Guanidinium group: A versatile moiety inducing transport and multicompartmentalization in complementary membranes

Cell-penetrating peptides for transmucosal delivery of proteins

Enabling non-invasive delivery of proteins across the mucosal barriers promises improved patient compliance and therapeutic efficacies. Cell-penetrating peptides (CPPs) are emerging as a promising and versatile tool to enhance protein and peptide permeation across various mucosal barriers. This review examines the structural and physicochemical attributes of the nasal, buccal, sublingual, and oral mucosa that hamper macromolecular delivery. Recent development of CPPs for overcoming those mucosal barriers for protein delivery is summarized and analyzed. Perspectives regarding current challenges and future research directions towards improving non-invasive transmucosal delivery of macromolecules for ultimate clinical translation are discussed.

Modular Diazo Compound for the Bioreversible Late-Stage Modification of Proteins

We introduce a versatile strategy for the bioreversible modification of proteins. Our strategy is based on a tricomponent molecule, synthesized in three steps, that incorporates a diazo moiety for chemoselective esterification of carboxyl groups, a pyridyl disulfide group for late-stage functionalization with thiolated ligands, and a self-immolative carbonate group for esterase-mediated cleavage. Using cytochrome c (Cyt c) and the green fluorescent protein (GFP) as models, we generated protein conjugates modified with diverse domains for cellular delivery that include a small molecule, targeting and cell-penetrating peptides (CPPs), and a large polysaccharide. As a proof of concept, we used our strategy to effect the delivery of proteins into the cytosol of live mammalian cells in the presence of serum. The cellular delivery of functional Cyt c, which induces apoptosis, highlighted the advantage of bioreversible conjugation on a carboxyl group versus irreversible conjugation on an amino group. The ease and utility of this traceless modification provide new opportunities for chemical biologists.

Guanidinium-Rich Lipopeptide-Based Nanoparticle Enables Efficient Gene Editing in Skeletal Muscles

Genome editing mediated by the CRISPR-Cas system holds great promise for the treatment of genetic diseases. However, safe and efficient in vivo delivery of CRISPR genome editing machinery remains a challenge. Here, we report a lipopeptide-based nanoparticle (LNP) that can efficiently deliver the CRISPR Cas9/sgRNA ribonucleoprotein (RNP) and enable efficient genome editing both in vitro and in vivo. An artificial lipopeptide, GD-LP, was constructed by linking a hydrophilic guanidinium-rich head to an oleic acid-based hydrophobic tail via a disulfide bond. LNP formed by the self-assembly of GD-LP can easily form a complex with RNP with a loading content of up to 20 wt %. The resulting RNP-LNP nanocomplex led to 72.6% gene editing efficiency in GFP-HEK cells with negligible cytotoxicity. The LNP also showed significantly higher transfection efficiencies than Lipofectamine 2000 for the delivery of mRNA in NIH 3T3 and RAW 264.7 and the delivery of plasmid DNA in B78 cells. In vivo studies showed that intramuscular injection of the RNP-LNP nanocomplex in Ai14 mice induced efficient gene editing in muscular tissues. Moreover, the delivery of Cas9 RNP and donor DNA by LNP (i.e., RNP/ssODN-LNP nanocomplex) restored dystrophin expression, reduced skeletal muscle fibrosis, and significantly improved muscle strength in a Duchenne muscular dystrophy (DMD) mouse model.

G-quadruplex-mediated specific recognition, stabilization and transcriptional repression of bcl-2 by small molecule

The presence of the G-quadruplex (G4) structure in the promoter region of the human bcl-2 oncogenes makes it a promising target for developing anti-cancer therapeutics. Bcl-2 inhibits apoptosis, and its frequent overexpression in cancer cells contributes to tumor initiation, progression, and resistance to therapy. Small molecules that can specifically bind to bcl-2 G4 with high affinity and selectivity are remaining elusive. Here, we report that small molecule 1,3-bis-) furane-2yl-methylidene-amino) guanidine (BiGh) binds to bcl-2 G4 DNA structure with very high affinity and selectivity over other genomic G4 DNA structures and duplex DNA. BiGh stabilizes folded parallel conformation of bcl-2 G4 via non-covalent and electrostatic interactions and increases the thermal stabilization up to 15 °C. The ligand significantly suppresses the bcl-2 transcription in HeLa cells by a G4-dependent mechanism and induces cell cycle arrest which promotes apoptosis. The in silico ADME profiling confirms the potential 'drug-likeness' of BiGh. Our results showed that BiGh stabilizes the bcl-2 G-quadruplex motif, downregulates the bcl-2 gene transcription as well as translation process in cervical cancer cells, and exhibits potential anti-cancer activity. This work provides a potential platform for the development of lead compound(s) as G4 stabilizers with drug-like properties of BiGh for cancer therapeutics.

Design, Synthesis, and Antiproliferative Activity of Novel Neocryptolepine-Rhodanine Hybrids

A series of novel neocryptolepine-rhodanine hybrids (9a,b, 11a-d, 14, and 16a,b) have been synthesized by combining neocryptolepine core 5 modified at the C-11 position with rhodanine condensed with the appropriate aryl/hetero aryl aldehydes. Based on these findings, the structures of the hybrids were confirmed by spectral analyses. By employing the MTT assay, all hybrids were tested for their in vitro antiproliferative activity against two cancer cell lines, including MDA-MB-231 (human breast) and HepG-2 (hepatocellular carcinoma). Interestingly, the IC50 values of all hybrids except 9b and 11c showed activity comparable to the standard anticancer drug, 5-fluorouracil, against HepG-2 cancer cells. Furthermore, the cytotoxicity of all the synthesized hybrids was investigated on a normal skin human cell line (BJ-1), and the results showed that these compounds had no significant cytotoxicity toward these healthy cells at the highest concentration used in this study. This study also indicated that the active hybrids exert their cytotoxic activity via the induction of apoptosis. A molecular docking study was used to shed light on the molecular mechanism of their anticancer activity. The docking results revealed that the hybrids exert their mode of action through DNA intercalation. Furthermore, in silico assessment for pharmacokinetic properties was performed on the most potent compounds, which revealed candidates with good bioavailability, high tolerability with cell membranes, and positive drug-likeness values.

