Charge Type, Charge Spacing, and Hydrophobicity of Arginine-Rich Cell-Penetrating Peptides Dictate Gene Transfection

Translational use of homing peptides: Tumor and placental targeting

HYPOTHESIS

Tissue-specific homing peptides have been shown to improve chemotherapeutic efficacy due to their trophism for tumor cells. Other sequences that selectively home to the placenta are providing new and safer therapeutics to treat complications in pregnancy. Our hypothesis is that the placental homing peptide RSGVAKS (RSG) may have binding affinity to cancer cells, and that insight can be gained into the binding mechanisms of RSG and the tumor homing peptide CGKRK to model membranes that mimic the primary lipid compositions of the respective cells.

EXPERIMENTS

Following cell culture studies on the binding efficacy of the peptides on a breast cancer cell line, a systematic translational characterization is delivered using ellipsometry, Brewster angle microscopy and neutron reflectometry of the extents, structures, and dynamics of the interactions of the peptides with the model membranes on a Langmuir trough.

FINDINGS

We start by revealing that RSG does indeed have binding affinity to breast cancer cells. The peptide is then shown to exhibit stronger interactions and greater penetration than CGKRK into both model membranes, combined with greater disruption to the lipid component. RSG also forms aggregates bound to the model membranes, yet both peptides bind to a greater extent to the placental than cancer model membranes. The results demonstrate the potential for varying local reservoirs of peptide within cell membranes that may influence receptor binding. The innovative nature of our findings motivates the urgent need for more studies involving multifaceted experimental platforms to explore the use of specific peptide sequences to home to different cellular targets.

Beyond the promise: Exploring the complex interactions of nanoparticles within biological systems

The exploration of nanoparticle applications is filled with promise, but their impact on the environment and human health raises growing concerns. These tiny environmental particles can enter the human body through various routes, such as the respiratory system, digestive tract, skin absorption, intravenous injection, and implantation. Once inside, they can travel to distant organs via the bloodstream and lymphatic system. This journey often results in nanoparticles adhering to cell surfaces and being internalized. Upon entering cells, nanoparticles can provoke significant structural and functional changes. They can potentially disrupt critical cellular processes, including damaging cell membranes and cytoskeletons, impairing mitochondrial function, altering nuclear structures, and inhibiting ion channels. These disruptions can lead to widespread alterations by interfering with complex cellular signaling pathways, potentially causing cellular, organ, and systemic impairments. This article delves into the factors influencing how nanoparticles behave in biological systems. These factors include the nanoparticles' size, shape, charge, and chemical composition, as well as the characteristics of the cells and their surrounding environment. It also provides an overview of the impact of nanoparticles on cells, organs, and physiological systems and discusses possible mechanisms behind these adverse effects. Understanding the toxic effects of nanoparticles on physiological systems is crucial for developing safer, more effective nanoparticle-based technologies.

An assembly-inducing PDC enabling the efficient nuclear delivery of nucleic acid for cancer stem-like cell suppression

Nucleic acid therapy is attracting great attention in diverse clinical translations because of its therapeutic advantages. As a renowned oligonucleotide therapeutical candidate in the clinical stage, AS1411 has shown outstanding tumor suppressing effects; however, its efficient delivery to the cell nucleus is critical for its anticancer effect. Herein, we identified a multifunctional peptide drug conjugate (PDC) as a safe and efficient carrier to achieve the nuclear delivery of AS1411. This PDC consists of the cell penetration peptide RW9, an HDAC inhibitor warhead (peptide C-terminus), and 5-FU (peptide N-terminus), which can coassemble with AS1411 to form nanospheres. The PDC efficiently delivered AS1411 to the nucleus of several types of cancer cells. Moreover, it reversed the stemness of a cancer stem-like cell line. Significantly, due to the assembly-induced accumulation enhancement and retention, a safe single agent concentration of PDC showed unexpected synergy with AS1411 to augment the cancer cell suppression efficiency, exemplified by the downregulation of the stemness-related proteins and the upregulation of apoptosis-related proteins. Therefore, our work presents a powerful strategy for the nuclear delivery of nucleic acid drugs by leveraging cancer-suppressing PDC as assembly inducers, which provides a powerful combination regimen in treating cancer stem-like cells.

