A combined FTIR and DSC study on the bilayer-stabilising effect of electrostatic interactions in ion paired lipids

Magnetic Thermosensitive Liposomes Loaded with Doxorubicin

Liposome-mediated anticancer drug delivery has the advantage of limiting the massive cytotoxicity of chemotherapeutic agents. Doxorubicin (DOX) PEG-liposomal does however have a slow-release rate that hinders its therapeutic efficacy. In this study, an integrated therapeutic system based on magnetic thermosensitive liposomes was designed. The chelated gadolinium acquired magnetic properties in the liposomes. The hyperthermia induced by ultra-high-field magnetic resonance imaging (UHF-MRI) enhances the chemotherapeutic effects of DOX. The DOX release from liposomes was facilitated over a narrow range of temperatures owing to the phase transition temperature of the liposomes. The magnetic properties of the liposomes were evident by the elevation of contrast after the exposure to UHF-MRI. Moreover, triple-negative breast cancer (TNBC) cells showed a significant decrease in cellular viability reaching less than 40% viability after 1 h of exposure to UHF-MRI. The liposomes demonstrated a physiological coagulation time and a minimal hemolytic potential in hemocompatibility studies; therefore, they were considered safe for physiological application. As a result, magnetic-thermosensitive liposomal guidance of local delivery of DOX could increase the therapeutic index, thereby reducing the amount of the drug required for systemic administration and the chance of affecting the adjacent tissues.

Interaction mechanism of three egg protein derived ACE inhibitory tri-peptides and DPPC membrane using FS, FTIR, and DSC studies

Understanding the interaction of food derived angiotensin converting enzyme (ACE) inhibitory peptides and intestinal epithelial cell membrane may help to improve their absorption. This research aimed to study the molecular interaction of ACE inhibitory tri-peptides ADF, FGR, and MIR with DPPC membrane during absorption process. The DPPC liposome was prepared and characterized, then used as a model membrane. The permeability of tri-peptides across the membrane was investigated using Fluorescence spectroscopy. The effect of tri-peptides on the structure and dynamics of DPPC bilayers was determined using Fourier transform infrared spectroscopy. The effect of tri-peptides on the phase transition temperature in the DPPC membrane was also analyzed using Differential scanning calorimetry. The results showed that ACE inhibitory tri-peptides ADF, FGR, and MIR can penetrate into both the membrane-water interface and hydrophobic region of DPPC bilayer, and the tri-peptide FGR have higher permeability across the membrane.

Molecular docking of the pentapeptide derived from rice bran protein as anticancer agent inhibiting both receptor and non-receptor tyrosine kinases

The cationic pentapeptide Glu-Gln-Arg-Pro-Arg (EQRPR) belongs to the family of anti-cancer peptides with significant anti-cancer activity. However, the mechanism by which the peptide performs this activity is unknown. In this study, we explored the pharmaceutical profile of Glu-Gln-Arg-Pro-Arg pentapeptide and revealed its anticancer properties by in silico docking studies. Moreover, the effect of EQRPR behavior of the DPPC membrane was investigated by means of Langmuir monolayer technique and the results were discussed in terms of mutual interactions. To evaluate the binding mechanisms, the pentapeptide and its various D-amino acid substituted analogs were docked to both epidermal growth factor receptor (EGFR) tyrosine kinase and proto-oncogene tyrosine-protein kinase, Fyn. Simultaneous binding of the pentapeptides to both EGFR and Fyn proteins, which are receptor- and non-receptor-kinases, respectively, suggest that these peptides can be an effective agent for cancer treatment. Moreover, to show the potential of the investigated pentapeptides to overcome the generated mutation-related drug resistance to EGFR targeted therapies, molecular docking investigations of EQRPR and all its D-analogs were performed against the prospective targets: Wild type EGFR^WT and mutant EGFR^T790M. Erlotinib and TAK-285 were used as reference molecules. The strong interaction of the peptide with EGFR^WT (from -9.24 to -9.75 kcal/mol) and the secondary mutant EGFR^T790M (from -9.28 to -9.64 kcal/mol) observed in most cancer recurrence cases indicates its good potential to overcome drug resistance in cancer therapy. In addition, the pharmacological properties of the investigated pentapeptides were revealed by in silico ADME (Absorption, Distribution, Metabolism, Excretion) and toxicity analysis.Communicated by Ramaswamy H. Sarma.

