Dipalmitoylphosphatidylcholine Liposomes Research Articles

Structure, Self-Assembly, and Phase Behavior of Neuroactive N-Acyl GABAs: Doxorubicin Encapsulation in NPGABA/DPPC Liposomes and Release Studies.

N-Acylated amino acids and neurotransmitters in mammals exert significant biological effects on the nervous system, immune responses, and vasculature. N-Acyl derivatives of γ-aminobutyric acid (N-acyl GABA), which belong to both classes mentioned above, are prominent among them. In this work, a homologous series of N-acyl GABAs bearing saturated N-acyl chains (C8-C18) have been synthesized and characterized with respect to self-assembly, thermotropic phase behavior, and supramolecular organization. Differential scanning calorimetric studies revealed that the transition enthalpies and entropies of N-acyl GABAs are linearly dependent on the acyl chain length. The crystal structure of N-tridecanoyl GABA showed that the molecules are packed in bilayers with the acyl chains aligned parallel to the bilayer normal and that the carboxyl groups from opposite layers associate to form dimeric structures involving strong O-H···O hydrogen bonds. In addition, N-H···O and C-H···O hydrogen bonds between amide moieties of adjacent molecules within each layer stabilize the molecular packing. Powder X-ray diffraction studies showed odd-even alternation in the d spacings, suggesting that the odd chain and even chain compounds pack differently. Equimolar mixtures of N-palmitoyl GABA and dipalmitoylphosphatidylcholine (DPPC) were found to form stable unilamellar vesicles with diameters of ∼300-340 nm, which could encapsulate doxorubicin, an anticancer drug, with higher efficiency and better release characteristics than DPPC liposomes at physiologically relevant pH. These liposomes exhibit faster release of doxorubicin at acidic pH (<7.0), indicating their potential utility as drug carriers in cancer chemotherapy.

Effect of liposomal complexes of quercetin-rich flavonoids from French Marigold (Tagetes patula L.) on Jurkat cell viability

Background: Natural polyphenols are naturally used in traditional medicine to treat various diseases. Despite their healthful properties, ingesting phenolic compounds in food form does not provide a sufficient concentration for systemic therapeutic effects due to their low solubility in water, poor absorption, and fast metabolism. This problem has been solved by creating various composite pharmaceuticals from phenolic compounds using different methods to stabilize polyphenols. Objective: The purpose of this study was to assess the effects of the DPPA (1,2-palmitoyl phosphatidic acid) and DPPC (dipalmitoyl phosphatidylcholine) liposomes on the protective effects of a quercetin-rich flavonoid fraction extracted from French Marigold (Tagetes patula L.) on the viability of Jurkat cells. The study will examine both intact cells and cells that have been incubated under oxidative stress conditions. Materials and Methods: Quercetin-rich flavonoid fraction was extracted from a French Marigold (Tagetes patula L.) by thin-layer chromatography (TLC), High-pressure liquid chromatography (HPLC), and Liquid Chromatography-Mass Spectrometry (LC-MS) methods. Extract alone and in complex with dipalmitoyl phosphatidylcholine (DPPC) and 1,2- dipalmitoyl phosphatidic acid (DPPA) liposomes were added to the Jurkat cells culture at a rate of 2 mg/mL−1.The 3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide (MTT) test assayed Cell viability by evaluating cellular dehydrogenase activity. Results: Flavonoids were separated and identified in the marigold extracts by TLC, HPLC, and LC-MS methods. The spectrophotometric absorption spectrum of the quercetin-rich flavonoid fraction extracted from French Marigold (Tagetes patula L.) shows two peaks corresponding to benzoyl (254nm) and cinnamyl (375nm) aromatic rings. In the complex of quercetin-rich flavonoid fraction with DPPC and DPPA liposomes, the spectrophotometric absorption peak at 254nm was not detected, while the absorption intensity of the peak at 375nm was sharply reduced. The quercetin-rich flavonoid fraction alone and in combination with DPPC liposome increased intact and incubated under low- and high-intensity oxidative stress conditions Jurkat cells’ viability but did not reveal effect in combination with DPPA liposome. Conclusions: The quercetin-rich flavonoid fraction extracted from French Marigold (Tagetes patula L.) forms stable complexes with DPPC and DPPA liposomes that allow the storage of high content of phenolic compounds in lipid nanocapsules. The use of the liposomal system in the pharmaceutical and food industry allows for carried and controlled bioactive-compound release, which is considered one of the main strategies to improve and enhance the quality of food, providing preventative healthcare for the population and decreasing the risk of disease. Keywords: bioactive-compound, polyphenols, Quercetin, Liposomes, Jurkat cells, therapeutic effects, pharmaceuticals

