Lipid Dispersions Research Articles

Stability of the Metastable α-Polymorph in Solid Triglyceride Drug-Carrier Nanoparticles.

Colloidal dispersions of crystalline nonpolar lipids are under intensive investigation as carrier systems in pharmaceutics and nutrition. In this context, the controlled preparation of particles in a metastable polymorphic state is of some interest for the delivery of active substances. In the present study, tristearin particles stabilized with three α-polymorph-preserving emulsifier regimes ((I) sodium glycocholate/saturated long-chain phospholipids, (II) sodium glycocholate, and (III) poly(vinyl alcohol) (PVA)) were investigated concerning the stability of the metastable α-polymorph after controlled crystallization of the particles from the melt. Upon long-term storage, the α-polymorph was preserved best in PVA-stabilized dispersions, followed by those stabilized with the glycocholate/phospholipid mixture and finally those stabilized solely with the bile salt. In particular for rapidly crystallized nanoparticles, the formation of an α-polymorph with highly reduced lamellarity was observed. According to time-/temperature-resolved synchrotron X-ray diffraction analysis with simultaneous DSC (differential scanning calorimetry) studies, this less-ordered α-polymorph transformed into the common, lamellar α-form upon heating. Although the presence of the less-ordered form is probably related to the extraordinarily high stability of the metastable α-polymorph observed in some of the dispersions, it could not completely prevent the transition into the stable β-polymorph. The higher the transition temperature of the less-ordered α-form to the ordered one, the slower was the polymorphic transition to the stable β-polymorph. To estimate the polymorphic stability of the differently stabilized particles upon isothermal long-term storage, standard DSC measurements on samples stored at 23 °C for 4 weeks seem to be of predictive value.

Kinetic Mechanism of Lipidprotein Nanodisc Dissociation in Bicelles

Nanodisc soluble lipid bilayer systems are vital in rendering membrane proteins soluble in aqueous solutions where they remain monodisperse and active in a membrane‐like environment. Nanodiscs or nanolipidprotein particles (NLPs), are bordered by an amphipathic helical protein belt or membrane scaffolding protein (MSP) mimicking a cell membrane. Past works have shown that fragments of bacteriorhodopsin when placed in separate nanodisc do not interact to form the functional protein. The introduction of bicelles enabled the fragments to form oligomers inside the bicelles. An analysis of the kinetics of the aforementioned NLP‐bicelle interaction showed a sigmoid curve suggesting the possibility of an autocatalyzed reaction. We hypothesized that the kinetics where due to MSP1E3D1′s dissociation from the nanodisc which catalyzed the reaction. Using fluorescently labeled lipids 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐(lissamine rhodamine B sulfonyl), 1,2‐diphytanoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐(7‐nitro‐2‐1,3‐benzoxadiazol‐4‐yl) LR‐PE and NBD‐PE, respectively with 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) and MSP1E3D1 we constructed NLPs. Bicelles were prepared using 1,2‐dihexanoyl‐sn‐glycero‐3‐phosphocholine (DHPC) and DMPC. Kinetics of NLP‐bicelle interactions and fluorescently labeled lipid dispersion were observed measuring fluorescence resonance energy transfer (FRET) using stopped‐flow spectroscopy. The NLP‐bicelle interaction followed previously observed kinetics and continued to do so after the addition of excess MSP1E3D1. Our results show that MSP1E3D1 is not responsible for the observed kinetics of the transfer of lipids between NLPs and bicelles.

Optimization of multi-pulse sequences for nonlinear contrast agent imaging using a cMUT array

Capacitive micromachined ultrasonic transducer (cMUT) technology provides advantages such as wide frequency bandwidth, which can be exploited for contrast agent imaging. Nevertheless, the efficiency of traditional multi-pulse imaging schemes, such as pulse inversion (PI), remains limited because of the intrinsic nonlinear character of cMUTs. Recently, a new contrast imaging sequence, called bias voltage modulation sequence (BVM), has been specifically developed for cMUTs to suppress their unwanted nonlinear behavior. In this study, we propose to optimize contrast agent detection by combining the BVM sequence with PI and/or chirp reversal (CR). An aqueous dispersion of lipid encapsulated microbubbles was exposed to several combinations of multi-pulse imaging sequences. Approaches were evaluated in vitro using 9 inter-connected elements of a cMUT linear array (excitation frequency of 4 MHz; peak negative pressure of 100 kPa). For sequences using chirp excitations, a specific compression filter was designed to compress and extract several nonlinear components from the received microbubble responses. A satisfactory cancellation of the nonlinear signal from the source is achieved when BVM is combined with PI and CR. In comparison with PI and CR imaging modes alone, using sequences incorporating BVM increases the contrast-to-tissue ratio by 10.0 dB and 4.6 dB, respectively. Furthermore, the combination of BVM with CR and PI results in a significant increase of the contrast-to-noise ratio (+29 dB). This enhancement is attributed to the use of chirps as excitation signals and the improved preservation of several nonlinear components contained within the contrast agent response.