Tryptophan, more than just an interfacial amino acid in the membrane activity of cationic cell-penetrating and antimicrobial peptides

Trp is unique among the amino acids since it is involved in many different types of noncovalent interactions such as electrostatic and hydrophobic ones, but also in π-π, π-cation, π-anion and π-ion pair interactions. In membranotropic peptides and proteins, Trp locates preferentially at the water-membrane interface. In antimicrobial or cell-penetrating peptides (AMPs and CPPs respectively), Trp is well-known for its strong role in the capacity of these peptides to interact and affect the membrane organisation of both bacteria and animal cells at the level of the lipid bilayer. This essential amino acid can however be involved in other types of interactions, not only with lipids, but also with other membrane partners, that are crucial to understand the functional roles of membranotropic peptides. This review is focused on this latter less known role of Trp and describes in details, both in qualitative and quantitative ways: (i) the physico-chemical properties of Trp; (ii) its effect in CPP internalisation; (iii) its importance in AMP activity; (iv) its role in the interaction of AMPs with glycoconjugates or lipids in bacteria membranes and the consequences on the activity of the peptides; (v) its role in the interaction of CPPs with negatively charged polysaccharides or lipids of animal membranes and the consequences on the activity of the peptides. We intend to bring highlights of the physico-chemical properties of Trp and describe its extensive possibilities of interactions, not only at the well-known level of the lipid bilayer, but with other less considered cell membrane components, such as carbohydrates and the extracellular matrix. The focus on these interactions will allow the reader to reevaluate reported studies. Altogether, our review gathers dedicated studies to show how unique are Trp properties, which should be taken into account to design future membranotropic peptides with expected antimicrobial or cell-penetrating activity.

Membrane Internalization Mechanisms and Design Strategies of Arginine-Rich Cell-Penetrating Peptides

Cell-penetrating peptides (CPPs) have been discovered to deliver chemical drugs, nucleic acids, and macromolecules to permeate cell membranes, creating a novel route for exogenous substances to enter cells. Up until now, various sequence structures and fundamental action mechanisms of CPPs have been established. Among them, arginine-rich peptides with unique cell penetration properties have attracted substantial scientific attention. Due to the positively charged essential amino acids of the arginine-rich peptides, they can interact with negatively charged drug molecules and cell membranes through non-covalent interaction, including electrostatic interactions. Significantly, the sequence design and the penetrating mechanisms are critical. In this brief synopsis, we summarize the transmembrane processes and mechanisms of arginine-rich peptides; and outline the relationship between the function of arginine-rich peptides and the number of arginine residues, arginine optical isomers, primary sequence, secondary and ternary structures, etc. Taking advantage of the penetration ability, biomedical applications of arginine-rich peptides have been refreshed, including drug/RNA delivery systems, biosensors, and blood-brain barrier (BBB) penetration. Understanding the membrane internalization mechanisms and design strategies of CPPs will expand their potential applications in clinical trials.

In silico and experimental validation of a new modified arginine-rich cell penetrating peptide for plasmid DNA delivery

Cell-penetrating peptides (CPPs) attracted great attention because of the capability to deliver various types of cargo molecules across into the cells. In this study, we presented a new arginine rich CPP, named MR, for efficient transporting plasmid DNA. We used a combined bioinformatic-based approach to improve the speed and accuracy of CPP evaluation. MR protein properties, structural models, interaction with DNA, as well as cell localization and membrane interaction were evaluated through multiple servers. Importantly, analysis using different algorithms showed the high CPP prediction confidence of MR. Experimental results also revealed the capacity of this gene delivery system in vitro for efficient plasmid DNA transfection. Additionally, in vitro mechanistically studies together with bioinformatic investigation suggested that MR peptide may internalize into the cell through endocytosis pathways. Moreover, in silico safety analysis such as immunogenicity, allergenicity, toxicity, and hemolysis activity as well as MTT assay also confirmed the safety of MR peptide. This study illustrated that MR peptide could be presented as remarkable potential gene delivery system for promising transport of plasmid DNA towards the therapeutic applications.

Peptide Self-assembly into stable Capsid-Like nanospheres and Co-assembly with DNA to produce smart artificial viruses

Smart artificial viruses have been successfully developed by co-assembly of de novo designed peptides with DNA, which achieved stimuli-responsibility and efficient gene transfection in cancer cells. The peptides were designed to incorporate several functional segments, including a hydrophobic aromatic segment to drive self-assembly, two or more cysteines to regulate the assemblage shape and stabilize the assembled nanostructures via forming disulfide bonds, several lysines to facilitate co-assembly with DNA and binding to cell membranes, and an enzyme-cleavable segment to introduce cancer sensitivity. The rationally designed peptides self-assembled into stable nanospheres with a uniform diameter of < 10 nm, which worked as capsid-like subunits to further interact with DNA to produce hierarchical virus-mimicking structures by encapsulating DNA in the interior. Such artificial viruses can effectively protect DNA from nuclease digestion and achieve efficient genome release by enzyme-triggered structure disassembly, which ensured a high level of gene transfection in tumor cells. The system emulates very well the structural and functional properties of natural viruses from the aspects of capsid formation, genome package and gene transfection, which is highly promising for application as efficient gene vectors.

