Dynamics of an aqueous suspension of short hyaluronic acid chains near a DPPC bilayer.

The synergy between hyaluronic acid (HA) and lipid molecules plays a crucial role in synovial fluids, cell coatings, etc. Diseased cells in cancer and arthritis show changes in HA concentration and chain size, impacting the viscoelastic and mechanical properties of the cells. Although the solution behavior of HA is known in experiments, a molecular-level understanding of the role of HA in the dynamics at the interface of HA-water and the cellular boundary is lacking. Here, we perform atomistic molecular dynamics simulation of short HA chains in an explicit water solvent in the presence of a DPPC bilayer, relevant in pathological cases. We identify a stable interface between HA-water and the bilayer where the water molecules are in contact with the bilayer and the HA chains are located away without any direct contact. Both translation and rotation of the interfacial waters in contact with the lipid bilayer and translation of the HA chains exhibit subdiffusive behavior. The diffusive behavior sets in slightly away from the bilayer, where the diffusion coefficients of water and HA decrease monotonically with increase in HA concentration. On the contrary, the dependence on HA chain size is only marginal due to enhanced chain flexibility as their size increases.

Effects induced by η6-p-cymene ruthenium(II) complexes on Langmuir monolayers mimicking cancer and healthy cell membranes do not correlate with their toxicity.

The mechanism of chemotherapeutic action of Ru-based drugs involves plasma membrane disruption and valuable insights into this process may be gained using cell membrane models. The interactions of a series of cytotoxic η6-p-cymene ruthenium(II) complexes, [Ru(η6-p-cymene)P(3,5-C(CH3)3-C6H3)3Cl2] (1), [Ru(η6-p-cymene)P(3,5-CH3-C6H3)3Cl2] (2), [Ru(η6-p-cymene)P(4-CH3O-3,5-CH3-C6H2)3Cl2] (3), and [Ru(η6-p-cymene)P(4-CH3O-C6H4)3Cl2] (4), were examined using Langmuir monolayers as simplified healthy and cancerous outer leaflet plasma membrane models. The cancerous membrane (CM1 and CM2) models contained either 40 % 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 30 % cholesterol (Chol), 20 % 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and 10 % 1,2-dipalmitoyl-sn-glycero-3-phospho-l-serine (DPPS). Meanwhile, the healthy membrane (HM1 and HM2) models were composed of 60 % DPPC or DOPC, 30 % Chol and 10 % DPPE. The complexes affected surface pressure isotherms and decreased compressional moduli of cancerous and healthy membrane models, interacting with the monolayers headgroup and tails according to data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). However, the effects did not correlate with the toxicity of the complexes to cancerous and healthy cells. Multidimensional projection technique showed that the complex (1) induced significant changes in the CM1 and HM1 monolayers, though it had the lowest cytotoxicity against cancer cells and is not toxic to healthy cells. Moreover, the most toxic complexes (2) and (4) were those that least affected CM2 and HM2 monolayers. The findings here support that the ruthenium complexes interact with lipids and cholesterol in cell membrane models, and their cytotoxic activities involve a multifaceted mode of action beyond membrane disruption.

Porphysome Engineered With Specific Protein Binding Sites as a Multimodal Theranostic Nanocarrier for Targeted Protein Delivery.

The immobilization of proteins on the surface of carriers is challenging due to the loss of protein structure and function in this process. Here, we report the development of the protein immobilization on the surface of the metallated-porphyrin complex in the porphysome nanocarrier. The conjugated Ni-porphyrin to fatty acid (as a tail) has been synthesized and independently placed at the depth of the bilayer center of Dipalmitoylphosphatidylcholine (DPPC) in which the Ni-porphyrin was at the polar region of the membrane and is thus superficial. This porphysome (DPPC: Ni-porphyrin, 4 : 1 mole ratio) was formed by supramolecular self-assembly with a diameter of 173±7 nm and zeta potential -8.5±3.4 mv, which exhibited no significant toxicity at the experimental concentrations and acceptable cellular uptake on MCF-7 cells. The physicochemical properties and specific protein binding sites of the firefly luciferase as a model protein into the porphysome (1 : 2 mole ratio) show the conjugation efficiency about 80 % and the conformation of protein was completely maintained. Furthermore, bioluminescence assay and SDS-PAGE confirmed the preservation of protein function. The stabilized platform of porphyrin-lipid structure can potentially improve the efficacy of protein functionality for a particular display, shifting porphysomes from a simple carrier to a therapeutic agent.

