, and it is an immense challenge to control its infection. An intracellularly expressed Nsp9-specific nanobody, Nb6, has been shown to be able to inhibit PRRSV replication in MARC-145 cells. However, its application is limited, because Nb6 cannot physically enter cells. Here, we demonstrated that the cell-penetrating peptide TAT could deliver Nb6 into cultured cells. In addition, TAT-Nb6 fusion protein could suppress the replication of various PRRSV strains in MARC-145 cells and PAMs. These findings may provide a new approach for drug development to control PRRS.

TP10-Dopamine Conjugate as a Potential Therapeutic Agent in the Treatment of Parkinson's Disease

Parkinson's disease (PD) is a common progressive neurodegenerative disorder for which the current treatment is not fully satisfactory. One of the major drawbacks of current PD therapy is poor penetration of drugs across the blood-brain barrier (BBB). In recent years, cell-penetrating peptides (CPPs) such as Tat, SynB, or TP10 have gained great interest due to their ability to penetrate cell membranes and to deliver different cargos to their targets including the central nervous system (CNS). However, there is no data with respect to the use of CPPs as drug carriers to the brain for the treatment of PD. In the presented research, the covalent TP10-dopamine conjugate was synthesized and its pharmacological properties were characterized in terms of its ability to penetrate the BBB and anti-parkinsonian activity. The results showed that dopamine (DA) in the form of a conjugate with TP10 evidently gained access to the brain tissue, exhibited low susceptibility to O-methylation reaction by catechol- O-methyltransferase (lower than that of DA), possessed a relatively high affinity to both dopamine D₁ and D₂ receptors (in the case of D₁, a much higher than that of DA), and showed anti-parkinsonian activity (higher than that of l-DOPA) in the MPTP-induced preclinical animal model of PD. The presented results prove that the conjugation of TP10 with DA may be a good starting point for the development of a new strategy for the treatment of PD.

New Cell-Penetrating Peptide (KRP) with Multiple Physicochemical Properties Endows Doxorubicin with Tumor Targeting and Improves Its Therapeutic Index

Cell-penetrating peptides (CPPs) are considered as promising drug carriers by virtue of their potent cell-penetrating capacity. However, lack of targetability still represents a bottleneck for their systemic administration. Here, we synthesized a lysine-rich CPP named KRP and developed a tumor-targeted drug delivery system (DDS) by linking KRP and doxorubicin (DOX) with stable covalent bonds (thioether bond and amide bond). Through in vitro and in vivo tests, we confirmed that the multiple physicochemical properties of KRP endow KRP-DOX with multiple synergistic functions, including good biocompatibility and biodistribution, selective accumulation in tumor tissues, inclination to remain in tumor tissues and be internalized by tumor cells; stable covalent bonds prevent free DOX release from KRP-DOX in blood stream, shield normal tissues from the toxic effect of DOX, and lead to the majority of DOX delivery into tumor cells by KRP; lysosome escape of KRP-DOX ensures its tumor-killing effect. In addition, the simple chemical composition and modification reduce the risk of immunogenicity and metabolite toxicity. Our study provides a simple, safe, and efficient platform for tumor-targeted DDS.

Cell penetrating peptides in preclinical and clinical cancer diagnosis and therapy

Delivery of imaging reagents and drugs to tumors is essential for cancer diagnosis and therapy. In addition to therapeutic and diagnostic functionalities, peptides have potential benefits such as biocompatibility, ease to synthesize, smaller size, by-passing off-target side effects, and achieving the beneficial effects with lower-administered dosages. A particular type of peptide known as cell penetrating peptides (CPP) have been predominantly studied during last twenty years as they are not only capable to translocate themselves across membranes but also allow carrier drugs to translocate across plasma membrane, by different mechanisms depending on the CPP. This is of great potential importance in drug delivery systems, as the ability to pass across membranes is crucial to many drug delivery systems. In spite of significant progress in design and application of CPP, more investigations are required to further improve their delivery to tumors, with reduced side-effect and enhanced therapeutic efficacy. In this review, we emphasis on current advancements in preclinical and clinical trials based on using CPP for more efficient delivery of anti-cancer drugs and imaging reagents to cancer tissues and individual cells associated with them. We discuss the evolution of the CPPs-based strategies for targeted delivery, their current status and strengths, along with summarizing the role of CPPs in targeted drug delivery. We also discuss some recently reported diagnostic applications of engineered protease-responsive substrates and activable imaging complexes. We highlight the recent clinical trial data by providing a road map for better design of the CPPs for future preclinical and clinical applications.

