Recent in vivo advances in cell-penetrating peptide-assisted drug delivery

ABSTRACT

Introduction: Delivery of macromolecular drugs is an important field in medical research. However, macromolecules are usually unable to cross the cell membrane without the assistance of a delivery system. Cell penetrating peptides (CPPs) are unique tools to gain access to the cell interior and deliver a bioactive cargo into the cytosol or nucleus. In addition to macromolecular delivery, CPPs have been used to deliver smaller bioactive molecules. Therefore CPPs have become an intensive field of research for medical treatment.

Areas covered: In this review, we highlight studies that include CPP in vivo disease models. We review different strategies and approaches that have been used, with specific attention on recent publications. The approaches that have been used include CPP–cargo covalent conjugation strategies and nanoparticle strategies. Various additional strategies have been used to achieve disease targeting, including active targeting, passive targeting, and combined active/passive strategies. As a result, delivery of various types of molecule has been achieved, including small drug molecules, proteins and nucleic acid-based macromolecules (e.g. siRNA, antisense nucleotides and plasmid DNA).

Expert Opinion: Despite recent advances in the field, confusions surrounding CPP internalization mechanisms and intracellular trafficking are hindering the development of new and more efficient vectors. Nevertheless, the recent increase in the number of publications containing in vivo CPP utilization looks promising that the number of clinical trials would also increase in the near future.     

Recent CPP-based applications in medicine

ABSTRACT

Introduction: Cell-penetrating peptides (CPP) offer versatile tools for the field of drug delivery and development of macromolecular therapeutics. These tools have matured into applications that allow the use of proteins, nucleic acid, peptides, imaging agents, and low molecular weight drugs as therapeutic entities.

Areas covered: The progress of the field is discussed in the current review, with the examples from a recent couple of years, in the utilization of CPPs in medicine. Specific focus is on the research articles that include applications that have direct translational value. Progress with protein mimicry and its recent leap in medicine is discussed with special attention, but also achievements with nanoformulation and drug targeting is presented.

Expert opinion: The opinion section discusses some of the limitations and shortcomings, proposing the areas where more effort should be invested in order to increase the translational value of the current preclinical research.     

细胞穿膜肽在癌症治疗中的应用

细胞膜有选择渗透性,能阻止大多数外来因子进入细胞。然而许多治疗因子必须穿过细胞膜才能进入细胞内起作用。细胞穿膜肽是一组简短的阳离子序列,它具有很强的穿膜能力。自从1988年发现细胞穿膜肽后,细胞穿膜肽被用于携带各种物质,如小分子、核酸、抗体、纳米粒等进入细胞膜。本文重点介绍了近几年来关于细胞穿膜肽穿膜机制的研究进展,以及细胞穿膜肽作为运载体携带抗癌药物靶向进入肿瘤细胞,从而实现对肿瘤细胞的靶向性,同时可克服肿瘤的多药抗药性等研究进展。     

Trends in the biological functions and medical applications of extracellular vesicles and analogues

Natural extracellular vesicles (EVs) play important roles in many life processes such as in the intermolecular transfer of substances and genetic information exchanges. Investigating the origins and working mechanisms of natural EVs may provide an understanding of life activities, especially regarding the occurrence and development of diseases. Additionally, due to their vesicular structure, EVs (in small molecules, nucleic acids, proteins, etc.) could act as efficient drug-delivery carriers. Herein, we describe the sources and biological functions of various EVs, summarize the roles of EVs in disease diagnosis and treatment, and review the application of EVs as drug-delivery carriers. We also assess the challenges and perspectives of EVs in biomedical applications.     

