Hydrophobicity: The door to drug delivery.

The engineering of intracellular delivery systems with the goal of achieving personalized medicine has been encouraged by advances in nanomaterial science as well as a greater understanding of diseases and of the biochemical pathways implicated in many disorders. The development of vectors able to transport the drug to a target location and release it only on demand is undoubtedly the primary issue. From a molecular perspective, the topography of drug carrier surfaces is directly related to the design of an effective drug carrier because it provides a physical hint to modifying its interactions with biological systems. For instance, the initial ratio of hydrophilic to hydrophobic surfaces and the changes brought about by external factors enable the release or encapsulation of a therapeutic molecule and the ability of the nanosystem to cross biological barriers and reach its target without causing systemic toxicity. The first step in creating new materials with enhanced functionality is to comprehend and characterize the interplay between hydrophilic and hydrophobic molecules at the molecular level. Therefore, the focus of this review is on the function of hydrophobicity, which is essential for matching the complexity of biological environments with the intended functionality.

Unveiling the mechanism of action of acylated temporin L analogues against multidrug-resistant Candida albicans.

The increasing resistance of fungi to conventional antifungal drugs has prompted worldwide the search for new compounds. In this work, we investigated the antifungal properties of acylated Temporin L derivatives, Pent-1B and Dec-1B, against Candida albicans, including the multidrug-resistant strains. Acylated peptides resulted to be active both on reference and clinical strains with MIC values ranging from 6.5 to 26 µM, and they did not show cytotoxicity on human keratinocytes. In addition, we also observed a synergistic or additive effect with voriconazole for peptides Dec-1B and Pent-1B through the checkerboard assay on voriconazole-resistant Candida strains. Moreover, fluorescence-based assays, NMR spectroscopy, and confocal microscopy elucidated a potential membrane-active mechanism, consisting of an initial electrostatic interaction of acylated peptides with fungal membrane, followed by aggregation and insertion into the lipid bilayer and causing membrane perturbation probably through a carpeting effect.

Myxinidin-Derived Peptide against Biofilms Caused by Cystic Fibrosis Emerging Pathogens.

Chronic lung infections in cystic fibrosis (CF) patients are triggered by multidrug-resistant bacteria such as Pseudomonas aeruginosa, Achromobacter xylosoxidans, and Stenotrophomonas maltophilia. The CF airways are considered ideal sites for the colonization and growth of bacteria and fungi that favor the formation of mixed biofilms that are difficult to treat. The inefficacy of traditional antibiotics reinforces the need to find novel molecules able to fight these chronic infections. Antimicrobial peptides (AMPs) represent a promising alternative for their antimicrobial, anti-inflammatory, and immunomodulatory activities. We developed a more serum-stable version of the peptide WMR (WMR-4) and investigated its ability to inhibit and eradicate C. albicans, S. maltophilia, and A. xylosoxidans biofilms in both in vitro and in vivo studies. Our results suggest that the peptide is able better to inhibit than to eradicate both mono and dual-species biofilms, which is further confirmed by the downregulation of some genes involved in biofilm formation or in quorum-sensing signaling. Biophysical data help to elucidate its mode of action, showing a strong interaction of WMR-4 with lipopolysaccharide (LPS) and its insertion in liposomes mimicking Gram-negative and Candida membranes. Our results support the promising therapeutic application of AMPs in the treatment of mono- and dual-species biofilms during chronic infections in CF patients.

WMR Peptide as Antifungal and Antibiofilm against Albicans and Non-Albicans Candida Species: Shreds of Evidence on the Mechanism of Action.

Candida species are the most common fungal pathogens infecting humans and can cause severe illnesses in immunocompromised individuals. The increased resistance of Candida to traditional antifungal drugs represents a great challenge in clinical settings. Therefore, novel approaches to overcome antifungal resistance are desired. Here, we investigated the use of an antimicrobial peptide WMR against Candida albicans and non-albicans Candida species in vitro and in vivo. Results showed a WMR antifungal activity on all Candida planktonic cells at concentrations between 25 µM to >50 µM and exhibited activity at sub-MIC concentrations to inhibit biofilm formation and eradicate mature biofilm. Furthermore, in vitro antifungal effects of WMR were confirmed in vivo as demonstrated by a prolonged survival rate of larvae infected by Candida species when the peptide was administered before or after infection. Additional experiments to unravel the antifungal mechanism were performed on C. albicans and C. parapsilosis. The time-killing curves showed their antifungal activity, which was further confirmed by the induced intracellular and mitochondrial reactive oxygen species accumulation; WMR significantly suppressed drug efflux, down-regulating the drug transporter encoding genes CDR1. Moreover, the ability of WMR to penetrate within the cells was demonstrated by confocal laser scanning microscopy. These findings provide novel insights for the antifungal mechanism of WMR against Candida albicans and non-albicans, providing fascinating scenarios for the identification of new potential antifungal targets.

