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Fractal analysis can be properly applied to complex structures, like physical and chemical networks formed by particles or polymers, when they exhibit self-similarity over an extended range of length scales and, hence, can be profitably used not only for their morphological characterization but also for individuating possible relationships between morphology and mechanisms of aggregation and crosslinking, as well as between morphology and physical properties. Several experimental methods are available to determine the fractal dimension of gel networks, including various scattering techniques and microscopies, permeability measurements and rheology. The present study regards the self-assembly kinetics of High Methoxyl Pectin (HMP) solutions with different pectin and sucrose concentrations investigated by rheological measurements to highlight the effects of pectin and sucrose concentrations on the gel point and to evaluate the degree of compactness of the incipient gel networks through an interpretation of the viscoelastic response at the sol-gel transition.

The study concerns the development of rheological properties of aqueous TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)-oxidized nanofibrillated cellulose (NFC) suspensions prepared from a commercially available TEMPO-NFC powder. Ageing of hydrogels with concentrations from 1 to 3 wt% of TEMPO-NFC was investigated by monitoring shear flow and linear viscoelastic properties after different days from sample preparation. For quantitative representation of the results time dependencies of zero shear viscosity and storage modulus are given. The increase of rheological parameters is described by a sigmoidal mathematical model. By superposition of individual data sets master curves displaying reduced values of the most significant parameters are constructed, showing the effect of ageing kinetics. The reduced storage modulus and zero-shear viscosity values increase for 2 and 3 decades, respectively, before reaching final values. Obtained results are useful for several applications of nanocellulose hydrogels, especially for those, where pumping, mixing, coating or injecting is necessary. For example, in biomedical field, a less viscous suspension can be injected to the spot of interest, where the final gel properties are developed.

The aim of this work is the evaluation of the addition of Moringa leaf powder (MLP) in cookies in terms of antioxidant properties, dough processability and sensorial properties of the cookies. The total content of biophenols and flavonoids in MLP was detected and the identification of the bioactive molecules was performed by HPLC-ESI-TOF-MS measurements, before and after oven treatment at 180 ◦C for 20 min. After a preliminary evaluation of the MLP water soluble fraction (MLPsf) cytotoxicity, its protective effect against an oxidative injury induced in the SH-SY5Y cells was assessed. Data evidence that the bioactive molecules present in MLPsf are effective in preventing ROS production and in protecting neuronal cells against oxidative stress. Prototypes of cookies containing MLP in different concentrations were then produced and evaluated by a consumer panel. Selected doughs containing MLP were analysed to determine the total content of biophenols in the cookies after baking and their enrichment in terms of valuable chemical elements. The influence of MLP on the viscoelastic behaviour and morphology of the doughs was also assessed. Finally, the potential role in counteracting the insurgence of not treatable neurodegenerative pathologies of two main MLP components, glucomoringin and kaempferol derivatives, present also after the thermal treatment, was discussed.

Hydrogels for complex and chronic wound dressings must be conformable, absorb and retain wound exudates and maintain hydration. They can incorporate and release bioactive molecules that can accelerate the healing process. Wound dressings have to be in contact with the wound and epidermis, even for long periods, without causing adverse effects. Hydrogel dressing formulations based on biopolymers derived from terrestrial or marine flora can be relatively inexpensive and well tolerated. In the present article hydrogel films composed by agarose (1.0 wt%), κ-carrageenan at three different concentrations (0.5, 1.0 and 1.5 wt%) and glycerol (3.0 wt%) were prepared without recourse to crosslinking agents, and characterized for their mechanical properties, morphology, swelling and erosion behavior. The films resulted highly elastic and able to absorb and retain large amounts of fluids without losing their integrity. One of the films was loaded with the aqueous extract from Cryphaea heteromalla (Hedw.) D. Mohr for its antioxidant properties. Absence of cytotoxicity and ability to reduce the oxidative stress were demonstrated on NIH-3T3 fibroblast cell cultures. These results encourage further biological evaluations to assess their impact on the healing process.

BACKGROUND: Laminopathies are genetic diseases caused by mutations in the nuclear lamina. OBJECTIVE: Given the clinical impact of laminopathies, understanding mechanical properties of cells bearing lamin mutations will lead to advancement in the treatment of heart failure. METHODS: Atomic force microscopy (AFM) was used to analyze the viscoelastic behavior of neonatal rat ventricular myocyte cells expressing three human lamin A/C gene (LMNA) mutations. RESULTS: Cell storage modulus is characterized, by two plateaus, one in the low frequency range, a second one at higher frequencies. The loss modulus instead shows a “bell” shape with a relaxation toward fluid properties at lower frequencies. Mutations shift the relaxation to higher frequencies, rendering the networks more solid-like. Is interesting that this increase of mutations stiffness (solid like behavior) is at frequencies around 1 Hz, close to the human heart rate. CONCLUSIONS: These features result from a combination of the properties of cytoskeleton filaments and their temporary cross-linker. Our results substantiate that cross-linked filaments contribute for the most part of the mechanical strength of the cytoskeleton cell studied and the relaxation time is determined by the dissociation dynamics of the cross-linking proteins. The severity of biomechanical defects due to these LMNA mutations correlated with the severity of the clinical phenotype.

