Self-assembled peptide (CADY-1) improved the clinical application of doxorubicin

Cell-Penetrating Peptides: A Powerful Tool for Targeted Drug Delivery

The cellular membrane hinders the effective delivery of therapeutics to targeted sites. Cellpenetrating peptide (CPP) is one of the best options for rapidly internalizing across the cellular membrane. CPPs have recently attracted lots of attention because of their excellent transduction efficiency and low cytotoxicity. The CPP-cargo complex is an effective and efficient method of delivering several chemotherapeutic agents used to treat various diseases. Additionally, CPP has become another strategy to overcome some of the current therapeutic agents' limitations. However, no CPP complex is approved by the US FDA because of its limitations and issues. In this review, we mainly discuss the cellpenetrating peptide as the delivery vehicle, the cellular uptake mechanism of CPPs, their design, and some strategies to synthesize the CPP complex via some linkers such as disulfide bond, oxime, etc. Here, we also discuss the recent status of CPPs in the market.

pH-Responsive Self-Assembling Peptide-Based Biomaterials: Designs and Applications

Stimuli-responsive peptide-based biomaterials are increasingly gaining interest for various specific and targeted treatments, including drug delivery and tissue engineering. Among all stimuli, pH can be especially useful because endogenous pH changes are often associated with abnormal microenvironments. pH-Responsive amino acids and organic linkers can be easily incorporated into peptides that self-assemble into various nanostructures. Thus, these largely biocompatible and easily tunable platforms are ideal candidates for drug release and as fibrous materials capable of mimicking the native extracellular matrix. In this review, we highlight common design motifs and mechanisms of pH-responsiveness in self-assembling peptide-based biomaterials, focusing on recent advances of these biomaterials applied in drug delivery and tissue engineering. Finally, we suggest future challenges and areas for potential development in pH-responsive self-assembling peptide-based biomaterials.

Cell-penetrating peptides improve pharmacokinetics and pharmacodynamics of anticancer drugs

This review concentrates on the research concerning conjugates of anticancer drugs with versatile cell-penetrating peptides (CPPs). For a better insight into the relationship between the components of the constructs, it starts with the characteristic of the peptides and considers its following aspects: mechanisms of cellular internalization, interaction with cancer-modified membranes, selectivity against tumor tissue. Also, CPPs with anticancer activity have been distinguished and summarized with their mechanisms of action. With respect to the conjugates, the preclinical studies (in vitro, in vivo) indicated that they possess several merits in comparison to the parent drugs. They concerned not only better cellular internalization but also other improvements in pharmacokinetics (e.g. access to the brain tissue) and pharmacodynamics (e.g. overcoming drug resistance). The anticancer activity of the conjugates was usually superior to that of the unconjugated drug. Certain anticancer CPPs and conjugates entered clinical trials.

The antimetastatic breast cancer activity of the viral protein-derived peptide vCPP2319 as revealed by cellular biomechanics

The incidence of metastatic breast cancer (MBC) is increasing and the therapeutic arsenal available to fight it is insufficient. Brain metastases, in particular, represent a major challenge for chemotherapy as the impermeable nature of the blood–brain barrier (BBB) prevents most drugs from targeting cells in the brain. For their ability to transpose biological membranes and transport a broad spectrum of bioactive cargoes, cell‐penetrating peptides (CPPs) have been hailed as ideal candidates to deliver drugs across biological barriers. A more ambitious approach is to have the CPP as a drug itself, capable of both killing cancer cells and interacting with the blood/brain interface, therefore blocking the onset of brain metastases. vCPP2319, a viral protein‐derived CPP, has both properties as it: (a) is selective toward human breast cancer cells (MDA‐MB‐231) and increases cell stiffness compared to breast epithelial cells (MCF 10A) hindering the progression of metastases; and (b) adsorbs at the surface of human brain endothelial cells potentially counteracting metastatic cells from reaching the brain. Overall, the results reveal the selective anticancer activity of the peptide vCPP2319, which is also able to reside at the blood–brain interface, therefore counteracting brain penetration by metastatic cancer cells.