富含脯氨酸的抗菌肽研究进展

富含脯氨酸的抗菌肽是一族分离自动物的线性多肽 ,它们都具有抗菌活性 ,在天然免疫中具有重要的作用。这类抗菌肽按来源又分为两类 :来自哺乳动物的富含脯氨酸的抗菌肽和来自昆虫和其他脊椎动物的富含脯氨酸的抗菌肽。它们都富含脯氨酸 ,对革兰阴性菌起作用 ,其杀菌机制不同于大多抗菌肽的膜溶解作用。它们进入细菌胞质后 ,结合DnaK蛋白 ,抑制DnaK的生物功能 ,最终导致了细菌的死亡。这一作用机制对于药物的开发很有意义。除了抗菌作用外 ,富含脯氨酸的抗菌肽还具有其他重要的药理作用。对这方面作用研究比较多的是PR 39,它在诱导粘连蛋白聚糖在间充质细胞的表达 ,抑制嗜中性粒细胞NADPH氧化酶 ,抑制 1κBα和HIF 1α的降解等方面具有重要作用。这些发现表明PR 39在伤口修复、炎症、缺血再灌注损伤以及诱导血管生成等方面具有很好的应用前景。     

Thermosensitive magnetic liposomes with doxorubicin cell-penetrating peptides conjugate for enhanced and targeted cancer therapy

To specifically deliver cytotoxic drug to tumor cells and enhance cellular uptake is the key for effective cancer therapy. In this paper, we described a novel drug targeting system, which is designed to combine features of biological (cell-penetrating peptides, CPPs) and physical (magnetic) drug targeting for use in the magnetic hyperthermia-triggered release. A doxorubicin–CPPs conjugate (DOX-CPPs) was loaded into thermosensitive magnetic liposomes (TSMLs) (DOX-CPPs/TSMLs), and in vitro DOX-CPPs thermosensitive release activity, anti-proliferation effect, in vivo targeted delivery as well as in vivo antitumor activity were determined. The results demonstrated that the DOX-CPPs/TSMLs showed good physicochemical properties, effective anti-proliferation effect in MCF-7 cells in vitro. Additionally, in vivo study, DOX-CPPs/TSMLs under AC magnetic field displayed superior in vivo targeted delivery efficacy, antitumor efficacy in an MCF-7 xenograft murine model. In conclusion, the application of DOX-CPPs/TSMLs under AC magnetic field may provide a strategy for the selective and efficient delivery of drug.     

穿膜肽的研究进展

穿膜肽是一些具有细胞膜穿透能力的小分子多肽,可有效携带比其分子质量大100倍的外源性疏水大分子进入细胞,并对宿主细胞没有显著毒副作用.穿膜肽存在多种穿膜机制,诸如直接渗透到细胞膜,通过易位形成的一个暂时性的结构和内吞作用介导入膜等.具体的穿膜机制还不清楚,但普遍认为穿膜肽与细胞表面负电荷物质的直接接触是必不可少的.由于穿膜肽的穿膜性质,其在分子生物学、药学、细胞生物学、疫苗学甚至影像学上有广泛的应用前景.本文对近年来穿膜肽的结构、穿膜机制和应用方面的研究进展进行了综述.     

超声微泡介导的基因递送系统应用进展

超声波可聚焦于体内的特定部位。含气体微泡既可以作为医学超声显像的造影剂，又可以作为药物或基因载体。超声微泡有望实现基因的靶向递送，因此成为药物递送系统研究的热门领域。本文阐述了超声微泡介导的基因递送系统在心肌、血管、骨骼肌和肿瘤组织等方面的研究进展，讨论其在未来应用中面临的问题。     

Functional ligands for improving anticancer drug therapy: current status and applications to drug delivery systems

Conventional chemotherapy lacking target selectivity often leads to severe side effects, limiting the effectiveness of chemotherapy. Therefore, drug delivery systems ensuring both selective drug release and efficient intracellular uptake at the target sites are highly demanded in chemotherapy to improve the quality of life of patients with low toxicity. One of the effective approaches for tumor-selective drug delivery is the adoption of functional ligands that can interact with specific receptors overexpressed in malignant cancer cells. Various functional ligands including folic acid, hyaluronic acid, transferrin, peptides, and antibodies, have been extensively explored to develop tumor-selective drug delivery systems. Furthermore, cell-penetrating peptides or ligands for tight junction opening are also actively pursued to improve the intracellular trafficking of anticancer drugs. Sometimes, multiple ligands with different roles are used in combination to enhance the cellular uptake as well as target selectivity of anticancer drugs. In this review, the current status of various functional ligands applicable to improve the effectiveness of cancer chemotherapy is overviewed with a focus on their roles, characteristics, and preclinical/clinical applications.     