Discovery of potent Guanidine derivative that selectively binds and stabilizes the human BCL-2 G-quadruplex DNA and downregulates the transcription

Small molecules that interact with quadruplexes offer a wide range of potential applications, including not just as medications but also as sensors for quadruplexes structures. The BCL-2 is a proto-oncogene that often gets mutated in lethal cancer and could be an interesting target for developing an anti-cancer drug. In the present study, we have employed various biophysical techniques such as fluorescence, CD, Isothermal calorimeter, gel retardation, and PCR stop assay, indicating that Guanidine derivatives GD-1 and GD-2 selectively interact with high affinity with BCL-2 G-quadruplex over other G-quadruplex DNA and duplex DNA. The most promising small molecule GD-1 increases the thermostability of the BCL-2 GQ structure by 12°C. Our biological experiments such as ROS generation, qRT-PCR, western blot, TFP based Reporter assay, show that the GD-1 ligand causes a synthetic lethal interaction by suppressing the expression BCL-2 genes via interaction and stabilization of its the promoter G-quadruplexes in HeLa cells and act as a potential anti-cancer agent.

Multistage Systemic and Cytosolic Protein Delivery for Effective Cancer Treatment

Current clinical applications of protein therapy are largely limited to systemically accessible targets in vascular or extracellular areas. Major obstacles to the widespread application of protein therapeutics in cancer treatment include low membrane permeability and endosomal entrapment. Herein, we report a multistage nanoparticle (NP) strategy for systemic and cytosolic protein delivery to tumor cells, by encapsulating a protein conjugate, tetra-guanidinium (TG)-modified saporin, into tumor microenvironment (TME) pH-responsive polymeric NPs. Upon reaching the tumor site after systemic circulation, the polymeric NPs respond rapidly to the acidic tumor microenvironment and release the TG-saporin conjugates, which penetrate the tumor tissue and enter into tumor cells via TG-mediated cytosolic transportation. The TG-saproin NPs showed potent inhibition of lung cancer cell growth in vitro and in vivo. We expect that this multistage NP delivery strategy with long blood circulation, deep tumor penetration, and efficient cytosolic transport may be applicable to various therapeutic proteins for effective cancer treatment.

Polyphosphate in Antiviral Protection: A Polyanionic Inorganic Polymer in the Fight Against Coronavirus SARS-CoV-2 Infection

Polyanions as polymers carrying multiple negative charges have been extensively studied with regard to their potential antiviral activity. Most studies to date focused on organic polyanionic polymers, both natural and synthetic. The inorganic polymer, polyphosphate (polyP), despite the ubiquitous presence of this molecule from bacteria to man, has attracted much less attention. More recently, and accelerated by the search for potential antiviral agents in the fight against the pandemic caused by the coronavirus SARS-CoV-2, it turned out that polyP disrupts the first step of the viral replication cycle, the interaction of the proteins in the virus envelope and in the cell membrane that are involved in the docking process of the virus with the target host cell. Experiments on a molecular level using the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein and the cellular angiotensin converting enzyme 2 (ACE2) receptor revealed that polyP strongly inhibits the binding reaction through an electrostatic interaction between the negatively charged centers of the polyP molecule and a cationic groove, which is formed by positively charged amino acids on the RBD surface. In addition, it was found that polyP, due to its morphogenetic and energy delivering activities, enhances the antiviral host innate immunity defense of the respiratory epithelium. The underlying mechanisms and envisaged application of polyP in the therapy and prevention of COVID-19 are discussed.

Nanoparticles for vaccine and gene therapy: Overcoming the barriers to nucleic acid delivery

Nucleic acid therapeutics can be used to control virtually every aspect of cell behavior and therefore have significant potential to treat genetic disorders, infectious diseases, and cancer. However, while clinically approved to treat a small number of diseases, the full potential of nucleic acid therapeutics is hampered by inefficient delivery. Nucleic acids are large, highly charged biomolecules that are sensitive to degradation and so the approaches to deliver these molecules differ significantly from traditional small molecule drugs. Current studies suggest less than 1% of the injected nucleic acid dose is delivered to the target cell in an active form. This inefficient delivery increases costs and limits their use to applications where a small amount of nucleic acid is sufficient. In this review, we focus on two of the major barriers to efficient nucleic acid delivery: (1) delivery to the target cell and (2) transport to the subcellular compartment where the nucleic acids are therapeutically active. We explore how nanoparticles can be modified with targeting ligands to increase accumulation in specific cells, and how the composition of the nanoparticle can be engineered to manipulate or disrupt cellular membranes and facilitate delivery to the optimal subcellular compartments. Finally, we highlight how with intelligent material design, nanoparticle delivery systems have been developed to deliver nucleic acids that silence aberrant genes, correct genetic mutations, and act as both therapeutic and prophylactic vaccines. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Biology-Inspired Nanomaterials > Lipid-Based Structures.

A supramolecular double-helix based on complementary phosphate-guanidinium pairing

A double-helical supramolecular structure was formed by self-assembly of 1,1'-binaphthyl-based bisguanidines and bisphosphoric acids. Interestingly the homochiral (S,S) + (S,S)-pair forms a left-handed double-helix, while the heterochiral (S,S) + (R,R)-pair forms a non-helical dimer.