Organization of Carotenoid Aggregates in Membranes Studied Selectively using Resonance Raman Optical Activity.

In living organisms, carotenoids are incorporated in biomembranes, remarkably modulating their mechanical characteristics, fluidity, and permeability. Significant resonance enhancement of Raman optical activity (ROA) signals of carotenoid chiral aggregates makes resonance ROA (RROA), a highly selective tool to study exclusively carotenoid assemblies in model membranes. Hence, RROA is combined with electronic circular dichroism (ECD), dynamic light scattering (DLS), molecular dynamics, and quantum-chemical calculations to shed new light on the carotenoid aggregation in dipalmitoylphosphatidylcholine (DPPC) liposomes. Using representative members of the carotenoid family: apolar α-carotene and more polar fucoxanthin and zeaxanthin, the authors demonstrate that the stability of carotenoid aggregates is directly linked with their orientation in membranes and the monomer structures inside the assemblies. In particular, polyene chain distortion of α-carotene molecules is an important feature of J-aggregates that show increased orientational freedom and stability inside liposomes compared to H-assemblies of more polar xanthophylls. In light of these results, RROA emerges as a new tool to study active compounds and drugs embedded in membranes.

Multifunctional antibiotic hydrogel doped with antioxidative lycopene-based liposome for accelerative diabetic wound healing

In the daily management of infected diabetic wound, antibiotics resistance derived from broad-spectrum antimicrobe is still inevitable. Together with the complicated inflammatory environment induced by hyperglycemia and bacteria colonization, it’s urgent to develop a novel bioactive ingredient integrating both anti-oxidative and modulation on inflammatory environment to be combined with disinfection. In regard of this, lycopene (LYC), an abundant, natural and unsaturated alkene carotenoid extracted from tomatoes was intercalated into the Dipalmitoyl-phosphatidylcholine (DPPC) liposomes loading with tobramycin (TOB), and further formulated with HAMA hydrogel (LT NPs@Gel) to prepare a novel multifunctional antibiotic wound dressing. The in vitro study showed that the intercalation of LYC and the loaded TOB brought LT NPs antioxidative and antibacterial properties, thus effectively inhibit the proliferation of bacteria and relieve endoplasmic reticulum (ER) stress to promote cell migration and angiogenesis. In an infected diabetic wound model on rat, the local administration of LT NPs@Gel significantly promoted wound healing within 14 days. Owing to the synchronized management on the inflammation environment and bacteria colonization, the massive oxidative stress in the wound were significantly alleviated, followed by the distinctive promotion of angiogenesis, re-epithelization, and collagen deposition. We believe that this functional hybrid HAMA hydrogel formulated with novel LYC-intercalated antibiotic liposome can achieve the multi-dimensional management of infected diabetic wounds.

Resveratrol-Loaded Dipalmitoylphosphatidylcholine Liposomal Large Porous Microparticle Inhalations for the Treatment of Bacterial Pneumonia Caused by Acinetobacter baumannii.

