Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

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.

Using waste biomass to produce 3D-printed artificial biodegradable structures for coastal ecosystem restoration

The loss of ecosystem functions and services caused by rapidly declining coastal marine ecosystems, including corals and bivalve reefs and wetlands, around the world has sparked significant interest in interdisciplinary methods to restore these ecologically and socially important ecosystems. In recent years, 3D-printed artificial biodegradable structures that mimic natural life stages or habitat have emerged as a promising method for coastal marine restoration. The effectiveness of this method relies on the availability of low-cost biodegradable printing polymers and the development of 3D-printed biomimetic structures that efficiently support the growth of plant and sessile animal species without harming the surrounding ecosystem. In this context, we present the potential and pathway for utilizing low-cost biodegradable biopolymers from waste biomass as printing materials to fabricate 3D-printed biodegradable artificial structures for restoring coastal marine ecosystems. Various waste biomass sources can be used to produce inexpensive biopolymers, particularly those with the higher mechanical rigidity required for 3D-printed artificial structures intended to restore marine ecosystems. Advancements in 3D printing methods, as well as biopolymer modifications and blending to address challenges like biopolymer solubility, rheology, chemical composition, crystallinity, plasticity, and heat stability, have enabled the fabrication of robust structures. The ability of 3D-printed structures to support species colonization and protection was found to be greatly influenced by their biopolymer type, surface topography, structure design, and complexity. Considering limited studies on biodegradability and the effect of biodegradation products on marine ecosystems, we highlight the need for investigating the biodegradability of biopolymers in marine conditions as well as the ecotoxicity of the degraded products. Finally, we present the challenges, considerations, and future perspectives for designing tunable biomimetic 3D-printed artificial biodegradable structures from waste biomass biopolymers for large-scale coastal marine restoration.

A 3D-Printed Scaffold for Repairing Bone Defects

The treatment of bone defects has always posed challenges in the field of orthopedics. Scaffolds, as a vital component of bone tissue engineering, offer significant advantages in the research and treatment of clinical bone defects. This study aims to provide an overview of how 3D printing technology is applied in the production of bone repair scaffolds. Depending on the materials used, the 3D-printed scaffolds can be classified into two types: single-component scaffolds and composite scaffolds. We have conducted a comprehensive analysis of material composition, the characteristics of 3D printing, performance, advantages, disadvantages, and applications for each scaffold type. Furthermore, based on the current research status and progress, we offer suggestions for future research in this area. In conclusion, this review acts as a valuable reference for advancing the research in the field of bone repair scaffolds.

Wet-Spun Chitosan-Sodium Caseinate Fibers for Biomedicine: From Spinning Process to Physical Properties

We designed and characterized chitosan-caseinate fibers processed through wet spinning for biomedical applications such as drug delivery from knitted medical devices. Sodium caseinate was either incorporated directly into the chitosan dope or allowed to diffuse into the chitosan hydrogel from a coagulation bath containing sodium caseinate and sodium hydroxide (NaOH). The latter route, where caseinate was incorporated in the neutralization bath, produced fibers with better mechanical properties for textile applications than those formed by the chitosan-caseinate mixed collodion route. The latter processing method consists of enriching a pre-formed chitosan hydrogel with caseinate, preserving the structure of the semicrystalline hydrogel without drastically affecting interactions involved in the chitosan self-assembly. Thus, dried fibers, after coagulation in a NaOH/sodium caseinate aqueous bath, exhibited preserved ultimate mechanical properties. The crystallinity ratio of chitosan was not significantly impacted by the presence of caseinate. However, when caseinate was incorporated into the chitosan dope, chitosan-caseinate fibers exhibited lower ultimate mechanical properties, possibly due to a lower entanglement density in the amorphous phase of the chitosan matrix. A standpoint is to optimize the chitosan-caseinate composition ratio and processing route to find a good compromise between the preservation of fiber mechanical properties and appropriate fiber composition for potential application in drug release.

Enhancing Paper Packaging's Wet Strength Using the Synergy between Chitosan and Nanofibrillated Cellulose Additives

The demand for eco-friendly packaging materials has urged researchers to look for alternatives to petroleum-based polymers. In this regard, paper-based products have turned out to be a promising choice; however, their weak resistance to water has limited their application. The use of various additives to enhance paper's moisture resistance is a common practice. However, considering the growing global agenda for sustainable development, the search for new bio-based paper additives has become increasingly important. This study investigated the potential synergistic impact of the addition of nanofibrillated cellulose (NFC) and chitosan additives (CHIT) to different fiber combinations to improve paper's properties, in particular, their wet strength. The efficacy of the additive application order was examined and was found to be crucial in achieving the desired outcomes. The results showed that incorporating CHIT after NFC enhanced the paper's tensile and burst indicators, as well as the paper stretch in the dry state, by 35-70%, 35-55%, and 20-35%, respectively. In addition, the tensile index and stretch in the wet state improved 9-13 times and 2.5-5.5 times over, respectively. The air permeability decreased 2.5-12 times over. These findings demonstrate that the sequential addition of the NFC and CHIT additives yield a greater enhancement of paper's properties than using each additive separately.

