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1.
Biochim Biophys Acta Biomembr ; 1864(1): 183812, 2022 02 01.
Article in English | MEDLINE | ID: mdl-34743950

ABSTRACT

Lipid-porphyrin conjugates are considered nowadays as promising building blocks for the conception of drug delivery systems with multifunctional properties such as photothermal therapy (PTT), photodynamic therapy (PDT), phototriggerable release, photoacoustic and fluorescence imaging. For this aim, we have recently synthesized a new lipid-porphyrin conjugate named PhLSM. This was obtained by coupling pheophorbide-a (Pheo-a), a photosensitizer derived from chlorophyll-a, to egg lyso-sphingomyelin. The pure PhLSMs were able to self-assemble into vesicle-like structures that were however not stable and formed aggregates with undefined structures due to the mismatch between the length of the alkyl chain in sn-1 position and the adjacent porphyrin. Herein, stable PhLSMs lipid bilayers were achieved by mixing PhLSMs with cholesterol which exhibits a complementary packing parameter. The interfacial behavior as well as the fine structures of their equimolar mixture was studied at the air/buffer interface by the mean of Langmuir balance and x-ray reflectomerty (XRR) respectively. Our XRR analysis unraveled the monolayer thickening and the increase in the lateral ordering of PhLSM molecules. Interestingly, we could prepare stable vesicles with this mixture that encapsulate hydrophilic fluorescent probe. The light-triggered release kinetics and the photothermal conversion were studied. Moreover, the obtained vesicles were photo-triggerable and allowed the release of an encapsulated cargo in an ON-OFF fashion.


Subject(s)
Drug Delivery Systems , Lipids/chemistry , Phospholipids/chemistry , Porphyrins/chemistry , Chlorophyll/analogs & derivatives , Chlorophyll/chemical synthesis , Chlorophyll/chemistry , Cholesterol/chemistry , Humans , Hydrophobic and Hydrophilic Interactions/radiation effects , Kinetics , Light , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Lipids/chemical synthesis , Lipids/radiation effects , Lipids/therapeutic use , Liposomes/chemistry , Liposomes/radiation effects , Liposomes/therapeutic use , Phospholipids/chemical synthesis , Phospholipids/pharmacology , Phospholipids/radiation effects , Photochemotherapy/trends , Photosensitizing Agents/chemical synthesis , Photosensitizing Agents/chemistry , Photosensitizing Agents/radiation effects , Photothermal Therapy/trends , Porphyrins/chemical synthesis , Porphyrins/radiation effects , Porphyrins/therapeutic use
2.
J Photochem Photobiol B ; 224: 112320, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34600201

ABSTRACT

Membrane proteins can be regulated by alterations in material properties intrinsic to the hosting lipid bilayer. Here, we investigated whether the reversible photoisomerization of bilayer-embedded diacylglycerols (OptoDArG) with two azobenzene-containing acyl chains may trigger such regulatory events. We observed an augmented open probability of the mechanosensitive model channel gramicidin A (gA) upon photoisomerizing OptoDArG's acyl chains from trans to cis: integral planar bilayer conductance brought forth by hundreds of simultaneously conducting gA dimers increased by typically >50% - in good agreement with the observed increase in single-channel lifetime. Further, (i) increments in the electrical capacitance of planar lipid bilayers and protrusion length of aspirated giant unilamellar vesicles into suction pipettes, as well as (ii) changes of small-angle X-ray scattering of multilamellar vesicles indicated that spontaneous curvature, hydrophobic thickness, and bending elasticity decreased upon switching from trans- to cis-OptoDArG. Our bilayer elasticity model for gA supports the causal relationship between changes in gA activity and bilayer material properties upon photoisomerization. Thus, we conclude that photolipids are deployable for converting bilayers of potentially diverse origins into light-gated actuators for mechanosensitive proteins.