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.

Study transport of hesperidin based on the DPPC lipid model and the BSA transport model.

Hesperidin (HE), a significant flavonoid polyphenolic compound present in citrus plants, exhibits diverse pharmacological effects. Considering the crucial involvement of biological membranes and transporter proteins in the transportation and biological processes of HE, it becomes essential to comprehend the potential mechanisms through which HE interacts with membranes and transporter proteins. In order to simulate the process of active molecule transport, a cell membrane model consisting of 1,2-dipalmitoyl-n-glycero-3-phosphatidylcholine (DPPC) and a transporter protein model of bovine serum albumin (BSA) were employed for investigation. The present study aimed to investigate the mechanism of action of hesperidin (HE) in DPPC and BSA using fluorescence quenching, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The localization and interaction of HE within liposomes were also elucidated. Furthermore, the binding of BSA and HE was analyzed through UV/Vis absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, and computational biology techniques. Computational biology analysis revealed that the binding between HE and BSA primarily occurred via hydrogen bonding and hydrophobic interactions. This study aimed to investigate the role and mechanism of HE in the DPPC cell membrane model and the BSA transporter protein model, thereby offering novel insights into the action of HE in DPPC and BSA.

Effect of cationic dendrimer on membrane mimetic systems in the form of monolayer and bilayer.

Interactions between a zwitterionic phospholipid, 1, 2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and four anionic phospholipids dihexadecyl phosphate (DHP), 1, 2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG), 1, 2-dipalmitoyl-sn-glycero-3-phosphate (DPP) and 1, 2-dipalmitoyl-sn-glycero-3-phospho ethanol (DPPEth) in combination with an additional amount of 30 mol% cholesterol were separately investigated at air-buffer interface through surface pressure (π) - area (A) measurements. π-A isotherm derived parameters revealed maximum negative deviation from ideality for the mixtures comprising 30 mol% anionic lipids. Besides the film functionality, structural changes of the monomolecular films at different surface pressures in the absence and presence of polyamidoamine (PAMAM, generation 4), a cationic dendrimer, were visualised through Brewster angle microscopy and fluorescence microscopic studies. Fluidity/rigidity of monolayers were assessed by surface dilatational rheology studies. Effect of PAMAM on the formation of adsorbed monolayer, due to bilayer disintegration of liposomes (DPPC:anionic lipids= 7:3 M/M, and 30 mol% cholesterol) were monitored by surface pressure (π) - time (t) isotherms. Bilayer disintegration kinetics were dependent on lipid head group and chain length, besides dendrimer concentration. Such studies are considered to be an in vitro cell membrane model where the alteration of molecular orientation play important roles in understanding the nature of interaction between the dendrimer and cell membrane. Liposome-dendrimer aggregates were nontoxic to breast cancer cell line as well as in doxorubicin treated MDA-MB-468 cell line suggesting their potential as drug delivery systems.

The Equilibria of Triterpene Sapogenins-Phosphatidylcholine in Monolayers at the Air/Water Interface.

