Efficient Cell Penetration Research Articles

Nanoscale Biodegradable Organic-Inorganic Hybrids for Efficient Cell Penetration and Drug Delivery.

We report a comprehensive study on novel, highly efficient, and biodegradable hybrid molecular transporters. To this end, we designed a series of cell-penetrating, cube-octameric silsesquioxanes (COSS), and investigated cellular uptake by confocal microscopy and flow cytometry. A COSS with dense spatial arrangement of guanidinium groups displayed fast uptake kinetics and cell permeation at nanomolar concentrations in living HeLa cells. Efficient uptake was also observed in bacteria, yeasts, and archaea. The COSS-based carrier was significantly more potent than cell-penetrating peptides (CPPs) and displayed low toxicity. It efficiently delivered a covalently attached cytotoxic drug, doxorubicin, to living tumor cells. As the uptake of fluorescently labeled carrier remained in the presence of serum, the system could be considered particularly attractive for the in vivo delivery of therapeutics.

Dual Targeting of Intracellular Pathogenic Bacteria with a Cleavable Conjugate of Kanamycin and an Antibacterial Cell-Penetrating Peptide.

Bacterial infection caused by intracellular pathogens, such as Mycobacterium, Salmonella, and Brucella, is a burgeoning global health epidemic that necessitates urgent action. However, the therapeutic value of a number of antibiotics, including aminoglycosides, against intracellular pathogenic bacteria is compromised due to their inability to traverse eukaryotic membranes. For this significant problem to be addressed, a cleavable conjugate of the antibiotic kanamycin and a nonmembrane lytic, broad-spectrum antimicrobial peptide with efficient mammalian cell penetration, P14LRR, was prepared. This approach allows kanamycin to enter mammalian cells as a conjugate linked via a tether that breaks down in the reducing environment within cells. Potent antimicrobial activity of the P14KanS conjugate was demonstrated in vitro, and this reducible conjugate effectively cleared intracellular pathogenic bacteria within macrophages more potently than that of a conjugate lacking the disulfide moiety. Notably, successful clearance of Mycobacterium tuberculosis within macrophages was observed with the dual antibiotic conjugate, and Salmonella levels were significantly reduced in an in vivo Caenorhabditis elegans model.

Novel Efficient Cell-Penetrating, Peptide-Mediated Strategy for Enhancing Telomerase Inhibitor Oligonucleotides.

At present, there are several therapeutic approaches for targeting telomerase in tumors. One in particular, currently undergoing clinical trials, is based on synthetic lipid-modified oligonucleotide antagonists aimed at inhibiting the ribonucleoprotein subunit of human telomerase. However, while enabling efficient uptake, the lipid modifications reduce the potency of the therapeutic oligonucleotides compared to nonmodified oligonucleotides. Moreover, lipid modification may increase oligonucleotide accumulation in the liver causing undesirable hepatotoxicity. Noncovalent complexation strategies for cell-penetrating peptide (CPP)-mediated delivery present an option to circumvent the need for potency-reducing modifications, while allowing for a highly efficient uptake, and could significantly improve the efficiency of telomerase-targeting cancer therapeutics. Delivery of a nonlipidated locked nucleic acid/2'-O-methyl mixmer significantly inhibits the telomerase activity in treated HeLa cells. The inhibitory effect was further improved through addition of a CPP. Furthermore, calculated IC50-values for the oligonucleotide delivered by CPPs into HeLa cells are more than 20 times lower than telomerase inhibitor Imetelstat, currently undergoing clinical trials. These results emphasize the potential of CPP-mediated delivery of future pharmaceuticals and provide means by which to enhance an already promising therapeutic strategy for cancer treatment.

Selective Inhibition of Osteosarcoma Cell Functions Induced By Curcumin‐Loaded Self‐assembled Arginine‐Rich‐RGD Nanospheres

ObjectivesTo develop a treatment against osteosarcoma with higher selectivity towards osteosarcoma cells and lower cytotoxicity towards normal osteoblast cells.Statement of methodsCurcumin was found to have significant selectivity against osteosarcoma cells in vitro, and the ampiphilic peptide C18GR7RGDS was used as a carrier in aqueous solution. This peptide contains an arginine‐rich and an arginine‐glycine‐aspartic acid (RGD) structure, which may lead to efficient cell penetration and targeting for cancerous cells since RGD sequence can target to the overexpressed ανβ3 integrin. Using a method of co‐dissolution with acetic acid and dialysis tubing, the solubility of curcumin was enhanced and formed a homogeneous solution with the help of amphiphilic nanoparticles (APNPs). The cytotoxicity and cellular uptake of these materials on both osteosarcoma and normal healthy osteoblast cell lines were evaluated by MTT assays and confocal fluorescent microscopyResultsIt was demonstrated for the first time that APNPs formed nanospheres with diameters of 10‐20 nm in water and phosphate buffer saline (PBS), and opened up when the pH value was reduced to 4. The successful encapsulation of curcumin in APNPs was confirmed by Fourier transform infrared (FT‐IR) and X‐ray diffraction (XRD) analysis. The curcumin‐loaded APNPs exhibited a significant selective internalization against the MG‐63 osteosarcoma cell lineimageConclusionsAPNPs can encapsulate hydrophobic curcumin in their hydrophobic cores, and the curcumin‐loaded APNPs could be an innovative candidate for the selective inhibition against osteosarcoma.

