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Unlocking natural-based multimaterial 3D printing by engineering the nanocomposite organic/inorganic interface
J.R. Maia1, Daniel S. Fidalgo2, Marco Parente2, R. Sobreiro-Almeida1, J. F. Mano1
1 Department of Chemistry, CICECO – Aveiro Institute of Materials, University of Aveiro, 3810-193, Aveiro, Portugal
2 Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), 4200-465, Porto, Portugal
Abstract
Osteochondral defect regeneration remains a clinical challenge with no solution achieving long-term functional restoration. Effective regenerative strategies require hierarchically structured scaffolds that support both bone and cartilage repair. Three-dimensional (3D) printing using natural-based multimaterials and bioactive fillers such as hydroxyapatite or bioactive glasses offer promising approaches for fabricating such biomimetic scaffolds. However, its effectiveness can be limited by inadequate multi-material integration, poor dispersion of bioactive fillers, and suboptimal rheological and mechanical properties of natural-based materials.
In this study, we present an ink engineering approach that enables the 3D printing of nanocomposites (NC), composed of low-viscous natural-derived matrices and bioactive glass nanoparticles. By chemical coupling organic and inorganic phases, we hypothesize to achieve highly reproducible and scalable printability.
We synthesized two photocurable natural matrices: a protein - bovine serum albumin methacrylate (BSAMA), and a polysaccharide - hyaluronic acid methacrylate (HAMA). Bioactive glass nanoparticles (BGNP) were functionalized via aminosilane chemistry. Covalent crosslinking through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) facilitated homogenous BGNP immobilization, improving rheological properties, dispersion, and printability. EDC/NHS binds carboxylic groups of BSAMA/HAMA and BGNP-grafted amines. Without the phase interaction, the inks were highly heterogeneous and unprintable. Different crosslinker and BGNP amounts were tested. Visible-light photopolymerization (with lithium phenyl-2,4,6-trimethylbenzoylphosphinateensured photoinitiator) was used post-printing to form a mechanically robust construct. The NC’s rheological, mechanical, and biological behavior was evaluated. Computational simulation of material properties was performed to validate and predict its applicability.
Our findings demonstrate that the optimized NC inks transform low-viscosity precursors (<1 Pa) into shear-thinning formulations with tunable elastic and viscous moduli (50 - 500 Pa). Post-printing photocured scaffolds exhibited enhanced mechanical stability (1 - 5 kPa) and bioactivity, promoting calcium phosphate deposition in simulated body fluid. In vitro assays with adipose-derived stem cells revealed increased metabolic activity and viability. Notably, BSAMA and HAMA displayed distinct printability, cellular performance, and mechanical properties, which were leveraged for osteochondral regeneration applications. HAMA inks were mechanically more robust, whereas BSAMA inks presented higher cytocompatibility. Further, their seamless integration through photocrosslinkable moieties made them ideal for multi-tissue engineering applications, enabling the obtention of multiple geometries when printing with both materials. Computational simulations validated the performance and feasibility of 3D printed hierarchical scaffolds, confirming clinical relevance.
This work presents a reproducible ink engineering strategy that addressed key limitations of NC inks, derived from low-viscous natural-based biomaterials. This strategy allowed the fabrication of hierarchical, multi-material osteochondral-mimetic scaffolds via extrusion 3D printing.
Keywords: Nanocomposite ink engineering, Extrusion 3D printing, Computational simulation, Osteochondral hierarchical constructs.
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