Background: Acinetobacter baumannii-mediated bacterial pneumonia is a common disease that is harmful to human health. Dipalmitoylphosphatidylcholine (DPPC) is the major lipid component of the pulmonary surfactant (PS) found in the alveolar space; the PS helps to keep surface tension low, which allows for improved oxygen delivery. Resveratrol (RE) is a phytoalexin found in plants that is released in response to injury or infection. The therapeutic effect of Re is limited due to its low solubility and bioavailability. In this study, we report pulmonary delivery of Re-loaded DPPC liposomal large porous microparticles (RDLPMs) for treatment of A. baumannii-induced pneumonia. Methods: Novel RDLPMs were prepared by rotary evaporation and a freeze-drying method in this study. RDLPMs were evaluated by the particle size, electric potential, in vitro release, and particle size distribution. A rat model of A. baumannii-mediated pneumonia was established and used for pharmacodynamic evaluations. Results: The Re-loaded DPPC liposomes (RDLs) consisted of Re/DPPC (1:3, mol/mol) and DPPC/cholesterol (3:1, w/w), with a hydration time of 15 minutes. The RDLs had a high encapsulation efficiency of 69.8% ± 1.6%, a mean size of 191.5 ± 4.5 nm, and a high zeta potential of 12.4 ± 1.5 mV. The RDLPMs were composed of mannitol/large porous microparticles/RDLs (1:4:2, w/w/w) and had a loading efficiency of 2.20% ± 0.24%. The RDLPMs had an aerodynamic diameter (2.73 ± 0.65 μm), a good fluidity (28.30° ± 6.13°), and demonstrated high lung deposition (fine particle fraction = 43.33%). Surprisingly, while penicillin showed better microbial inhibition than the RDLPMs and Re groups in vitro, the RDLPMs were more effective in vivo. Conclusion: The RDLPMs showed good powder properties for pulmonary delivery. The RDLPMs may inhibit the nuclear factor kappa-B pathway and downregulate the expression of cytokines downstream of tumor necrosis factor-α and interleukin-1β. As well as, RDLPMs demonstrated some antibacterial properties against A. baumannii bacteria. Re, when delivered in RDLPMs as a dry powder inhaler, is a promising substitute for antibiotics in the treatment of A. baumannii pneumonia.

Drug–Membrane Interaction as Revealed by Spectroscopic Methods: The Role of Drug Structure in the Example of Rifampicin, Levofloxacin and Rapamycin

We have investigated the nature of the interaction of small organic drug molecules with lipid membranes of various compositions. Using infrared spectroscopy and differential scanning calorimetry methods, we studied the role of the structure of the active molecule in interaction with the membrane using the example of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylcholine:cardiolipin (DPPC:CL) liposomes. We discovered the key role of the heterocycle in interaction with the polar part of the bilayer and the network of unsaturated bonds in interaction with the hydrophobic part. For rifampicin and levofloxacin, the main binding sites were phosphate and carbonyl groups of lipids, and in the case of anionic liposomes we found a slight penetration of rifampicin into the hydrophobic part of the bilayer. For rapamycin, experimental confirmation of the localization of the molecule in the region of fatty acid chains was obtained, and perturbation in the region of phosphate groups was demonstrated for the first time. The process of phase transition of liposomal forms of rifampicin and levofloxacin was studied. DPPC liposomes accelerate the phase transition when loaded with a drug. DPPC:CL liposomes are less susceptible to changes in the phase transition rate.

Structural dynamics of chlorpromazine (CPZ) drug with dipalmitoylphosphatidylcholine (DPPC) lipid: a potential drug for SARS-CoV-2