Delivery of Various Cargos into Cancer Cells and Tissues via Cell-Penetrating Peptides: A Review of the Last Decade

Cell-penetrating peptides (CPPs), also known as protein transduction domains, are a class of diverse amino acid sequences with the ability to cross cellular membranes. CPPs can deliver several bioactive cargos, including proteins, peptides, nucleic acids and chemotherapeutics, into cells. Ever since their discovery, synthetic and natural CPPs have been utilized in therapeutics delivery, gene editing and cell imaging in fundamental research and clinical experiments. Over the years, CPPs have gained significant attention due to their low cytotoxicity and high transduction efficacy. In the last decade, multiple investigations demonstrated the potential of CPPs as carriers for the delivery of therapeutics to treat various types of cancer. Besides their remarkable efficacy owing to fast and efficient delivery, a crucial benefit of CPP-based cancer treatments is delivering anticancer agents selectively, rather than mediating toxicities toward normal tissues. To obtain a higher therapeutic index and to improve cell and tissue selectivity, CPP-cargo constructions can also be complexed with other agents such as nanocarriers and liposomes to obtain encouraging outcomes. This review summarizes various types of CPPs conjugated to anticancer cargos. Furthermore, we present a brief history of CPP utilization as delivery systems for anticancer agents in the last decade and evaluate several reports on the applications of CPPs in basic research and preclinical studies.

Emerging self-assembling peptide nanomaterial for anti-cancer therapy

Recently it is mainly focused on anti-tumor comprehensive treatments like finding target tumor cells or activating immune cells to inhibit tumor recurrence and metastasis. At present, chemotherapy and molecular-targeted drugs can inhibit tumor cell growth to a certain extent. However, multi-drug resistance and immune escape often make it difficult for new drugs to achieve expected effects. Peptide hydrogel nanoparticles is a new type of biological material with functional peptide chains as the core and self-assembling peptide (SAP) as the framework. It has a variety of significant biological functions, including effective local inflammation suppression and non-drug-resistant cell killing. Besides, it can induce immune activation more persistently in an adjuvant independent manner when compared with simple peptides. Thus, SAP nanomaterial has great potential in regulating cell physiological functions, drug delivery and sensitization, vaccine design and immunotherapy. Not only that, it is also a potential way to focus on some specific proteins and cells through peptides, which has already been examined in previous research. A full understanding of the function and application of SAP nanoparticles can provide a simple and practical strategy for the development of anti-tumor drugs and vaccine design, which contributes to the historical transition of peptide nanohydrogels from bench to bedside and brings as much survival benefits as possible to cancer patients.

Cell-penetrating peptides (CPPs): an overview of applications for improving the potential of nanotherapeutics

In the field of nanotherapeutics, gaining cellular entry into the cytoplasm of the target cell continues to be an ultimate challenge. There are many physicochemical factors such as charge, size and molecular weight of the molecules and delivery vehicles, which restrict their cellular entry. Hence, to dodge such situations, a class of short peptides called cell-penetrating peptides (CPPs) was brought into use. CPPs can effectively interact with the cell membrane and can assist in achieving the desired intracellular entry. Such strategy is majorly employed in the field of cancer therapy and diagnosis, but now it is also used for other purposes such as evaluation of atherosclerotic plaques, determination of thrombin levels and HIV therapy. Thus, the current review expounds on each of these mentioned aspects. Further, the review briefly summarizes the basic know-how of CPPs, their utility as therapeutic molecules, their use in cancer therapy, tumor imaging and their assistance to nanocarriers in improving their membrane penetrability. The review also discusses the challenges faced with CPPs pertaining to their stability and also mentions the strategies to overcome them. Thus, in a nutshell, this review will assist in understanding how CPPs can present novel possibilities for resolving the conventional issues faced with the present-day nanotherapeutics.

Challenge to overcome current limitations of cell-penetrating peptides

The penetration of biological membranes is a prime obstacle for the delivery of pharmaceutical drugs. Cell-penetrating peptide (CPP) is an efficient vehicle that can deliver various cargos across the biological membranes. Since the discovery, CPPs have been rigorously studied to unveil the underlying penetrating mechanism as well as to exploit CPPs for various biomedical applications. This review will focus on the various strategies to overcome current limitations regarding stability, selectivity, and efficacy of CPPs.

