Constructing bioactive peptides with pH-dependent activities

Computer-Aided Design of Lasso-like Self-Assembling Anticancer Peptides with Multiple Functions for Targeted Self-Delivery and Cancer Treatments

Anticancer peptides are promising drug candidates for cancer treatment, but the short circulation time and low delivery efficiency limit their clinical applications. Herein, we designed several lasso-like self-assembling anticancer peptides (LASAPs) integrated with multiple functions by a computer-aided approach. Among these LASAPs, LASAP1 (CRGDKGPDCGKAFRRFLGALFKALSHLL, 1-9 disulfide bond) was determined to be superior to the others because it can self-assemble into homogeneous nanoparticles and exhibits improved stability in serum. Thus, LASAP1 was chosen for proving the design idea. LASAP1 can self-assemble into nanoparticles displaying iRGD on the surface because of its amphiphilic structure and accumulate to the tumor site after injection because of the EPR effect and iRGD targeting to αVβ3 integrin. The nanoparticles could disassemble in the acidic microenvironment of the solid tumor, and cleaved by the overexpressed hK2, which was secreted by prostate tumor cells, to release the effector peptide PTP-7b (FLGALFKALSHLL), which was further activated by the acidic pH. Therefore, LASAP1 could target the orthotopic prostate tumor in the model mice after intraperitoneal injection and specifically inhibit tumor growth, with low systematic toxicity. Combining the multiple targeting functions, LASAP1 represents a promising design of self-delivery of peptide drugs for targeted cancer treatments.

Legumain/pH dual-responsive lytic peptide-paclitaxel conjugate for synergistic cancer therapy

After molecule targeted drug, monoclonal antibody and antibody–drug conjugates (ADCs), peptide–drug conjugates (PDCs) have become the next generation targeted anti-tumor drugs due to its properties of low molecule weight, efficient cell penetration, low immunogenicity, good pharmacokinetic and large-scale synthesis by solid phase synthesis. Herein, we present a lytic peptide PTP7-drug paclitaxel conjugate assembling nanoparticles (named PPP) that can sequentially respond to dual stimuli in the tumor microenvironment, which was designed for passive tumor-targeted delivery and on-demand release of a tumor lytic peptide (PTP-7) as well as a chemotherapeutic agent of paclitaxel (PTX). To achieve this, tumor lytic peptide PTP-7 was connected with polyethylene glycol by a peptide substrate of legumain to serve as hydrophobic segments of nanoparticles to protect the peptide from enzymatic degradation. After that, PTX was connected to the amino group of the polypeptide side chain through an acid-responsive chemical bond (2-propionic-3-methylmaleic anhydride, CDM). Therefore, the nanoparticle (PPP) collapsed when it encountered the weakly acidic tumor microenvironment where PTX molecules fell off, and further triggered the cleavage of the peptide substrate by legumain that is highly expressed in tumor stroma and tumor cell surface. Moreover, PPP presents improved stability, improved drug solubility, prolonged blood circulation and significant inhibition ability on tumor growth, which gives a reasonable strategy to accurately deliver small molecule drugs and active peptides simultaneously to tumor sites.

Syntheses and Investigations of Conformationally Restricted, Linker-Free α-Amino Acid-BODIPYs via Boron Functionalization

A series of α-amino acid-BODIPY derivatives were synthesized using commercially available N-Boc-l-amino acids, via boron functionalization under mild conditions. The mono-linear, mono-spiro, and di-amino acid-BODIPY derivatives were obtained using an excess of basic (histidine, lysine, and arginine), acidic (aspartic acid), polar (tyrosine, serine), and nonpolar (methionine) amino acid residues, in yields that ranged from 37 to 66%. The conformationally restricted mono-spiro- and di-amino acid-BODIPYs display strong absorptions in the visible spectral region with high molar extinction coefficients and significantly enhanced fluorescence quantum yields compared with the parent BF₂-BODIPY. Cellular uptake and cytotoxicity studies using the human HEp2 cell line show that both the presence of an N,O-bidentate spiro-ring and basic amino acids (His and Arg) increase cytotoxicity and enhance cellular uptake. Among the series of BODIPYs tested, the spiro-Arg- and spiro-His-BODIPYs were found to be the most cytotoxic (IC₅₀ ∼ 22 μM), while the spiro-His-BODIPY was the most efficiently internalized, localizing preferentially in the cell lysosomes, ER, and mitochondria.

