Phosphatidylcholine Group Research Articles

Association equilibria of divalent ions on the surface of liposomes formed from phosphatidylcholine

.Divalent ions, in particular calcium ions, constitute important macroelements in living organisms. They are also found in cell membranes, i.e., ensuring their stabilization or participating in synaptic transmission of nerve impulses. The aim of this work is to describe the interactions of divalent ions, such as Ca2+, Ba2+, and Sr2+, in electrolytes with the functional groups on the surface of liposomes formed from phosphatidylcholine (PC). Microelectrophoresis is used to determine the surface charge density as a function of pH. The interactions between ions found in solution and the functional groups of PC are described with the use of a seven-equilibrium mathematical model. Using this model along with experimental data on the charge density of the membrane surface, the association constants characterizing this equilibrium are determined. These parameters are used to calculate the theoretical model curves. The validity of the proposed model is confirmed by comparing the theoretically calculated changes in charge density on the liposome surface with the experimental results.Graphical abstract

The efficacy of saxagliptin in T2DM patients with non-alcoholic fatty liver disease: preliminary data.

To investigate the clinical efficacy and the possible mechanisms of saxagliptin in the treatment of type 2 diabetes mellitus (T2DM) combined with non-alcoholic fatty liver disease (NAFLD). A total of 95 T2DM and NAFLD patients were randomly divided into group A (saxagliptin group), group B (glimepiride group), and group C (glimepiride combined with polyene phosphatidylcholine group). After intervention treatment for 24 w, body mass index (BMI), waist-to-hip ratio (WHR), glycated haemoglobin (HbA1c), fasting plasma glucose (FPG), fasting insulin (FINS), homeostatic model assessment of insulin resistance (HOMA-IR), interleukin-6 (IL-6), triglyceride (TG), total cholesterol (TC), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (γ-GT), and quantitative detection of liver steatosis of study subjects were observed, the action of liver steatosis in subjects of groups A and C were significantly different from those of group B; however, there were no differences between groups A and C. The FINS, HOMA-IR, and IL-6 of subjects in group A was lower than those in groups B and C; however, there were no significant differences between the latter two groups. For T2DM combined with NAFLD patients, the saxagliptin treatment could not only effectively control blood glucose but also attenuate insulin resistance and inflammatory injury of the liver to improve fatty liver further.

Cell membrane adhesive n-hexadecyl choline phosphate as vaccine delivery systems for anticancer immunotherapy

In recent years, cancer immunotherapy as a new generation of cancer treatment strategy has displayed promising potential and attracted more and more attention. However, tumor-associated antigens if used alone could not induce potent immune responses. Therefore, efficient tumor treatment demands the assistance of vaccine delivery systems to elicit strong anti-tumor immune responses. In this study, a novel cell membrane adhesive vaccine carrier—n-hexadecyl choline phosphate (C16-CP) was synthesized and evaluated for the delivery of model antigen ovalbumin (OVA) and for anticancer therapy. Choline phosphate (CP) group is orientated opposite to and hence has electrostatic attraction with the phosphatidylcholine group of cell membrane component dipalmitoyl phosphatidylcholine. Moreover, CP group was hydrophobically modified with n-hexadecyl chain to prepare a cell membrane adhesive molecule C16-CP, which could adhere to cell membrane through electrostatic attraction and hydrophobic interaction. The CP group is positively charged at neutral pH environment. Hence, the cationic lipid C16-CP could interact with OVA through electrostatic attraction and hydrophobic interaction. In this work, the potential of C16-CP to assist antigen delivery was evaluated in order to develop a novel vaccine delivery system.

Location, location, location: lipid metabolism varies in different parts of the seed.

Location, location, location: lipid metabolism varies in different parts of the seed.

Pramlintide: The Effects of a Single Drug Injection on Blood Phosphatidylcholine Profile for Alzheimer's Disease.

