Advanced PEG-tyramine biomaterial ink for precision engineering of perfusable and flexible small-diameter vascular constructs via coaxial printing.

Vascularization is crucial for providing nutrients and oxygen to cells while removing waste. Despite advances in 3D-bioprinting, the fabrication of structures with void spaces and channels remains challenging. This study presents a novel approach to create robust yet flexible and permeable small (600-1300 µm) artificial vessels in a single processing step using 3D coaxial extrusion printing of a biomaterial ink, based on tyramine-modified polyethylene glycol (PEG-Tyr). We combined the gelatin biocompatibility/activity, robustness of PEG-Tyr and alginate with the shear-thinning properties of methylcellulose (MC) in a new biomaterial ink for the fabrication of bioinspired vessels. Chemical characterization using NMR and FTIR spectroscopy confirmed the successful modification of PEG with Tyr and rheological characterization indicated that the addition of PEG-Tyr decreased the viscosity of the ink. Enzyme-mediated crosslinking of PEG-Tyr allowed the formation of covalent crosslinks within the hydrogel chains, ensuring its stability. PEG-Tyr units improved the mechanical properties of the material, resulting in stretchable and elastic constructs without compromising cell viability and adhesion. The printed vessel structures displayed uniform wall thickness, shape retention, improved elasticity, permeability, and colonization by endothelial-derived - EA.hy926 cells. The chorioallantoic membrane (CAM) and in vivo assays demonstrated the hydrogel's ability to support neoangiogenesis. The hydrogel material with PEG-Tyr modification holds promise for vascular tissue engineering applications, providing a flexible, biocompatible, and functional platform for the fabrication of vascular structures.

Optimizing phenol-modified hyaluronic acid for designing shape-maintaining biofabricated hydrogel scaffolds in soft tissue engineering.

In this study, we developed a well-printable biomaterial ink for 3D printing of shape-maintaining hydrogel scaffolds. The hydrogel base comprised tyramine-modified hyaluronic acid (HA-Tyr) and gelatin methacrylate (GelMA) and was dually cross-linked. Using the Box-Behnken design, we explored how varying the ink composition affected fiber formation and shape preservation. By adjusting the polymer ratios, we produced a stable hydrogel with varying responses, from a viscous liquid to a thick gel, and optimized 3D scaffolds that were structurally stable both during and after printing, offering precision and flexibility. Our ink exhibited shear-thinning behavior and high swelling capacity, as well as ECM-like characteristics and biocompatibility, making it an ideal candidate for soft tissues matrices with storage modulus of around 300 Pa. Animal trials and CAM assays confirmed its biocompatibility and integration with host tissue.

Printable hyaluronic acid hydrogel functionalized with yeast-derived peptide for skin wound healing.

Targeted delivery of bioactive agents, growth factors, and drugs to skin wounds is a growing trend in biomaterials development for wound healing. This study presents a printable hyaluronic acid (HA) based hydrogel to deliver yeast-derived ACE-inhibitory peptide of VLSTSFPPW (VW-9) to the wound site. We first conjugated tyramine (Ty) on the carboxyl groups of the HA to form a phenol-functionalized HA (HA-Ty); then, the carboxylic acid groups of HA-Ty were aminated with ethylenediamine (HA-Ty-NH2). The primary amine groups of the HA-Ty-NH2 could then react with the carboxylic acids of the peptide. The hydrogel was then 3D printed and crosslinked with visible light. The modification of HA was confirmed by 1H NMR and FTIR. The swelling capacity of the conjugated hydrogels was 1.5-fold higher compared to the HA-Ty-NH2 hydrogel. The conjugated peptide did not affect on rheological properties and morphology of the hydrogels. The 3T3-L1 fibroblast cells seeded on the peptide-modified hydrogels exhibited higher viability than the hydrogels without the peptide, indicating that the peptide-enriched hydrogels may have the potential for wound healing applications.

Bioengineering in salivary gland regeneration.

Salivary gland (SG) dysfunction impairs the life quality of many patients, such as patients with radiation therapy for head and neck cancer and patients with Sjögren's syndrome. Multiple SG engineering strategies have been considered for SG regeneration, repair, or whole organ replacement. An in-depth understanding of the development and differentiation of epithelial stem and progenitor cells niche during SG branching morphogenesis and signaling pathways involved in cell-cell communication constitute a prerequisite to the development of suitable bioengineering solutions. This review summarizes the essential bioengineering features to be considered to fabricate an engineered functional SG model using various cell types, biomaterials, active agents, and matrix fabrication methods. Furthermore, recent innovative and promising approaches to engineering SG models are described. Finally, this review discusses the different challenges and future perspectives in SG bioengineering.

Anionic exopolysaccharide from Cryptococcus laurentii 70766 as an alternative for alginate for biomedical hydrogels.

Alginates are widely used polysaccharides for biomaterials engineering, which functional properties depend on guluronic and mannuronic acid as the building blocks. In this study, enzymatically crosslinked hydrogels based on sodium alginate (Na-Alg) and the exopolysaccharide (EPS) derived from Cryptococcus laurentii 70766 with glucuronic acid residues were synthesized and characterized as a new potential source of polysaccharide for biomaterials engineering. The EPS was extracted (1.05 ± 0.57 g/L) through ethanol precipitation. Then the EPS and Na-Alg were functionalized with tyramine hydrochloride to produce enzymatically crosslinked hydrogels in the presence of horseradish peroxidase (HRP) and H2O2. Major characteristics of the hydrogels such as gelling time, swelling ratio, rheology, cell viability, and biodegradability were studied. The swelling ratio and degradation profile of both hydrogels showed negative values, indicating an increased crosslinking degree and a lower water uptake percentage. The EPS hydrogel showed similar gelation kinetics compared to the Alg hydrogel. The EPS and its hydrogel were found cytocompatible. The results indicate the potential of EPS from C. laurentii 70766 for biomedical engineering due to its biocompatibility and degradability. Further studies are needed to confirm this EPS as an alternative for Alg in tissue engineering applications, particularly in the development of wound dressing products.

Natural Hydrogel-Based Bio-Inks for 3D Bioprinting in Tissue Engineering: A Review.

Three-dimensional (3D) printing is well acknowledged to constitute an important technology in tissue engineering, largely due to the increasing global demand for organ replacement and tissue regeneration. In 3D bioprinting, which is a step ahead of 3D biomaterial printing, the ink employed is impregnated with cells, without compromising ink printability. This allows for immediate scaffold cellularization and generation of complex structures. The use of cell-laden inks or bio-inks provides the opportunity for enhanced cell differentiation for organ fabrication and regeneration. Recognizing the importance of such bio-inks, the current study comprehensively explores the state of the art of the utilization of bio-inks based on natural polymers (biopolymers), such as cellulose, agarose, alginate, decellularized matrix, in 3D bioprinting. Discussions regarding progress in bioprinting, techniques and approaches employed in the bioprinting of natural polymers, and limitations and prospects concerning future trends in human-scale tissue and organ fabrication are also presented.