The viscoelastic and flow properties of aqueous Laponite/TEMPO-oxidized nanofibrillated cellulose (TEMPO-NFC) systems are investigated with the aim to study the effect of content and proportion of both components on the properties. Both Laponite and TEMPO-NFC aqueous dispersions can find numerous applications in different fields (from industrial to biomedical one) due to their structural and rheological properties. The most important effects of blending are observed at low Laponite fractions, also with qualitative changes in the shape of the flow curves and mechanical spectra. Positive synergistic effects are ascribed to the interpenetration and electrostatic interactions between TEMPO-NFC fibrils and Laponite nanodisks. These mechanisms are more effective in Laponite-poor blends when a minority of clay nanoparticles and its aggregated forms are distributed within the nanocellulose matrix, acting as bridging agents between polymer nanofibrils. The synergistic effects are compared to those observed for Laponite blends with a nonionic biopolymer, scleroglucan.

The combination of Low-Field NMR relaxometry (LF-NMR) and rheological analyses was used to investigate the kinetics of aging and structural evolution of salt-free aqueous Laponite dispersions with concentrations ranging from 0.33 to 2.00 wt%. The examination of LF-NMR results reveals that the rate of nanoclay delamination increases with increasing Laponite concentration while its degree decreases. Furthermore, the LF-NMR results were interpreted together with rheological results to assess the kinetics of processes occurring on different length scales reflecting on the time evolution of the three-dimensional structure. The structural evolution is described by the definition and comparison of three different characteristic times. The LF-NMR decay time (tr) designates the time required for Laponite delamination. The induction time (ti) indicates when interparticle edge-face interactions become effective enough for incipient networking. The gelation time (tg) corresponds to sufficiently high degree of interparticle connectivity for the development of a macroscopic gel behavior. The comparison of ti and tg, on one hand, and tr, on the other hand, allows to conclude that for low concentration Laponite dispersions nanoclay delamination is a prerequisite for the formation of the new dispersion structure with a macroscopic gel behavior. Interestingly, the development of the new structure, based on orientation of clay disks into edge-to-face pattern and mutual interparticle attractive interactions, starts when the delamination process is still running.

The present data concern the structuring kinetics of aqueous high methoxyl pectin (HMP) solutions at acid pH (3.1), constant pectin concentration (0.2% w/w) and sucrose concentrations ranging from 56 to 65% w/w. Consecutive frequency sweep was applied to samples immediately after their preparation. The generalized Maxwell (gM) model was used to describe the change of the mechanical spectra for each different sucrose concentration and to determine the viscoelastic parameters controlling the gelation of the HMP solutions. The viscosities in the sol region are explored in the range 0 to 55% 0 to 40% (w/w) sucrose concentration.

Background: The new concepts of personalized and precision medicine require the design of more and more refined delivery systems. In this frame, hydrogels can play a very important role as they represent the best surrogate of soft living tissues for what concerns rheological properties. Thus, this paper focusses on a global theoretical approach able to describe how hydrogel polymeric networks can affect the release kinetics of drugs characterized by different sizes. The attention is focused on a case study dealing with an interpenetrated hydrogel made up by alginate and poly(N-vinyl-2-pyrrolidone). Methods: Information about polymeric network characteristics (mesh size distribution and polymer volume fraction) is deduced from the theoretical interpretation of the rheological and the low field Nuclear Magnetic Resonance (NMR) characterization of hydrogels. This information is then, embodied in the mass balance equation whose resolution provides the release kinetics. Results: Our simulations indicate the influence of network characteristics on release kinetics. In addition, the reliability of the proposed approach is supported by the comparison of the model outcome with experimental release data. Conclusions: This study underlines the necessity of a global theoretical approach in order to design reliable delivery systems based on hydrogels.

Viscosupplementation is an intra-articular symptomatic treatment of mild osteoarthritis in synovial joints. It normally consists of single or repeated injections of hyaluronan- based fluids, aimed to restore desirable viscoelastic behavior of the synovial fluid and thus recreate the intra-articular joint homeostasis. Recently, a novel viscosupplement based on amidated carboxymethylcellulose has been developed by blending the soluble polymer (CMCAp) with its crosslinked derivative (CMCAg) in appropriate proportions and concentrations in order to ensure an optimal combination of flow behavior and viscoelastic properties. The present work is concerned with the rheological monitoring of the crosslinking reaction performed at 25 °C by starting from aqueous CMCAp solutions in order to describe the time evolution of the linear viscoelastic moduli occurring along the whole gelation process and to individuate how the polymer concentration affects the mechanical response at the sol-gel transition and the fractal dimension of the incipient polymeric network.

