Thermodynamics and Viscoelastic Property of Interface Unravel Combined Functions of Cationic Surfactant and Aromatic Alcohol against Gram-Negative Bacteria.

Lipopolysaccharides (LPSs), the major constituents of the outer membranes of Gram-negative bacteria, play a key role in protecting bacteria against antibiotics and antibacterial agents. In this study, we investigated how a mixture of cationic surfactants and aromatic alcohols, the base materials of widely used sanitizers, synergistically act on LPSs purified from Escherichia coli using isothermal titration calorimetry (ITC), surface tension measurements, and quartz crystal microbalance with dissipation (QCM-D). ITC data measured in the absence of Ca2+ ions showed the coexistence of exothermic and endothermic processes. The exotherm can be interpreted as the electrostatic binding of the cationic surfactant to the negatively charged LPS membrane surface, whereas the endotherm indicates the hydrophobic interaction between the hydrocarbon chains of the surfactants and LPSs. In the presence of Ca2+ ions, only an exothermic reaction was observed by ITC, and no entropically driven endotherm could be detected. Surface tension experiments further revealed that the co-adsorption of surfactants and LPS was synergistic, while that of surfactants and alcohol was negatively synergistic. Moreover, the QCM-D data indicated that the LPS membrane remained intact when the alcohol alone was added to the system. Intriguingly, the LPS membrane became highly susceptible to the combination of cationic surfactants and aromatic alcohols in the absence of Ca2+ ions. The obtained data provide thermodynamic and mechanical insights into the synergistic function of surfactants and alcohols in sanitation, which will enable the identification of the optimal combination of small molecules for a high hygiene level for the post-pandemic society.

Modulation of wetting of stimulus responsive polymer brushes by lipid vesicles: experiments and simulations.

The interactions between vesicle and substrate have been studied by simulation and experiment. We grafted polyacrylic acid brushes containing cysteine side chains at a defined area density on planar lipid membranes. Specular X-ray reflectivity data indicated that the addition of Cd2+ ions induces the compaction of the polymer brush layer and modulates the adhesion of lipid vesicles. Using microinterferometry imaging, we determined the onset level, [CdCl2] = 0.25 mM, at which the wetting of the vesicle emerges. The characteristics of the interactions between vesicle and brush were quantitatively evaluated by the shape of the vesicle near the substrate and height fluctuations of the membrane in contact with brushes. To analyze these experiments, we have systematically studied the shape and adhesion of axially symmetric vesicles for finite-range membrane-substrate interaction, i.e., a relevant experimental characteristic, through simulations. The wetting of vesicles sensitively depends on the interaction range and the approximate estimates of the capillary length change significantly, depending on the adhesion strength. We found, however, that the local transversality condition that relates the maximal curvature at the edge of the adhesion zone to the adhesion strength remains rather accurate even for a finite interaction range as long as the vesicle is large compared to the interaction range.

Lengthened Efferent Limb in Braun Enteroenterostomy Reduces Delayed Gastric Emptying After Pancreaticoduodenectomy.

BACKGROUND: Delayed gastric emptying (DGE) is a common complication after pancreaticoduodenectomy (PD), but a method to prevent DGE has not been established. This study aims to demonstrate a novel technique utilizing a lengthened efferent limb in Billroth-II (B-II) reconstruction during PD and to evaluate the impact of the longer efferent limb on DGE occurrence. METHODS: Patients who underwent PD with B-II reconstruction were divided into two groups: PDs with lengthened (50-60 cm) efferent limb (L group) and standard length (0-30 cm) efferent limb (S group). Postoperative outcomes were compared. DGE was defined and graded according to the International Study Group of Pancreatic Surgery criteria. RESULTS: Among 283 consecutive patients who underwent PD from 2002 to 2021, 206 patients were included in this study. Patients who underwent Roux-en-Y reconstruction (n = 77) were excluded. Compared with the S group, the L group included older patients and those who underwent PD after 2016 (p = 0.025, < 0.001, respectively). D2 lymphadenectomy, antecolic route reconstruction, and Braun enteroenterostomy were performed more frequently in the L group (p = 0.040, < 0.001, < 0.001, respectively). The rate of DGE was significantly decreased to 6% in the L group, compared with 16% in the S group (p = 0.027), which might lead to a shorter hospital stay in the L group (p < 0.001). Multivariable analysis identified two factors as independent predictors for DGE: intraabdominal abscess [odds ratio (OR) 5.530, p = 0.008] and standard efferent limb length (OR 2.969, p = 0.047). CONCLUSION: A lengthened efferent limb in Braun enteroenterostomy could reduce DGE after PD.

