Low-cost luminescent scaffolds-based on thiol chitosans by microwave radiation for vertebral disc repair/theragnostic.

This study introduces a new 3D scaffold based on thiolated chitosans with luminescence by microwave radiation using cysteine (Chi_CT_Cys) and 11-mercaptoundecanoic acid (Chi_CT_MUA) for vertebral disc regeneration/theragnostic. These scaffolds were characterized by Raman, PL spectroscopy, swelling, gel-fraction, and morphologies. Cytocompatibility and mechanical behavior were evaluated. Raman showed that disulfide bonds improved the grafting degree (Chi_CT_Cys (1072 ± 136) µmol·g-1 and Chi_CT_MUA (3245 ± 105) µmol·g-1). Morphologies showed interesting characteristics. Swelling behavior showed that Chi_CT_MUA presented a slight minor swelling (2101 ± 251) % compared to Chi_CT_Cys (2589 ± 188) %. Differently, gel-fraction showed that the chemical stability of Chi_CT_Cys was worse (29 ± 4) % than Chi_CT_MUA (15 ± 3) %. PL showed a possibility to use theragnostic evaluation of points of greater compression in a vertebral disc. The mechanical behavior of Chi_CT_MUA presented better results ((70 ± 3) MPa) than Chi_CT_Cys ((37 ± 3) MPa). Cytocompatible showed that the scaffolds presented cell viability >90%. Thusly, these 3D scaffolds presented an incredible potential for tissue engineering applications.

3D sponges of chemically functionalized chitosan for potential environmental pollution remediation: biosorbents for anionic dye adsorption and 'antibiotic-free' antibacterial activity.

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.

Ecofriendly multifunctional thiolated carboxymethyl chitosan-based 3D scaffolds with luminescent properties for skin repair and theragnostic of tissue regeneration.

Luminescent biopolymers, namely carboxymethyl chitosan, have become a target of attention due to their potential for biomedical applications. In this context, biomaterials capable of improving theragnostic tissue regeneration and provide a tissue repair remain a challenge. This study introduces a new 3D scaffold based on two innovative thiolated carboxymethyl chitosan with cysteine (CMCCys) and 11-mercaptoundecanoic acid (CMCMerc) resulting in enhanced fluorescence of CMC for repair and theragnostic of tissue regeneration. Those thiolated CMCs were intensively characterized by spectroscopy techniques (FTIR, NMR), swelling degree, chemical stability (Gel-fraction, GF) and morphological analysis (SEM, microtomography, BET). In addition, the photoluminescence properties were evaluated and cytocompatibility was performed via in vitro bioassays. The results demonstrated that those scaffolds presented interconnected 3D porous (porosity > 80%), a great GF, and a high degree of thiolation (2%-11%). Furthermore, the spectroscopy analysis elucidated a significant disulfide bond formation, which guaranteed mechanical stability for applications in tissue engineering (elastic modulus, (22 ± 3) kPa and (35 ± 2) kPa, for CMCCys and CMCMerc, respectively). Additionally, the incorporation of thiol group improved the fluorescence of CMC and they presented cytocompatibility > 90%. Thus, for the first time, a multifunctional 3D CMC thiomer was produced for applications in repair and theragnostic of tissue regeneration.

Chitosan and carboxymethyl-chitosan capping ligands: Effects on the nucleation and growth of hydroxyapatite nanoparticles for producing biocomposite membranes.

Synthetic biomaterials based on calcium phosphates (CaP) have been widely studied for bone tissue reconstruction therapies, but no definitive solution that fulfills all of the required properties has been identified. Thus, this study reports the synthesis of composite membranes based on nanohydroxyapatite particles (nHA) embedded in chitosan (CHI) and O-carboxymethyl chitosan (CMC) matrices produced using a one-step co-precipitation method in water media. Biopolymers were used as capping ligands for simultaneously controlling the nucleation and growth of the nHA particles during the precipitation process and also to form the polymeric network of the biocomposites. The bionanocomposites were extensively characterized using light microscopy (LM), scanning and transmission electron microscopy (SEM/TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray micro-CT analysis (µCT), andMTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazoliumbromide) cell proliferation assays for cell cytotoxicity. The results demonstrated that the ligands used during the synthesis highly affected the composites produced, primarily due the changes in the mechanisms and kinetics of nucleation and growth of the HA particles at the nanoscale level. The SEMimages revealed that the use of carboxyl-functionalized chitosan (CMC) ligands significantly reduced the average size of theHA nanoparticles and caused the formation of a narrower size distribution (90±20nm) compared to theHAnanoparticles producedwith chitosan ligands (220±50nm). The same trend was verified by the AFM analysis,where the nHA particles were formed evenly dispersed in the polymer matrix. However, the CMC-based composites were more homogeneously distributed, which was endorsed by the images collected via X-ray micro-CT. The FTIR spectra and the XRD analysis indicated that nanosized hydroxyapatite was the predominant calcium phosphate phase produced during the co-precipitation aqueous process for both the chitosan and CMC biocomposites. These novel hybrid systems based on chitosan and chitosan-derivatives with nHA composites were non-cytotoxic to a human osteoblast-like model cell line (SAOS) according to MTT in vitro assays. Moreover, the CMC-nHA biocomposites revealed a striking improvement in the cell viability response compared to the CHI-nHA biocomposite, which was attributed to the much higher surface area caused by the refinement of the nanoparticles size. Thus, the results of this study demonstrate that these novel bionanocomposite membranes offer promising perspectives as biomaterials for potential repair and replacement of cartilage and bone tissues.