This paper focusses on the mathematical modeling of the ascorbic acid (antioxidant) release from a pectin edible film (packaging) to an agar hydrogel (food). The proposed model considers the viscoelastic properties of the polymeric film, the solid ascorbic acid dissolution inside the film, its degradation and diffusion in both the film and the hydrogel. By relying on the independent determination of all its parameters, the model proved to predict the ascorbic acid transport inside the agar hydrogel properly. Thus, it may be considered a powerful theoretical tool for the design of polymeric films (packaging) aimed at releasing antioxidant agents inside food. Fil: Chiarappa, Gianlucca. Università degli Studi di Trieste; Italia Fil: De'nobili, Maria Dolores. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; Argentina Fil: Rojas, Ana Maria Luisa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; Argentina Fil: Abrami, Michela. Università degli Studi di Trieste; Italia Fil: Lapasin, Romano. Università degli Studi di Trieste; Italia Fil: Grassi, Federico Guillermo. Università degli Studi di Trieste; Italia Fil: Ferreira, Jose. University Of Coimbra. Centre For Mathematics; Portugal Fil: Gudiño, Elias. Universidade Federal do Paraná; Brasil Fil: de Oliveira, Paula. University Of Coimbra. Centre For Mathematics; Portugal Fil: Grassi, Mario. Università degli Studi di Trieste; Italia

A typical example of viscoelastic matrices is represented by polymeric particles devoted to the controlled release of active agents (drugs) that swell when put in contact with an external solvent, typically a physiological medium. Although, in general, physiological fluids can be considered Newtonian, this is not always the case, let us consider, for example, the mucus present in different organs such lungs when affected by chronic obstructive disease (bacterial infections and cystic fibrosis, for instance). Swelling allows the release of the embedded drug due to the enlargement of the meshes of the polymeric network. The demand for more and more sophisticated drug delivery systems requires to theoretically study in high detail the mass transport phenomena involved in the swelling and release processes. The present study concerns with the mathematical modelling of both transport processes in the case of a viscoelastic matrix swollen by a viscoelastic fluid. While matrix viscoelasticity is accounted for by the generalized Maxwell model, a mean relaxation time accounts for fluid viscoelasticity. The model assumes that solvent uptake gives origin to an internal stress, due the polymeric network reaction to enlargement, able to affect solvent transport and thus, drug release. Despite the complexity connected to the theoretical description of stress and deformation in the swelling matrix, it is generally assumed that the stress state can be approximated by a scalar that can be viewed as an osmotically induced viscoelastic swelling pressure related to the trace of the stress tensor. At the same time, assuming incompressible materials and vanishing deformation gradient inside the matrix, deformation can be simply represented by a scalar quantity (the radial deformation in the case of spheres). Model simulations indicate that the higher the swelling solvent relaxation time, the lower the effect of matrix viscoelastic properties on mass transport phenomena

Several natural and synthetic polysaccharides are able to form, under appropriate conditions, supramolecular structures, typically physical hydrogels, and, together with their biocompatibility, this explains their wide use in food, pharmaceutical and biomedical sectors. In the case of high methoxyl pectins (HMP) the gel formation is promoted by the presence of cosolutes (sugars or polyols) and low pH. The present investigation mainly regards the structuring kinetics of aqueous HMP solutions at add pH (3.1) with the same pectin concentration (0.2% w/w) and different sucrose concentrations (from 56 to 65% w/w). Preliminary viscosity tests were performed to individuate the threshold of the sol region. A sequence of consecutive frequency sweeps was applied to each sample immediately after its preparation. The time evolution of the linear viscoelastic behavior is described by the sigmoidal profiles of both moduli at each applied frequency and more thoroughly defined through the change of the mechanical spectrum, i.e. the variation of the parameters of the generalized Maxwell model or the Friedrich-Braun model which are both suitable to provide a satisfactory data fitting. In particular, the equilibrium modulus G(e) offers a significant description of the gelation kinetics and its sucrose dependence.

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field.

It is widely accepted that the pathological state of cells is characterized by a modification of mechanical properties, affecting cellular shape and viscoelasticity as well as adhesion behaviour and motility. Thus, assessing these parameters could represent an interesting tool to monitor disease development and progression, but also the effects of drug treatments. Since biomechanical properties of cells are strongly related to cytoskeletal architecture, in this work we extensively studied the effects of selective impairments of actin microfilaments and microtubules on HeLa cells through force-deformation curves and stress relaxation tests with atomic force microscopy. Confocal microscopy was also used to display the effects of the used drugs on the cytoskeletal structure. In synergy with the aforementioned methods, stress relaxation data were used to assess the storage and loss moduli, as a complementary way to describe the influence of cytoskeletal components on cellular viscoelasticity. Our results indicate that F-actin and microtubules play a complementary role in the cell stiffness and viscoelasticity, and both are fundamental for the adhesion properties. Our data support also the application of biomechanics as a tool to study diseases and their treatments.