Targeting intracellular bacteria with an extended cationic amphiphilic polyproline helix.

An extended cationic and amphiphilic polyproline helix (CAPH) is described with a dual mode of action: effective cell penetration of human macrophages, and potent antimicrobial activity in vitro against both Gram-positive and negative pathogens, including Acinetobacter baumannii, Escherichia coli O157 and Bacillus anthracis. This dual action was successfully combined to clear pathogenic bacteria (Brucella and Salmonella) residing within macrophages.

Cell‐Penetrating, Dimeric α‐Helical Peptides: Nanomolar Inhibitors of HIV‐1 Transcription

AbstractWe constructed dimeric α‐helical peptide bundles based on leucine (L) and lysine (K) residues for both efficient cell penetration and inhibition of the Tat–TAR interaction. The LK dimers can penetrate nearly quantitatively into eukaryotic cells and effectively inhibit the elongation of the TAR transcript at low nanomolar concentrations. The effective inhibition of HIV‐1 replication strongly suggests that the LK dimer has strong potential as an anti‐HIV‐1 drug.

Cell-penetrating, dimeric α-helical peptides: nanomolar inhibitors of HIV-1 transcription.

We constructed dimeric α-helical peptide bundles based on leucine (L) and lysine (K) residues for both efficient cell penetration and inhibition of the Tat-TAR interaction. The LK dimers can penetrate nearly quantitatively into eukaryotic cells and effectively inhibit the elongation of the TAR transcript at low nanomolar concentrations. The effective inhibition of HIV-1 replication strongly suggests that the LK dimer has strong potential as an anti-HIV-1 drug.

Phosphorylation of Maurocalcine Strongly Modifies its Effect on Type 1 Ryanodine Receptor

Maurocalcine (MCa) is a 33-amino acid peptide isolated from the venom of Scorpio maurus palmatus, a Tunisian scorpion. It possesses efficient cell penetration properties and has been shown to strongly modify ryanodine receptor (RyR1) channel behavior by increasing open probability and inducing a long-lasting subconductance state. The amino acid residue threonine at position 26 belongs to a putative phosphorylation site within MCa sequence. We investigated the effect of a) T26 phosphorylation (MCa T26Phospho) by protein kinase A and b) replacement of T26 by glutamic acid residue to mimic phosphorylation on the effect of MCa on RyR1 properties. Using [3H]ryanodine ([3H]Ry) binding and single channel voltage-clamp measurements, we show that both MCa T26Phospho and MCa T26E analogs almost completely lose the ability to induce RyR1 activation. Neither MCa T26Phospho nor MCa T26E (up to 2µM) increase [3H]rya binding. Small increase (∼1.65-fold activation; p<0.01) was observed with high concentrations (10µM) of either MCa T26Phospho or MCa T26E. Single channel measurements revealed that neither MCa T26E nor MCa T26Phospho (up to 2µM) were able to induce the characteristic long-lasting subconductance state of RyR1 observed in presence of wild-type MCa. MCa T26Phospho altered RyR1 channel gating in a time-dependent biphasic manner with initial activation of Po followed by almost complete inactivation. These effects of MCa T26Phospho could be reversed by 200nM wt MCa. At concentrations ≥2μM, MCa T26E enhances Po∼3 fold by shortening τc without altering τo. These results show that single phosphorylation of MCa modifies RyR1 activity.1P01 AR52354.