Anti-metastatic Effects of Cationic KT2 Peptide (a Lysine/Tryptophan-rich Peptide) on Human Melanoma A375.S2 Cells

BACKGROUND/AIM

KT2 is a lysine/tryptophan-rich peptide modified from Crocodylus siamensis Leucrocin I. In this study, we examined the cell toxicity, cellular uptake, anti-migration and anti-invasion activities of KT2 in A375.S2 human melanoma cells.

MATERIALS AND METHODS

A375.S2 cells were treated with KT2 peptide and then we performed MTT assay, study of cellular uptake by a confocal microscope, wound healing assay, transwell migration/invasion assay, and evaluation of the expression of metastasis-associated proteins.

RESULTS

KT2 can be internalized through the plasma membrane and can slightly alter cell morphology, decrease the percentage of viable cells and inhibit cell migration and invasion of A375.S2 cells in a dose-dependent manner. This peptide suppressed MMP-2 activity, as measured by gelatine zymography assay. The protein level of MMP-2 was decreased by KT2. KT2 also down-regulated metastasis pathway-related molecules, including FAK, RhoA, ROCK1, GRB2, SOS-1, p-JNK, p-c-Jun, PI3K, p-AKT (Thr308), p-AKT (Ser473), p-p38, MMP-9, NF-kB, and uPA.

CONCLUSION

These results indicate that KT2 inhibits the migration and invasion of human melanoma cells by decreasing MMP-2 and MMP-9 expression through inhibition of FAK, uPA, MAPK, PI3K/AKT NF-kB, and RhoA-ROCK signalling pathways. These findings suggest that KT2 deserves further investigation as an anti-metastatic agent for human melanoma.

Physicochemical Features and Peculiarities of Interaction of AMP with the Membrane

Antimicrobial peptides (AMPs) are anti-infectives that have the potential to be used as a novel and untapped class of biotherapeutics. Modes of action of antimicrobial peptides include interaction with the cell envelope (cell wall, outer- and inner-membrane). A comprehensive understanding of the peculiarities of interaction of antimicrobial peptides with the cell envelope is necessary to perform a rational design of new biotherapeutics, against which working out resistance is hard for microbes. In order to enable de novo design with low cost and high throughput, in silico predictive models have to be invoked. To develop an efficient predictive model, a comprehensive understanding of the sequence-to-function relationship is required. This knowledge will allow us to encode amino acid sequences expressively and to adequately choose the accurate AMP classifier. A shared protective layer of microbial cells is the inner, plasmatic membrane. The interaction of AMP with a biological membrane (native and/or artificial) has been comprehensively studied. We provide a review of mechanisms and results of interactions of AMP with the cell membrane, relying on the survey of physicochemical, aggregative, and structural features of AMPs. The potency and mechanism of AMP action are presented in terms of amino acid compositions and distributions of the polar and apolar residues along the chain, that is, in terms of the physicochemical features of peptides such as hydrophobicity, hydrophilicity, and amphiphilicity. The survey of current data highlights topics that should be taken into account to come up with a comprehensive explanation of the mechanisms of action of AMP and to uncover the physicochemical faces of peptides, essential to perform their function. Many different approaches have been used to classify AMPs, including machine learning. The survey of knowledge on sequences, structures, and modes of actions of AMP allows concluding that only possessing comprehensive information on physicochemical features of AMPs enables us to develop accurate classifiers and create effective methods of prediction. Consequently, this knowledge is necessary for the development of design tools for peptide-based antibiotics.

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.

Designing a bioactive scaffold from coassembled collagen–laminin short peptide hydrogels for controlling cell behaviour

Exploring the potential of bifunctional collagen–laminin mimetic peptide based co-assembling gels for cell culture applications.