Rheology in Product Development: An Insight into 3D Printing of Hydrogels and Aerogels

Rheological characterisation plays a crucial role in developing and optimising advanced materials in the form of hydrogels and aerogels, especially if 3D printing technologies are involved. Applications ranging from tissue engineering to environmental remediation require the fine-tuning of such properties. Nonetheless, their complex rheological behaviour presents unique challenges in additive manufacturing. This review outlines the vital rheological parameters that influence the printability of hydrogel and aerogel inks, emphasising the importance of viscosity, yield stress, and viscoelasticity. Furthermore, the article discusses the latest developments in rheological modifiers and printing techniques that enable precise control over material deposition and resolution in 3D printing. By understanding and manipulating the rheological properties of these materials, researchers can explore new possibilities for applications such as biomedicine or nanotechnology. An optimal 3D printing ink requires strong shear-thinning behaviour for smooth extrusion, forming continuous filaments. Favourable thixotropic properties aid viscosity recovery post-printing, and adequate yield stress and G' are crucial for structural integrity, preventing deformation or collapse in printed objects, and ensuring high-fidelity preservation of shapes. This insight into rheology provides tools for the future of material design and manufacturing in the rapidly evolving field of 3D printing of hydrogels and aerogels.

3D and 4D Bioprinting Technologies: A Game Changer for the Biomedical Sector?

Bioprinting is an innovative and emerging technology of additive manufacturing (AM) and has revolutionized the biomedical sector by printing three-dimensional (3D) cell-laden constructs in a precise and controlled manner for numerous clinical applications. This approach uses biomaterials and varying types of cells to print constructs for tissue regeneration, e.g., cardiac, bone, corneal, cartilage, neural, and skin. Furthermore, bioprinting technology helps to develop drug delivery and wound healing systems, bio-actuators, bio-robotics, and bio-sensors. More recently, the development of four-dimensional (4D) bioprinting technology and stimuli-responsive materials has transformed the biomedical sector with numerous innovations and revolutions. This issue also leads to the exponential growth of the bioprinting market, with a value over billions of dollars. The present study reviews the concepts and developments of 3D and 4D bioprinting technologies, surveys the applications of these technologies in the biomedical sector, and discusses their potential research topics for future works. It is also urged that collaborative and valiant efforts from clinicians, engineers, scientists, and regulatory bodies are needed for translating this technology into the biomedical, pharmaceutical, and healthcare systems.

Fabrication of bio-inspired anisotropic structures from biopolymers for biomedical applications: A review

The anisotropic features play indispensable roles in regulating various life activities in different organisms. Increasing efforts have been made to learn and mimic various tissues' intrinsic anisotropic structure or functionality for broad applications in different areas, especially in biomedicine and pharmacy. This paper discusses the strategies for fabricating biomaterials using biopolymers for biomedical applications with the case study analysis. Biopolymers, including different polysaccharides, proteins, and their derivates, that have been confirmed with sound biocompatibility for different biomedical applications are summarized, with a special focus on nanocellulose. Advanced analytical techniques for understanding and characterizing the biopolymer-based anisotropic structures for various biomedical applications are also summarized. Challenges still exist in precisely constructing biopolymers-based biomaterials with anisotropic structures from molecular to macroscopic levels and fitting the dynamic processes in native tissue. It is foreseeable that with the advancement of biopolymers' molecular functionalization, biopolymer building block orientation manipulation strategies, and structural characterization techniques, developing anisotropic biopolymer-based biomaterials for different biomedical applications would significantly contribute to a friendly disease-curing and healthcare experience.

Structural properties of optically clear bacterial cellulose produced by Komagataeibacter hansenii using arabitol

Bacterial cellulose (BC) exhibits beneficial properties for use in biomedical applications but is limited by its lack of tunable transparency capabilities. To overcome this deficiency, a novel method to synthesize transparent BC materials using an alternative carbon source, namely arabitol, was developed. Characterization of the BC pellicles was performed for yield, transparency, surface morphology, and molecular assembly. Transparent BC was produced using mixtures of glucose and arabitol. Zero percent arabitol pellicles exhibited 25% light transmittance, which increased with increasing arabitol concentration through to 75% light transmittance. While transparency increased, overall BC yield was maintained indicating that the altered transparency may be induced on a micro-scale rather than a macro-scale. Significant differences in fiber diameter and the presence of aromatic signatures were observed. Overall, this research outlines methods for producing BC with tunable optical transparency, while also bringing new insight to insoluble components of exopolymers produced by Komagataeibacter hansenii.