Emerging landscape of cell-penetrating peptide-mediated nucleic acid delivery and their utility in imaging, gene-editing, and RNA-sequencing

The safety issues like immunogenicity and unacceptable cancer risk of viral vectors for DNA/mRNA vaccine delivery necessitate the development of non-viral vectors with no toxicity. Among the non-viral strategies, cell-penetrating peptides (CPPs) have been a topic of interest recently because of their ability to cross plasma membranes and facilitate nucleic acids delivery both in vivo and in vitro. In addition to the application in the field of gene vaccine and gene therapy, CPPs based nucleic acids delivery have been proved by its potential application like gene editing, RNA-sequencing, and imaging. Here, we focus on summarizing the recent applications and progress of CPPs-mediated nucleic acids delivery and discuss the current problems and solutions in this field.

Self-assembly of an aptamer-decorated chimeric peptide nanocarrier for targeted cancer gene delivery

In this study, we developed a peptide-based non-viral carrier decorated with aptamer to overcome the specific gene delivery barriers. The carrier (KLN/Apt) was designed to contain multiple functional segments, including 1) two tandem repeating units of low molecular weight protamine (LMWP) to condense DNA into stable nanosize particles and protect it from enzymatic digestion, 2) AS1411 aptamer as targeting moiety to target nucleolin and promote carrier internalization, 3) a synthetic pH-sensitive fusogenic peptide (KALA) for disrupting endosomal membranes and enhancing cytosol escape of the nanoparticles, and 4) a nuclear localization signal (NLS) for active cytoplasmic trafficking and nuclear delivery of DNA. The obtained results revealed the developed carrier capacity in terms of specific cell targeting, overcoming cellular gene delivery barriers, and mediating efficient gene transfection. The KLN/pDNA/aptamer nanoparticles offer remarkable potential for the conceptual design and formation of promising multi-functionalized carriers towards the most demanding therapeutic applications.

Peptide-Based Nanoparticles for Therapeutic Nucleic Acid Delivery

Gene therapy offers the possibility to skip, repair, or silence faulty genes or to stimulate the immune system to fight against disease by delivering therapeutic nucleic acids (NAs) to a patient. Compared to other drugs or protein treatments, NA-based therapies have the advantage of being a more universal approach to designing therapies because of the versatility of NA design. NAs (siRNA, pDNA, or mRNA) have great potential for therapeutic applications for an immense number of indications. However, the delivery of these exogenous NAs is still challenging and requires a specific delivery system. In this context, beside other non-viral vectors, cell-penetrating peptides (CPPs) gain more and more interest as delivery systems by forming a variety of nanocomplexes depending on the formulation conditions and the properties of the used CPPs/NAs. In this review, we attempt to cover the most important biophysical and biological aspects of non-viral peptide-based nanoparticles (PBNs) for therapeutic nucleic acid formulations as a delivery system. The most relevant peptides or peptide families forming PBNs in the presence of NAs described since 2015 will be presented. All these PBNs able to deliver NAs in vitro and in vivo have common features, which are characterized by defined formulation conditions in order to obtain PBNs from 60 nm to 150 nm with a homogeneous dispersity (PdI lower than 0.3) and a positive charge between +10 mV and +40 mV.

The era of gene therapy: From preclinical development to clinical application

Three decades of promise have culminated in the development of gene therapies that can be applied to a broad range of human diseases. After a brief history, we provide an overview of gene therapy types and delivery methods, gene editing technologies, regulatory affairs, clinical trials, approved products, ongoing challenges, and future goals. Information on clinical trials of candidates and on approved products for gene therapy developed between 1988 and 2020 is systematically collated. To obtain this global information, we scanned and reviewed more than 46,000 records of clinical trials from 17 clinical trial database providers. The medical benefits of transformative gene therapies are gradually being accepted by payors, and a significant increase in the number of gene therapy clinical trials and approved gene therapy products has resulted.

