Jul 2026· International Journal of Biological Macromolecules· Vol 375, pp.
153373
· 0 citations· 70 references
Medicine
TL;DR
A microgel-based biphasic bioink that leverages microgels' advantages while maintaining porosity to enhance cellular performance is developed, enabling the high-fidelity fabrication of complex, spatially controlled heterogeneous 3D structures with tunable mechanical properties.
Abstract
A primary challenge in extrusion-based bioprinting using microgel-based bioink is balancing printability, mechanical stability, and biological functionality. In this study, we developed a microgel-based biphasic bioink that leverages microgels' advantages while maintaining porosity to enhance cellular performance. This biphasic bioink consists of densely packed physically crosslinked silk acid-based microgels (SA-MG) suspended in a secondary hydrogel precursor of alginate/carboxymethyl cellulose (Alg/CMC), which crosslinks physically after printing. The resulting dynamic, hybrid matrix enhances ink cohesion during extrusion, enabling the high-fidelity fabrication of complex, spatially controlled heterogeneous 3D structures with tunable mechanical properties. Cells cultured in the biphasic system exhibit significantly enhanced proliferation, demonstrating good cytocompatibility and early signs of vascularization. This approach represents a significant advance in biofabrication of 3D printing mechanically robust scaffolds.
Extrusion‐based three‐dimensional (3D) printing has emerged as a powerful fabrication strategy in tissue engineering. However, achieving reliable printability and structural stability in hydrogel‐based systems remains a persistent challenge. Alginate‐based hydrogels are among the most widely investigated biomaterial inks for this purpose, due to their biocompatibility, biodegradability, and capacity for ionic crosslinking. This preliminary study investigated the influence of calcium chloride (CaCl
2
) concentration on the rheological behavior, extrudability, and scaffold geometric fidelity of alginate hydrogel inks for extrusion‐based 3D printing. Formulations were prepared at three CaCl
2
concentrations (2.73, 3.33, and 3.91 mg/mL) and characterized by oscillatory rheology to determine storage modulus (
G
′), loss modulus (
G
″), yield stress, and complex viscosity. Gelation behavior was evaluated through inversion assays, and printability was assessed via extrusion tests, filament spreadability analysis, and scaffold geometric fidelity evaluation across multiple printed geometries. Among the formulations evaluated, the intermediate CaCl
2
concentration (3.33 mg/mL) yielded the most favorable rheological profile, exhibiting
G
′ >
G
″ in the small‐amplitude oscillatory shear region and a yield stress compatible with continuous filament extrusion. Scaffold fidelity assessment revealed persistent structural limitations: including rounded pores, pore‐size variation, and partial layer collapse indicating that printability was improved relative to the other formulations but not fully resolved at this crosslinking level. These findings establish a rheological‐to‐printability framework for CaCl
2
‐crosslinked alginate inks, identifying yield stress and
G
′ dominance in the SAOS regime as predictive criteria for extrusion‐based printability, and provide a reproducible technical foundation for systematic formula optimization prior to biological validation and tissue engineering application.
A. L. P. de Melo, Andressa Baggio Dias, H.S. Barud et al.· Journal of Applied Polymer S...· 0 citations
This study provides a practical framework for creating intrafilamentary porosity into 3D-printed PCL scaffolds with improved surface-mediated biological performance.
Mikaela Kutrolli, Noah S Pereira, Delaram Ghanbariamin et al.· ACS Biomaterials Science & E...· 0 citations
Three-dimensional (3D) printing enables the fabrication of hydrogel constructs with precise architecture, yet developing photocurable hydrogel biomaterial ink that combine printability, structural stability, and biofunctionality remains a challenge. Here, we present a gallol-functionalized gellan gum methacrylate (GGMA-GA) hydrogel as a robust photocrosslinkable biomaterial ink for extrusion-based 3D bioprinting. A dual-crosslinking strategy was employed in which mild ionic pre-crosslinking enhances shear-thinning and print fidelity, followed by photocrosslinking of methacrylate groups to reinforce mechanical stability post-printing. Incorporation of gallol moieties provides antioxidant activity and tissue adhesion, mitigating oxidative stress and promoting construct integration. We systematically evaluated rheological and swelling properties, printability, and cytocompatibility, demonstrating that GGMA-GA hydrogels maintain structural fidelity while supporting cell viability. The combination of low swelling degree, enhanced functionality, and precise printability positions GGMA-GA as a versatile photocurable hydrogel platform for extrusion-based 3D fabrication, with potential for long-term and in situ biomedical applications.
