Study of 3D-printed chitosan scaffold features after different post-printing gelation processes

Evaluation of composition effects on the tissue-adhesive, mechanical and physical properties of physically crosslinked hydrogels based on chitosan and pullulan for wound healing applications

Tissue adhesion of hydrogels plays an important role in wound healing, which can improve the efficiency of wound treatment, stop bleeding, facilitate tissue growth and wound closure. However, most non-covalent crosslinked hydrogels have weak tissue adhesion and rheological properties. Furthermore, it remains a challenge to synthesize a fully physically crosslinked hydrogel with good rheological properties without compromising its tissue adhesion strength. In this paper, a physically crosslinked hydrogel was developed from a mixture of chitosan and pullulan in different polymer volume ratios using aqueous NaOH. Fourier transform infrared spectroscopy, scanning electron microscopy, thermal analysis, rheological and lap shear tests were used to evaluate the influence of polymer volume ratios on the rheological, and tissue adhesive properties of the hydrogels. It was found that the hydrogels possessed high tissue adhesive strength ranging from 18.0 ± 0.90 to 49.0 ± 2.45 kPa and good storage moduli up to 5.157 ± 1.062 kPa. Gentamicin was incorporated into this polymer matrix and the release profile was investigated. The ratio of chitosan and pullulan to obtain hydrogels with optimum viscoelastic and tissue adhesive properties was identified to be CS/PUL 2:1. These results indicated that the synthesized hydrogels can be potential materials for biomedical applications such as medical adhesives and wound dressings.

"Review of strategic methods for encapsulating essential oils into chitosan nanosystems and their applications"

Essential oils (EOs) are hydrophobic, concentrated extracts of botanical origin containing diverse bioactive molecules that have been used for their biomedical properties. On the other hand, the volatility, toxicity, and hydrophobicity limited their use in their pure form. Therefore, nano-encapsulation of EOs in a biodegradable polymeric platform showed a solution. Chitosan (CS) is a biodegradable polymer that has been intensively used for EOs encapsulation. Various approaches such as homogenization, probe sonication, electrospinning, and 3D printing have been utilized to integrate EOs in CS polymer. Different CS-based platforms were investigated for EOs encapsulation such as nanoparticles (NPs), nanofibers, films, nanoemulsions, 3D printed composites, and hydrogels. Biological applications of encapsulating EOs in CS include antioxidant, antimicrobial, and anticancer functions. This review explores the principles for nanoencapsulation strategies, and the available technologies are also reviewed, in addition to an in-depth overview of the current research and application of nano-encapsulated EOs.

3D-Printed Chitosan-Based Hydrogels Loaded with Levofloxacin for Tissue Engineering Applications

Herein, we demonstrate the feasibility of a three-dimensional printed chitosan (CS)-poly(vinyl alcohol) (PVA)-gelatin (Gel) hydrogel incorporating the antimicrobial drug levofloxacin (LEV) as a potential tissue engineering scaffold. Hydrogels were prepared by physically cross-linking the polymers, and the printability of the prepared hydrogels was determined. The hydrogel with 3% w/v of CS, 3% w/v of PVA, and 2% w/v of Gel presented the best printability, producing smooth and uniform scaffolds. The integrity of 3D-printed scaffolds was improved via a neutralization process since after testing three different neutralized agents, i.e., NH3 vapors, EtOH/NaOH, and KOH solutions. It was proved that the CS/PVA/Gel hydrogel was formed by hydrogen bonds and remained amorphous in the 3D-printed structures. Drug loading studies confirmed the successful incorporation of LEV, and its in vitro release continued for 48 h. The cytotoxicity/cytocompatibility tests showed that all prepared scaffolds were cytocompatible.

Hydrogel Bioinks of Alginate and Curcumin-Loaded Cellulose Ester-Based Particles for the Biofabrication of Drug-Releasing Living Tissue Analogs

3D bioprinting is a versatile technique that allows the fabrication of living tissue analogs through the layer-by-layer deposition of cell-laden biomaterials, viz. bioinks. In this work, composite alginate hydrogel-based bioinks reinforced with curcumin-loaded particles of cellulose esters (CEpCUR) and laden with human keratinocytes (HaCaT) are developed. The addition of the CEpCUR particles, with sizes of 740 ± 147 nm, improves the rheological properties of the inks, increasing their shear stress and viscosity, while preserving the recovery rate and the mechanical and viscoelastic properties of the resulting fully cross-linked hydrogels. Moreover, the presence of these particles reduces the degradation rate of the hydrogels from 26.3 ± 0.8% (ALG) to 18.7 ± 1.3% (ALG:CEpCUR_10%) after 3 days in the culture medium. The 3D structures printed with the ALG:CEpCUR inks reveal increased printing definition and the ability to release curcumin (with nearly 70% of cumulative release after 24 h in PBS). After being laden with HaCaT cells (1.2 × 106 cells mL-1), the ALG:CEpCUR bioinks can be successfully 3D bioprinted, and the obtained living constructs show good dimensional stability and high cell viabilities at 7 days post-bioprinting (nearly 90%), confirming their great potential for application in fields like wound healing.

Chitosan and its derivatives in 3D/4D (bio) printing for tissue engineering and drug delivery applications

Tissue engineering research has undergone to a revolutionary improvement, thanks to technological advancements, such as the introduction of bioprinting technologies. The ability to develop suitable customized biomaterial inks/bioinks, with excellent printability and ability to promote cell proliferation and function, has a deep impact on such improvements. In this context, printing inks based on chitosan and its derivatives have been instrumental. Thus, the current review aims at providing a comprehensive overview on chitosan-based materials as suitable inks for 3D/4D (bio)printing and their applicability in creating advanced drug delivery platforms and tissue engineered constructs. Furthermore, relevant strategies to improve the mechanical and biological performances of this biomaterial are also highlighted.