Hydrophilic Linear Peptide with Histidine and Lysine Residues as a Key Factor Affecting Antifungal Activity

Increases in the numbers of immunocompromised patients and the emergence of drug-resistance fungal pathogens have led to the need for new, safe, efficacious antifungal agents. In this study, we designed a histidine-lysine-lysine (HKK) motif and synthesized six HKK peptides with repetitions of the motif. These peptides showed length-dependent antifungal activity against drug-susceptible and drug-resistant fungal pathogens via membranolytic or non-membranolytic action. None of the peptides were cytotoxic to rat erythrocytes or NIH3T3 mouse embryonic fibroblasts. Short-length peptides were directly translocated in fungal cytosol and reacted with mitochondria, resulting in apoptosis. Membrane-permeabilizing activity occurred in the presence of long peptides, and peptides were able to transfer to the cytosol and induce reactive oxygen species. Our results suggest that peptides composed only of cationic amino acids may be good candidates as antifungal agents.

Peptide oligomers from ultra-short peptides using sortase

Sortase A catalyzed ligation of ultra-short peptides leads to inter/intra-molecular transpeptidation to form either linear or cyclic oligomers dependent upon the peptide length. Cyclic peptides were the main products for peptides with more than 15aa. However, for ultra-short (<15aa) peptides, cyclic oligomers became predominant in prolonged reactions. Peptides with 1-3 aminoglycines were equally active but peptide oligomers from peptide containing more than one aminoglycine were prone to hydrolysis.

Improving tumor chemotherapy effect using an injectable self-healing hydrogel as drug carrier

A self-healing hydrogel has been used as the anti-tumor drug carrier to improve the chemotherapy effect.

Stimuli-responsive polymers for antimicrobial therapy: drug targeting, contact-killing surfaces and competitive release

INTRODUCTION

Polymers can be designed to modify their features as a function of the level and nature of the surrounding microorganisms. Such responsive polymers can endow drug delivery systems and drug-medical device combination products with improved performance against intracellular infections and biofilms.

AREAS COVERED

Knowledge on microorganism growth environment outside and inside cells and formation of biofilm communities on biological and synthetic surfaces, together with advances in materials science and drug delivery are prompting strategies with improved efficacy and safety compared to traditional systemic administration of antimicrobial agents. This review deals with antimicrobial strategies that rely on: (i) polymers that disintegrate or undergo phase-transitions in response to changes in enzymes, pH and pO2 associated to microorganism growth; (ii) stimuli-responsive polymers that expose contact-killing groups when microorganisms try to adhere; and (iii) bioinspired polymers that recognize microorganisms for triggered (competitive/affinity-driven) drug release.

EXPERT OPINION

Prophylaxis and treatment of infections may benefit from polymers that are responsive to the unique changes that microbial growth causes in the surrounding environment or that even recognize the microorganism itself or its quorum sensing signals. These polymers may offer novel tools for the design of macrophage-, bacteria- and/or biofilm-targeted nanocarriers as well as of medical devices with switchable antibiofouling properties.

Dual-functionalized liposomal delivery system for solid tumors based on RGD and a pH-responsive antimicrobial peptide

[D]-H₆L₉, as a pH-responsive anti-microbial peptide (AMP), has been evidenced by us to be an excellent choice in tumor microenvironment-responsive delivery as it could render liposomes responsive to the acidified tumor microenvironment. However, [D]-H₆L₉-modified liposomes could not actively target to tumor area. Therefore, integrin α_vβ₃-targeted peptide RGD was co-modified with [D]-H₆L₉ onto liposomes [(R + D)-Lip] for improved tumor delivery efficiency. Under pH 6.3, (R + D)-Lip could be taken up by C26 cells and C26 tumor spheroids (integrin α_vβ₃-positive) with significantly improved efficiency compared with other groups, which was contributed by both RGD and [D]-H₆L₉, while RGD did not increase the cellular uptake performance on MCF-7 cells (integrin α_vβ₃-negative). Results showed that RGD could decrease cellular uptake of (R + D)-Lip while [D]-H₆L₉ could increase it, implying the role of both RGD and [D]-H₆L₉ in cellular internalization of (R + D)-Lip. On the other hand, (R + D)-Lip could escape the entrapment of lysosomes. PTX-loaded (R + D)-Lip could further increase the cellular toxicity against C26 cells compared with liposomes modified only with RGD and [D]-H₆L₉ respectively, and achieve remarkable tumor inhibition effect on C26 tumor models.