Studies suggest that a single injection of pramlintide, an amylin analog, induces changes in Alzheimer's disease (AD) biomarkers in the blood of AD mouse models and AD patients. The aim of this study was to examine whether a pramlintide challenge combined with a phosphatidylcholine (PC) profile diagnoses of AD and mild cognitive impairment (MCI) better than PC alone. Non-diabetic subjects with cognitive status were administered a single subcutaneous injection of 60 mcg of pramlintide under fasting condition. A total of 71 PCs, amyloid-β peptide (Aβ), and total tau (t-tau) in plasma at different time points were measured and treated as individual variables. A single injection of pramlintide altered the levels of 7 PCs in the blood, while a pramlintide injection plus food modulated the levels of 10 PCs in the blood (p < 0.05). The levels of 2 PCs in MCI and 12 PCs in AD in the pramlintide challenge were significantly lower than the ones in controls. We found that while some PCs were associated with only Aβ levels, other PCs were associated with both Aβ and t-tau levels. A receiver operating characteristic analysis of the PCs was combined with the Aβ and t-tau data to produce an area under the curve predictive value of 0.9799 between MCI subjects and controls, 0.9794 between AD subjects and controls, and 0.9490 between AD and MCI subjects. A combination of AD biomarkers and a group of PCs post a pramlintide challenge may provide a valuable diagnostic and prognostic test for AD and MCI.

NMR Contacts between the HIV Fusion Peptide and Lipid Support a Beta-Bowl Membrane Topology of the Peptide with Thermodynamic Preference for Peptide/Cholesterol Contact

The HIV fusion peptide (FP) is the ∼25-residue N-terminal region of the gp41 protein and plays a critical role in joining virus and host cell membranes. Segments of gp41 that include the FP catalyze fusion of membrane vesicles, which supports a FP contribution to viral fusion. The FP adopts intermolecular antiparallel β sheet structure in membrane that contains ∼30 mole% cholesterol, which is typical for HIV host cells. NMR measurements support distinct populations of membrane locations of the FP β sheet. The dominant population has <5 Å contacts between residues in the sheet interior and –CH3 groups of phosphatidylcholine (PC) and cholesterol lipids near the membrane center. Longer >10 Å distances are detected to lipid headgroups. By contrast, close headgroup contacts are observed for residues at the sheet edges, with longer distances to the –CH3 groups. There is a smaller FP population with contacts between interior strand residues and the membrane surface. A FP β-bowl inserted in a single membrane leaflet is consistent with many of these contact data. The middle sections of interior strands of the bowl contact the membrane center, whereas strand termini contact lipid headgroups. Most of the bowl edge strands contact the membrane surface. Lipids contacting the bowl adopt its curvature, which may reduce activation energy needed to achieve the high-curvature transition state of fusion. The NMR data also support higher population of FP-cholesterol vs. FP-PC contacts. The thermodynamic preference of cholesterol for the FP bowl may be due to higher intrinsic curvature of cholesterol vs. PC.

Study of the interaction of water with phospholipid bilayers by FTIR spectroscopy

The hydration of the dimyristoylphosphatidylcholine multi-bilayers has been studied by means of Fourier transform infrared spectroscopy. The structure of water confined in lipid membrane, under water-rich and water-poor conditions has been investigated by examining the OH stretching band region. We found that the structure of solvation water of lipid bilayer differs from bulk water. In addition, interaction of water molecules with carbonyl group and phosphate group of phosphatidylcholine have been observed through the downshift of the relative vibrational components representing hydrogen bonded groups. We infer that the disorder of the water network occurs especially in the interfacial region of phospholipids and it increases above the gel to liquid crystalline phase transition, giving rise to an increase of the absorption around 3600 cm -1 which indicates the presence of weakly hydrogen bonded water aggregates.

Analyzing Liposomal Drug Delivery Systems in Three-Dimensional Cell Culture Models Using MALDI Imaging Mass Spectrometry.