Specific and nondisruptive interaction of guanidium-functionalized gold nanoparticles with neutral phospholipid bilayers

Understanding and controlling the interaction between nanoparticles and biological entities is fundamental to the development of nanomedicine applications. In particular, the possibility to realize nanoparticles capable of directly targeting neutral lipid membranes would be advantageous to numerous applications aiming at delivering nanoparticles and their cargos into cells and biological vesicles. Here, we use experimental and computational methodologies to analyze the interaction between liposomes and gold nanoparticles (AuNPs) featuring cationic headgroups in their protecting monolayer. We find that in contrast to nanoparticles decorated with other positively charged headgroups, guanidinium-coated AuNPs can bind to neutral phosphatidylcholine liposomes, inducing nondisruptive membrane permeabilization. Atomistic molecular simulations reveal that this ability is due to the multivalent H-bonding interaction between the phosphate residues of the liposome's phospholipids and the guanidinium groups. Our results demonstrate that the peculiar properties of arginine magic, an effect responsible for the membranotropic properties of some naturally occurring peptides, are also displayed by guanidinium-bearing functionalized AuNPs.

Multi-Walled Carbon Nanotubes Decorated with Guanidinylated Dendritic Molecular Transporters: An Efficient Platform for the Selective Anticancer Activity of Doxorubicin

An efficient doxorubicin (DOX) drug delivery system with specificity against tumor cells was developed, based on multi-walled carbon nanotubes (MWCNTs) functionalized with guanidinylated dendritic molecular transporters. Acid-treated MWCNTs (oxCNTs) interacted both electrostatically and through hydrogen bonding and van der Waals attraction forces with guanidinylated derivatives of 5000 and 25,000 Da molecular weight hyperbranched polyethyleneimine (GPEI5K and GPEI25K). Chemical characterization of these GPEI-functionalized oxCNTs revealed successful decoration with GPEIs all over the oxCNTs sidewalls, which, due to the presence of guanidinium groups, gave them aqueous compatibility and, thus, exceptional colloidal stability. These GPEI-functionalized CNTs were subsequently loaded with DOX for selective anticancer activity, yielding systems of high DOX loading, up to 99.5% encapsulation efficiency, while the DOX-loaded systems exhibited pH-triggered release and higher therapeutic efficacy compared to that of free DOX. Most importantly, the oxCNTs@GPEI5K-DOX system caused high and selective toxicity against cancer cells in a non-apoptotic, fast and catastrophic manner that cancer cells cannot recover from. Therefore, the oxCNTs@GPEI5K nanocarrier was found to be a potent and efficient nanoscale DOX delivery system, exhibiting high selectivity against cancerous cells, thus constituting a promising candidate for cancer therapy.

Spontaneous vesicle formation and vesicle-to-α-gel transition in aqueous mixtures of sodium monododecylphosphate and guanidinium salts

Monoalkyl phosphates (MAPs) are one kind of important single-chain weak acid/salt type surfactants, but the understanding of their aggregation behavior in water is very limited due to their insolubility at room temperature. In the current work, the effect of guanidinium salts (GuSalts) on the solubility of sodium monododecylphosphate (SDP), a typical MAP, in water was determined at 25.0 °C, and the aggregation behavior of SDP in the GuSalt/water mixtures was investigated. The solubility of SDP is significantly improved by GuSalts including GuCl, GuSO4, GuSO3, GuPO4, and GuCO3 at 25.0 °C, resulting in an isotropic phase. SDP vesicles are spontaneously formed in the isotropic phase, with a critical vesicle concentration of ∼1.0 mM independent of the type of GuSalts. A "bridging dimer" mechanism is proposed to explain the formation of SDP vesicles. The SDP vesicles have a unilamellar structure with a size of ∼80 nm and an alkyl interdigitated degree of ∼25%, and exhibit size-selective permeability. Interestingly, a temperature-induced reversible transition between vesicles and α-gels was observed for the SDP/GuSalt/H2O systems when the SDP content is higher than 20 mM. The α-gels obtained are composed of vesicles and bilayer sheets, showing similar viscoelasticity to conventional gels, although their water content is as high as ∼98 wt%. The microviscosity of SDP vesicle membranes (ca. 35.79-49.34 mPa s at 25.0 °C) and the transition temperature between vesicles and α-gels (ca. 21.0-22.8 °C) are all dependent of the type of GuSalts. This work deepens the understanding of the aggregation behavior of MAPs and also provides valuable information for their practical applications.

Nonviral gene delivery using PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from human papillomavirus type 11 E2 protein

Polyamidoamine (PAMAM) dendrimers are biocompatible polymers utilized in multiple biomedical applications including tissue engineering, medical diagnosis, drug and gene delivery systems, and biosensors. Normally, high-generation PAMAM dendrimers are advantageous for use in gene therapy research because they have a relatively high transfection efficiency. A high-generation PAMAM dendrimer has a high charge density, which induces greater damage to the membranous organelles than that induced by a low-generation PAMAM dendrimer. In this study, we added NLS sequences derived from the human papillomavirus (HPV) type 11 E2 protein to the low-generation PAMAM generation 2 (PAMAM G2) dendrimer and simultaneously introduced histidine residues to reduce cytotoxicity. RKRARH-PAMAM G2 showed similar and high transfection efficiencies in Neuro-2A and NIH3T3 cell lines and relatively low cytotoxicities relative to that of polyethylenimine 25 kDa (PEI 25 kDa).