There is an urgent requirement for drug discovery and more importantly drug repositioning due to infectious new Severe Acute Respiratory Syndrome coronavirus 2. As per the recent report published in the journal L'Encéphale in May 2020, there is a planned ReCoVery Study examining the repurposing the chlorpromazine for the treatment of COVID-19. Here, we apply a combined Raman microspectroscopy and DFT-MD approach to investigate the structural dynamics of the Chlorpromazine (CPZ) drug with dipalmitoylphosphatidylcholine (DPPC) lipid bilayer, identifying the specific position of the drug in the DPPC lipid bilayer. The intensity ratios of the Raman peaks I 2935/I 2880, I 1097/I 1064 and I 1097/I 1129 are representative of the interaction of drugs with lipid alkyl chains and furnish conformation of lipid alkyl chains. Raman imaging microscopy for the study of the distribution of CPZ inside the lipid vesicles is reported. We also investigated the influence of order and disorder ratio in the CPZ on the DPPC liposomes prepared on phase transition temperature. HIGHLIGHTS Drug–membrane interactions using micromolar concentrations of both lipid and drugs. Neuroleptic drug and DPPC vesicles composed of DPPC/drug mixtures reveal qualitative differences between the Raman spectra The temperature-controlled Raman microspectroscopic study has demonstrated that below phase-transition temperature, the fatty acid chains of the phospholipids are stiff and packed in a highly ordered array. DFT and MD simulations to understand molecular interactions, structural dynamics, and Raman spectra. Above phase-transition temperature, the chains are disordered and possess more motional freedom. Communicated by Ramaswamy H. Sarma

On the structure and stability of novel cationic DPPC liposomes doped with gemini surfactants

A novel formulation of cationic liposomes was studied by mixing dipalmitoylphosphatidylcholine (DPPC) with tetradecyltrimethylammonium bromide gemini surfactants with different alkane spacer groups lengths attached to their ammonium head-groups. The physicochemical characterization of the cationic liposomes was obtained by combining experimental results from differential scanning microcalorimetry (DSC) with molecular dynamic simulations, in order to understand their structural configuration. An adapted Ising model was used to interpret the results in terms of cooperativity of the phase transitions.The gemini surfactants partition into the lipid bilayer of DPPC liposomes, and the induced changes in colloidal stability and phase transition were analyzed in detail. The DPPC liposomes became positively charged upon gemini surfactant partition, showing increased colloidal stability. Our results show significant differences in structural configuration between gemini surfactants with short and long spacer lengths. While gemini with shorter spacers allocate within the lipid bilayer with both headgroups in the same layer, geminis with longer spacers unexpectedly intercalate in the lipid membrane in a particular zig-zag configuration, with each headgroup located at a different side of the bilayer, altering the coupling degree parameters of the membrane’s phase transition.The extraordinary increase of colloidal stability of DPPC liposomes with gemini surfactants at very low molar ratio and the possibility to tune the physicochemical properties of the membrane by control de spacer length of the geminis opens new possibilities for cationic liposomal formulations with potential applications in vaccines, drug/gene delivery or biosensing.

Divergent effects of cholesterol on the structure and fluidity of liposome and catanionic vesicle membranes.

Lipid-like ion-pair amphiphile vesicles, or catanionic vesicles, have emerged as potential drug carriers. The effects of cholesterol on the properties of catanionic vesicles have yet been systematically studied. Here, we compared the effects of cholesterol on the structures and fluidities of dipalmitoylphosphatidylcholine liposomes and catanionic vesicles with similar main transition temperatures (Tm ). For liposomes, fluorescence anisotropy (FA) thermograms reveal typical condensing and disordering effects of cholesterol above and below Tm respectively. In contrast, FA and molecular simulation data reveal that catanionic bilayers below Tm are more fluidic due to shorter alkyl chains. This leads to only condensing effects of cholesterol for catanionic vesicles at all temperatures. Our results provide important insights into the fabrication of catanionic vesicles as novel drug carriers.

Liposomal Formulation for Oral Delivery of Cyclosporine A: Usefulness as a Semisolid-Dispersion System.