Modified Intestinal Derotation Procedure with Reversed Kocherization to Facilitate Mesopancreas Excision During Pancreaticoduodenectomy.

BACKGROUND: Although intestinal derotation procedure has advantages of facilitating mesopancreas excision during pancreaticoduodenectomy, the wide mobilization takes time and risks injuring other organs. This article describes a modified intestinal derotation procedure in pancreaticoduodenectomy and its clinical impact on short-term outcomes. METHODS: The modified procedure comprised the pinpoint mobilization of the proximal jejunum following reversed Kocherization. Among 99 consecutive patients who underwent pancreaticoduodenectomy between 2016 and 2022, the short-term outcomes of pancreaticoduodenectomy with the modified procedure were compared with those of conventional pancreaticoduodenectomy. The feasibility of the modified procedure was investigated based on the vascular anatomy of the mesopancreas. RESULTS: Compared with conventional pancreaticoduodenectomy (n = 55), the modified procedure (n = 44) involved less blood loss and shorter operation time (p < 0.001 and 0.017, respectively). Severe morbidity, clinically relevant postoperative pancreatic fistula, and prolonged hospitalization occurred less often with the modified procedure compared with conventional pancreaticoduodenectomy (p = 0.003, 0.008, and < 0.001, respectively). According to preoperative image findings, most (72%) patients had a single inferior pancreaticoduodenal artery sharing a common trunk with the first jejunal artery. The inferior pancreaticoduodenal vein drained into the jejunal vein in 71% of the patients. The first jejunal vein ran behind the superior mesenteric artery in 77% of the patients. CONCLUSIONS: By combining our modified intestinal derotation procedure with preoperative recognition of the vascular anatomy of mesopancreas, mesopancreas excision during pancreaticoduodenectomy can be performed safely and accurately.

Time-strain inseparability in multiaxial stress relaxation of supramolecular gels formed via host-guest interactions.

Supramolecular hydrogels utilizing host-guest interactions (HG gels) exhibit large deformability and pronounced viscoelasticity. The inclusion complexes between ß-cyclodextrin (host) and adamantane (guest) units on the water-soluble polymers form transient bonds. The HG gels show significant stress relaxation with finite equilibrium stress following the step strain. The stress relaxation process reflects the detachment dynamics of the transient bonds which sustain the initial stress, while the finite equilibrium stress is preserved by the permanent topological cross-links with a rotaxane structure. Nonlinear stress relaxation experiments in biaxial stretching with various combinations of two orthogonal strains unambiguously reveal that time and strain effects on stress are not separable. The relaxation is accelerated for a short time frame (<102 s) with an increase in the magnitude of strain, whereas it is retarded for a longer time window with an increase in the anisotropy of the imposed biaxial strain. The time-strain inseparability in the HG gels is in contrast to the simple nonlinear viscoelasticity of a dual cross-link gel with covalent and transient cross-links in which the separability was previously validated by the same assessment. We currently interpret that the significant susceptibility of the detachment dynamics to the deformation type results from the structural characteristics of the HG gels, i.e., the host and guest moieties covalently connected to the network chains, the considerably low concentrations (<0.1 M) of these moieties, and the slidability of the permanent rotaxane cross-links.

Long-term and short-term outcomes of laparoscopic versus open resection following tube decompression for obstructive colorectal cancer: a single-center retrospective study.