Engineering of Janus-Like Dendrimers with Peptides Derived from Glycoproteins of Herpes Simplex Virus Type 1: Toward a Versatile and Novel Antiviral Platform.

Novel antiviral nanotherapeutics, which may inactivate the virus and block it from entering host cells, represent an important challenge to face viral global health emergencies around the world. Using a combination of bioorthogonal copper-catalyzed 1,3-dipolar alkyne/azide cycloaddition (CuAAC) and photoinitiated thiol-ene coupling, monofunctional and bifunctional peptidodendrimer conjugates were obtained. The conjugates are biocompatible and demonstrate no toxicity to cells at biologically relevant concentrations. Furthermore, the orthogonal addition of multiple copies of two different antiviral peptides on the surface of a single dendrimer allowed the resulting bioconjugates to inhibit Herpes simplex virus type 1 at both the early and the late stages of the infection process. The presented work builds on further improving this attractive design to obtain a new class of therapeutics.

Antiviral Potential of Naphthoquinones Derivatives Encapsulated within Liposomes.

HSV infections, both type 1 and type 2, are among the most widespread viral diseases affecting people of all ages. Their symptoms could be mild, with cold sores up to 10 days of infection, blindness and encephalitis caused by HSV-1 affecting immunocompetent and immunosuppressed individuals. The severe effects derive from co-evolution with the host, resulting in immune evasion mechanisms, including latency and growing resistance to acyclovir and derivatives. An efficient alternative to controlling the spreading of HSV mutations is the exploitation of new drugs, and the possibility of enhancing their delivery through the encapsulation of drugs into nanoparticles, such as liposomes. In this work, liposomes were loaded with a series of 2-aminomethyl- 3-hydroxy-1,4-naphthoquinones derivatives with n-butyl (compound 1), benzyl (compound 2) and nitrobenzene (compound 3) substituents in the primary amine of naphthoquinone. They were previously identified to have significant inhibitory activity against HSV-1. All of the aminomethylnaphthoquinones derivatives encapsulated in the phosphatidylcholine liposomes were able to control the early and late phases of HSV-1 replication, especially those substituted with the benzyl (compound 2) and nitrobenzene (compound 3), which yields selective index values that are almost nine times more efficient than acyclovir. The growing interest of the industry in topical administration against HSV supports our choice of liposome as a drug carrier of aminomethylnaphthoquinones derivatives for formulations of in vivo pre-clinical assays.

Avidin Localizations in pH-Responsive Polymersomes for Probing the Docking of Biotinylated (Macro)molecules in the Membrane and Lumen.

To mimic organelles and cells and to construct next-generation therapeutics, asymmetric functionalization and location of proteins for artificial vesicles is thoroughly needed to emphasize the complex interplay of biological units and systems through spatially separated and spatiotemporal controlled actions, release, and communications. For the challenge of vesicle (= polymersome) construction, the membrane permeability and the location of the cargo are important key characteristics that determine their potential applications. Herein, an in situ and post loading process of avidin in pH-responsive and photo-cross-linked polymersomes is developed and characterized. First, loading efficiency, main location (inside, lumen, outside), and release of avidin under different conditions have been validated, including the pH-stable presence of avidin in polymersomes' membrane outside and inside. This advantageous approach allows us to selectively functionalize the outer and inner membranes as well as the lumen with several bio(macro)molecules, generally suited for the construction of asymmetrically functionalized artificial organelles. In addition, a fluorescence resonance energy transfer (FRET) effect was used to study the permeability or uptake of the polymersome membrane against a broad range of biotinylated (macro)molecules (different typology, sizes, and shapes) under different conditions.

Novel temporin L antimicrobial peptides: promoting self-assembling by lipidic tags to tackle superbugs.

The rapid development of antimicrobial resistance is pushing the search in the discovering of novel antimicrobial molecules to prevent and treat bacterial infections. Self-assembling antimicrobial peptides, as the lipidated peptides, are a novel and promising class of molecules capable of meeting this need. Based on previous work on Temporin L analogs, several new molecules lipidated at the N- or and the C-terminus were synthesised. Our goal is to improve membrane interactions through finely tuning self-assembly to reduce oligomerisation in aqueous solution and enhance self-assembly in bacterial membranes while reducing toxicity against human cells. The results here reported show that the length of the aliphatic moiety is a key factor to control target cell specificity and the oligomeric state of peptides either in aqueous solution or in a membrane-mimicking environment. The results of this study pave the way for the design of novel molecules with enhanced activities.

