Insight into morphological, physicochemical and spectroscopic properties of β-chitin nanocrystalline structures

Aldehyde-functionalization of chitin nanocrystals via SI-ARGET ATRP of lignin-derived monomers

Chitin nanocrystals (ChNCs), prepared from a down-sizing process from chitin, have recently captured great attention to access sustainable nanomaterials. The surface modification of ChNCs is crucial to regulate the surface physicochemical properties and introduce specific functions, thus satisfying their diverse applications. In this study, aldehyde-functionalized ChNCs (ChNCs-PVMA) with enhanced hydrophobicity were developed via surface-initiated activators regenerated by electron transfer for atom transfer radical polymerization (SI-ARGET ATRP) of a lignin-derived polymerizable aldehyde monomer, vanillin methacrylate (VMA). The monomer conversion was determined by 1H NMR spectroscopy of the reaction mixture based on the change of the relative ratio of VMA and solvent signals. The prepared ChNCs-PVMA were systematically characterized by FTIR, CP/MAS 13C NMR, XPS, XRD, DSC, TGA, and TEM. The dispersibility of ChNCs and ChNCs-PVMA in water and DMF was evaluated by dynamic light scattering and visual observation, indicating good dispersion of ChNCs-PVMA in organic solvents. Furthermore, based on the available aldehyde groups, the ChNCs-PVMA was reacted with amino acids via Schiff base reaction, demonstrating a rich follow-up chemistry towards diverse functions by the reactive aldehyde groups.

Hierarchical Chitin Nanocrystal-Based 3D Printed Dual-Layer Membranes Hydrogels: A Dual Drug Delivery Nano-Platform for Periodontal Tissue Regeneration

Periodontitis, a prevalent chronic inflammatory disease caused by bacteria, poses a significant challenge to current treatments by merely slowing their progression. Herein, we propose an innovative solution in the form of hierarchical nanostructured 3D printed bilayer membranes that serve as dual-drug delivery nanoplatforms and provide scaffold function for the regeneration of periodontal tissue. Nanocomposite hydrogels were prepared by combining lipid nanoparticle-loaded grape seed extract and simvastatin, as well as chitin nanocrystals, which were then 3D printed into a bilayer membrane that possesses antimicrobial properties and multiscale porosity for periodontal tissue regeneration. The constructs exhibited excellent mechanical properties by adding chitin nanocrystals and provided a sustained release of distinct drugs over 24 days. We demonstrated that the bilayer membranes are cytocompatible and have the ability to induce bone-forming markers in human mesenchymal stem cells, while showing potent antibacterial activity against pathogens associated with periodontitis. In vivo studies further confirmed the efficacy of bilayer membranes in enhancing alveolar bone regeneration and reducing inflammation in a periodontal defect model. This approach suggests promising avenues for the development of implantable constructs that not only combat infections, but also promote the regeneration of periodontal tissue, providing valuable insights into advanced periodontitis treatment strategies.

Activity of a Recombinant Chitinase of the Atta sexdens Ant on Different Forms of Chitin and Its Fungicidal Effect against Lasiodiplodia theobromae

This study evaluates the activity of a recombinant chitinase from the leaf-cutting ant Atta sexdens (AsChtII-C4B1) against colloidal and solid α- and β-chitin substrates. 1H NMR analyses of the reaction media showed the formation of N-acetylglucosamine (GlcNAc) as the hydrolysis product. Viscometry analyses revealed a reduction in the viscosity of chitin solutions, indicating that the enzyme decreases their molecular masses. Both solid state 13C NMR and XRD analyses showed minor differences in chitin crystallinity pre- and post-reaction, indicative of partial hydrolysis under the studied conditions, resulting in the formation of GlcNAc and a reduction in molecular mass. However, the enzyme was unable to completely degrade the chitin samples, as they retained most of their solid-state structure. It was also observed that the enzyme acts progressively and with a greater activity on α-chitin than on β-chitin. AsChtII-C4B1 significantly changed the hyphae of the phytopathogenic fungus Lasiodiplodia theobromae, hindering its growth in both solid and liquid media and reducing its dry biomass by approximately 61%. The results demonstrate that AsChtII-C4B1 could be applied as an agent for the bioproduction of chitin derivatives and as a potential antifungal agent.

Multifunctional bilayer membranes composed of poly(lactic acid), beta-chitin whiskers and silver nanoparticles for wound dressing applications

Nanomaterial-based wound dressings have been extensively studied for the treatment of both minor and life-threatening tissue injuries. These wound dressings must possess several crucial characteristics, such as tissue compatibility, non-toxicity, appropriate biodegradability to facilitate wound healing, effective antibacterial activity to prevent infection, and adequate physical and mechanical strength to withstand repetitive dynamic forces that could potentially disrupt the healing process. Nevertheless, the development of nanostructured wound dressings that incorporate various functional micro- and nanomaterials in distinct architectures, each serving specific purposes, presents significant challenges. In this study, we successfully developed a novel multifunctional wound dressing based on poly(lactic acid) (PLA) fibrous membranes produced by solution-blow spinning (SBS) and electrospinning. The PLA-based membranes underwent surface modifications aimed at tailoring their properties for utilization as effective wound dressing platforms. Initially, beta-chitin whiskers were deposited onto the membrane surface through filtration, imparting hydrophilic character. Afterward, silver nanoparticles (AgNPs) were incorporated onto the beta-chitin layer using a spray deposition method, resulting in platforms with antimicrobial properties against both Staphylococcus aureus and Escherichia coli. Cytotoxicity studies demonstrated the biocompatibility of the membranes with the neonatal human dermal fibroblast (HDFn) cell line. Moreover, bilayer membranes exhibited a high surface area and porosity (> 80%), remarkable stability in aqueous media, and favorable mechanical properties, making them promising candidates for application as multifunctional wound dressings.

Antimicrobial and Photoantimicrobial Activities of Chitosan/CNPPV Nanocomposites

Multidrug-resistant bacteria represent a global health and economic burden that urgently calls for new technologies to combat bacterial antimicrobial resistance. Here, we developed novel nanocomposites (NCPs) based on chitosan that display different degrees of acetylation (DAs), and conjugated polymer cyano-substituted poly(p-phenylene vinylene) (CNPPV) as an alternative approach to inactivate Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Chitosan’s structure was confirmed through FT-Raman spectroscopy. Bactericidal and photobactericidal activities of NCPs were tested under dark and blue-light irradiation conditions, respectively. Hydrodynamic size and aqueous stability were determined by DLS, zeta potential (ZP) and time-domain NMR. TEM micrographs of NCPs were obtained, and their capacity of generating reactive oxygen species (ROS) under blue illumination was also characterized. Meaningful variations on ZP and relaxation time T2 confirmed successful physical attachment of chitosan/CNPPV. All NCPs exhibited a similar and shrunken spherical shape according to TEM. A lower DA is responsible for driving higher bactericidal performance alongside the synergistic effect from CNPPV, lower nanosized distribution profile and higher positive charged surface. ROS production was proportionally found in NCPs with and without CNPPV by decreasing the DA, leading to a remarkable photobactericidal effect under blue-light irradiation. Overall, our findings indicate that chitosan/CNPPV NCPs may constitute a valuable asset for the development of innovative strategies for inactivation and/or photoinactivation of bacteria.