Cancer chemotherapeutics often fail to reach all diseased cells. To help solve this problem, researchers are investigating novel drug delivery systems. Liposomes are an attractive option due to their low toxicity, high biocompatibility, and potential to carry a large amount of a drug to the tumor site, all while avoiding being eliminated from the body. This study evaluates the penetration of doxorubicin-encased liposomes into three-dimensional cell cultures, or spheroids. Liposomes composed of lipids containing head groups of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cholesterol were created by extrusion. Doxorubicin is encapsulated within the hydrophilic core of the liposome. The drug is actively released in the spheroid as the lipids bind to cellular lipid bilayers. Spheroids were dosed with liposomal doxorubicin, free doxorubicin, or media control to assess drug distribution over the course of 72 h. Drug penetration was visualized by Matrix-Assisted Laser Desorption/Ionization-Imaging Mass Spectrometry (MALDI-IMS) with confirmation by steady state fluorescence microscopy, creating a comprehensive picture of drug distribution. This technique is able to identify both free and liposomal doxorubicin throughout the spheroid after just 12 hours of treatment. Additionally, MALDI-IMS is able to detect three metabolites of doxorubicin, indicating that cells actively metabolize the drug during treatment. Steady state fluorescence microscopy cannot distinguish the drug from its metabolites as they have the same emission spectra. This report summarizes the first study to use MALDI-IMS to analyze drug penetration of a liposomal drug carrier as well as its metabolites.

Effects of telmisartan on improving leptin resistance and inhibiting hepatic fibrosis in rats with non-alcoholic fatty liver disease.

The present study aimed to investigate the impacts of telmisartan (TEL) on hepatic fibrosis, serum leptin, leptin protein in liver tissue and its mRNA expression level in rats with non-alcoholic fatty liver disease (NAFLD). Male Sprague Dawley rats were randomly divided into the control (N), model (M), polyene phosphatidylcholine (P) and TEL (T) groups. Group M and the intervention groups were given a high-fat diet for 12 weeks to induce NAFLD, followed by 4 weeks of intragastric administration of normal saline (1.0 ml/kg/day), polyene phosphatidylcholine (PPC; 123.1 mg/kg/day) and TEL (8 mg/kg/day). The liver tissue was then assessed for the NAFLD activity score and fibrosis score (FS), and serum biochemistry and leptin levels were determined. Additionally, leptin protein expression levels were examined by western blotting and the expression of leptin mRNA was investigated by reverse transcription-polymerase chain reaction. TEL significantly improved FS in rats (P<0.01) and was more effective than PPC. TEL significantly reduced the expression of serum leptin, as well as the expression levels of leptin protein and its mRNA in liver tissue (P<0.01); however, the effects of PPC were not significant (P>0.05). TEL reduced serum leptin, leptin protein and its mRNA in the liver tissue of NAFLD rats, and improved the pathological indicators of liver fibrosis.

Immobilization and detection of platelet-derived extracellular vesicles on functionalized silicon substrate: cytometric and spectrometric approach

Among the various biomarkers that are used to diagnose or monitor disease, extracellular vesicles (EVs) represent one of the most promising targets in the development of new therapeutic strategies and the application of new diagnostic methods. The detection of circulating platelet-derived microvesicles (PMVs) is a considerable challenge for laboratory diagnostics, especially in the preliminary phase of a disease. In this study, we present a multistep approach to immobilizing and detecting PMVs in biological samples (microvesicles generated from activated platelets and human platelet-poor plasma) on functionalized silicon substrate. We describe the application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and spectroscopic ellipsometry methods to the detection of immobilized PMVs in the context of a novel imaging flow cytometry (ISX) technique and atomic force microscopy (AFM). This novel approach allowed us to confirm the presence of the abundant microvesicle phospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) on a surface with immobilized PMVs. Phosphatidylcholine groups (C5H12N+; C5H15PNO4+) were also detected. Moreover, we were able to show that ellipsometry permitted the immobilization of PMVs on a functionalized surface to be evaluated. The sensitivity of the ISX technique depends on the size and refractive index of the analyzed microvesicles.Graphical abstractHuman platelets activated with thrombin (in concentration 1IU/mL) generate population of PMVs (platelet derived microvesicles), which can be detected and enumerated with fluorescent-label method (imaging cytometry). Alternatively, PMVs can be immobilized on the modified silicon substrate which is functionalized with a specific IgM murine monoclonal antibody against human glycoprotein IIb/IIIa complex (PAC-1). Immobilized PMVs can be subjected to label-free analyses by means ellipsometry, atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

Insight into the Tribological Behavior of Liposomes in Artificial Joints.

