Nanozyme technology at Moscow State University. Achievements and development perspectives

The work describes novel functional bionanosystems for treatment and diagnostics on the basis of proteins, enzymes, polymeric coatings, and magnetic nanoparticles developed at Lomonosov Moscow State University Laboratory for Chemical Design of Bionanomaterials in collaboration with scientists from UNC Eshelman School of Pharmacy (USA). The properties of enzymes (superoxide dismutase, catalase, organophosphate hydrolase, and lysines of bacteriophages) and other drug molecules immobilized in polymeric complexes, as well as the methods for targeted drug delivery using cell-mediated systems and magnetic nanoparticles in in vitro and in vivo operating conditions, are discussed. Physical and chemical characteristics, including data on the functional properties of the nanoformulations, are obtained. The nanoformulations developed demonstrated high potential therapeutic efficacy for the treatment of central nervous system and brain diseases, inflammations (including inflammatory diseases of the eye), cancer and infectious diseases, neurotoxic injury, and others. The possibilities of remote control biochemical reactions using a nonheating low-frequency alternating magnetic field (AMF) for the controlled release of drugs are analyzed in the review. The experimental results of the AMF effects on bionanosystems containing magnetic nanoparticles, such as changing the catalytic activities of enzymes bound to magnetic nanoparticles and ‘disordering’ of the lipid bilayer in membranes, are considered.     

Triggered release in lipid bilayer-capped mesoporous silica nanoparticles containing SPION using an alternating magnetic field

We report here the on-command cargo controlled delivery using an alternating magnetic field (AMF) from magnetic silica mesoporous supports capped with a lipid bilayer.     

Interaction of bare and gold-coated superparamagnetic iron oxide nanoparticles with fetal bovine serum

Superparamagnetic iron oxide nanoparticles (SPIONs) are being increasingly used in various biomedical processes such as hyperthermia, cell and protein separation, enhancing resolution of magnetic resonance imaging and drug delivery. Here, SPIONs were prepared by optimized co-precipitation of iron chlorides in basic medium and then coated with gold. Bare SPIONs and Aucoated SPIONs were characterized by TEM before incubation with fetal bovine serum for 0.5, 1, 2, 4, 8 and 24 h. After these interaction times, the mixture was deposed on a small column in a strong magnetic field (MACS?system). The SPIONs were retained; different washing fractions were collected and studied by UV-Vis spectroscopy and by 1D gel electrophoresis. The study revealed the presence of proteins in the washing solutions and confirmed the strong interaction of the protein with the SPIONs.     

基于超顺磁性Fe3O4的磁响应型纳米药物载体的研究进展

基于超顺磁性Fe3O4纳米粒子（SPIONs）磁响应型纳米药物载体已经广泛应用于肿瘤诊断与治疗方面。将SPIONs用多功能性外壳修饰后,能够使其稳定性增加,实现体内长循环,并能缓释出所携带药物;再将其靶向性配体分子复合后,能够提高其肿瘤多靶向的效果;通过将SPIONs用温敏性或光敏性等外壳材料包覆,利用SPIONs的磁致发热、光致发热以及外壳材料自身的特点,能够直接杀死肿瘤细胞或者将温敏性外壳剥落,平稳地释放出药物,提高肿瘤部位的药物浓度,增强治疗效果。因此,本文综述了基于SPIO的磁响应型纳米药物载体在肿瘤治疗领域的新研究与新进展,并进行研究展望,以期为今后相关方面的深入研究提供参考和借鉴。     

Impact of Strong and Weak Lipid–Protein Interactions on the Structure of a Lipid Bilayer on a Gold Electrode Surface

