Expansion properties of Alginate beads as cell carrier in the fluidized bed bioartificial liver

The homogeneous expansion behaviour of liquid-fluidized beds is exploited in various fields such as minerals engineering and biotechnology. Innovative fluidized bed bioreactor concepts have been also explored for applications as bioartificial organs, particularly the bioartificial liver (1). It has been shown that the fluidized bed bioreactor constituted of alginate beads hosting liver cells is one of the promising solution to a bioartificial liver. Compared to other solutions, fluidization of alginate beads containing the cells does not suffer from the severe limitations to mass transfer between the beads and the perfusion medium. In the present work, appropriate alginate beads were prepared by the alginate drop gelation in calcium chloride. The beads were characterized in terms of size distribution and density. Sauter mean diameter of 813 m and density of 1020 kg/m3 were obtained. The latter shows a value very close to usual perfusion fluid, which required also careful evaluation of the liquid properties. Expansion properties were evaluated for free alginate beads (i.e. without hepatic cells) using saline solutions as fluidization medium. Bed expansions have been conducted in a small-size 1-cm diameter column used for perfusion in in vitro experiments as well as in a bigger 10-cm diameter column close to human size bioreactor. Velocity-voidage plots are reported and elaborated in terms of Richardson-Zaki parameters, showing the effect of walls and the different distributor. ACKNOLEDGEMENTS The financial support of the European Union through the Project FP7-PEOPLE-2012-ITN “Training network for developing innovative bioartificial devices for treatment of kidney and liver disease” is gratefully acknowledged. REFERENCES Gautier A., Carpentier B., Dufresne M., Vu Dinh Q., Paullier P., Legallais C. Impact of alginate type and bead diameter on mass transfers and the metabolic activities of encapsulated C3A cells in bioartificial liver applications. European Cells and Materials 2011, 21:94-106

Probing membrane and interface properties in concentrated electrolyte solutions

This study deals with the membrane and interface electrical properties investigation by electrochemical impedance spectroscopy (EIS). The EIS is a powerful technique for characterizing electrical behavior of systems in which coupled electrical processes occur at different rates.A systematics tudy on the effect of solution concentration,temperature and velocity, on the electrical resistance of anion-and cation- exchange membranes (AEMs and CEMs) and their interfaces (electrical double layer and diffusion boundary layer), was carried out. At the best of our knowledge, for t he first time electrolyte concentrations up to 4 M were used for the study of membranes and interface by EIS. Moreover, Pulsed Gradient Spin Echo Nuclear Magnetic Resonance (PGSE-NMR)technique was used to measure the water self-diffusion coefficients in swelled membrane as a function of the solution concentration and temperature.These measurements gave additional important insights about the effect of the electrolyte solution and fixed charges concentration in membrane,on membrane microstructure and its transport and electrical properties. & 2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBY This study deals with the membrane and interface electrical properties investigation by electrochemical impedance spectroscopy (EIS)

Selective precipitation of calcium ion from seawater desalination reverse osmosis brine

The near zero liquid discharge (NZLD) approach, by recovering water and dissolved valuable salts, is the most attractive clean solution for the valorisation of brines from seawater desalination reverse osmosis (SWD-RO) plants. In this perspective, a key aspect is calcium removal/recovery, to avoid scaling problems in the successive advanced separation units for recovering other valuable salts. In this work sodium citrate (Na3C6H5O7), carbonate (Na2CO3) and hydrogencarbonate (NaHCO3) were tested as calcium precipitation reagents. Different pH, temperature, ionic strength and reagent molar ratio were tested to maximize the Ca2+ precipitation and minimize the Mg2+ loss. Aqueous solutions containing Ca and Mg ions with/without all major seawater electrolytes were used. The chemical basis of the precipitation processes were discussed based on the effective ion surface density (e.g. Slater rule), ion hydration and Eigen association process of the precipitate formation in the complex multicomponent brine. PhreeqC and Medusa equilibrium numerical codes were applied on some experimental data of the precipitation processes providing a good agreement between calculated and experimental values. Ca2+ removal efficiency higher than 90% coupled with an Mg2+ loss below 7% was obtained at 60 °C and controlled pH, by using NaHCO3. These results are very promising in view of designing a process for brines valorisation, thus mitigating the environmental problems related to SWD-RO brines disposal.Peer ReviewedPostprint (published version