Colloidal Dispersions of Lipids and Curcumin, and the Solubility and Degradation Kinetics of the Latter in Micellar Solution

A simple but potentially useful technique has been used to prepare colloidal dispersions of weakly soluble cholesterol(CS), Dipalmitoyl-Phosphocholine (DPPC), hexadecane dioic acid (HDA) and curcumin (CM) stabilized by the surfactants, SDS, NaC, CTAB, Tween-20, and NaDA at their critical micelle concentrations (CMC). The dispersions of DPPC were also vesicles (or liposomes); their nature, shape, and size were characterized and determined by flourimetry, dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM) methods. The solubility of CM in the micellar solution of concentrations, 1 to 10 CMC was also studied. The kinetics of degradation (instability) of the CM in basic medium in micellar solutions was investigated. The findings on the biologically important materials have been analyzed and presented.

Modulating Drug Release and Enhancing the Oral Bioavailability of Torcetrapib with Solid Lipid Dispersion Formulations.

The development of drug dispersions using solid lipids is a novel formulation strategy that can help address the challenges of poor drug solubility and systemic exposure after oral administration. The highly lipophilic and poorly water-soluble drug torcetrapib could be effectively formulated into solid lipid microparticles (SLMs) using an anti-solvent precipitation strategy. Acoustic milling was subsequently used to obtain solid lipid nanoparticles (SLNs). Torcetrapib was successfully incorporated into the lipid matrix in an amorphous state. Spherical SLMs with mean particle size of approximately 15-18 μm were produced with high drug encapsulation efficiency (>96%) while SLNs were produced with a mean particle size of 155 nm and excellent colloidal stability. The in vitro drug release and the in vivo absorption of the solid lipid micro- and nanoparticles after oral dosing in rats were evaluated against conventional crystalline drug powders as well as a spray dried amorphous polymer dispersion formulation. Interestingly, the in vitro drug release rate from the lipid particles could be tuned for immediate or extended release by controlling either the particle size or the precipitation temperature used when forming the drug-lipid particles. This change in the rate of drug release was manifested in vivo with changes in Tmax as well. In addition, in vivo pharmacokinetic studies revealed a significant increase (∼6 to 11-fold) in oral bioavailability in rats dosed with the SLMs and SLNs compared to conventional drug powders. Importantly, this formulation approach can be performed rapidly on a small scale, making it ideal as a formulation technology for use early in the drug discovery timeframe.

Liposomes Prepared in Absence of Organic Solvents: Sonication Versus Lipid Film Hydration Method

Context: Liposomes appear as an excellent vehicle for parenteral and non-parenteral administration routes. Drugs, genetic vaccines or skin care products, are candidates to be included in liposomes. Irrespective of the therapeutic aim, most reported procedures for lipid vesicles formulation, make it necessary to use and then remove organic solvents. Objetive: To explore the possibility of avoiding organic solvents for liposomes preparation by sonication of component mixture. Materials and methods: Liposomes were prepared by direct sonication of lipids and water medium and by the lipid film hydration method both in the presence and absence of trehalose. Extrusion through 1.0 and 0.1 μm pore membranes was performed in both cases. Liposomes size distribution was determined by dynamic laser scattering analysis. Results: Sonication of watery lipid dispersion produces lipid vesicles in a size range of 20-120 nm while lipid film hydration method provides with larger vesicles under all experimental assayed conditions. Extrusion through 1.0 μm pore membrane failed to produce monodisperse liposomes even from the largest liposomes. Sequential extrusion though 0.1 μm, however, lead to monodisperse samples with both methods. Conclusion: The sonication of aqueous lipid dispersions is a suitable organic solvent-free alternative for preparation of small lipid vesicles. Keywords: Extrusion, lipid vesicles, liposomes, organic-free procedures, sonication, vesicles size.