OctoPartenopin: Identification and Preliminary Characterization of a Novel Antimicrobial Peptide from the Suckers of Octopus vulgaris.

Microorganism resistance to conventional antibiotics represents one of the major global health concerns. This paper focuses on a peptide (OctoPartenopin) extracted from suckers of Octopus vulgaris; bioassay-guided chromatographic fractionation was used to identify this sequence, which holds significant antibacterial activity against Gram-positive and Gram-negative bacteria. OctoPartenopin is encrypted within the calponin sequence and was associated with the high levels of proteolytic activity already reported in octopus arm suckers. We synthesized the parent peptide and four analogues; all peptide were tested for their antibacterial and antibiofilm activities. Preliminary antibiofilm experiments showed that that one of the analogues had the best activity in both inhibition and eradication of biofilm of all three microorganisms tested. The occurrence of OctoPartenopin in arm suckers provided novel speculative information on animal behavior, as concerns maternal care of fertilized eggs. Our results highlight that suckers are a rich source of multifaceted peptides to develop alternative antimicrobial agents and food preservatives.

Quantum dots functionalized with gH625 attenuate QDs oxidative stress and lethality in Caenorhabditis elegans: a model system.

Nanomaterials have revolutionized many scientific fields and are widely applied to address environmental problems and to develop novel health care strategies. However, their mechanism of action is still poorly understood. Several nanomaterials for medical applications are based on quantum dots (QDs). Despite their amazing physico-chemical properties, quantum dots display significant adverse effects. In the present study, the effects of QDs on the motor nervous system of nematodes Caenorhabditis elegans have been investigated as a non-mammalian alternative model. We also explored the possibility of modifying the toxicity of QDs by coating with a cell-penetrating peptide gH625 and thus we analysed the effects determined by QDs-gH625 complexes on the nematodes. With this work, we have demonstrated, by in vivo experiments, that the peptide gH625 is able to reduce the side effects of metallic nanoparticle making them more suitable for medical applications.

Enhancing the Potency of Antimicrobial Peptides through Molecular Engineering and Self-Assembly.

Healthcare-associated infections resulting from bacterial attachment and biofilm formation on medical implants are posing significant challenges in particular with the emergence of bacterial resistance to antibiotics. Here, we report the design, synthesis and characterization of self-assembled nanostructures, which integrate on their surface antibacterial peptides. The antibacterial WMR peptide, which is a modification of the native sequence of the myxinidin, a marine peptide isolated from the epidermal mucus of hagfish, was used considering its enhanced activity against Gram-negative bacteria. WMR was linked to a peptide segment of aliphatic residues (AAAAAAA) containing a lipidic tail (C19H38O2) attached to the ε-amino of a terminal lysine to generate a peptide amphiphile (WMR PA). The self-assembly of the WMR PA alone, or combined with coassembling shorter PAs, was studied using spectroscopy and microscopy techniques. The designed PAs were shown to self-assemble into stable nanofiber structures and these nanoassemblies significantly inhibit biofilm formation and eradicate the already formed biofilms of Pseudomonas aeruginosa (Gram-negative bacteria) and Candida albicans (pathogenic fungus) when compared to the native WMR peptide. Our results provide insights into the design of peptide based supramolecular assemblies with antibacterial activity, and establish an innovative strategy to develop self-assembled antimicrobial materials for biomedical applications.

gH625 Cell-Penetrating Peptide Promotes the Endosomal Escape of Nanovectorized siRNA in a Triple-Negative Breast Cancer Cell Line.

The use of small interfering RNA (siRNA) to regulate oncogenes appears as a promising strategy in the context of cancer therapy, especially if they are vectorized by a smart delivery system. In this study, we investigated the cellular trafficking of a siRNA nanovector (called CS-MSN) functionalized with the cell-penetrating peptide gH625 in a triple-negative breast cancer model. With complementary techniques, we showed that siRNA nanovectors were internalized by both clathrin- and caveolae-mediated endocytosis. The presence of gH625 at the surface of the siRNA nanovector did not modify the entry pathway of CS-MSN, but it increased the amount of siRNA found inside the cells. Results suggested an escape of siRNA from endosomes, which is enhanced by the presence of the peptide gH625, whereas nanoparticles continued their trafficking into lysosomes. The efficiency of CS-MSN to inhibit the GFP in MDA-MB-231 cells was 1.7-fold higher than that of the nanovectors without gH625.