Sapogenins are the non-sugar parts of saponins (aglycones), high-molecular-weight glycosides linked to one or more sugar side chains. This group of compounds presents many properties, e.g., the potent properties of reducing surface tension and foaming properties, as evidenced by the amphipathic nature of these substances. They are used in the cosmetics industry, the washing and detergent industry, and the food industry. In addition, they have many healing properties. They lower blood cholesterol but are also used to synthesize steroid drugs or hormones. As reported in the literature, saponins also show antitumor activity, leading to cell cycle inhibition and apoptosis of various neoplastic cells. In this study, the influence of two sapogenins: asiatic acid (AA) and oleanolic acid (OA), on the properties of monolayers made of phosphatidylcholine (DPPC) was investigated. The method used in these studies was the Langmuir method with Brewster angle microscopy. The interactions between the tested compounds in mixed monolayers were described. Using mathematical equations, we established that oleanolic acid and asiatic acid formed complexes with DPPC at 1:1 ratios, characterized by high stability constants. We derived the parameters characterizing the formed complexes and described the phase transitions that occur during the formation of pure and mixed monolayers.

Investigation of the Membrane Localization and Interaction of Selected Flavonoids by NMR and FTIR Spectroscopy.

In this report, we discuss the effects of undescribed flavone derivatives, HZ4 and SP9, newly isolated from the aerial parts of Hottonia palustris L. and Scleranthus perennis L. on membranes. Interaction of flavonoids with lipid bilayers is important for medicinal applications. The experiments were performed with FTIR and NMR techniques on liposomes prepared from DPPC (dipalmitoylphosphatidylcholine) and EYPC (egg yolk phosphatidylcholine). The data showed that the examined polyphenols incorporate into the polar head group region of DPPC phospholipids at both 25 °C and 45 °C. At the lower temperature, a slight effect in the spectral region of the ester carbonyl group is observed. In contrast, at 45 °C, both compounds bring about the changes in the spectral regions attributed to antisymmetric and symmetric stretching vibrations of CH2 and CH3 moieties. Similarly, as in DPPC lipids, the tested compounds interact with the fingerprint region of the polar head groups of the EYPC lipids and cause its reorganization. The outcomes obtained by NMR analyses confirmed the localization of both flavonoids in the polar heads zone. Unraveled effects of HZ4 and SP9 in respect to lipid bilayers can partly determine their biological activities and are crucial for their usability in medicine as disease-preventing phytochemicals.

Doxorubicin Interaction with Lipid Monolayers Leads to Decreased Membrane Stiffness when Experiencing Compression-Expansion Dynamics.

Physical membrane models permit to study and quantify the interactions of many external molecules with monitored and simplified systems. In this work, we have constructed artificial Langmuir single-lipid monolayers with dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE), dipalmitoylphosphatidylserine (DPPS), or sphingomyelin to resemble the main lipid components of the mammalian cell membranes. We determined the collapse pressure, minimum area per molecule, and maximum compression modulus (Cs-1) from surface pressure measurements in a Langmuir trough. Also, from compression/expansion isotherms, we estimated the viscoelastic properties of the monolayers. With this model, we explored the membrane molecular mechanism of toxicity of the well-known anticancer drug doxorubicin, with particular emphasis in cardiotoxicity. The results showed that doxorubicin intercalates mainly between DPPS and sphingomyelin, and less between DPPE, inducing a change in the Cs-1 of up to 34% for DPPS. The isotherm experiments suggested that doxorubicin had little effect on DPPC, partially solubilized DPPS lipids toward the bulk of the subphase, and caused a slight or large expansion in the DPPE and sphingomyelin monolayers, respectively. Furthermore, the dynamic viscoelasticity of the DPPE and DPPS membranes was greatly reduced (by 43 and 23%, respectively), while the reduction amounted only to 12% for sphingomyelin and DPPC models. In conclusion, doxorubicin intercalates into the DPPS, DPPE, and sphingomyelin, but not into the DPPC, membrane lipids, inducing a structural distortion that leads to decreased membrane stiffness and reduced compressibility modulus. These alterations may constitute a novel, early step in explaining the doxorubicin mechanism of action in mammalian cancer cells or its toxicity in non-cancer cells, with relevance to explain its cardiotoxicity.