A lipid bilayer deposited on an electrode surface can serve as a benchmark system to investigate lipid–protein interactions in the presence of physiological electric fields. Recoverin and myelin‐associated glycoprotein (MAG) are used to study the impact of strong and weak protein–lipid interactions on the structure of model lipid bilayers, respectively. The structural changes in lipid bilayers are followed using electrochemical polarization modulation infrared reflection–absorption spectroscopy (PM IRRAS). Recoverin contains a myristoyl group that anchors in the hydrophobic part of a cell membrane. Insertion of the protein into the 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphatidylcholine (DMPC)–cholesterol lipid bilayer leads to an increase in the capacitance of the lipid film adsorbed on a gold electrode surface. The stability and kinetics of the electric‐field‐driven adsorption–desorption process are not affected by the interaction with protein. Upon interaction with recoverin, the hydrophobic hydrocarbon chains become less ordered. The polar head groups are separated from each other, which allows for recoverin association in the membrane. MAG is known to interact with glycolipids present on the surface of a cell membrane. Upon probing the interaction of the DMPC–cholesterol–glycolipid bilayer with MAG a slight decrease in the capacity of the adsorbed lipid film is observed. The stability of the lipid bilayer increases towards negative potentials. At the molecular scale this interaction results in minor changes in the structure of the lipid bilayer. MAG causes small ordering in the hydrocarbon chains region and an increase in the hydration of the polar head groups. Combining an electrochemical approach with a structure‐sensitive technique, such as PM IRRAS, is a powerful tool to follow small but significant changes in the structure of a supramolecular assembly.     

Forming Lipid Bilayer Membrane Arrays on Micropatterned Polyelectrolyte Film Surfaces

A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer‐by‐layer technique on a silicon oxide surface modified with a 3‐aminopropyltriethoxysilane (APTES) monolayer. The surface pK_a value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer‐by‐layer assembly. Micropatterned polyelectrolyte films were obtained by deep‐UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm² s^?1 in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field.     

Functionalization of magnetic nanoparticles with dendritic-linear-brush-like triblock copolymers and their drug release properties

Novel water-soluble dendritic-linear-brush-like triblock copolymer polyamidoamine-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PAMAM-b-PDMAEMA-b-PPEGMA)-grafted superparamagnetic iron oxide nanoparticles (SPIONs) were successfully prepared via a two-step copper-mediated atom transfer radical polymerization (ATRP) method. The macroinitiators were immobilized on the surface of Fe(3)O(4) nanoparticles via effective ligand exchange of oleic acid with the propargyl focal point PAMAM-typed dendron (generation 2.0, denoted as propargyl-D(2.0)) containing four carboxyl acid end groups, following a click reaction with 2'-azidoethyl-2-bromoisobutylate (AEBIB). PDMAEMA and PPEGMA were grown gradually from nanoparticle surfaces using the "grafting from" approach, which rendered the SPIONs soluble in water and reversed aggregation. To the best of our knowledge, this is the first report that describes the functionalization of magnetic nanoparticles with dendritic-linear-brush-like triblock copolymers. The modified nanoparticles were systematically studied via TEM, FT-IR, DLS, XRD, NMR, TGA, and magnetization measurements. DLS measurement confirmed that the obtained dendritic-linear-brush-like triblock copolymer-grafted SPIONs had a uniform hydrodynamic particle size of average diameter less than 30 nm. The dendritic-linear-brush-like triblock copolymer-grafted SPIONs possessed excellent biocompatibility by methyl tetrazolium (MTT) assays against NIH3T3 cells and hemolysis assays with rabbit erythrocytes. Furthermore, an anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the dendritic-linear-brush-like triblock copolymer-grafted SPIONs, and subsequently, the drug releases were performed in phosphoric acid buffer solution pH = 4.7, 7.4, or 11.0 at 37 °C. The results verify that the dendritic-linear-brush-like triblock copolymer-grafted SPIONs possess pH-responsive drug release behavior. The Dox dose of the loaded and free drug required for 50% cellular growth inhibition was 2.72 and 0.72 μm/mL, respectively, according to MTT assay against a Hella cell line in vitro. Therefore, on the basis of its biocompatibility and drug release effect, the modified SPION could provide a charming opportunity to design some excellent drug delivery systems for therapeutic applications.     