Enhancing Protective Efficacy of Poultry Vaccines through Targeted Delivery of Antigens to Antigen-Presenting Cells

Avian viral diseases including avian influenza, Marek's disease and Newcastle disease are detrimental to economies around the world that depend on the poultry trade. A significant zoonotic threat is also posed by avian influenza viruses. Vaccination is an important and widely used method for controlling these poultry diseases. However, the current vaccines do not provide full protection or sterile immunity. Hence, there is a need to develop improved vaccines. The major aim of developing improved vaccines is to induce strong and specific humoral and cellular immunity in vaccinated animals. One strategy used to enhance the immunogenicity of vaccines is the selective delivery of protective antigens to antigen-presenting cells (APCs) including dendritic cells, macrophages and B cells. APCs have a central role in the initiation and maintenance of immune responses through their ability to capture, process and present antigens to T and B cells. Vaccine technology that selectively targets APCs has been achieved by coupling antigens to monoclonal antibodies or ligands that are targeted by APCs. The aim of this review is to discuss existing strategies of selective delivery of antigens to APCs for effective vaccine development in poultry.

Pulmonary surfactant and drug delivery: Focusing on the role of surfactant proteins

Pulmonary surfactant (PS) has been extensively studied because of its primary role in mammalian breathing. The deposition of this surface-active material at the alveolar air-water interface is essential to lower surface tension, thus avoiding alveolar collapse during expiration. In addition, PS is involved in host defense, facilitating the clearance of potentially harmful particulates. PS has a unique composition, including 92% of lipids and 8% of surfactant proteins (SPs) by mass. Although they constitute the minor fraction, SPs to a large extent orchestrate PS-related functions. PS contains four surfactant proteins (SPs) that can be structurally and functionally divided in two groups, i.e. the large hydrophilic SP-A and SP-D and the smaller hydrophobic SP-B and SP-C. The former belong to the family of collectins and are involved in opsonization processes, thus promoting uptake of pathogens and (nano)particles by phagocytic cell types. The latter SPs regulate interfacial surfactant adsorption dynamics, facilitating (phospho)lipid transfer and membrane fusion processes. In the context of pulmonary drug delivery, the exploitation of PS as a carrier to promote drug spreading along the alveolar interface is gaining interest. In addition, recent studies investigated the interaction of PS with drug-loaded nanoparticles (nanomedicines) following pulmonary administration, which strongly influences their biological fate, drug delivery efficiency and toxicological profile. Interestingly, the specific biophysical mode-of-action of the four SPs affect the drug delivery process of nanomedicines both on the extra-and intracellular level, modulating pulmonary distribution, cell targeting and intracellular delivery. This knowledge can be harnessed to exploit SPs for the design of unique and bio-inspired drug delivery strategies.

Bioresponsive polyplexes - chemically programmed for nucleic acid delivery

INTRODUCTION

The whole delivery process of nucleic acids is very challenging. Appropriate carrier systems are needed, which show extracellular stability and intracellular disassembly. Viruses have developed various strategies to meet these requirements, as they are optimized by biological evolution to transfer genetic information into host cells. Taking viruses as models, smart synthetic carriers can be designed, mimicking the efficient delivery process of viral infection. These 'synthetic viruses' are pre-programmed and respond to little differences in their microenvironment, caused by either exogenous or endogenous stimuli.

AREAS COVERED

This review deals with polymer-based, bioresponsive nanosystems (polyplexes) for the delivery of nucleic acids. Strategies utilizing pH-responsiveness, redox-responsiveness as well as sensitivity towards enzymes will be described more in detail. Systems, which respond to other endogenous triggers (i.e. reactive oxygen species, adenosine triphosphate, hypoxia), will be briefly illustrated. Moreover, some examples for combined bioresponsiveness will be presented.

EXPERT OPINION

Bioresponsive polyplexes are a smart way to facilitate programmed, timely delivery of nucleic acids to desired, specific sites. Nevertheless, further optimization is necessary to improve the still moderate transfection efficiency and specificity - also in regard to medical translation. For this purpose, precise carrier structures are desirable and stability issues of bioresponsive systems must be considered.