Peptides as a material platform for gene delivery: Emerging concepts and converging technologies

Successful gene therapies rely on methods that safely introduce DNA into target cells and enable subsequent expression of proteins. To that end, peptides are an attractive materials platform for DNA delivery, facilitating condensation into nanoparticles, delivery into cells, and subcellular release to enable protein expression. Peptides are programmable materials that can be designed to address biocompatibility, stability, and subcellular barriers that limit efficiency of non-viral gene delivery systems. This review focuses on fundamental structure-function relationships regarding peptide design and their impact on nanoparticle physical properties, biologic activity, and biocompatibility. Recent peptide technologies utilize multi-dimensional structures, non-natural chemistries, and combinations of peptides with lipids to achieve desired properties and efficient transfection. Advances in DNA cargo design are also presented to highlight further opportunities for peptide-based gene delivery. Modern DNA designs enable prolonged expression compared to traditional plasmids, providing an additional component that can be synergized with peptide carriers for improved transfection. Peptide transfection systems are poised to become a flexible and efficient platform incorporating new chemistries, functionalities, and improved DNA cargos to usher in a new era of gene therapy.

Cell-penetrating peptides in oncologic pharmacotherapy: A review

Cancer is the second leading cause of death in the world and its treatment is extremely challenging, mainly due to its complexity. Cell-Penetrating Peptides (CPPs) are peptides that can transport into the cell a wide variety of biologically active conjugates (or cargoes), and are, therefore, promising in the treatment and in the diagnosis of several types of cancer. Some notable examples are TAT and Penetratin, capable of penetrating the central nervous system (CNS) and, therefore, acting in cancers of this system, such as Glioblastoma Multiforme (GBM). These above-mentioned peptides, conjugated with traditional chemotherapeutic such as Doxorubicin (DOX) and Paclitaxel (PTX), have also been shown to induce apoptosis of breast and liver cancer cells, as well as in lung cancer cells, respectively. In other cancers, such as esophageal cancer, the attachment of Magainin 2 (MG2) to Bombesin (MG2B), another CPP, led to pronounced anticancer effects. Other examples are CopA3, that selectively decreased the viability of gastric cancer cells, and the CPP p28. Furthermore, in preclinical tests, the anti-tumor efficacy of this peptide was evaluated on human breast cancer, prostate cancer, ovarian cancer, and melanoma cells in vitro, leading to high expression of p53 and promoting cell cycle arrest. Despite the numerous in vitro and in vivo studies with promising results, and the increasing number of clinical trials using CPPs, few treatments reach the expected clinical efficacy. Usually, their clinical application is limited by its poor aqueous solubility, immunogenicity issues and dose-limiting toxicity. This review describes the most recent advances and innovations in the use of CPPs in several types of cancer, highlighting their crucial importance for various purposes, from therapeutic to diagnosis. Further clinical trials with these peptides are warranted to examine its effects on various types of cancer.

Self-assembling Peptides in Current Nanomedicine: Versatile Nanomaterials for Drug Delivery

BACKGROUND

The development of modern nanomedicine greatly depends on the involvement of novel materials as drug delivery system. In order to maximize the therapeutic effects of drugs and minimize their side effects, a number of natural or synthetic materials have been widely investigated for drug delivery. Among these materials, biomimetic self-assembling peptides (SAPs) have received more attention in recent years. Considering the rapidly growing number of SAPs designed for drug delivery, a summary of how SAPs-based drug delivery systems were designed, would be beneficial.

METHOD

We outlined research works on different SAPs that have been investigated as carriers for different drugs, focusing on the design of SAPs nanomaterials and how they were used for drug delivery in different strategies.

RESULTS

Based on the principle rules of chemical complementarity and structural compatibility, SAPs such as ionic self-complementary peptide, peptide amphiphile and surfactant-like peptide could be designed. Determined by the features of peptide materials and the drugs to be delivered, different strategies such as hydrogel embedding, hydrophobic interaction, electrostatic interaction, covalent conjugation or the combination of them could be employed to fabricate SAPs-drug complex, which could achieve slow release, targeted or environment-responsive delivery of drugs. Furthermore, some SAPs could also be combined with other types of materials for drug delivery, or even act as drug by themselves.

CONCLUSION

Various types of SAPs have been designed and used for drug delivery following various strategies, suggesting that SAPs as a category of versatile nanomaterials have promising potential in the field of nanomedicine.

