Hyaluronic Acid Scaffolds for Loco-Regional Therapy in Nervous System Related Disorders.

Hyaluronic acid (HA) is a Glycosaminoglycan made of disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. Its molecular mass can reach 10 MDa and its physiological properties depend on its polymeric property, polyelectrolyte feature and viscous nature. HA is a ubiquitous compound found in almost all biological tissues and fluids. So far, HA grades are produced by biotechnology processes, while in the human organism it is a major component of the extracellular matrix (ECM) in brain tissue, synovial fluid, vitreous humor, cartilage and skin. Indeed, HA is capable of forming hydrogels, polymer crosslinked networks that are very hygroscopic. Based on these considerations, we propose an overview of HA-based scaffolds developed for brain cancer treatment, central and peripheral nervous systems, discuss their relevance and identify the most successful developed systems.

Quantification of the dissolved inorganic carbon species and of the pH of alkaline solutions exposed to CO2 under pressure: a novel approach by Raman scattering.

Dissolved inorganic carbon (DIC) content of aqueous systems is a key function of the pH, of the total alkanility (TA), and of the partial pressure of CO2. However, common analytical techniques used to determine the DIC content in water are unable to operate under high CO2 pressure. Here, we propose to use Raman spectroscopy as a novel alternative to discriminate and quantitatively monitor the three dissolved inorganic carbon species CO2(aq), HCO3(-), and CO3(2-) of alkaline solutions under high CO2 pressure (from P = 0 to 250 bar at T = 40 °C). In addition, we demonstrate that the pH values can be extracted from the molalities of CO2(aq) and HCO3(-). The results are in very good agreement with those obtained from direct spectrophotometric measurements using colored indicators. This novel method presents the great advantage over high pressure conventional techniques of not using breakable electrodes or reference additives and appears of great interest especially in marine biogeochemistry, in carbon capture and storage and in material engineering under high CO2 pressure.

Polymer-lipid hybrid nanomedicines to deliver siRNA in and against glioblastoma cells.

Small interfering RNA (siRNA) holds great potential to treat many difficult-to-treat diseases, but its delivery remains the central challenge. This study aimed at investigating the suitability of polymer-lipid hybrid nanomedicines (HNMeds) as novel siRNA delivery platforms for locoregional therapy of glioblastoma. Two HNMed formulations were developed from poly(lactic-co-glycolic acid) polymer and a cationic lipid: 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or 3ß-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol). After characterization of the HNMeds, a model siRNA was complexed onto their surface to form HNMed/siRNA complexes. The physicochemical properties and siRNA binding ability of complexes were assessed over a range of nitrogen-to-phosphate (N/P) ratios to optimize the formulations. At the optimal N/P ratio of 10, complexes effectively bound siRNA and improved its protection from enzymatic degradation. Using the NIH3T3 mouse fibroblast cell line, DOTAP-based HNMeds were shown to possess higher cytocompatibility in vitro over the DC-Chol-based ones. As proof-of-concept, uptake and bioefficacy of formulations were also assessed in vitro on U87MG human glioblastoma cell line expressing luciferase gene. Complexes were able to deliver anti-luciferase siRNA and induce a remarkable suppression of gene expression. Noteworthy, the effect of DOTAP-based formulation was not only about three-times higher than DC-Chol-based one, but also comparable to lipofectamine model transfection reagent. These findings set the basis to exploit this nanosystem for silencing relevant GB-related genes in further in vitro and in vivo studies.

Implantable SDF-1α-loaded silk fibroin hyaluronic acid aerogel sponges as an instructive component of the glioblastoma ecosystem: Between chemoattraction and tumor shaping into resection cavities.