Thermotropic Behavior of Cardiolipin and Dimyristoylphosphatidylcholine Bilayers in the Presence and Absence of Calcium

Cardiolipin is an unusual lipid in that it is comprised of two diacylglycerols linked by a glycerol bridge. It is in found primarily in membranes in which electron transport is coupled to phosphorylation. There it plays a critical role in effective functioning of the electron transport chain. The mechanism by which cardiolipin plays this role may be through effects on bilayer properties as well as through direct interactions with protein complexes. In this study we investigate the influence of increasing the composition of tetramyristoyl cardiolipin (TMCL) on the thermotropic behavior of dimyristoyl phosphatidylcholine (DMPC) bilayers using differential scanning calorimetry (DSC). DSC experiments were performed using a MicroCal VP-DSC microcalorimeter. Lipid dispersions of DMPC/TMCL were prepared in which TMCL constituted 0, 5,10, 20, 50 and 100 mole percent of the total lipid. In these studies the Tm increased from 25 oC to 40 oC as the TMCL composition increased. Ca++ has been shown to have a plethora of in vivo effects on biological membranes and to induce alterations in lipid phase behavior of model membranes. Therefore we further investigated the thermotropic behavior of DMPC/TMCL bilayers in the presence of Ca++. Above 20 mole percent TMCL a distinct phase separation was induced. The effect of Ca++ on cardiolipin/PC membranes was also investigated using 6-dodecanoyl-2-dimethylaminonaphthalene (LAURDAN). These data are consistent with an alteration of the hydration of the bilayer in the headgroup region in the presence of Ca++ and suggest that Ca++ induces tighter packing.

On Prilling of Hydrophilic Microgels in Lipid Dispersions Using Mono‐N‐Carboxymethyl Chitosan for Oral Biologicals Delivery

Oral delivery of biologicals is a thriving field in pharmaceutics and the first challenge is to achieve a stable drug product. Interesting is prilling of a drug-containing polymeric solution as microgel into an aqueous hardening bath where crosslinking occurs. However, to deliver a final dosage form, for example, soft gelatin capsules, the aqueous hardening bath must be removed, thus leading to manufacturing processes that are potentially harmful for the active. The current work introduces a prilling method with a lipid-based hardening bath, which could theoretically be filled directly into capsules. Bovine serum albumin (BSA) and mono-N-carboxymethyl chitosan (MCC) were selected as model biological and encapsulating polymer, respectively. Several nonaqueous formulations of the receiving bath were investigated; calcium chloride was added to these formulations to allow the MCC gelling. The obtained microgels had average diameters of ∼300 μm and spherical to toroidal shapes, according to the hardening bath composition. Along with a high encapsulation efficiency (>85%), the microgels protected the BSA from any denaturing effect of the hardening bath. The release study showed a rather fast BSA release within the first 10 min from most microgels. This novel approach demonstrated technical viability for encapsulation of biologicals using lipid formulations regarding oral delivery.

Studying three phase contact in the system air/DMPC water dispersion/silica

The studying of lipid vesicles is motivated because they are a useful model of biological membranes. The behavior of three phase contact (TPC) formed on different substrates from lipid dispersions is of high practical importance. In the present paper, we study wetting of hydrophilic silica surfaces with DMPC dispersion by measurement of their three-phase contact (TPC) parameters. These properties can provide more detailed information about the hydrophobicity and structure of the adsorbed lipid layer. The calculation of TPC parameters, from the contact angle and surface tension of liquid–vapor interface experimental data starts with Young's equation. An approach of additional relation among the parameters of Young's equation such as an equation-of-state relation is used to calculate the surface tensions solid–liquid and solid–vapor interfaces. Two states are observed distinctly in dependence of the phase interface surface tension on the DMPC dispersion concentration. The calculated values of the adsorption are reasonable. Surface adsorption at the solid–liquid interface is significantly lower than the adsorption of the other two interfaces. The obtained results about the adsorption are in agreement with the expected physical picture.

PEGylation of phytantriol-based lyotropic liquid crystalline particles--the effect of lipid composition, PEG chain length, and temperature on the internal nanostructure.