Transformation of oligomers of lipidated peptide induced by change in pH

Oligomerization of lipidated peptides is of general scientific interest and is important in biomedical and pharmaceutical applications. We investigated the solution properties of a lipidated peptide, Liraglutide, which is one of the glucagon-like peptide-1 (GLP-1) agonists used for the treatment of type II diabetes. Liraglutide can serve as a model system for studying biophysical and biochemical properties of micelle-like self-assemblies of the lipidated peptides. Here, we report a transformation induced in Liraglutide oligomers by changing pH in the vicinity of pH 7. This fully reversible transformation is characterized by changes in the size and aggregation number of the oligomer and an associated change in the secondary structure of the constituent peptides. This transformation has quite slow kinetics: the equilibrium is reached in a course of several days. Interestingly, while the transformation is induced by changing pH, its kinetics is essentially independent of the final pH. We interpreted these findings using a model in which desorption of the monomer from the oligomer is the rate-limiting step in the transformation, and we determined the rate constant of the monomer desorption.

Bacteria responsive antibacterial surfaces for indwelling device infections

Indwelling device infections now represent life-threatening circumstances as a result of the biofilms' tolerance to antibiotic treatments. Current antibiotic impregnation approaches through sustained antibiotic release have some unsolved problems which include short life-span, narrowed antibacterial spectrum, ineffectiveness towards resistant mutants, and the potential to hasten the antibiotic resistance process. In this study, bacteria responsive anti-biofilm surfaces were developed using bioactive peptides with proved activity to antibiotic resistant bacteria and biofilms. Resulting surfaces were stable under physiological conditions and in the presence of high concentrations of salts (0.5M NaCl) and biomacromolcules (1.0% DNA and 2.0% alginate), and thus showed good biocompatibility to various tissue cells. However, lytic peptide immobilized surfaces could sense bacteria adhesion and kill attached bacteria effectively and specifically, so biofilms were unable to develop on the lytic peptide immobilized surfaces. Bacteria responsive catheters remained biofilm free for up to a week. Therefore, the bacteria responsive antibacterial surfaces developed in this study represent new opportunities for indwelling device infections.

Simultaneous delivery of therapeutic antagomirs with paclitaxel for the management of metastatic tumors by a pH-responsive anti-microbial peptide-mediated liposomal delivery system

The roles of microRNAs (miRNAs) in the regulation of metastasis have been widely recognized in the recent years. Mir-10b antagomir (antagomir-10b) was shown to impede metastasis through the down-regulation of mir-10b; however, it could not stunt the growth of primary tumors. In this study we showed that the co-delivery of antagomir-10b with paclitaxel (PTX) by a novel liposomal delivery system modified with an anti-microbial peptide [D]-H6L9 (D-Lip) could significantly both hinder the migration of 4T1 cells and induce evident cellular apoptosis and cell death in the meantime. The histidines in the sequence of [D]-H6L9 allowed the peptide to get protonated under pH5.0 (mimicking the lysosome/endosome environment), and strong membrane lytic effect could thus be activated, leading to the escape of liposomes from the lysosomes and the decrease of of mir-10b expression. The in vivo and ex vivo fluorescence imaging showed that D-Lip could reach 4T1 tumors efficaciously. Incorporation of PTX did not influence the antagomir-10b delivery effect of D-Lip; for the in vivo tumor inhibition assay, compared with all the other groups, the combination of antagomir-10b and PTX delivered by D-Lip could prominently delay the growth of 4T1 tumors and reduce the lung metastases at the same time, and the expression of Hoxd10 in tumors was also significantly up-regulated. Taken together, these results demonstrated that D-Lip could act as a sufficient tool in co-delivering antagomir-10b and PTX.

