Thermodynamic and structural properties of lipid-photosensitizer conjugates mixed with phospholipids: Impact on the formation and stability of nano-assemblies.

The photosensitizer Phenalenone (PN) was grafted with one or two lipid (C18) chains to form pure nano-assemblies or mixed lipid vesicles suitable for photodynamic therapy. Mixtures of PN-C18 conjugates with stearoyl-oleoyl phosphatidylcholine (SOPC) form vesicles that disintegrate into bilayer sheets as the concentration of PN-C18 conjugates increases. We hypothesized that PN-C18 conjugates control the thermodynamic and structural properties of the mixtures and induce the disintegration of vesicles due to PN π-π-interactions. Monolayers were analyzed by surface pressure and grazing incidence X-ray diffraction (GIXD) measurements, and vesicles by differential scanning calorimetry and cryo-TEM. The results showed that PN-triazole-C18 (1A) and PN-NH-C18 (1B) segregate from the phospholipid domains. PN-(C18)2 (conjugate 2) develops favorable interactions with SOPC and distearoyl-phosphatidylcholine (DSPC). GIXD demonstrates the contribution of SOPC to the structuring of conjugate 2 and the role of the major component in controlling the structural properties of DSPC-conjugate 2 mixtures. Above 10 mol% conjugate 2 in SOPC vesicles, the coexistence of domains with different molecule packing leads to conjugate segregation, vesicle deformation, and the formation of small bilayer discs stabilized by the inter-bilayer π-π stacking of PN molecules.

PLA-PEG forming worm-like nanoparticles despite unfavorable packing parameter: Formation mechanism, thermal stability and potential for cell internalization.

Most nanoparticles produced for drug delivery purposes are spherical. However, the literature suggests that elongated particles are advantageous, notably in terms of cellular uptake. Thus, we synthesized biocompatible polylactide-b-poly(ethylene glycol) (PLA-PEG) polymers bearing carboxylate moieties, and used them to formulate worm-like nanoparticles by a simple emulsion-evaporation process. Worm-like nanoparticles with variable aspect ratio were obtained by simply adjusting the molar mass of the PLA block: the shorter the molar mass of the PLA block, the more elongated the particles. As PLA molar mass decreased from 80,000 g/mol to 13,000 g/mol, the proportion of worm-like nanoparticles increased from 0 to 46%, in contradiction with the usual behavior of block polymers based on their packing parameter. To explain this unusual phenomenon, we hypothesized the shape arises from a combination of steric and electrostatic repulsions between PEG chains bearing a carboxylate moiety present at the dichloromethane-water interface during the evaporation process. Worm-like particles turned out to be unstable when incubated at 37 °C, above polymer glass transition temperature. Indeed, above Tg, a Plateau-Rayleigh instability occurs, leading to the division of the worm-like particles into spheres. However, this instability was slow enough to assess worm-like particles uptake by murine macrophages. A slight but significant increase of internalization was observed for worm-like particles, compared to their spherical counterparts, confirming the interest of developing biocompatible anisotropic nanoparticles for pharmaceutical applications such as drug delivery.

Organization of the Interfacial Film of Nanoemulsions Stabilized by Porphyrin Derivatives.

Photodynamic therapies combining the action of a photosensitizer (PS), molecular oxygen, and light make it possible to destroy certain infectious sites and tumors. The incorporation of photosensitizers in nanocarriers allows for better control of their distribution in tissues and increases their concentration in the area that will be then illuminated. Nanoemulsions of glyceryl trioctanoate (GTO) have been designed in which pyropheophobide a (Pyro-A) or its lipid conjugate (Pyro-Lipid) are both stabilizing and photostimulable agents. In this work, we studied by surface pressure measurements and Brewster angle microscopy (BAM) analysis the organization of the interfacial films of nanodroplets. Comparison of preformed porphyrin nanoemulsions and two porphyrin-GTO mixtures, one mimicking the composition of the nanoemulsions and the other that of a porphyrin-rich interfacial film, highlighted the role of GTO and porphyrin derivatives in the formation, organization, and elasticity of the interfacial films in nanoemulsions. Pyro-Lipid and GTO can mix, and some of the GTO molecules remain inserted in the interfacial film at high surface pressures. In contrast, Pyro-A and GTO do not mix well and tend to segregate, leaving Pyro-A alone in the condensed interfacial film. The results of this study demonstrate the importance of characterizing the interfacial properties of porphyrin derivatives and their interaction with the oil to design stable nanoemulsions with well-controlled optical properties.