A 3D-Printed Biomaterial Scaffold Reinforced with Inorganic Fillers for Bone Tissue Engineering: In Vitro Assessment and In Vivo Animal Studies

This research aimed to substantiate the potential practicality of utilizing a matrix-like platform, a novel 3D-printed biomaterial scaffold, to enhance and guide host cells' growth for bone tissue regeneration. The 3D biomaterial scaffold was successfully printed using a 3D Bioplotter^® (EnvisionTEC, GmBH) and characterized. Osteoblast-like MG63 cells were utilized to culture the novel printed scaffold over a period of 1, 3, and 7 days. Cell adhesion and surface morphology were examined using scanning electron microscopy (SEM) and optical microscopy, while cell viability was determined using MTS assay and cell proliferation was evaluated using a Leica microsystem (Leica MZ10 F). The 3D-printed biomaterial scaffold exhibited essential biomineral trace elements that are significant for biological bone (e.g., Ca-P) and were confirmed through energy-dispersive X-ray (EDX) analysis. The microscopy analyses revealed that the osteoblast-like MG63 cells were attached to the printed scaffold surface. The viability of cultured cells on the control and printed scaffold increased over time (p < 0.05); however, on respective days (1, 3, and 7 days), the viability of cultured cells between the two groups was not significantly different (p > 0.05). The protein (human BMP-7, also known as growth factor) was successfully attached to the surface of the 3D-printed biomaterial scaffold as an initiator of osteogenesis in the site of the induced bone defect. An in vivo study was conducted to substantiate if the novel printed scaffold properties were engineered adequately to mimic the bone regeneration cascade using an induced rabbit critical-sized nasal bone defect. The novel printed scaffold provided a potential pro-regenerative platform, rich in mechanical, topographical, and biological cues to guide and activate host cells toward functional regeneration. The histological studies revealed that there was progress in new bone formation, especially at week 8 of the study, in all induced bone defects. In conclusion, the protein (human BMP-7)-embedded scaffolds showed higher regenerative bone formation potential (week 8 complete) compared to the scaffolds without protein (e.g., growth factor; BMP-7) and the control (empty defect). At 8 weeks postimplantation, protein (BMP-7) significantly promoted osteogenesis as compared to other groups. The scaffold underwent gradual degradation and replacement by new bones at 8 weeks in most defects.

Mechanical strength predictability of full factorial, Taguchi, and Box Behnken designs: Optimization of thermal settings and Cellulose Nanofibers content in PA12 for MEX AM

Optimization of reinforced nanocomposites for MEX 3D-printing remain strong industrial claims. Herein, the efficacy of three modeling methods, i.e., full factorial (FFD), Taguchi (TD), and Box-Behnken (BBD), on the performance of MEX 3D printed nanocomposites was investigated, aiming to reduce the experimental effort. Filaments of medical-grade Polyamide 12 (PA12) reinforced with Cellulose NanoFibers (CNF) were evolved. Besides the CNF loading, 3D printing settings such as Nozzle (NT) and Bed (BΤ) Temperatures were optimization goals aiming to maximize the mechanical response. Three parameters and three levels of FFD were compliant with the ASTM-D638 standard (27 runs, five repetitions). An L9 orthogonal TD and a 15 runs BBD were compiled. In FFD, wt.3%CNF, 270 °C NT, and 80 °C BΤ led to 24% higher tensile strength compared to pure PA12. TGA, RAMAN, and SEM analyses interpreted the reinforcement mechanisms. TD and BBD exhibited fair approximations, requiring 7.4% and 11.8% of the FFD experimental effort.

Scaffold Using Chitosan, Agarose, Cellulose, Dextran and Protein for Tissue Engineering-A Review

Biological macromolecules like polysaccharides/proteins/glycoproteins have been widely used in the field of tissue engineering due to their ability to mimic the extracellular matrix of tissue. In addition to this, these macromolecules are found to have higher biocompatibility and no/lesser toxicity when compared to synthetic polymers. In recent years, scaffolds made up of proteins, polysaccharides, or glycoproteins have been highly used due to their tensile strength, biodegradability, and flexibility. This review is about the fabrication methods and applications of scaffolds made using various biological macromolecules, including polysaccharides like chitosan, agarose, cellulose, and dextran and proteins like soy proteins, zein proteins, etc. Biopolymer-based nanocomposite production and its application and limitations are also discussed in this review. This review also emphasizes the importance of using natural polymers rather than synthetic ones for developing scaffolds, as natural polymers have unique properties, like high biocompatibility, biodegradability, accessibility, stability, absence of toxicity, and low cost.