Advances in the use of cell penetrating peptides for respiratory drug delivery

Introduction: Respiratory diseases are leading causes of death in the world, still inhalation therapies are the largest fail in drug development. There is an evident need to develop new therapies. Biomolecules represent apotential therapeutic agent in this regard, however their translation to the clinic is hindered by the lack of tools to efficiently deliver molecules. Cell penetrating peptides (CPPs) have arisen as apotential strategy for intracellular delivery that could theoretically enable the translation of new therapies.Areas covered: In this review, the use of CPPs as astrategy to deliver different molecules (cargoes) to treat lung-relateddiseases will be the focus. Abrief description of these molecules and the innovative methods in designing new CPPs is presented. The delivery of different cargoes (proteins, peptides, poorly soluble drugs and nucleic acids) using CPPs is discussed, focusing on benefits to treat different respiratory diseases like inflammatory disorders, cystic fibrosis and lung cancer.Expert opinion: The advantages of using CPPs to deliver biomolecules and poorly soluble drugs to the lungs is evident. This field has advanced in the past few years toward targeted intracellular delivery, although further studies are needed to fully understand its potential and limitations in vitro and in vivo.

Improving Cell Penetration of Gold Nanorods by Using an Amphipathic Arginine Rich Peptide

Introduction

Gold nanorods are highly reactive, have a large surface-to-volume ratio, and can be functionalized with biomolecules. Gold nanorods can absorb infrared electromagnetic radiation, which is subsequently dispersed as local heat. Gold nanoparticles can be used as powerful tools for the diagnosis and therapy of different diseases. To improve the biological barrier permeation of nanoparticles with low cytotoxicity, in this study, we conjugated gold nanorods with cell-penetrating peptides (oligoarginines) and with the amphipathic peptide CLPFFD.

Methods

We studied the interaction of the functionalized gold nanorods with biological membrane models (liposomes) by dynamic light scattering, transmission electron microscopy and the Langmuir balance. Furthermore, we evaluated the effects on cell viability and permeability with an MTS assay and TEM.

Results and Discussion

The interaction study by DLS, the Langmuir balance and cryo-TEM support that GNR-Arg₇CLPFFD enhances the interactions between GNRs and biological membranes. In addition, cells treated with GNR-Arg₇CLPFFD internalized 80% more nanoparticles than cells treated with GNR alone and did not induce cell damage.

Conclusion

Our results indicate that incorporation of an amphipathic sequence into oligoarginines for the functionalization of gold nanorods enhances biological membrane nanoparticle interactions and nanoparticle cell permeability with respect to nanorods functionalized with oligoarginine. Overall, functionalized gold nanorods with amphipathic arginine rich peptides might be candidates for improving drug delivery by facilitating biological barrier permeation.

Cartilage penetrating cationic peptide carriers for applications in drug delivery to avascular negatively charged tissues

Drug delivery to avascular, negatively charged tissues like cartilage remains a challenge. The constant turnover of synovial fluid results in short residence time of administered drugs in the joint space and the dense negatively charged matrix of cartilage hinders their diffusive transport. Drugs are, therefore, unable to reach their cell and matrix targets in sufficient doses, and fail to elicit relevant biological response, which has led to unsuccessful clinical trials. The high negative fixed charge density (FCD) of cartilage, however, can be used to convert cartilage from a barrier to drug entry into a depot by making drugs positively charged. Here we design cartilage penetrating and binding cationic peptide carriers (CPCs) with varying net charge, spatial distribution and hydrophobicity to deliver large-sized therapeutics and investigate their electro-diffusive transport in healthy and arthritic cartilage. We showed that CPC uptake increased with increasing net charge up to +14 but dropped as charge increased further due to stronger binding interactions that hindered CPC penetrability and uptake showing that weak-reversible binding is key to enable their penetration through full tissue thickness. Even after 90% GAG depletion, while CPC +14 uptake reduced by over 50% but still had a significantly high value of 148× showing that intra-tissue long-range charge-based binding is further stabilized by short-range H-bond and hydrophobic interactions. The work presents an approach for rational design of cationic carriers based on tissue FCD and properties of macromolecules to be delivered. These design rules can be extended to drug delivery for other avascular, negatively charged tissues. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) remains an untreatable disease partly due to short joint residence time of drugs and a lack of delivery methods that can effectively target the dense, avascular, highly negatively charged cartilage tissue. In this study, we designed cartilage penetrating and binding cationic peptide carriers (CPCs) that, due to their optimal charge provide adequate electrical driving force to rapidly transport OA drugs into cartilage and reach their cell and matrix targets in therapeutic doses before drugs exit the joint space. This way cartilage is converted from being a barrier to drug entry into a drug depot that can provide sustained drug release for several weeks. This study also investigates synergistic effects of short-range H-bond and hydrophobic interactions in combination with long-range electrostatic interactions on intra-cartilage solute transport. The work provides rules for rational design of cartilage penetrating charge-based carriers depending on the net charge of tissue (normal versus arthritic), macromolecule to be delivered and whether the application is in drug delivery or tissue imaging.