Subject(s)
Gramicidin/chemistry , Ion Channels/radiation effects , Light , Lipid Bilayers/radiation effects , Ion Channels/chemistry , Isomerism , Lipid Bilayers/chemistry , Membrane Proteins/chemistry , Scattering, Small Angle , X-Ray Diffraction
3.
Adv Sci (Weinh) ; 8(11): e2004068, 2021 06.
Article in English | MEDLINE | ID: mdl-34105299

ABSTRACT

Resealing of membrane pores is crucial for cell survival. Membrane surface charge and medium composition are studied as defining regulators of membrane stability. Pores are generated by electric field or detergents. Giant vesicles composed of zwitterionic and negatively charged lipids mixed at varying ratios are subjected to a strong electric pulse. Interestingly, charged vesicles appear prone to catastrophic collapse transforming them into tubular structures. The spectrum of destabilization responses includes the generation of long-living submicroscopic pores and partial vesicle bursting. The origin of these phenomena is related to the membrane edge tension, which governs pore closure. This edge tension significantly decreases as a function of the fraction of charged lipids. Destabilization of charged vesicles upon pore formation is universal-it is also observed with other poration stimuli. Disruption propensity is enhanced for membranes made of lipids with higher degree of unsaturation. It can be reversed by screening membrane charge in the presence of calcium ions. The observed findings in light of theories of stability and curvature generation are interpreted and mechanisms acting in cells to prevent total membrane collapse upon poration are discussed. Enhanced membrane stability is crucial for the success of electroporation-based technologies for cancer treatment and gene transfer.


Subject(s)
Cell Membrane/chemistry , Cell Survival/genetics , Lipid Bilayers/chemistry , Lipids/chemistry , Calcium/pharmacology , Cell Membrane/genetics , Detergents/pharmacology , Electromagnetic Fields/adverse effects , Electroporation , Humans , Lipid Bilayers/radiation effects , Porosity/drug effects , Porosity/radiation effects , Surface Properties
4.
Chemistry ; 27(9): 3013-3018, 2021 Feb 10.
Article in English | MEDLINE | ID: mdl-32743875

ABSTRACT

Photosystem I (PS I) is a transmembrane protein that assembles perpendicular to the membrane, and performs light harvesting, energy transfer, and electron transfer to a final, water-soluble electron acceptor. We present here a supramolecular model of it formed by a bicationic oligofluorene 12+ bound to the bisanionic photoredox catalyst eosin Y (EY2- ) in phospholipid bilayers. According to confocal microscopy, molecular modeling, and time dependent density functional theory calculations, 12+ prefers to align perpendicularly to the lipid bilayer. In presence of EY2- , a strong complex is formed (Ka =2.1±0.1×106 m-1 ), which upon excitation of 12+ leads to efficient energy transfer to EY2- . Follow-up electron transfer from the excited state of EY2- to the water-soluble electron donor EDTA was shown via UV-Vis absorption spectroscopy. Overall, controlled self-assembly and photochemistry within the membrane provides an unprecedented yet simple synthetic functional mimic of PS I.


Subject(s)
Energy Transfer/radiation effects , Light , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Phospholipids/chemistry , Phospholipids/radiation effects , Photosystem I Protein Complex/radiation effects , Electron Transport/radiation effects , Photochemistry
5.
Ultrasound Med Biol ; 46(9): 2370-2387, 2020 09.
Article in English | MEDLINE | ID: mdl-32616427

