Annarosa Gugliuzza

Competitive hydrogen-bonding interactions in modified polymer membranes: a density functional theory investigation.

The subject of this work is the density functional theory (DFT) investigation of competitive hydrogen-bonding interactions that occur in modified block poly(ether/amide) (PEBAX) membranes. Previously, an evaluation of hydrogen-bonding interactions occurring between N-ethyl-o,p-toluensulfonamide (KET) modifiers was performed to establish the role of these interactions in affinity processes when the modifier is dissolved in PEBAX matrixes. However, some issues related to polymer-polymer (host-host) and modifier-polymer (host-guest) interactions were not analyzed from a theoretical point of view in the previous analysis. Here, a comparative computational analysis of these intermolecular interactions is discussed. New insights into the role of hydrogen bonding in domino processes are provided. Calculations in solvent and in vacuum have been done, yielding indications about the change in the availability of the polar groups of the polymer, which is considered to be partially responsible for the enhanced hydrophilicity of the membranes. This study can open the way to the construction of new predictive quantum modeling approaches for designing improved modifiers, enabling the optimization of polymer membrane performance.

Influence of protein bulk properties on membrane surface coverage during immobilization

Biomolecules immobilization is a key factor for many biotechnological applications. For this purpose, the covalent immobilization of bovine serum albumin (BSA), lipase from Candida rugosa and protein G on differently functionalized regenerated cellulose membranes was investigated. Dynamic light scattering and electrophoresis measurements carried out on biomolecules in solution indicated the presence of monomers, dimers and trimers for both BSA and protein G, while large aggregates were observed for lipase. The immobilization rate and the surface coverage on functionalized regenerated cellulose membranes were studied as a function of biomolecule concentration. Results indicated that the saturation coverage of BSA and protein G was concentration independent (immobilized protein amount of 2.40±0.03mg/g and 2.65±0.07mg/g, respectively). Otherwise, a different immobilization kinetics trend was obtained for lipase, for which the immobilized amount increases as a function of time without reaching a saturation value. Atomic force microscopy (AFM) micrographs showed the formation of monolayers for both BSA and protein G on the membrane surface, while a multilayer structure is found for lipase, in agreement with the trends observed in the related immobilization kinetics. As a result, the morphology of the proteins layer on the membrane surface seems to be strictly dependent on the proteins behavior in solution. Besides, the surface coverage has been described for BSA and protein G by the pseudo second order models, the results indicating the surface reaction as the controlling step of immobilization kinetics. Finally, enzyme activity and binding capacity studies indicated the preservation of the biomolecule functional properties.

Physico-Chemical Properties and Performance of Novel PEEK-WC Membranes Contacting Human Plasma and Proteins

The aim of this work was the exploration of a potential biocompatible membrane prepared from a modified polyetheretherketone (PEEK-WC). The physico-chemical properties of PEEK-WC were characterised by Differential Scanning Calorimetry and FT-Infrared Spectroscopy. The surface affinity of this membrane to human plasma and proteins such as albumin, fibrinogen and immunoglobulins G was evaluated and compared with that of commercial membranes. The wettability of all investigated membranes was established by water contact angle measurements. PEEK-WC membranes exhibited moderate wettability and low protein adsorption, differently from other commercial membranes such as cellulose acetate membrane. A preferential adsorption of hydrophilic proteins as albumin on the membrane surfaces was observed. Human plasma adsorption on membranes followed the same trend as individual protein solutions.

Photoactive Gel for Assisted Cleaning during Olive Mill Wastewater Membrane Microfiltration

A photoactive gel has been fabricated on the surface of polyethylene membranes for enhancing the fouling resistance during olive mill wastewater treatment. Light and pH responsive materials have been introduced in the membrane surface through the build up of a layer-by-layer pattern, which is formed by photocatalytic nanoparticles and ionic polyelectrolytes. The best working conditions to contrast foulants adsorption have been explored and identified. Repulsive interfacial forces and assisted transfer of foulants to catalytic sites have been envisaged as crucial factors for contrasting the decline of the flux during microfiltration. Tests in submerged configuration have been implemented for six continuous hours under irradiation at two different pH conditions. As a result, a worthy efficiency of the photoactive gel has been reached when suitable chemical microenvironments have been generated along the shell side of the membranes. No additional chemical reagents or expensive back-flushing procedures have been necessary to further clean the membranes; rather, fast and reversible pH switches have been enough to remove residues, thereby preserving the integrity of the layer-by-layer (LBL) complex onto the membrane surface.