The potential roles of cell surface pHs in bioactive peptide activation

Glycolytic metabolism of cells produces protons that are removed from the cytosol by transport proteins to create a pH difference between the adjacent bulk solution and the cell membrane surface. Therefore, tissue cells have distinct surface pHs because of varied glycocalyx and proton production capability. In this study, we proved the role of cell surface pH in peptide-cell interaction and peptide activation using lytic peptides with pH-dependent activity as probes. Properly, selected peptides could sense the specific pH zones on cells and thus demonstrated varied activity to tissue cells with different surface pHs. For a specific cell, the activity of pH-sensitive peptides changed accordingly as the cell surface pH was tuned up or down by proton channel regulators. Mechanistic studies revealed that cell surface pH directly affected peptide insertion into membranes by altering the secondary structure and aggregation status of membrane-bound pH-sensitive peptides. A pH-sensitive lytic peptide-designed based on the cell surface pH difference between a normal-cancer cell pair showed good selectivity to cancer cells. Therefore, cell surface pHs may present new opportunities to design therapeutic peptides with high cell specificity and selectivity.

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.

Advances in targeted delivery of small interfering RNA using simple bioconjugates

INTRODUCTION

Development of drugs based on RNA interference by small interfering RNA (siRNA) has been progressing slowly due to a number of challenges associated with the in vivo behavior of siRNA. A central problem is controlling siRNA delivery to specific cell types. Here, we review existing literature on one type of strategy for solving the issue of cell-specific delivery of siRNA, namely delivering the siRNA as part of simple bioconjugate constructs.

AREAS COVERED

This review presents current experience from strategies aimed at targeting siRNA to specific cell types, by associating the siRNA with a targeting moiety, in a simple bioconjugate construct. We discuss the use of different types of targeting moieties, as well as the different conjugation strategies employed for preparing these bioconjugate constructs that deliver the siRNA to target cells. We focus especially on the in-built or passive functionalities associated with each strategy, in order to identify key elements of successful siRNA delivery strategies with potential for further exploration.

EXPERT OPINION

By evaluating the current literature on this subject, we identify strategies and concepts that are suitable for future studies, to enable the development of highly efficient simple bioconjugates for targeted siRNA delivery with therapeutic application.

Peptide fibrils with altered stability, activity, and cell selectivity

Peptides have some unique and superior features compared to proteins. However, the use of peptides as therapeutics is hampered by their low stability and cell selectivity. In this study, a new lytic peptide (CL-1, FLGALFRALSRLL) was constructed. Under the physiological condition, peptide CL-1 self-assembled into dynamically stable aggregates with fibrils-like structures. Aggregated CL-1 demonstrated dramatically altered activity and stability in comparison with single molecule CL-1 and other lytic peptides: when incubated with cocultured bacteria and tissue cells, CL-1 aggregates killed bacteria selectively but spared cocultured human cells; CL-1 aggregates were kept intact in human serum for more than five hours. Peptide-cell interaction studies performed on lipid monolayers and live human tissue cells revealed that in comparison with monomeric CL-1, aggregated CL-1 had decreased cell affinity and membrane insertion capability on tissue cells. A dynamic process involving aggregate dissociation and rearrangement seemed to be an essential step for membrane bound CL-1 aggregates to realize its cytotoxicity to tissue cells. Our study suggests that peptide aggregation could be as important as the charge and secondary structure of a peptide in affecting peptide-cell interactions. Controlling peptide self-assembly represents a new way to increase the stability and cell selectivity of bioactive peptides for wide biomedical applications.

Self-assembled poly(ethylene glycol)-co-acrylic acid microgels to inhibit bacterial colonization of synthetic surfaces

