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In this work, bionanocomposite membranes of hydroxyapatite nanoparticles (nHA) embedded in chitosan (CHI) or carboxymethyl-chitosan (CMC) matrices were chemically crosslinked with epichlorohydrin (ECH) for tuning their physicochemical and biological properties aiming at bone tissue regeneration. The choice of CHI or CMC biopolymer, as well as the presence of ECH crosslinker, affected the nucleation and growth processes of nHA producing average diameters varying from 93 nm to 589 nm and altered the relative stability of the membranes against degradation. In vitro analysis by MTT using SAOS and HEK 293 T cell lineages evidenced preliminary cytocompatibility for the biocomposites investigated. Moreover, in vivo analyses using the Wistar rat model demonstrated that the crosslinking enhanced bone repair processes in up to 55% and 22% compared to the control and non-crosslinked biocomposites, respectively. Chitosan and Carboxymethyl-Chitosan Biocomposites Reinforced with Nanohydroxyapatite: Towards Artificial Bone Substitutes [ABSTRACT FROM AUTHOR]

In this work, it was developed three-dimensional (3D) porous hydrogel sponges produced by the freeze-dried process using chitosan polymer functionalized by 11-mercaptoundecanoic acid (MUA). These chitosan-based sponges were used as cationic adsorbents for the removal of anionic methyl orange (MO) dye, simulating a model organic pollutant in aqueous medium. Moreover, these porous 3D constructs were also evaluated as 'antibiotic-free' antibacterial materials against gram-negative and gram-positive bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, respectively, which were used as model pathogens possibly found in contaminated hospital discharges. These 3D hydrogels were comprehensively characterized through morphological methods such as scanning electron microscopy and X-ray micro-computed tomography techniques, combined with FTIR, Raman, and UV-visible spectroscopy analyses. Additionally, the surface area, the degree of swelling, and the adsorption profiles and kinetics of these scaffolds were systematically investigated. The chemically thiolated chitosan (CHI-MUA) hydrogels were successfully produced with a supramolecular polymeric network based on hydrogen bonds, disulfide bonds, and hydrophobic interactions that resulted in higher stability in aqueous medium than hydrogels of pristine chitosan. CHI-MUA exhibited sponge-like three-dimensional structures, with highly interconnected and hierarchical pore size distribution with high porosity and surface area. These architectural aspects of the 3D sponges favoured the high adsorption capacity for MO dye (∼388 mg.g−1) in water with removal efficiency greater than 90% for MO solutions (from 20 mg.L−1–1200 mg.L−1). The adsorption data followed a pseudo-second-order kinetic model and adsorption isotherm analysis and spectroscopy studies suggested a multilayer behaviour with coexistence of adsorbent-adsorbate and adsorbate-adsorbate interactions. Additionally, the in vitro evaluation of toxicity (MTT and LIVE-DEAD® assays) of 3D-sponges revealed a non-toxic response and preliminary suitability for bio-related applications. Importantly, the 3D-sponges composed of chitosan-thiolated derivative proved high antibacterial activity, specificity against P. aeruginosa (model hazardous pathogen), equivalent to conventional antibiotic drugs, while no lethality against S. aureus (reference commensal bacteria) was observed. [ABSTRACT FROM AUTHOR]

Competing Interests: None