In view of inevitable recurrences despite resection, glioblastoma (GB) is still an unmet clinical need. Dealing with the stromal-cell derived factor 1-alpha (SDF-1α)/CXCR4 axis as a hallmark of infiltrative GB tumors and with the resection cavity situation, the present study described the effects and relevance of a new engineered micro-nanostructured SF-HA-Hep aerogel sponges, made of silk fibroin (SF), hyaluronic acid (HA) and heparin (Hep) and loaded with SDF-1α, to interfere with the GB ecosystem and residual GB cells, attracting and confining them in a controlled area before elimination. 70 µm-pore sponges were designed as an implantable scaffold to trap GB cells. They presented shape memory and fit brain cavities. Histological results after implantation in brain immunocompetent Fischer rats revealed that SF-HA-Hep sponges are well tolerated for more than 3 months while moderately and reversibly colonized by immuno-inflammatory cells. The use of human U87MG GB cells overexpressing the CXCR4 receptor (U87MG-CXCR4+) and responding to SDF-1α allowed demonstrating directional GB cell attraction and colonization of the device in vitro and in vivo in orthotopic resection cavities in Nude rats. Not modifying global survival, aerogel sponge implantation strongly shaped U87MG-CXCR4+ tumors in cavities in contrast to random infiltrative growth in controls. Overall, those results support the interest of SF-HA-Hep sponges as modifiers of the GB ecosystem dynamics acting as "cell meeting rooms" and biocompatible niches whose properties deserve to be considered toward the development of new clinical procedures. STATEMENT OF SIGNIFICANCE: Brain tumor glioblastoma (GB) is one of the worst unmet clinical needs. To prevent the relapse in the resection cavity situation, new implantable biopolymer aerogel sponges loaded with a chemoattractant molecule were designed and preclinically tested as a prototype targeting the interaction between the initial tumor location and its attraction by the peritumoral environment. While not modifying global survival, biocompatible SDF1-loaded hyaluronic acid and silk fibroin sponges induce directional GB cell attraction and colonization in vitro and in rats in vivo. Interestingly, they strongly shaped GB tumors in contrast to random infiltrative growth in controls. These results provide original findings on application of exogenous engineered niches that shape tumors and serve as cell meeting rooms for further clinical developments.

Fluorescent self-assembled monolayers of umbelliferone: a relationship between contact angle and fluorescence.

Self-assembled monolayers (SAMs) that contain fluorophore units are nowadays widely used to tune surface properties and design new chemical sensor chips. It is well-known that the nature of the substrate may strongly interfere with the emission properties of the grafted molecules, but the organization of the monolayer may also have an important role. To study the influence of the SAM organization on the luminescence properties, we prepared different coumarin-based derivatives endowed with tethered chains of different lengths and elaborated the corresponding SAMs on glass slides. Besides SAM structural characterizations by atomic force microscopy and X-ray reflectivity, we carried out contact angle measurements and applied the Van Oss-Chaudhury-Good theory, which was rarely used previously for self-assembled monolayers. As expected, by increasing the tethered chain length, a higher surface coverage, a higher degree of organization, and a stronger molecular packing were observed. However, it appears to facilitate the self-quenching process, and thus, this strongly affects the fluorescent properties of the SAMs.

Insights into Healthcare Professionals' Perceptions and Attitudes toward Nanotechnological Device Application: What Is the Current Situation in Glioblastoma Research?

Nanotechnology application in cancer treatment is promising and is likely to quickly spread worldwide in the near future. To date, most scientific studies on nanomaterial development have focused on deepening the attitudes of end users and experts, leaving clinical practice implications unexplored. Neuro-oncology might be a promising field for the application of nanotechnologies, especially for malignant brain tumors with a low-survival rate such as glioblastoma (GBM). As to improving patients' quality of life and life expectancy, innovative treatments are worth being explored. Indeed, it is important to explore clinicians' intention to use experimental technologies in clinical practice. In the present study, we conducted an exploratory review of the literature about healthcare workers' knowledge and personal opinions toward nanomedicine. Our search (i) gives evidence for disagreement between self-reported and factual knowledge about nanomedicine and (ii) suggests the internet and television as main sources of information about current trends in nanomedicine applications, over scientific journals and formal education. Current models of risk assessment suggest time-saving cognitive and affective shortcuts, i.e., heuristics support both laypeople and experts in the decision-making process under uncertainty, whereas they might be a source of error. Whether the knowledge is poor, heuristics are more likely to occur and thus clinicians' opinions and perspectives toward new technologies might be biased.

Optimization of an Injectable Hydrogel Depot System for the Controlled Release of Retinal-Targeted Hybrid Nanoparticles.

