A new water-based topical carrier with polar skin-lipids

A new water-based topical formulation is presented that aims at providing good penetration properties for both lipophilic and hydrophilic drugs with as small a disturbance of the skin barrier function as possible. The formulation contains dispersed lipids in a ratio resembling that of human skin. The capacity to deliver is addressed in this first study while the mild effect on skin will be presented later. Three variations of the lipid formulation were investigated by use of pigskin in vitro diffusion cell. The hydrophilic 5(6)-carboxyfluorescein (CF) and the lipophilic acridine orange 10-nonyl bromide (AO) were used as model drug substances. The results showed that the delivery properties of the new formulation exceeded that of the references (vaseline and xanthan gum gel). The effect was largest for lipophilic AO where all lipid matrix formulations were superior in amount detected in the skin. The results for the hydrophilic CF were also promising. Especially efficient was the lipid formulation containing the non-ionic adjuvants tetra ethylene glycol monododecyl ether and polyoxyethylene 23 dodecyl ether. The additional in vivo study suggests that the used in vitro model has qualitative bearing on relevant in vivo situations

End-Tagging of Ultra-Short Antimicrobial Peptides by W/F Stretches to Facilitate Bacterial Killing

BACKGROUND: Due to increasing resistance development among bacteria, antimicrobial peptides (AMPs), are receiving increased attention. Ideally, AMP should display high bactericidal potency, but low toxicity against (human) eukaryotic cells. Additionally, short and proteolytically stable AMPs are desired to maximize bioavailability and therapeutic versatility. METHODOLOGY AND PRINCIPAL FINDINGS: A facile approach is demonstrated for reaching high potency of ultra-short antimicrobal peptides through end-tagging with W and F stretches. Focusing on a peptide derived from kininogen, KNKGKKNGKH (KNK10) and truncations thereof, end-tagging resulted in enhanced bactericidal effect against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Through end-tagging, potency and salt resistance could be maintained down to 4-7 amino acids in the hydrophilic template peptide. Although tagging resulted in increased eukaryotic cell permeabilization at low ionic strength, the latter was insignificant at physiological ionic strength and in the presence of serum. Quantitatively, the most potent peptides investigated displayed bactericidal effects comparable to, or in excess of, that of the benchmark antimicrobial peptide LL-37. The higher bactericidal potency of the tagged peptides correlated to a higher degree of binding to bacteria, and resulting bacterial wall rupture. Analogously, tagging enhanced peptide-induced rupture of liposomes, particularly anionic ones. Additionally, end-tagging facilitated binding to bacterial lipopolysaccharide, both effects probably contributing to the selectivity displayed by these peptides between bacteria and eukaryotic cells. Importantly, W-tagging resulted in peptides with maintained stability against proteolytic degradation by human leukocyte elastase, as well as staphylococcal aureolysin and V8 proteinase. The biological relevance of these findings was demonstrated ex vivo for pig skin infected by S. aureus and E. coli. CONCLUSIONS/SIGNIFICANCE: End-tagging by hydrophobic amino acid stretches may be employed to enhance bactericidal potency also of ultra-short AMPs at maintained limited toxicity. The approach is of general applicability, and facilitates straightforward synthesis of hydrophobically modified AMPs without the need for post-peptide synthesis modifications

Interaction Between Antimicrobial Peptides and Phospholipid Membranes : Effects of Peptide Length and Composition

Due to increasing problems with bacterial resistance development, there is a growing need for identifying new types of antibiotics. Antimicrobial peptides constitute an interesting group of substances for this purpose, since they are believed to act mainly by disrupting the bacterial membrane, which is a fast and non-specific mechanism. In order to understand the details on this action simplified phospholipid model membranes based on liposomes, monolayers and bilayers, were employed in this thesis. By in situ ellipsometry studies on supported lipid bilayers in combination with leakage from liposomes it was found that peptide-induced membrane rupture to a great extent is related to peptide adsorption. The peptide activity and mechanism of action is highly dependent on peptide properties such as length, topology, charge, and hydrophobicity. Electrostatic interactions are crucial for peptide adsorption, whereas α-helix formation is of less importance, demonstrated by the dominating peptide conformation being random coil both in absence and presence of membranes, as investigated by circular dichroism. Comparable effects were observed in both mono- and bilayer systems, showing that formation of transmembrane structures is no prerequisite for membrane rupture by complement-derived peptides. Electrochemical studies on these peptides further demonstrated that hydrophobic interactions facilitate peptide penetration into the membrane, causing defects in close proximity to the peptides, while strong electrostatic interactions arrest the peptide in the headgroup region. Increasing the peptide hydrophobicity, by e.g., tryptophan end-tagging, also increases salt resistance. Good correlations were found between model membrane investigations and antibacterial activity towards both Gram-negative and Gram-positive bacteria, showing that membrane rupture is a key mechanism of action for the peptides investigated. In addition, for all peptides investigated cell toxicity is low

Interaction Between Antimicrobial Peptides and Phospholipid Membranes : Effects of Peptide Length and Composition