Synthesis by Melt-Polymerization of a Novel Series of Bio-Based and Biodegradable Thiophene-Containing Copolyesters with Promising Gas Barrier and High Thermomechanical Properties

Volatile global oil prices, owing to the scarcity of fossil resources, have impacted the cost of producing petrochemicals. Therefore, there is a need to seek novel, renewable chemicals from biomass feedstocks that have comparable properties to petrochemicals. In this study, synthesis, thermal and mechanical properties, and degradability studies of a novel series of sustainable thiophene-based copolyesters like poly(hexylene 2,5-thiophenedicarboxylate-co-bis(2-hydroxyethoxybenzene) (PTB_xH_y) were conducted via a controlled melt polymerization method. Fourier-transform infrared (FTIR) and nuclear magnetic resonance (¹H NMR) spectroscopy techniques elucidated the degree of randomness and structural properties of copolyesters. Meanwhile, gel permeation chromatography (GPC) analysis showed a high average molecular weight in the range of 67.4-78.7 × 10³ g/mol. The glass transition temperature (T_g) was between 69.4 and 105.5 °C, and the melting point between 173.7 and 194.2 °C. The synthesized polymers outperformed poly(ethylene 2,5-thiophenedicarboxylate) (PETF) and behaved similarly to polyethylene terephthalate. The copolyesters exhibited a high tensile strength of 46.4-70.5 MPa and a toughness of more than 600%, superior to their corresponding homopolyesters. The copolyesters, which ranged from 1,4-bis(2-hydroxyethyl)benzene thiophenedicarboxylate (TBB)-enriched to hexylene thiophenedicarboxylate (THH)-enriched, offered significant control over crystallinity, thermal and mechanical properties. Enzymatic hydrolysis of synthetized polymers using porcine pancreatic lipase (PP-L) over a short period resulted in significant weight losses of 9.6, 11.4, 30.2, and 35 wt%, as observed by scanning electron microscopy (SEM), with perforations visible on all surfaces of the films. Thus, thiophene-based polyesters with cyclic aromatic structures similar to terephthalic acid (TPA) show great promise as PET mimics. At the same time, PP-L appears to be a promising biocatalyst for the degradation of bioplastic waste and its recycling via re-synthesis processes.

The diversified hydrogels for biomedical applications and their imperative roles in tissue regeneration

Repair and regeneration of tissues after injury are complex pathophysiological processes. Microbial infection, malnutrition, and an ischemic and hypoxic microenvironment in the injured area can impede the typical healing cascade. Distinguished by biomimicry of the extracellular matrix, high aqueous content, and diverse functions, hydrogels have revolutionized clinical practices in tissue regeneration owing to their outstanding hydrophilicity, biocompatibility, and biodegradability. Various hydrogels such as smart hydrogels, nanocomposite hydrogels, and acellular matrix hydrogels are widely used for applications ranging from bench-scale to an industrial scale. In this review, some emerging hydrogels in the biomedical field are briefly discussed. The protective roles of hydrogels in wound dressings and their diverse biological effects on multiple tissues such as bone, cartilage, nerve, muscle, and adipose tissue are also discussed. The vehicle functions of hydrogels for chemicals and cell payloads are detailed. Additionally, this review emphasizes the particular characteristics of hydrogel products that promote tissue repair and reconstruction such as anti-infection, inflammation regulation, and angiogenesis.

Lignocellulosic-Based Materials from Bean and Pistachio Pod Wastes for Dye-Contaminated Water Treatment: Optimization and Modeling of Indigo Carmine Sorption

In this work, biomass lignocellulosic materials extracted via chemical and physical treatments from bean and pistachio pod waste were used for the optimized elimination of Indigo Carmine (IC) from aqueous medium, using a design of experiments methodology. The physicochemical properties of the studied materials (raw and treated counterparts) used for the sorption of IC were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDX, and thermal analysis. Key variables influencing the adsorption of IC, namely the initial IC concentration, the pH of the solution, the stirring time and the mass of adsorbents, were optimized by the central composite design (CCD) with three center points, the measured response being the amount of IC adsorbed. The optimal conditions obtained from the statistical analysis for the removal of IC were as follows: maximum adsorbed amounts of IC: 1.81 mg/g, 2.05 mg/g, 3.56 mg/g; 7.42 mg/g, 8.95 mg/g, 15.35 mg/g, for raw bean pods (RBS), BST1 and BST2 (bean pods chemically treated), and for raw pistachio pods (RPS), PST1 and PST2 (pistachio pods chemically treated), respectively. The pseudo-second-order nonlinear kinetics model well described the IC adsorption kinetics for RBS, BST1 and BST2, while the Elovich model was properly fitted by RPS, PST1, and PST2 biomaterials data. The Freundlich isotherm best described the shrinkage of IC on different sorbents. The good correlation of the experimental data of the IC with respect to the Freundlich isotherm indicated a multilayer adsorption with heterogeneous adsorption sites and different energies. The interest of this work consisted in developing analytical methods for the treatment of water polluted by dyes by using biosorbents, local biological materials widely available and inexpensive. The results collected in this work highlighted the interesting structural, morphological, and physico-chemical properties of the agro-waste used in the study, which properties allowed an important fixation of the target dye in solution. The research showed that the agro-waste used in the study are possible precursors to locally manufacture adsorbents at low cost, thus allowing the efficient removal of waste and dyes in liquid effluents.