Ionic Nanocomplexes of Hyaluronic Acid and Polyarginine to Form Solid Materials: A Green Methodology to Obtain Sponges with Biomedical Potential

We report on the design, development, characterization, and a preliminary cellular evaluation of a novel solid material. This material is composed of low-molecular-weight hyaluronic acid (LMWHA) and polyarginine (PArg), which generate aqueous ionic nanocomplexes (INC) that are then freeze-dried to create the final product. Different ratios of LMWHA/PArg were selected to elaborate INC, the size and zeta potential of which ranged from 100 to 200 nm and +25 to -43 mV, respectively. Turbidimetry and nanoparticle concentration analyses demonstrated the high capacity of the INC to interact with increasing concentrations of LMWHA, improving the yield of production of the nanostructures. Interestingly, once the selected formulations of INC were freeze-dried, only those comprising a larger excess of LMWHA could form reproducible sponge formulations, as seen with the naked eye. This optical behavior was consistent with the scanning transmission electron microscopy (STEM) images, which showed a tendency of the particles to agglomerate when an excess of LMWHA was present. Mechanical characterization evidenced low stiffness in the materials, attributed to the low density and high porosity. A preliminary cellular evaluation in a fibroblast cell line (RMF-EG) evidenced the concentration range where swollen formulations did not affect cell proliferation (93-464 µM) at 24, 48, or 72 h. Considering that the reproducible sponge formulations were elaborated following inexpensive and non-contaminant methods and comprised bioactive components, we postulate them with potential for biomedical purposes. Additionally, this systematic study provides important information to design reproducible porous solid materials using ionic nanocomplexes.

Improved Intracellular Delivery of Polyarginine Peptides with Cargoes

Complementary to endocytosis, cell-penetrating peptides (CPPs) at high concentrations can penetrate the cell membrane in a direct way, which further makes CPPs popular candidates for delivering therapeutic or diagnostic agents. Although featured as rapid uptake, the translocation efficiency and potential toxicity of the direct penetration are usually affected by cargoes, which is still unclear. Here, using coarse-grained molecular dynamics simulations, we show that the polyarginine (R₈) peptides penetrate the membrane through a water pore in the membrane, and the transmembrane efficiency is improved by conjugating to small nanoparticles (NPs) with proper linkers. It can be attributed to both the extension of the lifetime of the water pore by the NPs and outward diffusion of negative lipids in the asymmetry membrane, which induces the surrounding R₈-NP conjugates to the water pore before it is closed. The translocation efficiency is closely related to the length of the linkers, and it gets the maximum value when the length of the linkers is around half of the membrane thickness. Overlong linkers not only decrease the transmembrane efficiency because of the blockage of NPs in the water pore but may also cause cytotoxicity because of the unclosed water pore. The results provide insights into the internalization of CPPs and facilitate the design of CPP and drug conjugates with high efficiency and low toxicity.

Optimization of the Conditions for Plasmid DNA Delivery and Transfection with Self-Assembled Hyaluronic Acid-Based Nanoparticles

Polymeric systems have been extensively studied as polyelectrolyte complexes to enhance the cellular delivery and transfection efficiency of genetic materials, such as plasmid DNA (pDNA). Here, self-assembled nanoparticles were formulated by complexation of hyaluronic acid (HA)-conjugated poly(ethylene glycol) (HA-PEG) and poly(ethylenimine) (HA-PEI), respectively, with pDNA creating relatively small, stable, and multifunctional nanoparticle complex formulations with high transfection efficiency. This formulation strategy offers high gene expression efficiency and negligible cytotoxicity in HeLa and A549 human lung cancer cell lines. To develop the ideal formulation, in vitro transfection efficiency was studied for three different nanoparticle formulations (HA-PEI/HA-PEG, HA-PEI, and HA-PEG) with different concentrations. The combination of the three polymers (HA, PEG, and PEI) was significant for the formulation to achieve the maximum gene expression results. The nanoparticles were found to be stable for up to a week at 4 °C conditions. Overall, these HA-based nanoparticles showed promising aspects that can be utilized in the designing of gene delivery vectors for cancer therapy.