Interaction mechanism of egg derived peptides RVPSL and QIGLF with dipalmitoyl phosphatidylcholine membrane: microcalorimetric and molecular dynamics simulation studies.

BACKGROUND: Egg-derived peptides are becoming increasingly popular due to their biological activity and non-toxic effects. The egg-derived peptides Arg-Val-Pro-Ser-Leu (RVPSL) and Gln-Ile-Gly-Leu-Phe (QIGLF) display strong angiotensin-converting enzyme inhibitory activity and they can be taken up by intestinal epithelial cells. The interaction of the egg-derived peptides RVPSL and QIGLF with the membrane remains unclear. RESULTS: The position and structure of the peptides in the membrane were calculated. The maximum density values of RVPSL and QIGLF were 2.27 and 1.22 nm from the center of the 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) membrane, respectively, indicating that peptides penetrated the membrane-water interface and were embedded in the membrane. The interaction of RVPSL and QIGLF with the DPPC membrane did not affect the average area per lipid or the lipid sequence parameters. The thermodynamic parameters ΔH, ΔG, and ΔS of the interaction between the peptide RVPSL with the DPPC membrane were 17.91 kJ mol-1 , -17.63 kJ mol-1 , 187.5 J mol-1 ·k-1 , respectively. The thermodynamic parameters ΔH, ΔG, and ΔS of the interaction between peptide QIGLF with DPPC membrane were 17.10 kJ mol-1 , -17.12 kJ mol-1 , 114.8 J mol-1 ·k-1 , respectively. CONCLUSION: The results indicated that the binding of peptides RVPSL and QIGLF to DPPC is an endothermic, spontaneous, and entropy-driven reaction. The results of the study are relevant to the problem of the low bioavailability of bioactive peptides (BP). © 2023 Society of Chemical Industry.

Interaction of neutral and protonated Tamoxifen with the DPPC lipid bilayer using molecular dynamics simulation.

Tamoxifen as an antiestrogen is successfully applied for the clinical treatment of breast cancer in pre- and post-menopausal women. Due to the side effects related to the oral administration of Tamoxifen (such as deep vein thrombosis, pulmonary embolism, hot flushes, ocular disturbances and some types of cancer), liposomal drug delivery is recommended for taking this drug. Drug encapsulation in a liposomal or lipid drug delivery system improves the pharmacokinetic and pharmacodynamic properties. In this regard, we carried out 200-ns molecular dynamics (MD) simulations for three systems (pure DPPC and neutral and protonated Tamoxifen-loaded DPPC). Here, DPPC is a model lipid bilayer to provide us with conditions like liposomal drug delivery systems to investigate the interactions between Tamoxifen and DPPC lipid bilayers and to estimate the preferred location and orientation of the drug molecule inside the bilayer membrane. Properties such as area per lipid, membrane thickness, lateral diffusion coefficient, order parameters and mass density, were surveyed. With insertion of neutral and protonated Tamoxifen inside the DPPC lipid bilayers, area per lipid and membrane thickness increased slightly. Also, Tamoxifen induce ordering of the hydrocarbon chains in DPPC bilayer. Analysis of MD trajectories shows that neutral Tamoxifen is predominantly found in the hydrophobic tail region, whereas protonated Tamoxifen is located at the lipid-water interface (polar region of DPPC lipid bilayers).

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-1ß. 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.

Unsaturation pattern of phosphatidylglycerols modulating the interaction of lysicamine with cells membrane models at the air-water interface.