A drawback in the development of treatments that can reach the retina is the presence of barriers in the eye that restrain compounds from reaching the target. Intravitreal injections hold promise for retinal delivery, but the natural defenses in the vitreous can rapidly degrade or eliminate therapeutic molecules. Injectable hydrogel implants, which act as a reservoir, can allow for long-term drug delivery with a single injection into the eye, but still suffer due to the fast clearance of the released drugs when traversing the vitreous and random diffusion that leads to lower pharmaceutic efficacy. A combination with HA-covered nanoparticles, which can be released from the gel and more readily pass through the vitreous to increase the delivery of therapeutic agents to the retina, represents an advanced and elegant way to overcome some of the limitations in eye drug delivery. In this article, we developed hybrid PLGA-Dotap NPs that, due to their hyaluronic acid coating, can improve in vivo distribution throughout the vitreous and delivery to retinal cells. Moreover, a hydrogel implant was developed to act as a depot for the hybrid NPs to better control and slow their release. These results are a first step to improve the treatment of retinal diseases by protecting and transporting the therapeutic treatment across the vitreous and to improve treatment options by creating a depot system for long-term treatments.

Dynamical and rheological properties of fluorinated surfactant films adsorbed at the pressurized CO2-H2O interface.

The dynamics of adsorption, interfacial tension, and rheological properties of two phosphocholine-derived partially fluorinated surfactants FnHmPC, designed to compensate for the weak CO(2)-surfactant tail interactions, were determined at the pressurized CO(2)-H(2)O interface. The two surfactants differ only by the length of the hydrocarbon spacer (5 CH(2) in F8H5PC and 11 CH(2) in F8H11PC) located between the terminal perfluoroalkyl chain and the polar head. The length of this spacer was found to have a critical impact on the adsorption kinetics and elasticity of the interfacial surfactant film. F8H5PC is soluble in both water and CO(2) phases and presents several distinct successive interfacial behaviors when bulk water concentration (C(W)) increases and displays a nonclassical isotherm shape. The isotherms of F8H5PC are similar for the three CO(2) pressures investigated and comprise four regimes. In the first regime, at low C(W), the interfacial tension is controlled by the organization that occurs between H(2)O and CO(2). The second regime corresponds to the adsorption of the surfactant as a monolayer until the CO(2) phase is saturated with F8H5PC, resulting in a first inflection point. In this regime, F8H5PC molecules reach maximal compaction and display the highest apparent interfacial elasticity. In the third regime, a second inflection is observed that corresponds to the critical micelle concentration of the surfactant in water. At the highest concentrations (fourth regime), the interfacial films are purely viscous and highly flexible, suggesting the capacity for this surfactant to produce water-in-CO(2) microemulsion. In this regime, surfactant adsorption is very fast and equilibrium is reached in less than 100 s. The behavior of F8H11PC is drastically different: it forms micelles only in the water phase, resulting in a classical Gibbs interface. This surfactant decreases the interfacial tension down to 1 mN/m and forms a strongly elastic interface. As this surfactant forms a very cohesive interface, it should be suitable for formulating stable water-in-CO(2) emulsions. The finding that the length of the hydrocarbon spacer in partially fluorinated surfactants can drastically influence film properties at the CO(2)-H(2)O interface should help control the formation of microemulsions versus emulsions and help elaborate a rationale for the design of surfactants specifically adapted to pressurized CO(2).

Nanoparticle-containing electrospun nanofibrous scaffolds for sustained release of SDF-1α.

Chemokines such as stromal cell-derived factor-1α (SDF-1α) regulate the migration of cancer cells that can spread from their primary tumor site by migrating up an SDF-1α concentration gradient, facilitating their local invasion and metastasis. Therefore, the implantation of SDF-1α-releasing scaffolds can be a useful strategy to trap cancer cells expressing the CXCR4 receptor. In this work, SDF-1α was encapsulated into poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles and subsequently electrospun with chitosan to produce nanofibrous scaffolds of average fiber diameter of 261 ± 45 nm, intended for trapping glioblastoma (GBM) cells. The encapsulated SDF-1α maintained its biological activity after the electrospinning process as assessed by its capacity to induce the migration of cancer cells. The scaffolds could also provide sustained release of SDF-1α for at least 5 weeks. Using NIH3T3 mouse fibroblasts, human Thp-1 macrophages, and rat primary astrocytes we showed that the scaffolds possessed high cytocompatibility in vitro. Furthermore, a 7-day follow-up of Fischer rats bearing implanted scaffolds demonstrated the absence of adverse effects in vivo. In addition, the nanofibrous structure of the scaffolds provided excellent anchoring sites to support the adhesion of human GBM cells by extension of their pseudopodia. The scaffolds also demonstrated slow degradation kinetics, which may be useful in maximizing the time window for trapping GBM cells. As surgical resection does not permit a complete removal of GBM tumors, our results support the future implantation of these scaffolds into the walls of the resection cavity to evaluate their capacity to attract and trap the residual GBM cells in the brain.