The antitumor effect of TAT-DCF1 peptide in glioma cells

BACKGROUND

Glioblastoma is one of the most malignant brain cancer, thus, establishing an effective therapy is paramount. Our previous results indicate that dendritic cell-derived factor (DCF1) is an attractive candidate for therapy against Glioblastoma, since its overexpression in Glioblastoma U251 cells leads to apoptosis. However, the delivery approach limits its clinical application, in this paper, we expressed TAT-DCF1 fusion protein in E.coli in order to surmount its current delivery problems.

METHODS

The coding sequences of the different domains of DCF1 (full length, cytoplasmic, extracellular, 19-amino acid), together with the N-terminal transactivator of transcription (TAT) sequence, were amplified and subcloned into the bacterial expression vector pET30a(+) in order to produce (His)₆-tagged fusion proteins. Coomassie blue-stained SDS-PAGE and Western blotting identification showed that purity of the fusion proteins.

RESULTS

Immunofluorescence and flow cytometry show that U251 cells were efficiently transduced with the fusion proteins. Cell viability, proliferation, and migration assays suggest that the complete TAT-DCF1 fusion protein significantly decreased U251 proliferation and migration. Flow cytometry further reveals that TAT-DCF1 triggered cellular apoptosis.

CONCLUSIONS

In conclusion, these findings suggest that the TAT-DCF1 fusion protein was efficiently transduced into Glioblastoma U251 cells and induced the antitumor effect and support further investigation into specific targeting and side effects of TAT-DCF1 during drug delivery.

Dual functionalized liposome-mediated gene delivery across triple co-culture blood brain barrier model and specific in vivo neuronal transfection

Gene therapy has become a promising approach for neurodegenerative disease treatment, however there is an urgent need to develop an efficient gene carrier to transport gene across the blood brain barrier (BBB). In this study, we strategically designed dual functionalized liposomes for efficient neuronal transfection by combining transferrin (Tf) receptor targeting and enhanced cell penetration utilizing penetratin (Pen). A triple cell co-culture model of BBB confirmed the ability of the liposomes to cross the barrier layer and transfect primary neuronal cells. In vivo quantification of PenTf-liposomes demonstrated expressive accumulation in the brain (12%), without any detectable cellular damage or morphological change. The efficacy of these nanoparticles containing plasmid β-galactosidase in modulating transfection was assessed by β-galactosidase expression in vivo. As a consequence of accumulation in the brain, PenTf-liposomes significantly induced gene expression in mice. Immunofluorescence studies of brain sections of mice after tail vein injection of liposomes encapsulating pDNA encoding GFP (pGFP) illustrate the superior ability of dual-functionalized liposomes to accumulate in the brain and transfect neurons. Taken together, the multifunctional liposomes provide an excellent gene delivery platform for neurodegenerative diseases.

Functional Analysis of Novicidin Peptide: Coordinated Delivery System for Zinc via Schiff Base Ligand

Novicidin (NVC), is a membrane-penetrating peptide, which forms a stable complex with Zn-Schiff base with interesting antitumor selectivity. We studied NVC derivatives to determine functional roles of key amino acids in toxicity, helicity, and binding of the Zn-Schiff base complex. Trimmed derivatives highlighted the role of peptide length and helicity in toxicity and membrane penetration. The removal of Lys from position 1 and 2 strongly increases the ability to disrupt the membranes. The trimming of the N-terminal residues significantly increases the stability of peptide helicity enhancing penetrating properties. Gly residue derivatives undermined a role of peptide bending in membrane penetration and toxicity. After the substitution of the central Gly derivatives with Ile or Lys, the peptides retained toxicity. These results illustrate the minor role of central helix bending in NVC toxicity. Binding-site-peptide derivatives identified His residue as the sole Zn-Schiff base binding site and eliminated the role of other aromatic residues.

Emerging Methods and Design Principles for Cell-Penetrant Peptides

Biomolecules such as antibodies, proteins, and peptides are important tools for chemical biology and leads for drug development. They have been used to inhibit a variety of extracellular proteins, but accessing intracellular proteins has been much more challenging. In this review, we discuss diverse chemical approaches that have yielded cell-penetrant peptides and identify three distinct strategies: masking backbone amides, guanidinium group patterning, and amphipathic patterning. We summarize a growing number of large data sets, which are starting to reveal more specific design guidelines for each strategy. We also discuss advantages and disadvantages of current methods for quantifying cell penetration. Finally, we provide an overview of best-odds approaches for applying these new methods and design principles to optimize cytosolic penetration for a given bioactive peptide.