Stable polymer bilayers for protein channel recordings at high guanidinium chloride concentrations

The use of chaotropic reagents is common in biophysical characterization of biomolecules. When the study involves transmembrane protein channels, the stability of the protein channel and supporting bilayer membrane must be considered. In this letter, we show that planar bilayers composed of poly(1,2-butadiene)-b-poly(ethylene oxide) diblock copolymer are stable and leak-free at high guanidinium chloride concentrations, in contrast to diphytanoyl phosphatidylcholine bilayers, which exhibit deleterious leakage under similar conditions. Furthermore, insertion and functional analysis of channels such as α-hemolysin and MspA are straightforward in these polymer membranes. Finally, we demonstrate that α-hemolysin channels maintain their structural integrity at 2 M guanidinium chloride concentrations using blunt DNA hairpins as molecular reporters.

Enhanced transfection efficiency of low generation PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from herpesviridae

Polyamidoamine (PAMAM) dendrimer is an extensively studied polymer in the biomedical research because of its low polydispersity, distinct molecular structure, and surface functionalities. Generally, a high-generational PAMAM dendrimer is used for gene delivery because transfection efficiency is dependent on charge density; however, an increase in charge density induces disruption of the cellular membrane, and damage to the membrane results in cytotoxicity. In this study, we selected PAMAM generation 2 to reduce the cytotoxic effect and conjugated RRILH and RRLHL sequences, nuclear localization signals (NLS) derived from herpesviridae to PAMAM generation 2. The transfection efficiency of RRILH-PAMAM G2 and RRLHL-PAMAM G2 was similar to that of polyethylenimine (PEI) in Neuro2A, HT22, and HaCaT cells, whereas their transfection efficiency was much higher than that of PEI in NIH3T3 cells. RRILH-PAMAM G2 showed relatively lower cytotoxicity than did RRLHL-PAMAM G2 in all cell lines, but the transfection capacity of the two polymers was similar. Our study shows that low-generational PAMAM dendrimer conjugated with NLS sequences has potential as an alternative to PEI in gene delivery.

Metabolomics reveals differential mechanisms of toxicity of hyperbranched poly(ethyleneimine)-derived nanoparticles to the soil-borne fungus Verticillium dahliae Kleb

There is a consensus on the urge for the discovery and assessment of alternative, improved sources of bioactivity that could be developed as plant protection products (PPPs), in order to combat issues that the agrochemical sector is facing. Based on the recent advances in nanotechnology, nanoparticles seem to have a great potential towards the development of the next generation nano-PPPs used as active ingredients (a.i.) per se or as nanocarriers in their formulation. Nonetheless, information on their mode(s)-of-action (MoA) and mechanisms of toxicity is yet largely unknown, representing a bottleneck in their further assessment and development. Therefore, we have undertaken the task to assess the fungitoxicity of hyperbranched poly(ethyleneimine) (HPEI), quaternized hyperbranched poly(ethyleneimine) (QPEI), and guanidinylated hyperbranched poly(ethyleneimine) (GPEI) nanoparticles to the soil-born plant pathogenic fungus Verticillium dahliae Kleb, and dissect their effects on its metabolism applying GC/EI/MS metabolomics. Results revealed that functionalization of HPEI nanoparticles with guanidinium end groups (GPEI) increases their toxicity to V. dahliae, while functionalization with quaternary ammonium end groups (QPEI) decreases it. The treatments with the nanoparticles affected the chemical homeostasis of the fungus, altering substantially its amino acid pool, energy production, and fatty acid content, causing additionally oxidative and osmotic stresses. To the best of our knowledge, this is the first report on the comparative toxicity of HPEI, QPEI, and GPEI to filamentous fungi applying metabolomics. The findings could be exploited in the study of the quantitative structure-activity relationship (QSAR) of HPEI-derived nanoparticles and their further development as nano-PPPs.

Tuning of endosomal escape and gene expression by functional groups, molecular weight and transfection medium: a structure-activity relationship study

The use of genetic material by non-viral transfer systems is still in its initial stages, but there are high expectations for the development of targeted therapies. However, nucleic acids cannot enter cells without help, they must be well protected to prevent degradation and overcome a variety of biological barriers, the endosomal barrier being one of the greatest cellular challenges. Herein, the structure-property-relationship was investigated in detail, using well-defined polymers. Polyacrylamides were synthesized via RAFT polymerization resulting in a polymer library of (i) different cationic groups as aminoethyl acrylamide (AEAm), dimethylaminoethyl acrylamide (DMAEAm), dimethylaminopropyl acrylamide (DMAPAm) and guanidinopropyl acrylamide (GPAm); (ii) different degree of polymerization; and investigated (iii) in different cell culture settings. The influence of molar mass and cationic moiety on complex formation with pDNA, cytotoxicity and transfection efficiency of the polymers were investigated. The systematic approach identified a pH-independent guanidinium-containing homopolymer (PGPAm₈₉) as the polymer with the highest transfection efficiency and superior endosomal release under optimal conditions. Since PGPAm₈₉ is not further protonated inside endosomes, common escape theories appear unsuitable. Therefore, the interaction with bis(monoacryloylglycerol)phosphate, a lipid specific for endosomal vesicles, was investigated. Our research suggests that the interactions between amines and lipids may be more relevant than anticipated.

From Interaction to Function in DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly represents a rich and growing subset of supramolecular chemistry where functional self-assemblies are programmed in a versatile manner using nucleic acids as readily-available and readily-tunable templates. In this review, we summarize the different DNA recognition modes and the basic supramolecular interactions at play in this context. We discuss the recent results that report the DNA-templated self-assembly of small molecules into complex yet precise nanoarrays, going from 1D to 3D architectures. Finally, we show their emerging functions as photonic/electronic nanowires, sensors, gene delivery vectors, and supramolecular catalysts, and their growing applications in a wide range of area from materials to biological sciences.