Lysicamine, an alkaloid with tumorigenic activity, was incorporated in cell membrane models made of lipid Langmuir monolayers. Dipalmitoylphosphocholine (DPPC), dioleoylphosphocholine (DOPC), and palmitoyloleoylcholine (POPC) represented non-tumorigenic cell membranes, and dipalmitoylphosphoserine (DPPS), dioleoylphosphoserine (DOPS), and palmitoyloleoylserine (POPS), tumorigenic ones. The monolayers were characterized by tensiometry, infrared spectroscopy, and Brewster Angle Microscopy (BAM). No significant shifts of the isotherms were observed for the saturated lipids (DPPC and DPPS), while for the others (DOPC, POPS, DOPS, and POPS), more significant changes were observed not only in the compression isotherms but also in the surface pressure-time curve for pre-compressed monolayers. The molecular organization, as well as the morphology of the drug-lipid monolayers, could be inferred with infrared spectroscopy and BAM. While the first revealed that the alkyl chain ordering changed upon lysicamine incorporation, the second showed how the drug could distinctly change the state of aggregation of molecular domains at the air-water interface. In conclusion, lysicamine could interact distinctly with each lipid at the air-water interface, showing the dependence not only on the lipid polar groups but also on the level of unsaturation of the alkyl chains.

Total Internal Reflection Raman Spectra of Alamethicin Interacting with Supported Lipid Bilayers at a Silica/Water Interface.

We report total internal reflection (TIR)-Raman spectroscopy to study intermolecular interactions between membrane-binding peptides and lipid bilayer membranes. The method was applied to alamethicin (ALM), a model peptide for channel proteins, interacting with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer membranes at a silica/water interface. After a dimethyl sulfoxide (DMSO) solution of ALM was added into the water subphase of the DPPC/DPPC bilayer, Raman signals in the CH stretching region increased in intensity reflecting the appearance of the Raman bands due to ALM and DMSO. To identify ALM-dependent spectral changes, we removed DPPC and DMSO contributions from the Raman spectra. We first subtracted the spectrum of the DPPC bilayer from those after the addition of the ALM solution. The contribution of DMSO was then removed by subtracting a DMSO spectrum from the resultant spectra. The DMSO spectrum was obtained in a similar way from a control experiment where DMSO alone was added into the subphase. With the use of this double difference approach, the ALM-dependent changes were successfully obtained. Experiments with DPPC bilayers with deuterated acyl chains revealed that most of the spectral change observed after the addition of ALM was due to the vibrational bands of ALM, not originated from ALM-induced conformational changes of the lipid bilayers.

Mineralization Profile of Annexin A6-Harbouring Proteoliposomes: Shedding Light on the Role of Annexin A6 on Matrix Vesicle-Mediated Mineralization.

The biochemical machinery involved in matrix vesicles-mediated bone mineralization involves a specific set of lipids, enzymes, and proteins. Annexins, among their many functions, have been described as responsible for the formation and stabilization of the matrix vesicles' nucleational core. However, the specific role of each member of the annexin family, especially in the presence of type-I collagen, remains to be clarified. To address this issue, in vitro mineralization was carried out using AnxA6 (in solution or associated to the proteoliposomes) in the presence or in the absence of type-I collagen, incubated with either amorphous calcium phosphate (ACP) or a phosphatidylserine-calcium phosphate complex (PS-CPLX) as nucleators. Proteoliposomes were composed of 1,2-dipalmitoylphosphatidylcholine (DPPC), 1,2-dipalmitoylphosphatidylcholine: 1,2-dipalmitoylphosphatidylserine (DPPC:DPPS), and DPPC:Cholesterol:DPPS to mimic the outer and the inner leaflet of the matrix vesicles membrane as well as to investigate the effect of the membrane fluidity. Kinetic parameters of mineralization were calculated from time-dependent turbidity curves of free Annexin A6 (AnxA6) and AnxA6-containing proteoliposomes dispersed in synthetic cartilage lymph. The chemical composition of the minerals formed was investigated by Fourier transform infrared spectroscopy (FTIR). Free AnxA6 and AnxA6-proteoliposomes in the presence of ACP were not able to propagate mineralization; however, poorly crystalline calcium phosphates were formed in the presence of PS-CPLX, supporting the role of annexin-calcium-phosphatidylserine complex in the formation and stabilization of the matrix vesicles' nucleational core. We found that AnxA6 lacks nucleation propagation capacity when incorporated into liposomes in the presence of PS-CPLX and type-I collagen. This suggests that AnxA6 may interact either with phospholipids, forming a nucleational core, or with type-I collagen, albeit less efficiently, to induce the nucleation process.