To evaluate the rheological properties of mixtures of different commercially available ophthalmic viscosurgical devices (OVDs) containing sodium hyaluronate and chondroitin sulfate. SETTING: Eye Clinic, University of Trieste, Trieste, Italy. DESIGN: Laboratory study. METHODS: Blends were obtained combining a superviscous cohesive OVD (Healon GV [sodium hyaluronate 1%]) and a medium-viscosity dispersive OVD (Viscoat [sodium hyaluronate 3.0%-chondroitin sulfate 4.0%]). The 2 substances were combined in different ratios, and the rheological characteristics were analyzed to find the optimum proportion. A new viscous dispersive OVD, Discovisc (hyaluronic acid 1.6%-chondroitin sulfate 4.0%) was evaluated for comparison. The storage modulus, loss modulus, crossover point, complex viscosity, shear viscosity, and pseudoplasticity were studied. RESULTS: The rheological properties of the mixed solution (1:1 and 3:1) showed intermediate characteristics in comparison with the 2 original substances, characterized by a viscosity comparable to that of the superviscous cohesive OVD, but at a higher shear rate (similar to the medium-viscosity dispersive OVD). The new viscous dispersive OVD performed similarly to the medium-viscosity dispersive OVD at low shear rates but was comparable to the superviscous cohesive OVD at high shear rates. CONCLUSIONS: The mixture of dispersive and cohesive rheological properties in a single OVD might be an advantage during cataract surgery. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Debris flows are rapid gravity-induced flows of high-concentration granular-liquid mixtures, consisting of clay, silt, sand and boulders with a variable quantity of water. Due their high speed and energy, they represent a severe hazard in mountain regions. In this study, we investigate the properties and the dynamic of a debris flow occurred on 29th August 2003 in Valcanale valley (Friuli Venezia Giulia, Italy). Among the many watersheds affected by debris flow during the catastrophic alluvial event, we have chosen a dolomitic one, called “Solari” stream. Grain size, mineralogy and rheological behavior were characterized through laboratory analysis; later two-dimensional simulations, using the Flo-2D software, were performed on a 5 × 5 m grid obtained by the extrapolation of elevation values of the Regional Technical Map (CTRN), surveyed in 2003, in order to replicate the event, and on a 5 × 5 m grid obtained by the resampling of a LiDAR DTM, surveyed in 2008, to test the efficiency of the mitigation works. This work points out the safety of the infrastructures downstream, protected by an adequate deposition basin. At the same time, it underlines some issues during the rheological analysis and the overestimation of the depositional extent of the debris flow, when the laboratory data were used to run the simulations.

Both Laponite and scleroglucan can find several applications in various fields (from industrial to biomedical one) in virtue of their peculiar features and rheological properties displayed in aqueous phases. Structural states of Laponite dispersions strongly depend on concentration and ionic strength. When attractive and repulsive interparticle interactions are so effective that they lead to arrested states (attractive gel or repulsive glass), the rheological behavior of the dispersion undergoes a sharp transition, from quasi-Newtonian to markedly shear thinning and viscoelastic. Conversely, scleroglucan solutions gradually change to weak gels with increasing polymer concentration. The present work is concerned with aqueous Laponite-scleroglucan mixed systems, obtained according to different preparation modes, and is aimed at examining how much the content and proportion of both components affect the viscoelastic and flow properties of the mixed system.

Heart failure is a morbid disorder characterized by progressive cardiomyocyte (CM) dysfunction and death. Interest in cell-based therapies is growing, but sustainability of injected CMs remains a challenge. To mitigate this, we developed an injectable biomimetic Reverse Thermal Gel (RTG) specifically engineered to support long-term CM survival. This RTG biopolymer provided a solution-based delivery vehicle of CMs, which transitioned to a gel-based matrix shortly after reaching body temperature. In this study we tested the suitability of this biopolymer to sustain CM viability. The RTG was biomolecule-functionalized with poly-l-lysine or laminin. Neonatal rat ventricular myocytes (NRVM) and adult rat ventricular myocytes (ARVM) were cultured in plain-RTG and biomolecule-functionalized-RTG both under 3-dimensional (3D) conditions. Traditional 2D biomolecule-coated dishes were used as controls. We found that the RTG-lysine stimulated NRVM to spread and form heart-like functional syncytia. Regarding cell contraction, in both RTG and RTG-lysine, beating cells were recorded after 21 days. Additionally, more than 50% (p value < 0.05; n = 5) viable ARVMs, characterized by a well-defined cardiac phenotype represented by sarcomeric cross-striations, were found in the RTG-laminin after 8 days. These results exhibit the tremendous potential of a minimally invasive CM transplantation through our designed RTG-cell therapy platform.

Several biopolymers are widely employed in food, pharmaceutical and biomedical sectors by virtue of their ability to generate supramolecular structures, typically physical hydrogels. In the case of high methoxyl pectins (HMP) the gel formation is promoted by the presence of cosolutes (sugars or polyols) and low pH. The present investigation regards the structuring kinetics of aqueous HMP solutions having different polymer concentration and equal sucrose content at 20°C. A sequence of consecutive frequency sweep was applied to each sample immediately after its preparation. The time evolution of the linear viscoelastic behavior is described by the sigmoidal profiles of both moduli at each applied frequency and more thoroughly defined through the change of the mechanical spectrum, i.e. the variation of the parameters of the generalized Maxwell model or the Friedrich-Braun model which are both suitable to provide a satisfactory data fitting.