Chemically reactive membrane crystallisation reactor for CO2–NH3 absorption and ammonium bicarbonate crystallisation: Kinetics of heterogeneous crystal growth

The feasibility of gas-liquid hollow fibre membrane contactors for the chemical absorption of carbon dioxide (CO2) into ammonia (NH3), coupled with the crystallisation of ammonium bicarbonate has been demonstrated. In this study, the mechanism of chemically facilitated heterogeneous membrane crystallisation is described, and the solution chemistry required to initiate nucleation elucidated. Induction time for nucleation was dependent on the rate of CO2 absorption, as this governed solution bicarbonate concentration. However, for low NH3 solution concentrations, a reduction in pH was observed with progressive CO2 absorption which shifted equilibria toward ammonium and carbonic acid, inhibiting both absorption and nucleation. An excess of free NH3 buffered pH suitably to balance equilibria to the onset of supersaturation, which ensured sufficient bicarbonate availability to initiate nucleation. Following induction at a supersaturation level of 1.7 (3.3 M NH3), an increase in crystal population density and crystal size was observed at progressive levels of supersaturation which contradicts the trend ordinarily observed for homogeneous nucleation in classical crystallisation technology, and demonstrates the role of the membrane as a physical substrate for heterogeneous nucleation during chemically reactive crystallisation. Both nucleation rate and crystal growth rate increased with increasing levels of supersaturation. This can be ascribed to the relatively low chemical driving force imposed by the shift in equilibrium toward ammonium which suppressed solution reactivity, together with the role of the membrane in promoting counter-current diffusion of CO2 and NH3 into the concentration boundary layer developed at the membrane wall, which permitted replenishment of reactants at the site of nucleation, and is a unique facet specific to this method of membrane facilitated crystallisation. Free ammonia concentration was shown to govern nucleation rate where a limiting NH3 concentration was identified above which crystallisation induced membrane scaling was observed. Provided the chemically reactive membrane crystallisation reactor was operated below this threshold, a consistent (size and number) and reproducible crystallised reaction product was collected downstream of the membrane, which evidenced that sustained membrane operation should be achievable with minimum reactive maintenance intervention

On the aggregation and nucleation mechanism of the monoclonal antibody anti-CD20 near liquid-liquid phase separation (LLPS)

The crystallization of Anti-CD20, a full-length monoclonal antibody, has been studied in the PEG400/Na2SO4/Water system near Liquid-Liquid Phase Separation (LLPS) conditions by both sitting-drop vapour diffusion and batch methods. In order to understand the Anti-CD20 crystallization propensity in the solvent system of different compositions, we investigated some measurable parameters, normally used to assess protein conformational and colloidal stability in solution, with the aim to understand the aggregation mechanism of this complex biomacromolecule. We propose that under crystallization conditions a minor population of specifically aggregated protein molecules are present. While this minor species hardly contributes to the measured average solution behaviour, it induces and promotes crystal formation. The existence of this minor species is the result of the LLPS occurring concomitantly under crystallization conditions

NiSe and CoSe topological nodal-line semimetals: A sustainable platform for efficient thermoplasmonics and solar-driven photothermal membrane distillation