3D Printing of Cellulase-Laden Cellulose Nanofiber/Chitosan Hydrogel Composites: Towards Tissue Engineering Functional Biomaterials with Enzyme-Mediated Biodegradation

The 3D printing of a multifunctional hydrogel biomaterial with bioactivity for tissue engineering, good mechanical properties and a biodegradability mediated by free and encapsulated cellulase was proposed. Bioinks of cellulase-laden and cellulose nanofiber filled chitosan viscous suspensions were used to 3D print enzymatic biodegradable and biocompatible cellulose nanofiber (CNF) reinforced chitosan (CHI) hydrogels. The study of the kinetics of CNF enzymatic degradation was studied in situ in fibroblast cell culture. To preserve enzyme stability as well as to guarantee its sustained release, the cellulase was preliminarily encapsulated in chitosan-caseinate nanoparticles, which were further incorporated in the CNF/CHI viscous suspension before the 3D printing of the ink. The incorporation of the enzyme within the CHI/CNF hydrogel contributed to control the decrease of the CNF mechanical reinforcement in the long term while keeping the cell growth-promoting property of chitosan. The hydrolysis kinetics of cellulose in the 3D printed scaffolds showed a slow but sustained degradation of the CNFs with enzyme, with approximately 65% and 55% relative activities still obtained after 14 days of incubation for the encapsulated and free enzyme, respectively. The 3D printed composite hydrogels showed excellent cytocompatibility supporting fibroblast cell attachment, proliferation and growth. Ultimately, the concomitant cell growth and biodegradation of CNFs within the 3D printed CHI/CNF scaffolds highlights the remarkable potential of CHI/CNF composites in the design of tissue models for the development of 3D constructs with tailored in vitro/in vivo degradability for biomedical applications.

Fabrication of an Organofunctionalized Talc-like Magnesium Phyllosilicate for the Electrochemical Sensing of Lead Ions in Water Samples

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH₂), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol-gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N₂ sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH₂ material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)₆]^3-. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s^-1, indicating a fast direct electron transfer rate of [Fe(CN)₆]^3- to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb²⁺ ions on TalcNH₂/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10^-8 M (S/N = 3) and 24.84 × 10^-8 M (S/N 10), for the determination of Pb²⁺ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb²⁺ ions by the grafted NH₂ groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors.

Amino-Functionalized Laponite Clay Material as a Sensor Modifier for the Electrochemical Detection of Quercetin

In this work, an electrode modified with an amino-functionalized clay mineral was used for the electrochemical analysis and quantification of quercetin (QCT). The resulting amine laponite (LaNH₂) was used as modifier for a glassy carbon electrode (GCE). The organic-inorganic hybrid material was structurally characterized using X-ray diffraction, Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and CHN elemental analysis. The covalent grafting of the organosilane to the clay backbone was confirmed. The charge on the aminated laponite, both without and with the protonation of NH₂ groups, was evaluated via cyclic voltammetry. On the protonated amine (LaNH₃⁺)-modified GCE, the cyclic voltammograms for QCT showed two oxidation peaks and one reduction peak in the range of -0.2 V to 1.2 V in a phosphate buffer-ethanol mixture at pH 3. By using the differential pulse voltammetry (DPV), the modification showed an increase in the electrode performance and a strong pH dependence. The experimental conditions were optimized, with the results showing that the peak current intensity of the DPV increased linearly with the QCT concentration in the range from 2 × 10^-7 M to 2 × 10^-6 M, leading to a detection limit of 2.63 × 10^-8 M (S/N 3). The sensor selectivity was also evaluated in the presence of interfering species. Finally, the proposed aminated organoclay-modified electrode was successfully applied for the detection of QCT in human urine. The accuracy of the results achieved with the sensor was evaluated by comparing the results obtained using UV-visible spectrometry.

