A review on design of scaffold for osteoinduction: Toward the unification of independent design variables

Synergistic effects of calcium and zinc on bio-functionalized 3D Ti cancellous bone scaffold with enhanced osseointegration capacity in rabbit model

The present research aims to develop a Ca-Zn ion-incorporated surface functionalized 3D Ti cancellous bone scaffold for bone defect repair. The scaffold is designed to mimic human cancellous bone architecture through selective laser melting-based additive manufacturing. The chemical-based surface modification approach employed here created a Ca and Zn ions incorporated nano-porous surface layer with enhanced surface roughness and hydrophilicity. The modified biomimetic scaffold improved the corrosion resistance behaviour with ICORR and ECORR values of 0.174 mA and 0.0097 V respectively. It is learned that incorporating Zn as ZnO over the scaffold has antibacterial activity against Staphylococcus aureus and Escherichia coli. The cellular response of MG-63 to the modified scaffold was evaluated through in-vitro studies which focus on the cytocompatible properties. The intra-osseous biomimetic Ti-Na-Ca:Zn 3D scaffold revealed significant improvement in the osseointegration capabilities in terms of bone mineral density (BMD) and bone volume/total volume (BV/TV) in the rabbit model. The osseointegration potential at the Ti-Na-Ca:Zn interface was evidenced by histological analysis and micro-CT imaging. In addition to this, the remarkable upregulation of osteogenic genes such as OCN, COL1A1, OPN, ALP, RUNX2, and OSX evidences the dynamics of the osseointegration process at each surgical period. This Ca and Zn surface functionalised porous architecture of the 3D Ti cancellous bone scaffold with enhanced biological response and bone integration can potentially give insights into implant customisation along with improved clinical outcomes.

Bone Ingrowth Simulation Within the Hexanoid, a Novel Scaffold Design

The utilization of bone scaffold implants represents a promising approach for repairing substantial bone defects. In recent years, various traditional scaffold structures have been developed and, with advances in materials biology and computer technology, novel scaffold designs are now being evaluated. This study investigated the effects of a novel scaffold unit cell design (Hexanoid) through a computational framework, comparing its performance to that of four well-known scaffold designs. A finite element analysis numerical simulation and mechanical testing were conducted to analyze the dynamic bone ingrowth process and the mechanical strength of the different scaffold designs. Bone formation within the Ti-6Al-4V metal scaffolds was simulated based on the theory of bone remodeling. The outcomes of the study reveal that the novel scaffold design (Hexanoid) attains a notably elevated ultimate bone volume fraction (∼27%), it outperformed conventional unit-cell designs found in extant literature, such as cubic design with 19.1% and circular design with 16.9% in relation to the bone-to-cavity volume ratio. This novel structure also has comparable mechanical strength to that of human compact bone tissue. While the design was not optimal in every category, it provided a very satisfactory overall performance regarding certain key aspects of bone performances in comparison with the five scaffold structures evaluated. Although limitations exist in this project, similar methodologies can also be applied in the primary evaluation of new scaffold structures, resulting in improved efficiency and effectiveness. In future research, the results of this project may be integrated with clinical rehabilitation processes to offer a critical evaluation for optimization of additional novel scaffold unit-cell structure designs.

An explainable machine learning-based probabilistic framework for the design of scaffolds in bone tissue engineering