Liposomes are widely used in drug delivery and gene therapy, and their new role as boundary lubricant in natural/artificial joints has been found in recent years. In this study, the tribological properties of liposomes on titanium alloy (Ti6Al4 V)/UHMWPE interface were studied by a ball-on-disc tribometer. The efficient reduction of friction coefficient and wear on both surfaces under various velocities and loads is found. A multilayer structure of physically adsorbed liposomes on Ti6Al4 V surface was also observed by atomic force microscope (AFM). Except for the hydration mechanism by phosphatidylcholine (PC) groups, the well-performed tribological properties by liposomes is also attributed to the existence of adsorbed liposome layers on both surfaces, which could reduce asperities contact and show great bearing capacity. This work enriches the research on liposomes for lubrication improvement on artificial surface and shows their value in clinical application.

In vivo protective effect of phosphatidylcholine on carbon tetrachloride induced nephrotoxicity

Phosphatidylcholine (PC) from egg yolk is a bioactive substance with various beneficial effects, including anti-inflammatory and anti-oxidant effects. Recently, this substance has been reported to prevent acute hepatotoxicity. In the present study, we aimed to evaluate the putative protective effect of PC on carbon tetrachloride (CCl4)-induced nephrotoxicity in ICR mice. Many previous studies demonstrated that CCl4 induces nephrotoxicity resulting in renal oxidative damage. CCl4 in corn oil (0.1ml, 1.2g/kg) was intra-peritoneally injected into 7-week-old ICR mice twice a week. PC in corn oil (0.1ml, 100mg/kg) was then orally injected daily for a week. In 7 days, blood urea nitrogen (BUN) and creatinine concentrations had significantly increased in the CCl4 group compared to the control group, whereas the PC and CCl4 co-injected group had significantly decreased BUN and creatinine concentrations compared to the CCl4 group. Comparative analysis of histopathological injuries revealed that PC abrogated the nephrotoxicity of CCl4 at 7 days. Accordingly, PC also improved renal fibrosis induced by CCl4. Various biomarkers associated with oxidative damage appeared to be up-regulated in the CCl4 group, whereas in the PC and CCl4 co-injected group, levels of oxidative damage significantly decreased. Aquaporin1 (AQP1), an important water transport protein in the kidney, was down regulated in the CCl4 group compared to the control group. PC counteracted this effect. These results strongly suggest that PC can protect against oxidative damage induced by CCl4 in the kidney and enhance recovery from renal disorders.

Effects of different fatty acids composition of phosphatidylcholine on brain function of dementia mice induced by scopolamine.

BackgroundPhosphatidylcholine (PC), the major source of dietary choline, has been demonstrated to improve the capability of learning and memory in rodent and the amelioration of long-chain n-3 polyunsaturated fatty acids (PUFA) on anti-aging and anti-oxidation is widely known as well. In this study, three kinds of PC were chose to demonstrate the role of different fatty acids composition on glycerol backbone in improving the brain function of mice induced by scopolamine which was used to impair cholinergic system and cause oxidative stress.MethodsMale BALB/c mice were randomly divided into 5 groups: model (M) group, control (Con) group, egg yolk lecithin (EL) group, squid PC (SQ-PC) group and sea cucumber PC (SC-PC) group. The intraperitoneal injection of scopolamine hydrobromide (5 mg/kg) was carried out on the 8th of group feeding and sustained daily until the end of test. Morris water maze test was used to evaluate the improvement of cognitive decline and the activity of acetylcholinesterase (AchE), superoxide dismutase (SOD) and monoamine oxidase (MAO) and malondialdehyde (MDA) content in brain were measured to assess the physiological changes.ResultsIn behavior test, the latency of PC groups was significantly reduced, while number of crossing the platform and time in target quadrant were increased in comparison with M group and the improvements of SQ-PC and SC-PC were better than that of EL (P < 0.05). Similar trend was observed in physiological changes. The AchE activity was effectively decreased and the SOD activity increased in hippocampus, cortex and white matter when comparing PC groups with M group. SQ-PC, SC-PC and EL respectively showed 22.82, 28.80 and 11.81 % decrease in MDA level in brain compared with M group. The MAO activity in white matter of SQ-PC, SC-PC and EL group separately depressed 33.05, 33.64 and 19.73 % in comparison with M group. No significance between SQ-PC and SC-PC was found in these indicators except the SOD activity in hippocampus and white matter. SQ-PC group had a higher SOD activity in hippocampus (103.68U/mg · prot.) and lower in white matter (120.57 U/mg · prot.) than SC-PC group (95.53 U/mg · prot. in hippocampus, 134.49 U/mg · prot. in white matter). PC rich in n-3 PUFA acted more ameliorative effects than that barely contained on the indicators above.ConclusionsDifferent fatty acids composition of PC all could diminish the cognitive decline and biological damage and protect the brain. EPA and DHA partly enhaced to the advantageous effects.

