Hydrophobically Modified Ethyl Hydroxyethyl Cellulose Research Articles

Lubricating Performance of Polymer-Coated Liposomes

Dry mouth is a troublesome condition linked to lubrication failure and leads to other diseases such as fungal infections and wounds in the oral cavity. There are many commercial salivary substitutes in the market, but none with a long-lasting lubrication effect. Polymer-coated liposomes can be an interesting formulation strategy for retrieving the symptoms of dry mouth by mimicking the micelles of saliva. In the present study, polymer coated-liposomes were prepared by the conventional thin film method and subsequently coated with three different polymers with different charge densities; alginate, chitosan and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). The prepared polymer-coated liposomes were studied concerning their lubricating properties using a ball-on-disc tribometer at 2 N load at 37 °C, and their flow behaviours were also measured. Solutions of the pure polymers and dispersions of the uncoated liposomes were also studied to investigate any contributions from the individual components. A commercial dry mouth product based on HEC (hydroxyethyl cellulose) and glycerol was also included. The formulations were measured as soon as possible after preparation and some of them after >4 weeks. Results demonstrated that all the positively-charged formulations (chitosan, positive liposomes and chitosan-coated liposomes) had superior lubricating properties with friction coefficients (μ < 0.1) at orally relevant speeds (50 mm/s) as compared to the neutral or negatively-charged systems. At boundary lubrication conditions (3 mm/s), the chitosan-coated liposomes obtained an even lower friction force than the individual components, thus indicating a synergistic effect between the polymer and the liposome.

Electrospinning of non-ionic cellulose ethers/polyvinyl alcohol nanofibers: Characterization and applications

The morphology of spin-coated films and electrospun fibers of ethyl hydroxy ethyl cellulose (EHEC), hydrophobically modified ethyl hydroxy ethyl cellulose (HM-EHEC) and their blends with Poly(vinyl alcohol) (PVA) was examined by AFM, SEM and contact angle measurements. These polysaccharides upon blending with PVA exhibited smooth surface which was evidenced by Atomic Force Microscopy (AFM) observation. The electrospinnability of above polysaccharides with PVA was demonstrated for the first time. The oriented fibers could be obtained using a rotating disc collector. Contact angles of spin-coated films and electrospun fibers were discussed in terms of hydrophobicity and wetting characteristics. Further, The nanofibers of EHEC/PVA were in-situ crosslinked using citric acid and were used for controlled release of an antibacterial drug, Chlorhexidine Digluconate (ChD). In-vitro studies of cytotoxicity, cell growth and cell proliferation were performed using L929 mouse fibroblast cells. These nanofiber mats show potential in drug delivery and as scaffolds in tissue engineering applications.

Polymer coated mucoadhesive liposomes intended for the management of xerostomia

The aim of this work was to prepare and test different pharmaceutical formulations in respect of their potential in relieving dry mouth symptom. Since many of the products available on the market provide only temporary relief to the patients, there is need for new formulations able to retain on the oral mucosa. The prolonged moisture protection could be achieved by combining mucoadhesive materials, such as polymers containing hydrogen bonding groups, with vesicles capable of releasing hydration medium from the inner compartment. In this study three different types of liposomes (positively, negatively and neutrally charged) were coated with five different types of polymers: low-methoxylated pectin (LM-pectin), high-methoxylated pectin (HM-pectin), alginate, chitosan and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). The particle size and the zeta potential of the obtained carriers were tested by measuring dynamic light scattering (DLS) and electrophoretic mobility. Later on, selected positively charged liposomes were deposited on a negatively charged mica surface and depicted by atomic force microscopy (AFM). The water sorption properties of polymers, uncoated liposomes and polymer-coated liposomes were studied by the means of dynamic vapor sorption (DVS). The experiments were performed within the relative humidity range RH=95–0–95%, at 35°C. It was found that coating the liposomes with polymers significantly increased the water sorption capacity of the formulations, making them an attractive choice for hydration of the oral mucosa.

