Vesicle Transformations Resulting from Curvature Tuning in Systems with Micellar, Lamellar, and Bicontinuous Cubic Phases

Dissolution mechanism of supported phospholipid bilayer in the presence of amphiphilic drug investigated by neutron reflectometry and quartz crystal microbalance with dissipation monitoring

The influence and interaction of the ionizable amphiphilic drug amitriptyline hydrochloride (AMT) on a 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) phospholipid bilayer supported on a silica surface have been investigated using a combination of neutron reflectometry and quartz crystal microbalance with dissipation monitoring. Adding AMT solutions with concentrations 3, 12, and 50 mM leaves the lipid bilayer mainly intact and we observe most of the AMT molecules attached to the head-group region of the outer bilayer leaflet. Virtually no AMT penetrates into the hydrophilic head-group region of the inner leaflet close to the silica surface. By adding 200 mM AMT solution, the lipid bilayer dissolved entirely, indicating a threshold concentration for the solubilization of the bilayer by AMT. The observed threshold concentration is consistent with the observation that various bilayer structures abruptly transform into mixed AMT-DOPC micelles beyond a certain AMT-DOPC composition. Based on our experimental observations, we suggest that the penetration of drug into the phospholipid bilayer, and subsequent solubilization of the membrane, follows a two-step mechanism with the outer leaflet being removed prior to the inner leaflet.

Lipid engineered nanoparticle therapy for burn wound treatment

INTRODUCTION

Skin is the largest organ of the human body protecting the underlying organs and tissues from any foreign attack. Any damage caused in the skin may sometimes result in serious consequences within the internal body tissues. Burn is one such issue that damage the layers of skin and thereby makingthe skin vulnerableand pronefor any foreign matter to enter and cause serious diseases.

METHODS

An online literature assessment was steered for the lipid nanoparticles, burn wound treatments, and different types of nanoformulation. Appropriate information was taken from different electronic scientific databases such as Web of Science, Elsevier, Science Direct, Springer, PubMed, Google Scholar etc.,Additional data was summarized from textbooks, local prints and scripts.

RESULTS

Recent innovations and developments in nanotechnology-based drug delivery systems has shown promising results in minimizing the drawbacks associated with conventional therapies. Lipid based nanoparticles possess capabilities to deliver active agents to their target site without the possibility of degradation. Conventional therapy of burn wound is costly and the treatment is long lasting, making the patient uncomfortable. Moreover, italso doesn't yield satisfactory results or narrow effects.Encapsulation of bioactives inside the lipid core protects the active entity from pH and enzymatic degradations.

CONCLUSION

This review highlights the drawbacks associated with the conventional dosage forms. A lot of consideration is focused on the advancement of nanomaterials using innovative methods in wound care for treating burn wounds with the faster healing effect.This review article highlights recent developments in lipid based nanoformulations for treatment of burn wound injury.

Tenoxicam loaded hyalcubosomes for osteoarthritis

The main aim is to develop transcutaneous tenoxicam (TNX) loaded vesicles to control osteoarthritis (OA) without common side effects. Different vesicles were prepared by the emulsification technique, where poloxamer and glyceryl monooleate used for cubosomes. Then, hyalcubosomes were prepared by adding sodium hyaluronate to cubosomes components. Different characterization techniques were used. The selected formulations were tested using an ex-vivo permeation study to evaluate the ability to penetrate and retained in skin layers. Also, in-vitro cell studies using human skin fibroblasts were evaluated the safety of the formulation. The anti-inflammatory efficiency was tested using an in-vivo carrageenan-induced rat paw edema model. Finally, the efficiency to control OA symptoms was tested on three patients with a medical history of knee OA. Results confirmed the successful development of spherical cubosomes with particle size <250 nm, -14.5 mV, high entrapment efficiency percentage (>90%). Moreover, the addition of sodium hyaluronate to selected cubosomes improved viscosity and spreadability. Permeation study confirmed drug penetration and deposition. Cell studies proved the safety of the selected formulation. The animal model showed high anti-inflammatory activity. Finally, the preliminary clinical study demonstrates the potential efficacy and safety of the formulation in controlling OA symptoms over 8 weeks of therapy.

Unusual Structures of Interpolyelectrolyte Complexes: Vesicles and Perforated Vesicles

By means of computer simulation and analytical theory, we first demonstrated that the interpolyelectrolyte complexes in dilute solution can spontaneously form hollow spherical particles with thin continuous shells (vesicles) or with porous shells (perforated vesicles) if the polyions forming the complex differ in their affinity for the solvent. The solvent was considered good for the nonionic groups of one macroion and its quality was varied for the nonionic groups of the other macroion. It was found that if the electrostatic interactions are weak compared to the attraction induced by the hydrophobicity of the monomer units, the complex in poor solvent tends to form "dense core-loose shell" structures of different shapes. The strong electrostatic interactions favor the formation of the layered, the hollow, and the filled structured morphologies with the strongly segregated macroions. Vesicles with perforated walls were distinguished as the intermediate between the vesicular and the structured solid morphologies. The order parameter based on the spherical harmonics expansion was introduced to calculate the pore distribution in the perforated vesicles depending on the solvent quality. The conditions of the core-shell and hollow vesicular-like morphologies formation were determined theoretically via the calculations of their free energy. The results of the simulation and theoretical approaches are in good agreement.