Efficiency of cell-penetrating peptides on the nasal and intestinal absorption of therapeutic peptides and proteins

The purpose of our study was to investigate the potential of cell-penetrating peptides; penetratin as novel delivery vector, on the systemic absorption of therapeutic peptides and proteins across different mucosal administration sites. The absorption-enhancing feasibility of l- and d-penetratin (0.5 mM) was used for glucagon-like peptide-1 (GLP-1), and exendin-4 as novel antidiabetic therapy, in addition to interferon-β (IFN-β) as protein biotherapeutic model from nasal and intestinal route of administration was evaluated as first time in rats. Nasal route is the most feasible for the delivery of therapeutic peptides coadministered with penetratin whereas the intestinal route appears to be more restricted. The absolute bioavailability (BA (%)) values depend on the physichochemical characters of drugs, stereoisomer character of penetratin, and site of administration. Penetratin significantly increased the nasal more than intestinal absorption of GLP-1 and exendin-4, as the BA for nasal and intestinal administration of GLP-1 was 15.9% and 5%, and for exendin-4 were 7.7% and 1.8%, respectively. Moreover, the BA of IFN-β coadministered with penetratin was 11.1% and 0.17% for nasal and intestinal administration, respectively. From these findings, penetratin is a promising carrier for transmucosal delivery of therapeutic peptides and macromolecules as an alternative to conventional parenteral routes.     

Recent advances in cell membrane-camouflaged nanoparticles for inflammation therapy

During inflammation, inflammatory cells are rapidly recruited to sites of infection or injury, where they cross physiological barriers around the infected site and further infiltrate into the tissues. Other cells, such as erythrocytes, endothelial cells and stem cells, also play prominent roles in host defense and tissue repair. In recent years, nanotechnology has been exploited to deliver drugs to sites of inflammation. For example, nanoparticles camouflaged with a cell membrane are a novel drug-delivery platform that can interact with the immune system and that show great potential for treating inflammation. Encapsulating drugs inside plasma membranes derived from various cells involved in inflammatory processes can be effective against inflammation. This review describes the preparation, characterization, and properties of various types of cell membrane-camouflaged biomimetic nanoparticles. It also summarizes preclinical research into their efficacy against inflammation.     

Recent advances in natriuretic peptides in congestive heart failure

Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) are secreted by the heart and play important roles in the compensation of congestive heart failure with their vasodilating, natriuretic, antiproliferative, lusitropic and neurohumoral-modulating properties. Based on these beneficial properties, exogenous BNP was developed as a new treatment for congestive heart failure and approved in the US for acute decompensated heart failure. New therapeutic strategies for heart failure that are currently being investigated include chronic subcutaneous BNP administration and intermittent BNP infusions. Furthermore, strategies combining exogenous BNP with an inhibitor of the BNP-degrading enzyme neutral endopeptidase could contribute to maximising the actions of BNP and reduce the amount of exogenous BNP needed.     

Cell penetrating peptides: the potent multi-cargo intracellular carriers

ABSTRACT

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.     

Advances in the delivery of antisense oligonucleotides for combating bacterial infectious diseases

Discovery and development of new antibacterial drugs against multidrug resistant bacterial strains have become more and more urgent. Antisense oligonucleotides (ASOs) show immense potential to control the spread of resistant microbes due to its high specificity of action, little risk to human gene expression, and easy design and synthesis to target any possible gene. However, efficient delivery of ASOs to their action sites with enough concentration remains a major obstacle, which greatly hampers their clinical application. In this study, we reviewed current progress on delivery strategies of ASOs into bacteria, focused on various non-virus gene vectors, including cell penetrating peptides, lipid nanoparticles, bolaamphiphile-based nanoparticles, DNA nanostructures and Vitamin B12. The current review provided comprehensive understanding and novel perspective for the future application of ASOs in combating bacterial infections.     