The control of heat at the nanoscale via the excitation of localized surface plasmons in nanoparticles (NPs) irradiated with light holds great potential in several fields (cancer therapy, catalysis, desalination). To date, most thermoplasmonic applications are based on Ag and Au NPs, whose cost of raw materials inevitably limits the scalability for industrial applications requiring large amounts of photothermal NPs, as in the case of desalination plants. On the other hand, alternative nanomaterials proposed so far exhibit severe restrictions associated with the insufficient photothermal efficacy in the visible, the poor chemical stability, and the challenging scalability. Here, it is demonstrated the outstanding potential of NiSe and CoSe topological nodal-line semimetals for thermoplasmonics. The anisotropic dielectric properties of NiSe and CoSe activate additional plasmonic resonances. Specifically, NiSe and CoSe NPs support multiple localized surface plasmons in the optical range, resulting in a broadband matching with sunlight radiation spectrum. Finally, it is validated the proposed NiSe and CoSe-based thermoplasmonic platform by implementing solar-driven membrane distillation by adopting NiSe and CoSe nanofillers embedded in a polymeric membrane for seawater desalination. Remarkably, replacing Ag with NiSe and CoSe for solar membrane distillation increases the transmembrane flux by 330% and 690%, respectively. Correspondingly, costs of raw materials are also reduced by 24 and 11 times, respectively. The results pave the way for the advent of NiSe and CoSe for efficient and sustainable thermoplasmonics and related applications exploiting sunlight within the paradigm of the circular blue econom

Realizzazione di membrane polimeriche innovative per la crescita in vitro di tessuti umani

Dottorato di Ricerca in Ingegneria Chimica e dei Materiali, Ciclo XXIII, a.a. 2009-2010Università of Calabri

Reverse electrodialysis for energy recovery: material development and performance evalution

Dottorato di Ricerca in Scienze e Ingegneria dell'Ambiente delle Costruzioni e dell'Energia. Ciclo XXXSalinity Gradient Power- Reverse Electrodialysis (SGP-RED), so-called blue energy, is a promising untapped membrane based renewable and sustainable energy generation technology. Salinity gradient energy can be defined as the energy reveals during the mixing of two solution having different concentration. Creating a controlled mixing in a RED stack gives the opportunity to transfer the mixing energy directly to electricity by redox reactions. Alternate arrangement of cation exchange membranes (CEM) and anion exchange membranes (AEM) form the required compartment design for controlled mixing. When high and low concentration solutions are fed from neighboring compartments, electrochemical potential difference of the solutions drive the ions from high to low concentrations. However, only charges opposite to membrane fixed charge can diffuse through, i.e. for an ideal membrane only cations can transport through CEM. Therefore, an ionic flux can be generated inside of the stack. Understanding the fundamentals of the technology and the present challenges of SGP-RED is very important for the evaluation of the experimental study. Therefore, Chapter 1 deals with the theory behind SGP-RED, potential of current state of art and challenges on performance and commercialization. Most of the RED literature investigate RED performance by using artificial solutions that only contains NaCl. In Chapter 2, the effect of real river and seawater solutions (collected from river of Amantea, Italy) is experimentally investigated on lab-scale RED stack prototype. Different flow rates and temperature are studied to find an optimized condition. RED effluents are characterized to have a better understanding on transport mechanisms of monovalent and multivalent ions. Ion characterization results indicate multivalent ions tends to transport against their concentration gradient. Moreover, investigations on electrochemical properties concludes Mg2+ has the most severe effect on RED performance by causing an order of magnitude reduction on CEM conductivity After concluding drastic negative effect of Mg2+ on power generation in the second chapter, Chapter 3 is dedicated to investigate broad range of magnesium content in mixing brine and seawater. Magnesium is known as second most abundant cation in the natural seawater solution and concentration varies from region to region. 0.5 and 4 molal solutions from 0 to 100 % Mg2+ content are tested in RED setup. Ionic characterization of outlet solution is completed to see effect of concentration on transport of ions. It is observed that uphill transport is limited to 0 – 30% of MgCl2. Ohmic and non-ohmic resistance of the CEM and AEM characterized in the test solutions. Resistance characterization reveals that cation exchange membrane resistance is critically affected by Mg2+ concentration while resistance of AEM remains unaffected. Due to RED is a non-commercialized technology, there is no commercial ion exchange membranes designed for RED. Therefore, most of the RED studies investigates electrodialysis (ED) membranes because of the similarity. In Chapter 4, cation exchange membranes are prepared considering the needs of RED. A well-known polymer, polysulfone, is sulfonated by chlorosulfonic acid to obtain negatively charged polymer. After the characterization of the polymer, CEMs are prepared with an asymmetric porous morphology by wet phase inversion method. Phase inversion parameters, e.g. solvent type, co-solvent ratio, are studied to optimize the membrane resistance and permselectivity. Among the prepared membranes, most promising one is further characterized for different NaCl concentration to estimate the power density. The results encourage to consider wet phase inversion method as a fabrication method for CEM. Commercial cation exchange membranes are produced as dense homogeneous membranes by functionalized polymeric materials as standalone or into a support to have a mechanical stability. In Chapter 5, sulfonated polyethersulfone membranes are prepared by wet phase inversion and solvent evaporation method. In solvent evaporation method, polyethersulfone/sulfonated polyethersulfone blend ratio is optimized considering electrochemical and mechanical properties. In wet phase inversion, effect of co-solvent, evaporation time, coagulation bath composition and concentration are studied to optimize the membrane electrochemical properties. Best performing wet phase inversion membrane, solvent evaporation membrane with corresponding ion exchange capacity and a benchmark commercial membrane CMX (Neosepta, Japan) are characterized to estimate RED performance for different solution concentration. Competitive results point out the possibility of CEM production by wet phase inversion Chapter 6 is dedicated to conclude and discuss the achievements of the conducted work. In addition, some outlook for the future works was mentioned based on the deductions of the experimental workUniversità della Calabri