This study aims to understand the process and mechanism of oral drug absorption from liposomes and to verify the usefulness of liposomal formulation for poorly soluble drugs. Cyclosporine A (CsA) was used as a model drug and entrapped into Dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) liposomes. Molecular state of CsA in the liposomes was analyzed using powder X-ray diffraction (PXRD) and polarized light microscopy (PLM). Release profiles of CsA from liposomes were observed in fasted state simulated intestinal fluid (FaSSIF). Oral absorption of CsA from liposomal formulations were investigated in rats. PXRD and PLM analyses suggested that CsA exists in the lipid layer of liposomes as a molecular dispersed state. Although both liposomes retained CsA stably in the simple buffer, DPPC liposomes quickly released CsA within 10min in FaSSIF due to the interaction with bile acid. In contrast, effect of bile acid was negligible in DSPC, indicating a high resistivity to membrane perturbation. Oral bioavailability of CsA from liposomal formulations were almost comparable with that from a marketed product (Neoral). However, the absorption profiles were clearly different. CsA was absorbed quickly from DPPC liposomes and Neoral, while sustained absorption profile was observed from DSPC liposomes. Further study in which ritonavir was co-entrapped in the liposomes with CsA showed the higher efficacy of ritonavir to increase oral bioavailability of CsA. Liposomes allows the appropriate formulation design for oral delivery of poorly soluble drugs, not only to increase the extent but also to control the rate of absorption.

The effects of miltefosine on the structure and dynamics of DPPC and DPPS liposomes mimicking normal and cancer cell membranes: FTIR and DSC studies

Miltefosine (MLT,hexadecylphosphocholine (HePC)) is an alkylphospholipid (APL) clinically used against leishmaniasis and the topical treatment of cancer. Although the MLT mechanism of action has not yet been clarified, it is thought to be related to its incorporation into the plasma membrane, affecting lipid homeostasis. An essential feature of APLs is that they possess a lethal effect that acts only on malignant cells without affecting normal cells; this property indicates the potential selective antitumor properties of these types of drugs. However, the exact mechanism of APLs action at the molecular level is not yet known in detail. This study aimed to elucidate the molecular mechanisms of the interaction of the antitumor alkylphospholipid drug miltefosine with molecular models of normal and cancer cell membranes. The interaction of MLT with dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposomes (MLVs) mimicking normal cell membrane and dipalmitoyl phosphatidylserine (DPPS) multilamellar liposomes (MLVs) mimicking cancer cell membrane was studied in the presence of (1 mol%,3 mol%, 6 mol%, 9 mol%, 15 mol%, 24 mol%, 30 mol% and 35 mol%) and in the absence of MLT by using two different non-invasive techniques; Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). The comparative results show that miltefosine affects DPPS/MLT systems modeled cancer cells more than the DPPC/MLT system modeled healthy cells. Our results may be proof at the molecular level that miltefosine has selective antitumor properties.

Liposomes as nonspecific nanocarriers for 5-Fluorouracil in the presence of cyclodextrins

5-Fluorouracil (5-FU) is one of anticancer drugs with broad activity. Due to its severe side effects, recent studies concentrate on new ways of directed 5-FU delivery and its release in ill tissue. One of selective carriers could be cyclodextrins and liposomes. The combination of novel methods, leading to formation of inclusion complexes (IC) between host molecule of β-cyclodextrin (β-CD) or 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and 5-FU guest and its subsequent encapsulation in dipalmitoylphosphatidylcholine (DPPC) liposomes is studied experimentally in the present work. Several methods are applied to proof the encapsulation of the analysed drug and its release over time at 37 and 41 °C. The 5-FU release from complex of liposomal form of 5-fluorouracil and β-cyclodextrin (L[DPPC/5-FU]:β-CD) and complex of liposomal form of 5-fluorouracil and (2-hydroxypropyl)-β-cyclodextrin (L[DPPC/5-FU]:HP-β-CD) was followed using UV–Vis and fluorescence spectroscopy, proton nuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC) techniques. The electronic and NMR spectra analysis were additionally supported by molecular modeling, including prediction of spectral changes in vacuum and in water using density functional theory (DFT-B3LYP-D3). From the observed changes the fastest release from liposomes (within 1 h) was observed for the 5-FU complexes with HP-β-cyclodextrin at 41 °C.