Exclusive Photothermal Heat Generation by a Gadolinium Bis(naphthalocyanine) Complex and Inclusion into Modified High-Density Lipoprotein Nanocarriers for Therapeutic Applications

A hydrophobic gadolinium bis(naphthalocyanine) sandwich complex (GdSand) possessing several absorbances across visible and infrared wavelengths (up to 2500 nm) was solubilized in aqueous solution by uptake into a nascent mutant high-density lipoprotein (HDL) nanocarrier. The HDL nanocarrier was additionally functionalized with a trans-activator of transcription peptide sequence to promote efficient cell penetration of the drug delivery system (cpHDL). The dye-loaded nanocarrier (GdSand@cpHDL) exhibited photothermal heat generation properties upon irradiation with near-infrared (NIR) laser light, with controllable heat generation abilities as a function of the incident laser light power. Comparison of the photothermal behavior of the dyes GdSand and the well-explored molecular photothermal agent indocyanine green (ICG) in the cpHDL nanocarrier (i.e., ICG@cpHDL) revealed two significant advantages of GdSand@cpHDL: (1) the ability to maintain elevated temperatures upon light absorption for extended periods of time, with a reduced degree of self-destruction of the dye, and (2) exclusive photothermal heat generation with no detectable singlet oxygen production leading to improved integrity of the cpHDL nanocarrier after irradiation. Finally, GdSand@cpHDL was successfully subjected to an in vitro study against NCI-H460 human lung cancer cells, demonstrating the proof-of-principle utility of lanthanide sandwich complexes in photothermal therapeutic applications.

The intracellular mechanism of action on Escherichia coli of BF2-A/C, two analogues of the antimicrobial peptide Buforin 2

In the present study, the antimicrobial peptides BF2-A and BF2-C, two analogues of Buforin 2, were chemically synthesized and the activities were assayed. To elucidate the bactericidal mechanism of BF2-A/C and their different antimicrobial activities, the influence of peptides to E. coli cell membrane and targets of intracellular action were researched. Obviously, BF2-A and BF2-C did not induce the influx of PI into the E. coli cells, indicating nonmemebrane permeabilizing killing action. The FITC-labeled BF2-A/C could penetrate the E. coli cell membrane and BF2-C penetrated the cells more efficiently. Furthermore, BF2-A/C could bind to DNA and RNA respectively, and the affinity of BF2-C to DNA was powerful at least over 4 times than that of BF2-A. The present results implied that BF2-A and BF2-C inhibited the cellular functions by binding to DNA and RNA of cells after penetrating the cell membranes, resulting in the rapid cell death. The structure-activity relationship analysis of BF2-A/C revealed that the cell-penetrating efficiency and the affinity ability to DNA were critical factors for determining the antimicrobial potency of both peptides. The more efficient cell-penetrating and stronger affinity to DNA caused that BF2-C displayed more excellent antimicrobial activity and rapid killing kinetics than BF2-A.

200 Potent inhibition of HIV replication by RNA-binding peptide mimetics with unprecedented specificity

RNA provides an inviting target for pharmaceutical intervention in both infectious and chronic diseases, but it has so far been impossible to identify drug-like molecules with sufficient potency to lead to the successful clinical applications. We have developed a new class of structurally constrained cyclic peptides to target the interaction between the human immunodeficiency virus (HIV-1) transactivator protein Tat and its response element TAR (1,2), which plays an essential role in viral replication. Many previous attempts to inhibit this interaction have failed to yield molecules with sufficient potency and specificity to warrant pharmaceutical development. The peptidic mimics of Tat that are pM inhibitors of the Tat-TAR interaction and discriminate > 1000 fold between closely related RNAs. They are potent inhibitors of viral replication (tens of nM) with no cytotoxicity and efficient cell penetration which specifically inhibit TAR-dependent reverse transcription as well as activation of transcription, and repress replication of a wide variety of viral strains representing all the major HIV clades in primary human lymphocytes (3). The potency and selectivity observed for this family of peptides is unprecedented among Tat inhibitors and suggest that peptides of this class may be more widely useful for the pharmacological inhibition of other protein–RNA interactions.

4(R/S)-Amino/Guanidino-substituted Proline Peptides: Design, Synthesis and DNA Transfection Properties

Collagen is a major structural protein found in the connective tissues of higher organisms and mammals and its biomechanical properties are related to the high thermal stability of its triple helical structure. The primary structure of collagen is composed of the repeating tripeptide motif of Pro-Hyp-Gly, where Hyp is 4 R -hydroxy proline. Cationic collagen mimetics consisting of [Pro(X)-Pro(Y)-Gly](6) where Pro(X) and Pro(Y) are 4(R/S)-amino/guanidine proline have been synthesized and shown to form triplexes more stable than the unmodified collagen peptide [Pro-Hyp-Gly](6). The origin of hyperstability is due to conformational pre-organization of proline pucker arising from the electronegativity of the cationic group. These cationic collagen peptides are shown to be effective cell penetrating and plasmid DNA transfecting agents. The results have potential for design of new collagen mimetics for biomaterial applications and efficient cell penetrating agents for drug delivery applications.