Ion Channel Behavior of a Supported Bilayer Lipid Membrane Composed of 5,5－Ditetradecyl－2－ （2－trimethyl－ammonioethyl）－l, 3－dioxane Bromide Modified Glassy Carbon Electrode

A synthetic cationic surfactant, 5,5-ditetradecyl-2-(2-trimethyl-ammonioethyl)-l,3-dioxane bromide (DTDB), was used to construct a supported bilayer lipid membrane (s-BLM) coatedon an underlying glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS), small-angle X-ray diffraction (SAXD) and cyclic voltammetry were used to characterize the s-BLM. Both EIS and SAXD data indicated that the synthetic lipid exists as a well-oriented bilayer in the membrane.The voltammetric study showed that the lipid membrane can open ion channels in the presence of ClO4^- stimulant with Ru(bpy)3^2 as marker ions and give distinct channel currents.The channels can be dosed and open up again many times by removing or introducing ClO4^- anions.     

Kinetics and thermodynamics of chlorpromazine interaction with lipid bilayers: effect of charge and cholesterol

Passive transport across cell membranes is the major route for the permeation of xenobiotics through tight endothelia such as the blood–brain barrier. The rate of passive permeation through lipid bilayers for a given drug is therefore a critical step in the prediction of its pharmacodynamics. We describe a detailed study on the kinetics and thermodynamics for the interaction of chlorpromazine (CPZ), an antipsychotic drug used in the treatment of schizophrenia, with neutral and negatively charged lipid bilayers. Isothermal titration calorimetry was used to study the partition and translocation of CPZ in lipid membranes composed of pure POPC, POPC:POPS (9:1), and POPC:Chol:POPS (6:3:1). The membrane charge due to the presence of POPS as well as the additional charge resulting from the introduction of CPZ in the membrane were taken into account, allowing the calculation of the intrinsic partition coefficients (K(P)) and the enthalpy change (ΔH) associated with the process. The enthalpy change upon partition to all lipid bilayers studied is negative, but a significant entropy contribution was also observed for partition to the neutral membrane. Because of the positive charge of CPZ, the presence of negatively charged lipids in the bilayer increases both the observed amount of CPZ that partitions to the membrane (KP(obs)) and the magnitude of ΔH. However, when the electrostatic effects are discounted, the intrinsic partition coefficient was smaller, indicating that the hydrophobic contribution was less significant for the negatively charged membrane. The presence of cholesterol strongly decreases the affinity of CPZ for the bilayer in terms of both the amount of CPZ that associates with the membrane and the interaction enthalpy. A quantitative characterization of the rate of CPZ translocation through membranes composed of pure POPC and POPC:POPS (9:1) was also performed using an innovative methodology developed in this work based on the kinetics of the heat evolved due to the interaction of CPZ with the membranes.     

Magnetically Responsive Polymeric Microparticles for the Triggered Delivery of a Complex Mixture of Human Placental Proteins

Bone loss through traumatic injury is a significant clinical issue. Researchers have created many scaffold types to mimic an extracellular matrix to provide structural support for the formation of new bone, however functional regeneration of larger scaffolds has not been fully achieved. Newer scaffolds aim to deliver bioactive molecules to improve tissue regeneration. To achieve a more comprehensive regenerative response, a magnetically triggerable polymeric microparticle platform is developed for the on‐demand release of a complex mixture of isolated human placental proteins. This system is composed of polycaprolactone (PCL) microparticles, encapsulating magnetic nanoparticles (MNPs), and placental proteins. When subjected to an alternating magnetic field (AMF), the MNPs heat and melt the PCL, enhancing the diffusion of proteins from microparticles. When the field is off, the PCL re‐solidifies. This potentially allows for cyclic drug delivery. Here the design, synthesis, and proof‐of‐concept experiments for this system are reported. In addition, it is shown that the proteins retain function after being magnetically released. The ability to trigger the release of complex protein mixtures on‐demand may provide a significant advantage with wounds where stagnation of healing processes can occur (e.g., large segmented bone defects).     