Rapid Prototyping of 3D-Printed AgNPs- and Nano-TiO2-Embedded Hydrogels as Novel Devices with Multiresponsive Antimicrobial Capability in Wound Healing

Two antimicrobial agents such as silver nanoparticles (AgNPs) and titanium dioxide (TiO₂) have been formulated with natural polysaccharides (chitosan or alginate) to develop innovative inks for the rapid, customizable, and extremely accurate manufacturing of 3D-printed scaffolds useful as dressings in the treatment of infected skin wounds. Suitable chemical-physical properties for the applicability of these innovative devices were demonstrated through the evaluation of water content (88-93%), mechanical strength (Young's modulus 0.23-0.6 MPa), elasticity, and morphology. The antimicrobial tests performed against Staphylococcus aureus and Pseudomonas aeruginosa demonstrated the antimicrobial activities against Gram+ and Gram- bacteria of AgNPs and TiO₂ agents embedded in the chitosan (CH) or alginate (ALG) macroporous 3D hydrogels (AgNPs MIC starting from 5 µg/mL). The biocompatibility of chitosan was widely demonstrated using cell viability tests and was higher than that observed for alginate. Constructs containing AgNPs at 10 µg/mL concentration level did not significantly alter cell viability as well as the presence of titanium dioxide; cytotoxicity towards human fibroblasts was observed starting with an AgNPs concentration of 100 µg/mL. In conclusions, the 3D-printed dressings developed here are cheap, highly defined, easy to manufacture and further apply in personalized antimicrobial medicine applications.

Porous Chitosan Hydrogels Produced by Physical Crosslinking: Physicochemical, Structural, and Cytotoxic Properties

Chitosan hydrogels are biomaterials with excellent potential for biomedical applications. In this study, chitosan hydrogels were prepared at different concentrations and molecular weights by freeze-drying. The chitosan sponges were physically crosslinked using sodium bicarbonate as a crosslinking agent. The X-ray spectroscopy (XPS and XRD diffraction), equilibrium water content, microstructural morphology (confocal microscopy), rheological properties (temperature sweep test), and cytotoxicity of the chitosan hydrogels (MTT assay) were investigated. XPS analysis confirmed that the chitosan hydrogels obtained were physically crosslinked using sodium bicarbonate. The chitosan samples displayed a semi-crystalline nature and a highly porous structure with mean pore size between 115.7 ± 20.5 and 156.3 ± 21.8 µm. In addition, the chitosan hydrogels exhibited high water absorption, showing equilibrium water content values from 23 to 30 times their mass in PBS buffer and high thermal stability from 5 to 60 °C. Also, chitosan hydrogels were non-cytotoxic, obtaining cell viability values ≥ 100% for the HT29 cells. Thus, physically crosslinked chitosan hydrogels can be great candidates as biomaterials for biomedical applications.

A Novel Chitosan Composite Biomaterial with Drug Eluting Capacity for Maxillary Bone Regeneration

Bone grafting is one of the most commonly performed treatments for bone healing or repair. Autografts, grafts from the same patient, are the most frequently used bone grafts because they can provide osteogenic cells and growth factors at the site of the implant with reduced risk of rejection or transfer of diseases. Nevertheless, this type of graft presents some drawbacks, such as pain, risk of infection, and limited availability. For this reason, synthetic bone grafts are among the main proposals in regenerative medicine. This branch of medicine is based on the development of new biomaterials with the goal of increasing bone healing capacity and, more specifically in dentistry, they aim at simultaneously preventing or eliminating bacterial infections. The use of fibers made of chitosan (CS) and hydroxyapatite (HA) loaded with an antibiotic (doxycycline, DX) and fabricated with the help of an injection pump is presented as a new strategy for improving maxillary bone regeneration. In vitro characterization of the DX controlled released from the fibers was quantified after mixing different amounts of HA (10-75%). The 1% CS concentration was stable, easy to manipulate and exhibited adequate cuttability and pH parameters. The hydroxyapatite concentration dictated the combined fast and controlled release profile of CSHA50DX. Our findings demonstrate that the CS-HA-DX complex may be a promising candidate graft material for enhancing bone tissue regeneration in dental clinical practice.

Expanding the knowledge around antitubercular 5-(2-aminothiazol-4-yl)isoxazole-3-carboxamides: Hit-to-lead optimization and release of a novel antitubercular chemotype via scaffold derivatization

Tuberculosis is one of the deadliest infectious diseases in the world, and the increased number of multidrug-resistant and extensively drug-resistant strains is a reason for concern. We have previously reported a series of substituted 5-(2-aminothiazol-4-yl)isoxazole-3-carboxamides with growth inhibitory activity against Mycobacterium tuberculosis strains and low propensity to be substrate of efflux pumps. Encouraged by these preliminary results, we have undertaken a medicinal chemistry campaign to determine the metabolic fate of these compounds and to delineate a reliable body of Structure-Activity Relationships. Keeping intact the (thiazol-4-yl)isoxazole-3-carboxamide core, as it is deemed to be the pharmacophore of the molecule, we have extensively explored the structural modifications able to confer good activity and avoid rapid clearance. Also, a small set of analogues based on isostere manipulation of the 2-aminothiazole were prepared and tested, with the aim to disclose novel antitubercular chemotypes. These studies, combined, were instrumental in designing improved compounds such as 42g and 42l, escaping metabolic degradation by human liver microsomes and, at the same time, maintaining good antitubercular activity against both drug-susceptible and drug-resistant strains.

Improving Chitosan Hydrogels Printability: A Comprehensive Study on Printing Scaffolds for Customized Drug Delivery

Chitosan is an interesting polymer to produce hydrogels suitable for the 3D printing of customized drug delivery systems. This study aimed at the achievement of chitosan-based scaffolds suitable for the incorporation of active components in the matrix or loaded into the pores. Several scaffolds were printed using different chitosan-based hydrogels. To understand which parameters would have a greater impact on printability, an optimization study was conducted. The scaffolds with the highest printability were obtained with a chitosan hydrogel at 2.5 wt%, a flow speed of 0.15 mm/s and a layer height of 0.41 mm. To improve the chitosan hydrogel printability, starch was added, and a design of experiments with three factors and two responses was carried out to find out the optimal starch supplementation. It was possible to conclude that the addition of starch (13 wt%) to the chitosan hydrogel improved the structural characteristics of the chitosan-based scaffolds. These scaffolds showed potential to be tested in the future as drug-delivery systems.