Genotoxicity of gold nanoparticles functionalized with indolicidin towards Saccharomyces cerevisiae.

The toxic effects of gold nanoparticles surface-functionalized with the antimicrobial peptide indolicidin (AuNPs-indolicidin) towards the yeast Saccharomyces cerevisiae, one of the major eukaryotic model organisms, have been evaluated. Growth and survival, genotoxicity, as measured by comet assay, and expression of the YCA1, an apoptosis indicating gene, following 72hr exposure of yeast to AuNPs-indolicidin, and to AuNPs and indolicidin alone have been examined. The gold nanoparticles exerted toxicity with DNA damage, accompanied by reactive oxygen species production (ROS), but they do not inhibit yeast growth and viability. Genotoxicity was less pronounced for surface-functionalized nanoparticles, showing that S. cerevisiae is quite resistant to the complex AuNPs-indolicidin. A progressive reduction of the genotoxic effect was observed along 72hr exposure, presumably due to the activation of DNA repair mechanisms. These findings suggest the occurrence of a physiological protective response of S. cerevisiae towards nanoparticles, thereby providing useful information to the assessment of the environmental impact of metal nanoparticles.

Infectivity inhibition by overlapping synthetic peptides derived from the gH/gL heterodimer of herpes simplex virus type 1.

Herpes simplex virus (HSV) is a human pathogen that infects epithelial cells. The cutaneous lesions, caused by the virus, spread to the nervous system creating several complications. Fusion of host membranes with the viral envelope is mandatory and mediated by a group of glycoproteins conserved in all Herpesviridae subfamilies, such as the glycoproteins B (gB), H (gH), L (gL) and D (gD). We investigated the inhibitory activity mediated by synthetic overlapping peptides spanning the entire ectodomains of gH and gL glycoproteins. We have performed a brute analysis of the complete gH/gL heterodimer in order to explore the inhibitory activity of peptides modelled on these glycoproteins against HSV-1 infection. Twenty-four of the gH peptides at a concentration of 150 µM reached the 50% of inhibition cut-off. Interestingly, they are mainly located in the gH carboxy-terminal domain. None of the gL peptides had a clear inhibiting effect. No peptide toxicity was observed by lactate dehydrogenase assay at the concentrations used in our experimental conditions. HSV-1 therapy is based on acyclovir treatment, but some resistant strains are emerging. In this scenario, innovative approaches for HSV-1 treatment are necessary. Our data support the direct involvement of the described domains in the process of virus penetration; therefore, these results are of relevance to the potential development of novel therapeutic compounds to prevent HSV-1 infections. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Toxicity Effects of Functionalized Quantum Dots, Gold and Polystyrene Nanoparticles on Target Aquatic Biological Models: A Review.

Nano-based products are widespread in several sectors, including textiles, medical-products, cosmetics, paints and plastics. Nanosafety and safe-by-design are driving nanoparticle (NP) production and applications through NP functionalization (@NPs). Indeed, @NPs frequently present biological effects that differ from the parent material. This paper reviews the impact of quantum dots (QDs), gold nanoparticles (AuNPs), and polystyrene-cored NPs (PSNPs), evidencing the role of NP functionalization in toxicity definition. Key biological models were taken into consideration for NP evaluation: Saccharomyces cerevisiae, fresh- (F) and saltwater (S) microalgae (Raphidocelis subcapitata (F), Scenedesmus obliquus (F) and Chlorella spp. (F), and Phaeodactylum tricornutum (S)), Daphnia magna, and Xenopus laevis. QDs are quite widespread in technological devices, and they are known to induce genotoxicity and oxidative stress that can drastically change according to the coating employed. For example, AuNPs are frequently functionalized with antimicrobial peptides, which is shown to both increase their activity and decrease the relative environmental toxicity. P-NPs are frequently coated with NH2- for cationic and COOH- for anionic surfaces, but when positively charged toxicity effects can be observed. Careful assessment of functionalized and non-functionalized NPs is compulsory to also understand their potential direct and indirect effects when the coating is removed or degraded.

Cyclic Peptides as Novel Therapeutic Microbicides: Engineering of Human Defensin Mimetics.