Direct Enzymatic Synthesis of 1‐Phosphatidyl‐β‐D‐glucose by Engineered Phospholipase D

AbstractA simple, direct method for the synthesis of 1‐phosphatidyl‐β‐D‐glucose (1‐PGlc) was established, being the first example of direct enzymatic synthesis of this recently discovered, highly important bioactive phospholipid. The method employs phospholipase D (PLD, E.C. 3.1.4.4)‐catalyzed transphosphatidylation, in which the polar head group of phosphatidylcholine is exchanged to glucose. Although wild‐type PLD can catalyze the transfer reaction, it provides only 6‐phosphatidyl‐glucose, a positional isomer of 1‐PGlc, due to its strong preference towards the primary hydroxyl group. To synthesize 1‐PGlc, engineered PLD variants, previously isolated as the ones active on secondary hydroxyls of inositol, were screened for the ability to catalyze the reaction. One of the variants, 187K/191W/385Y (KWY), was identified as the best‐performing in 1‐PGlc synthesis, however, in addition to 1‐PGlc the reaction with KWY also afforded undesired positional isomers as byproducts. To facilitate the isolation of 1‐PGlc, the isomers were converted into the corresponding amines by reductive amination. Following the column chromatography, the desired product was isolated with the overall yield of 12.5 %. The structure of the product was confirmed by 1H‐NMR analysis.

Biosorption of aluminum through the use of non-viable biomass of Pseudomonas putida

Living and non-living biomass of Pseudomonas putida A (ATCC 12633) was used as biosorbent for the removing of Al3+ from aqueous solutions. The process was stable with time, efficient at pH 4.3 and between 15°C and 42°C. Two isotherms models were applied to describe the interaction between the biosorbent and Al3+. Non-living biomass of P. putida A (ATCC 12633) was found to be the most efficient at adsorbing Al3+ with a maximum sorption capacity of 0.55mg Al3+/gr adsorbent and with 36×105 binding sites of Al3+/microorganisms. Infrared spectroscopy analysis shows that the biosorbent present some vibrational band of functional groups that change in presence of Al3+: hydroxyl, carboxyl and phosphate. Considering that Al3+ binds to the phosphate group of phosphatidylcholine, non-viable biomass of P. putida PB01 (mutant lacking phosphatidylcholine) was used. Aluminum adsorption of the parental strain was 30 times higher than values registered in P. putida PB01 (36×105 sites/microorganism vs 1.2×105 sites/microorganism, respectively). This result evidenced that the absence of phosphatidylcholine significantly affected the availability of the binding sites and consequently the efficiency of the biomass to adsorb Al3+.

Iron Ion and Iron Hydroxide Adsorption to Charge-Neutral Phosphatidylcholine Templates.