Impact of the physico-chemical properties of polymeric microspheres functionalized with cell adhesion molecules on the behavior of mesenchymal stromal cells.

Polymeric, biodegradable, microspheres (MS) presenting a biomimetic surface of extracellular matrix (ECM) proteins are currently used for transporting cells and/or encapsulated proteins for regenerative medicine studies. They can be made of (lactic-co-glycolic acid) (PLGA) or of a more hydrophilic PLGA-P188 (Poloxamer188)-PLGA polymer allowing for the complete release of the therapeutic proteins. They promote stem cell adhesion, cell survival and differentiation after transplantation. Although the biological effectiveness of these microcarriers is established, a detailed understanding of the protein and cell interactions with the microcarrier surface remain unclear due to a lack of information of their surface properties. The aim of this study was to characterize the physicochemical properties of two polymeric MS systems and determine the effect of laminin and poly-d-lysine coated microcarriers on stem cell adhesion, survival and neuronal differentiation. The hydrophobicity and topography of PLGA MS promoted protein adsorption and the stem cells quickly adhered and spread on the surface of these microcarriers. In contrast less proteins adsorbed onto PLGA-P188-PLGA MS and although cells adhered to these microcarriers, they remained round and did not spread on their surface. Despite these early-stage differences, our results suggest that the nature of the MS does not strongly influence the long-term cell behavior. The cells exhibit the same cell number, differentiation profile and ability to secrete ECM molecules regardless of the type of microcarrier used. Likely the ECM molecules that form a microenvironment around both of these 3D microcarrier/cell constructs over time play a role in this converging cell behavior. We have thus furthered our understanding of the physicochemical properties of polymeric cell carriers affecting stem cell behavior to help tailor suitable microcarriers for neuroregenerative applications.

Curdlan-Chitosan Electrospun Fibers as Potential Scaffolds for Bone Regeneration.

Polysaccharides have received a lot of attention in biomedical research for their high potential as scaffolds owing to their unique biological properties. Fibrillar scaffolds made of chitosan demonstrated high promise in tissue engineering, especially for skin. As far as bone regeneration is concerned, curdlan (1,3-ß-glucan) is particularly interesting as it enhances bone growth by helping mesenchymal stem cell adhesion, by favoring their differentiation into osteoblasts and by limiting the osteoclastic activity. Therefore, we aim to combine both chitosan and curdlan polysaccharides in a new scaffold for bone regeneration. For that purpose, curdlan was electrospun as a blend with chitosan into a fibrillar scaffold. We show that this novel scaffold is biodegradable (8% at two weeks), exhibits a good swelling behavior (350%) and is non-cytotoxic in vitro. In addition, the benefit of incorporating curdlan in the scaffold was demonstrated in a scratch assay that evidences the ability of curdlan to express its immunomodulatory properties by enhancing cell migration. Thus, these innovative electrospun curdlan-chitosan scaffolds show great potential for bone tissue engineering.

Relating polymeric microparticle formulation to prevalence or distribution of fibronectin and poly-d-lysine to support mesenchymal stem cell growth.