ABSTRACT

The nonlinear acoustic properties of microbubble ultrasound enhancing agents have allowed for the development of subharmonic, second harmonic, and contrast-pulse sequence ultrasound imaging modes, which enhance the quality, reduce the noise, and improve the diagnostic capabilities of clinical ultrasound. This study details acoustic scattering responses of perfluorobutane (PFB) microbubbles, an un-nested perfluoropentane (PFP) nanoemulsion, and two nested PFP nanoemulsions-one comprising a negatively charged phospholipid bilayer and another comprising a zwitterionic phospholipid bilayer-when excited at 1 or 2.25 MHz over a peak negative pressure range of 200 kPa to 4 MPa in the absence and presence of a 1-Hz, 1-V/cm electric field. The only sample that exhibited an increase in nonlinear activity in the presence of an electric field at both excitation frequencies was the negatively charged nested PFP nanoemulsion; the most pronounced effect was observed at an excitation of 2.25 MHz. Interestingly, the application of an electric field not only increased the nonlinear acoustic activity of the negatively charged nested PFP nanoemulsion but increased it beyond that seen when the nanoemulsion is un-nested and on the same scale as PFB microbubbles.


Subject(s)
Electricity , Fluorocarbons/pharmacology , Image Enhancement/methods , Microbubbles , Ultrasonic Waves , Acoustics , Lipid Bilayers/radiation effects , Phospholipids/radiation effects
6.
Soft Matter ; 16(13): 3216-3223, 2020 Apr 01.
Article in English | MEDLINE | ID: mdl-32161934

ABSTRACT

Archaeal lipids ensure unprecedented stability of archaea membranes in extreme environments. Here, we incorporate a characteristic structural feature of an archaeal lipid, the cyclopentane ring, into hydrocarbon chains of a short-chain (C12) phosphatidylcholine to explore whether the insertion would allow such a lipid (1,2-di-(3-(3-hexylcyclopentyl)-propanoate)-sn-glycero-3-phosphatidylcholine, diC12cp-PC) to form stable bilayers at room temperature. According to fluorescence-based assays, in water diC12cp-PC formed liquid-crystalline bilayers at room temperature. Liposomes produced from diC12cp-PC retained calcein for over a week when stored at +4 °C. diC12cp-PC could also form model bilayer lipid membranes that were by an order of magnitude more stable to electrical breakdown than egg PC membranes. Molecular dynamics simulation showed that the cyclopentane fragment fixes five carbon atoms (or four C-C bonds), which is compensated by the higher mobility of the rest of the chain. This was found to be the reason for the remarkable stability of the diC12cp-PC bilayer: restricted conformational mobility of a chain segment increases the membrane bending modulus (compared to a normal hydrocarbon chain of the same length). Here, higher stiffness practically does not affect the line tension of a membrane pore edge. Rather it makes it more difficult for diC12cp-PC to rearrange in order to line the edge of a hydrophilic pore; therefore, fewer pores are formed.


Subject(s)
Archaea/chemistry , Cyclopentanes/chemistry , Hydrophobic and Hydrophilic Interactions/drug effects , Phospholipids/chemistry , Electricity/adverse effects , Lipid Bilayers/radiation effects , Liposomes/chemistry , Liposomes/radiation effects , Molecular Conformation/radiation effects , Water/chemistry
7.
Biochim Biophys Acta Biomembr ; 1862(7): 183257, 2020 07 01.
Article in English | MEDLINE | ID: mdl-32147355

ABSTRACT

Pinholins are a family of lytic membrane proteins responsible for the lysis of the cytosolic membrane in host cells of double stranded DNA bacteriophages. Protein-lipid interactions have been shown to influence membrane protein topology as well as its function. This work investigated the interactions of pinholin with the phospholipid bilayer while in active and inactive confirmations to elucidate the different interactions the two forms have with the bilayer. Pinholin incorporated into deuterated DMPC-d54 lipid bilayers, along with 31P and 2H solid state NMR (SS-NMR) spectroscopy were used to probe the protein-lipid interactions with the phosphorus head group at the surface of the bilayer while interactions with the 2H nuclei were used to study the hydrophobic core. A comparison of the 31P chemical shift anisotropy (CSA) values of the active S2168 pinholin and inactive S21IRS pinholin indicated stronger head group interactions for the pinholin in its active form when compared to that of the inactive form supporting the model of a partially externalized peripheral transmembrane domain (TMD) of the active S2168 instead of complete externalized TMD1 as suggested by Ahammad et al. JPC B 2019. The 2H quadrupolar splitting analysis showed a decrease in spectral width for both forms of the pinholin when compared to the empty bilayers at all temperatures. In this case the decrease in the spectral width of the inactive S21IRS form of the pinholin showed stronger interactions with the acyl chains of the bilayer. The presence of the inactive form's additional TMD within the membrane was supported by the loss of peak resolution observed in the 2H NMR spectra.