Starches were isolated from five improved rice varieties developed by West African Rice Development Agency (WARDA) namely FARO 32, FARO 51, FARO 52, FARO 54 and NERICA. Starch yield and amylose content varied between 73.77–70.02% and 22.88–24.48% respectively. Starches were polyhedral in appearances and within the size range 1.5–6.1 μm. The X-ray diffraction patterns of the starches show a peak centered on 2θ = 15.1°, a doublet on 17.1° and 18.1°, and another single peak at 23.12°. However, NERICA shows no doublet but a single peak at 2θ = 17.1° with a small shoulder. The peak viscosity of the starches ranged between 147.48 and 209.17 RVA corresponding to FARO 52 and NERICA respectively. A neat distinction is observed between the marked shear thinning of FARO 52 and the apparently plastic behavior of the other samples. Important differences appear in the low shear region where the viscosity increases in the following order: FARO 52

Microencapsulation is a powerful technique commonly used for the protection of a wide range of biomolecules (small molecules and protein) and cells of bacterial, yeast and animal origin. In this work, solutions of mixed biopolymers are investigated as excipients for the formulation of a model system. The influence of the different components is studied from the viscoelastic behaviour of the starting solutions to the thermal characterisation of the gel beads therefrom produced. Rheological characterisation displays an almost regular trend for the several combination of solutes and for the frequency dependence, but some peculiarities emerge when both the model protein lysozyme and the cosolvent ethanol are present in the mixture; for the latter system a delayed melting behaviour of water appears in the gel beads. Changes in the temperature dependence of water evaporation from the beads are taken as an evidence of the rate of release from the beads.

Two methyl end-capped oligo(ethylene glycol) esters (1a,b) of benzofulvene derivative BF1 were synthesized and induced to polymerize spontaneously by solvent removal to give poly-1a,b showing both NMR and absorption/emission spectra very similar to those of poly-BF1. Poly-1a,b showed relatively high molecular weight and the tendency to depolymerize to a different degree as a function of the temperature in the presence of solvents, while they exhibited appreciable stability in the absence of solvent. Poly-1b, bearing a longer oligo(ethylene glycol) side chain, featured an amphiphilic character and interacted with a number of organic solvents to produce transparent gel aggregates, and with water to give a quite compact physical gel. Rheological studies performed on the hydrogel suggested strong gel characteristics and the combination of rheology and NMR transverse relaxation measurements allowed the pore size distribution in the hydrogel to be defined. Finally, biological studies performed with poly-1b solutions showed neither cytotoxicity nor cell viability impairment suggesting potential biocompatibility features for this polymer. In conclusion, poly-1b can be considered a promising polymer for the preparation of hydrogels potentially useful in a range of biological and biotechnological applications such as drug delivery, molecular recognition, biosensing, protein and DNA separation, micro- and nanofluidics, as well as tissue engineering.

Coronary restenosis consists of the partial/total re-occlusion of the artery lumen following percutaneous transluminal angioplasty (PTCA). In order to match this pathology, PTCA is followed by the implantation of rigid scaffolds (stent or coated stent) aimed to contrast the most important mechanical (coronary wall elastic recoil and late remodelling) and biological (smooth muscle cells iper-proliferation) factors leading to restenosis. In the light of the clinical problems recently arisen about the use of traditional coated stents, this paper proposes a theoretical study to comprehend the release kinetics of novel anti-proliferative drugs, i.e. nucleic acid based drugs (NABD), complexed with the proper delivery agent (DA). The release of NABD-DA is supposed to occur from a double gel layer adhering to coronary wall and embedding the stent. The proposed mathematical model assumes that diffusion, convection and cellular internalisation/metabolism are the leading mechanisms ruling drug spreading in the coronary wall. In addition, stent void fraction, positioning (totally embedded or totally out of the coronary wall) and continuous or discontinuous character of the gel layer are other three important model parameters. In order to generalise the results, stent geometry is idealised as a series of not connected, equally spaced, rings positioned in the stented zone. In correspondence of stent strut, drug transport cannot occur. The most important outcomes of this study are that, in the usual void fraction range (0.7-0.9), stent presence does not sensibly affect NABD-DA release kinetics. In addition, whereas stent positioning in the continuous gel configuration (totally embedded or totally out of coronary wall) is not very important, in the discontinuous case, it becomes relevant. Finally, this study evidences that a proper mixture of NABD complexed with different (in dimensions and kind) DA can ensure an almost constant NABD coronary concentration for several months, as requested by clinical observations.

Pectin (P) and pectin–alginate (PAL) edible films, developed for antioxidant preservation, were placed on agar cylinders, mimicking food materials, in order to understand the release of l-(+)-ascorbic acid (AA) from the films. To improve the release properties of polymeric systems, it is crucial to describe and understand the macro- and microscopic properties of the matrices. Rheological studies performed within linear and non linear frames permitted to select, among different polymer concentrations (0.50–2.00% w/w), a 2.00% w/w agar gel as food model as this system shows the higher pure elastic contribution. Rheological and Low Field NMR (LFNMR) tests performed on 0.50–2.00% w/w agar gels as well as on P- and PAL-films after exposure (up to 6 h) to 2.00%-agar gels, showed that in spite of the higher glycerol (plasticizer) content, P-network is characterized by more numerous calcium-junction zones than PAL-matrix. The determined average network mesh size (ξ¯) for both of P- and PAL-films did not significantly change during 6 h of contact with 2.00%-agar gel. However, due to a higher swelling degree, PAL-film leads to higher ξ¯ value and water mobility inside the polymeric network. These results are of paramount importance as “ξ¯” is the main parameter affecting the release kinetics of AA from film networks to agar gels and also the diffusion of AA into the agar gel or food. Fil: De'nobili, Maria Dolores. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rojas, Ana Maria Luisa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Abrami, Michela. Università degli Studi di Trieste; Italia Fil: Lapasin, Romano. Università degli Studi di Trieste; Italia Fil: Grassi, Mario. Università degli Studi di Trieste; Italia