Cubosomal based oral tablet for controlled drug delivery of telmisartan: formulation, in-vitro evaluation and in-vivo comparative pharmacokinetic study in rabbits

A nanoparticulate system; cubosomes has been suggested to support the controlled release of Telmisartan (TEL), a poorly water-soluble medication. Four distinctive formulae were selected according to the results of three estimated responses. The liquid cubosomes were successfully adsorbed onto Aerosil 380 to form granules. The formulae were evaluated for their flow properties. The best granules were compressed into tablets suitable for oral administration. The tablets were evaluated for its performance. The in vivo study of the best selected cubosomal tablets was checked after oral administration in the blood of albino rabbits utilizing an HPLC method. Results revealed that the highest EE was shown in formulae C5 (59.68 ± 1.3). All the prepared formulae had particle size less than 500 nm with PDI < 0.5 and the highest zeta potential results were observed in C5, C7, C9, C11 and C12 (>30 mv). A7 and A9 prepared using Aerosil 380 showed a perfect flowability. After 1 h of dissolution testing, the commercial product showed a 66% drug release while the release of all cubosomal formulae didn't exceed 35% during the first hour reaching a 85% of the drug released at the end of 24 h. A7 was selected for the in vivo study; T_max of TEL absorption is increased for cubosomal formula by three folds indicating sustained release pattern. The relative bioavailability is also increased by 2.6 fold. The investigation proposed the rationality of cubosome to figure an effective controlled release tablets to improve its bioavailability and expand its activity.

Antibacterial high-genus polymer vesicle as an "armed" drug carrier

Presented in this paper is an "armed" high-genus block copolymer vesicle (g = 18) which has excellent blood compatibility and more internal barriers than simple polymer vesicles (g = 0) for controlled anti-cancer drug delivery. The high-genus vesicle also shows better antibacterial activity against both Gram-positive and Gram-negative bacteria without quaternary ammonium moieties or the loading of any external antibiotics compared to the non-self-assembled individual polymer chains, or a conventional simple vesicle. This high-genus polymer vesicle was prepared by the self-assembly of PMEO₂MA₂₀-b-PTA₂₀ diblock copolymers in DMF-water, where PMEO₂MA is thermo-responsive poly[2-(2-methoxyethoxy)ethyl methacrylate] and PTA is pH-responsive and antibacterial poly[2-(tert-butylaminoethyl) methacrylate]. Doxorubicin (DOX) loading/release experiments revealed a retarded release rate of DOX in high-genus block copolymer vesicles than conventional simple vesicles, which could be used as an efficient drug delivery carrier with more internal barriers for drug molecules than conventional simple vesicles. Moreover, this "armed" drug delivery vehicle makes antibacterial and anti-cancer therapeutic processes proceed spontaneously, representing a safer and more efficient drug delivery system in nanomedicine.

The intermediate state of DMPG is stabilized by enhanced positive spontaneous curvature

1,2-Dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) at low salt concentrations has a complex endotherm with at least four components and extending over the span of 20 degrees. During this ongoing melting, the solution becomes viscous and scatters light poorly. This multipeak endotherm was suggested to result from the effects of curvature on the relative free energies of gel and fluid DMPG bilayers, further relating to the formation of an intermediate sponge phase between the lamellar gel and fluid phases. Although later studies appear to exclude a connected bilayer network, the relation of the endotherm peaks to curvature remains an appealing hypothesis. This was tested by including in the system both water-soluble small molecules (dimethyl sulfoxide, ethanol, and urea) as well as amphiphiles (myristoyl-lyso-PG, cholesterol, cholesterol-3-sulfate, and dimyristoylglycerol) known to alter the spontaneous curvature of bilayers. All compounds increasing the monolayer positive spontaneous curvature (ethanol, urea, myristoyl-lyso-PG, cholesterol-3-sulfate) increased the temperature span of the intermediate state and elevated the temperature of its dissolution, while all compounds increasing the negative spontaneous curvature (dimethyl sulfoxide, cholesterol, dimyristoylglycerol) had the opposite effect, implying that the intermediate state contains a structure with positive curvature. The results support the view that the intermediate state consists of vesicles with a large number of holes. The viscosity increase could be related to vesicle expansion needed to accommodate the numerous holes.

Interactions of surfactants with lipid membranes

Surfactants are surface-active, amphiphilic compounds that are water-soluble in the micro- to millimolar range, and self-assemble to form micelles or other aggregates above a critical concentration. This definition comprises synthetic detergents as well as amphiphilic peptides and lipopeptides, bile salts and many other compounds. This paper reviews the biophysics of the interactions of surfactants with membranes of insoluble, naturally occurring lipids. It discusses structural, thermodynamic and kinetic aspects of membrane-water partitioning, changes in membrane properties induced by surfactants, membrane solubilisation to micelles and other phases formed by lipid-surfactant systems. Each section defines and derives key parameters, mentions experimental methods for their measurement and compiles and discusses published data. Additionally, a brief overview is given of surfactant-like effects in biological systems, technical applications of surfactants that involve membrane interactions, and surfactant-based protocols to study biological membranes.