ITP-Pred: an interpretable method for predicting, therapeutic peptides with fused features low-dimension representation

The peptide therapeutics market is providing new opportunities for the biotechnology and pharmaceutical industries. Therefore, identifying therapeutic peptides and exploring their properties are important. Although several studies have proposed different machine learning methods to predict peptides as being therapeutic peptides, most do not explain the decision factors of model in detail. In this work, an Interpretable Therapeutic Peptide Prediction (ITP-Pred) model based on efficient feature fusion was developed. First, we proposed three kinds of feature descriptors based on sequence and physicochemical property encoded, namely amino acid composition (AAC), group AAC and coding autocorrelation, and concatenated them to obtain the feature representation of therapeutic peptide. Then, we input it into the CNN-Bi-directional Long Short-Term Memory (BiLSTM) model to automatically learn recognition of therapeutic peptides. The cross-validation and independent verification experiments results indicated that ITP-Pred has a higher prediction performance on the benchmark dataset than other comparison methods. Finally, we analyzed the output of the model from two aspects: sequence order and physical and chemical properties, mining important features as guidance for the design of better models that can complement existing methods.

Ridaifen-F conjugated with cell-penetrating peptides inhibits intracellular proteasome activities and induces drug-resistant cell death

Ridaifen-F (RID-F) potently inhibits proteolytic activities of the 20S proteasome but poorly inhibits those of the 26S proteasome. Here, we report preparation of several conjugates in which various peptides are connected to RID-F. Conjugates with peptides consisting of seven amino acid residues significantly inhibited the 26S proteasome. Particularly, RID-F conjugated to an octaarginine peptide (R₈, a so-called cell-penetrating peptide) inhibited intracellular proteasome activities and induced cell death in drug-resistant KMS-11 myeloma cells. RID-F conjugated to hydrophobic peptides also inhibited the 26S proteasome but failed to induce cell death, suggesting poor penetration into cells. We infer that the R₈ peptide has dual functions: (1) rapid penetration of conjugates into the cell increases intracellular drug concentrations sufficient for exhibition of its effect, and (2) recognition of the conjugates by the 26S proteasome stimulates drug entry into the catalytic chamber. In the presence of ATPγS, RID-F conjugates containing R₈ inhibited the 26S proteasome more potently than in the presence of ATP, suggesting efficient entry of drugs into the catalytic chamber in a similar fashion to the substrate. Taken together with docking simulations of RID-F conjugate interactions with proteasome active sites, the second function of R₈ peptide is plausible. Thus, the conjugation of nonpeptidic proteasome inhibitors to a cell-penetrating peptide could represent a viable strategy for overcoming the drug-resistance of tumor cells.

Nanoparticles induced by embedding self-assembling cassette into glucagon-like peptide 1 for improving in vivo stability

The multiple physiologic characteristics of glucagon-like peptide 1 (GLP-1) make it a promising drug candidate for treating type 2 diabetes mellitus. However, the half-life of GLP-1 is short as a result of degradation by dipeptidyl peptidase IV and renal clearance. Stabilizing GLP-1 is therefore critical for its use in drug development. Self-assembling peptides are a class of peptides that undergo spontaneous assembly into ordered nanostructures. Recently, studies of self-assembling peptides as drug carriers have increased because of their enhanced stability. In the present study, GLP-1 was modified to incorporate the structural characteristics of self-assembling peptides aiming to generate a self-assembling GLP-1 derivative. Receptor binding capacity and insulinotropic effects were measured to investigate the physiologic functions of GLP-1, along with morphologic approaches to observe supramolecular formation on self-assembly at the nano scale. Finally, blood glucose regulation and body weight were monitored after administration of selected derivatives. Our findings revealed that cadyglp1e and cadyglp1m both exhibited improved stability even though different nanoshapes were observed for these two self-assembling peptides. Both cadyglp1e and cadyglp1m retained glucoregulatory activity after insulin stimulation and were potent drug candidates for long-acting GLP-1 derivatives to treat type 2 diabetes mellitus. Our findings support the feasibility of introducing self-assembly functions into peptides with poor stabilities, such as GLP-1.-Li, Y., Cui, T., Kong, X., Yi, X., Kong, D., Zhang, J., Liu, C., Gong, M. Nanoparticles induced by embedding self-assembling cassette into glucagon-like peptide 1 for improving in vivo stability.