Poly(ethylene glycol)-grafted 1,2-distearoyl-sn-glycero-3-phosphoethanolamines (DSPE-mPEGs) are a family of amphiphilic lipopolymers attractive in formulating injectable long-circulating nanoparticulate drug formulations. In addition to long circulating liposomes, there is an interest in developing injectable long-circulating drug nanocarriers based on cubosomes and hexosomes by shielding and coating the dispersed particles enveloping well-defined internal nonlamellar liquid crystalline nanostructures with hydrophilic PEG segments. The present study attempts to shed light on the possible PEGylation of these lipidic nonlamellar liquid crystalline particles by using DSPE-mPEGs with three different block lengths of the hydrophilic PEG segment. The effects of lipid composition, PEG chain length, and temperature on the morphology and internal nanostructure of these self-assembled lipidic aqueous dispersions based on phytantriol (PHYT) were investigated by means of synchrotron small-angle X-ray scattering and Transmission Electron Cryo-Microscopy. The results suggest that the used lipopolymers are incorporated into the water-PHYT interfacial area and induce a significant effect on the internal nanostructures of the dispersed submicrometer-sized particles. The hydrophilic domains of the internal liquid crystalline nanostructures of these aqueous dispersions are functionalized, i.e., the hydrophilic nanochannels of the internal cubic Pn3m and Im3m phases are significantly enlarged in the presence of relatively small amounts of the used DSPE-mPEGs. It is evident that the partial replacement of PHYT by these PEGylated lipids could be an attractive approach for the surface modification of cubosomal and hexosomal particles. These PEGylated nanocarriers are particularly attractive in designing injectable cubosomal and hexosomal nanocarriers for loading drugs and/or imaging probes.

New Micellar Transfection Agents

Two novel micelle-forming amino-functionalized lipids (OT6 and TT6) bearing two alkyl chains connected to a large positively charged hexavalent headgroup, which might be interesting polynucleotide transferring agents with the advantage of an easy and reproducible production of micelle dispersions, have been characterized. The critical micelle concentration (cmc) of both lipids has been determined by two different methods, namely, isothermal titration calorimetry (ITC) and 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence experiments. In addition, the lipid dispersions were studied as a function of temperature using differential scanning calorimetry (DSC), dynamic light scattering (DLS), Fourier-transform infrared (FT-IR) spectroscopy, and cryo-transmission electron microscopy (cryo-TEM). The OT6 and TT6 micelles effectively complex DNA as determined by ITC and DSC measurements. In addition, DLS and ζ-potential measurements were performed to determine lipoplex formulations that exhibit colloidal stability. Finally, the structures of OT6/DNA complexes were investigated by means of X-ray scattering and TEM.

Phospholipid-Cholesterol Bilayers, Cholesterol Bilayer Domains, and Cholesterol Crystals were Detected in Lipid Dispersion Prepared from Lipids Extracted from Lens Nucleus of Old Human Donors

Human lens lipid membranes prepared using a rapid solvent exchange method from the total lipids extracted from the clear lens cortex and nucleus of 61- to 70-year-old donors were investigated. The measured cholesterol-to-phospholipid (Chol/PL) molar ratio in these preparations was extremely high, showing values of 1.8 and 4.4 for cortex and nucleus, respectively. We expect that at this elevated Chol content, the entire membrane will become saturated with Chol (as in the case of the cortical membrane) and the excess of Chol will form Chol crystals, presumably outside the membrane (as in the case of the nuclear membrane). Properties and organization of the lipid bilayer were investigated using electron paramagnetic resonance spin-labeling methods. Formation of Chol crystals was confirmed using the differential scanning calorimetry. We showed that in the lipid dispersion prepared from nuclear lipids Chol exists in three distinguished environments: (1) Chol dispersed in PL bilayer, (2) Chol in non-crystalline membrane domains (cholesterol bilayer domains, CBDs), and (3) Chol in crystals. In cortical membranes, because of the lower Chol content, Chol crystals were not detected. Amounts of Chol in CBDs were almost the same in cortical and nuclear membranes which indicates that Chol content in both membranes is close or exceeds the Chol solubility thresholds in these membranes. Profiles of cortical and nuclear membrane properties (alkyl-chain order, fluidity, oxygen transport parameter, and hydrophobicity) were very similar to each other and to those reported for cortical and nuclear lens lipid membranes of 41- to 60-year-old donors reported earlier. This confirms our earlier statement that saturation with Chol determines properties of the PL bilayer with the minor effect of the PL composition.