PURPOSE: The benefits of laparoscopic surgery over open surgery are well documented; however, the suitability of laparoscopic surgery for obstructive colorectal cancer is still controversial. The aim of this retrospective study was to compare the clinical benefits of laparoscopic surgery vs. open surgery for obstructive colorectal cancer after tube decompression. METHODS: We analyzed the outcomes of patients who underwent laparoscopic surgery vs. open surgery for curative resection after tube decompression for obstructive colorectal cancer at our hospital between January, 2007 and March, 2018. RESULTS: This study comprised 67 patients: 29 patients who underwent open surgery and 38 patients who underwent laparoscopic surgery. The morbidity within 30 days after surgery was comparable between the groups. The 3-year overall survival rates of the open and laparoscopic groups were 83.3 and 79.4%, respectively (p = 0.6244), and the 3-year disease-free survival rates were 59.3 and 71.2%, respectively (p = 0.3200). Multivariate analysis showed that nodal stage (p = 0.021) was an independent prognostic factor for OS and sex (p = 0.010) and side-ness (p = 0.048) were independent prognostic factors for DFS. CONCLUSION: If adequate decompression is achieved, laparoscopic resection following tube decompression for obstructive colorectal cancer can be a safe alternative to open surgery.

Glucose Metabolism and Aging of Hematopoietic Stem and Progenitor Cells.

Comprehensive proteomics studies of human hematopoietic stem and progenitor cells (HSPC) have revealed that aging of the HSPC compartment is characterized by elevated glycolysis. This is in addition to deregulations found in murine transcriptomics studies, such as an increased differentiation bias towards the myeloid lineage, alterations in DNA repair, and a decrease in lymphoid development. The increase in glycolytic enzyme activity is caused by the expansion of a more glycolytic HSPC subset. We therefore developed a method to isolate HSPC into three distinct categories according to their glucose uptake (GU) levels, namely the GUhigh, GUinter and GUlow subsets. Single-cell transcriptomics studies showed that the GUhigh subset is highly enriched for HSPC with a differentiation bias towards myeloid lineages. Gene set enrichment analysis (GSEA) demonstrated that the gene sets for cell cycle arrest, senescence-associated secretory phenotype, and the anti-apoptosis and P53 pathways are significantly upregulated in the GUhigh population. With this series of studies, we have produced a comprehensive proteomics and single-cell transcriptomics atlas of molecular changes in human HSPC upon aging. Although many of the molecular deregulations are similar to those found in mice, there are significant differences. The most unique finding is the association of elevated central carbon metabolism with senescence. Due to the lack of specific markers, the isolation and collection of senescent cells have yet to be developed, especially for human HSPC. The GUhigh subset from the human HSPC compartment possesses all the transcriptome characteristics of senescence. This property may be exploited to accurately enrich, visualize, and trace senescence development in human bone marrow.

Functionalized supported membranes for quantifying adhesion of P. falciparum-infected erythrocytes.

The pathology of Plasmodium falciparum malaria is largely defined by the cytoadhesion of infected erythrocytes to the microvascular endothelial lining. The complexity of the endothelial surface and the large range of interactions available for the infected erythrocyte via parasite-encoded adhesins make analysis of critical contributions during cytoadherence challenging to define. Here, we have explored supported membranes functionalized with two important adhesion receptors, ICAM1 or CD36, as a quantitative biomimetic surface to help understand the processes involved in cytoadherence. Parasitized erythrocytes bound to the receptor-functionalized membranes with high efficiency and selectivity under both static and flow conditions, with infected wild-type erythrocytes displaying a higher binding capacity than do parasitized heterozygous sickle cells. We further show that the binding efficiency decreased with increasing intermolecular receptor distance and that the cell-surface contacts were highly dynamic and increased with rising wall shear stress as the cell underwent a shape transition. Computer simulations using a deformable cell model explained the wall-shear-stress-induced dynamic changes in cell shape and contact area via the specific physical properties of erythrocytes, the density of adhesins presenting knobs, and the lateral movement of receptors in the supported membrane.

Cost-effectiveness of TAS-102 plus bevacizumab versus TAS-102 monotherapy in patients with metastatic colorectal cancer.