3D Printed Chitosan/Alginate Hydrogels for the Controlled Release of Silver Sulfadiazine in Wound Healing Applications: Design, Characterization and Antimicrobial Activity

The growing demand for personalized medicine requires innovation in drug manufacturing to combine versatility with automation. Here, three-dimensional (3D) printing was explored for the production of chitosan (CH)/alginate (ALG)-based hydrogels intended as active dressings for wound healing. ALG hydrogels were loaded with 0.75% w/v silver sulfadiazine (SSD), selected as a drug model commonly used for the therapeutic treatment of infected burn wounds, and four different 3D CH/ALG architectures were designed to modulate the release of this active compound. CH/ALG constructs were characterized by their water content, elasticity and porosity. ALG hydrogels (Young's modulus 0.582 ± 0.019 Mpa) were statistically different in terms of elasticity compared to CH (Young's modulus 0.365 ± 0.015 Mpa) but very similar in terms of swelling properties (water content in ALG: 93.18 ± 0.88% and in CH: 92.76 ± 1.17%). In vitro SSD release tests were performed by using vertical diffusion Franz cells, and statistically significant different behaviors in terms of the amount and kinetics of drugs released were observed as a function of the construct. Moreover, strong antimicrobial potency (100% of growth inhibition) against Staphylococcus aureus and Pseudomonas aeruginosa was demonstrated depending on the type of construct, offering a proof of concept that 3D printing techniques could be efficiently applied to the production of hydrogels for controlled drug delivery.

Encapsulated salts in velvet worm slime drive its hardening

Slime expelled by velvet worms entraps prey insects within seconds in a hardened biopolymer network that matches the mechanical strength of industrial polymers. While the mechanic stimuli-responsive nature and building blocks of the polymerization are known, it is still unclear how the velvet worms' slime hardens so fast. Here, we investigated the slime for the first time, not only after, but also before expulsion. Further, we investigated the slime's micro- and nanostructures in-depth. Besides the previously reported protein nanoglobules, carbohydrates, and lipids, we discovered abundant encapsulated phosphate and carbonate salts. We also detected CO₂ bubbles during the hardening of the slime. These findings, along with further observations, suggest that the encapsulated salts in expelled slime rapidly dissolve and neutralize in a baking-powder-like reaction, which seems to accelerate the drying of the slime. The proteins' conformation and aggregation are thus influenced by shear stress and the salts' neutralization reaction, increasing the slime's pH and ionic strength. These insights into the drying process of the velvet worm's slime demonstrate how naturally evolved polymerizations can unwind in seconds, and could inspire new polymers that are stimuli-responsive or fast-drying under ambient conditions.

3D-printed scaffold composites for the stimuli-induced local delivery of bioactive adjuncts

Polysaccharide scaffolds have been successfully employed to reconstruct environments that sustain skin tissue regeneration after injuries. Three-dimensional (3D) advanced additive manufacturing technologies allow creating scaffolds with controlled and reproducible macro- and micro-structure that improve the quality of the restored tissue to favor spontaneous repair. However, when persistent inflammation occurs, the physiological tissue healing capacity is reduced, like in the presence of pathologies like diabetes, vascular diseases, chronic infection, and others. In these circumstances, the bioavailability of therapeutic adjuncts like the growth factors in addition to the standard treatments represents undoubtedly a promising strategy to accelerate the healing of skin lesions. Precisely designed polysaccharide scaffolds obtained by 3D printing represent a robust platform that can be further implemented with the controlled delivery of bioactive adjuncts. Human elastin-like polypeptides (HELPs) are stimuli-responsive biopolymers. Their structure allows the integration of domains endowed with biological functionality, making them attractive compounds to prepare composites with smart properties. In the present study, 3D-printed alginate and chitosan scaffolds were combined with the HELP components. The HELP biopolymer was fused to the epidermal growth factor (EGF) as the bioactive domain. Different constructs were prepared and the stimuli-responsive behavior as well as the biological activity were evaluated, suggesting that these smart bioactive composites are suitable to realize multifunctional dressings that sustain the local release of therapeutic adjuncts.

Biomaterials for Regenerative Medicine in Italy: Brief State of the Art of the Principal Research Centers

Regenerative medicine is the branch of medicine that effectively uses stem cell therapy and tissue engineering strategies to guide the healing or replacement of damaged tissues or organs. A crucial element is undoubtedly the biomaterial that guides biological events to restore tissue continuity. The polymers, natural or synthetic, find wide application thanks to their great adaptability. In fact, they can be used as principal components, coatings or vehicles to functionalize several biomaterials. There are many leading centers for the research and development of biomaterials in Italy. The aim of this review is to provide an overview of the current state of the art on polymer research for regenerative medicine purposes. The last five years of scientific production of the main Italian research centers has been screened to analyze the current advancement in tissue engineering in order to highlight inputs for the development of novel biomaterials and strategies.

Indirect Additive Manufacturing: A Valid Approach to Modulate Sorption/Release Profile of Molecules from Chitosan Hydrogels

This work studied the influence of hydrogel’s physical properties (geometry and hierarchical roughness) on the in vitro sorption/release profiles of molecules. To achieve this goal, chitosan (CS) solutions were cast in 3D-printed (3DP) molds presenting intricate shapes (cubic and half-spherical with/without macro surface roughness) and further immersed in alkaline solutions of NaOH and NaCl. The resulting physically crosslinked hydrogels were mechanically stable in aqueous environments and successfully presented the shapes and geometries imparted by the 3DP molds. Sorption and release profiles were evaluated using methyl orange (MO) and paracetamol (PMOL) as model molecules, respectively. Results revealed that distinct MO sorption/PMOL release profiles were obtained according to the sample’s shape and presence/absence of hierarchical roughness. MO sorption capacity of CS samples presented both dependencies of hierarchical surface and geometry parameters. Hence, cubic samples without a hierarchical surface presented the highest (up to 1.2 × greater) dye removal capacity. Moreover, PMOL release measurements were more dependent on the surface area of hydrogels, where semi-spherical samples with hierarchical roughness presented the fastest (~1.13 × faster) drug delivery profiles. This work demonstrates that indirect 3DP (via fused filament fabrication (FFF) technology) could be a simple strategy to obtain hydrogels with distinct sorption/release profiles.