S. Annurakshita, Hatai Jongprasitkul, Marianne Niemelä et al.· International Journal of Bio...· 0 citations
Biomedical devices for bone tissue repair require materials with a balanced combination of printability, structural integrity, and biological performance. Their fabrication is increasingly shifting toward additive manufacturing, in which thermoplastic biodegradable polymers, particularly poly(lactic acid) (PLA), serve as matrices. In this study, PLA composite filaments with varying hydroxyapatite (HAp) contents (0, 5, 10, 20, and 30 wt%) were fabricated via a solvent-assisted non-solvent-induced precipitation method and evaluated for extrusion-based bone tissue engineering applications. HAp content significantly influenced the physicochemical, rheological, mechanical, and biological performance of the composites: increasing HAp loading reduced filler dispersion homogeneity and, at 30 wt%, pronounced agglomeration and microvoid formation. Thermal analysis demonstrated that the incorporation of HAp did not significantly affect the glass transition temperature of PLA, which remained nearly constant regardless of HAp content. However, the presence of HAp shifted the cold crystallization temperature to higher values, suggesting delayed cold crystallization during heating. Intermediate HAp incorporation (5-10 wt%) provided the most favourable balance between homogeneous filler dispersion, mechanical reinforcement, and osteoblastic response, with PLA-HAp10 showing enhanced ALP activity and osteogenic gene expression together with reliable filament formation and scaffold printability. In contrast, 20 wt% HAp approached the upper composition-processing threshold of the system, while 30 wt% HAp compromised structural homogeneity and extrusion reliability. These findings highlight the importance of controlling HAp loading to achieve a balanced combination of processability, structural integrity, and osteogenic performance in PLA-based biomaterials.
Lukošiūnas Jokūbas, Šaparajavaitė Gabrielė, Dambrauskas Tadas et al.· International Journal of Bio...· 0 citations
Extrusion-based bioprinting imposes stringent mechanical constraints on bioink formulations, yet the rheological parameters governing cell survival during the printing process are rarely reported in a standardized way, limiting cross-study comparison. In this work, we systematically characterized the viscoelastic properties of alginate/methylcellulose bioinks incorporating strontium-enriched hydroxyapatite (Sr-OHAp) particles and Poloxamer 188, and assessed their effect on PANC-1 cell viability in bioprinted constructs. The power law consistency index K and pseudoplasticity index n were used as quantitative descriptors of bioink behavior. Addition of Poloxamer 188 reduced K by 52.1% in particle-free inks and by 64.6% in particle-containing inks, while n remained largely unchanged (≤2% variation), indicating that particles selectively modulate consistency without compromising shear-thinning behavior. On day 1, bioprinted constructs showed lower cell viability than cell-seeded scaffolds (53.9–58.9% vs. 96.7%); however, constructs containing Sr-OHAp (B3) displayed progressive recovery, reaching 84.0% viability by day 7, compared to 72.9% for particle-free bioinks (B1). These results demonstrate that Sr-OHAp particles act as rheological sensitizers that reduce extrusion-induced shear stress while simultaneously promoting long-term cell recovery, likely through their bioactive surface chemistry. We propose that systematic reporting of K and n indices should become standard practice in bioprinting studies to enable rational bioink design and consistent knowledge accumulation across the field.
Fiona Ye Rojo Acero, Daniel F. de Castro Hernández, M. L. Flores-Cedillo et al.· Polymers· 0 citations
The development of hydrogel bioinks that combine structural stability with biological compatibility remains a major challenge in extrusion-based 3D printing for tissue engineering. In this proof-of-concept study, bacterial cellulose (BC) obtained from kombucha fermentation was explored as a sustainable nanofibrillar component for alginate/chondroitin sulfate (CS)/silicon-substituted hydroxyapatite (Si-HA) composite inks. Following alkaline purification, mechanical processing, and freeze-drying, BC was characterized by scanning electron microscopy (SEM), ATR-FTIR spectroscopy, and X-ray diffraction (XRD), revealing a highly entangled nanofibrillar architecture with high crystallinity (85.4%) and strong hydrogen-bonding potential. Four hydrogel formulations were developed as a comparative 2 × 2 matrix, contrasting BC-containing systems with methylcellulose (MC)-containing reference systems at two Si-HA loadings. Reduced-viscosity measurements of the uncrosslinked precursor formulations showed higher values at the lower Si-HA loading in both formulation series. All formulations could be extruded as acellular inks into grid-like constructs and retained identifiable macroporous architectures after ionic crosslinking. Swelling increased between 24 and 48 h, while mass loss remained limited after the initial 24 h incubation period. In direct-contact testing with L929 fibroblasts, cell viability remained above 84% after 48 h, meeting the ISO 10993-5 non-cytotoxicity criterion. These findings support the feasibility of incorporating physically processed kombucha-derived BC into alginate-based composite inks.
E. Uțoiu, E. Oprita, V. Manoiu et al.· Fibers· 0 citations