Chitosan-based high-strength supramolecular hydrogels for 3D bioprinting

The loss of tissues and organs is a major challenge for biomedicine, and the emerging 3D bioprinting technology has brought the dawn for the development of tissue engineering and regenerative medicine. Chitosan-based supramolecular hydrogels, as novel biomaterials, are considered as ideal materials for 3D bioprinting due to their unique dynamic reversibility and fantastic biological properties. Although chitosan-based supramolecular hydrogels have wonderful biological properties, the mechanical properties are still under early exploration. This paper aims to provide some inspirations for researchers to further explore. In this review, common 3D bioprinting techniques and the properties required for bioink for 3D bioprinting are firstly described. Then, several strategies to enhance the mechanical properties of chitosan hydrogels are introduced from the perspectives of both materials and supramolecular binding motifs. Finally, current challenges and future opportunities in this field are discussed. The combination of chitosan-based supramolecular hydrogels and 3D bioprinting will hold promise for developing novel biomedical implants.

Hydroxyapatite/L-Lysine Composite Coating as Glassy Carbon Electrode Modifier for the Analysis and Detection of Nile Blue A

An amperometric sensor was developed by depositing a film coating of hydroxyapatite (HA)/L-lysine (Lys) composite material on a glassy carbon electrode (GCE). It was applied for the detection of Nile blue A (NBA). Hydroxyapatite was obtained from snail shells and its structural properties before and after its combination with Lys were characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analyses. The coupling of Lys to HA was attributed to favorable interaction between negatively charged -COO^- groups of Lys and divalent ions Ca²⁺ of HA. Electrochemical investigations pointed out the improvement in sensitivity of the GCE/Lys/HA sensor towards the detection of NBA in solution. The dependence of the peak current and potential on the pH, scan rate, and NBA concentration was also investigated. Under optimal conditions, the GCE/Lys/HA sensor showed a good reproducibility, selectivity, and a NBA low detection limit of 5.07 × 10^-8 mol L^-1. The developed HA/Lys-modified electrode was successfully applied for the detection of NBA in various water samples.

Bioinspired Hydrogels as Platforms for Life-Science Applications: Challenges and Opportunities

Hydrogels, as interconnected networks (polymer mesh; physically, chemically, or dynamic crosslinked networks) incorporating a high amount of water, present structural characteristics similar to soft natural tissue. They enable the diffusion of different molecules (ions, drugs, and grow factors) and have the ability to take over the action of external factors. Their nature provides a wide variety of raw materials and inspiration for functional soft matter obtained by complex mechanisms and hierarchical self-assembly. Over the last decade, many studies focused on developing innovative and high-performance materials, with new or improved functions, by mimicking biological structures at different length scales. Hydrogels with natural or synthetic origin can be engineered as bulk materials, micro- or nanoparticles, patches, membranes, supramolecular pathways, bio-inks, etc. The specific features of hydrogels make them suitable for a wide variety of applications, including tissue engineering scaffolds (repair/regeneration), wound healing, drug delivery carriers, bio-inks, soft robotics, sensors, actuators, catalysis, food safety, and hygiene products. This review is focused on recent advances in the field of bioinspired hydrogels that can serve as platforms for life-science applications. A brief outlook on the actual trends and future directions is also presented.

Organic acid cross-linked 3D printed cellulose nanocomposite bioscaffolds with controlled porosity, mechanical strength, and biocompatibility

Herein, we fabricated chemically cross-linked polysaccharide-based three-dimensional (3D) porous scaffolds using an ink composed of nanofibrillated cellulose, carboxymethyl cellulose, and citric acid (CA), featuring strong shear thinning behavior and adequate printability. Scaffolds were produced by combining direct-ink-writing 3D printing, freeze-drying, and dehydrothermal heat-assisted cross-linking techniques. The last step induces a reaction of CA. Degree of cross-linking was controlled by varying the CA concentration (2.5–10.0 wt.%) to tune the structure, swelling, degradation, and surface properties (pores: 100-450 μm, porosity: 86%) of the scaffolds in the dry and hydrated states. Compressive strength, elastic modulus, and shape recovery of the cross-linked scaffolds increased significantly with increasing cross-linker concentration. Cross-linked scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as determined by the viability assay and live/dead staining with human osteoblast cells. The proposed method can be extended to all polysaccharide-based materials to develop cell-friendly scaffolds suitable for tissue engineering applications.

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Chemically cross-linked polysaccharide-based 3D porous scaffolds were fabricated

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Physicochemical and mechanical properties increased with cross-linker concentration

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Lower cross-linker concentration led to higher porosity and interconnected pores

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Scaffolds promoted clustered cell adhesion and showed no cytotoxic effects

Improved 3D Printing and Cell Biology Characterization of Inorganic-Filler Containing Alginate-Based Composites for Bone Regeneration: Particle Shape and Effective Surface Area Are the Dominant Factors for Printing Performance