Effect of Ursolic and Oleanolic Acids on Lipid Membranes: Studies on MRSA and Models of Membranes

Staphylococcus aureus is an opportunistic pathogen and the major causative agent of life-threatening hospital- and community-acquired infections. A combination of antibiotics could be an opportunity to address the widespread emergence of antibiotic-resistant strains, including Methicillin-Resistant S. aureus (MRSA). We here investigated the potential synergy between ampicillin and plant-derived antibiotics (pentacyclic triterpenes, ursolic acid (UA) and oleanolic acid (OA)) towards MRSA (ATCC33591 and COL) and the mechanisms involved. We calculated the Fractional Inhibitory Concentration Index (FICI) and demonstrated synergy. We monitored fluorescence of Bodipy-TR-Cadaverin, propidium iodide and membrane potential-sensitive probe for determining the ability of UA and OA to bind to lipoteichoic acids (LTA), and to induce membrane permeabilization and depolarization, respectively. Both pentacyclic triterpenes were able to bind to LTA and to induce membrane permeabilization and depolarization in a dose-dependent fashion. These effects were not accompanied by significant changes in cellular concentration of pentacyclic triterpenes and/or ampicillin, suggesting an effect mediated through lipid membranes. We therefore focused on membranous effects induced by UA and OA, and we investigated on models of membranes, the role of specific lipids including phosphatidylglycerol and cardiolipin. The effect induced on membrane fluidity, permeability and ability to fuse were studied by determining changes in fluorescence anisotropy of DPH/generalized polarization of Laurdan, calcein release from liposomes, fluorescence dequenching of octadecyl-rhodamine B and liposome-size, respectively. Both UA and OA showed a dose-dependent effect with membrane rigidification, increase of membrane permeabilization and fusion. Except for the effect on membrane fluidity, the effect of UA was consistently higher compared with that obtained with OA, suggesting the role of methyl group position. All together the data demonstrated the potential role of compounds acting on lipid membranes for enhancing the activity of other antibiotics, like ampicillin and inducing synergy. Such combinations offer an opportunity to explore a larger antibiotic chemical space.

Omega-3- and Resveratrol-Loaded Lipid Nanosystems for Potential Use as Topical Formulations in Autoimmune, Inflammatory, and Cancerous Skin Diseases

Resveratrol (RSV) and omega 3 (ω₃), because of their biological favorable properties, have become subjects of interest for researchers in dermocosmetic and pharmaceutical industries; however, these bioactives present technological limitations that hinder their effective delivery to the target skin layer. To overcome the stability and skin permeation limitations of free bioactives, this work proposes a combined strategy involving two different lipid nanosystems (liposomes and lipid nanoparticles) that include ω₃ in their lipid matrix. Additionaly, RSV is only encapsulated in liposomes that provid an adequate amphiphilic environment. Each formulation is thoroughly characterized regarding their physical–chemical properties. Subsequently, the therapeutic performance of the lipid nanosystems is evaluated based on their protective roles against lipid peroxidation, as well as inhibition of cicloxygenase (COX) and nitric oxid (NO) production in the RWA264.7 cell line. Finally, the lipid nanosystems are incorporated in hydrogel to allow their topical administration, then rheology, occlusion, and RSV release–diffusion assays are performed. Lipid nanoparticles provide occlusive effects at the skin surface. Liposomes provide sustained RSV release and their flexibility conferred by edge activator components enhances RSV diffusion, which is required to reach NO production cells and COX cell membrane enzymes. Overall, the inclusion of both lipid nanosystems in the same semisolid base constitutes a promising strategy for autoimmune, inflammatory, and cancerous skin diseases.

Lipid domain formation and non-lamellar structures associated with varied lysylphosphatidylglycerol analogue content in a model Staphylococcal plasma membrane

Dipalmitoyl-3-aza-dehydroxy-lysylphosphatidylglycerol (DP3adLPG), is a chemically stable synthetic analogue of the bacterial lipid lysylphosphatidylglycerol (LPG), designed as a substitute for the notoriously labile native lipid in biophysical investigations. In Staphylococcus aureus, LPG is known to play a role in resistance to antibiotics by altering membrane charge properties in response to environmental stress, but little is known about how LPG influences other bilayer physicochemical properties or lateral organisation, through the formation of complexes with lipids such as phosphatidylglycerol (PG). In this study we have investigated the different phases formed by biomimetic mixtures of 3adLPG and PG in different thermotropic states, using neutron diffraction and electron microscopy. In a DPPG/DP3adLPG 70:30 mol% mixture, two distinct lamellar phases were observed below the lipid melting transition: L_β' 1 and L_β' 2 with respective periodicities of 82 and 62 Å. Increasing the proportion of DP3adLPG to mimic the effects of environmental stress led to the disappearance of the L_β' 1 phase and the formation of an inverse hexagonal phase. The compositions of these different phases were identified by investigating the thermotropic properties of the two mixtures, and probing their interaction with the antimicrobial peptide magainin 2 F5W. We propose that the observed polymorphism results from the preferential formation of either triplet PG-3adLPG-PG, or paired PG-3adLPG complexes, dependent upon the mixing proportions of the two lipids. The relevance of these findings to the role native LPG in S. aureus, are discussed with respect to their influence on antibiotic resistance and lateral membrane organisation.