Viscosupplementation is an intra-articular symptomatic treatment of mild osteoarthritis. The treatment involves the injection of high-molecular-weight hyaluronan (HA), and especially of cross-linked HA to restore the lubricating and cushioning properties of the synovial fluid. This work involves the development of a novel viscosupplementation fluid based on amidated carboxymethylcellulose and obtained by blending the soluble polymer with its crosslinked derivative. Rheological analyses carried out under both oscillatory and continuous shear provided a rationale to assess the viscosupplement formulation and the production process. The hydrogel fraction content and the total polymer concentration can be properly selected in order to ensure an optimal combination of flowability and viscoelastic properties.

Rheological and erosion studies regarding a liposome-containing polymeric blend that is propaedeutic to its use in paving techniques in tubular organs, such as blood vessels, are reported. Attention is focused on an aqueous polymeric blend composed of Pluronic (PF127) and alginate (Protanal LF 10/60) because both polymers, when dissolved in water at a sufficiently high concentration, are subjected to different structural mechanisms, which are driven by temperature increase and addition of bivalent cations, respectively, and both result in marked viscoelastic and plastic properties. After proving the compatibility between PF127 and alginate, we show that the structural transition temperature of the blend, T ST , can be properly modulated. In particular, we found that T ST for an aqueous solution of pure Pluronic 20% w/w is about 21 °C and that even slight reductions in polymer concentration result in considerable T ST decrease. The addition of salts or alginate (provided as Na-alginate) provokes a substantial decrease of T ST and thus the alginate concentration in the blend should not exceed 1% w/w. In addition, liposomes slow down the structural transition but do not substantially affect the rheological properties of the system in the final state at higher temperatures, thus showing that they can be added to the polymeric blend without significant effects. Finally, erosion tests show that after contact with a source of bivalent cations, the polymeric blend containing PF127 and alginate shows an erosion resistance neatly improved with respect to the simple structured Pluronic system having the same polymer concentration. As a whole, all these results constitute the basis for future potential applications of the considered polymeric blend in tubular organs such as blood vessels.

A cogrinding process represents a possible strategy to improve the bioavailability of poorly water-soluble drugs because it allows the formation of composite materials (carrier plus drug) where the drug appears in the form of nanocrystals or in an amorphous phase which competes higher water solubility. Because of the fact that many drugs are thermolabile, an accurate knowledge of thermal conditions experienced by a drug during cogrinding is of paramount importance. Accordingly, this paper is focused on the thermal analysis of a vibrational mill by means of a mathematical model representing the mill as a sum of parts where temperature is spatially uniform but changing with time. The only exception is given by the mill bowl where, because of the low heat conductivity and high thickness of its wall, a two-dimensional heat conduction problem is solved. The comparison between the model best fitting and the experimental evidences confirms the reliability of the hypotheses on which the model was built.

Here we focus the attention on the physical characteristics of a highly biocompatible hydrogel made up of crosslinked alginate and Pluronic F127 (PF127). This is a composite polymeric blend we propose for artery endoluminal delivery of an emerging class of molecules named nucleic acid based drugs (NABDs). The physical characterization of our composite gel, i.e. mesh size distribution and PF127-alginate mutual organization after crosslinking, can significantly determine the NABDs release kinetics. Thus, to explore these aspects, different technical approaches, i.e. rheology, low/high field NMR and TEM, were used. While rheology provided information at the macroscopic and nano-level, the other three approaches gave details at the nano-level. We observe that Pluronic micelles, organizing in cubic ordered domains, generate, upon alginate crosslinking, the formation of meshes (≈150 nm) larger than those occurring in a Pluronic-free alginate network (≈25 nm). Nevertheless, smaller alginate meshes are still on and can just host un-structured Pluronic micelles and water. Accordingly, the gel structure is quite inhomogeneous, where big meshes (filled by crystalline Pluronic) co-exist with smaller meshes (hosting water and un-structured PF127 micelles). While big meshes offer a considerable hindering action on a diffusing solute, smaller ones represent a sort of free space where solute diffusion is faster. The presence of big and small meshes indicates that drug release may follow a double kinetics characterized by a fast and slow release. Notably, this behavior is considered appropriate for endoluminal drug release to the arterial wall. © The Royal Society of Chemistry 2014.