Protein-coated polymer-based microparticles are attractive supports for cell delivery, but the interplay between microparticle properties, protein coating, and cell response is poorly understood. The interest in alternative microparticle formulations increases the need for a better understanding of how functional protein coatings form on different microparticles. In this work, microparticle formulations based on biodegradable polymers [poly (lactic-co-glycolic acid) (PLGA) and the triblock copolymer PLGA-poloxamer-PLGA] were prepared via an emulsion-based process. To explore the impact that the use of a surfactant has on the properties of the microparticles, the emulsion was stabilized by using either a surfactant, poly(vinyl alcohol), or an organic solvent, propylene glycol. Four different types of microparticles were prepared through combinations of the two types of polymers and the two types of stabilizers. The coating of microparticles with proteins/polypeptides such as fibronectin and poly-d-lysine has been demonstrated before and is an integral step for their application as microcarriers, e.g., for cell delivery; however, the impact of the microparticles' surface chemical properties on the formation (prevalence and distribution) of the mixed polypeptide coatings and the influence on subsequent cell attachment remain to be elucidated. Using a colocalization analysis approach on ToF-SIMS images of protein-coated microparticles, we show that the use of propyleneglycol over PVA as well as the substitution of PLGA by the triblock copolymer resulted in enhanced protein adsorption. Furthermore, if propyleneglycol is used, the substitution of PLGA with the triblock copolymer leads to increased stem cell adhesion.

Rapamycin-Loaded Lipid Nanocapsules Induce Selective Inhibition of the mTORC1-Signaling Pathway in Glioblastoma Cells.

Inhibition of the PI3K/Akt/mTOR signaling pathway represents a potential issue for the treatment of cancer, including glioblastoma. As such, rapamycin that inhibits the mechanistic target of rapamycin (mTOR), the downstream effector of this signaling pathway, is of great interest. However, clinical development of rapamycin has floundered due to the lack of a suitable formulation of delivery systems. In the present study, a novel method for the formulation of safe rapamycin nanocarriers is investigated. A phase inversion process was adapted to prepare lipid nanocapsules (LNCs) loaded with the lipophilic and temperature sensitive rapamycin. Rapamycin-loaded LNCs (LNC-rapa) are ~110 nm in diameter with a low polydispersity index (<0.05) and the zeta potential of about -5 mV. The encapsulation efficiency, determined by spectrophotometry conjugated with filtration/exclusion, was found to be about 69%, which represents 0.6 wt% of loading capacity. Western blot analysis showed that LNC-rapa do not act synergistically with X-ray beam radiation in U87MG glioblastoma model in vitro. Nevertheless, it demonstrated the selective inhibition of the phosphorylation of mTORC1 signaling pathway on Ser2448 at a concentration of 1 µM rapamycin in serum-free medium. Interestingly, cells cultivated in normoxia (21% O2) seem to be more sensitive to mTOR inhibition by rapamycin than those cultivated in hypoxia (0.4% O2). Finally, we also established that mTOR phosphorylation inhibition by LNC-rapa induced a negative feedback through the activation of Akt phosphorylation. This phenomenon was more noticeable after stabilization of HIF-1α in hypoxia.

Aerogel sponges of silk fibroin, hyaluronic acid and heparin for soft tissue engineering: Composition-properties relationship.

This work aims to design biocompatible aerogel sponges that can host and control the release of stromal cell-derived factor-1α (SDF-1α or CXCL12), a key protein for applications ranging from regenerative medicine to cancer therapy (notably for neural tissues). Miscibility of silk fibroin (SF) and hyaluronic acid (HA) was investigated by means of fluorescence and scanning electron microscopy to identify processing conditions. Series of freeze-dried sponges were prepared by associating and cross-linking within the same 3D structure, HA, SF, poly-l-lysine (PLL) and heparin (hep). Aerogel sponges presented high swelling degree and porosity (∼90 %), adequate mean pore diameter (ca. 60 µm) and connectivity for welcoming cells, and a soft texture close to that of the brain (6-13 kPa Young's Modulus). Addition of SF yielded sponges with slower biodegradation. SF-HA and SF-HA-hep sponges retained 75 % and 93 % of the SDF-1α respectively after 7 days and were found to be cytocompatible in vitro.

Synthesis, Characterization, and In Vitro Studies of an Reactive Oxygen Species (ROS)-Responsive Methoxy Polyethylene Glycol-Thioketal-Melphalan Prodrug for Glioblastoma Treatment.

