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We prepared composite ultrafiltration membranes by directly electrospinning a top layer of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) onto polysulfone (PSU). The electrospun layer was cross-linked by heat curing, and the previous irradiation of the PSU support allowed creating stable composites that did not detach under crossflow operation. The physicochemical properties of the composites were measured using FTIR spectroscopy, water contact angle, surface ζ-potential, and permeation measurements. We showed that PAA−PVA electrospun layers increased membrane hydrophilicity and reduced organic fouling without affecting permeability and protein rejection performance. The antibacterial performance of the top-layer composites was investigated using Escherichia coli and Staphylococcus aureus strains and tracked counting colony forming units, SEM images of colonized specimens, and cell viability using confocal microscopy. The results showed that PAA−PVA coating resulted in clear antimicrobial performance, particularly for the bacteriumS. aureus, which we attributed to the chelating of the cations stabilizing cell envelopes. Composite membranes were compared with neat PSU membranes in 48 h cross-flow experiments. The composites showed good mechanical integrity and antimicrobial behavior under flow conditions with average reduction of 1-log for electrospun composites exposed to S. aureus over PSU. This work demonstrates that top-layer nanofiber composites can lead to ultrafiltration membranes with enhanced functionalities.

BACKGROUND: Poly(vinyl alcohol) (PVA) is a synthetic biocompatible polymer that is extensively used by the medical and pharmaceutical industries due to its FDA approval for in vivo applications. Its highly hydrophilic nature makes it an ideal wound dressing material, especially in the form of nanofibrous mats. RESULTS: In this work, electrospun PVA-based scaffolds suitable for wound management were created. Chemical cross-linking with citric acid and glyoxal was employed to enhance the supports' stability in aqueous environments, and cellulose nanocrystals were added during the electrospinning process to improve the mechanical properties of the final constructs. Varying the concentrations of the cross-linking agents (0.12-1 wt% citric acid and 0.06-0.5 wt% glyoxal), allowed the control of the rate and extend of dissolution, thereby tuning the properties of the materials to the specific wound types (e.g. acute vs chronic). There was an inverse relationship between the amount of cross-linkers used and the mats' weight loss (ranging from 2% to 18%) after 6 days immersion in water. All supports sustained the growth of human fibroblasts (>85% viability), whereas there was no biofilm formation when in contact with S. aureus for 24 hours. The presence of cellulose nanocrystals did not affect cytocompatibility but improved the mechanical properties of the non-woven fibres.CONCLUSION: Tailor-made biocompatible electrospun mats showing antimicrobial behaviour were successfully created through altering the concentration of chemical cross-linkers. This flexible approach offers the potential of matching the dressing to the wound type and offering a more targeted solution to wound management.

Poly(vinyl chloride) (PVC) ultrafiltration membranes with improved antifouling and antibiofouling properties were prepared by non-solvent induced phase inversion using a hyperbranched polyamidoamine as additive. PVC reacted into the casting solution with the commercial polyamidoamine nanomaterial Helux-3316 by means of a nucleophilic substitution reaction. The composition of neat and functionalized membranes was studied by ATR-FTIR and elemental composition. Amino groups were tracked using the fluorescent dye fluorescamine. Surface ζ-potential and water contact angles were used to measure surface charge and hydrophilicity of tested membranes. The incorporation of amino groups increased membrane hydrophilicity and surface porosity, which resulted in enhanced permeability. Functionalized membranes displayed antifouling behaviour revealed upon filtering BSA solutions and lower irreversible fouling than PVC membranes. The attachment of Helux moieties to PVC yielded membranes with antibiofouling functionality explained by the interaction of positively charged Helux moieties with the negatively charged cell envelopes. Growth reduction for cells attached to the membrane surface during filtration reached up to 1log for the gram-positive bacterium S. aureus. This investigation revealed that the incorporation of the hyperbranched nanomaterial in concentrations in the order of 1 wt% in the casting solution provides significant benefits to membrane performance, in terms of permeability and antifouling potential.