Subject(s)
Lipid Bilayers/chemistry , Magnetic Resonance Spectroscopy , Membrane Proteins/chemistry , Phospholipids/chemistry , Amino Acid Sequence , Deuterium/chemistry , Lipid Bilayers/radiation effects , Phospholipids/radiation effects
8.
Mol Pharm ; 16(7): 2956-2965, 2019 07 01.
Article in English | MEDLINE | ID: mdl-31084010

ABSTRACT

The controlled release of anticancer drugs at the tumor site is a central challenge in treating cancer. To achieve this goal, our strategy was based on tumor-specific targeting and ultrasound-triggered release of an anticancer agent from liposomal nanocarriers. To enhance the ultrasound-triggered drug release, we incorporated a lipophilic sonosensitizer, chlorin e6 (Ce6) ester, into the lipid bilayer of liposomes. Additionally, asparagine-glycine-arginine (NGR) that binds to CD13, which is overexpressed in tumor cells, was introduced into these liposomes. Under the navigation effects of the NGR, the novel ultrasound-triggerable NGR-modified liposomal nanocarrier (NGR/UT-L) accumulates in tumor sites. Once irradiated by ultrasound in tumor tissues, the sonodynamic effect produced by Ce6 could create more efficient disruptions of the lipid bilayer of the liposomal nanocarriers. After encapsulating doxorubicin (DOX) as the model drug, the ultrasound triggered lipid bilayer breakdown can spring the immediate release of DOX, making it possible for ultrasound-responsive chemotherapy with great selectivity. By combining tumor-specific targeting and stimuli-responsive controlled release into one system, NGR/UT-L demonstrated a perfect antitumor effect. Moreover, this report provides an example of controlled-release by means of a novel class of ultrasound triggering systems.


Subject(s)
Drug Delivery Systems/methods , Drug Liberation/radiation effects , Fibrosarcoma/metabolism , Ultrasonic Waves , Animals , Antibiotics, Antineoplastic/administration & dosage , CD13 Antigens/metabolism , Cell Line, Tumor , Cell Survival/drug effects , Chlorophyllides , Doxorubicin/administration & dosage , Drug Carriers , Fibrosarcoma/drug therapy , Fibrosarcoma/pathology , Humans , Lipid Bilayers/radiation effects , Liposomes/chemistry , Mice , Mice, Nude , Oligopeptides/chemistry , Oligopeptides/metabolism , Porphyrins/chemistry , Radiation-Sensitizing Agents/chemistry , Tumor Burden/drug effects , Xenograft Model Antitumor Assays
9.
Colloids Surf B Biointerfaces ; 173: 312-319, 2019 Jan 01.
Article in English | MEDLINE | ID: mdl-30308456

ABSTRACT

Catechin molecules such as epigallocatechin-3-gallate (EGCG) are capable of attenuating the biomolecular damage induced by UV radiation, possibly through molecular mechanisms involving the cell membranes. In this study, we confirmed the protective role of EGCG against UV of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol) (sodium salt) (DPPG) in liposomes and cast films. The incorporation of EGCG increased the stability of DPPG liposomes as indicated by UV-vis absorption spectra. Using 2D correlation spectroscopy to analyse the spectra, we found that DPPG and EGCG are co-helpers and complement each other against degradation induced by UV. At the molecular level, UV irradiation affects the phosphate and carbonyl groups of DPPG, in addition to triggering the oxidation and opening of the pyrogallol ring of EGCG. Since EGCG can be incorporated into liposomes and is a strong shield against UV radiation, one may envisage its use in anti-ageing and sunscreen creams, and in dermal drug delivery.