Therapeutic hydrogel sheets programmed with multistage drug delivery for effective treatment of corneal abrasion

Corneal abrasion (CA) is a leading cause of inflammation, scar formation, and even loss of vision in the eye if allowed to progress; however, current treatments remain constrained by complex and sequential conditions that impede access to most therapies for progressively abraded corneas. Herein, an advanced therapeutic hydrogel sheet (THS) constructed via electrostatic assembly of a functional hydrogel and a ternary drug-carrier system is reported. Specifically, the functional hydrogel comprises a poly(hydroxyethyl methacrylate), a positively charged chitosan, and zinc oxide nanoparticles. The ternary drug-carrier system is composed of dipalmitoylphosphatidylcholine liposome (DPPC) nanoparticles containing epigallocatechin gallate (EGCG) and hyaluronic acid nanoparticles with low and high crosslinking degrees, which separately carrying β-1,3-glucan and SB431542. Owing to the tailored degradability of the ternary system, the THS is able to provide multistage drug release, consequently allowing successive drug administration onto an ocular surface afflicted with CA for the suppression of inflammatory response in the early stage (by the fastest released EGCG) of corneal tissue repair, followed by promotion of wound healing in the middle stage (the moderately fast released β-1,3-glucan) and prevention of scar formation in the final stage (by the slowest released SB431542). In a rabbit model of CA, the THS has a significant treatment efficacy for repairing injured cornea tissues and demonstrates a percent recovery of greater than 90%, which represents a more than eight-fold improvement compared to conventional eye drops. The therapeutic hydrogel material demonstrated here can adapt to a variety of drug molecules, opening up a new avenue for the treatment of complex ocular diseases.

The Interaction of Baicalein with Dipalmitoylphosphatidylcholine Liposomes: Differential Scanning Calorimetry, Synchrotron X-ray Diffraction, and Fourier Transform Infrared Studies

Baicalein is an important flavonoid compound extracted from the roots of Scutellaria baicalensis. The interaction between baicalein and DPPC liposomes has been studied by differential scanning calorimetry, synchrotron X-ray diffraction and Fourier transform infrared spectroscopy. The results showed the phase states of liposomes change under the disturbance of baicalein. When the molar percentage of baicalein (x) is not more than 5%, the baicalein molecules promote the hydration degree of the head groups. At x=5%, the liposomes undergo a change from Lβ′ to Lβ phase. When x is between 5% and 10%, the liposomes are in Pβ′ phase. When x is more than 10%, the baicalein molecules alter the hydration state of head groups. Meanwhile, the phase states shift from Pβ′ to Pβ. This study is of great significance to further study the interaction between drugs and biomimetic membranes and to further investigate the phase transition mechanisms of DPPC liposome.

Utilizing DPPC Liposomes to Capture Persistent Organic Pollutants

Polychlorinated biphenyls (PCBs) are a class of man-made persistent organic pollutants that saw wide-spread use in commercial and industrial infrastructure as both an insulator and coolant in electrical transformers and capacitors. 2,2’,3,3′,4,4’-hexachlorobiphenyl (HCBP) was one of the most widely produced PCBs. As these mechanical structures failed or are discarded, PCBs are released into the soil, migrate to the water table, and eventually spread to nearby ecosystems by rain and wind. The remarkable chemical stability of PCBs leave few options for environmental waste and water removal, yet they are becoming increasingly concerning as they pose potential health risks to individuals who become exposed to them. Conventionally, liposomes have been used for their promising drug delivery capabilities. Here, we investigated their potential for the entrapment and removal of HCBP. Liposomes are small, nonpolar lipid bi-layered aggregates capable of capturing a wide variety of both polar and nonpolar compounds. Dipalmitoylphosphatidylcholine (DPPC) is a well-characterized lipid that can be derived from natural sources. It is a phospholipid typically found as a major component of pulmonary surfactant mixtures. To assess the utility of liposomes prepared with pure DPPC in capturing PCBs, they were prepared using probe-tip sonication for both direct and passive incorporation of HCBP. Incorporation was assessed using a combination of differential scanning calorimetry and UV-Vis spectroscopy. For direct incorporation liposome stability generally decreased compared to pure DPPC liposomes based on a corresponding decrease in the phase transition temperature, Tm, from 40.8 °C to 37.4 °C. An analysis of passive incorporation using UV-Vis spectroscopy showed an increase in the incorporation of HCBP proportionate to the length of exposure time up to 24 hours. Together our calorimetry and spectroscopic measurements are indicative of HCBP incorporation into liposomes and shows promising potential for use in sustainable environmental cleanup and water treatment technologies. Future studies aim to further explore their technological capabilities by optimizing their thermal and mechanical stability.