BACKGROUND: TAS-102 plus bevacizumab is an anticipated combination regimen for patients who have metastatic colorectal cancer. However, evidence supporting its use for this indication is limited. We compared the cost-effectiveness of TAS-102 plus bevacizumab combination therapy with TAS-102 monotherapy for patients with chemorefractory metastatic colorectal cancer. METHOD: Markov decision modeling using treatment costs, disease-free survival, and overall survival was performed to examine the cost-effectiveness of TAS-102 plus bevacizumab combination therapy and TAS-102 monotherapy. The Japanese health care payer's perspective was adopted. The outcomes were modeled on the basis of published literature. The incremental cost-effectiveness ratio (ICER) between the two treatment regimens was the primary outcome. Sensitivity analysis was performed and the effect of uncertainty on the model parameters were investigated. RESULTS: TAS-102 plus bevacizumab had an ICER of $21,534 per quality-adjusted life-year (QALY) gained compared with TAS-102 monotherapy. Sensitivity analysis demonstrated that TAS-102 monotherapy was more cost-effective than TAS-102 and bevacizumab combination therapy at a willingness-to-pay of under $50,000 per QALY gained. CONCLUSIONS: TAS-102 and bevacizumab combination therapy is a cost-effective option for patients who have metastatic colorectal cancer in the Japanese health care system.

Nanofocused Scanning X-ray Fluorescence Microscopy Revealing an Effect of Heterozygous Hemoglobin S and C on Biochemical Activities in Plasmodium falciparum-Infected Erythrocytes.

While there is ample evidence suggesting that carriers of heterozygous hemoglobin S and C are protected from life-threatening malaria, little is known about the underlying biochemical mechanisms at the single cell level. Using nanofocused scanning X-ray fluorescence microscopy, we quantify the spatial distribution of individual elements in subcellular compartments, including Fe, S, P, Zn, and Cu, in Plasmodium falciparum-infected (P. falciparum-infected) erythrocytes carrying the wild type or variant hemoglobins. Our data indicate that heterozygous hemoglobin S and C significantly modulate biochemical reactions in parasitized erythrocytes, such as aberrant hemozoin mineralization and a delay in hemoglobin degradation. The label-free scanning X-ray fluorescence imaging has great potential to quantify the spatial distribution of elements in subcellular compartments of P. falciparum-infected erythrocytes and unravel the biochemical mechanisms underpinning disease and protective traits.

Influence of Semifluorinated Alkane Surface Domains on Phase Behavior and Linear and Nonlinear Viscoelasticity of Phospholipid Monolayers.

Semifluorinated alkanes self-assemble into 30-40 nm-large surface domains (hemimicelles) at the air/water interface. They have been drawing increasing attention to stabilize microbubbles coated with lipids, which are used for enhancing the contrast in sonographic imaging. Although previous studies suggested that semifluorinated alkanes increase the stability of phospholipid membranes, little is known about how semifluorinated alkanes influence phase behaviors and mechanical properties of lipid-coated microbubbles. As a well-defined model of microbubble surfaces, we prepared monolayers consisting of a mixture of phospholipids and semifluorinated alkanes at the air/water interface and investigated the influence of hemimicelles of semifluorinated alkanes on the phase behavior and interfacial viscoelastic properties of phospholipid monolayers. Hemimicelles are phase-separated from phospholipids and accumulate at the phase boundary, which strongly modulates the correlation between solid phospholipid domains. Intringuingly, we found that the mixed monolayer of semifluorinated alkanes and phospholipids possesses linear and nonlinear viscoelastic properties comparable to those of phospholipid monolayers. Since the mixing of semifluorinated alkanes and phospholipids enables one to overcome the intrinsically low stability of pure semifluorinated alkanes against the change in the surface area of microbubbles through the partial dissolution of gas into the aqueous phase, this is a promising strategy for the stable coating of microbubbles in ultrasound diagnosis.

HIV-1 Nef Disrupts CD4+ T Lymphocyte Polarity, Extravasation, and Homing to Lymph Nodes via Its Nef-Associated Kinase Complex Interface.