Polymer coated liposomes for use in the oral cavity – a study of the in vitro toxicity, effect on cell permeability and interaction with mucin

In this study we investigated the in vitro toxicity, impact on cell permeability and mucoadhesive potential of polymer-coated liposomes intended for use in the oral cavity. A TR146 cell line was used as a model. The overall aim was to end up with a selection of safe polymer coated liposomes with promising mucoadhesive properties for drug delivery to the oral cavity. The following polymers were tested: chitosan, low-methoxylated pectin (LM-pectin), high-methoxylated pectin (HM-pectin), amidated pectin (AM-pectin), Eudragit, poly(N-isopropylacrylamide-co-methacrylic acid) (p(NIPAAM-co-MAA)), hydrophobically modified hydroxyethyl cellulose (HM-HEC), and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). With chitosan as an exception, all the systems exhibited no significant effect on cell viability and permeability at the considered concentrations. Additionally, all the formulations showed to a varying degree an interaction with mucin (BSM type I-S); the positively charged formulations exhibited the strongest interaction, while the negatively and neutrally charged formulations displayed a moderate or low interaction. The ability to interact with mucin makes all the liposomal formulations promising for oromucosal administration. Although the chitosan-coated liposomes affected the cell viability, this formulation also influenced the cell permeability, which makes it an interesting candidate for systemic drug delivery from the oral cavity.

Mixed solutions of hydrophobically modified graft and block copolymers

Phase separation temperatures and viscosities of dilute and semidilute aqueous mixtures of hydrophobically modified graft and block copolymers have been studied. The graft copolymer was hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC), and the block copolymers were hydrophobically modified poly(ethylene glycol) (HM-PEG) with diblock (DB) or triblock (TB) structures, i.e., modified at one or both ends, respectively. For comparison, viscosity measurements were made also on mixtures of TB with HM-HEC, and on systems where one of the polymers was unmodified (i.e. HM-EHEC/PEG or TB/EHEC). All results indicate mixed hydrophobic associations between graft and block copolymers. Moderate viscosity enhancements were found on addition of HM-PEG to HM-EHEC, and the effects were larger for TB than for DB. The viscosity changes were quite sensitive to the concentration of HM-EHEC.

Gels of Hydrophobically Modified Ethyl(hydroxyethyl) Cellulose Cross-Linked by Amylose: Effects of Hydrophobe Architecture

Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. Here we investigate the complexation of AM with different samples of hydrophobically modified ethyl(hydroxyethyl) cellulose (HMEHEC), distinguished by differences in the architecture of the hydrophobes (the hydrophobic side chains). All hydrophobes, except one, were based on linear alkyl chains, but with varying chain lengths (C12-C14). In addition, some samples contained short hydrophilic "spacers", consisting of 2-5 ethylene oxide units, between the alkyl chains and the EHEC backbone. Gels of varying strength were obtained for the different AM/HMEHEC samples. The alkyl chain length seemed to be the major factor affecting the gel strength, with longer alkyl chains giving stronger gels. For similar alkyl chain lengths, stronger gels were obtained when a spacer was present. Addition of AM caused a small increase of the cloud points of HMEHECs with C14 hydrophobes in water. Time-dependent effects and effects of the sample preparation procedure were also investigated. The reversibility of the gelation with respect to shear was confirmed. A gel destroyed by added surfactant was shown to reform on removal of the surfactant by dialysis.

Time dependent association phenomena in dilute aqueous mixtures of a hydrophobically modified cellulose derivative and an anionic surfactant

Associations in dilute solutions of hydrophobically modified ethyl (hydroxyethyl) cellulose (HM-EHEC) in the presence of an anionic surfactant (sodium dodecyl sulfate (SDS)) are studied with the aid of dynamic light scattering. The autocorrelation functions revealed the existence of two relaxation modes: a single exponential at short times, followed by a stretched exponential at longer times. The slow relaxation time is affected by both polymer and surfactant concentrations. In very dilute polymer solutions the slow relaxation time increases with time at moderate levels of surfactant addition. At higher surfactant concentrations the fast and the slow relaxation time are constant with respect to time. The results are interpreted in terms of a change in the interaction between polymer coils with adsorbed surfactant molecules. The conjecture is that depending on the polymer concentration two scenarios are possible. At low polymer concentrations the polymer–surfactant clusters associate as time passes, forming aggregates. At higher polymer concentrations the polymer–surfactant clusters undergo a conformational transition with time. In both cases a phase separation at long time after mixing is found.