TRAIL mutant membrane penetrating peptide alike-MuR6-TR enhances the antitumor effects of TRAIL in pancreatic carcinoma both in vitro and in vivo

To remedy the drug resistance of natural tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and enhance its antitumor effects, we prepared a type of TRAIL mutant membrane penetrating peptide alike (TMPPA)‑TRAIL mutant R6 (MuR6-TR) by mutating the N‑terminal of the soluble TRAIL gene sequence. The expressed MuR6‑TR protein was purified to treat pancreatic carcinoma cell lines BxPC‑3 and PANC‑1. The inhibitory effects on the proliferation of BxPC‑3 and PANC‑1 cells was assessed with CCK‑8 assay and compared with natural TRAIL. The antitumor effect of MuR6‑TR was assessed on implant tumors derived from PANC‑1 cells in nude mice and compared with gemcitabine. Finally, the soluble MuR6‑TR gene was successfully mutated with 4 amino acids in the N‑terminal of TRAIL and had a molecular size of 513 bp. The mutant MuR6‑TR was connected to pET32a and verified by enzymatic digestion and sequencing. The recombinant MuR6‑TR was transformed and expressed in Escherichia coli. The CCK‑8 assay results indicated that MuR6‑TR inhibited the growth of BxPC‑3 and PANC‑1 cells in a dose‑dependent manner, with IC50 values of 4.63 and 7.84 ng/ml, respectively, which were much lower than that of natural TRAIL. MuR6‑TR demonstrated a higher inhibitory effect on tumor growth (24.2%) than natural TRAIL (14.4%) and an effect similar to that of gemcitabine at an early period. Thus, the mutant MuR6‑TR exhibited a stronger antitumor effect than that of natural TRAIL both in vivo and in vitro and may have potential therapeutic value for pancreatic carcinoma, which requires further validation.

Surface density of polyarginine influence the size, zeta potential, cellular uptake and tissue distribution of the nanostructured lipid carrier

Poly-arginines are strong tools to elevate the cellular uptake of nanopreparations. To learn the influence of poly-arginine (RRRRRRRR, R8) density on a series of properties of nanostructured lipid carrier (NLC), we build six R8 modified NLCs with different R8 densities (nR-NLC, where n represents the R8 ratio) by fusion–emulsion method with the aid of stearyl-R8. The pharmaceutical characteristics like size, zeta potential and in vitro drug release, cellular uptake, cytotoxicity to A549 cells and tissue distribution in S180 tumor-bearing mice of the six nR-NLCs are all investigated. It turns out that with as little as 2% weight ratio of stearyl-R8 modified on NLC, its pharmaceutical properties, especially zeta potential changes astonishingly; however, the stearyl-R8 ratio should be higher than 4% to upgrade the cellular uptake and cytotoxicity evidently; in the ex vivo tissue distribution assessment, the nR-NLC with less than 8% R8 showed similar tissue accumulation, while NLC with 10% R8 shows obvious acute toxicity to mice. Our study pays attention to the effect of the R8 ratio on the changes of cargo properties, and the results indicate that this topic is essential and worth to be further developed.

Peptide-based strategies for enhanced cell uptake, transcellular transport, and circulation: Mechanisms and challenges

Peptides are emerging as a new tool in drug and gene delivery. Peptide-drug conjugates and peptide-modified drug delivery systems provide new opportunities to avoid macrophage recognition and subsequent phagocytosis, cross endothelial and epithelial barriers, and enter the cytoplasm of target cells. Peptides are relatively small, low-cost, and are stable in a wide range of biological conditions. In this review, we summarize recent work in designing peptides to enhance penetration of biological barriers, increase cell uptake, and avoid the immune system. We highlight recent successes and contradictory results, and outline common emerging concepts and design rules. The development of sequence-structure-function relationships and standard protocols for benchmarking will be a key to progress in the field.

Increased Hydrophobic Block Length of PTDMs Promotes Protein Internalization

The plasma membrane is a major obstacle in the development and use of biomacromolecules for intracellular therapeutic applications. Protein transduction domains (PTDs) have been used to overcome this barrier, but often require covalent conjugation to their cargo and can be time consuming to synthesize. Synthetic monomers can be designed to mimic the amino acid moieties in PTDs, and their resulting polymers provide a well-controlled platform to vary molecular composition for structure-activity relationship studies. In this paper, a series of polyoxanorbornene-based synthetic mimics, inspired by PTDs, with varying cationic and hydrophobic densities, and the nature of the hydrophobic chain and degree of polymerizations were investigated in vitro to determine their ability to non-covalently transport enhanced green fluorescent protein into HeLa cells, Jurkat T cells, and hTERT mesenchymal stem cells. Polymers with high charge density lead to efficient protein delivery. Similarly, the polymers with the highest hydrophobic content and density proved to be the most efficient at internalization. The observed improvements with increased hydrophobic length and content were consistent across all three cell types, suggesting that these architectural relationships are not cell type specific. However, Jurkat T cells showed distinct variation in uptake between polymers than with the other two cell types. These results provide important design parameters for more effective delivery of biomacromolecules for intracellular delivery applications.