Subject(s)
Antioxidants/chemistry , Catechin/analogs & derivatives , Phosphatidylglycerols/chemistry , Radiation-Protective Agents/chemistry , Catechin/chemistry , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Liposomes/chemistry , Liposomes/radiation effects , Oxidation-Reduction , Principal Component Analysis , Ultraviolet Rays
10.
Langmuir ; 34(44): 13368-13374, 2018 11 06.
Article in English | MEDLINE | ID: mdl-30346771

ABSTRACT

Controlling lateral interactions between lipid molecules in a bilayer membrane to guide membrane organization and domain formation is a key factor for studying and emulating membrane functionality in synthetic biological systems. Here, we demonstrate an approach to reversibly control lipid organization, domain formation, and membrane stiffness of phospholipid bilayer membranes using the photoswitchable phospholipid azo-PC. azo-PC contains an azobenzene group in the sn2 acyl chain that undergoes reversible photoisomerization on illumination with UV-A and visible light. We demonstrate that the concentration of the photolipid molecules and also the assembly and disassembly of photolipids into lipid domains can be monitored by UV-vis spectroscopy because of a blue shift induced by photolipid aggregation.


Subject(s)
Lipid Bilayers/chemistry , Membrane Microdomains/radiation effects , Unilamellar Liposomes/chemistry , Azo Compounds/chemical synthesis , Azo Compounds/chemistry , Azo Compounds/radiation effects , Isomerism , Lipid Bilayers/radiation effects , Microscopy, Fluorescence , Phosphatidylcholines/chemical synthesis , Phosphatidylcholines/chemistry , Phosphatidylcholines/radiation effects , Ultraviolet Rays , Unilamellar Liposomes/radiation effects
11.
J Phys Chem B ; 122(29): 7319-7331, 2018 07 26.
Article in English | MEDLINE | ID: mdl-29912560

ABSTRACT

Neural stimulation has widespread applications in investigating brain functions, restoring impaired neural functions, and treating numerous neurological/psychiatric diseases. Use of infrared pulses to stimulate neurons (infrared neural stimulation) offers a direct and non-invasive technique. Recent research has demonstrated that transient heating associated with the absorption of infrared light by the local aqueous medium around the cell membrane can stimulate nerves. One mechanism for this stimulation is due to a thermally induced increase in the membrane electrical capacitance, which causes cell depolarization as well as action potential production under certain physiological conditions. A theoretical and computational model helps better understand the mechanism of thermally induced electrical capacitance changes and optimize the stimulus parameters. In this article, we develop the existing theoretical models for membrane electrical capacitance and its thermally induced changes. We improve the formulation of Gouy-Chapman-Stern theory by Genet et al. and Shapiro et al. with the addition of a diffuse layer to the electrical double layer and by modifying the relation of Stern layer capacitance, to calculate the membrane capacitive charge and capacitive current. We also present a new method to calculate the membrane electrical capacitance and the rate of its thermally induced changes. In our calculations, two new factors are considered including the temperature dependence of the surface charge density and the hydrophobic core dielectric constant of the lipid bilayer. Our developed model predicts rates of 0.3 and 0.26%/°C for the thermally induced capacitance changes of the artificial lipid bilayer under two different sets of conditions previously reported by Shapiro et al. and Carvalho-de-Souza et al., respectively. Our model is in very good agreement with the corresponding experimental values given by these groups. The presented model is also able to calculate the membrane capacitive currents and investigate the voltage dependence of this current.