Handling FMRP and its molecular partners: Structural insights into Fragile X Syndrome

Fragile X Mental Retardation Protein (FMRP) is a RNA-binding protein (RBP) known to control different steps of mRNA metabolism, even though its complete function is not fully understood yet. Lack or mutations of FMRP lead to Fragile X Syndrome (FXS), the most common form of inherited intellectual disability and a leading monogenic cause of autism spectrum disorder (ASD). It is well established that FMRP has a multi-domain architecture, a feature that allows this RBP to be engaged in a large interaction network with numerous proteins and mRNAs or non-coding RNAs. Insights into the three-dimensional (3D) structure of parts of its three domains (N-terminus, central domain and C-terminus) were obtained using Nuclear Magnetic Resonance and X-ray diffraction, but the complete 3D arrangement of each domain with respect to the others is still missing. Here, we review the structural features of FMRP and of the network of its protein and RNA interactions. Understanding these aspects is the first necessary step towards the design of novel compounds for new therapeutic interventions in FXS.

Octaarginine-modified gold nanoparticles enhance the radiosensitivity of human colorectal cancer cell line LS180 to megavoltage radiation

Background

This study investigated the effectiveness and underpinning mechanisms of radiosensitization using octaarginine (R8)-modified gold nanoparticle–poly(ethylene glycol) (GNP-PEG-R8) in colorectal cancer cell line LS180 to megavoltage radiotherapy in vitro.

Method

In-house synthesized GNP-PEG was characterized by transmission electron microscopy, dynamic light scattering, ultraviolet–visible spectrophotometry, and X-ray photoelectron spectroscopy. Inductively coupled plasma mass spectroscopy was used to quantify internalization. Direct cytotoxicity was established using the Cell Counting Kit-8, while radiosensitivity was determined using the gold standard in vitro clonogenic assay. Cell-cycle distribution, apoptosis, reactive oxygen species (ROS), and mitochondrial membrane potential (MMP) were analyzed by flow cytometry, further exploring the key mechanisms driving GNP-PEG-R8 radiosensitization.

Results

The core GNP diameter was 6.3±1.1 nm (mean±SD). Following functionalization, the hydrodynamic diameter increased to 19.7±2.8 nm and 27.8±1.8 nm for GNP-PEG and GNP-PEG-R8, with respective surface plasmon resonance peaks of 515 nm and 525 nm. Furthermore, incorporation of the R8 significantly increased nanoparticle internalization compared to GNP-PEG (p<0.001) over a 1 h treatment period. Functionalized GNPs confer little cytotoxicity below 400 nM. In clonogenic assays, radiation combined with GNP-PEG-R8 induced a significant reduction in colony formation compared with radiation alone, generating a sensitizer enhancement ratio of 1.59. Furthermore, GNP-PEG-R8 plus radiation predominantly induced cell-cycle arrest in the G2/M phase, increasing G2/M stalling by an additional 10% over GNP-PEG, markedly promoting apoptosis (p<0.001). Finally, ROS levels and alterations in MMP were investigated, indicating a highly significant (p<0.001) change in both parameters following the combined treatment of GNP-PEG-R8 and radiation over radiation alone.

Conclusion

R8-modified GNPs were efficiently internalized by LS180 cells, exhibiting minimal cytotoxicity. This yielded significant radiosensitization in response to megavoltage radiation. GNP-PEG-R8 may enhance radiosensitivity by arresting cell cycle and inducing apoptosis, with elevated ROS identified as the likely initiator.

Stereochemistry as a determining factor for the effect of a cell-penetrating peptide on cellular viability and epithelial integrity

Cell-penetrating peptides (CPPs) comprise efficient peptide-based delivery vectors. Owing to the inherent poor enzymatic stability of peptides, CPPs displaying partial or full replacement of l-amino acids with the corresponding d-amino acids might possess advantages as delivery vectors. Thus, the present study aims to elucidate the membrane- and metabolism-associated effects of l-Penetratin (l-PEN) and its corresponding all-d analog (d-PEN). These effects were investigated when exerted on hepatocellular (HepG2) or intestinal (Caco-2 and IEC-6) cell culture models. The head-to-head comparison of these enantiomeric CPPs included evaluation of their effects on cell viability and morphology, epithelial membrane integrity, and cellular ultrastructure. In all investigated cell models, a rapid decrease in cell viability, pronounced membrane perturbation and an altered ultrastructure were detected upon exposure to d-PEN. At equimolar concentrations, these observations were less pronounced or even absent for cells exposed to l-PEN. Both CPPs remained stable for at least 2 h during exposure to proliferating cells (cultured for 24 h), although d-PEN exhibited a longer half-life when compared with that of l-PEN when exposed to well-differentiated cell monolayers (cultured for 18-20 days). Thus, the stereochemistry of the CPP penetratin significantly influences its effects on cell viability and epithelial integrity when profiled against a panel of mammalian cells.