Curcumin Accelerates the Lateral Motion of DPPC Membranes.

Curcumin, the main ingredient in turmeric, has attracted attention due to its potential anti-inflammatory, anticancer, wound-healing, and antioxidant properties. Though curcumin efficacy is related to its interaction with biomembranes, there are few reports on the effects of curcumin on the lateral motion of lipids, a fundamental process in the cell membrane. Employing the quasielastic neutron scattering technique, we explore the effects of curcumin on the lateral diffusion of the dipalmotylphosphatidylcholine (DPPC) membrane. Our investigation is also supported by Fourier transform infrared spectroscopy, dynamic light scattering, and calorimetry to understand the interaction between curcumin and the DPPC membrane. It is found that curcumin significantly modulates the packing arrangement and conformations of DPPC lipid, leading to enhanced membrane dynamics. In particular, we find that the presence of curcumin substantially accelerates the DPPC lateral motion in both ordered and fluid phases. The effects are more pronounced in the ordered phase where the lateral diffusion coefficient increases by 23% in comparison to 9% in the fluid phase. Our measurements provide critical insights into molecular mechanisms underlying increased lateral diffusion. In contrast, the localized internal motions of DPPC are barely altered, except for a marginal enhancement observed in the ordered phase. In essence, these findings indicate that curcumin is favorably located at the membrane interface rather than in a transbilayer configuration. Further, the unambiguous evidence that curcumin modulates the membrane dynamics at a molecular level supports a possible action mechanism in which curcumin can act as an allosteric regulator of membrane functionality.

Molecular dynamics simulation of drug delivery across the cell membrane by applying gold nanoparticle carrier: Flutamide as hydrophobic and glutathione as hydrophilic drugs as the case studies.

In this study, molecular dynamics simulation is applied to investigate drug transport in both pure state and conjugated with neutral gold nanoparticle (AuNP) as a drug carrier inside dipalmitoylphosphatidylcholine (DPPC) membrane. Flutamide (Flu) as a hydrophobic and Glutathione (GSH) as a hydrophilic anticancer drug are selected as the case studies. Dynamics of each drug including adhesion on and penetration into the cell membrane are investigated. Pure and conjugated form of drugs inside the water and near the membrane are studied. Simulation results show that the interaction between drug molecules and DPPC changes after drug conjugating with AuNP. GSH, as a hydrophilic drug, intends to remain above the membrane bilayer and after conjugating with AuNP diffuses inside DPPC. However, hydrophobic Flu molecule likes to diffuse inside DPPC, but after conjugating with AuNP, its diffusion inside the lipid bilayer decreases, and its retention time at the surface of DPPC increases. Presence of Flu-NP at the surface of DPPC could enhance its impact on blocking dihydrotestosterone binding at androgen receptors resulting in tumor cell growth arrest. In addition, the tendency of GSH-NP for diffusion to the DPPC is a positive factor for the successful transport of heavy metals such as AuNP without rapid clearance through either the hepatobiliary pathway or the renal system. In conclusion, such MD simulation results may solve problems in nanomedicine translation and turn into a bridge toward maximizing targeting and minimizing nanotoxicity of metal NPs.

Interactions between curcumin and cell membrane models by Langmuir monolayers.