Structural behaviour and gene delivery in complexes formed between DNA and arginine-containing peptide amphiphiles

We describe in depth the structure of complexes formed between DNA and two classes of arginine-containing peptide amphiphiles, namely, the lipopeptide PRW-C₁₆ (P = proline, R = arginine, W = tryptophan, C₁₆ = C16 : 0 alkyl chain) and the bolaamphiphile RFL₄FR (R = arginine, F = phenylalanine, L = leucine). A combination of X-ray and neutron scattering provided unprecedented insights into the local structure of these complexes. Lipopeptide-based complexes self-assembled into layered structures with large-scale fractal features, hosting DNA in the interstices. Bola-amphiphile scaffolds were characterized by planar structures with DNA strands presumably sandwiched in-between peptide nanotapes. Importantly, complexation did not affect the structural integrity of DNA in either of the two complexes. The bolaamphiphile conjugates displayed high levels of molecular ordering in contrast to the liquid-crystalline features observed in lipopeptide assemblies. Peptide-DNA complexes were assessed for their potential as a means to deliver the reporter vector pEGFP-N1 into SW480 human colon carcinoma cells. Successfully transfected cells expressed green fluorescent protein. The potentiating effect of PRW-C₁₆ on the cellular uptake of ectopic DNA was found to be much greater than that observed with RFL₄FR. In contrast to the bolaamphiphile-based conjugate, the liquid-crystalline nature of the lipopeptide complex is likely to play a key role in DNA release and transfection efficiency since these weakly bound structures require lower energy expenditure during disassembly and load release.

Targeted gene silencing of CCL2 inhibits triple negative breast cancer progression by blocking cancer stem cell renewal and M2 macrophage recruitment

Triple negative breast cancers are an aggressive subtype of breast cancer, characterized by the lack of estrogen receptor, progesterone receptor and Her2 expression. Triple negative breast cancers are non-responsive to conventional anti-hormonal and Her2 targeted therapies, making it necessary to identify new molecular targets for therapy. The chemokine CCL2 is overexpressed in invasive breast cancers, and regulates breast cancer progression through multiple mechanisms. With few approaches to target CCL2 activity, its value as a therapeutic target is unclear. In these studies, we developed a novel gene silencing approach that involves complexing siRNAs to TAT cell penetrating peptides (Ca-TAT) through non-covalent calcium cross-linking. Ca-TAT/siRNA complexes penetrated 3D collagen cultures of breast cancer cells and inhibited CCL2 expression more effectively than conventional antibody neutralization. Ca-TAT/siRNA complexes targeting CCL2 were delivered to mice bearing MDA-MB-231 breast tumor xenografts. In vivo CCL2 gene silencing inhibited primary tumor growth and metastasis, associated with a reduction in cancer stem cell renewal and recruitment of M2 macrophages. These studies are the first to demonstrate that targeting CCL2 expression in vivo may be a viable therapeutic approach to treating triple negative breast cancer.

Optimisation of vectorisation property: A comparative study for a secondary amphipathic peptide

RNA interference provides a powerful technology for specific gene silencing. Therapeutic applications of small interfering RNA (siRNA) however require efficient vehicles for stable complexation and intracellular delivery. In order to enhance their cell delivery, short amphipathic peptides called cell-penetrating peptides (CPPs) have been intensively developed for the last two decades. In this context, the secondary amphipathic peptide CADY has shown to form stable siRNA complexes and to improve their cellular uptake independent of the endosomal pathway. In the present work, we have described the parameters influencing CADY nanoparticle formation (buffers, excipients, presence of serum, etc.), and have followed in details the CPP:siRNA self-assembly. Once optimal conditions were determined, we have compared the ability of seven different CADY analogues to form siRNA-loaded nanoparticles compared to CADY:siRNA. First of all, we were able to show by biophysical methods that structural polymorphism (α-helix) is an important prerequisite for stable nanoparticle formation independently of occurring sequence mutations. Luciferase assays revealed that siRNA complexed to CADY-K (shorter version) shows better knock-down efficiency on Neuro2a-Luc(+) and B16-F10-Luc(+) cells compared to CADY:siRNA. Altogether, CADY-K is an ideal candidate for further application especially with regards to ex vivo or in vivo applications.