Small Efficient Cell-penetrating Peptides Derived from Scorpion Toxin Maurocalcine

Maurocalcine is the first demonstrated example of an animal toxin peptide with efficient cell penetration properties. Although it is a highly competitive cell-penetrating peptide (CPP), its relatively large size of 33 amino acids and the presence of three internal disulfide bridges may hamper its development for in vitro and in vivo applications. Here, we demonstrate that several efficient CPPs can be derived from maurocalcine by replacing Cys residues by isosteric 2-aminobutyric acid residues and sequence truncation down to peptides of up to 9 residues in length. A surprising finding is that all of the truncated maurocalcine analogues possessed cell penetration properties, indicating that the maurocalcine is a highly specialized CPP. Careful examination of the cell penetration properties of the truncated analogues indicates that several maurocalcine-derived peptides should be of great interest for cell delivery applications where peptide size matters.

D-Maurocalcine, a Pharmacologically Inert Efficient Cell-penetrating Peptide Analogue

Maurocalcine has been the first demonstrated animal toxin acting as a cell-penetrating peptide. Although it possesses competitive advantages, its use as a cell-penetrating peptide (CPP) requires that analogues be developed that lack its characteristic pharmacological activity on ryanodine-sensitive calcium channels without affecting its cell-penetrating and vector efficiencies. Here, we present the synthesis, three-dimensional (1)H NMR structure, and activity of D-maurocalcine. We demonstrate that it possesses all of the desired features for an excellent CPP: preserved structure, lack of pharmacological action, conserved vector properties, and absence of cell toxicity. This is the first report of a folded/oxidized animal toxin in its D-diastereomer conformation for use as a CPP. The protease resistance of this new peptide analogue, combined with its efficient cell penetration at concentrations devoid of cell toxicity, suggests that D-maurocalcine should be an excellent vector for in vivo applications.

Interactions of pyrrolobenzodiazepine dimers and duplex DNA from methicillin-resistant Staphylococcus aureus

Binding of two bactericidal pyrrolobenzodiazepine (PBD) dimers, SJG-136 and ELB-21, to genomic DNA from Staphylococcus aureus EMRSA-16 was investigated. Both agents cross-linked purified EMRSA-16 DNA. The more potent agent, ELB-21, had a greater capacity to cross-link DNA after incubation with intact cells than SJG-136. Extensive interstrand cross-linking at multiple sites on the EMRSA-16 genome was demonstrated by probing EcoRI-restricted DNA with mecA and 16S rDNA. Cross-linking was again greater in DNA extracted from ELB-21-treated cells and was compatible with frequency analysis of preferred binding sequences in EMRSA-16 DNA. These studies support the premise that the potency of ELB-21 is due to efficient cell penetration and provide evidence that the antibacterial activity of PBD dimers results from cross-linking at specific genomic sites.

Design of antisense and triplex-forming oligonucleotides

Antisense oligonucleotides bind to their complementary sequence on messenger RNAs and inhibit translation of the mRNA into the protein. Short oligonucleotides may also be used to inhibit gene transcription via triple-helix formation on a double-stranded DNA gene. These oligonucleotides are called triplex-forming oligonucleotides (TFO). Certain TFOs (also called clamp oligonucleotides) are designed to bind to single-stranded nucleic acids and may inhibit mRNA translation by physical blockade. The numerous applications of triplex-based strategies have been well described. Triplex-forming oligonucleotides and antisense oligonucleotides share the same requirements for cellular applications, such as high binding affinity for their targets, nuclease resistance, and efficient cell penetration. Very similar physicochemical methods are used to study antisense and triplex-forming oligonucleotides in vitro before considering their utilization in cell culture. This chapter focuses on some of the methods employed to determine the critical parameters that help in designing an efficient antisense or triplex-forming oligonucleotide.

Design, synthesis, and biological activities of new thieno[3,2-d] pyrimidines as selective type 4 phosphodiesterase inhibitors.

A common pharmacophore for compounds structurally related to nitraquazone has been derived. Using this pharmacophore, new structures have been designed, synthesized, and evaluated for their inhibitory potencies against cyclic adenosine 5'-monophosphate (cAMP) specific phosphodiesterase (PDE 4). From these compounds, 4-benzylamino-2-butylthieno[3,2-d]pyrimidine (4) was selected for optimization. The effects of changes to the lipophilic groups and the amino linkage on the PDE 4 activity have been investigated. As a result, some potent PDE 4 inhibitors, selective with respect to PDE 3, have been identified. A selected group of compounds have been further evaluated for their ability to displace [3H]rolipram from its binding site and also to potentiate isoprenaline-induced cAMP accumulation in isolated guinea pig eosinophils. Of these, 2-butyl-4-cyclohexylaminothieno[3,2-d]pyrimidine (33) has an interesting profile, with an important improvement in PDE 4/[3H]rolipram ratio with respect to reference drugs, and good activity in cAMP potentiation, consistent with efficient cell penetration.