Polymers that reduce intraperitoneal adhesion formation.

Viscous macromolecules and phospholipids have been shown to reduce postoperative adhesion formation. The ideal agent, or combination of agents, still remains to be identified. The effect of hydrophobically modified ethyl (hydroxyethyl) cellulose (HM-EHEC) and polyquarternium-24 (LM-200), two cellulose-derived polymers, and of sphingomyelin, was examined in an animal model. Adhesions were induced in the parietal peritoneum in a standardized manner and quantity, and the morphology of adhesion formation was evaluated after 7 days. A significant reduction in adhesion formation was seen in animals receiving LM-200 (P=0.013) and HM-EHEC (P=0.012) as a short-term treatment compared with controls given saline, but not in animals receiving sphingomyelin (P=0.733). Additional effects were seen in the animals receiving LM-200 as a prolonged treatment (P< 0.001) compared with controls. There was no difference in the magnitude of the inflammatory response between the groups. These results suggest that hydrophobically modified polymers are efficient in reducing adhesions, without affecting the inflammatory response.

Study on Polymer Micelles of Hydrophobically Modified Ethyl Hydroxyethyl Cellulose Using Single-Molecule Force Spectroscopy

Individual hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC) molecules under different conditions were elongated using a new atomic force microscope (AFM) based technique-single-molecule force spectroscopy (SMFS). The critical concentration of HM-EHEC for micelle-like clusters at a solid/liquid interface was around 0.8 wt %, which is lower than that in solution. The different mechanical properties of HM-EHEC below and above the critical concentration were displayed on force-extension curves. Through a comparison with unmodified hydroxyethyl cellulose, substituent-induced effects on nanomechanical features of HM-EHEC were investigated. Because of hydrophobic interactions and cooperative binding with the polymer, surfactants such as sodium dodecyl sulfate (SDS) dramatically influence the elastic properties of HM-EHEC below the critical concentration, and further addition of SDS reduces the interactions between the hydrophobic groups and the surfactant.

Interfacial Interaction between Sodium Dodecyl Sulfate and Hydrophobically Modified Ethyl(hydroxyethyl)cellulose. A Surface Force Study

The effect of addition of sodium dodecyl sulfate (SDS) to a layer of hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC) preadsorbed on hydrophobized mica has been studied with an interferometric surface force apparatus (SFA). The force between the surfaces was always repulsive on both compression and separation. The range of this force, which is 1500 Å for the HM-EHEC layers, undergoes a non-monotonic change on addition of SDS. Initially, at low SDS concentrations the layer expand, while at higher surfactant concentrations a contraction of the adsorbed layer is observed. At 1.5 mM SDS the range of the force is at maximum, while at 6 mM SDS the layer is significantly thinner than before addition of SDS. The results are discussed in terms of polymer−surfactant interfacial association and competitive adsorption. The data obtained by surface force measurements agree qualitatively with ellipsometry findings on the same system.

Colloid Polymer Interactions and Aggregation in Aqueous Mixtures of Polystyrene Latex, Sodium Dodecyl Sulfate, and a Hydrophobically Modified Polymer: A Dynamic Light Scattering Study

The kinetics of clusters formed in the flocculation process of polystyrene latex particles (PSL) in the presence of hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC) and sodium dodecyl sulfate (SDS) in the concentration interval of 2−4 mmolal have been investigated with the aid of dynamic light scattering measurements at different temperatures. For this system (HM-EHEC/SDS/PSL) we observe an intriguing time-dependent cluster growth over a restricted (2−4 mmolal) surfactant concentration range. The rate of flocculation and the aggregation mechanism are affected by both the level of surfactant addition and temperature. The value of the homogeneity exponent λ, used to characterize the aggregation mechanism, depends on temperature and concentration of surfactant. Flocculation behaviors between the reaction-limited and diffusion-limited regimes are observed. The picture that emerges is that polymer−surfactant complexes are adsorbed onto the PSL particles in form of fuzzy layers with hydrophobic s...