Studying interactions between potential anticancer drugs and cell membrane models is of great interest to explore the capability of novel drugs in the development of anticancer treatments. Lipid membrane models are useful to understand cellular interactions and to discern drug mechanism action. Here, the interactions of curcumin, as a bioactive natural compound with anti-cancer properties, with both healthy and cancerous or tumor cell membrane models, based on Langmuir monolayers, have been studied. The healthy-cell membrane model is composed of cholesterol 67%, and saturated lipid dipalmitoylphosphatidylcholine 33%. The cancerous-cell-membrane-model is composed of a lower proportion of cholesterol, 25%, and unsaturated lipid sphingomyelin 75%. To compare their interaction with curcumin we report the compression isotherms registered for both lipid membrane models and curcumin in different proportions, their compression moduli and the thermodynamic interaction parameters. From this analysis, we evidence a destabilizing interaction between curcumin and the cancerous cell membrane model in comparison with the healthy one. This interaction is further visualized by micro-Brewster Angle and Atomic Force Microscopies. Our experiments show that the drug enhances cohesion in the healthy membrane model whereas it fluidifies the cancerous cell membrane model causing thermodynamic destabilization. These are useful results to improve the selectivity of the drug avoiding adverse side effects of most current anticancer therapies.

Trans-Resveratrol Decreases Membrane Water Permeability: A Study of Cholesterol-Dependent Interactions.

Resveratrol (RSV), a biologically active plant phenol, has been extensively investigated for cancer prevention and treatment due to its ability to regulate intracellular targets and signaling pathways which affect cell growth and metastasis. The non-specific interactions between RSV and cell membranes can modulate physical properties of membranes, which in turn can affect the conformation of proteins and perturb membrane-hosted biological functions. This study examines non-specific interactions of RSV with model membranes having varying concentrations of cholesterol (Chol), mimicking normal and cancerous cells. The perturbation of the model membrane by RSV is sensed by changes in water permeability parameters, using Droplet Interface Bilayer (DIB) models, thermotropic properties from Differential Scanning Calorimetry, and structural properties from confocal Raman spectroscopy, all of which are techniques not complicated by the use of probes which may themselves perturb the membrane. The nature and extent of interactions greatly depend on the presence and absence of Chol as well as the concentration of RSV. Our results indicate that the presence of RSV decreases water permeability of lipid membranes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), indicating a capability for RSV in stiffening fluidic membranes. When Chol is present, however, (at 4:1 and 2:1 mol ratio DOPC to cholesterol), the addition of RSV has no significant effect upon the water permeability. DSC thermograms show that RSV interacts with DOPC and DOPC/Chol bilayers and influences their thermotropic phase behavior in a concentration-dependent manner, by decreasing the main phase transition temperature and enthalpy, with a phase separation shown at the higher concentrations of RSV. Raman spectroscopic studies indicate an ordering effect of RSV on DOPC supported bilayer, with a lesser extent of ordering in the presence of Chol. Combined results from these investigations highlight a differential effect of RSV on Chol-free and Chol-enriched membranes, respectively, which results constitute a bellwether for increased understanding and effective use of resveratrol in disease therapy including cancer.

Effect of biphosphate salt on dipalmitoylphosphatidylcholine bilayer deformation by Tat polypeptide.

Translocation of positively charged cell penetrating peptides (CPP) through cell membrane is important in drug delivery. Here we report all-atom molecular dynamics simulations to investigate how a biphosphate salt in a solvent affects the interaction of a CPP, HIV-1 Tat peptide with model dipalmitoylphosphatidylcholine (DPPC) lipid bilayer. Tat peptide has a large number of basic arginines and a couple of polar glutamines. We observe that in absence of salt, the basic residues of the polypeptide get localized in the vicinity of the membrane without altering the bilayer properties much; polypeptide induce local thinning of the bilayer membrane at the area of localization. In presence of biphosphate salt, the basic residues, dressed by the biphosphate ions, are repelled by the phosphate head groups of the lipid molecules. However, polar glutamine prefers to stay in the vicinity of the bilayer. This leads to larger local bilayer thickness at the contact point by the polar residue and non-uniform bilayer thickness profile. The thickness deformation of bilayer structure disappears upon mutating the polar residue, suggesting importance of the polar residue in bilayer deformation. Our studies point to control bilayer deformation by appropriate peptide sequence and solvent conditions.