Subject(s)
Lasers , Lipid Bilayers/chemistry , Models, Theoretical , Electric Capacitance , Lipid Bilayers/radiation effects , Membrane Potentials , Temperature
12.
Colloids Surf B Biointerfaces ; 167: 544-549, 2018 Jul 01.
Article in English | MEDLINE | ID: mdl-29730576

ABSTRACT

Light-initiated fusion between vesicles has attracted much attention in the research community. In particular, fusion between photoresponsive and non-photoresponsive vesicles has been of much interest in the development of systems for the delivery of therapeutic agents to cells. We have performed fusion between giant vesicles (GVs) and photoresponsive smaller vesicles containing malachite green (MG) derivative, which undergoes ionization to afford a positive charge on the molecule by irradiation. The fusion proceeds as the concentration of GV lipid increases toward equimolarity with the lipid of the smaller vesicle. It is also dependent on the molar percentage of photoionized MG in the lipid of the smaller vesicle. On the other hand, the fusion is hardly affected by the anionic component of the GV. The photoinduced fusion was characterized by two methods, involving the mixing of lipid membranes and of aqueous contents. Fluorescence microscopy revealed that irradiation triggered the fusion of a single GV with the smaller vesicles containing MG.


Subject(s)
Lipid Bilayers/radiation effects , Membrane Fusion/radiation effects , Rosaniline Dyes/chemistry , Ultraviolet Rays , Unilamellar Liposomes/radiation effects , Fluorescence Resonance Energy Transfer , Lipid Bilayers/chemistry , Lipid Bilayers/metabolism , Membrane Lipids/chemistry , Membrane Lipids/metabolism , Membrane Lipids/radiation effects , Microscopy, Fluorescence , Unilamellar Liposomes/chemistry , Unilamellar Liposomes/metabolism
13.
Chemistry ; 24(44): 11245-11254, 2018 Aug 06.
Article in English | MEDLINE | ID: mdl-29633378

ABSTRACT

Diarylethene derivatives, the biological activity of which can be reversibly changed by irradiation with light of different wavelengths, have shown promise as scientific tools and as candidates for photocontrollable drugs. However, examples demonstrating efficient photocontrol of their biological activity are still relatively rare. This concept article discusses the possible reasons for this situation and presents a critical analysis of existing data and hypotheses in this field, in order to extract the design principles enabling the construction of efficient photocontrollable diarylethene-based molecules. Papers addressing biologically relevant interactions between diarylethenes and biomolecules are analyzed; however, in most published cases, the efficiency of photocontrol in living systems remains to be demonstrated. We hope that this article will encourage further discussion of design principles, primarily among pharmacologists, synthetic and medicinal chemists.


Subject(s)
Ethylenes/radiation effects , Animals , Azo Compounds/chemistry , Azo Compounds/radiation effects , Ethylenes/chemical synthesis , Histone Deacetylase Inhibitors/chemistry , Histone Deacetylase Inhibitors/radiation effects , Light , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Models, Molecular , Molecular Structure , Photochemical Processes , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/radiation effects , Stereoisomerism
14.
Langmuir ; 33(16): 4083-4089, 2017 04 25.
Article in English | MEDLINE | ID: mdl-28361538

ABSTRACT

Giant unilamellar vesicles (GUVs) represent a versatile model system to emulate the fundamental properties and functions associated with the plasma membrane of living cells. Deformability and shape transitions of lipid vesicles are closely linked to the mechanical properties of the bilayer membrane itself and are typically difficult to control under physiological conditions. Here, we developed a protocol to form cell-sized vesicles from an azobenzene-containing phosphatidylcholine (azo-PC), which undergoes photoisomerization on irradiation with UV-A and visible light. Photoswitching within the photolipid vesicles enabled rapid and precise control of the mechanical properties of the membrane. By varying the intensity and dynamics of the optical stimulus, controlled vesicle shape changes such as budding transitions, invagination, pearling, or the formation of membrane tubes were achieved. With this system, we could mimic the morphology changes normally seen in cells, in the absence of any molecular machines associated with the cytoskeleton. Furthermore, we devised a mechanism to utilize photoswitchable lipid membranes for storing mechanical energy and then releasing it on command as locally usable work.