Due to increasing problems with bacterial resistance development, there is a growing need for identifying new types of antibiotics. Antimicrobial peptides constitute an interesting group of substances for this purpose, since they are believed to act mainly by disrupting the bacterial membrane, which is a fast and non-specific mechanism. In order to understand the details on this action simplified phospholipid model membranes based on liposomes, monolayers and bilayers, were employed in this thesis. By in situ ellipsometry studies on supported lipid bilayers in combination with leakage from liposomes it was found that peptide-induced membrane rupture to a great extent is related to peptide adsorption. The peptide activity and mechanism of action is highly dependent on peptide properties such as length, topology, charge, and hydrophobicity. Electrostatic interactions are crucial for peptide adsorption, whereas α-helix formation is of less importance, demonstrated by the dominating peptide conformation being random coil both in absence and presence of membranes, as investigated by circular dichroism. Comparable effects were observed in both mono- and bilayer systems, showing that formation of transmembrane structures is no prerequisite for membrane rupture by complement-derived peptides. Electrochemical studies on these peptides further demonstrated that hydrophobic interactions facilitate peptide penetration into the membrane, causing defects in close proximity to the peptides, while strong electrostatic interactions arrest the peptide in the headgroup region. Increasing the peptide hydrophobicity, by e.g., tryptophan end-tagging, also increases salt resistance. Good correlations were found between model membrane investigations and antibacterial activity towards both Gram-negative and Gram-positive bacteria, showing that membrane rupture is a key mechanism of action for the peptides investigated. In addition, for all peptides investigated cell toxicity is low

Interaction between amphiphilic peptides and phospholipid membranes

This brief review aims at providing some illustrative examples on the interaction between amphiphilic peptides and phospholipid membranes an area of significant current interest Focusing on antimicrobial peptides factors affecting peptide-membrane interactions are addressed including effects of peptide length charge hydrophobicity secondary structure and topology Effects of membrane composition are also illustrated including effects of membrane charge nature of the polar headgroup and presence of cholesterol and other sterols Throughout novel insights on the importance of peptide adsorption density on membrane stability are emphasized as is the correlation between peptide adsorption peptide induced leakage in model liposome systems peptide-induced lysis of bacteria and bacteria killing (C) 2010 Elsevier Ltd All rights reserve

Effects of single amino acid substitutions on peptide interaction with lipid membranes and bacteria-variants of GKE21, an internal sequence from human LL-37

Effects of helix destabilization on lipid membrane interaction, liposome rupture, and bacterial killing was investigated for variants of the antimicrobial peptide GKE21 (GKEFKRIVQRIKDFLRNLVPR), an internal sequence of human cathelicidin LL-37, by ellipsometry, circular dichroism, fluorescence spectroscopy, and bacterial radial diffusion assay. GKE21 displayed moderate helix induction in buffer, which increased on interaction with phospholipid membranes. Substituting either of the two valines (V) in GKE21 with either proline (P) or D-valine (dV) resulted in helix destabilization, while peptide isoelectric point, net charge at pH 7.4, and mean hydrophobicity remained unchanged. The decreased tendency for helix formation in GKE21 (V -> P, V -> dV) resulted in a lower induced (helix-related) amphiphilicity, and correlated to a lower peptide adsorption at supported phospholipid membranes, as well as to decreased peptide-induced liposome leakage, particularly at high electrolyte concentration where conformation-invariant electrostatic interactions are screened. In addition, bacterial killing was reduced for the substituted peptides, indicating that even minor changes in induced peptide amphiphilicity may be of relevance for the bactericidal properties of this type of antimicrobial peptides. (C) 2009 Elsevier B.V. All rights reserved

Effects of topology, length, and charge on the activity of a kininogen-derived peptide on lipid membranes and bacteria

Effects of topology, length, and charge on peptide interactions with lipid bilayers was investigated for variants of the human kininogen-derived peptide HKH20 (HKHGHGHGKHKNKGKKNGKH) by ellipsometry, CD, fluorescence spectroscopy, and z-potential measurements. The peptides display primarily random coil conformation in buffer and at lipid bilayers, and their lipid interaction is dominated by electrostatics, the latter evidenced by higher peptide adsorption and resulting membrane rupture for an anionic than for a zwitterionic membrane, as well as by strongly reduced adsorption and membrane rupture at high ionic strength. At sufficiently high peptide charge density, however, electrostatic interactions contribute to reducing the peptide adsorption and membrane defect formation. Truncating HKE20 into overlapping 10 amino acid peptides resulted in essentially eliminated membrane rupture and in a reduced amount peptide charges pinned at the lipid bilayer. Finally, cyclic HKH20 was found to be less efficient than the linear peptide in causing liposome rupture, partly due to a lower adsorption. Analogous results were found regarding bactericidal effects

Antimicrobial peptides : An emerging category of therapeutic agents

Antimicrobial peptides (AMPs), also known as host defense peptides, are short and generally positively charged peptides found in a wide variety of life forms from microorganisms to humans. Most AMPs have the ability to kill microbial pathogens directly, whereas others act indirectly by modulating the host defense systems. Against a background of rapidly increasing resistance development to conventional antibiotics all over the world, efforts to bring AMPs into clinical use are accelerating. Several AMPs are currently being evaluated in clinical trials as novel anti-infectives, but also as new pharmacological agents to modulate the immune response, promote wound healing, and prevent post-surgical adhesions. In this review, we provide an overview of the biological role, classification, and mode of action of AMPs, discuss the opportunities and challenges to develop these peptides for clinical applications, and review the innovative formulation strategies for application of AMPs.Published 27 December</p

Feeling fine - the effect of topography and friction on perceived roughness and slipperiness

(1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the surfaces of the materials and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials of different elastic modulus and 8 different wrinkle wavelengths were characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100. μm and roughness above 100. μm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) reference surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction component.Export Date: 23 August 2017; Article in Press</p