Apatite-binding nanoparticulate agonist of hedgehog signaling for bone repair

The hedgehog signaling pathway plays a critical role in bone development and regeneration. Applications of hedgehog morphogens or small molecular agonists are of interest in bone repair but constrained by low stability, high dose requirement, and nonspecific targeting in vivo. Herein, a nanoparticulate agonist as a new type of hedgehog signaling activator is developed for efficacious bone healing. The shell of nanoparticulate agonist consists of palmitic acid and oxysterol, which could modify hedgehog function and bind with the smoothened receptor to positively modulate hedgehog signaling. Meanwhile, the core is assembled with sonic hedgehog gene/polyethyleneimine complex, which could synergistically enhance hedgehog signaling with oxysterol constituents. Moreover, alendronate is introduced into nanoparticulate agonist to bind with hydroxyapatite for potential bone tissue targeting. Lastly, the nanoparticulate agonist surface is decorated with the guanidine group to overcome cell membrane barriers. The created multifunctional nanoparticulate agonist is successfully integrated onto apatite-coated three-dimensional scaffolds and demonstrates greatly improved osteogenesis in vitro and calvarial bone healing. This work suggests a novel biomaterial design to specifically promote hedgehog signaling for the treatment of bone defects.

Development of effective anti-influenza drugs: congeners and conjugates - a review

Influenza is a long-standing health problem. For treatment of seasonal flu and possible pandemic infections, there is a need to develop new anti-influenza drugs that have good bioavailability against a broad spectrum of influenza viruses, including the resistant strains. Relenza™ (zanamivir), Tamiflu™ (the phosphate salt of oseltamivir), Inavir™ (laninamivir octanoate) and Rapivab™ (peramivir) are four anti-influenza drugs targeting the viral neuraminidases (NAs). However, some problems of these drugs should be resolved, such as oral availability, drug resistance and the induced cytokine storm. Two possible strategies have been applied to tackle these problems by devising congeners and conjugates. In this review, congeners are the related compounds having comparable chemical structures and biological functions, whereas conjugate refers to a compound having two bioactive entities joined by a covalent bond. The rational design of NA inhibitors is based on the mechanism of the enzymatic hydrolysis of the sialic acid (Neu5Ac)-terminated glycoprotein. To improve binding affinity and lipophilicity of the existing NA inhibitors, several methods are utilized, including conversion of carboxylic acid to ester prodrug, conversion of guanidine to acylguanidine, substitution of carboxylic acid with bioisostere, and modification of glycerol side chain. Alternatively, conjugating NA inhibitors with other therapeutic entity provides a synergistic anti-influenza activity; for example, to kill the existing viruses and suppress the cytokines caused by cross-species infection.

Identification and elucidation of proline-rich antimicrobial peptides with enhanced potency and delivery

Proline-rich antimicrobial peptides (PrAMPs) kill bacteria via a nonlytic mechanism in which they permeate through the outer membrane, utilize protein-mediated transport across the inner membrane, and target the ribosome to inhibit protein synthesis. We previously reported that substitutions of oncocin ( VDKPPYLPRPRPPRRIYNR - NH 2 ) with a pair of cationic residues improved the antimicrobial activity. In this study, we applied the design protocol to three other PrAMPs: apidaecin-1b, pyrrhocoricin, and bactenecin 7(1-16) and found that the substitutions (R4K and I8K/R) for apidaecin-1b improve the activity by twofold (p < .05) against nonpathogenic Escherichia coli. Moreover, the substitutions (L7K/R and R14K) for pyrrhocoricin improve the activity by 2-10-fold (p < .05) against some strains of E. coli and Salmonella Typhimurium. We also performed activity tests against inner membrane protein (SbmA or YgdD) knockout strains. The result is consistent with previous studies that SbmA is the major transporter for apidaecin-1b and pyrrhocoricin derivatives. However, bactenecin 7(1-16) functions independently of these transporters. In addition, several apidaecin-1b derivatives exhibit enhanced activity relative to wild-type only in the absence of SbmA, which is consistent with mutations that enhance transport across the inner membrane. A high performance liquid chromatography-based kinetic assay for cellular association and internalization demonstrates that the selected cationic mutations can improve cellular association in minimal media, but this enhanced association is not required for increased activity, which suggests the importance of inner membrane transport. These functional studies on cationic mutants of PrAMPs advance understanding of potency and mechanism and advance the ability to engineer improved antimicrobials as evidenced by the identification of the pyrrhocoricin mutant (L7R and R14K) with 10-fold elevated potency against pathogenic E. coli.

Guanidine-based disinfectants, polyhexamethylene guanidine-phosphate (PHMG-P), polyhexamethylene biguanide (PHMB), and oligo(2-(2-ethoxy)ethoxyethyl guanidinium chloride (PGH) induced epithelial-mesenchymal transition in A549 alveolar epithelial cells

Abstracts Objective: The major active ingredient of humidifier disinfectant, polyhexamethylene guanidine-phosphate (PHMG-P), caused hundreds of deaths with pulmonary fibrosis. However, structurally similar guanidine-based disinfectants are still in use in various fields. Moreover, as they are precursors of excellent antimicrobial compounds, new chemicals with guanidine-based structures have been synthesized and introduced. In this study, we evaluated pulmonary fibrotic responses induced by PHMG-P, polyhexamethylene biguanide (PHMB), and oligo(2-(2-ethoxy)ethoxyethyl guanidinium chloride (PGH) and their toxicity mechanisms in type II alveolar epithelial A549 cells. Materials and methods: Cellular damage was compared by using the cytotoxicity test (WST-1 assay) and plasma membrane toxicity tests (Lactate dehydrogenase leakage detection assay and plasma membrane staining). As a measure of fibrotic response, induction of the epithelial-mesenchymal transition (EMT) was evaluated by measuring E-cadherin and α-smooth muscle actin (α-SMA) protein expression (epithelial and mesenchymal marker, respectively). Results: All tested compounds showed membrane damage; PHMG-P and PGH induced the highest and lowest damage, respectively. Moreover, they induced EMT when the test chemicals were treated with similar cytotoxic concentrations. Conclusions: Our study indicates that three guanidine-based disinfectants are potential fibrosis-inducing chemicals that induce EMT through cellular damage. Therefore, use of guanidine-based polymers should be strictly regulated by considering their potential adverse effects on the lungs.