Bioink Formulation and Machine Learning-Empowered Bioprinting Optimization

Bioprinting enables the fabrication of complex, heterogeneous tissues through robotically-controlled placement of cells and biomaterials. It has been rapidly developing into a powerful and versatile tool for tissue engineering. Recent advances in bioprinting modalities and biofabrication strategies as well as new materials and chemistries have led to improved mimicry and development of physiologically relevant tissue architectures constituted with multiple cell types and heterogeneous spatial material properties. Machine learning (ML) has been applied to accelerate these processes. It is a new paradigm for bioprinting. In this review, we explore current trends in bioink formulation and how ML has been used to accelerate optimization and enable real-time error detection as well as to reduce the iterative steps necessary for bioink formulation. We examined how rheometric properties, including shear storage, loss moduli, viscosity, shear-thinning property of biomaterials affect the printability of a bioink. Furthermore, we scrutinized the interplays between yield shear stress and the printability of a bioink. Moreover, we systematically surveyed the application of ML in precision in situ surgical site bioprinting, closed-loop AI printing, and post-printing optimization.

A Guide to Polysaccharide-Based Hydrogel Bioinks for 3D Bioprinting Applications

Three-dimensional (3D) bioprinting is an innovative technology in the biomedical field, allowing the fabrication of living constructs through an approach of layer-by-layer deposition of cell-laden inks, the so-called bioinks. An ideal bioink should possess proper mechanical, rheological, chemical, and biological characteristics to ensure high cell viability and the production of tissue constructs with dimensional stability and shape fidelity. Among the several types of bioinks, hydrogels are extremely appealing as they have many similarities with the extracellular matrix, providing a highly hydrated environment for cell proliferation and tunability in terms of mechanical and rheological properties. Hydrogels derived from natural polymers, and polysaccharides, in particular, are an excellent platform to mimic the extracellular matrix, given their low cytotoxicity, high hydrophilicity, and diversity of structures. In fact, polysaccharide-based hydrogels are trendy materials for 3D bioprinting since they are abundant and combine adequate physicochemical and biomimetic features for the development of novel bioinks. Thus, this review portrays the most relevant advances in polysaccharide-based hydrogel bioinks for 3D bioprinting, focusing on the last five years, with emphasis on their properties, advantages, and limitations, considering polysaccharide families classified according to their source, namely from seaweed, higher plants, microbial, and animal (particularly crustaceans) origin.

Investigation of the 3D Printability of Covalently Cross-Linked Polypeptide-Based Hydrogels

The 3D printability of poly(l-lysine-ran-l-alanine) and four-arm poly(ethylene glycol) (P(KA)/4-PEG) hydrogels as 3D biomaterial inks was investigated using two approaches to develop P(KA)/4-PEG into 3D biomaterial inks. Only the "composite microgel" inks were 3D printable. In this approach, P(KA)/4-PEG hydrogels were processed into microparticles and incorporated into a polymer solution to produce a composite microgel paste. Polymer solutions composed of either 4-arm PEG-acrylate (4-PEG-Ac), chitosan (CS), or poly(vinyl alcohol) (PVA) were used as the matrix material for the composite paste. The three respective composite microgel inks displayed good 3D printability in terms of extrudability, layer-stacking ability, solidification mechanism, and 3D print fidelity. The biocompatibility of P(KA)/4-PEG hydrogels was retained in the 3D printed scaffolds, and the biofunctionality of bioinert 4-PEG and PVA hydrogels was enhanced. CS-P(KA)/4-PEG inks demonstrated excellent 3D printability and proved highly successful in printing scaffolds with a narrow strand diameter (∼200 μm) and narrow strand spacing (∼500 μm) while the integrity of the vertical and horizontal pores was maintained. Using different needle IDs and strand spacing, certain physical properties of the hydrogels could be tuned, while the 3D printed porosity was kept constant. This included the surface area to volume ratio, the macropore sizes, and the mechanical properties. The scaffolds demonstrated adequate adhesion and spreading of NIH 3T3 fibroblasts seeded on the scaffold surfaces for 4 days. Consequently, the scaffolds were considered suitable for potential applications in wound healing, as well as other soft tissue engineering applications. Apart from the contribution to new 3D biomaterial inks, this work also presented a new and facile method of processing covalently cross-linked hydrogels into 3D printed scaffolds. This could potentially "unlock" the 3D printability of biofunctional hydrogels, which are generally excluded from 3D printing applications.

pH-Induced 3D Printable Chitosan Hydrogels for Soft Actuation

Three-dimensional (3D) printing represents a suitable technology for the development of biomimetic scaffolds for biomedical and tissue engineering applications. However, hydrogel-based inks’ printability remains a challenge due to their restricted print accuracy, mechanical properties, swelling or even cytotoxicity. Chitosan is a natural-derived polysaccharide that has arisen as a promising bioink due to its biodegradability, biocompatibility, sustainability and antibacterial properties, among others, as well as its ability to form hydrogels under the influence of a wide variety of mechanisms (thermal, ionic, pH, covalent, etc.). Its poor solubility at physiological pH, which has traditionally restricted its use, represents, on the contrary, the simplest way to induce chitosan gelation. Accordingly, herein a NaOH strong base was employed as gelling media for the direct 3D printing of chitosan structures. The obtained hydrogels were characterized in terms of morphology, chemical interactions, swelling and mechanical and rheological properties in order to evaluate the influence of the gelling solution’s ionic strength on the hydrogel characteristics. Further, the influence of printing parameters, such as extrusion speed (300, 600 and 800 mm/min) and pressure (20–35 kPa) and the cytocompatibility were also analyzed. In addition, printed gels show an electro-induced motion due to their polycationic nature, which highlights their potential as soft actuators and active scaffolds.