Single-Step Co-Crystallization and Lipid Dispersion by Supercritical Enhanced Atomization

This work evaluates the feasibility of the supercritical enhanced atomization (SEA) process to improve stability and delivery of active pharmaceutical ingredients (APIs). This process was used to generate distinct microcomposites of pure theophylline (TPL), an API model, the theophylline-saccharin (TPL-SAC) cocrystal, and dispersions of each crystalline form in hydrogenated palm oil (HPO), TPL-HPO and TPL-SAC-HPO. The formation of the TPL-SAC cocrystal within the HPO suggests that the cocrystallization step anticipates the lipid dispersion during the formation of the microcomposites. The TPL-SAC cocrystal extended the TPL stability at 92% relative humidity by over 6 months, contrary to that of raw TPL, which converted into a monohydrate after a few days only, even when dispersed into HPO. The TPL-SAC cocrystal slowed the TPL release from the lipid particles, which is explained by its higher stability toward hydration. The feasibility of the cocrystal microcomposites for therapeutic application was evaluated by estimating the plasmatic concentration of TPL using a pharmacokinetic model (one compartment approach). This model revealed that the small therapeutic concentration window and high elimination rate of TPL raises serious limitations to control the TPL release. The microcomposites were able to attenuate the TPL burst effect and improve stability toward hydration but could not extend significantly its delivery.

Comparison of Intravenous Lipid Emulsion, Bicarbonate, and Tailored Liposomes in Rabbit Clomipramine Toxicity

Liposome (LIP)-like lipid dispersions have emerged as useful detoxification vehicles in vitro. The authors compare resuscitation with tailored LIPs, 20% intravenous lipid emulsion (ILE), and sodium bicarbonate (BIC), in a rabbit model of clomipramine toxicity. Sedated, instrumented New Zealand white rabbits underwent clomipramine infusion at 3.2mg/kg/min to 50% baseline mean arterial pressure (MAP) and then at 1.6mg/kg/min for 30minutes. BIC (3mL/kg 8.4%), ILE (3mL/kg 20%), or LIP (24mg/kg) were infused as rescue treatments at toxicity and were repeated at 10minutes (n=5 in each group). Thirty-minute MAP was greatest in ILE-treated animals: 61mmHg ILE (interquartile range [IQR]= 49 to 64mmHg), 43mmHg LIP (IQR= 36.5 to 49mmHg), and 10mmHg BIC (IQR= 10 to 44mmHg; all p=0.02). Two of the five BIC-treated animals survived to 30minutes, compared with all five of the ILE-treated animals and all five of the LIP-treated animals (p=0.044). Both ILE and LIPs improved hemodynamic recovery compared with bicarbonate in clomipramine-induced cardiotoxicity in rabbits. Greater 30-minute MAP was observed in the ILE group.

Interaction of the C-Terminal Peptide of Pulmonary Surfactant Protein B (SP-B) with a Bicellar Lipid Mixture Containing Anionic Lipid

The hydrophobic lung surfactant SP-B is essential for respiration. SP-B promotes spreading and adsorption of surfactant at the alveolar air-water interface and may facilitate connections between the surface layer and underlying lamellar reservoirs of surfactant material. SP-B63–78 is a cationic and amphipathic helical peptide containing the C-terminal helix of SP-B. 2H NMR has been used to examine the effect of SP-B63–78 on the phase behavior and dynamics of bicellar lipid dispersions containing the longer chain phospholipids DMPC-d 54 and DMPG and the shorter chain lipid DHPC mixed with a 3∶1∶1 molar ratio. Below the gel-to-liquid crystal phase transition temperature of the longer chain components, bicellar mixtures form small, rapidly reorienting disk-like particles with shorter chain lipid components predominantly found around the highly curved particle edges. With increasing temperature, the particles coalesce into larger magnetically-oriented structures and then into more extended lamellar phases. The susceptibility of bicellar particles to coalescence and large scale reorganization makes them an interesting platform in which to study peptide-induced interactions between lipid assemblies. SP-B63–78 is found to lower the temperature at which the orientable phase transforms to the more extended lamellar phase. The peptide also changes the spectrum of motions contributing to quadrupole echo decay in the lamellar phase. The way in which the peptide alters interactions between bilayered micelle structures may provide some insight into some aspects of the role of full-length SP-B in maintaining a functional surfactant layer in lungs.