Interactions of Casein and Polypeptides in Multilayer Films Studied by FTIR and Molecular Dynamics

Multilayer films containing α- and β-casein and polypeptides, poly-L-lysine (PLL), and poly-L-arginine (PLArg) were formed by the layer-by-layer technique and Fourier Transform InfraRed spectroscopy with Attenuated Total Reflection (FTIR-ATR) and FTIR/Grazing Angle analyzed their infrared spectra. We investigated the changes of conformations of casein and polypeptides in the complexes formed during the build-up of the films. To elucidate the differences in the mechanism of complex formation leading to various growths of (PLL/casein)_n and (PLArg/casein)_n films, we performed the molecular dynamics simulations of the systems consisting of short PLL and PLArg chains and the representative peptide chains—casein fragments, which consists of several aminoacid sequences. The results of the simulation indicated the preferential formation of hydrogen bonds of poly-L-arginine with phosphoserine and glutamic acid residues of caseins. FTIR spectra confirmed those, which revealed greater conformational changes during the formation of casein complex with poly-L-arginine than with poly-L-lysine resulting from stronger interactions, which was also reflected in the bigger growth of (PLArg/casein)_n films with the number of deposited layers.

Functionalized Anion-Exchange Membranes Facilitate Electrodialysis of Citrate and Phosphate from Model Dairy Wastewater

In this study, the preparation of a new, functional anion-exchange membrane (AEM), containing guanidinium groups as the anion-exchanging sites (Gu-100), is described as well as the membrane characterization by XPS, water uptake, permselectivities, and electrical resistances. The functional membrane was also employed in pH-dependent electrodialysis experiments using model dairy wastewater streams. The properties of the new membrane are compared to those of a commercially available anion-exchange membrane bearing conventional quaternary ammonium groups (Gu-0). Guanidinium was chosen for its specific binding properties toward oxyanions: e.g., phosphate. This functional moiety was covalently coupled to an acrylate monomer via a facile two-step synthesis to yield bulk-modified membranes upon polymerization. Significant differences were observed in the electrodialysis experiments for Gu-0 and Gu-100 at pH 7, showing an enhanced phosphate and citrate transport for Gu-100 in comparison to Gu-0. At pH 10 the difference is much more pronounced: for Gu-0 membranes almost no phosphate and citrate transport could be detected, while the Gu-100 membranes transported both ions significantly. We conclude that having guanidinium groups as anion-exchange sites improves the selectivity of AEMs. As the presented monomer synthesis strategy is modular, we consider the implementation of functional groups into a polymer-based membrane via the synthesis of tailor-made monomers as an important step toward selective ion transport, which is relevant for various fields, including water treatment processes and fuel cells.

Synthesis and Evaluation of Anticancer Activities of Novel C-28 Guanidine-Functionalized Triterpene Acid Derivatives

Triterpene acids, namely, 20,29-dihydrobetulinic acid (BA), ursolic acid (UA) and oleanolic acid (OA) were converted into C-28-amino-functionalized triterpenoids 4–7, 8a, 15, 18 and 20. These compounds served as precursors for the synthesis of novel guanidine-functionalized triterpene acid derivatives 9b–12b, 15c, 18c and 20c. The influence of the guanidine group on the antitumor properties of triterpenoids was investigated. The cytotoxicity was tested on five human tumor cell lines (Jurkat, K562, U937, HEK, and Hela), and compared with the tests on normal human fibroblasts. The antitumor activities of the most tested guanidine derivatives was lower, than that of corresponding amines, but triterpenoids with the guanidine group were less toxic towards human fibroblasts. The introduction of the tris(hydroxymethyl)aminomethane moiety into the molecules of triterpene acids markedly enhanced the cytotoxic activity of the resulting conjugates 15, 15c, 18b,c and 20b,c irrespective of the triterpene skeleton type. The dihydrobetulinic acid amine 15, its guanidinium derivative 15c and guanidinium derivatives of ursolic and oleanolic acids 18c and 20c were selected for extended biological investigations in Jurkat cells, which demonstrated that the antitumor activity of these compounds is mediated by induction of cell cycle arrest at the S-phase and apoptosis.

Non-peptidic guanidinium-functionalized silica nanoparticles as selective mitochondria-targeting drug nanocarriers

We report on the design and fabrication of a Fe₃O₄ core-mesoporous silica nanoparticle shell (Fe₃O₄@MSNs)-based mitochondria-targeting drug nanocarrier. A guanidinium derivative (GA) was conjugated onto the Fe₃O₄@MSNs as the mitochondria-targeting ligand. The fabrication of the Fe₃O₄@MSNs and their functionalization with GA were carried out by the sol-gel polymerization of alkoxysilane groups. Doxorubicin (DOX), an anti-cancer drug, was loaded into the pores of a GA-attached Fe₃O₄@MSNs due to both its anti-cancer properties and to allow for the fluorescent visualization of the nanocarriers. The selective and efficient mitochondria-targeting ability of a DOX-loaded GA-Fe₃O₄@MSNs (DOX/GA-Fe₃O₄@MSNs) was demonstrated by a co-localization study, transmission electron microscopy, and a fluorometric analysis on isolated mitochondria. It was found that the DOX/GA-Fe₃O₄@MSNs selectively accumulated into mitochondria within only five minutes; to the best of our knowledge, this is the shortest accumulation time reported for mitochondria targeting systems. Moreover, 2.6 times higher amount of DOX was accumulated in mitochondria by DOX/GA-Fe₃O₄@MSNs than by DOX/TPP-Fe₃O₄@MSNs. A cell viability assay indicated that the DOX/GA-Fe₃O₄@MSNs have high cytotoxicity to cancer cells, whereas the GA-Fe₃O₄@MSNs without DOX are non-cytotoxic; this indicates that the DOX/GA-Fe₃O₄@MSNs have great potential for use as biocompatible and effective mitochondria-targeting nanocarriers for cancer therapy.