Glioblastoma (GBM) is the most frequent and aggressive primary tumor of the brain and averages a life expectancy in diagnosed patients of only 15 months. Hence, more effective therapies against this malignancy are urgently needed. Several diseases, including cancer, are featured by high levels of reactive oxygen species (ROS), which are possible GBM hallmarks to target or benefit from. Therefore, the covalent linkage of drugs to ROS-responsive molecules can be exploited aiming for a selective drug release within relevant pathological environments. In this work, we designed a new ROS-responsive prodrug by using Melphalan (MPH) covalently coupled with methoxy polyethylene glycol (mPEG) through a ROS-cleavable group thioketal (TK), demonstrating the capacity to self-assembly into nanosized micelles. Full chemical-physical characterization was conducted on the polymeric-prodrug and proper controls, along with in vitro cytotoxicity assayed on different GBM cell lines and "healthy" astrocyte cells confirming the absence of any cytotoxicity of the prodrug on healthy cells (i.e. astrocytes). These results were compared with the non-ROS responsive counterpart, underlining the anti-tumoral activity of ROS-responsive compared to the non-ROS-responsive prodrug on GBM cells expressing high levels of ROS. On the other hand, the combination treatment with this ROS-responsive prodrug and X-ray irradiation on human GBM cells resulted in an increase of the antitumoral effect, and this might be connected to radiotherapy. Hence, these results represent a starting point for a rationale design of innovative and tailored ROS-responsive prodrugs to be used in GBM therapy and in combination with radiotherapy.

Comparative whole corona fingerprinting and protein adsorption thermodynamics of PLGA and PCL nanoparticles in human serum.

Nanoparticles (NPs) based on biocompatible and biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) represent effective systems for systemic drug delivery. Upon injection into the blood circuit, the NP surface is rapidly modified due to adsorption of proteins that form a 'protein corona' (PC). The PC plays an important role in cellular targeting, uptake and NP bio-distribution. Hence, the study of interactions between NPs and serum proteins appears as key for biomedical applications and safety of NPs. In the present work, we report on the comparative protein fluorescence quenching extent, thermodynamics of protein binding and identification of proteins in the soft and hard corona layers of PLGA and PCL NPs. NPs were prepared via a single emulsion-solvent evaporation technique and characterized with respect to size, zeta potential, surface morphology and hydrophobicity. Protein fluorescence quenching experiments were performed against human serum albumin. The thermodynamics of serum protein binding onto the NPs was studied using isothermal titration calorimetry. Semi-quantitative analysis of proteins in the PC layers was conducted using gel electrophoresis and mass spectrometry using human serum. Our results demonstrated the influence of particle hydrophobicity on the thermodynamics of protein binding. Human serum proteins bind to a greater extent and with greater affinity to PCL NPs than PLGA NPs. Several proteins were detected in the hard and soft corona of the NPs, representing their unique proteome fingerprints. Some proteins were unique to the PCL NPs. We anticipate that our findings will assist with rational design of polymeric NPs for effective drug delivery applications.

Reversing the Tumor Target: Establishment of a Tumor Trap.

Despite the tremendous progress made in the field of cancer therapy in recent years, certain solid tumors still cannot be successfully treated. Alongside classical treatments in the form of chemotherapy and/or radiotherapy, targeted treatments such as immunotherapy that cause fewer side effects emerge as new options in the clinics. However, these alternative treatments may not be useful for treating all types of cancers, especially for killing infiltrative and circulating tumor cells (CTCs). Recent advances pursue the trapping of these cancer cells within a confined area to facilitate their removal for therapeutic and diagnostic purposes. A good understanding of the mechanisms behind tumor cell migration may drive the design of traps that mimic natural tumor niches and guide the movement of the cancer cells. To bring this trapping idea into reality, strong efforts are being made to create structured materials that imitate myelinated fibers, blood vessels, or pre-metastatic niches and incorporate chemical cues such as chemoattractants or adhesive proteins. In this review, the different strategies used (or could be used) to trap tumor cells are described, and relevant examples of their performance are analyzed.

Interactions between poly(ethylene glycol) and protein in dichloromethane/water emulsions: a study of interfacial properties.