HIV-1 Nef is a multifunctional protein that optimizes virus spread and promotes immune evasion of infected cells to accelerate disease progression in AIDS patients. As one of its activities, Nef reduces the motility of infected CD4+ T lymphocytes in confined space. In vivo, Nef restricts T lymphocyte homing to lymph nodes as it reduces the ability for extravasation at the diapedesis step. Effects of Nef on T lymphocyte motility are typically mediated by its ability to reduce actin remodeling. However, interference with diapedesis does not depend on residues in Nef required for inhibition of host cell actin dynamics. In search for an alternative mechanism by which Nef could alter T lymphocyte extravasation, we noted that the viral protein interferes with the polarization of primary human CD4+ T lymphocytes upon infection with HIV-1. Expression of Nef alone is sufficient to disrupt T cell polarization, and this effect is conserved among lentiviral Nef proteins. Nef acts by arresting the oscillation of CD4+ T cells between polarized and nonpolarized morphologies. Mapping studies identified the binding site for the Nef-associated kinase complex (NAKC) as critical determinant of this Nef activity and a NAKC-binding-deficient Nef variant fails to impair CD4+ T lymphocyte extravasation and homing to lymph nodes. These results thus imply the disruption of T lymphocyte polarity via its NAKC binding site as a novel mechanism by which lentiviral Nef proteins alter T lymphocyte migration in vivo.

Influence of Perfluorohexane-Enriched Atmosphere on Viscoelasticity and Structural Order of Self-Assembled Semifluorinated Alkanes at the Air-Water Interface.

Semifluorinated alkanes FnHm self-assemble into nanometer-sized surface micelles at the air-water interface. In this study, we investigated how an atmosphere enriched with perfluorohexane (PFH) influences the interfacial viscoelasticity and structural order of a monolayer of FnHm by the combination of dilational rheology and grazing-incidence small-angle X-ray scattering (GISAXS). The monolayers behaved predominantly elastic which can be attributed to the strong dipole repulsions of the surface domains. Enrichment of the atmosphere with PFH lead to an increase of the compressibility and a decrease of the elastic modulus without altering the structural ordering of the FnHm molecules into highly correlated nanodomains, suggesting the adsorption of PFH molecules to the free spaces between the domains. The capability of FnHm domains to retain the structural integrity in the presence of PFH gas is promising for the fabrication of stable microbubbles for sonographic imaging.

Long-Range Lateral Correlation between Self-Assembled Domains of Fluorocarbon-Hydrocarbon Tetrablocks by Quantitative GISAXS.

The structure and lateral correlation of fluorocarbon-hydrocarbon tetrablock di(F10Hm) domains at the air/water interface have been determined by quantitative analysis of grazing incidence small-angle X-ray scattering (GISAXS) data. The measured GISAXS signals can be well represented by the full calculation of the form and structure factors. The form factor suggests that di(F10Hm) domains take a hemiellipsoid shape. Both major and minor axes of the hemiellipsoids monotonically increased in response to the elongation of the hydrocarbon blocks, which can be explained by the concominant increase in van der Waals interaction. The structure factor calculated from the GISAXS signals suggests that the domains take an orthorhombic lattice. Remarkably, the lateral correlation can reach over a distance that is more than 14 times longer than the distance to the nearest neighbors. Our data suggest that quantitative GISAXS enables the optimal design of mesoscopic self-assemblies at the air/water interface by fine-tuning of the structures of molecular building blocks.

Shear-Enhanced Dynamic Adhesion of Lactobacillus rhamnosus GG on Intestinal Epithelia: Correlative Effect of Protein Expression and Interface Mechanics.