Insights into Membrane Translocation of Protegrin Antimicrobial Peptides by Multistep Molecular Dynamics Simulations

Protegrin-1 (PG-1) is a cationic arginine-rich antimicrobial peptide. It is widely accepted that PG-1 induces membrane disruption by forming pores that lead to cell death. However, the insertion mechanism for these highly cationic peptides into the hydrophobic membrane environment is still poorly understood at the molecular scale. It has previously been determined that the association of arginine guanidinium and lipid phosphate groups results in strong bidentate bonds that stabilize peptide-lipid complexes. It has also been suggested that arginine residues are able to drag phosphate groups as they insert inside the membrane to form a toroidal pore. However, whether bidentate bonds play a significant role in inducing a pore formation remains unclear. To investigate the role of bidentate complexes in PG-1 translocation, we conducted molecular dynamics simulations. Two computational electroporation methods were implemented to examine the translocation process. We found that PG-1 could insert into the membrane, provided the external electric potential is large enough to first induce a water column or a pore within the lipid bilayer membrane. We also found that the highly charged PG-1 is capable in itself of inducing molecular electroporation. Substitution of arginines with charge-equivalent lysines showed a markedly reduced tendency for insertion. This indicates that the guanidinium group likely facilitates PG-1 translocation. Potential of mean force calculations suggests that peptide insertion inside the hydrophobic environment of the membrane core is not favored. We found that formation of a water column or a pore might be a prerequisite for PG-1 translocation. We also found that PG-1 can stabilize the pore after insertion. We suggest that PG-1 could be a pore inducer and stabilizer. This work sheds some light on PG-1 translocation mechanisms at the molecular level. Methods presented in this study may be extended to other arginine-rich antimicrobial and cell-penetrating peptides.

Effects of polyhexamethylene guanidine phosphate on human gingival fibroblasts

OBJECTIVE

Polyhexamethylene guanidine phosphate (PHMG-P) was compared to chlorhexidine (CHX) in order to determine potential cytotoxic and immune-modulatory effects on human gingival fibroblasts.

MATERIALS AND METHODS

Cytotoxic effects of PHMG-P and CHX on human gingival fibroblasts were assessed using cell viability assay at various time points and concentrations. The effects of PHMG-P and CHX on the secretion of prostaglandin (PG) E₂, interleukin (IL)-6, IL-8 and matrix metalloproteinase (MMP)-1 by non-stimulated or IL-1β stimulated fibroblasts were evaluated by enzyme-linked immunosorbent assays.

RESULTS

PHMG-P concentration 0.00009% led to the total loss of fibroblast viability within 24 h, whereas inhibition of fibroblast viability by CHX occurred at significantly higher concentrations of 0.0009% (p < .001). Short-term exposure to 0.005% PHMG-P led to loss of fibroblast viability after 5 min, whilst cells exposed to 0.005% CHX survived 30 min of treatment (p < .001). IL-1β stimulation induced an inflammatory response with a significant increase in the secretion of PGE₂, IL-6, IL-8 and MMP-1. Treatment of IL-1β stimulated fibroblasts in combination with PHMG-P or CHX at concentrations of 0.000045 or 0.0.00009% resulted in significantly decreased PGE₂, IL-6, IL-8 and MMP-1 levels. PHMG-P or CHX alone did not affect the baseline secretion of PGE₂, IL-6, IL-8 or MMP-1 by gingival fibroblasts.

CONCLUSIONS

Cytotoxic effects on gingival fibroblasts were triggered by both PHMG-P and CHX at concentrations below those used in clinical practice. The tested antiseptics did not cause inflammation and reduced IL-1β-induced secretion of inflammatory mediators and collagenase by gingival fibroblasts, which suggests anti-inflammatory properties.

An efficient synthesis of indolo[2,3-b]quinoline guanidine derivatives with their in vitro and in vivo study

An optimization of the guanidylation process by verifying the efficacy of common guanylation reagents in order to obtain the guanidine derivatives of indolo[2,3-b]quinoline has been performed. As a result, a high-yield procedure using N,N′-di-Boc-N′′-triflylguanidine was applied to synthesize the guanidine derivative of indolo[2,3-b]quinoline 1 in a gram scale for specific in vitro and in vivo biological research. Extensive studies on the antiproliferative activity against eight human tumor cell lines were completed. Compound 1 revealed the highest activity against A549 lung adenocarcinoma and MCF7 breast cancer cell lines. Thus, 1 was evaluated for the in vivo anticancer activity against 4T1 mammary gland carcinoma and KLN205 murine lung carcinoma in mouse models. The anticancer effect was observed in the KLN205 model with a 37% tumor growth inhibition at the 20 mg/kg dose. This anticancer activity of 1 was comparable to that of cyclophosphamide which inhibited murine lung tumor growth in the range of 27–43% at the dose of 100 mg/kg. The biochemistry research after 1 admission, including measurements of blood parameters like alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and urea and creatinine, were also performed.