Adsorption and Desorption of Unmodified and Hydrophobically Modified Ethyl(hydroxyethyl)cellulose on Polystyrene Latex Particles in the Presence of Ionic Surfactants Using Dynamic Light Scattering

The effect of addition of anionic (sodium dodecyl sulfate, SDS) or cationic (cetyltrimethylammonium bromide, CTAB) surfactant on the hydrodynamic thickness of layers of unmodified (EHEC) and hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC), adsorbed on anionic polystyrene latex particles (PSL), was studied by dynamic light scattering. The hydrodynamic layer thickness of EHEC increases in the presence of SDS or CTAB at low surfactant concentration due to the formation of polymer−surfactant clusters on the particle surfaces, followed by a reduction of this layer at higher levels of surfactant addition. The maximum in hydrodynamic thickness is observed at the critical aggregation concentration (cac) of the respective EHEC−surfactant complex, and the desorption is virtually complete around the critical micelle concentration of the pure surfactant. The interaction peak is more pronounced with SDS than in the presence of the cationic surfactant. For the HM-EHEC/SDS/PSL and HM-EHEC/CTAB/PSL system...

Microstructures formed in aqueous solutions of a hydrophobically modified nonionic cellulose derivative and sodium dodecyl sulfate: a fluorescence probe investigation

The association behavior of hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC) and its interaction with the anionic surfactant sodium dodecyl sulfate (SDS) has been studied in the dilute concentration regime. Steady-state fluorescence probe techniques have been utilized to obtain microstructural information of the system properties and combined with macroscopic bulk information from equilibrium dialysis experiments in order to determine binding isotherms of SDS to HM-EHEC. HM-EHEC was found to self-associate and form polymeric micelles in semi-dilute aqueous solutions. c ∗ for the self-association process was determined to be approximately 0.4%. The microviscosity of the polymeric micelles is much higher, and the micropolarity slightly higher, than that of ordinary SDS micelles. The onset of interaction between HM-EHEC and SDS was evidenced by a simultaneous strong increase in microviscosity and decrease in micropolarity upon successive addition of SDS. There is a minor, noncooperative SDS binding to the HM-EHEC starting from low concentrations of SDS (<5 mM) followed by a highly cooperative binding region at SDS concentrations ≥5 mM. The polymer–surfactant aggregates are rigid and hydrophobic with a maximum in microviscosity in the noncooperative binding region at a very low degree of SDS-adsorption.

Interactions of Polymerized Surfactants and a Polymer

The interactions of polymerized surfactants and hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC) have been investigated in terms of their viscosities. Three polymerizable surfactants used were sodium 10-undecenoate (SUD), sodium 11-(N-ethylacrylamido)undecanoate (SEAAU), and zwitterionic (((acryloyloxy)undecyl)dimethylammonio)acetate (AUMAA). These polysoaps exerted varying degrees of hydrophobic interactions with HMEHEC via the formation of mixed micelles as clusters of physical crosslinks. Polymerized SEAAU showed a 27-fold increase in the viscosity of the mixed system, but the effect was much inferior for the other two systems. The copolymers of the surfactants and styrene also interacted rather strongly with HMEHEC. The dominating effect of electrostatic charges on the viscosity is demonstrated by the marked difference between the system with negatively charged poly(SEAAU) and that with the charge-neutral poly(AUMAA).

Polymer Effects on the Phase Equilibrium of a Balanced Microemulsion: Adsorbing versus Nonadsorbing Polymers

The phase equilibrium of polymer-microemulsion mixtures has been studied. Two polymers with the same cellulose backbone have been examined in comparison: hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC), containing ca. 6.5 hydrophobic «stickers» per molecule versus the unmodified precursor (EHEC). It has been shown that (i) the modified polymer is soluble in the bicontinuous microemulsion phase, whereas the unmodified polymer is not, (ii) HM-EHEC, being dissolved in the bicontinuous phase increases its ultimate swelling in water and, to a less degree, in oil, and (iii) these effects of HM-EHEC on the phase equilibrium disappear at high polymer concentrations