The oral uptake of probiotic microorganisms as food additives is one widely used strategy to sustain and improve the homeostasis of intestinal microbiota that protect the intestinal epithelia from attack by pathogenic bacteria. Once delivered to the ileum and colon, probiotics must adhere and form colonies on mucus that coats the surface of intestinal epithelial cells. Although an increasing amount of knowledge about the genetic and molecular level mechanisms of probiotics-mucus interactions has been accumulated, little is known about the physicochemical aspects of probiotics-mucus interactions under physiological shear in intestines. In this study, we established well-defined models of intestinal epithelial cell monolayers based on two major constituents of gut epithelia, enterocytes and goblet cells. First, the formation of a polarized cell monolayer sealed by tight junctions was monitored by transepithelial electrical resistance over time. The establishment of tight junctions and secretion of mucus proteins (mucin) was confirmed by immunofluorescence staining. In the next step, we measured the elasticity of cell monolayer surfaces by indentation using particle-assisted atomic force microscopy. The effective elastic modulus of goblet cell-like cells was 30 times smaller compared to that of enterocyte-like cells, which can be attributed to the secretion of a 3 µm thick mucin layer. As probiotics, we used Lactobacillus rhamnosus GG (LGG), which is one of the most widely used strains as food additives. To investigate the dynamic adhesion of LGG to the intestine model surface, we transferred the epithelial cell monolayer into a microfluidic chamber. A distinct difference in dynamic adhesion between two cell types was observed, which could be attributed to the difference in the mucin expression amount. Remarkably, we found that the dynamic LGG adhesion is enhanced by the increase in shear stress, showing a maximum binding efficiency at 0.3 Pa. Finally, we examined the persistence of LGG adhesion by a stepwise increase in the shear stress exerted on adherent LGG, demonstrating that LGG could withstand high shear stress even beyond that of physiological stress. The obtained results present a large potential to quantitatively understand the influence of engineered foods and probiotics on the homeostasis of microbiota on the surface of intestinal epithelia.

Dynamic Contact Guidance of Myoblasts by Feature Size and Reversible Switching of Substrate Topography: Orchestration of Cell Shape, Orientation, and Nematic Ordering of Actin Cytoskeletons.

Biological cells in tissues alter their shapes, positions, and orientations in response to dynamic changes in their physical microenvironments. Here, we investigated the dynamic response of myoblast cells by fabricating substrates displaying microwrinkles that can reversibly change their direction within 60 s by axial compression and relaxation. To quantitatively assess the collective order of cells, we introduced the nematic order parameter of cells that takes not only the distribution of cell-wrinkle angles but also the degree of cell elongation into account. On the subcellular level, we also calculated the nematic order parameter of actin cytoskeletons that takes the rearrangement of actin filaments into consideration. The results obtained on substrates with different wrinkle wavelengths implied the presence of a characteristic wavelength beyond which the order parameters of both cells and actin cytoskeletons level off. Immunofluorescence labeling of vinculin showed that the focal adhesions were all concentrated on the peaks of wrinkles when the wavelength is below the characteristic value. On the other hand, we found focal adhesions on both the peaks and the troughs of wrinkles when the wavelength exceeds the characteristic level. The emergence of collective ordering of cytoskeletons and the adaptation of cell shapes and orientations were monitored by live cell imaging after the seeding of cells from suspensions. After the cells had reached the steady state, the orientation of wrinkles was abruptly changed by 90°. The dynamic response of myoblasts to the drastic change in surface topography was monitored, demonstrating the coordination of the shape and orientation of cells and the nematic ordering of actin cytoskeletons. The "dynamic" substrates established in this study can be used as a powerful tool in mechanobiology that helps us understand how cytoskeletons, cells, and cell ensembles respond to dynamic contact guidance cues.

[Thoracoscopic Resection of a Mediastinal Enteric Cyst Assisted with Artificial Pneumothorax in the Prone Position].

Mediastinal enteric cysts are very rare among in adults and usually asymptomatic. A 54-year-old male was referred to our hospital due to an abnormal shadow incidentally found on a chest X-ray at health check. Chest computed tomography scan revealed a cystic mass in the posterior and inferior mediastinum surrounded by diaphragm, inferior vena cava, and esophagus. Based on many reports of thoracoscopic esophagectomy in the prone position in recent years, we chose thoracoscopic resection of the mediastinal tumor in the prone position with artificial pneumothorax. The prone position with artificial pneumothorax provided much better exposure of the operating field and the surgery was performed successfully.

Neutron Scattering Reveals Water Confined in a Watertight Bilayer Vesicle.

