Direct ink writing of biocompatible chitosan/non-isocyanate polyurethane/cellulose nanofiber hydrogels for wound-healing applications

State-of-the-art in natural hydrogel-based wound dressings: Design, functionalization, and fabrication approaches

Natural hydrogel-based wound dressings, synthesized from biopolymers such as chitosan, sodium alginate, and cellulose, are gaining recognition in wound care due to their ability to promote healing through biocompatibility, moisture retention, and biodegradability. These materials foster an ideal healing environment by supporting cell proliferation and tissue regeneration while providing a protective barrier against infection. For chronic or infected wounds, enhancing the therapeutic performance of these hydrogels is essential. This review critically evaluates advanced functionalization strategies, including chemical modifications to optimize hydrogel properties, the incorporation of bioactive agents like growth factors and antimicrobial compounds, and the development of stimuli-responsive hydrogels that adjust to environmental cues such as pH, temperature, and enzymatic activity. Furthermore, fabrication techniques-such as solution casting, freeze-drying, electrospinning, and 3D printing-are discussed for their potential to generate tailored dressings with specific mechanical properties and bioactive capabilities. By highlighting key innovations and challenges, this review provides a comprehensive roadmap for the design, functionalization, and fabrication of natural hydrogel-based wound dressings, identifying critical areas for future research and development.

Additive-free 3D-printed nanostructured carboxymethyl cellulose aerogels

3D printing of polysaccharide solutions is widely recognized as a highly promising method in the biomedical field for achieving complex customized shapes. One of the main challenges is in selecting conditions, in particular, the rheological properties of the system, to retain the printed shape. For the first time, the direct ink writing (DIW) is successfully applied to neat carboxymethyl cellulose (CMC) solutions without any additives or crosslinking, only by adjusting solutions' rheological properties. The influence of CMC molecular weight, degree of substitution and polymer concentration on solutions' viscoelastic properties is investigated. Extrusion velocity at various pressures and pressure calibration curves are determined to optimize printing parameters. Lightweight and nanostructured materials, aerogels, are then made from the printed structures through drying with supercritical CO2. 3D printed aerogels with high shape stability are of density (solid part) around 0.1 g/cm3 and specific surface area up to 140 m2/g, density being twice lower and surface area twice higher than those of the "bulk" (or moulded) counterparts. Customized aerogels with high specific surface area hold significant potential in biomedical applications, such as tissue engineering, wound dressings, drug delivery, etc.

Green fabrication of biodegradable films: Harnessing the cellulosic residue of oat straw

Agricultural biomass is a sustainable source for developing biodegradable film to address mounting plastic perils. This study aims to investigate the influence of CaCl2 concentration on the properties of lignocellulose-based biodegradable film produced from oat straw biomass. Lignocellulose is extracted from oat biomass, and a green technique is employed to solubilize it in ZnCl2 solution and crosslinked with varying CaCl2 concentrations (200 mM-800 mM) to make films. The films containing 800 mM CaCl2 concentration demonstrated the lowest moisture content (12.81 ± 0.81 %), water solubility (43.91 ± 0.42), water vapor permeability (4.96 ± 0.14 × 10-11 gm-1s-1Pa-1), visible light transmittance (53.27 ± 0.69 %), and moisture absorption (42.42 ± 1.32 %). The tensile strength has increased remarkably from 4.24 ± 0.76 to 17.24 ± 3.68 MPa due to increased CaCl2 concentration from 200 mM to 800 mM. They degraded up to 83 % in soil with 20 % moisture after 28 days. Overall, films made of lignocellulose from oat straw biomass films demonstrate high strength and moisture barrier capabilities, rendering them suitable for use as food packaging materials.

Synthesis and Characterization of Novel Non-Isocyanate Polyurethanes Derived from Adipic Acid: A Comprehensive Study

The increasing quest for greener and more sustainable polymeric materials has gained interest in the past few decades. Non-isocyanate polyurethanes (NIPUs) have attracted attention considering that they are produced through less toxic methods compared to the conventional polyurethanes (PUs) obtained from petroleum resources and toxic isocyanates. In this context, adipic acid, glycerol carbonate, 1,2-ethylenediamine, and 1,6-hexamethylenediamine, were used to synthesize NIPU_ethyl and NIPU_hexa, respectively. The obtained NIPUs were characterized using nuclear magnetic resonance spectroscopy (H-NMR spectra) and Fourier-transform infrared spectroscopy (FTIR) analysis, which verified the structures of the intermediate and final products. Calorimetric and dielectric studies provided direct and indirect support for the facilitated thermal stability of NIPU_ethyl and NIPU_hexa. Compared to the intermediate product, the NIPUs exhibit elevated glass transition temperatures, suggesting the formation of more rigid structures. The NIPUs were also tested in terms of swelling properties, and the results indicated that NIPU_hexa absorbs and withholds increased amounts of water for longer time periods compared to NIPU_ethyl, and their hydrolysis and enzymatic hydrolysis confirmed that NIPU_hexa is more stable in aqueous environments than NIPU_ethyl. Therefore, the successful production of adipic-acid-based NIPUs through a novel perspective of the polyaddition path is reported and complemented by the characterization of the obtained materials with several techniques.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Innovations in hydrogel-based manufacturing: A comprehensive review of direct ink writing technique for biomedical applications

Direct ink writing (DIW) stands as a pioneering additive manufacturing technique that holds transformative potential in the field of hydrogel fabrication. This innovative approach allows for the precise deposition of hydrogel inks layer by layer, creating complex three-dimensional structures with tailored shapes, sizes, and functionalities. By harnessing the versatility of hydrogels, DIW opens up possibilities for applications spanning from tissue engineering to soft robotics and wearable devices. This comprehensive review investigates DIW as applied to hydrogels and its multifaceted applications. The paper introduces a diverse range of printing techniques while providing a thorough exploration of DIW for hydrogel-based printing. The investigation aims to explain the progress made, challenges faced, and potential trajectories that lie ahead for DIW in hydrogel-based manufacturing. The fundamental principles underlying DIW are carefully examined, specifically focusing on rheological attributes and printing parameters, prompting a comprehensive survey of the wide variety of hydrogel materials. These encompass both natural and synthetic variations, all of which can be effectively harnessed for this purpose. Furthermore, the review explores the latest applications of DIW for hydrogels in biomedical areas, with a primary focus on tissue engineering, wound dressing, and drug delivery systems. The document not only consolidates the existing state of DIW within the context of hydrogel-based manufacturing but also charts potential avenues for further research and innovative breakthroughs.