Surface-sensitive X-ray scattering and spectroscopy techniques reveal significant adsorption of iron ions and iron-hydroxide (Fe(III)) complexes to a charge-neutral zwitterionic template of phosphatidylcholine (PC). The PC template is formed by a Langmuir monolayer of dipalmitoyl-PC (DPPC) that is spread on the surface of 2 to 40 μM FeCl3 solutions at physiological levels of KCl (100 mM). At 40 μM of Fe(III) as many as ∼3 iron atoms are associated with each PC group. Grazing incidence X-ray diffraction measurements indicate a significant disruption in the in-plane ordering of DPPC molecules upon iron adsorption. The binding of iron-hydroxide complexes to a neutral PC surface is yet another example of nonelectrostatic, presumably covalent bonding to a charge-neutral organic template. The strong binding and the disruption of in-plane lipid structure has biological implications on the integrity of PC-derived lipid membranes, including those based on sphingomyelin.

Association of alkali metal cations with phosphatidylcholine liposomal membrane surface

Interactions of alkali metal cations (Li+, Na+, K+, Cs+) with phosphatidylcholine (PC) liposomal membranes were investigated through experimental studies and theoretical considerations. Using a microelectrophoresis technique, charge densities of experimental membrane surfaces were measured as a function of the pH of electrolyte solutions. Equilibria between the PC liposomal membranes and monovalent ions were mathematically analyzed and described quantitatively through a previously proposed theoretical model. Association constants between functional groups of PC and the studied ions were determined and used to define theoretical curves of membrane surface charge density versus pH. Theoretical and experimental data were compared to verify the model. The PC membrane was found to have the highest affinity for lithium ions, among the ions tested.

Choline phosphate functionalized cellulose membrane: A potential hemostatic dressing based on a unique bioadhesion mechanism

Wound dressings are a key component in provision of optimal conditions for bleeding control and wound healing. For absorbent dressings, electrostatic interactions are frequently utilized as one of the mechanisms driving dressing adhesion. Herein, a choline phosphate functionalized biocompatible cellulose membrane that can efficiently arrest human red blood cells was developed to have potential application in wound dressing. The bioadhesion is based on the unique multivalent electrostatic interaction between the head groups of phosphatidyl choline based lipids on the cell membrane and its inverse orientation but virtually identical structure, choline phosphate, coupled to the cellulose membrane. For functionalization, the cellulose membrane was decorated with polymer brushes bearing multiple choline phosphate groups via surface-initiator atom transfer radical polymerization followed by click chemistry. The modified cellulose membranes were characterized by ATR-FTIR and the molecular weight and the grafting density of polymer brushes grafted from the cellulose membrane surface were thoroughly evaluated by calibrated force-distance measurements with atomic force microscopy (AFM). This new method provides an approach to estimating polymer brush parameters on rough surfaces of unknown surface area based on the dependence of brush thickness on brush density and polymer molecular weight for a calibration set of brushes. The dependence of binding of human red blood cells (RBCs) to the cellulose membrane surface on the number density of choline phosphate groups (e.g. molecular weight) and the grafting density were investigated using this AFM-based approach. Bound RBCs showed “pseudopodia”-like membrane projections under scanning electron microscopy where cells contacted the microfibers of the cellulose, distorting the RBC shape, reflecting the multivalent interactions between the RBCs and the choline phosphate-doped cellulose membrane. We believe this efficient strategy provides a promising approach to blood conservation and trauma management. Statement of SignificanceUncontrolled bleeding can dramatically affect morbidity and mortality. Absorptive wound dressings provide either adherent or non-adherent layers to control bleeding. Our new adherent material is based on a universal adhesion reaction between cell membrane phosphatidyl choline (PC) headgroups and cellulose membranes (CM) decorated with polymer brushes carrying a CP group per monomer. The CP-PC multivalent interactions provide adherence to cut tissue margins and blood cells, blocking bleeding. We here demonstrate the strong specific binding of red cells to CM-CP but not CM-PC membranes and determine the requisite brush molecular weight and surface concentration via a new approach using atomic force microscopy, applicable to rough surfaces. We believe this strategy provides a promising approach to blood conservation and trauma management.