Adipose-Derived Stem Cell-Incubated HA-Rich Sponge Matrix Implant Modulates Oxidative Stress to Enhance VEGF and TGF-β Secretions for Extracellular Matrix Reconstruction In Vivo

This study demonstrated both adipose-derived stem cells (ASCs) in vitro and in vivo combined with three-dimensional (3D) porous sponge matrices on implant wound healing. Sponge matrices were created from hyaluronic acid (HA), collagen (Col), and gelatin (Gel), constructing two types: HA-L (low content) and HA-H (high content), to be cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Fourier transform infrared spectroscopy method verified carboxyl groups of HA and amino groups of Col and Gel reacting between the raw materials and scaffolds to identify the successive cross-linking. The swelling ratios of two types of sponge matrices were analyzed by water absorption capabilities, and the results displayed both over 30-fold dry scaffold weight enhancements. In biodegradation tests, matrices were hydrolyzed over time by three cutaneous enzymes, hyaluronidase, lysozyme, and collagenase I. ASCs from rats were cultured within the HA-H scaffold, demonstrating higher antioxidative abilities and secretions on related genes and proteins compared to the other two groups. The ASC HA-H matrix promoted cell proliferation to stimulate capillary angiogenesis inducer secretions, including vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β). In vivo histological examinations showed ASCs from implanted HA-H implant transported into the subcutis, and rat skin cells also infiltrated into the original matrix zone to increase the extracellular matrix (ECM) reconstructions. Our experimental data revealed that the ASC HA-H sponge implant was effective in improving wound repair.

3D Food Printing: Principles of Obtaining Digitally-Designed Nourishment

Three-dimensional printing (3DP) technology gained significance in the fields of medicine, engineering, the food industry, and molecular gastronomy. 3D food printing (3DFP) has the main objective of tailored food manufacturing, both in terms of sensory properties and nutritional content. Additionally, global challenges like food-waste reduction could be addressed through this technology by improving process parameters and by sustainable use of ingredients, including the incorporation of recovered nutrients from agro-industrial by-products in printed nourishment. The aim of the present review is to highlight the implementation of 3DFP in personalized nutrition, considering the technology applied, the texture and structure of the final product, and the integrated constituents like binding/coloring agents and fortifying ingredients, in order to reach general acceptance of the consumer. Personalized 3DFP refers to special dietary necessities and can be promising to prevent different non-communicable diseases through improved functional food products, containing bioactive compounds like proteins, antioxidants, phytonutrients, and/or probiotics.

Biocompatible 3D Printed Chitosan-Based Scaffolds Containing α-Tocopherol Showing Antioxidant and Antimicrobial Activity

Active dressings acting on multiple fronts are requested in the field of care for chronic skin ulcers in order to ameliorate patient compliance and tissue restoration. Currently, three-dimensional polymeric hydrogels are widely investigated; however, no prototypes aiming to control oxidative stress and bacterial proliferation in the wound bed have been developed up until now. The present work describes the formulation of a novel chitosan-based printable material containing α-tocopherol at stable dosages to obtain reproducible 3D scaffolds possessing antioxidant and antimicrobial activity without the use of organic solvents. Stability assays mimicking the manufacturing process and storage conditions reveal no significant drug loss. Chemico-physical characterizations including porosity and behavior after dehydration/hydration demonstrate that the dressings are highly porous, can be dehydrated up to 80%, and can recover more than 90% of water upon 1 h of rehydration. Elasticity determined by stress/strain tests was higher than human skin and was sufficiently resistant for potential clinical manipulation. Footage of fibroblasts in in vitro cultures demonstrated the biocompatibility of the constructs over 28 days. Finally, scaffolds loaded with α-tocopherol showed dose-dependent antioxidant activity (up to 80% in less than 1 h), while antimicrobial action versus multi-drug resistant strains of Pseudomonas aeruginosa and Staphilococcus aureus was assessed by inhibition rings obtained through the Kirby–Bauer technique. The proposed hydrogels can be useful as dressings for the treatment of chronically infected wounds.

Cultured Horse Articular Chondrocytes in 3D-Printed Chitosan Scaffold With Hyaluronic Acid and Platelet Lysate

Three-dimensional (3D) printing has gained popularity in tissue engineering and in the field of cartilage regeneration. This is due to its potential to generate scaffolds with spatial variation of cell distribution or mechanical properties, built with a variety of materials that can mimic complex tissue architecture. In the present study, horse articular chondrocytes were cultured for 2 and 4 weeks in 3D-printed chitosan (CH)-based scaffolds prepared with or without hyaluronic acid and in the presence of fetal bovine serum (FBS) or platelet lysate (PL). These 3D culture systems were analyzed in terms of their capability to maintain chondrocyte differentiation in vitro. This was achieved by evaluating cell morphology, immunohistochemistry (IHC), gene expression of relevant cartilage markers (collagen type II, aggrecan, and Sox9), and specific markers of dedifferentiated phenotype (collagen type I, Runx2). The morphological, histochemical, immunohistochemical, and molecular results demonstrated that the 3D CH scaffold is sufficiently porous to be colonized by primary chondrocytes. Thereby, it provides an optimal environment for the colonization and synthetic activity of chondrocytes during a long culture period where a higher rate of dedifferentiation can be generally observed. Enrichment with hyaluronic acid provides an optimal microenvironment for a more stable maintenance of the chondrocyte phenotype. The use of 3D CH scaffolds causes a further increase in the gene expression of most relevant ECM components when PL is added as a substitute for FBS in the medium. This indicates that the latter system enables a better maintenance of the chondrocyte phenotype, thereby highlighting a fair balance between proliferation and differentiation.