Controlled polymorphic transformation of continuously crystallized solid lipid nanoparticles in a microstructured device: A feasibility study

The contribution describes the transfer from a batch to a micro-continuous process for the production of stable solid lipid nanoparticles as drug carrier systems. Solid lipid nanoparticles are commonly prepared batch-wise often resulting in poorly defined product qualities with regard to the polymorphic state of their lipid matrix. In order to obtain solid lipid nanoparticle dispersions that meet the requirements for an acceptable pharmaceutical product, the manufacture of reproducible product qualities preferably containing the stable crystal form of the respective matrix lipid is necessary. These requests are addressed by the continuous preparation process of solid lipid nanoparticles. A four step feasibility study for the standardized evaluation whether or not a colloidal lipid dispersion is suitable for continuous crystallization of the particles resulting in stable crystal forms is presented. The process is based on the continuous crystallization and subsequent thermal treatment of differently stabilized, tripalmitin-based nanoparticle formulations in microstructured devices. The successful production of the stable crystal form by means of a continuous process chain is shown for a dispersion stabilized with a blend of hydrogenated soybean lecithin and sodium glycocholate.

General Synthesis and Physicochemical Characterisation of a Series of Peptide‐Mimic Lysine‐Based Amino‐Functionalised Lipids

A series of novel malonic acid diamides (second generation) with two long hydrophobic alkyl chains and an alkaline polar head group was synthesised and characterised as a new class of amino-functionalised lipids. These peptide-mimic lipids are suitable for polynucleotide transfer. The lipids bear a novel backbone consisting of a lysine unit and a malonic acid unit. Six different head-group structures, which vary in size and number of amino groups that can be protonated, were attached to the backbone structure. Furthermore, different alkyl chains were used to build the lipophilic part (namely tetradecyl, hexadecyl, and oleyl). Phase transitions of the new compounds in aqueous dispersions at pH 10 were analysed and discussed in terms of head group and alkyl chain variations. The shape and size of the formed aggregates of selected lipid dispersions were investigated by dynamic light scattering and transmission electron microscopy.

English

technique for characterising microparticles and nanosystems recently developed by our research group. In particular, polyester or acrylic polymer microparticles for fenretinide administration are presented here. Moreover, with regard to nanosystems, solid lipid nanoparticles, nanostructured lipid carriers for prednisone and clotrimazole administration and monooleine aqueous dispersion are discussed. Methodology Microparticles were produced by the ‘solvent evaporation method’. Solid lipid nanoparticlesand nanostructured lipid carriers were prepared by stirring, followed by ultrasonication. Monooleine aqueous dispersionswere produced by the hydrotrope or by the hot homogenization methods. For scanning electron microscopyanalysis, microparticles were metallized by gold coating (Edwards Sputter coat-ing S150) and visualized at 15 – 20 kV with a 360 Stereoscan (Cambridge Instruments, Cambridge, UK). For Cryo-TEM ­analysis­ samples­were­ vitrified­ and­ transferred to a Zeiss EM922Omega (Zeiss SMT, Oberkochen, Germany). Images were recorded by a CCD digital camera (Ultrascan 1000, Gatan) and analyzed using a GMS 1.8 software (Gatan). Conclusion Microscopy is to be considered as an indispensable tool to study drug delivery systems. In particular, scanning electron microscopy is helpful in giving information about micro-sized powders, allowing to identify microspheres and microcapsules, as well as to obtain size distribution of the observed particles. Introduction Microand nanoparticles have attracted pharmaceutical interest in the last decades since they offer a number of advantages with respect to other delivery systems such as: (a) the ability to maintain unaltered physicochemical characteristics for long periods allowing long-term storage; (b) the possible administration through different ways (oral, intramuscular or subcutaneous) depending on their composition and (c) their suitability for industrial production1. Concerning nanosystems, lipid dispersions possess a potential use as matrixes able to dissolve and deliver active molecules in a controlled fashion, thereby improving their bioavailability and reducing side-effects2. In particular, solid lipid nanoparticles (SLN) are delivery systems in which the nano-dispersed phase has a matrix of crystalline solid lipids. SLN are able to protect encapsulated molecules from degradation and modulate their release3,4. Another generation of SLN is represented by nanostructured lipid carriers (NLC) whose matrix is composed of a mixture of solid–liquid lipids able to better solubilise lipophilic drugs5,6. Another type of lipid dispersion able to provide matrices for sustained­ drug­ release­ is­ typified­ by­ monooleine aqueous dispersions (MAD). MAD are heterogeneous systems generated by the dispersion of an amphiphilic lipid, such as monoolein, in water. They are constituted of complex lyotropic liquid crystalline nanostructures like micellar, lamellar, hexagonal and cubic phases, the predominance of one species over Abstract Introduction This review provides an overview of the use of microscopy as a tool to characterise shape and dimension of micro and nanoparticulate systems. In­ the­ pharmaceutical­ field,­ the­ use of microscopy has been exerted an important role since the advent of micro and nanotechnology. Indeed, the morphology of particles and their­ inner­ structure­ does­ influence­ the modalities of administration and release of encapsulated drugs. Scanning electron microscopy can be employed to study the morphology of dry powders. In particular microparticles made of polymers can be well visualised and their diameters can be measured. By cutting the powder during sample preparation, it is possible to obtain important information about the inner morphology of the microstructures, discriminating either the capsule or the sphere microstructure. Cryo transmission electron microscopy is a precious tool for characterising colloidal systems. In particular, external as well as internal shape of nanoparticulate systems such as solid lipid nanoparticles or lyotropic mesophases can be well identified.­Moreover,­size­of­disperse­ phase and the overall structure of the dispersion can be monitored. We provide an overview about the use of electron microscopy as