细胞穿膜肽作为药物载体的研究进展

生物大分子在许多疾病的治疗中发挥着重要的作用, 但由于细胞膜的天然屏障作用, 只有分子质量小于600 Da的分子才能穿透细胞膜进入细胞内。这使得一些有治疗价值但无细胞膜穿透性的分子在细胞生物学、药学等领域的应用受到极大的限制。近年来发现的一些具有细胞穿透功能的短肽 (少于30个氨基酸) 即细胞穿膜肽 (CPPs), 能够有效地将蛋白质、多肽、核酸片段等以多种方式导入多种哺乳动物细胞, 其转导效率高且不会造成细胞损伤。CPPs的发现为生物大分子在细胞生物学、基因治疗、药物体内转运、临床药效评价以及细胞免疫学等研究领域等均具有良好的应用前景。本文就CPPs的种类特点、内化机制、应用及其存在的问题进行讨论和评述。     

The use of cell-penetrating peptides for drug delivery

In the past decade, several peptides that can translocate cell membranes have been identified. Some of these peptides, which can be divided into different families, have short amino acid sequences (10-27 residues in length) and enter the cell by a receptor-independent mechanism. Furthermore, these peptides are capable of internalizing hydrophilic cargoes. Although the detailed mechanism by which these molecules enter cells is poorly understood, their ability to traverse the membrane into the cytoplasm has provided a new and powerful biological tool for transporting drugs across cell membranes.     

细胞促渗肽在透皮给药中的应用

细胞促渗肽（CPP）最早于细胞研究中发现,此后被引入透皮制剂领域,相关透皮机制尚未阐明。CPP在透皮制剂领域中应用广泛,对小分子药物、多肽、蛋白质、核酸和胶粒载体均有皮肤促渗作用。本文综述CPP在透皮领域中的应用。     

Therapeutic delivery opportunities, obstacles and applications for cell-penetrating peptides

Advancements in the development of large bioactive molecules as therapeutic agents have made drug delivery an active and important field of research. Cell-penetrating peptides (CPPs) have the ability to deliver an array of molecules and even nano-size particles into cells in an efficient and non-toxic manner, both in vitro and in vivo. This review aims to give a perspective on the obstacles that CPP-mediated drug delivery is currently facing as well as the great opportunities for improvements that lie ahead. Strategies for delivery of novel gene-modulating agents and enhancing efficacy of classical drugs will be discussed, as well as methods for increasing bioavailability and tissue specificity of CPPs. The usefulness and potential of CPPs as therapeutic drug-delivery vectors will be exemplified by their use in the treatment of cancer, viral infection and muscular dystrophy.     

Recent advances in polymeric materials for the delivery of RNA therapeutics

ABSTRACT

Introduction: The delivery of nucleic acid therapeutics through non-viral carriers face multiple biological barriers that reduce their therapeutic efficiency. Despite great progress, there remains a significant technological gap that continues to limit clinical translation of these nanocarriers. A number of polymeric materials are being exploited to efficiently deliver nucleic acids and achieve therapeutic effects.

Areas covered: We discuss the recent advances in the polymeric materials for the delivery of nucleic acid therapeutics. We examine the use of common polymer architectures and highlight the challenges that exist for their development from bench side to clinic. We also provide an overview of the most notable improvements made to circumvent such challenges, including structural modification and stimuli-responsive approaches, for safe and effective nucleic acid delivery.

Expert opinion: It has become apparent that a universal carrier that follows ‘one-size’ fits all model cannot be expected for delivery of all nucleic acid therapeutics. Carriers need to be designed to exhibit sensitivity and specificity toward individual targets diseases/indications, and relevant subcellular compartments, each of which possess their own unique challenges. The ability to devise synthetic methods that control the molecular architecture enables the future development that allow for the construction of ‘intelligent’ designs.     

31P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin

The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R₈, R₁₁, and YKA) through skin intercellular lipids using ³¹P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0–60, 61–120, and 121–180 μm) were collected and analyzed for ³¹P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200 mg/ml of TAT on skin layers, diffusion of TAT, R₈, R₁₁, and YKA in the skin and time dependent permeation of R₁₁ was measured on various skin sections using ³¹P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in ³¹P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100 mg/ml CPP concentration. R₁₁ and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R₁₁ penetration up to 180 μm within 30 min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, ³¹P solid-state NMR can be used to track CPP penetration into different skin layers.