This paper focuses on the micro- and nano-topological organization of a hydrogel, constituted by a mixture of bacterial cellulose and acrylic acid, and intended for biomedical applications. The presence of acrylic acid promotes the formation of two interpenetrated continuous phases: the primary "pores phase" (PP) containing only water and the secondary "polymeric network phase" (PNP) constituted by the polymeric network swollen by the water. Low field Nuclear Magnetic Resonance (LF NMR), rheology, Scanning Electron Microscopy (SEM) and release tests were used to determine the characteristics of the two phases. In particular, we found that this system is a strong hydrogel constituted by 81% (v/v) of PP phase the remaining part being occupied by the PNP phase. Pores diameters span in the range 10-100 μm, the majority of them (85%) falling in the range 30-90 μm. The high PP phase tortuosity indicates that big pores are not directly connected to each other, but their connection is realized by a series of interconnected small pores that rend the drug path tortuous. The PNP is characterized by a polymer volume fraction around 0.73 while mesh size is around 3 nm. The theoretical interpretation of the experimental data coming from the techniques panel adopted, yielded to the micro- and nano-organization of our hydrogel. © 2014 Elsevier B.V. All rights reserved.

Purpose: to design, assemble and test a prototype of a novel production plant, suitable for producing microparticles (MPs) by processing highly viscous feed solutions (FSs). Methods: the prototype has been built using a commercial air compressor, a piston pump, an airless spray-gun, a customized air-treatment section, a timer, a rotating base, and a filtration section. Preliminary prototype parameter setting was carried out to individuate the best performing nozzle’s dimension, the nebulization timing, and the CaCl2 concentration in the gelation fluid. In addition, prototype throughput (1 L to 5 L) and the range of practicable feed solution (FS) viscosities were assayed. A set of four batches was prepared in order to characterize the MPs, in terms of mean particle size and distribution, flow properties, swelling, encapsulation efficiency and release. Results: according to a qualitative scoring, the large nozzle was suitable to nebulize FSs at a higher alginate concentration. Conversely, the small nozzle performed better in the processing of FSs with an alginate concentration up to 2% w/v. Only at the highest degree of viscosity, corresponding to 5% w/v of alginate, the FS processing was not technically possible. Among the CaCl2 concentrations considered, 15% w/v was recognized as the most versatile. The prototype appears to be convenient and suitable to grant a high yield starting from 2 L of FS. The flow behavior of the FSs assayed can be satisfactorily described with the Carreau-Yasuda equation and the throughput begins to slightly decrease for FSs at alginate concentrations exceeding 3% w/v. MP morphology was irregular with crumpled shape. The angle of repose indicates a good flowability and the release studies showed gastro-resistance and potential prolonged release applications. Conclusions: the novel prototype of production plant is suitable to process large amounts (2 L or more) of FSs, characterized by a high viscosity, to produce MPs suitable for bioactive principle delivery.

On August 29th 2003 many debris flows were activated along different streams of the Fella river basin (North–East Italy). After that huge event a program of debris flow risk analysis was started and through the use of FLO-2D software, a new outline of the hazardous areas was obtained. In the last years, part of a PhD research project was addressed to define a quick field and laboratory survey methodology suitable to obtain reliable rheological parameters and to reproduce debris flow scenarios in the absence of back analysis. An example of the methodology is presented, including grain-size and rheological analysis on samples of a watershed located in left side of the Fella river, the reconstruction of its DTM starting from detailed laser scanner data (Civil Defense of Friuli Venezia Giulia Region) and the updating of the morphometric parameters in virtue of the more detailed data. For the present research, a comparison between previous simulated scenarios and those obtained through the introduction of new basic data was provided. In particular, the simulations based on the parameters collected after the 2003 event on the DTM of 2003 were used as back analysis, whereas new simulations were performed using the rheological parameters derived from samplings and laboratory analyses realized during 2013 on the DTMs of 2008, in order to create future possible flooding scenarios on the actual morphology and to test the effectiveness of the mitigation measures, built up after the 2003 event.

Microemulsions are profitably employed in the pharmaceutical field to prepare drug delivery systems release for guest drugs sparingly soluble in water. In particular, they can be used for topical and transdermal administration in place of ointments or creams, on condition that their rheological properties are properly modulated. The present work concerns the analysis of the rheological effects produced by the addition of different amounts of Carbopol 940, a polymer widely used for topical applications, to an O/W microemulsion containing a lipophilic phase (Labrafac Hydro, 21 wt%) and stabilized by the surfactant (Cremophor RH40)/co-surfactant (Transcutol) couple. The contribution of the disperse phase is evaluated by comparing the linear and nonlinear properties of the Carbopol/microemulsion system (CM) with those of the corresponding aqueous Carbopol systems with co-surfactant (CWT) and without co-surfactant (CW). Four polymer concentrations (0.25%, 0.5%, 1%, and 2%) are taken into consideration. The linear viscoelastic properties of the microemulsions essentially mirror those of the corresponding aqueous Carbopol systems when the polymer concentration is sufficiently high (1–2%). In these conditions the oil phase is reasonably hosted within the meshes of the three-dimensional polymeric gel network and gives only a slight contribution to the connectivity of the whole system. Similar considerations can be drawn from the flow behavior of the systems examined in the low shear region.