Effect of replacing main-chain ureas with thiourea and guanidinium surrogates on the bactericidal activity of membrane active oligourea foldamers

Membrane-active foldamers have recently emerged as potential mimics of antimicrobial peptides (AMPs). Amphiphilic cationic helical N,N'-linked oligoureas are one such class of AMP mimics with activities in vitro against a broad range of bacteria including Bacillus anthracis, a Gram-positive sporulating bacillus and causing agent of anthrax. Here we have used site-selective chemical modifications of the oligourea backbone to gain additional insight into the relationship between structure and function and modulate anthracidal activity. A series of analogues in which urea linkages at selected positions are replaced by thiourea and guanidium surrogates have been prepared on solid support and tested against different bacterial forms of B. anthracis (germinated spores and encapsulated bacilli). Urea→thiourea and urea→guanidinium replacements close to the negative end of the helix dipole led to analogues with increased potency and selectivity for B. anthracis versus mammalian cells.

Nanoescapology: progress toward understanding the endosomal escape of polymeric nanoparticles

Using nanoparticles to deliver drugs to cells has the potential to revolutionize the treatment of many diseases, including HIV, cancer, and diabetes. One of the major challenges facing this field is controlling where the drug is trafficked once the nanoparticle is taken up into the cell. In particular, if drugs remain localized in an endosomal or lysosomal compartment, the therapeutic can be rendered completely ineffective. To ensure the design of more effective delivery systems we must first develop a better understanding of how nanoparticles and their cargo are trafficked inside cells. This needs to be combined with an understanding of what characteristics are required for nanoparticles to achieve endosomal escape, along with methods to detect endosomal escape effectively. This review is focused into three sections: first, an introduction to the mechanisms governing internalization and trafficking in cells, second, a discussion of methods to detect endosomal escape, and finally, recent advances in controlling endosomal escape from polymer- and lipid-based nanoparticles, with a focus on engineering materials to promote endosomal escape. WIREs Nanomed Nanobiotechnol 2017, 9:e1452. doi: 10.1002/wnan.1452 For further resources related to this article, please visit the WIREs website.

Cross-Linked Polymer-Stabilized Nanocomposites for the Treatment of Bacterial Biofilms

Infections caused by bacterial biofilms are an emerging threat to human health. Conventional antibiotic therapies are ineffective against biofilms due to poor penetration of the extracellular polymeric substance secreted by colonized bacteria coupled with the rapidly growing number of antibiotic-resistant strains. Essential oils are promising natural antimicrobial agents; however, poor solubility in biological conditions limits their applications against bacteria in both dispersed (planktonic) and biofilm settings. We report here an oil-in-water cross-linked polymeric nanocomposite (∼250 nm) incorporating carvacrol oil that penetrates and eradicates multidrug-resistant (MDR) biofilms. The therapeutic potential of these materials against challenging wound biofilm infections was demonstrated through specific killing of bacteria in a mammalian cell-biofilm coculture wound model.

Delivery of Copper-chelating Trientine (TETA) to the central nervous system by surface modified liposomes

The existence of the blood-brain barrier (BBB) complicates the treatment of many central nervous system (CNS) disorders, including the copper storage disease, Wilson's disease. Its CNS symptoms represent a serious problem, since therapeutics for Wilson's disease do not cross the BBB. One strategy to overcome this obstacle is the transfer of drugs across the BBB with colloidal carrier systems like liposomes. The aim of the present study was to encapsulate triethylenetetramine (TETA), a copper chelating agent, into surface modified liposomes and to investigate their permeation across the BBB. Liposomes were modified with cationized bovine serum albumin or penetratin, a cell penetrating peptide. Liposomes were characterized regarding size, PDI, zeta potential and encapsulation efficiency. Size was between 139.4±1.9nm to 171.1±3.5nm with PDI's below 0.2. Zeta potentials of vectorized liposomes were at least 6.9mV higher than those of standard liposomes. Cryo-TEM micrographs displayed liposomal structure, integrity and the similarity of structure and size between loaded, unloaded, vectorized and non- vectorized liposomes. In vivo experiments in rats showed an up to 16-fold higher brain uptake of TETA in vectorized liposomes compared to free TETA or TETA in non-vectorized liposomes, proving successful brain delivery using target seeking surface modifications. Tissue analysis indicated TETA concentrations in the brain being high enough to treat Wilson's disease.

Lipoic acid functionalized amino acids cationic lipids as gene vectors

A series of reducible cationic lipids 4a-4f with different amino acid polar-head groups were prepared. The novel lipid contains a hydrophobic lipoic acid (LA) moiety, which can be reduced under reductive conditions to release of the encapsulated plasmid DNA. The particle size, zeta potential and cellular uptake of lipoplexes formed with DNA, as well as the transfection efficacy (TE) were characterized. The TE of the cationic lipid based on arginine was especially high, and was 2.5times higher than that of a branched polyethylenimine in the presence of 10% serum.

Effect of Stearylguanidinium-Modified POPC Vesicles on the Melting Behavior of tRNA Molecules

Lipid membranes interact with biomolecules via noncovalent bonding interactions, wherein the physicochemical membrane properties are key factors in the recognition and rearrangement of biomolecule conformation. In this study, vesicles were prepared using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and stearylguanidinium (SG) to improve the affinity between the membrane and tRNA. Membrane fluidity decreased and dehydration of the membrane surface increased with increasing SG levels, suggesting that SG molecules could make the membrane rigid and induce a liquid-ordered (lo)-like phase. The binding constant (Ka) between nucleotide and lipid was evaluated by turbidity analysis; the Ka value for POPC/SG = (86/14) was 2.9 × 10(4) M(-1) but was slightly decreased by vesicles in the lo-like phase. CD spectra of tRNA by the presence of POPC/SG vesicles showed C-G selective base cleavage in tRNA during heat denaturation. POPC/SG = (61/39) and POPC/SG = (40/60) effectively led to C-G base pair cleavage at the melting temperature of tRNA.