Alterations in the Detergent-Induced Membrane Permeability and Solubilization of Saturated Phosphatidylcholine/Cholesterol Liposomes: Effects of Poly(ethylene glycol)-Conjugated Lipid

We have investigated the effects of two bile salts, chenodeoxycholate (CDC) and ursodeoxycholate (UDC), and a widely used detergent, Triton X-100 (T(X-100)), on normal and poly(ethylene glycol)-modified liposomes (PEGylated liposomes). We tested various lipid compositions, including hydrogenated soybean phosphatidylcholine/cholesterol/PEG-conjugated lipid (HSPC/PEG-lipid). Alterations in permeability were determined by the rate of drug release from the liposomes and solubilization was assessed by measuring the particle size of liposomes. In addition, we attempted to observe interactions between the detergents and lipid bilayers by using surface plasmon resonance (SPR). CDC induced drug release from liposomes in a dose-dependent manner, and the PEGylated liposomes tended to be susceptible to CDC. While UDC did not strongly induce drug release from liposomes, UDC exhibited a similar tendency with CDC. In case of T(X-100), there were significant differences in the percentage of released drug between normal and PEGylated liposomes, and the percentage of T(X-100)-induced drug release further increased with an increased ratio of PEG-lipid. SPR analysis revealed that the lipid bilayer including PEG-lipid was selectively solubilized by T(X-100), correlating with the drug release data. These results suggest that the effect of detergents on the lipid bilayer of liposomes depends on both the kind of detergent and the lipid composition, including the presence or absence of PEG-lipid. Moreover, the effects of T(X-100) on the lipid bilayers of the PEGylated liposomes significantly differed from those on the lipid bilayers of the normal liposomes.     

Transport of the neutral form of amphiphilic drugs through a planar bilayer lipid membrane: The role of the pH gradient

The inner field compensation (IFC) method was used to measure the dependence of the boundary potential (BP) difference of a bilayer lipid membrane (BLM) on remantadin concentration. It was found that the BP difference depended on the pH gradient and the buffer capacity of the solution. The addition of remantadin at one side of the membrane caused changes in the pH values in the unstirred layers near both surfaces of the membrane. These changes were detected by means of measurement of the transmembrane open circuit potential in the presence of the protonophore pentachlorphenol. The sign of the transmembrane potential corresponded to a pH decrease on the membrane cis-side (where REM was added) and a rise on the irons-side. There was no increase in the membrane conductance due to the remantadin addition.A model of remantadin penetration through the lipid membrane is proposed. According to this model, the neutral form of the drug passes through the membrane. The formation and decomposition reactions of the neutral form, taking place at the membrane boundaries, are accompanied by the ejection and sorption of protons, respectively. The pH changes in lyzosomes or receptosomes due to remantadin penetration are discussed within the framework of the resulting model.     

Di‐ and tri‐phenyltin chlorides transfer across a model lipid bilayer

A compound's ability to penetrate the plasma membrane of a cell is the critical parameter that determines its potential to become a biologically potent factor. A well‐known group of organotin compounds that exhibit toxic properties in relation to biological systems are phenyltins. There are as yet no studies that in a direct manner have established whether organotin compounds such as diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) diffuse, or not, through the lipid bilayer, although we know that at least some organotins absorb in both liposome and biological membranes. In this paper we present a series of experiments that show transfer of these compounds across the lipid membrane using the stopped‐flow technique. The results obtained demonstrate that DPhT and TPhT first adsorb onto the lipid bilayer surface, in a diffusion‐controlled manner and within a very short time (0.05 s), whereas the membrane crossing was observed to be on the order of a minute. The adsorption process was easily fitted with a single exponential for both the compounds studied, indicating a single process phenomenon. The longer time kinetics (characteristic of membrane crossing) showed a complex dependence on compound concentration and the presence of cholesterol in the membrane. On passing from the outer to the inner surface of the bilayer, organotins undergo desorption and enter the liposome interior, which has been shown in lipid monolayer desorption studies. In conclusion, it can be stated that amphiphilic DPhT and TPhT permeate the liposome membrane. Copyright © 2005 John Wiley & Sons, Ltd.     