Identification of a cell-penetrating peptide applicable to a protein-based transcription activator-like effector expression system for cell engineering

Cellular reprogramming is a promising technology in regenerative medicine, but most studies have been performed by using expression vectors. For future clinical applications, it is necessary to establish a system in which cell engineering can be manipulated without any risk of damaging the genome. Here, we identified a cell-penetrating peptide composed of 10 amino acids (RIFIHFRIGC) with nuclear trafficking activity and found that it was significantly more potent than a Tat-derived peptide or polyarginine peptide (R11). We named the peptide "nuclear trafficking peptide" (NTP) and applied it to a protein-based artificial transcription factor (NTP-ATF), which was composed of a transcription activator-like effector and transcription domain (VP64). An NTP-ATF designed to the proximal promoter region of the microRNA-302/367 cluster efficiently induced endogenous RNA expression at an extremely low concentration (0.25 nM), and repetitive treatment of mouse embryonic fibroblasts with NTP-ATF generated induced pluripotent stem-like cells, which gave chimeric mice. Together with the observation that recombinant NTP-ATF protein did not induce any apparent cytotoxicity, we propose that NTP-ATF is a promising system for cellular reprogramming applicable to regenerative medicine.

Catalytically Active Single-Chain Polymeric Nanoparticles: Exploring Their Functions in Complex Biological Media

Dynamic single-chain polymeric nanoparticles (SCPNs) are intriguing, bioinspired architectures that result from the collapse or folding of an individual polymer chain into a nanometer-sized particle. Here we present a detailed biophysical study on the behavior of dynamic SCPNs in living cells and an evaluation of their catalytic functionality in such a complex medium. We first developed a number of delivery strategies that allowed the selective localization of SCPNs in different cellular compartments. Live/dead tests showed that the SCPNs were not toxic to cells while spectral imaging revealed that SCPNs provide a structural shielding and reduced the influence from the outer biological media. The ability of SCPNs to act as catalysts in biological media was first assessed by investigating their potential for reactive oxygen species generation. With porphyrins covalently attached to the SCPNs, singlet oxygen was generated upon irradiation with light, inducing spatially controlled cell death. In addition, Cu(I)- and Pd(II)-based SCPNs were prepared and these catalysts were screened in vitro and studied in cellular environments for the carbamate cleavage reaction of rhodamine-based substrates. This is a model reaction for the uncaging of bioactive compounds such as cytotoxic drugs for catalysis-based cancer therapy. We observed that the rate of the deprotection depends on both the organometallic catalysts and the nature of the protective group. The rate reduces from in vitro to the biological environment, indicating a strong influence of biomolecules on catalyst performance. The Cu(I)-based SCPNs in combination with the dimethylpropargyloxycarbonyl protective group showed the best performances both in vitro and in biological environment, making this group promising in biomedical applications.

Scalable production of core-shell nanoparticles by flash nanocomplexation to enhance mucosal transport for oral delivery of insulin