Polymeric Biomaterials for the Treatment of Cardiac Post-Infarction Injuries

Cardiac regeneration aims to reconstruct the heart contractile mass, preventing the organ from a progressive functional deterioration, by delivering pro-regenerative cells, drugs, or growth factors to the site of injury. In recent years, scientific research focused the attention on tissue engineering for the regeneration of cardiac infarct tissue, and biomaterials able to anatomically and physiologically adapt to the heart muscle have been proposed as valuable tools for this purpose, providing the cells with the stimuli necessary to initiate a complete regenerative process. An ideal biomaterial for cardiac tissue regeneration should have a positive influence on the biomechanical, biochemical, and biological properties of tissues and cells; perfectly reflect the morphology and functionality of the native myocardium; and be mechanically stable, with a suitable thickness. Among others, engineered hydrogels, three-dimensional polymeric systems made from synthetic and natural biomaterials, have attracted much interest for cardiac post-infarction therapy. In addition, biocompatible nanosystems, and polymeric nanoparticles in particular, have been explored in preclinical studies as drug delivery and tissue engineering platforms for the treatment of cardiovascular diseases. This review focused on the most employed natural and synthetic biomaterials in cardiac regeneration, paying particular attention to the contribution of Italian research groups in this field, the fabrication techniques, and the current status of the clinical trials.

Recent Advances in 3D Printing for Parenteral Applications

3D printing has emerged as an advanced manufacturing technology in the field of pharmaceutical sciences. Despite much focus on enteral applications, there has been a lack of research focused on potential benefits of 3D printing for parenteral applications such as wound dressings, biomedical devices, and regenerative medicines. 3D printing technologies, including fused deposition modeling, vat polymerization, and powder bed printing, allow for rapid prototyping of personalized medications, capable of producing dosage forms with flexible dimensions based on patient anatomy as well as dosage form properties such as porosity. Considerations such as printing properties and material selection play a key role in determining overall printability of the constructs. These parameters also impact drug release kinetics, and mechanical properties of final printed constructs, which play a role in modulating immune response upon insertion in the body. Despite challenges in sterilization of printed constructs, additional post-printing processing procedures, and lack of regulatory guidance, 3D printing will continue to evolve to meet the needs of developing effective, personalized medicines for parenteral applications.

A reusable chitosan/TiO2@g-C3N4 nanocomposite membrane for photocatalytic removal of multiple toxic water pollutants under visible light

Photocatalysis has been proved to be a promising approach in wastewater purification. However, it is hard to recycle powdery photocatalysts from wastewater in industry, but immobilizing them using larger materials can overcome this drawback. For that reason, TiO₂@g-C₃N₄ was embedded into chitosan to synthesize a highly reusable and visible-light-driven chitosan/TiO₂@g-C₃N₄ nanocomposite membrane (CTGM). CTGM showed enhanced photoactivity and the photocatalytic efficiencies of the toxic water pollutants methyl orange (M.O.), rhodamine B (Rh.B), chromium (VI) (Cr (VI)), 2,4-dichlorophenol (2,4-DCP) and atrazine (ATZ) were more than 90% under visible light at ambient conditions. Significantly, CTGM was easy to recycle and showed excellent reusability: there was no decrease in the photocatalytic decolorization efficiency of Rh.B throughout 10 cycles. A continuous-flow photocatalysis system was set up and 90% of Rh.B was effectively decolorized. A simple approach was developed to prepare a novel, effective and visible-light-driven membrane that was easy to reuse, and a feasible photocatalysis continuous-flow system was designed to be a reference for wastewater treatment in industry.

Rheology and direct write printing of chitosan - graphene oxide nanocomposite hydrogels for differentiation of neuroblastoma cells

The direct write printing method has gained popularity in synthesizing scaffolds for tissue engineering. To achieve an excellent printability of scaffolds, a thorough evaluation of rheological properties is required. We report the synthesis, characterization, rheology, and direct-write printing of chitosan - graphene oxide (CH - GO) nanocomposite hydrogels at a varying concentration of GO in 3 and 4 wt% CH polymeric gels. Rheological characterization of CH - GO hydrogels shows that an addition of only 0.5 wt% of GO leads to a substantial increase in storage modulus (G'), viscosity, and yield stress of 3 and 4 wt% of CH hydrogels. A three-interval thixotropy test (3ITT) shows that 3 wt% CH with 0.5 wt% GO hydrogel has 94% recovery of G' after 7 sequential stress cycles and is the best candidate for direct-write printing. Neuronal cell culture on 3 wt% CH with 0.5 wt% hydrogels reveals that GO promotes the differentiation of SH-SY5Y cells.

Bioinks-materials used in printing cells in designed 3D forms

Use of materials to activate non-functional or damaged organs and tissues goes back to early ages. The first materials used for this purpose were metals, and in time, novel materials such as ceramics, polymers and composites were introduced to the field to serve in medical applications. In the last decade, the advances in material sciences, cell biology, technology and engineering made 3D printing of living tissues or organ models in the designed structure and geometry possible by using cells alone or together with hydrogels through additive manufacturing. This review aims to give a brief information about the chemical structures and properties of bioink materials and their applications in the production of 3D tissue constructs.

Chitosan hydrogels in 3D printing for biomedical applications

Tissue engineering and regenerative medicine have entered a new stage of development by the recent progress in biology, material sciences, and particularly an emerging additive manufacturing technique, three-dimensional (3D) printing. 3D printing is an advanced biofabrication technique which can generate patient-specific scaffolds with highly complex geometries while hosting cells and bioactive agents to accelerate tissue regeneration. Chitosan hydrogels themselves have been widely used for various biomedical applications due to its abundant availability, structural features and favorable biological properties; however, the 3D printing of chitosan-based hydrogels is still under early exploration. Therefore, 3D printing technologies represent a new avenue to explore the potential application of chitosan as an ink for 3D printing, or as a coating on other 3D printed scaffolds. The combination of chitosan-based hydrogels and 3D printing holds much promise in the development of next generation biomedical implants.

Preliminary Evaluation of 3D Printed Chitosan/Pectin Constructs for Biomedical Applications

In the present study, chitosan (CS) and pectin (PEC) were utilized for the preparation of 3D printable inks through pneumatic extrusion for biomedical applications. CS is a polysaccharide with beneficial properties; however, its printing behavior is not satisfying, rendering the addition of a thickening agent necessary, i.e., PEC. The influence of PEC in the prepared inks was assessed through rheological measurements, altering the viscosity of the inks to be suitable for 3D printing. 3D printing conditions were optimized and the effect of different drying procedures, along with the presence or absence of a gelating agent on the CS-PEC printed scaffolds were assessed. The mean pore size along with the average filament diameter were measured through SEM micrographs. Interactions among the characteristic groups of the two polymers were evident through FTIR spectra. Swelling and hydrolysis measurements confirmed the influence of gelation and drying procedure on the subsequent behavior of the scaffolds. Ascribed to the beneficial pore size and swelling behavior, fibroblasts were able to survive upon exposure to the ungelated scaffolds.