Alternating Magnetic Field Controlled Targeted Drug Delivery Based on Graphene Oxide-Grafted Nanosupramolecules

Graphene oxide (GO)-grafted nanosupramolecules have recently emerged as neoteric nano drug carriers in the therapy of refractory diseases. Herein, a multicomponent nanosupramolecular drug carrier based on a targeted peptide and magnetic GO is reported, the drug-release behavior of which can be regulated by an alternating magnetic field (AMF). This multicomponent nanosupramolecular carrier is composed of β-cyclodextrin (β-CD)/nickel nanoparticle-modified graphene oxide (GONiCD) and mitochondrial ion-targeting peptide (MitP)-grafted hyaluronic acid (HAMitP). Owing to the host–guest interaction between β-cyclodextrin and the cyclohexyl groups on MitP, GONiCD and HAMitP could form supramolecular assemblies during the doxorubicin (Dox) loading process, which not only remarkably enhances the drug-loading capacity, but also improves the drug-release efficiency under AMF stimulus. During co-incubation with tumor cells, the Dox-loaded assemblies could strongly target the tumor mitochondria and damage both the mitochondria and the nuclei, owing to Dox release from the assemblies induced by AMF. This study sheds light on the exploration of peptide caps for controlled drug loading/release of supramolecular nanocarriers for efficient drug delivery and anticancer therapy.     

Enhanced In Vitro Antitumor Efficacy and Strong Anti‐Cell‐Migration Activity of a Hydroxycamptothecin‐Encapsulated Magnetic Nanovehicle

A 10‐hydroxycamptothecin‐encapsulated magnetic nanovehicle (HEMN) was fabricated by coencapsulating Fe₃O₄ nanoparticles and 10‐hydroxycamptothecin (HCPT) into a micelle core self‐assembled from the amphiphilic copolymer methoxy‐poly(ethylene glycol)–poly(d,l ‐lactide‐co‐glycolide) through a facile dialysis method. A satisfactory drug‐loading content of (9.03±0.67) % and a relatively high encapsulation efficiency of (53.52±6.46) % were achieved. In vitro drug release was performed by membrane dialysis and a pH‐dependent release behavior was observed. In comparison with free HCPT dissolved in dimethylsulfoxide, HEMNs showed a greatly improved in vitro antitumor efficacy against three different human cancer cell lines—HeLa, A549, and HepG2—and lower IC₅₀ values were measured. The mechanism of cell death was investigated, and it was clearly demonstrated that the apoptosis process was triggered. An in vitro wound‐healing assay and a transwell assay indicated that HEMNs exerted much stronger activity in inhibiting HeLa cell migration. The cellular uptake of HEMNs in a desired area can be significantly enhanced by an external magnetic field. These results demonstrate HCPT‐encapsulated magnetic nanovehicles might have important potential in clinical applications for inhibiting tumor metastasis and for targeted drug delivery.     