Chondroitin sulfate interacts mainly with headgroups in phospholipid monolayers

Sulfated glycosaminoglycans are precursors of the extracellular matrix used to treat diseases related to blood clotting and degenerative joint diseases. These medical applications have been well established, but the mode of action at the molecular level, which depends on the interaction with cell membranes, is not known in detail. In this study, we investigated the interaction between chondroitin sulfate (CS) and phospholipid monolayers that mimic cell membranes. From surface pressure isotherms and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), CS was found to interact mainly with the polar groups of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG), with negligible penetration into the hydrophobic tails and only small changes in monolayer elasticity for the packing corresponding to a real cell membrane. The changes in surface pressure and surface potential isotherms depended on CS concentration and on the time allowed for its adsorption onto the monolayer, which points to a dynamic adsorption-desorption process. The charge of the phospholipid was also relevant, since CS induced order into DPPC monolayers while the opposite occurred for DPPG, according to the PM-IRRAS spectra. In summary, interaction with polar groups is responsible for the CS effects on model cell membranes.

Development of functional electrospun fiber mats for potential wound healing and blood conservation

Event Abstract Back to Event Development of functional electrospun fiber mats for potential wound healing and blood conservation Xiaoqiang Yang1, 2, Jayachandran Kizhakkedathu1, 2 and Donald Brooks1, 2, 3 1 University of British Columbia, Centre for Blood Research, Canada 2 University of British Columbia, Department of Pathology & Laboratory Medicine, Canada 3 University of British Columbia, Department of Chemistry, Canada Introduction: Our aim is to develop and evaluate a novel tissue sealant utilizing the universal adhesion reaction based on multivalent interactions between phosphatidyl choline (PC) lipid head groups on cell membranes and synthetic choline phosphate (CP)–containing polymers[1]. Such polymers when electrospun into pads should both adhere to solid tissue and bind red blood cells (RBCs) and platelets to arrest bleeding at sites of tissue damage or surgery where vascular integrity is breached. These polymer webs should meet the mechanical and functional requirements for wound healing and blood conservation applications[2]-[5]. Materials and Methods: A nano scale fiber web consisting of a random copolymer containing the backbone of ε-caprolactone and its derivative with a pendent hydrophilic segment bearing functional CP groups was prepared by the electrospinning process. To achieve the copolymer, a new cyclic ester, γ-(2-bromo-2-methly propionyl)-ε-caprolactone, containing a pendent-activated alkyl bromide functional group was prepared[6]. This new monomer serves as both a monomer for ring-opening polymerization (ROP) with ε-caprolacone as well as an initiator for controlled atom transfer radical polymerization (ATRP). The random co-poly(caprolactone) via ROP was tuned to make a suitable candidate for the electrospin process, balancing hydrophobicity, hydrophilicity and the density of functional groups by adjusting the ratio of new monomer and ε-caprolactone. The synthesis of poly(ε-caprolactone)-graft- poly(2-(2-(2-(2-azidoethoxy) -ethoxy)ethoxy)ethyl methacrylate) was via a grafting-from technique, where poly(caprolactone) with pendent isobutyryl bromide groups acted as macroinitiator to initiate the ATRP azido monomer to yield the grafted copolymer containing a backbone of poly(caprolactone) and dispersed side chains of poly(methacrylate) with multiple azido groups. Finally, pre-prepared prop-2-ynyle phosphatidylcholine (CP monomer) was clicked onto the above grafted copolymer via the reaction between the pendent azido groups of the copolymer and the alkyne group of CP monomer. The CP monomer (prop-2-ynyle phosphatidylcholine) was prepared following our previously reported method[1]. The designed copolymers were characterized with NMR and FTIR to determine the MW and presence of functional groups and the electrospun web with SEM. Results and Discussion: Human RBCs incubated with the CP web formed a uniform layer on the mat surface attributed to multivalent interactions between CP groups on the web and PC groups on the cell membrane, demonstrating the material’s potential for blood conservation and sealing. Incubation in isotonic whole blood with reduced ionic strength resulted in enhanced adhesion and supports an electrostatic mechanism for the CP-PC association. Conclusion: We anticipate that this functional fiber mat will prove to be a fundamentally new and effective biomaterial for wound dressing and blood conservation practice.