From adsorption kinetics and interfacial rheological studies performed by using a pendant-drop method, i.e. in conditions close to those of the primary emulsion of the water-in-oil-in-water emulsion-encapsulation technique, it was shown that adsorption of the hen egg-white lysozyme (HEWL) at the water/dichloromethane (DCM) interface can be efficiently slowed down by modulating some parameters. It was shown that a decrease of the ionic strength of the aqueous phase, and the optimization of the density of the poly(ethylene glycol) (PEG) adsorbed film by increasing the PEG concentration or by modulating the polymer chain length, can significantly decrease the rate of adsorption of HEWL at the water/DCM interface. Moreover, it was shown that the choice of the dissolution phase of PEG (DCM or water) clearly influences the results.

Dilational viscoelasticity and relaxation properties of interfacial electrostatic complexes between oppositely charged hydrophobic and hydrophilic polyelectrolytes.

Strongly adsorbing hydrophobic cationic polyelectrolyte, Eudragit RS, containing approximately 2.5 mol% of pendent hydrophilic trimethylammonium (TMA) groups irreversibly adsorbs from its methylene chloride (MCl) solution at the MCl/water interface and forms solid-like adsorption layers (ALs). Submitted to periodic dilational deformations with the standard radial frequency omega(0)=0.63 rad/s, these ALs exhibit relatively high dilational storage modulus E' approximately 20 mN/m and practically zero loss modulus E'' at the bulk concentration C(Eud)=4 x 10(-3)g/L. The frequency scanning of these ALs in the diapason omega=0.01-0.63rad/s and the approximation of the experimental dependences E'(omega) and E''(omega) by two relaxation times rheological model makes it possible to estimate the crossing frequency of these ALs determined from the condition E'(omega(c))=E''(omega(c)) as omega(c) approximately 5 x 10(-4)rad/s. Upon dissolving the hydrophilic anionic polyelectrolyte, chitosan sulfate (ChS), in the water phase (C(ChS)=3 x 10(-2)g/L) the electrostatic interpolyelectrolyte complexes form at the MCl/water interface. The elasticity moduli E' and E'' of these mixed AL did not undergo remarkable variations, but the crossing frequency is sharply increased by approximately 10 times becoming equal to omega(c) congruent with 3 x 10(-3)rad/s. The increase of omega(c) certifies for the liquefaction of mixed Eudragit RS/ChS adsorption layers. A remarkable decrease of the storage modulus down to E'=8 mN/m and simultaneous increase of the crossing frequency up to omega(c) congruent with 10(-2)rad/s occurs upon increasing the concentrations of both components, Eudragit RS and ChS, up to 0.1g/L. The liquefaction effect in the mixed ALs of oppositely charged polyelectrolytes was explained on the basis of the proposed relaxation mechanism. The effect of the liquefaction of adsorption layers of strongly adsorbing hydrophobic polyelectrolytes by formation of interpolyelectrolyte complexes with hydrophilic polyelectrolytes must be taken into account in the production of nano-capsules and nano-fibers.

Development of a non-toxic and non-denaturing formulation process for encapsulation of SDF-1α into PLGA/PEG-PLGA nanoparticles to achieve sustained release.

Chemokines are known to stimulate directed migration of cancer cells. Therefore, the strategy involving gradual chemokine release from polymeric vehicles for trapping cancer cells is of interest. In this work, the chemokine stromal cell-derived factor-1α (SDF-1α) was encapsulated into nanoparticles composed of poly-(lactic-co-glycolic acid) (PLGA) and a polyethylene glycol (PEG)-PLGA co-polymer to achieve sustained release. SDF-1α, and lysozyme as a model protein, were firstly precipitated to promote their stability upon encapsulation. A novel phase separation method utilising a non-toxic solvent in the form of isosorbide dimethyl ether was developed for the individual encapsulation of SDF-1α and lysozyme precipitates. Uniform nanoparticles of 200-250 nm in size with spherical morphologies were successfully synthesised under mild formulation conditions and conveniently freeze-dried in the presence of hydroxypropyl-ß-cyclodextrin as a stabiliser. The effect of PLGA carboxylic acid terminal capping on protein encapsulation efficiency and release rate was also explored. Following optimisation, sustained release of SDF-1α was achieved over a period of 72 h. Importantly, the novel encapsulation process was found to induce negligible protein denaturation. The obtained SDF-1α nanocarriers may be subsequently incorporated within a hydrogel or other scaffolds to establish a chemokine concentration gradient for the trapping of glioblastoma cells.