Investigating DPPC Liposomes and Their Capacity to Assimilate 2,2’,3,3’,4,4’-Hexachlorobiphenyl, an Emerging Environmental Pollutant

Persistent organic pollutants (POPs) are organic compounds that bioaccumulate in a wide variety of biological and ecological environments due to their resistive nature to chemical, thermal and photodegradation. The stability of POPs and specifically PCBs (a subclass of POPs) leave few options for environmental waste and water removal. Conventionally, liposomes have been used for their drug delivery capabilities, but here we investigated their potential for the entrapment and removal of this class of emerging environmental pollutants. Liposomes are small, nonpolar lipid bi-layered aggregates capable of capturing a wide variety of both polar and nonpolar compounds. Dipalmitoylphosphatidylcholine (DPPC)is a well-characterized lipid that can be derived from natural sources. It is a phospholipid typically found as a major component of pulmonary surfactant mixtures. To assess the utility of liposomes prepared with pure DPPC in capturing PCBs, they were prepared using probe-tip sonication for both direct and passive incorporation of a representative PCB compound, 2,2’,3,3’,4,4’-hexachlorobiphenyl (HCBP). Incorporation of HCBP was assessed using a combination of differential scanning calorimetry and UV-Vis spectroscopy. For direct incorporation in the presence of HCBP, it was apparent that liposome stability generally decreased compared to pure DPPC liposomes based on a corresponding decrease in the phase transition temperature, Tm, from 40.8 °C to 37.4 °C. Additionally, an analysis of passive incorporation by UV-Vis spectroscopy showed an increase in the incorporation of HCBP proportionate to the length of exposure time up to 24 hours. Both the decrease in Tm and substantial UV absorbance signal produced after the compound was extracted from DPPC liposomes are indicative of its incorporation and demonstrates the potential for the use of liposomes in sustainable environmental cleanup and water treatment technologies.

Cholecalciferol has strong effect on the order and dynamics of DPPC membranes: A combined Fourier transform infrared spectroscopy and differential scanning calorimetry study

The effect of cholecalciferol on dipalmitoyl phosphatidylcholine (DPPC) multilamellar vesicles (MLVs) as a function of temperature and cholecalciferol concentration (1–40 mol%) was studied by using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The investigation of the CH, C = O, and PO2− antisymmetric double stretching modes in FTIR spectra and DSC studies reveal that addition of cholecalciferol into pure DPPC liposomes shifts the phase transition to lower temperature, disorders and increases the dynamics of the acyl chains in both phases and induces hydrogen bond formation in the interfacial region.

Lamellarity and size distributions in mixed DPPC/amphiphilic poly(2-oxazoline) gradient copolymer vesicles and their temperature response

Mixed liposomes of dipalmitoylphosphatidylcholine (DPPC) and gradient (pseudodiblock) poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) copolymers are investigated by small angle neutron scattering (SANS). All experimental data, from different phospholipid-copolymer compositions, concentrations and temperatures are fitted with one model. This model allows the determination of the separate contributions from vesicular populations of different lamellarity and size. MPOx copolymers are proved to modify both the size and lamellarity of DPPC liposomes. The gradient copolymer with higher hydrophilic content induces shrinkage of the uni- and bi-lamellar DPPC vesicles. The copolymer with lower hydrophilic content causes dramatic changes on the lamellarity of DPPC vesicles by the formation of hexa-lamellar vesicles. The tendency of multi-lamellar vesicles to transform into uni-lamellar ones as temperature increases is more pronounced in the presence of the copolymers. These findings may have direct implications on the drug loading and release properties of liposomes and their interactions with cells.