The in vitro, in vivo antifungal activity and the action mode of Jelleine-I against Candida species

Recently, the mortality of life-threatening fungal infections increased dramatically. However, there are few antifungals existed. Antimicrobial peptides (AMPs) as promising antifungal candidates have attracted much attention. Here, we present a small antimicrobial peptide Jelleine-I that had potent in vitro and in vivo antifungal activity. Negligible hemolytic activity and in vivo toxicity were observed. Selectivity index (SI) of Jelleine-I is at least 4.6 times higher than amphotericin B. Jelleine-I could increase the production of cellular ROS and bind with genome DNA. This may contribute to its antifungal activity. Furthermore, drug resistance is not induced when the fungal cells were repeatedly treated by Jelleine-I. In conclusion, our results suggest that Jelleine-I may have the potential to be developed as a novel antifungal agent.

The Current Role of Cell-Penetrating Peptides in Cancer Therapy

Cell-penetrating peptides (CPPs) are a heterogeneous class of peptides with the ability to translocate across the plasma membrane and to carry attached cargos inside the cell. Two main entry pathways are discussed, as direct translocation and endocytosis , whereas the latter is often favored when bulky cargos are added to the CPP. Attachment to the CPP can be achieved by means of covalent coupling or non-covalent complex formation, depending on the chemical nature of the cargo. Owing to their striking abilities the further development and application of CPP-based delivery strategies has steadily emerged during the past years. However, one main pitfall when using CPPs is their non-selective uptake in nearly all types of cells. Thus, one particular interest lies in the design of targeting strategies that help to circumvent this drawback but still benefit from the potent delivery abilities of CPPs. The following review aims to summarize some of these very recent concepts and to highlight the current role of CPPs in cancer therapy.

Preclinical Evaluation of an Epidermal Growth Factor Receptor-Targeted Doxorubicin-Peptide Conjugate: Toxicity, Biodistribution, and Efficacy in Mice

Doxorubicin (DOX) is known to induce apoptosis and necrosis in healthy tissue resulting in unwanted toxicities. To improve the ability of DOX to more specifically target tumors and minimize undesirable side effects, conjugation of DOX with epidermal growth factor receptor (EGFR)--binding peptide (DOX-EBP) has been developed to deliver DOX to EGFR-overexpressing neoplastic cells. Here, we investigated whether DOX-EBP was able to reduce toxicity and enhance anticancer efficacy in vivo through receptor-mediated targeted delivery system. Nude mice were treated with DOX or DOX-EBP to estimate general toxicity, normal tissue damage, biodistribution, and antitumor efficacy. In addition, the expression levels of EGFR in tumor tissues and normal organs were investigated by Western blotting, and their mRNA expression was analyzed by reverse transcription PCR. This study demonstrated that DOX-EBP was able to effectively decrease the distribution of DOX in normal tissues without EGFR overexpressing and reduce DOX-induced toxicity. On the other hand, the research also confirmed that DOX-EBP was able to preferentially accumulate DOX in EGFR-overexpressing tumor tissues and showed the enhanced anticancer efficacy over free DOX. DOX-EBP could be used for receptor-targeted chemotherapy with less toxicity and greater efficacy of tumor cells overexpressing EGFR. DOX-EBP conjugate is a good therapeutic agent for cancer treatment.