Self-assembly in monoelaidin aqueous dispersions: direct vesicles to cubosomes transition

BACKGROUND

In the present study, synchrotron small-angle X-ray scattering (SAXS) and Cryo-TEM were used to characterize the temperature-induced structural transitions of monoelaidin (ME) aqueous dispersion in the presence of the polymeric stabilizer F127. We prove that the direct transition from vesicles to cubosomes by heating this dispersion is possible. The obtained results were compared with the fully hydrated bulk ME phase.

METHODOLOGY/PRINCIPAL FINDINGS

Our results indicate the formation of ME dispersion, which is less stable than that based on the congener monoolein (MO). In addition, the temperature-dependence behavior significantly differs from the fully hydrated bulk phase. SAXS findings indicate a direct L(alpha)-V(2) internal transition in the dispersion. While the transition temperature is conserved in the dispersion, the formed cubosomes with internal Im3m symmetry clearly contain more water and this ordered interior is retained over a wider temperature range as compared to its fully hydrated bulk system. At 25 degrees C, Cryo-TEM observations reveal the formation of most likely closely packed onion-like vesicles. Above the lamellar to non-lamellar phase transition at 65 degrees C, flattened cubosomes with an internal nanostructure are observed. However, they have only arbitrary shapes and thus, their morphology is significantly different from that of the well-shaped analogous MO cubosome and hexosome particles.

CONCLUSIONS/SIGNIFICANCE

Our study reveals a direct liposomes-cubosomes transition in ME dispersion. The obtained results suggest that the polymeric stabilizer F127 especially plays a significant role in the membrane fusion processes. F127 incorporates in considerable amount into the internal nanostructure and leads to the formation of a highly swollen Im3m phase.

Membranolytic activity of bile salts: influence of biological membrane properties and composition

The two main steps of the membranolytic activity of detergents: 1) the partitioning of detergent molecules in the membrane and 2) the solubilisation of the membrane are systematically investigated. The interactions of two bile salt molecules, sodium cholate (NaC) and sodium deoxycholate (NaDC) with biological phospholipid model membranes are considered. The membranolytic activity is analysed as a function of the hydrophobicity of the bile salt, ionic strength, temperature, membrane phase properties, membrane surface charge and composition of the acyl chains of the lipids. The results are derived from calorimetric measurements (ITC, isothermal titration calorimetry). A thermodynamic model is described, taking into consideration electrostatic interactions, which is used for the calculation of the partition coefficient as well as to derive the complete thermodynamic parameters describing the interaction of detergents with biological membranes (change in enthalpy, change in free energy, change in entropy etc). The solubilisation properties are described in a so-called vesicle-to-micelle phase transition diagram. The obtained results are supplemented and confirmed by data obtained from other biophysical techniques (DSC differential scanning calorimetry, DLS dynamic light scattering, SANS small angle neutron scattering).

High-density encapsulation of Fe3O4 nanoparticles in lipid vesicles

We report a morphological study of the encapsulation of 12-nm Fe3O4 nanoparticles (NPs) in large unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). Preparation was done by reverse-phase evaporation. Phase behavior of the NP-lipid system was studied so that the loading of NPs in vesicles could be maximized. Increasing NP concentration significantly affects the resulting lipid morphology in a manner similar to increasing lipid concentration. Optimal production of high-density NP-loaded vesicles (HNLVs) requires temperatures of 50 degrees C, higher than the main phase transition (Tm) of DPPC. The formation of fully enclosed HNLVs requires incubation times of at least hours.

Two distinct mechanisms of vesicle-to-micelle and micelle-to-vesicle transition are mediated by the packing parameter of phospholipid-detergent systems

The detergent solubilization and reformation of phospholipid vesicles was studied for various detergents. Two distinct mechanisms of vesicle-to-micelle and micelle-to-vesicle transition were observed by turbidimetry and cryo-electron microscopy. The first mechanism involves fast solubilization of phospholipids and occurs via open vesicular intermediates. The reverse process, micelle-to-vesicle transition, mimics the vesicle-to-micelle transition. In the second mechanism the solubilization is a slow process that proceeds via micelles that pinch off from closed vesicles. During vesicle reformation, the micelle-to-vesicle transition, a large number of densely packed multilamellar vesicles are formed. The route used, for solubilization and reformation, by a given detergent-phospholipid combination is critically dependent on the overall packing parameter of the detergent-saturated phospholipid membranes. By a change of the overall packing parameter the solubilization and or reformation mechanism could be changed. All five detergents tested fit within the proposed model. With two detergents the mechanism could be changed by changing the phospholipid composition or the medium conditions.