Magnetic resonance activatable thermosensitive liposomes for controlled doxorubicin delivery

To limit the massive cytotoxicity of chemotherapeutic agents, it is desirable to establish an appropriate subtle blend of formulation design based on a dual-responsive strategy. In this study, a combined therapeutic platform based on magnetic thermosensitive liposomes (Lip_TS-GD) was developed. The incorporation of chelated-gadolinium imparted magnetic properties to thermosensitive liposomes (Lip_TS). The application of an ultra high field magnetic resonance imaging (UHF-MRI) induced hyperthermia, thus provided an improved chemotherapeutic effect of Doxorubicin (DOX). The paramagnetic platform demonstrated thermal sensitivity over a narrow temperature range starting at 37.8 °C, hence the release of DOX from Lip_TS-GD can be well triggered by inducing hyperthermia using UHF-MRI application. The prepared Lip_TS-GD were below 200 nm in diameter and an adequate release of DOX reaching 68% was obtained after 1 h UHF-MRI exposure. Profoundly, triple-negative breast cancer (TNBC) cells that were treated with Lip_TS-GD and subjected thereafter to UHF-MRI exposure for 60 min showed 36% viability. Hemocompatibility studies of Lip_TS-GD showed a physiological coagulation time and minimal hemolytic potential. Conclusively, Lip_TS-GD guided local delivery of DOX to solid tumors will potentially raise the therapeutic index, thus reducing the required dose and frequency of DOX administered systemically without influencing the adjacent tissues.

Rational Development of Liposomal Hydrogels: A Strategy for Topical Vaginal Antiretroviral Drug Delivery in the Context of HIV Prevention

HIV/AIDS stands as a global burden, and vaginal microbicides constitute a promising strategy for topical pre-exposure prophylaxis. Preceding the development of a microbicide containing tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC), in silico and in vitro studies were performed to evaluate the physicochemical characteristics of both drugs, and to study their biophysical impact in lipid model systems. Results from these pre-formulation studies defined hydrogels as adequate vehicles to incorporate TDF-loaded liposomes and FTC. After studying interactions with mucin, zwitterionic liposomes with a mean diameter of 134 ± 13 nm, an encapsulation TDF efficiency of approximately 84%, and a transition temperature of 41 °C were selected. The chosen liposomal formulation was non-cytotoxic to HEC-1-A and CaSki cells, and was able to favor TDF permeation across polysulfone membranes (J_ss = 9.9 μg·cm^-2·h^-1). After the incorporation of TDF-loaded liposomes and FTC in carbomer hydrogels, the drug release profile was sustained over time, reaching around 60% for both drugs within 3-6 h, and best fitting the Weibull model. Moreover, liposomal hydrogels featured pseudoplastic profiles that were deemed suitable for topical application. Overall, the proposed liposomal hydrogels may constitute a promising formulation for the vaginal co-delivery of TDF/FTC.

Alkyl triphenylphosphonium surfactants as nucleic acid carriers: complexation efficacy toward DNA decamers, interaction with lipid bilayers and cytotoxicity studies

Herein, for the first time the complexation ability of a homological series of triphenylphosphonium surfactants (TPPB-n) toward DNA decamers has been explored. Formation of lipoplexes was confirmed by alternative techniques, including dynamic light scattering, indicating the occurrence of nanosized complexes (ca. 100-150 nm), and monitoring the charge neutralization of nucleotide phosphate groups and the fluorescence quenching of dye-intercalator ethidium bromide. The complexation efficacy of TPPB-surfactants toward an oligonucleotide (ONu) is compared with that of reference cationic surfactants. Strong effects of the alkyl chain length and the structure of the head group on the surfactant/ONu interaction are revealed, which probably occur via different mechanisms, with electrostatic and hydrophobic forces or intercalation imbedding involved. Phosphonium surfactants are shown to be capable of disordering lipid bilayers, which is supported by a decrease in the temperature of the main phase transition, T_m. This effect enhances with an increase in the alkyl chain length, indicating the integration of TPPB-n with lipid membranes. This markedly differs from the behavior of typical cationic surfactant cetyltrimethylammonium bromide, which induces an increase in the T_m value. It was demonstrated that the cytotoxicity of TPPB-n in terms of the MTT-test on a human cell line 293T nonmonotonically changes within the homological series, with the highest cytotoxicity exhibited by the dodecyl and tetradecyl homologs.