Elastic deformation of membrane bilayers probed by deuterium NMR relaxation

In deuterium ((2)H) NMR spectroscopy of fluid lipid bilayers, the average structure is manifested in the segmental order parameters (S(CD)) of the flexible molecules. The corresponding spin-lattice relaxation rates (R(1Z) depend on both the amplitudes and the rates of the segmental fluctuations, and indicate the types of lipid motions. By combining (2)H NMR order parameter measurements with relaxation studies, we have obtained a more comprehensive picture of lipids in the liquid-crystalline (L(alpha)) state than formerly possible. Our data suggest that a lipid bilayer constitutes an ordered fluid, in which the phospholipids are grafted to the aqueous interface via their polar headgroups, whereas the fatty acyl chains are in effect liquid hydrocarbon. Studies of (2)H-labeled saturated lipids indicate their R(1Z) rates and S(CD) order parameters are correlated by a model-free, square-law functional dependence, signifying the presence of relatively slow bilayer fluctuations. A new composite membrane deformation model explains simultaneously the frequency (magnetic field) dependence and the angular anisotropy of the relaxation. The results imply the R(1Z) rates are due to a broad spectrum of 3-D collective bilayer excitations, together with effective axial rotations of the lipids. For the first time, NMR relaxation studies show that the viscoelastic properties of membrane lipids at megahertz frequencies are modulated by the lipid acyl length (bilayer thickness), polar headgroups (bilayer interfacial area), inclusion of a nonionic detergent (C(12)E(8)), and the presence of cholesterol, leading to a range of bilayer softness. Our findings imply the concept of elastic deformation is relevant on lengths approaching the bilayer thickness and less (the mesoscopic scale), and suggest that application of combined R(1Z) and S(CD) studies of phospholipids can be used as a simple membrane elastometer. Heuristic estimates of the bilayer bending rigidity kappa and the area elastic modulus K(a) enable comparison to other biophysical studies, involving macroscopic deformation of thin membrane lipid films. Finally, the bilayer softness may be correlated with the lipid diversity of biomembranes, for example, with regard to membrane curvature, repulsive interactions between bilayers, and lipid-protein interactions.     

Lateral organization of a membrane protein in a supported binary lipid domain: direct observation of the organization of bacterial light-harvesting complex 2 by total internal reflection fluorescence microscopy

A unique method is described for directly observing the lateral organization of a membrane protein (bacterial light-harvesting complex LH2) in a supported lipid bilayer using total internal reflection fluorescence (TIRF) microscopy. The supported lipid bilayer consisted of anionic 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1'-glycerol)] (DOPG) and 1,2-distearoly-sn-3-[phospho-rac-(1'-glycerol)] (DSPG) and was formed through the rupture of a giant vesicle on a positively charged coverslip. TIRF microscopy revealed that the bilayer was composed of phase-separated domains. When a suspension of cationic phospholipid (1,2-dioleoyl-sn-glycero-3-ethylphosphocholine: EDOPC) vesicles (approximately 400 nm in diameter), containing LH2 complexes (EDOPC/LH2 = 1000/1), was put into contact with the supported lipid bilayer, the cationic vesicles immediately began to fuse and did so specifically with the fluid phase (DOPG-rich domain) of the supported bilayer. Fluorescence from the incorporated LH2 complexes gradually (over approximately 20 min) spread from the domain boundary into the gel domain (DSPG-rich domain). Similar diffusion into the domain-structured supported lipid membrane was observed when the fluorescent lipid (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-lissamine-rhodamine B sulfonyl: N-Rh-DOPE) was incorporated into the vesicles instead of LH2. These results indicate that vesicles containing LH2 and lipids preferentially fuse with the fluid domain, after which they laterally diffuse into the gel domain. This report describes for first time the lateral organization of a membrane protein, LH2, via vesicle fusion and subsequent lateral diffusion of the LH2 from the fluid to the gel domains in the supported lipid bilayer. The biological implications and applications of the present study are briefly discussed.     