We explored the use of self-assembled microgels to inhibit the bacterial colonization of synthetic surfaces both by modulating surface cell adhesiveness at length scales comparable to bacterial dimensions (∼1 μm) and by locally storing/releasing an antimicrobial. Poly(ethylene glycol) [PEG] and poly(ethylene glycol)-co-acrylic acid [PEG-AA] microgels were synthesized by suspension photopolymerization. Consistent with macroscopic gels, a pH dependence of both zeta potential and hydrodynamic diameter was observed in AA-containing microgels but not in pure PEG microgels. The microgels were electrostatically deposited onto poly(l-lysine) (PLL) primed silicon to form submonolayer surface coatings. The microgel surface density could be controlled via the deposition time and the microgel concentration in the parent suspension. In addition to their intrinsic antifouling properties, after deposition, the microgels could be loaded with a cationic antimicrobial peptide (L5) because of favorable electrostatic interactions. Loading was significantly higher in PEG-AA microgels than in pure PEG microgels. The modification of PLL-primed Si by unloaded PEG-AA microgels reduced the short-term (6 h) S. epidermidis surface colonization by a factor of 2, and the degree of inhibition increased when the average spacing between microgels was reduced. Postdeposition L5 peptide loading into microgels further reduced bacterial colonization to the extent that, after 10 h of S. epidermidis culture in tryptic soy broth, the colonization of L5-loaded PEG-AA microgel-modified Si was comparable to the very small level of colonization observed on macroscopic PEG gel controls. The fact that these microgels can be deposited by a nonline-of-sight self-assembly process and hinder bacterial colonization opens the possibility of modifying the surfaces of topographically complex biomedical devices and reduces the rate of biomaterial-associated infection.

Lytic peptides with improved stability and selectivity designed for cancer treatment

Lytic peptides are a group of membrane-acting peptides, which have excellent activity to drug-resistant cells. In this study, the stability and tumor selectivity of newly designed pH-activated lytic peptides were studied. We found that despite varied secondary structures, pH-induced structure changes could not be directly linked to the activity and pH sensitivity of peptides. On the contrary, formation of aggregates had great impacts on peptide binding and insertion into the lipid bilayer of cell membrane. It was found that the pH controlled peptide aggregation and dissolution was responsible for the pH-dependent membrane lysis activity of peptides. One peptide (PTP-7c) formed stable amyloid fibrils, which did not completely dissolve under acidic conditions. As a result, PTP-7c had the lowest membrane lysis and cell killing activities among tested lytic peptides. As solid tumors have consistently low extracellular pHs, peptides with acid-activation features showed improved selectivity to cancer cells. In addition, self-assembled lytic peptides were found to become more stable and showed dramatically increased half lives (up to 11 h) in human plasma. These new lytic peptides with good stability and acid-activated cell lysis activity will have wide biomedical applications especially for the treatment of cancers in which drug resistance has developed.

On the selectivity and efficacy of defense peptides with respect to cancer cells

Here, we review potential determinants of the anticancer efficacy of innate immune peptides (ACPs) for cancer cells. These determinants include membrane-based factors, such as receptors, phosphatidylserine, sialic acid residues, and sulfated glycans, and peptide-based factors, such as residue composition, sequence length, net charge, hydrophobic arc size, hydrophobicity, and amphiphilicity. Each of these factors may contribute to the anticancer action of ACPs, but no single factor(s) makes an overriding contribution to their overall selectivity and toxicity. Differences between the anticancer actions of ACPs seem to relate to different levels of interplay between these peptide and membrane-based factors.

Modified polyethyleneimine with histidine-lysine short peptides as gene carrier

There are several strategies that can be utilized to improve transfection efficiency while reducing the cytotoxicity of polyethyleneimine (PEI) as a promising non-viral gene delivery vector. In this study, we evaluated the potential use of lysine-histidine (KH) peptides in modifying the PEI 10 kDa structure and enhancing its efficiency while maintaining low toxicity of PEI. PEI 10 kDa was modified with 6-bromohexanoic acid (alkyl) to increase its lipophilicity. Then, ethylenediamine (EDA) was attached to the carboxylic groups of PEI-hexanoate to restore the primary amines of PEI. Subsequently, six different KH short peptides were conjugated to PEIs and evaluated for the effect of the KH sequence on vector transfection efficiency and cytotoxicity. The transfection efficiency of PEI-peptides complexed with a luciferase reporter gene (pRLCMV) in Neuro-2A murine neuroblastoma cells showed that the PEI conjugated to KHHHKKHHHK peptide had a significantly higher rate of gene transfection efficiency in comparison with other KH peptides. This peptide was conjugated to PEI-alkyl and PEI-alkyl-EDA and significant improvement in efficiency with minimal cytotoxicity was observed. The results obtained suggest that the sequence and content of KH peptides will have a significant impact on the transfection efficiency of modified PEI 10 kDa.