Scalable manufacturing continues to present a major barrier for clinical translation of nanotherapeutics. Methods available for fabricating protein-encapsulating nanoparticles in a scalable fashion are scarce. Protein delivery often requires multiple functionalities to be incorporated into the same vehicle. Specifically for nanoparticle-mediated oral delivery of protein therapeutics, protection in GI tract, site-specific release, facilitating transmucosal permeation, and enhancing epithelial transport are a few desirable features to be engineered into a nanoparticle system. Here we devised a sequential flash nanocomplexation (FNC) technique for the scalable production of a core-shell structured nanoparticle system by combining materials choice and particle size and structure to fulfill these functions, therefore enhancing the delivery efficiency of insulin. This method is highly effective in controlling the size, generating core-shell structure with high encapsulation efficiency (97%) and payload capacity (67%) using insulin/l-penetratin complex nanoparticles as a core coated with hyaluronic acid (HA). Both the in vitro and in vivo models confirmed that the HA coating on these core-shell nanoparticles enhanced the permeation of nanoparticles through the intestinal mucus layer and improved trans-epithelial absorption of insulin nanoparticles; and the enhancement effect was most prominent using HA with the highest average molecular weight. The insulin-loaded nanoparticles were then encapsulated into enteric microcapsules (MCs) in an FNC process to provide additional protection against the acidic environment in the stomach while allowing rapid release of insulin nanoparticles when they reach small intestine. The optimized multifunctional MCs delivered an effective glucose reduction in a Type I diabetes rat model following a single oral administration, yielding a relative bioavailability of 11% in comparison with subcutaneous injection of free-form insulin. This FNC technique is highly effective in controlling particle size and structure to improve delivery properties and function. It can be easily extended to oral delivery for other protein therapeutics.

Biophysical characterisation of the recombinant human frataxin precursor

Friedreich's ataxia is a disease caused by a decrease in the levels of expression or loss of functionality of the mitochondrial protein frataxin (FXN). The development of an active and stable recombinant variant of FXN is important for protein replacement therapy. Although valuable data about the mature form FXN81-210 has been collected, not enough information is available about the conformation of the frataxin precursor (FXN1-210). We investigated the conformation, stability and function of a recombinant precursor variant (His6-TAT-FXN1-210), which includes a TAT peptide in the N-terminal region to assist with transport across cell membranes. His6-TAT-FXN1-210 was expressed in Escherichia coli and conditions were found for purifying folded protein free of aggregation, oxidation or degradation, even after freezing and thawing. The protein was found to be stable and monomeric, with the N-terminal stretch (residues 1-89) mostly unstructured and the C-terminal domain properly folded. The experimental data suggest a complex picture for the folding process of full-length frataxin in vitro: the presence of the N-terminal region increased the tendency of FXN to aggregate at high temperatures but this could be avoided by the addition of low concentrations of GdmCl. The purified precursor was translocated through cell membranes. In addition, immune response against His6-TAT-FXN1-210 was measured, suggesting that the C-terminal fragment was not immunogenic at the assayed protein concentrations. Finally, the recognition of recombinant FXN by cellular proteins was studied to evaluate its functionality. In this regard, cysteine desulfurase NFS1/ISD11/ISCU was activated in vitro by His6-TAT-FXN1-210. Moreover, the results showed that His6-TAT-FXN1-210 can be ubiquitinated in vitro by the recently identified frataxin E3 ligase RNF126, in a similar way as the FXN1-210, suggesting that the His6-TAT extension does not interfere with the ubiquitination machinery.

Modified mixed nanomicelles with collagen peptides enhanced oral absorption of Cucurbitacin B: preparation and evaluation

Polymer nanoparticles modified with collagen peptides (CPs) are an attractive strategy for the oral delivery of active ingredients from Chinese medicine. Thus, in the present study, collagen cationic CPs were simply separated using ion-exchange resin from bovine CPs, to modify mixed nanomicelles (MMs) on the surface to improve the oral bioavailability of Cucurbitacin B (CuB). The physicochemical property of micelles was characterized, which confirmed the successful modification of the nanomicelles. CPs-modified nanomicelles in vitro were found to significantly increase cellular uptake and transportation. Compared to unmodified micelles, the quantity of CPs-modified micelles internalized by Caco-2 cells were 3.74 times greater and the cumulative transportation flux (AP-BL) was 2.81 times greater. The membrane transportation process of CuB-MMs-CPs was found to be associated with energy consumption and clathrin- and caveolin-mediated endocytosis. In vivo studies performed on rats indicated that in comparison to CuB and CuB-MMs, the relative bioavailability of CuB-MMs-CPs increased by 3.43 times and 2.14 times, respectively. In addition, the tumor inhibition caused by CuB-MMs-CPs was increased significantly. Therefore, the nanomicelles co-modified with isolated CPs could act as attractive carriers for oral delivery of CuB.