Reliable techniques can be easily used to determine the crosslink density and the Flory interaction parameter of polymeric gels, on condition that monolithic matrices of the crosslinked polymer are available, but they cannot be profitably applied to powdered forms. In the present work we propose an experimental procedure which is particularly suitable to determine the above mentioned parameters in the case of polymeric gel particles. The technique is based on polymer swelling experiments performed in the presence of vapour and liquid external phases, and was applied to four different commercial types of sodium starch glycolate. Such a crosslinked polymer is normally supplied in a powdered form and commonly used in the pharmaceutical field as disintegrant in tablet formulation. For each polymer, the crosslink density ρx and the Flory interaction parameter χ were calculated from the experimental swelling data by solving the relevant equilibrium equations deriving from the Flory theory for gel/liquid and gel/vapor equilibrium conditions. The crosslink density values were then used to estimate the mesh size of the polymeric networks. Such a parameter is of great interest in the pharmaceutical field since it can play an important role in the performance of drug release systems based on polymeric gel matrices or minimatrices.

The effects of concentration of polyacrylic acid as a dispersant on rheological properties of aqueous alumina suspensions have been investigated under steady and oscillatory shear conditions. At solid volume fractions between 0.45 and 0.6, a high degree of particle stabilization is achieved when 0.2 wt% of polyacrylic acid is added. At lower dispersant concentrations, suspensions exhibit pronounced irreversible thixotropic behaviour, whereas at higher dispersant concentrations, time dependent effects on the flow properties are not detectable. When the saturation adsorption limit of the polyelectrolyte on Al2O3 is reached, further addition of the dispersant appreciably changes the flow behaviour, as well as the viscoelastic response of investigated suspensions. The data under steady shear are described by application of the generalized Casson model, and for the analysis of viscoelastic data the generalized Maxwell model is used.

The influence of varied polyelectrolyte concentrations in alumina suspensions with and without the addition of a latex binder has been studied using rheological measurements. Two types of latex binders (one anionic and another one nonionic) and a polyacrylic dispersant were used, and these systems have earlier been successfully used for tape casting of alumina. The stability of the suspensions was characterised using continuous shear measurements for viscosity data and oscillatory procedures for viscoelastic properties. Excess polyelectrolyte dispersant, even with a low molecular weight of about 5000, leads to increased viscosity and elasticity in highly loaded suspensions, volume fraction 0·55. The systems, however, are stable as no thixotropy effects were observed. The mechanism causing this phenomenon was found to be a combination of three mechanisms; (i) increased rigidity from the additional, charged particles which the polyelectrolyte at excess addition can be considered as, (ii) decreased electrostatic repulsion as a result of the increased ionic strength from the counterions of the polyelectrolyte, and (iii) increased viscosity of the liquid phase from free polymer. It was found that the optimum dispersant concentration in the mixed systems with latex added was higher than in the pure alumina system. It was also found that a correct dispersant level is critical as interactions were observed both for the anionic and the nonionic latex. Adsorption of the dispersant onto the latex-particles, both the anionic and nonionic ones, results in bridging flocculation at a low dispersant level.

The influence of particle concentration on the rheological properties of aqueous alumina suspensions is investigated under steady and oscillatory shear conditions. At solid volume fractions between 0·45 and 0·6, a high degree of particle stabilization is achieved when 0·2 wt% of polyacrylic acid is added as a dispersant. With increasing particle concentration the flow behavior changes from pseudoplastic to plastic. The apparent yield stress (from the generalized Casson model) is found to be a significant quantity for characterizing changes in structural conditions of the disperse phase with increasing solids loading even though more detailed information is provided by viscoelastic properties. The analysis of viscoelastic data based on the Friedrich–Braun fractional derivative model and the generalized Maxwell model showed that transitions of particle arrangements due to electrostatic repulsion take place at Φ=0·5 and 0·55. For these critical concentrations the influence of latex binder addition on the rheological properties is examined.

The rheological behavior of titanium dioxide (rutile) suspensions has been investigated under steady shear conditions in order to study the influence of disperse phase concentration. The solid particles were dispersed in a Newtonian vehicle, made of epoxy and acrylic resins dissolved in a solvent mixture at different solid volume fractions Φ, ranging from 0.16 to 0.40 (the values do not take account of resin components). The suspensions examined exhibit a Newtonian plateau at very low shear stresses and shear thinning behavior in low and moderately high shear stress regions. At a solids volume fraction Φ higher than 0.20, the onset of shear thickening behavior is observed in the highest shear stress region. For these suspensions, time-dependent effects can be assumed negligible even at the highest particle concentration examined and the shear-dependent behavior is almost reversible as is usually found for stabilised suspensions. A satisfactory fitting of both shear-thinning and shear-thickening behavior is given for the suspensions examined by modified versions of the Krieger-Dougherty and Cross equations. Accordingly, the critical shear stresses and shear rates for the relevant conditions are defined. A thorough analysis of the whole data set clearly shows that the modified Eilers equation provides the best correlation for the concentration dependence of relative viscosity, on condition that shear stress is used as a proper reference quantity instead of shear rate.