Interplay between mucus mobility and alveolar macrophage targeting of surface-modified liposomes.

Alveolar macrophages play a crucial role in the initiation and resolution of the immune response in the lungs. Pro-inflammatory M1 alveolar macrophages are an interesting target for treating inflammatory and infectious pulmonary diseases. One commune targeting strategy is to use nanoparticles conjugated with hyaluronic acid, which interact with CD44 overexpressed on the membrane of those cells. Unfortunately, this coating strategy may be countered by the presence on the surface of the nanoparticles of a poly(ethylene glycol) corona employed to improve nanoparticles' diffusion in the lung mucus. This study aims to measure this phenomenon by comparing the behavior in a murine lung inflammation model of three liposomal platforms designed to represent different poly(ethylene glycol) and hyaluronic acid densities (Liposome-PEG, Liposome-PEG-HA and Liposome-HA). In this work, the liposomes were obtained by a one-step ethanol injection method. Their interaction with mucin and targeting ability toward pro-inflammatory macrophages were then investigated in vitro and in vivo in a LPS model of lung inflammation. In vitro, poly(ethylene glycol) free HA-liposomes display a superior targeting efficiency toward M1 macrophages, while the addition of poly(ethylene glycol) induces better mucus mobility. Interestingly in vivo studies revealed that the three liposomes showed distinct cell specificity with alveolar macrophages demonstrating an avidity for poly(ethylene glycol) free HA-liposomes, while neutrophils favored PEGylated liposomes exempt of HA. Those results could be explained by the presence of two forces exercising a balance between mucus penetration and receptor targeting. This study corroborates the importance of considering the site of action and the targeted cells when designing nanoparticles to treat lung diseases.

Polylactide Perspectives in Biomedicine: From Novel Synthesis to the Application Performance.

The incessant developments in the pharmaceutical and biomedical fields, particularly, customised solutions for specific diseases with targeted therapeutic treatments, require the design of multicomponent materials with multifunctional capabilities. Biodegradable polymers offer a variety of tailored physicochemical properties minimising health adverse side effects at a low price and weight, which are ideal to design matrices for hybrid materials. PLAs emerge as an ideal candidate to develop novel materials as are endowed withcombined ambivalent performance parameters. The state-of-the-art of use of PLA-based materials aimed at pharmaceutical and biomedical applications is reviewed, with an emphasis on the correlation between the synthesis and the processing conditions that define the nanostructure generated, with the final performance studies typically conducted with either therapeutic agents by in vitro and/or in vivo experiments or biomedical devices.

Multifunctional PLA/Gelatin Bionanocomposites for Tailored Drug Delivery Systems.