The use of organic-inorganic 3D printed composites with enhanced properties in biomedical applications continues to increase. The present study focuses on the development of 3D printed alginate-based composites incorporating inorganic fillers with different shapes (angular and round), for bone regeneration. Reactive fillers (bioactive glass 13-93 and hydroxyapatite) and non-reactive fillers (inert soda-lime glass) were investigated. Rheological studies and the characterization of various extrusion-based parameters, including material throughput, printability, shape fidelity and filament fusion, were carried out to identify the parameters dominating the printing process. It was shown that the effective surface area of the filler particle has the highest impact on the printing behavior, while the filler reactivity presents a side aspect. Composites with angular particle morphologies showed the same high resolution during the printing process, almost independent from their reactivity, while composites with comparable amounts of round filler particles lacked stackability after printing. Further, it could be shown that a higher effective surface area of the particles can circumvent the need for a higher filler content for obtaining convincing printing results. In addition, it was proven that, by changing the particle shape, the critical filler content for the obtained adequate printability can be altered. Preliminary in vitro biocompatibility investigations were carried out with the bioactive glass containing ink. The 3D printed ink, forming an interconnected porous scaffold, was analyzed regarding its biocompatibility in direct or indirect contact with the pre-osteoblast cell line MC3T3-E1. Both kinds of cell tests showed increased viability and a high rate of proliferation, with complete coverage of the 3D scaffolds' surface already after 7 d post cell-seeding.

Pure Chitosan Biomedical Textile Fibers from Mixtures of Low- and High-Molecular Weight Bidisperse Polymer Solutions: Processing and Understanding of Microstructure-Mechanical Properties' Relationship

Natural polymers, as extracted from biomass, may exhibit large macromolecular polydispersity. We investigated the impact of low molar mass chitosan (LMW, DP_w~115) on the properties of chitosan fibers obtained by wet spinning of chitosan solutions with bimodal distributions of molar masses. The fiber crystallinity index (CrI) was assessed by synchrotron X-ray diffraction and the mechanical properties were obtained by uniaxial tensile tests. The LMW chitosan showed to slightly increase the crystallinity index in films which were initially processed from the bimodal molar mass chitosan solutions, as a result of increased molecular mobility and possible crystal nucleating effects. Nevertheless, the CrI remained almost constant or slightly decreased in stretched fibers at increasing content of LMW chitosan in the bidisperse chitosan collodion. The ultimate mechanical properties of fibers were altered by the addition of LMW chitosan as a result of a decrease of entanglement density and chain orientation in the solid state. An increase of crystallinity might not be expected from LMW chitosan with a still relatively high degree of polymerization (DPw ≥ 115). Instead, different nucleation agents-either smaller molecules or nanoparticles-should be used to improve the mechanical properties of chitosan fibers for textile applications.

Direct Ink Writing of Biocompatible Nanocellulose and Chitosan Hydrogels for Implant Mesh Matrices

Direct ink writing via single or multihead extrusion is used to synthesize layer-by-layer (LbL) meshes comprising renewable polysaccharides. The best mechanical performance (683 ± 63 MPa modulus and 2.5 ± 0.4 MPa tensile strength) is observed for 3D printed structures with full infill density, given the role of electrostatic complexation between the oppositely charged components (chitosan and cellulose nanofibrils). The LbL structures develop an unexpectedly high wet stability that undergoes gradual weight loss at neutral and slightly acidic pH. The excellent biocompatibility and noncytotoxicity toward human monocyte/macrophages and controllable shrinkage upon solvent exchange make the cellular meshes appropriate for use as biomedical implants.

Ultrasound in cellulose-based hydrogel for biomedical use: From extraction to preparation

As the most abundant natural polymer on the pl anet, cellulose has a wide range of applications in the biomedical field. Cellulose-based hydrogels further expand the applications of this class of biomaterials. However, a number of publications and technical reports are mainly about traditional preparation methods. Sonochemistry offers a simple and green route to material synthesis with the biomedical application of ultrasound. The tiny acoustic bubbles, produced by the propagating sound wave, enclose an incredible facility where matter interact among at energy as high as 13 eV to spark extraordinary chemical reactions. Ultrasonication not only improves the efficiency of cellulose extraction from raw materials, but also influences the hydrogel preparation process. The primary objective of this article is to review the literature concerning the biomedical cellulose-based hydrogel prepared via sonochemistry and application of ultrasound for hydrogel. An innovated category of recent generations of hydrogel materials prepared via ultrasound was also presented in some details.