Water molecules confined in a nanocavity possess distinctly different characteristics from those in bulk, yet the preparation of such nanocavities is still a major experimental challenge. We report here a self-assembled vesicle of an anionic perfluoroalkylated [60]fullerene, unique for its outstanding stability and water tightness, containing water not bound to the membranes. Small-angle neutron scattering revealed that a vesicle of 14 nm outer radius contains a 2 nm thick fullerene bilayer, inside of which is a 3 nm thick membrane-bound water and unbound water in the 4 nm innermost cavity. The vesicle shows astonishingly low water permeability that is 6 to 9 orders of magnitude smaller than that of a lipid vesicle. As a result, a single vesicle isolated on a substrate can retain the interior water in air or even under high vacuum, indicating that the vesicle cavity provides a new tool for physicochemical studies of confined water as well as ions and molecules dissolved in it.

Ib-AMP4 insertion causes surface rearrangement in the phospholipid bilayer of biomembranes: Implications from quartz-crystal microbalance with dissipation.

Most antimicrobial peptides exert their rapid bactericidal activity through a unique mechanism of bacterial membrane disruption. However, the molecular events that underlie this mechanism remain partly unresolved. In this study, the frequency shift (ΔF) obtained through quartz-crystal microbalance with dissipation (QCM-D) indicated that the initial binding of Ib-AMP4 within the lipid membrane started at a critical Ib-AMP4 concentration that exceeded 100µg/ml. Circular dichroism measurements provided evidence that Ib-AMP4 occurs in a ß-sheet configuration which is adapted for insertion into the lipid membrane. Monolayer experiments and the value of dissipation alteration (ΔD) obtained through QCM-D showed that the pressure increased within the phospholipid bilayer upon peptide insertion, and the increase in pressure subsequently forced the bilayer to wrinkle and form pores. However, D continued to increase, indicating that the membrane surface underwent a dramatic morphological transition: the membrane surface likely became porous and uneven as Ib-AMP4 projected from the external surface of the lipid bilayer. Intensive peptide insertion, however, soon plateaued 1min after the addition of Ib-AMP4. This behaviour corresponded with the results of bactericidal kinetics and liposome leakage assays. A sudden decrease in D accompanied by a negligible decrease in F occurred after replacing the Ib-AMP4 solution with HEPES buffer. This result implied that the bilayer surface rearranged and that poration and wrinkling decreased without further peptide insertion. Transmission electron microscopy results indicated that pore formation occurred during Ib-AMP4 insertion but eventually subsided. Therefore, the mode of action of AMP in bacterial membranes could be elucidated through QCM-D.

Newly Synthesized Lipid-Porphyrin Conjugates: Evaluation of Their Self-Assembling Properties, Their Miscibility with Phospholipids and Their Photodynamic Activity In Vitro.

Lipid-porphyrin conjugates are considered nowadays as promising building blocks for the conception of supramolecular structures with multifunctional properties, required for efficient cancer therapy by photodynamic therapy (PDT). The synthesis of two new lipid-porphyrin conjugates coupling pheophorbide-a (Pheo-a), a photosensitizer derived from chlorophyll-a, to either chemically modified lyso-phosphatidylcholine (PhLPC) or egg lyso-sphingomyelin (PhLSM) is reported. The impact of the lipid backbone of these conjugates on their self-assembling properties, as well as on their physicochemical properties, including interfacial behavior at the air/buffer interface, fluorescence and absorption properties, thermotropic behavior, and incorporation rate in the membrane of liposomes were studied. Finally, their photodynamic activity was evaluated on esophageal squamous cell carcinoma (ESCC) and normal esophageal squamous epithelium cell lines. The liposome-like vesicles resulting from self-assembly of the pure conjugates were unstable and turned into aggregates with undefined structure within few days. However, both lipid-porphyrin conjugates could be efficiently incorporated in lipid vesicles, with higher loading rates than unconjugated Pheo-a. Interestingly, phototoxicity tests of free and liposome-incorporated lipid-porphyrin conjugates demonstrated a better selectivity in vitro to esophageal squamous cell carcinoma relative to normal cells.