Effects of synthetic lipids on solubilization and colloid stability of hydrophobic drugs

Aqueous miconazole (MCZ) aggregates were solubilized and/or colloidally stabilized by bilayer-forming synthetic amphiphiles such as dioctadecyldimethylammonium bromide (DODAB) or sodium dihexadecylphosphate (DHP) dispersions. Particle sizing, light absorption and scattering from drug particles, zeta-potential determination, and drug aggregation kinetics from turbidity changes in the presence or absence of lipid dispersions were obtained over a range of drug and lipid concentrations. The very low solubility of MCZ in water made possible the determination of size distributions for drug particles in water and comparison to those in the presence of DODAB or DHP nanosized bilayer fragments or entire and closed bilayer vesicles. Large drug aggregates disappeared upon incubation with nanosized bilayer fragments produced by ultrasonic dispersion with tip. Light-absorption spectra for MCZ in a poor solvent (water), in a good organic solvent (methanol), and in different lipid dispersions showed that solubilization depended on the presence of bilayer fragments. MCZ was poorly soluble in dispersions formed of closed bilayers (vesicles) of DODAB or DHP in the gel state and in phosphatidylcholine (PC) vesicles in the liquid-crystalline state. Increased hydrophobicity at the borders of bilayer fragments explained MCZ solubilization. At [MCZ]>0.4 mM, kinetics of drug aggregation, zeta-potential measurements, and size minimization were obtained upon addition of minute amounts of oppositely charged bilayer fragments ([DHP]=0.05 mM), making possible determination of a remarkable stabilizing effect of drug particles by coverage with anionic bilayer fragments. High drug colloid stability in the presence of charged bilayer fragments was achieved by two different means: (1). at large drug concentrations and small concentrations of bilayer fragments, coverage of large drug particles with bilayer fragments; (2). at large amounts of bilayer fragments, drug solubilization in its monomeric form at the borders of bilayer fragments. Inexpensive, synthetic bilayer fragments offered a large area of hydrophobic nanosurfaces dispersed and electrostatically stabilized in water, opening new prospects for drug solubilization and colloid stabilization of insoluble drug particles.     

Dynamics and state of lipid bilayer-internal water unraveled with solution state 1H dynamic nuclear polarization

The dynamics and state of lipid bilayer-internal hydration water of unilamellar lipid vesicles dispersed in solutions is characterized. This study was enabled by a recently developed technique based on Overhauser dynamic nuclear polarization (DNP)-driven amplification of (1)H nuclear magnetic resonance (NMR) signal of hydration water. This technique can, in the full presence of bulk water, selectively quantify the translational dynamics of hydration water within ～10 ? around spin labels that are specifically introduced to the local volume of interest within the lipid bilayer. With this approach, the local apparent diffusion coefficients of internal water at different depths of the lipid bilayer were determined. The modulation of these values as a response to external stimuli, such as the addition of sodium chloride or ethanol and the lipid phase transitions, that alter the fluctuations of bilayer interfaces together with the activation energy values of water diffusivity shows that water is not individually and homogeneously solvating lipid's hydrocarbon tails in the lipid bilayer. We provide experimental evidence that instead, water and the lipid membrane comprise a heterogeneous system whose constituents include transient hydrophobic water pores or water structures traversing the lipid bilayer. We show how these transient pore structures, as key vehicles for passive water transport can better reconcile our experimental data with existing literature data on lipid bilayer hydration and dynamics.     

MgFe2O4@(TF-LDHs)磁性纳米复合体的制备与表征

以镁铁尖晶石(MgFe2O4)颗粒为磁性基质, 采用共沉淀法制备了替加氟(TF)插层层状双金属氢氧化物(LDHs)包覆MgFe2O4的核-壳结构磁性纳米复合体[MgFe2O4@(TF-LDHs)], 并对其化学组成、 晶体结构和磁性等进行了表征, 探讨了TF在LDHs层间的存在状态, 考察了TF的释放行为. 实验结果表明, MgFe2O4@(TF-LDHs)纳米复合体具有顺磁性, 其比饱和磁化强度随磁性基质含量的增大而增强; TF分子在LDHs层间以长轴略倾斜于LDHs层板的方式呈双层排布; MgFe2O4@(TF-LDHs)纳米复合体具有明显的药物缓释效果, 其释放动力学过程符合准二级动力学方程, 释放机理为Fick扩散; 增大磁性基质含量或施加外加磁场均可减缓其药物释放过程.