Synthesis of High Performance Thiophene-Aromatic Polyesters from Bio-Sourced Organic Acids and Polysaccharide-Derived Diol: Characterization and Degradability Studies

In this work, the feasibility of replacing petroleum-based poly(ethylene terephthalate) (PET) with fully bio-based copolyesters derived from dimethyl 2,5-thiophenedicarboxylate (DMTD), dimethyl 2,5-dimethoxyterephthalate (DMDMT), and polysaccharide-derived 1,6-hexanediol (HDO) was investigated. A systematic study of structure-property relationship revealed that the properties of these poly(thiophene-aromatic) copolyesters (PHS(20-90)) can be tailored by varying the ratio of diester monomers in the reaction, whereby an increase in DMTD content noticeably shortened the reaction time in the transesterification step due to its higher reactivity as compared with DMDMT. The copolyesters had weight-average molar masses (Mw) between 27,500 and 38,800 g/mol, and dispersity Đ of 2.0-2.5. The different polarity and stability of heterocyclic DMTD provided an efficient mean to tailor the crystallization ability of the copolyesters, which in turn affected the thermal and mechanical performance. The glass transition temperature (Tg) could be tuned from 70-100 °C, while the tensile strength was in a range of 23-80 MPa. The obtained results confirmed that the co-monomers were successfully inserted into the copolyester chains. As compared with commercial poly(ethylene terephthalate), the copolyesters displayed not only enhanced susceptibility to hydrolysis, but also appreciable biodegradability by lipases, with weight losses of up to 16% by weight after 28 weeks of incubation.

3D Bioprinted Implants for Cartilage Repair in Intervertebral Discs and Knee Menisci

Cartilage defects pose a significant clinical challenge as they can lead to joint pain, swelling and stiffness, which reduces mobility and function thereby significantly affecting the quality of life of patients. More than 250,000 cartilage repair surgeries are performed in the United States every year. The current gold standard is the treatment of focal cartilage defects and bone damage with nonflexible metal or plastic prosthetics. However, these prosthetics are often made from hard and stiff materials that limits mobility and flexibility, and results in leaching of metal particles into the body, degeneration of adjacent soft bone tissues and possible failure of the implant with time. As a result, the patients may require revision surgeries to replace the worn implants or adjacent vertebrae. More recently, autograft - and allograft-based repair strategies have been studied, however these too are limited by donor site morbidity and the limited availability of tissues for surgery. There has been increasing interest in the past two decades in the area of cartilage tissue engineering where methods like 3D bioprinting may be implemented to generate functional constructs using a combination of cells, growth factors (GF) and biocompatible materials. 3D bioprinting allows for the modulation of mechanical properties of the developed constructs to maintain the required flexibility following implantation while also providing the stiffness needed to support body weight. In this review, we will provide a comprehensive overview of current advances in 3D bioprinting for cartilage tissue engineering for knee menisci and intervertebral disc repair. We will also discuss promising medical-grade materials and techniques that can be used for printing, and the future outlook of this emerging field.

Modelling Human Physiology on-Chip: Historical Perspectives and Future Directions

For centuries, animal experiments have contributed much to our understanding of mechanisms of human disease, but their value in predicting the effectiveness of drug treatments in the clinic has remained controversial. Animal models, including genetically modified ones and experimentally induced pathologies, often do not accurately reflect disease in humans, and therefore do not predict with sufficient certainty what will happen in humans. Organ-on-chip (OOC) technology and bioengineered tissues have emerged as promising alternatives to traditional animal testing for a wide range of applications in biological defence, drug discovery and development, and precision medicine, offering a potential alternative. Recent technological breakthroughs in stem cell and organoid biology, OOC technology, and 3D bioprinting have all contributed to a tremendous progress in our ability to design, assemble and manufacture living organ biomimetic systems that more accurately reflect the structural and functional characteristics of human tissue in vitro, and enable improved predictions of human responses to drugs and environmental stimuli. Here, we provide a historical perspective on the evolution of the field of bioengineering, focusing on the most salient milestones that enabled control of internal and external cell microenvironment. We introduce the concepts of OOCs and Microphysiological systems (MPSs), review various chip designs and microfabrication methods used to construct OOCs, focusing on blood-brain barrier as an example, and discuss existing challenges and limitations. Finally, we provide an overview on emerging strategies for 3D bioprinting of MPSs and comment on the potential role of these devices in precision medicine.

Controlled Polyelectrolyte Association of Chitosan and Carboxylated Nano-Fibrillated Cellulose by Desalting

We prepared chitosan (CHI) hydrogels reinforced with highly charged cellulose nanofibrils (CNF) by the desalting method. To this end, the screening of electrostatic interactions between CHI polycation and CNF polyanion was performed by adding NaCl at 0.4 mol/L to the chitosan acetate solution and to the cellulose nanofibrils suspension. The polyelectrolyte complexation between CHI polycation and CNF polyanion was then triggered by desalting the CHI/CNF aqueous mixture by multistep dialysis, in large excess of chitosan. Further gelation of non-complexed CHI was performed by alkaline neutralization of the polymer, yielding high reinforcement effects as probed by the viscoelastic properties of the final hydrogel. The results showed that polyelectrolyte association by desalting can be achieved with a polyanionic nanoparticle partner. Beyond obtaining hydrogel with improved mechanical performance, these composite hydrogels may serve as precursor for dried solid forms with high mechanical properties.