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Wound infections are the main complication when treating skin wounds. This work reports a novel antimicrobial material using green synthesized zinc oxide nanoparticles (ZnONPs) incorporated in polymeric fibers for wound healing purposes. ZnONPs are a promising antimicrobial nanomaterial with high activity against a range of microorganisms, including drug-resistant bacteria. The electrospun fibers were obtained using polyacrylic acid (PAA) and polyallylamine hydrochloride (PAH) and were loaded with ZnONPs green synthesized from Ilex paraguariensis leaves with a spherical shape and ~18 nm diameter size. The fibers were produced using the electrospinning technique and SEM images showed a uniform morphology with a diameter of ~230 nm. EDS analysis proved a consistent dispersion of Zn in the fiber mat, however, particle agglomerates with varying sizes were observed. FTIR spectra confirmed the interaction of PAA carboxylic groups with the amine of PAH molecules. Although ZnONPs presented higher antimicrobial activity against S. aureus than E. coli, resazurin viability assay revealed that the PAA/PAH/ZnONPs composite successfully inhibited both bacteria strains growth. Photomicrographs support these results where bacteria clusters were observed only in the control samples. The PAA/PAH/ZnONPs composite developed presents antimicrobial activity and mimics the extracellular matrix morphology of skin tissue, showing potential for wound healing treatments.

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Microfibrillated cellulose films have been gathering considerable attention due to their high mechanical properties and cheap cost. Additionally, it is possible to include compounds within the fibrillated structure in order to confer desirable properties. Ilex paraguariensis A. St.-Hil, yerba mate leaf extract has been reported to possess a high quantity of caffeoylquinic acids that may be beneficial for other applications instead of its conventional use as a hot beverage. Therefore, we investigate the effect of blending yerba mate extract during and after defibrillation of Eucalyptus sp. bleached kraft paper by ultrafine grinding. Blending the extract during defibrillation increased the mechanical and thermal properties, besides being able to use the whole extract. Afterwards, this material was also investigated with high content loadings of starch and glycerine. The results present that yerba mate extract increases film resistance, and the defibrillated cellulose is able to protect the bioactive compounds from the extract. Additionally, the films present antibacterial activity against two known pathogens S. aureus and E. coli, with high antioxidant activity and increased cell proliferation. This was attributed to the bioactive compounds that presented faster in vitro wound healing, suggesting that microfibrillated cellulose (MFC) films containing extract of yerba mate can be a potential alternative as wound healing bandages.

In this work, a novel dual-response hydrogel for enhanced bone repair following multiple fractures was investigated. The conventional treatment of multiple bone fracture consists on removing smaller bone fragments from the body in a surgery, followed by the fixation of the bone using screws and plates. This work proposes an alternative for this treatment via in situ UV-initiated radical polymerization of a novel IPN hydrogel composed of PAA/P(NiPAAM-co-PEGDMA) incorporated with ceramic additives. The influence of different additives on mechanical properties and sensitivity of the polymer, as well as the prepolymer mixture, were investigated in order to analyse the suitability of the composites for bone healing applications. This material exhibited an interpenetrating network, confirmed by FTIR, with ceramics particles dispersed in between the polymer network. These structures presented high strength by tensile tests, sensitivity to pH and temperature and a decrease on Tg values of NiPAAm depending on the amount of PEGDMA and ceramics added; although, the addition of ceramics to these composites did not decrease their stability drastically. Finally, cytotoxicity tests revealed variations on the toxicity, whereas the addition of TCP presented to be non-toxic and that the cell viability increased when ceramics additives were incorporated into the polymeric matrix with an increased reporter activity of NF-κB, associated with aiding fibroblast adhesion. Hence, it was possible to optimise feedstock ratios to increase the applicability of the prepolymer mixture as a potential treatment of multiple fractures.

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Although freeze-thaw mechanism for producing crosslinked hydrogels is relatively easy and simple, it lacks sufficient integrity and support leading to modifications on its three-dimensional polymeric network arrangement during water removal-drying. Therefore, a strengthening method for obtaining cryogenic spheres of polyvinyl alcohol hydrogels is purposed by dispensing it as liquid droplets into a low temperature solution followed by a modification on its freeze-thaw cycles to confer a good geometry without aggregation. Various materials were incorporated into this hydrogel structure, including poly(acrylic acid) to impart pH sensitivity; hydroxyapatite to improve biocompatibility; and ciprofloxacin as an antimicrobial agent relevant for the treatment of osteomyelitis. The overall network presented a porous structure with a fibrous-like pattern which varied in size and volume, with presence of Ca and P when hydroxyapatite is incorporated. These materials varied the crystalline melting point of the poly(vinyl alcohol) and a linear pH sensitivity function was obtained by the addition of the materials. These hydrogels were found to release ciprofloxacin within 60 min and were able to dissolve at the same time intervals. Therefore, the hydrogel synthesised in this work can be used as an immediate release drug delivery mechanism for the in situ delivery of active pharmaceutical such as ciprofloxacin for a treatment of osteomyelitis.

The effectiveness of tannic acid as antimicrobial and wound healing for burns have been shown for a century; however, uncontrolled target dosage may result in undesirable side-effects. Remarkably, tannic acid polyphenols compounds crosslinked with polymeric materials produce a strong composite containing the beneficial properties of this tannin. However, investigation of the crosslink structure and its antibacterial and regenerative properties are still unknown when using nanocellulose by mechanical defibrillation; additionally, due to the potential crosslink structure with chitosan, its structure can be complex. Therefore, this work uses bleach kraft nanocellulose in order to investigate the effect on the physical and regenerative properties when incorporated with chitosan and tannic acid. This film results in increased rigidity with a lamellar structure when incorporated with tannic acid due to its strong hydrogen bonding. The release of tannic acid varied depending on the structure it was synthesised with, whereas with chitosan it presented good release model compared to pure cellulose. In addition, exhibiting similar thermal stability as pure cellulose films with antibacterial properties tested against S. aureus and E. coli with good metabolic cellular viability while also inhibiting NF-κB activity, a characteristic of tannic acid.