Interaction of synthetic antimicrobial peptides of the Hylin a1 family with models of eukaryotic structures: Zwitterionic membranes and DNA

Antimicrobial peptides (AMPs) have been appointed as a possible alternative to traditional antibiotics in face of pathogens increasing resistance to conventional drugs. Hylin a1 (IFGAILPLALGALKNLIK), an AMP extracted from the skin secretion of a South American frog, Hypsiboas albopunctatus, was found to show a strong cytotoxicity against bacteria and fungus, but also a considerable hemolytic action. Considering the toxicity of the peptide in eukaryotic cells, this work focuses on investigating the effects of the interaction of the Hylin a1 analogues W6Hya1, D0W6Hya1 and K0W6Hya1 with models of eukaryotic structures, namely zwitterionic liposomes of dipalmitoyl phosphatidylcholine (DPPC) and calf-thymus DNA (CT DNA). Through intrinsic Trp fluorescence we determined that the peptide affinity for fluid DPPC bilayers follows the decreasing order: D0W6Hya1 (+2) > W6Hya1 (+3) » K0W6Hya1 (+4). Fluorescence data also indicate that the Trp residue in the more positively charged peptide, K0W6Hya1, is less deep in the bilayer than the residue in the other two peptides. This finding is supported by differential scanning calorimetry (DSC) data, which shows that both D0W6Hya1 and W6Hya1 disturb DPPC gel-fluid transition slightly more effectively than K0W6Hya1. DPPC DSC profiles are homogeneously disturbed by the three peptides, probably related to peptide-membrane diffusion. Surprisingly, the peptide that displays the lowest affinity for PC membranes and is located at the more superficial position in the bilayer, K0W6Hya1, is the most efficient in causing formation of pores on the membrane, as attested by carboxyfluorescein leakage assays. The three peptides were found to interact with CT DNA, with a deep penetration of the Trp residue into hydrophobic pockets of the double helix, as indicated by the significant blue shift on the Trp fluorescence, and the displacement of DNA-bound ethidium bromide by the peptides. The experiments of DNA electrophoresis confirm that Hylin peptides bind DNA in a concentration-dependent manner, inducing complete DNA retardation at the relative AMP/plasmid DNA weight ratio of ~17. These findings could help to better understand the AMPs toxic effects on eukaryotic cells, thus contributing to the design of healthier therapeutic agents.

PEPITEM/Cadherin 15 Axis Inhibits T Lymphocyte Infiltration and Glomerulonephritis in a Mouse Model of Systemic Lupus Erythematosus.

Control of lymphocyte infiltration in kidney is a potential therapeutic strategy for lupus nephritis, considering that control of lymphocyte migration by sphingosine 1 phosphate has been implicated in inflammation-related pathology. The peptide inhibitor of the transendothelial migration (PEPITEM)/cadherin (CDH) 15 axis was recently reported to promote sphingosine 1 phosphate secretion. In this study, we investigated whether CDH15 is expressed in the kidney of MRL/lpr mice and whether lymphocyte infiltration is suppressed by exogenously administered PEPITEM. Mice (18 wk old) were randomized into 4-wk treatment groups that received PEPITEM or PBS encapsulated in dipalmitoylphosphatidylcholine liposomes. Enlargement of the kidney, spleen, and axillary lymph nodes was suppressed by PEPITEM treatment, which also blocked infiltration of double-negative T lymphocytes into the kidney and glomerular IgG/C3 deposition, reduced proteinuria, and increased podocyte density. Immunohistochemical analysis revealed that the PEPITEM receptor CDH15 was expressed on vascular endothelial cells of glomeruli and kidney arterioles, skin, and peritoneum in lupus mice at 22 wk of age but not in 4-wk-old mice. These results suggest that PEPITEM inhibits lymphocyte migration and infiltration into the kidney, thereby preserving the kidney structure and reducing proteinuria. Thus, PEPITEM administration may be considered as a potential therapeutic tool for systemic lupus erythematosus.