Recently, 3D-printed biodegradable scaffolds have shown great potential for bone repair in critical-size fractures. The differentiation of the cells on a scaffold is impacted among other factors by the surface deformation of the scaffold due to mechanical loading and the wall shear stresses imposed by the interstitial fluid flow. These factors are in turn significantly affected by the material properties, the geometry of the scaffold, as well as the loading and flow conditions. In this work, a numerical framework is proposed to study the influence of these factors on the expected osteochondral cell differentiation. The considered scaffold is rectangular with a 0/90 lay-down pattern and a four-layered strut made of polylactic acid with a 5% steel particle content. The distribution of the different types of cells on the scaffold surface is estimated through a scalar stimulus, calculated by using a mechanobioregulatory model. To reduce the simulation time for the computation of the stimulus, a probabilistic machine learning (ML)-based reduced-order model (ROM) is proposed. Then, a sensitivity analysis is performed using the Shapley additive explanations to examine the contribution of the various parameters to the framework stimulus predictions. In a final step, a multiobjective optimization procedure is implemented using genetic algorithms and the ROM, aiming to identify the material parameters and loading conditions that maximize the percentage of surface area populated by bone cells while minimizing the area corresponding to the other types of cells and the resorption condition. The results of the performed analysis highlight the potential of using ROMs for the scaffold design, by dramatically reducing the simulation time while enabling the efficient implementation of sensitivity analysis and optimization procedures.

Biomineralization-inspired mineralized hydrogel promotes the repair and regeneration of dentin/bone hard tissue

Maxillofacial hard tissue defects caused by trauma or infection often affect craniofacial function. Taking the natural hard tissue structure as a template, constructing an engineered tissue repair module is an important scheme to realize the functional regeneration and repair of maxillofacial hard tissue. Here, inspired by the biomineralization process, we constructed a composite mineral matrix hydrogel PAA-CMC-TDM containing amorphous calcium phosphates (ACPs), polyacrylic acid (PAA), carboxymethyl chitosan (CMC) and dentin matrix (TDM). The dynamic network composed of Ca²⁺·COO^- coordination and ACPs made the hydrogel loaded with TDM, and exhibited self-repairing ability and injectability. The mechanical properties of PAA-CMC-TDM can be regulated, but the functional activity of TDM remains unaffected. Cytological studies and animal models of hard tissue defects show that the hydrogel can promote the odontogenesis or osteogenic differentiation of mesenchymal stem cells, adapt to irregular hard tissue defects, and promote in situ regeneration of defective tooth and bone tissues. In summary, this paper shows that the injectable TDM hydrogel based on biomimetic mineralization theory can induce hard tissue formation and promote dentin/bone regeneration.

Biofabrication of Poly(glycerol sebacate) Scaffolds Functionalized with a Decellularized Bone Extracellular Matrix for Bone Tissue Engineering

The microarchitecture of bone tissue engineering (BTE) scaffolds has been shown to have a direct effect on the osteogenesis of mesenchymal stem cells (MSCs) and bone tissue regeneration. Poly(glycerol sebacate) (PGS) is a promising polymer that can be tailored to have specific mechanical properties, as well as be used to create microenvironments that are relevant in the context of BTE applications. In this study, we utilized PGS elastomer for the fabrication of a biocompatible and bioactive scaffold for BTE, with tissue-specific cues and a suitable microstructure for the osteogenic lineage commitment of MSCs. In order to achieve this, the PGS was functionalized with a decellularized bone (deB) extracellular matrix (ECM) (14% and 28% by weight) to enhance its osteoinductive potential. Two different pore sizes were fabricated (small: 100-150 μm and large: 250-355 μm) to determine a preferred pore size for in vitro osteogenesis. The decellularized bone ECM functionalization of the PGS not only improved initial cell attachment and osteogenesis but also enhanced the mechanical strength of the scaffold by up to 165 kPa. Furthermore, the constructs were also successfully tailored with an enhanced degradation rate/pH change and wettability. The highest bone-inserted small-pore scaffold had a 12% endpoint weight loss, and the pH was measured at around 7.14. The in vitro osteogenic differentiation of the MSCs in the PGS-deB blends revealed a better lineage commitment of the small-pore-sized and 28% (w/w) bone-inserted scaffolds, as evidenced by calcium quantification, ALP expression, and alizarin red staining. This study demonstrates a suitable pore size and amount of decellularized bone ECM for osteoinduction via precisely tailored PGS elastomer BTE scaffolds.