A series of bionanocomposites composed of shark gelatin hydrogels and PLA nanoparticles featuring different nanostructures were designed to generate multifunctional drug delivery systems with tailored release rates required for personalized treatment approaches. The global conception of the systems was considered from the desired customization of the drug release while featuring the viscoelastic properties needed for their ease of storage and posterior local administration as well as their biocompatibility and cell growth capability for the successful administration at the biomolecular level. The hydrogel matrix offers the support to develop a direct thermal method to convert the typical kinetic trapped nanostructures afforded by the formulation method whilst avoiding the detrimental nanoparticle agglomeration that diminishes their therapeutic effect. The nanoparticles generated were successfully formulated with two different antitumoral compounds (doxorubicin and dasatinib) possessing different structures to prove the loading versatility of the drug delivery system. The bionanocomposites were characterized by several techniques (SEM, DLS, RAMAN, DSC, SAXS/WAXS and rheology) as well as their reversible sol-gel transition upon thermal treatment that occurs during the drug delivery system preparation and the thermal annealing step. In addition, the local applicability of the drug delivery system was assessed by the so-called "syringe test" to validate both the storage capability and its flow properties at simulated physiological conditions. Finally, the drug release profiles of the doxorubicin from both the PLA nanoparticles or the bionanocomposites were analyzed and correlated to the nanostructure of the drug delivery system.

Synthesis of High Molecular Weight Stereo-Di-Block Copolymers Driven by a Co-Initiator Free Catalyst.

Stereo-diblock copolymers of high molecular weight polylactide (PLA) were synthetized by the one pot-sequential addition method assisted by a heteroscorpionate catalyst without the need of a co-initiator. The alkyl zinc organometallic heteroscorpionate derivative (Zn(Et)(κ3-bpzteH)] (bpzteH = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide) proved to assist in the mechanism of reaction following a coordination-insertion process. Kinetic studies along with the linear correlation between monomer and number average molecular weight (Mn) conversion, and the narrow polydispersities supported the truly living polymerization character of the initiator, whereas matrix-assisted laser desorption/Ionization-time of flight (MALDI-TOF) studies showed a very low order of transesterification. The high stereo-control attained for the afforded high molecular weight derivatives was revealed by homonuclear decoupled 1H NMR spectra and polarimetry measurements. The nanostructure of the PLA derivatives was studied by both wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) and the stereocomplex phase of the PLA stereo-diblock copolymers was successfully identified.

Data Mining of Polymer Phase Transitions upon Temperature Changes by Small and Wide-Angle X-ray Scattering Combined with Raman Spectroscopy.

The complex physical transformations of polymers upon external thermodynamic changes are related to the molecular length of the polymer and its associated multifaceted energetic balance. The understanding of subtle transitions or multistep phase transformation requires real-time phenomenological studies using a multi-technique approach that covers several length-scales and chemical states. A combination of X-ray scattering techniques with Raman spectroscopy and Differential Scanning Calorimetry was conducted to correlate the structural changes from the conformational chain to the polymer crystal and mesoscale organization. Current research applications and the experimental combination of Raman spectroscopy with simultaneous SAXS/WAXS measurements coupled to a DSC is discussed. In particular, we show that in order to obtain the maximum benefit from simultaneously obtained high-quality data sets from different techniques, one should look beyond traditional analysis techniques and instead apply multivariate analysis. Data mining strategies can be applied to develop methods to control polymer processing in an industrial context. Crystallization studies of a PVDF blend with a fluoroelastomer, known to feature complex phase transitions, were used to validate the combined approach and further analyzed by MVA.

Deciphering the Peculiar Behavior of ß-Lapachone in Lipid Monolayers and Bilayers.

ß-Lapachone (ß-Lap) is a promising anticancer drug whose applications have been limited so far because of its poor solubility and stability. Its encapsulation in liposomes has been proposed to overcome these issues. However, surface pressure measurements show that ß-Lap exhibits atypical interfacial behavior when mixed with lipids. Although the drug does not seem to be retained in lipid monolayers as deduced from the π-A isotherms, small changes in compressibility moduli suggest that ß-Lap actually interacts with lipids, either disorganizing or rigidifying their monolayers. Thermal and structural analyses of lipid bilayers confirm the existence of ß-Lap/lipid interactions and show that the drug inserts between hydrophobic chains, close to the polar headgroup in DPPC bilayers and deeper in the acyl chains in POPC bilayers. Molecular dynamics simulations allow a comprehensive description of the drug position and orientation in DOPC and POPC bilayers in the presence or absence of cholesterol.