3D Printed Chitosan Composite Scaffold for Chondrocytes Differentiation

AIMS

Our aim is to develop 3D printed chitosan-gelatin-alginate scaffolds using a costeffective in house designed 3D printer followed by its characterization. To observe chondrocyte differentiation on 3D printed scaffolds as part of scaffold application.

BACKGROUND

Cartilage is considered to be a significant tissue in humans. It is present in between the rib cage, the lobe of the ear, nasal septum in the form of hyaline cartilage, in between ribs costal cartilage, intervertebral discs in the form of fibrocartilage, meniscus, larynx, epiglottis and between various joints of bones. To replace or repair damaged tissues due to disorders or trauma, thousands of surgical procedures are performed daily. 3D printing plays a crucial role in the development of controlled porous architectures of scaffolds for cartilage tissue regeneration. Advancement in 3D printing technology like inkjet, micro- extrusion in 3D bioprinting, Laser-assisted 3D Bioprinting (LAB), stereolithography combination with biomaterials plays a crucial role in the quick development of patient-specific articulating cartilage when need in a short period frame.

OBJECTIVE

Our objective is to develop different compositions of chitosan-gelatin-alginate composite hydrogel scaffolds with controlled porosity and architectures with the application of 3D printing and observe the growth of cartilage on it. To achieve as proposed, an in-house 3D paste extruder printer was developed, which is capable of printing porous composite chitosan hydrogel scaffolds of desired architecture layer by layer. After the characterization of 3D printed chitosan composite scaffolds, the differentiation of chondrocyte was observed using hMSC.

METHODS

In present paper process for the development of chitosan-alginate-gelatin composite hydrogel, 3D printing, morphological characterization, and observation for differentiation of chondrocytes cells on 3D printed chitosan composite hydrogels is presented. The present study is divided into three parts: in first part development of composite chitosan-alginate-gelatin hydrogel with the utilization of in house customized assembled paste extruder based 3D printer, which is capable of printing chitosan composite hydrogels. In the second part, the characterization of 3D printed chitosan composite scaffolds hydrogel is performed for evaluating the morphological, mechanical, and physical properties. The prepared composite scaffolds were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction(XRD), Scanning Electron Microscopy SEM, swelling property, mechanical testing, porosity, etc. In the last part of the study, the differentiation of chondrocytes cells was observed with human Mesenchymal Stem Cells (hMSC) on 3D printed scaffolds and showed positive results for the same.

RESULTS

Stereolithography (STL) files of 3D models for porous chitosan composite were developed using Computer-Aided Design (CAD) and printed with a hydrogel flow rate within the range of 0.2-0.25 ml/min. The prepared scaffolds are highly porous, having optimum porosity, optimal mechanical strength to sustain the cartilage formation. The 3D printed chitosan composite scaffolds show supports for the differentiation of chondrocytes. The above study is helpful for in-vivo regeneration of cartilage for patients having related cartilage disorders.

CONCLUSION

This method helps in regeneration of degenerated cartilage for patient-specific and form above experiment we also concluded that 3D printed chitosan scaffold is best suited for the regeneration of chondrocyte cells.

Characterization of Bacterial Cellulose-Based Wound Dressing in Different Order Impregnation of Chitosan and Collagen

Bacterial cellulose (BC), chitosan (Chi), and collagen (Col) are known as biopolymers which have met some properties that are required as wound dressing. This study focused on investigating the fabrication of BC-based wound dressing with chitosan and collagen, since chitosan has red blood cells binding and anti-bacterial properties, while collagen can support cell and tissue growth for skin wounds. The BC-based wound dressing was prepared by impregnating BC fibers in the chitosan and/or collagen solution for 24 h. FTIR was used to confirm the intermolecular interaction of amine and hydroxyl group of chitosan and/or collagen in BC-based wound dressing. Furthermore, the XRD diffractogram of the wound dressing show broader peaks at 14.2°, 16.6°, and 22.4° due to the presence of chitosan and collagen molecules in BC fibers. These results were then supported by SEM images which confirmed that chitosan and collagen were well penetrated into BC fibers. TGA curves revealed that BC/Chi/Col has better thermal properties based on the Tmax compare to BC/Col/Chi. Feasibility of the mats to be applied as wound dressing was also supported by other tests, i.e., water content, porosity, and hemocompatibility, which indicates that the wound dressing is classified as nonhemolytic materials. However, BC/Col/Chi was considered a more potential wound dressing to be applied compared to BC/Chi/Col since it has larger pores and showed better antibacterial properties (larger zones of inhibition) against S. aureus and E. coli via disk diffusion tests.

The adaptation of lipid profile of human fibroblasts to alginate 2D films and 3D printed scaffolds

BACKGROUND

The investigation of the interactions between cells and active materials is pivotal in the emerging 3D printing-biomaterial application fields. Here, lipidomics has been used to explore the early impact of alginate (ALG) hydrogel architecture (2D films or 3D printed scaffolds) and the type of gelling agent (CaCl₂ or FeCl₃) on the lipid profile of human fibroblasts.

METHODS

2D and 3D ALG scaffolds were prepared and characterized in terms of water content, swelling, mechanical resistance and morphology before human fibroblast seeding (8 days). Using a liquid chromatography-triple quadrupole-tandem mass spectrometry approach, selected ceramides (CER), lysophosphatidylcholines (LPC), lysophosphatidic acids (LPA) and free fatty acids (FFA) were analyzed.

