A Langmuir approach on monolayer interactions to investigate surface active peptides

The Langmuir Blodgett apparatus provides a versatile system for studying the interfacial properties of peptides and peptide-membrane interactions under controlled conditions. Using amphiphilic α-helical peptides to highlight studies undertaken, here we discuss the use of this system to provide information on the surface activity of peptides and describe the insights these studies give into biological functio

A theoretical analysis of secondary structural characteristics of anticancer peptides

Here, cluster analysis showed that a database of 158 peptides formed 21 clusters based on net positive charge, hydrophobicity and amphiphilicity. In general these clusters showed similar median toxicities (p = 0.176) against eukaryotic cell lines and no single combination of these properties was found optimal for efficacy. The database contained 14 peptides, which showed selectivity for tumour cell lines only (ACPCT), 123 peptides with general toxicity to eukaryotic cells (ACPGT) and 21 inactive peptides (ACPI). Hydrophobic arc size analysis showed that there was no significant difference across the datasets. Even though there was no correlation there was no correlation observed, peptides with wide hydrophobic arcs (> 270°) appeared less toxic. Extended hydrophobic moment plot analysis predicted that over 50% of ACPCT and ACPGT peptides would be surface active, which led to the suggestion that amphiphilicity is a key driver of the membrane interactions for these peptides but probably plays a role in their efficacy rather than their selectivity. This analysis also predicted that only 14% of ACPCT peptides compared to 45% of ACPGT peptides were candidates for tilted peptide formation. This implies that those peptides with non-specific activity may have a tendency towards the utilisation of membrane disruptive structures such as tilt peptides which led to the suggestion that the absence of this structure may support cancer cell selectivity. However, these analyses predicted that ACPI peptides, which possess no anticancer activity, would also form surface active and tilted a-helices, clearly showing that other factors are involved in determining the efficacy and selectivity of ACPs

Challenging the Clostridium botulinum toxin type A (BoNT/A) with a selection of microorganisms by culture methods and extended storage of used vials to assess the loss of sterility

In 2002, botulinum toxin type A (BoNT/A) was approved by the US Food and Drug Administration (FDA) for cosmetic use. However, there may be procedural differences between the ways in which a clinician handles, applies and stores the product compared to the suggested guidelines of the manufacturer for handling and storage. To this end vials (N = 12) of BoNT/A were tested for the incidence of microbial contamination followed by challenging the product with a selection of microorganisms by culture methods and by using a calcein release assay to contaminate multi-dose vials at the single concentration used for facial aesthetics. A culture, droplet method was used to count microorganisms challenged with the therapeutic product and to compare viability levels in appropriate controls as well as measuring their lytic properties via an existing cell-free system involving calcein release. Counts of test organisms within the droplets, with the product and the controls without the product were undertaken using Image J software. The result from the incidence of in-vial contamination was inconclusive. Bacterial levels between controls and product challenged groups demonstrated no differences in the growth of viable microorganisms following immediate contact (p = ≥ 0.05). The cell-free calcein release assay demonstrated differences at all time points for low levels of lysis in each case with bacterial lipid extract and were statistically significant (p = 0.011). Although these data appear to correlate with the minimum inhibitory concentration, the additives and vial integrity are also likely to contribute to the maintenance of BoNT/A sterility

The role of C-terminal amidation in the membrane interactions of the anionic antimicrobial peptide, maximin H5

Maximin H5 is an anionic antimicrobial peptide from amphibians, which carries a C-terminal amide moiety, and was found to be moderately haemolytic (20%). The α-helicity of the peptide was 42% in the presence of lipid mimics of erythrocyte membranes and was found able to penetrate (10.8mNm(-1)) and lyse these model membranes (64 %). In contrast, the deaminated peptide exhibited lower levels of haemolysis (12%) and α-helicity (16%) along with a reduced ability to penetrate (7.8mNm(-1)) and lyse (55%) lipid mimics of erythrocyte membranes. Taken with molecular dynamic simulations and theoretical analysis, these data suggest that native maximin H5 primarily exerts its haemolytic action via the formation of an oblique orientated α-helical structure and tilted membrane insertion. However, the C-terminal deamination of maximin H5 induces a loss of tilted α-helical structure, which abolishes the ability of the peptide's N-terminal and C-terminal regions to H-bond and leads to a loss in haemolytic ability. Taken in combination, these observations strongly suggest that the C-terminal amide moiety carried by maximin H5 is required to stabilise the adoption of membrane interactive tilted structure by the peptide. Consistent with previous reports, these data show that the efficacy of interaction and specificity of maximin H5 for membranes can be attenuated by sequence modification and may assist in the development of variants of the peptide with the potential to serve as anti-infective