Potent tumor targeting drug release system comprising MMP-2 specific peptide fragment with self-assembling characteristics

Self-assembling peptides are capable of forming a complex containing a cavity where cytotoxic agents can be wrapped in a self-assembling manner. These complexes are beneficial for improving the pharmacological properties and pharmacokinetics of cytotoxic agents, such as doxorubicin and paclitaxel. In the present study, this self-assembling feature was successfully integrated into a hexapeptide with matrix metalloproteinase (MMP)-2 specific targeting activity, producing a supramolecule possessing controlled drug release characteristics. The MMP-2 specific substrate fragment, PVGLIG, makes this supramolecule disassociate in the presence of MMP-2, and this system is considered to be a powerful tool for the treatment of tumors with high expression of MMP-2 or tumor metastasis. Our findings show that this modified self-assembling peptide with the PVGLIG fragment was able to significantly enhance specificity against HT1080 cells, a tumor cell line with high expression of MMP-2. In addition, residence time of the complex in blood was prolonged since paclitaxel was wrapped into the supramolecule. Our results suggest that the modified MMP-2 specific substrate, SAMTA7, could act as a controlled and sustained drug carrier for treatment of tumors with high expression of MMP-2 and for tumor metastasis.

Cell penetrating peptides: efficient vectors for delivery of nanoparticles, nanocarriers, therapeutic and diagnostic molecules

Efficient delivery of therapeutic and diagnostic molecules to the cells and tissues is a difficult challenge. The cellular membrane is very effective in its role as a selectively permeable barrier. While it is essential for cell survival and function, also presents a major barrier for intracellular delivery of cargo such as therapeutic and diagnostic agents. In recent years, cell-penetrating peptides (CPPs), that are relatively short cationic and/or amphipathic peptides, received great attention as efficient cellular delivery vectors due to their intrinsic ability to enter cells and mediate uptake of a wide range of macromolecular cargo such as plasmid DNA (pDNA), small interfering RNA (siRNAs), drugs, and nanoparticulate pharmaceutical carriers. This review discusses the various uptake mechanisms of these peptides. Furthermore, we discuss recent advances in the use of CPP for the efficient delivery of nanoparticles, nanocarriers, DNA, siRNA, and anticancer drugs to the cells. In addition, we have been highlighting new results for improving endosomal escape of CPP-cargo molecules. Finally, pH-responsive and activable CPPs for tumor-targeting therapy have been described.

Cell-penetrating peptides: design, synthesis, and applications

The intrinsic property of cell-penetrating peptides (CPPs) to deliver therapeutic molecules (nucleic acids, drugs, imaging agents) to cells and tissues in a nontoxic manner has indicated that they may be potential components of future drugs and disease diagnostic agents. These versatile peptides are simple to synthesize, functionalize, and characterize yet are able to deliver covalently or noncovalently conjugated bioactive cargos (from small chemical drugs to large plasmid DNA) inside cells, primarily via endocytosis, in order to obtain high levels of gene expression, gene silencing, or tumor targeting. Typically, CPPs are often passive and nonselective yet must be functionalized or chemically modified to create effective delivery vectors that succeed in targeting specific cells or tissues. Furthermore, the design of clinically effective systemic delivery systems requires the same amount of attention to detail in both design of the delivered cargo and the cell-penetrating peptide used to deliver it.

Nanoinformatics knowledge infrastructures: bringing efficient information management to nanomedical research

Nanotechnology represents an area of particular promise and significant opportunity across multiple scientific disciplines. Ongoing nanotechnology research ranges from the characterization of nanoparticles and nanomaterials to the analysis and processing of experimental data seeking correlations between nanoparticles and their functionalities and side effects. Due to their special properties, nanoparticles are suitable for cellular-level diagnostics and therapy, offering numerous applications in medicine, e.g. development of biomedical devices, tissue repair, drug delivery systems and biosensors. In nanomedicine, recent studies are producing large amounts of structural and property data, highlighting the role for computational approaches in information management. While in vitro and in vivo assays are expensive, the cost of computing is falling. Furthermore, improvements in the accuracy of computational methods (e.g. data mining, knowledge discovery, modeling and simulation) have enabled effective tools to automate the extraction, management and storage of these vast data volumes. Since this information is widely distributed, one major issue is how to locate and access data where it resides (which also poses data-sharing limitations). The novel discipline of nanoinformatics addresses the information challenges related to nanotechnology research. In this paper, we summarize the needs and challenges in the field and present an overview of extant initiatives and efforts.