Subject(s)
Azo Compounds/chemistry , Lipid Bilayers/chemistry , Phosphatidylcholines/chemistry , Unilamellar Liposomes/chemistry , Azo Compounds/chemical synthesis , Azo Compounds/radiation effects , Isomerism , Lipid Bilayers/chemical synthesis , Lipid Bilayers/radiation effects , Phosphatidylcholines/chemical synthesis , Phosphatidylcholines/radiation effects , Ultraviolet Rays , Unilamellar Liposomes/chemical synthesis , Unilamellar Liposomes/radiation effects
15.
Phys Chem Chem Phys ; 19(18): 11460-11473, 2017 May 10.
Article in English | MEDLINE | ID: mdl-28425533

ABSTRACT

Photo-triggerable liposomes are considered nowadays as promising drug delivery devices due to their potential to release encapsulated drugs in a spatial and temporal manner. In this work, we have investigated the photopermeation efficiency of three photosensitizers (PSs), namely verteporfin, pheophorbide a and m-THPP when incorporated into liposomes with well-defined lipid compositions (SOPC, DOPC or SLPC). By changing the nature of phospholipids and PSs, the illumination of the studied systems was shown to significantly alter their lipid bilayer properties via the formation of lipid peroxides. The system efficiency depends on the PS/phospholipid association, and the ability of the PS to peroxidize acyl chains. Our results demonstrated the possible use of these three clinically approved (or under investigation) PSs as potential candidates for photo-triggerable liposome conception.


Subject(s)
Drug Liberation/radiation effects , Liposomes/chemistry , Photosensitizing Agents/chemistry , Chlorophyll/analogs & derivatives , Chlorophyll/chemistry , Chlorophyll/radiation effects , Fluoresceins/chemistry , Fluorescent Dyes/chemistry , Hydrophobic and Hydrophilic Interactions , Light , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Lipid Peroxidation/radiation effects , Liposomes/radiation effects , Mesoporphyrins/chemistry , Mesoporphyrins/radiation effects , Molecular Dynamics Simulation , Permeability , Phosphatidylcholines/chemistry , Phosphatidylcholines/radiation effects , Photosensitizing Agents/radiation effects , Porphyrins/chemistry , Porphyrins/radiation effects , Transition Temperature , Verteporfin
16.
Proc Natl Acad Sci U S A ; 113(19): 5281-6, 2016 May 10.
Article in English | MEDLINE | ID: mdl-27114528

ABSTRACT

Electroporation is a widely used technique to permeabilize cell membranes. Despite its prevalence, our understanding of the mechanism of voltage-mediated pore formation is incomplete; methods capable of visualizing the time-dependent behavior of individual electropores would help improve our understanding of this process. Here, using optical single-channel recording, we track multiple isolated electropores in real time in planar droplet interface bilayers. We observe individual, mobile defects that fluctuate in size, exhibiting a range of dynamic behaviors. We observe fast (25 s(-1)) and slow (2 s(-1)) components in the gating of small electropores, with no apparent dependence on the applied potential. Furthermore, we find that electropores form preferentially in the liquid disordered phase. Our observations are in general supportive of the hydrophilic toroidal pore model of electroporation, but also reveal additional complexity in the interactions, dynamics, and energetics of electropores.


Subject(s)
Electroporation/methods , Lipid Bilayers/chemistry , Lipid Bilayers/radiation effects , Membrane Potentials/radiation effects , Microscopy, Fluorescence/methods , Porosity/radiation effects , Electromagnetic Fields , Kinetics , Materials Testing , Permeability/radiation effects
17.
Sci Rep ; 6: 22686, 2016 Mar 04.
Article in English | MEDLINE | ID: mdl-26940847

ABSTRACT

Lipid membranes are almost impermeable for charged molecules and ions that can pass the membrane barrier only with the help of specialized transport proteins. Here, we report how temperature manipulation at the nanoscale can be employed to reversibly control the electrical resistance and the amount of current that flows through a bilayer membrane with pA resolution. For this experiment, heating is achieved by irradiating gold nanoparticles that are attached to the bilayer membrane with laser light at their plasmon resonance frequency. We found that controlling the temperature on the nanoscale renders it possible to reproducibly regulate the current across a phospholipid membrane and the membrane of living cells in absence of any ion channels.