Solid Lipid Dispersions: Potential Delivery System for Functional Ingredients in Foods

Structured solid lipid (SL) systems have the advantages of long-term physical stability, low surfactant concentrations, and may exhibit controlled release of active ingredients. In this research work, the potential use of high-melting SLs for the production of the above structured SL carrier systems was investigated. Dispersions containing either SL or blend of solid lipid and oil (SL+O) were produced by a hot melt high-pressure homogenization method. Experiments involved the use of 3 different SLs for the disperse phase: stearic acid, candelilla wax and carnauba wax. Sunflower oil was incorporated in the disperse phase for the production of the dispersions containing lipid and oil. In order to evaluate the practical aspects of structured particles, analytical techniques were used including: static light scattering to measure particle sizes, transmission electron microscopy (TEM) for investigating particle morphology and differential scanning calorimetry (DSC) to investigate the crystallization behavior of lipids in bulk and in dispersions. Results showed different mean particle sizes depending on the type of lipid used in the disperse phase. Particle sizes for the 3 lipids were: stearic acid (SL: 195 ± 2.5 nm; SL+O: 138 ± 6.0 nm); candelilla wax (SL: 178 ± 1.7 nm; SL+O: 144 ± 0.6 nm); carnauba wax (SL: 303 ± 1.5 nm; SL+O: 295 ± 5.0 nm). TEM results gave an insight into the practical morphology, showing plate-like and needle-like structures. DSC investigations also revealed that SL dispersions melted and crystallized at lower temperatures than the bulk. This decrease can be explained by the small particle sizes of the dispersion, the high-specific surface area, and the presence of a surfactant.

Dynamics and Molecular Determinants of Cytoplasmic Lipid Droplet Clustering and Dispersion

Perilipin-1 (Plin1), a prominent cytoplasmic lipid droplet (CLD) binding phosphoprotein and key physiological regulator of triglyceride storage and lipolysis in adipocytes, is thought to regulate the fragmentation and dispersion of CLD that occurs in response to β-adrenergic activation of adenylate cyclase. Here we investigate the dynamics and molecular determinants of these processes using cell lines stably expressing recombinant forms of Plin1 and/or other members of the perilipin family. Plin1 and a C-terminal CLD-binding fragment of Plin1 (Plin1CT) induced formation of single dense CLD clusters near the microtubule organizing center, whereas neither an N-terminal CLD-binding fragment of Plin1, nor Plin2 or Plin3 induced clustering. Clustered CLD coated by Plin1, or Plin1CT, dispersed in response to isoproterenol, or other agents that activate adenylate cyclase, in a process inhibited by the protein kinase A inhibitor, H89, and blocked by microtubule disruption. Isoproterenol-stimulated phosphorylation of CLD-associated Plin1 on serine 492 preceded their dispersion, and live cell imaging showed that cluster dispersion involved initial fragmentation of tight clusters into multiple smaller clusters, which then fragmented into well-dispersed individual CLD. siRNA knockdown of the cortical actin binding protein, moesin, induced disaggregation of tight clusters into multiple smaller clusters, and inhibited the reaggregation of dispersed CLD into tight clusters. Together these data suggest that the clustering and dispersion processes involve a complex orchestration of phosphorylation-dependent, microtubule-dependent and independent, and microfilament dependent steps.