Self-assembling peptides improve the stability of glucagon-like peptide-1 by forming a stable and sustained complex

The multiple physiological characterizations of glucagon-like peptide-1 (GLP-1) make it a promising drug candidate for the treatment of T2DM. However, the short half-life of GLP-1 limits its clinical utility. Self-assembling peptides are presumed to wrap GLP-1 peptide, and this helps to prolong the stability of GLP-1 consequently. The aim of this study was to investigate whether self-assembling peptides could be applied to prolong the half-life of GLP-1 as sustained release preparations. In this study, five different self-assembling peptides were employed. The formation of the complexes was monitored using gel filtration and mass spectrometry and was simulated by Molecular Dynamics. Stabilization, insulin secretion stimulation, and glucose tolerance tests were performed to investigate the physiological characteristics retained by GLP-1 following complex formation with self-assembling peptides. Our findings revealed that, among the five different self-assembling peptides tested, complex of Pep-1 and GLP-1 exhibited a remarkable extension in the half-life of GLP-1. In addition, the experimental animals treated with a GLP-1/Pep-1 complex exhibited better blood glucose clearance activity over a greater duration of time than the animals treated with GLP-1 alone. Based on our results, an adjustment of the Pep-1 and GLP-1 ratios is presumed to be able to control the half-life of GLP-1 (e.g., medium-acting and long-acting). Collectively, the findings in this study suggest that the self-assembling peptide Pep-1 could serve as a powerful drug preparation tool to extend the short half-life of therapeutic peptides.

In silico approaches for designing highly effective cell penetrating peptides

Background

Cell penetrating peptides have gained much recognition as a versatile transport vehicle for the intracellular delivery of wide range of cargoes (i.e. oligonucelotides, small molecules, proteins, etc.), that otherwise lack bioavailability, thus offering great potential as future therapeutics. Keeping in mind the therapeutic importance of these peptides, we have developed in silico methods for the prediction of cell penetrating peptides, which can be used for rapid screening of such peptides prior to their synthesis.

Methods

In the present study, support vector machine (SVM)-based models have been developed for predicting and designing highly effective cell penetrating peptides. Various features like amino acid composition, dipeptide composition, binary profile of patterns, and physicochemical properties have been used as input features. The main dataset used in this study consists of 708 peptides. In addition, we have identified various motifs in cell penetrating peptides, and used these motifs for developing a hybrid prediction model. Performance of our method was evaluated on an independent dataset and also compared with that of the existing methods.

Results

In cell penetrating peptides, certain residues (e.g. Arg, Lys, Pro, Trp, Leu, and Ala) are preferred at specific locations. Thus, it was possible to discriminate cell-penetrating peptides from non-cell penetrating peptides based on amino acid composition. All models were evaluated using five-fold cross-validation technique. We have achieved a maximum accuracy of 97.40% using the hybrid model that combines motif information and binary profile of the peptides. On independent dataset, we achieved maximum accuracy of 81.31% with MCC of 0.63.

Conclusion

The present study demonstrates that features like amino acid composition, binary profile of patterns and motifs, can be used to train an SVM classifier that can predict cell penetrating peptides with higher accuracy. The hybrid model described in this study achieved more accuracy than the previous methods and thus may complement the existing methods. Based on the above study, a user- friendly web server CellPPD has been developed to help the biologists, where a user can predict and design CPPs with much ease. CellPPD web server is freely accessible at http://crdd.osdd.net/raghava/cellppd/.

Applications of cell-penetrating peptides for tumor targeting and future cancer therapies

Cell-penetrating peptides provide a highly promising strategy for intracellular drug delivery. One relevant clinical application of cell-penetrating peptides is cancer therapeutics. Peptide based delivery could increase the uptake of drugs in tumor cells and thereby increase the efficacy of the treatment, either of conventional small molecular drugs or oligonucleotide based therapeutics. This review is focused on the cancer applications of cell penetrating peptides as delivery systems; different aspects of drug loading, cargoes and delivery are discussed together with methods for targeted delivery, activatable cell-penetrating peptides and transducible agents coupled to cell-penetrating peptides.