Subject(s)
Electric Impedance , Hot Temperature , Lipid Bilayers/radiation effects , Membranes/radiation effects , Cell Line , Gold , Humans , Low-Level Light Therapy , Nanoparticles
18.
Langmuir ; 32(6): 1577-84, 2016 Feb 16.
Article in English | MEDLINE | ID: mdl-26794208

ABSTRACT

Polymerization of substrate-supported bilayers composed of dienoylphosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability; however, the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl-phosphatidylcholine (mono-SorbPC), bis-dienoyl-phosphatidylcholine (bis-DenPC), and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lß phase for each lipid. In all cases, polymerization reduced membrane fluidity; however, measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate interleaflet bonding. The D values measured after polymerization were 0.1-0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lß phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.


Subject(s)
Lipid Bilayers/chemistry , Membrane Fluidity/radiation effects , Phosphatidylcholines/chemistry , Phosphatidylethanolamines/chemistry , Rhodamines/chemistry , Diffusion , Fluorescence Recovery After Photobleaching , Lipid Bilayers/radiation effects , Phosphatidylcholines/radiation effects , Phosphatidylethanolamines/radiation effects , Polymerization , Rhodamines/radiation effects , Transition Temperature , Ultraviolet Rays
19.
Biofizika ; 60(5): 936-40, 2015.
Article in Russian | MEDLINE | ID: mdl-26591605

ABSTRACT

Calculations of heating of membrane-forming holes in Teflon film exposed to decimeter waves were performed. The dependence of the temperature increment in holes on the geometry of holes, electrolyte concentration, and decimeter wave frequency was studied. The kinetics of heating depending on the hole diameter was also obtained. It was concluded that the observed in the experiment effects of the decimeter wave on bilayer lipid membranes resulted from the elevated concentration of decimeter electromagnetic waves in membrane-forming hole that led to selective heating of electrolyte in hole and bilayer lipid membranes.


Subject(s)
Cell Membrane/chemistry , Lipid Bilayers/chemistry , Polytetrafluoroethylene/chemistry , Biophysical Phenomena , Cell Membrane/radiation effects , Electromagnetic Radiation , Heating , Kinetics , Lipid Bilayers/radiation effects
20.
Soft Matter ; 11(44): 8641-7, 2015 Nov 28.
Article in English | MEDLINE | ID: mdl-26371704

ABSTRACT

Non-invasive measurement of the membrane tension of free-standing black lipid membranes (BLMs), with sensitivity on the order of µN m(-1), was achieved using laser-induced surface deformation (LISD) spectroscopy. A BLM was vertically formed via the folding method and aqueous phases with different refractive indices were added on each side in order to induce radiation pressure by a laser beam. The dynamic response of the deformed BLMs was measured under periodic intensity modulation and their tensions could be estimated. The dependence of membrane tension on the cholesterol concentration of BLMs composed of phosphatidylcholine and phosphatidylethanolamine was investigated, with the membrane tension increasing from 1.3 µN m(-1) to 68.1 µN m(-1) when the cholesterol concentration increased from zero to 33%. These tension values are much smaller than some of those previously reported, because this method does not suppress membrane fluctuation unlike other conventional methods. Our LISD system can be a promising tool for the measurement of membrane tension in BLMs.


Subject(s)
Lipid Bilayers/chemistry , Cholesterol/chemistry , Lasers , Lipid Bilayers/radiation effects , Phosphatidylcholines/chemistry , Stress, Mechanical
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