Stacking as a Key Property for Creating Nanoparticles with Tunable Shape: The Case of Squalenoyl-Doxorubicin.

The development of elongated nanoparticles for drug delivery is of growing interest in recent years, due to longer blood circulation and improved efficacy compared to spherical counterparts. Squalenoyl-doxorubicin (SQ-Dox) conjugate was previously shown to form elongated nanoparticles with improved therapeutic efficacy and decreased toxicity compared to free doxorubicin. By using experimental and computational techniques, we demonstrate here that the specific physical properties of SQ-Dox, which include stacking and electrostatic interactions of doxorubicin as well as hydrophobic interactions of squalene, are involved in the formation of nanoassemblies with diverse elongated structures. We show that SQ-Dox bioconjugate concentration, ionic strength, and anion nature can be used to modulate the shape and stiffness of SQ-Dox nanoparticles. As those parameters are involved in nanoparticle behavior in biological media, these findings could bring interesting opportunities for drug delivery and serve as an example for the design of original nanodrugs with stacking properties tuned for particular clinical purposes.

Time evolution of Symmetry-forbidden Raman lines activated by photorefractivity.

Transmission Raman spectroscopy experiments were performed on iron doped congruent lithium niobate within two -in principle equivalent- configurations, namely Y(ZX)Y and Y(XZ)Y. While the former respects the Raman selection rules, the other configuration gives a time dependent spectrum that, after a transient time of several minutes, finally results in a mixture of expected and forbidden modes. This breaking of Raman selection rules is caused by the spontaneous conversion of a part of the ordinarily polarized pump beam into an extraordinarily polarized beam by photorefractive anisotropic self-scattering. A numerical modelling of the phenomenon is developed and fairly reproduces the time dependence of conversion energy.

Bare and Sterically Stabilized PLGA Nanoparticles for the Stabilization of Pickering Emulsions.

Pickering emulsions were formulated using biodegradable and biocompatible poly(lactic- co-glycolic acid) (PLGA) nanoparticles (NPs) prepared without surfactants or any other polymer than PLGA. A pharmaceutical and cosmetic oil (Miglyol) was chosen as the oil phase at a ratio of 10% w/w. These emulsions were then compared with emulsions using the same oil but formulated with well-described PLGA-poly(vinyl alcohol) (PVA) NPs, i.e., with PVA as NP stabilizers. Strikingly, the emulsions demonstrated very different structures at macroscopic, microscopic, and interfacial scales, depending on the type of NPs used. Indeed, the emulsion layer was significantly thicker when using PLGA NPs rather than PLGA-PVA NPs. This was attributed to the formation and coexistence of multiple water-in-oil-in-water (W/O/W) and simple oil-in-water (O/W) droplets, using a single step of emulsification, whereas simple O/W emulsions were obtained with PLGA-PVA NPs. The latter NPs were more hydrophilic than bare PLGA NPs because of the presence of PVA at their surface. Moreover, PLGA NPs only slightly lowered the oil/water interfacial tension whereas the decrease was more pronounced with PLGA-PVA NPs. The PVA chains at the PLGA-PVA NP surface could probably partially desorb from the NPs and adsorb at the interface, inducing the interfacial tension decrease. Finally, independent of their composition, NPs were adsorbed at the oil/water interface without influencing its rheological behavior, possibly due to their mobility at their interface. This work has direct implications in the formulation of Pickering emulsions and stresses the paramount influence of the physicochemical nature of the NP surface into the stabilization of these systems.

Molecular interactions governing the incorporation of cholecalciferol and retinyl-palmitate in mixed taurocholate-lipid micelles.