RESULTS

The results showed a clear alteration in the CER expression profile depending of both the geometry and the gelling agent used to prepare the hydrogels. As for LPCs, the main parameter affecting their distribution is the scaffold architecture with a significant decrease in the relative expression levels of the species with higher chain length (C20 to C22) for 3D scaffolds compared to 2D films. In the case of FFAs and LPAs only slight differences were observed as a function of scaffold geometry or gelling agent.

CONCLUSIONS

Variations in the cell membrane lipid profile were observed for 3D cell cultures compared to 2D and these data are consistent with activation processes occurring through the mutual interactions between fibroblasts and ALG support. These unknown physiologically relevant changes add insights into the discussion about the relationship between biomaterial and the variations of cell biological functions.

Three-Dimensional (3D) Printed Silver Nanoparticles/Alginate/Nanocrystalline Cellulose Hydrogels: Study of the Antimicrobial and Cytotoxicity Efficacy

Here, a formulation of silver nanoparticles (AgNPs) and two natural polymers such as alginate (ALG) and nanocrystalline cellulose (CNC) was developed for the 3D printing of scaffolds with large surface area, improved mechanical resistance and sustained capabilities to promote antimicrobial and cytotoxic effects. Mechanical resistance, water content, morphological characterization and silver distribution of the scaffolds were provided. As for applications, a comparable antimicrobial potency against S. aureus and P. aeruginosa was demonstrated by in vitro tests as function of the AgNP concentration in the scaffold (Minimal Inhibitory Concentration value: 10 mg/mL). By reusing the 3D system the antimicrobial efficacy was demonstrated over at least three applications. The cytotoxicity effects caused by administration of AgNPs to hepatocellular carcinoma (HepG2) cell culture through ALG and ALG/CNC scaffold were discussed as a function of time and dose. Finally, the liquid chromatography-mass spectrometry (LC-MS) technique was used for targeted analysis of pro-apoptotic initiation and executioner caspases, anti-apoptotic and proliferative proteins and the hepatocyte growth factor, and provided insights about molecular mechanisms involved in cell death induction.

The Production Possibility of the Antimicrobial Filaments by Co-Extrusion of the PLA Pellet with Chitosan Powder for FDM 3D Printing Technology

The last decades have witnessed a major advancement and development in three-dimensional (3D) printing technology. In the future, the trend’s utilization of 3D printing is expected to play an important role in the biomedical field. This work presents co-extrusion of the polylactic acid (PLA), its derivatives (sPLA), and chitosan with the aim of achieving filaments for printing 3D objects, such as biomedical tools or implants. The physicochemical and antimicrobial properties were evaluated using SEM, FT-IR, DSC, instrumental mechanical test, and based on the ASTM E2149 standard, respectively. The addition of chitosan in the PLA and sPLA filaments increased their porosity and decreased density. The FT-IR analysis showed that PLA and chitosan only formed a physical mixture after extrusion. The addition of chitosan caused deterioration of the mechanical properties of filaments, especially elongation at break and Young’s modulus. The addition of chitosan to the filaments improved their ability to crystallize and provide their antimicrobial properties against Escherichia coli and Staphylococcus aureus.

3D printed chitosan scaffolds: A new TiO2 support for the photocatalytic degradation of amoxicillin in water

TiO₂-supported chitosan scaffolds (TiO₂/CS) are here proposed as promising material for wastewater treatment, in particular for the removal of pharmaceutical compounds. TiO₂/CS are tested for the amoxicillin photodegradation under UV/Vis irradiation. Amoxicillin (AMX) is an antibiotic of the beta-lactam family. Due to the release of antibiotics in wastewater and their persistence in the environment, harmful effects can develop on the aquatic and terrestrial organisms. TiO₂ chitosan scaffolds with photocatalytic activity for wastewater remediation have been prepared by 3D printing using commercial P25-TiO₂. The formulation for the 3D printer was prepared by dispersion of chitosan and TiO₂ in powder form at the concentration 6% w/v and 1% w/v, respectively. The TiO₂ particles (crystalline anatase and rutile phases) embedded in the chitosan have a size of about 20 nm, like in the starting material, as verified by X-ray diffraction and Raman spectroscopy and are homogeneously distributed in the scaffold, also after repeated photocatalytic tests, as revealed by SEM-EDS. The mechanical properties of the 3D structures are suitable for the targeted application as they can be easily handled without breakage. The AMX photodegradation efficiency under light irradiation by TiO₂/CS made with scaffolds of different thicknesses (3, 5, 15 layers), was assessed in water by means of UV-Vis absorption and HPLC/UV measurements, at two different AMX:TiO₂ molar ratios: 1/100 and 1/10. The 3D printed TiO₂/CS system, even after repeated cycles, shows a high photodegradation efficiency, compared to the direct AMX photolysis. A zero-order kinetics for TiO₂ supported photodegradation was found, whereas a pseudo-first order was observed for water dispersed TiO₂. Mass spectrometry analysis revealed the presence of AMX degradates such as penilloic and penicilloic acids and diketopiperazine. The proposed 3D printed chitosan scaffolds may be used as reusable substrate for the TiO₂ photocatalytic degradation of antibiotic pollutants in wastewater.

Tissue Engineering Strategies for Intervertebral Disc Treatment Using Functional Polymers

Intervertebral disc (IVD) is the fibrocartilage between the vertebrae, allowing the spine to move steadily by bearing multidirectional complex loads. Aging or injury usually causes degeneration of IVD, which is one of the main reasons for low back pain prevalent worldwide and reduced quality of life. While various treatment strategies for degenerative IVD have been studied using in vitro studies, animal experiments, and clinical trials, there are unsolved limitations for endogenous regeneration of degenerative IVD. In this respect, several tissue engineering strategies that are based on the cell and scaffolds have been extensively researched with positive outcomes for regeneration of IVD tissues. Scaffolds made of functional polymers and their diverse forms mimicking the macro- and micro-structure of native IVD enhance the biological and mechanical properties of the scaffolds for IVD regeneration. In this review, we discuss diverse morphological and functional polymers and tissue engineering strategies for endogenous regeneration of degenerative IVD. Tissue engineering strategies using functional polymers are promising therapeutics for fundamental and endogenous regeneration of degenerative IVD.