Cyclic peptides are receiving significant attention thanks to their antimicrobial activity and high serum stability, which is useful to develop and design novel antimicrobial agents. Antimicrobial peptides appear to be key components of innate defences against bacteria, viruses, and fungi. Among the others, defensins possess a strong microbicidial activity. Defensins are cationic and amphipathic peptides with six cysteine residues connected by three disulfide bonds found in plants, insects, and mammals; they are divided in three families: α-, ß-, and θ-defensins. α-Defensins are contained in the primary granules of human neutrophils; ß-defensins are expressed in human epithelia; and θ-defensins are pseudo-cyclic defensins not found in humans, but in rhesus macaques. The structural diversities among the three families are reflected in a different antimicrobial action as well as in serum stability. The engineering of these peptides is an exciting opportunity to obtain more functional antimicrobial molecules highlighting their potential as therapeutic agents. The present review reports the most recent advances in the field of cyclic peptides with a specific regard to defensin analogs.

Function Oriented Molecular Design: Dendrimers as Novel Antimicrobials.

In recent years innovative nanostructures are attracting increasing interest and, among them, dendrimers have shown several fields of application. Dendrimers can be designed and modified in plentiful ways giving rise to hundreds of different molecules with specific characteristics and functionalities. Biomedicine is probably the field where these molecules find extraordinary applicability, and this is probably due to their multi-valency and to the fact that several other chemicals can be coupled to them to obtain desired compounds. In this review we will describe the different production strategies and the tools and technologies for the study of their characteristics. Finally, we provide a panoramic overview of their applications to meet biomedical needs, especially their use as novel antimicrobials.

gH625: a milestone in understanding the many roles of membranotropic peptides.

Here, we review the current knowledge about viral derived membranotropic peptides, and we discuss how they may be used for many therapeutic applications. While they have been initially discovered in viral fusion proteins and have been involved in the mechanism of viral entry, it is now clear that their features and their mode of interaction with membrane bilayers can be exploited to design viral inhibitors as well as to favor delivery of cargos across the cell membrane and across the blood-brain barrier. The peptide gH625 has been extensively used for all these purposes and provides a significant contribution to the field. We describe the roles of this sequence in order to close the gap between the many functions that are now emerging for membranotropic peptides.

Marine Antimicrobial Peptides: Nature Provides Templates for the Design of Novel Compounds against Pathogenic Bacteria.

The discovery of antibiotics for the treatment of bacterial infections brought the idea that bacteria would no longer endanger human health. However, bacterial diseases still represent a worldwide treat. The ability of microorganisms to develop resistance, together with the indiscriminate use of antibiotics, is mainly responsible for this situation; thus, resistance has compelled the scientific community to search for novel therapeutics. In this scenario, antimicrobial peptides (AMPs) provide a promising strategy against a wide array of pathogenic microorganisms, being able to act directly as antimicrobial agents but also being important regulators of the innate immune system. This review is an attempt to explore marine AMPs as a rich source of molecules with antimicrobial activity. In fact, the sea is poorly explored in terms of AMPs, but it represents a resource with plentiful antibacterial agents performing their role in a harsh environment. For the application of AMPs in the medical field limitations correlated to their peptide nature, their inactivation by environmental pH, presence of salts, proteases, or other components have to be solved. Thus, these peptides may act as templates for the design of more potent and less toxic compounds.

Investigating the inclusion properties of aromatic amino acids complexing beta-cyclodextrins in model peptides.

Cyclodextrins are commonly used as complexing agents in biological, pharmaceutical, and industrial applications since they have an effect on protein thermal and proteolytic stability, refolding yields, solubility, and taste masking. ß-cyclodextrins (ß-CD), because of their cavity size are a perfectly suited complexing agent for many common guest moieties. In the case of peptide-cyclodextrin and protein-cyclodextrin host-guest complexes the aromatic amino acids are reported to be the principal responsible of the interaction. For these reasons, we have investigated the inclusion properties of nine designed tripeptides, obtained permuting the position of two L-alanines (Ala, A) with that of one L-tryptophan (Trp, W), L-phenylalanine (Phe, F), or L-tyrosine (Tyr, Y), respectively. Interestingly, the position of the aromatic side-chain in the sequence appears to modulate the ß-CD:peptide binding constants, determined via UV-Vis and NMR spectroscopy, which in turn assumes values higher than those reported for the single amino acid. The tripeptides containing a tyrosine showed the highest binding constants, with the central position in the Ac-AYA-NH2 peptide becoming the most favorite for the interaction. A combined NMR and Molecular Docking approach permitted to build detailed complex models, highlighting the stabilizing interactions of the neighboring amino acids backbone atoms with the upper rim of the ß-CD.