Studio teorico di membrane bicompatibili per applicazioni farmaceutiche

Dottorato di Ricerca in Ingegneria Chimica e dei Materiali, Ciclo XXII SSD CHIM/072008-2009To design advanced dosage forms, suitable carrier materials are used to overcome the undesirable properties of drug molecules. Hence various kinds of high-performance biomaterials are being constantly developed. From the viewpoint of the optimization of pharmacotherapy, drug release should be controlled in accordance with the therapeutic purpose and pharmacological properties of active substances. The main objective of the present thesis was to characterize the interactions between drugs and drug carriers by using combined molecular dynamics, molecular mechanics, and docking computational techniques. These simulations are likely to benefit the study of materials by increasing our understanding of their chemical and physical properties at a molecular level and by assisting us in the design of new materials and predicting their properties. Simulations are usually considerably cheaper and faster than experiments. Molecular simulations also offer a unique perspective on the molecular level processes controlling structural, physical, optical, chemical, mechanical, and transport properties. In particular the attention was put on cyclodextrinic carriers supported on membrane and molecularly imprinted polymers. Thus, structural information, such as the geometries of the cyclodextrinic complexes, and thermodynamic data, i.e. the variation of the enthalpy, were considered to draw a complete picture of the βCD-drug interactions. The results were in good agreement with the experimental data found in the measurement of stability constants. Finally the molecular dynamics on the polymeric system formed by adding on the surface of PEEK-WC the βCD-drug complex showed the release of the included drug in a water solution. The docking and molecular mechanics techniques provided also informations on the geometry and the energy of complexation of a β-cyclodextrin derivative with naringin showing that the driving force for the host-guest complexation is due to the van der Waals interaction. Moreover the molecular dynamics calculations provided details on the complexation of naringin on the PEEK-WC surface containing the β-cyclodextrin derivative. The binding affinity and selectivity of MIP towards drug template were calculated from the interaction energy between the ligand and the monomers and from docking simulations, respectively, as also the number of hydrogen bonds was determined. Our computational results shown a higher interaction energy between the drug template and monomers and justified the experimental data of selective recognition and rebinding of the template in terms of MIP performance confirming the reliability of our computational method. Moreover the diffusion coefficient of 5-FU into a PMAA matrix on the release step was determined.Thus, atomistic modelling of material structure was a tool for understanding the mechanisms of physical processes on atomic and molecular levels, gaining insights into the molecular origins of behaviour of bulk polymers.Università degli Studi della Calabri