TGF-β signaling in cancer metastasis

The transforming growth factor (TGF)-β signaling events are well known to control diverse processes and numerous responses, such as cell proliferation, differentiation, apoptosis, and migration. TGF-β signaling plays context-dependent roles in cancer: in pre-malignant cells TGF-β primarily functions as a tumor suppressor, while in the later stages of cancer TGF-β signaling promotes invasion and metastasis. Recent studies have also suggested that the cross-talk between TGF-β signaling and other signaling pathways, such as Hippo, Wnt, EGFR/RAS, and PI3K/AKT pathways, may substantially contribute to our current understanding of TGF-β signaling and cancer. As a result of the wide-ranging effects of TGF-β, blockade of TGF-β and its downstream signaling components provides multiple therapeutic opportunities. Therefore, the outlook for anti-TGF-β signaling therapy for numerous diseases appears bright and will provide valuable information and thinking on the drug molecular design. In this review, we focus on recent insights into the regulation of TGF-β signaling in cancer metastasis which may contribute to the development of novel cancer-targeting therapies.

Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions

Here we present a protocol to study intracellular protein-protein interactions that is based on the widely used biotin-avidin pull-down system. The modification presented includes the combination of this technique with cell-penetrating sequences. We propose to design cell-penetrating baits that can be incubated with living cells instead of cell lysates and therefore the interactions found will reflect those that occur within the intracellular context. Connexin43 (Cx43), a protein that forms gap junction channels and hemichannels is down-regulated in high-grade gliomas. The Cx43 region comprising amino acids 266-283 is responsible for the inhibition of the oncogenic activity of c-Src in glioma cells. Here we use TAT as the cell-penetrating sequence, biotin as the pull-down tag and the region of Cx43 comprised between amino acids 266-283 as the target to find intracellular interactions in the hard-to-transfect human glioma stem cells. One of the limitations of the proposed method is that the molecule used as bait could fail to fold properly and, consequently, the interactions found could not be associated with the effect. However, this method can be especially interesting for the interactions involved in signal transduction pathways because they are usually carried out by intrinsically disordered regions and, therefore, they do not require an ordered folding. In addition, one of the advantages of the proposed method is that the relevance of each residue on the interaction can be easily studied. This is a modular system; therefore, other cell-penetrating sequences, other tags, and other intracellular targets can be employed. Finally, the scope of this protocol is far beyond protein-protein interaction because this system can be applied to other bioactive cargoes such as RNA sequences, nanoparticles, viruses or any molecule that can be transduced with cell-penetrating sequences and fused to pull-down tags to study their intracellular mechanism of action.

Fluorescent and Photosensitizing Conjugates of Cell-Penetrating Peptide TAT(47-57): Design, Microwave-Assisted Synthesis at 60 °C, and Properties

Conjugates based on cell-penetrating peptides (CPPs) are scientifically relevant owing to their structural complexity; their ability to enter cells and deliver drugs, labels, antioxidants, bioactive compounds, or DNA fragments; and, consequently, their potential for application in research and biomedicine. In this study, carboxyamidated fluorescently labeled conjugates FAM-GG-TAT(47-57)-NH2 and FAM-PEG6-TAT(47-57)-NH2 and photosensitizer-labeled conjugate Chk-PEG6-TAT(47-57)-NH2 [where TAT(47-57) is the CPP, 5(6)-carboxyfluorescein is the (FAM) fluorophore, chlorin k (Chk) is the photosensitizer, and the dipeptide glycyl-glycine (GG) or hexaethylene glycol (PEG6) is the spacer] were originally designed, prepared, and fully characterized. Practically, all chemical reactions of the synthetic steps (peptide synthesis, spacer incorporation, and conjugation) were microwave-assisted at 60 °C using optimized protocols to give satisfying yields and high-quality products. Detailed analyses of the conjugates using spectrofluorimetry and singlet oxygen detection showed that they display photophysical properties typical of FAM or Chk. Anticandidal activity assays showed that not only this basic property of TAT(47-57) was preserved in the conjugates but also that the minimal inhibitory concentration was slightly reduced for cells incubated with PS-bearing conjugate Chk-PEG6-TAT(47-57)-NH2. Overall, these results indicated that the synthetic approach on-resin assisted by microwaves at 60 °C is simple, straightforward, selective, metal-free, sufficiently fast, cleaner, and more cost-effective than those previously used for preparing this type of macromolecule. Furthermore, such new data show that microwaves at 60 °C and/or conjugation did not harm the integrity of the conjugates' constituents. Therefore, FAM-GG-TAT(47-57)-NH2, FAM-PEG6-TAT(47-57)-NH2, and Chk-PEG6-TAT(47-57)-NH2 have high potential for practical applications in biochemistry, biophysics, and therapeutics.