A Multivalent Approach to Triggerable-Release Cancer Drug Delivery Systems

Cancer continues to be one of the largest health concerns in Canada with approximately 43% of Canadians expected to be diagnosed in their lifetime. However, traditional chemotherapy methods often create complications from nonspecific drug distribution and poor penetration into tumors, providing an inefficient method for suppressing tumor growth and metastasis, and causing indiscriminate harm to healthy cells in the body. The damage that is caused to healthy cells is the root of most destructive and painful side-effects associated with chemotherapy, including nausea, fatigue, hair loss, mouth sores, fertility issues, and organ damage . Nanodiamonds, microscopic diamond particles, have recently gained popularity in medical applications due to their low cost and negligible toxicity. Additionally, their large surface area allows them to be easily modified with biocompatible attachments like polyethylene glycol (PEG) chains and a self-immolative drug linker, which acts as an efficient drug carrier due to its increased loading site. The Trant Team seeks to design and characterize a selective drug delivery system utilizing the pH-sensitive linker property to release the drug in the cancer cell’s acidic environment, reducing harm to not-as-acidic healthy cells. Previous work within the team used nanodiamond single valent carriers in preliminary studies. This presentation will describe multivalent modifications to further increase the loading capacity. Once synthesized and characterized, this drug delivery system is to be tested in vivo on zebrafish to observe its safety and efficacy

Development of a novel, multifunctional, membrane-interactive pyridinium salt with potent anticancer activity

The synthesis and biological evaluation of a novel pyridinium salt is reported. Initial membrane interaction with isolated phospholipid monolayers was obtained with the pyridinium salt, and two neutral analogues for comparison, and the anticancer effects of the best compound established using a cytotoxicity screening assay against glioma cells using both an established cell line and three short-term cell cultures – one of which has been largely resistant to all chemotherapeutic drugs tested to date. The results indicate that the pyridinium salt exhibits potent anticancer activity (EC50s = 9.8-312.5 μM) on all cell types, including the resistant one, for a continuous treatment of 72 hours. Microscopic examination of the treated cells using a trypan blue exclusion assay showed membrane lysis had occurred. Therefore, this letter highlights the potential for a new class of pyridinium salt to be developed as a much needed alternative treatment for glioma chemotherapy

Biophysical investigation into the antibacterial action of modelin-5-NH2

Modelin-5-CONH2 (M5-NH2) is a synthetic antimicrobial peptide, which was found to show potent activity against Bacillus subtilis (Minimum lethal concentration = 8.47 µM) and to bind strongly to membranes of the organism (Kd = 10.44 µM). The peptide adopted high levels of amphiphilic α-helical structure in the presence of these membranes (> 50 %), which led to high levels of insertion (Δπ ≥ 8.0 mN m-1). M5-NH2 showed high affinity for anionic lipid (Kd = 7.46 µM) and zwitterionic lipid (Kd = 14.7 µM), which drove insertion into membranes formed from these lipids (Δπ = 11.5 and 3.5 mN m-1, respectively). Neutron diffraction studies showed that M5-NH2 inserted into B. subtilis membranes with its N-terminal residue, L16, located 5.5 Å from the membrane centre, in the acyl chain region of these membranes, and promoted a reduction in membrane thickness of circa 1.8 Å or 5 % of membrane width. Insertion into B. subtilis membranes by the peptide also promoted other effects associated with membrane thinning, including increases in membrane surface area (Cs-1 decreases) and fluidity (ΔGmix > 0 to ΔGmix 55%), and it is speculated that the antibacterial action of the peptide may involve the toroidal pore, carpet or tilted-type mechanism of membrane permeabilization