Cholecalciferol (D3) and retinyl palmitate (RP) are the two main fat-soluble vitamins found in foods from animal origin. It is assumed that they are solubilized in mixed micelles prior to their uptake by intestinal cells, but only scarce data are available on the relative efficiency of this process and the molecular interactions that govern it. The extent of solubilization of D3 and RP in micelles composed of lipids and sodium taurocholate (NaTC) was determined. Then, the molecular interactions between components were analyzed by surface tension and surface pressure measurements. The mixture of lipids and NaTC allowed formation of micelles with higher molecular order, and at lower concentrations than pure NaTC molecules. D3 solubilization in the aqueous phase rich in mixed micelles was several times higher than that of RP. This was explained by interactions between NaTC or lipids and D3 thermodynamically more favorable than with RP, and by D3 self-association.

Dexamethasone palmitate large porous particles: A controlled release formulation for lung delivery of corticosteroids.

We have optimized a formulation of a prodrug of dexamethasone (DXM), dexamethasone palmitate (DXP) for pulmonary delivery as a dry powder. Formulations were prepared by spray drying DXP with 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) and Hyaluronic Acid (HA) as excipients. Large porous particles around 13 µm were produced with a tap density of 0.05g/cm3 and a Fine particle fraction around 40%. The palmitate moiety favors DXP insertion into DPPC bilayers therefore limiting its in vitro release as shown by differential scanning calorimetry. After administering DXP powder intratracheally to rats by insufflation, bronchoalveolar lavage fluid (BALF) and blood samples were collected up to 24h and DXP and DXM concentrations were determined by HPLC analysis after extraction. PK parameters were evaluated according to a non-compartmental model. We observe that DXP remains for up to 6h in the epithelial lining fluid (ELF) of the lungs at very high concentration. In addition, DXP concentration decreases according to two characteristic times. Consequently, DXM can be detected at rather important concentration in ELF up to 24h. The passage of DXP from the lungs to the bloodstream is very poor whereas DXM seems to be absorbed in the blood more easily. These results suggest that once administered DXP undergoes two different processes: hydrolysis into DXM due to the presence of esterases in the lungs and distribution in the lung tissue. This formulation appears promising to reduce systemic exposure and prolong the effect of the drug locally.

Polysaccharide-coated liposomes by post-insertion of a hyaluronan-lipid conjugate.

Hyaluronan (MW: 1.5 MDa) was linked to a phospholipid (dipalmitoyl phosphatidylethanolamine, DPPE) by an amidification procedure to obtain novel macromolecules (HA-DPPE) able to coat liposomes. Liposomes made of dipalmitoyl phosphatidylcholine and cholesterol (DPPC/Chol: 95/5 molar ratio), with a mean size around 100nm, were incubated with HA-DPPE at 55°C, allowing the insertion of DPPE moieties in the liposomal bilayer and leading to hyaluronan-coated liposomes (HAsomes) as evidenced by several techniques including dynamic light scattering and differential scanning calorimetry. The amount or HA-DPPE coating liposomes was quantified by different methods among which capillary electrophoresis and their stability in serum was finally compared to that of plain liposomes. As a conclusion, we provide insight into the physico-chemical characterization of HA-DPPE and of HAsomes demonstrating that easy coating of phospholipid vesicles can be achieved by post-insertion of a lipid derivative of hyaluronan. This approach represents an innovative strategy for coating vesicular systems to confer them simultaneously with long circulation properties and selective targeting towards HA-receptors.

Impact of lipid composition and photosensitizer hydrophobicity on the efficiency of light-triggered liposomal release.

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.

Quasi-phase-matched gratings printed by all-optical poling in polymer films.

The all-optical poling technique permits polar orientation of molecules. For efficient poling of thin films the relative phases, amplitudes, and polarizations of the two interfering beams must be controlled. We present an original stable one-arm interferometer that is specific to the recording of two-color interference. It relies on the index dispersion of optical glasses. This interference technique permits true real-time nonperturbative monitoring of the polar orientation process and easy all-optical poling of thin-film materials without the need for phase control. This new configuration opens the door to the realization of customized phase-matched wave-guided frequency-conversion devices for the near infrared.