Pore Size Of Scaffolds Research Articles

Optimizing scaffold pore size for tissue engineering: insights across various tissue types

Scaffold porosity is a critical factor in replicating the complex in vivo microenvironment, directly influencing cellular interactions, migration, nutrient transfer, vascularization, and the formation of functional tissues. For optimal tissue formation, scaffold design must account for various parameters, including material composition, morphology, mechanical properties, and cellular compatibility. This review highlights the importance of interconnected porosity and pore size, emphasizing their impact on cellular behavior and tissue formation across several tissue engineering domains, such as skin, bone, cardiovascular, and lung tissues. Specific pore size ranges enhance scaffold functionality for different tissues: small pores (∼1–2 µm) aid epidermal cell attachment in skin regeneration, moderate pores (∼2–12 µm) support dermal migration, and larger pores (∼40–100 µm) facilitate vascular structures. For bone tissue engineering, multi-layered scaffolds with smaller pores (50–100 µm) foster cell attachment, while larger pores (200–400 µm) enhance nutrient diffusion and angiogenesis. Cardiovascular and lung tissues benefit from moderate pore sizes (∼25–60 µm) to balance cell integration and nutrient diffusion. By addressing critical design challenges and optimizing pore size distributions, this review provides insights into scaffold innovations, ultimately advancing tissue regeneration strategies.

Controlling the pore size of carbonate apatite honeycomb scaffolds enhances orientation and strength of regenerated bone

To restore functions of long bones and avoid reconstruction failure, segmental defects should be quickly repaired using abundant amounts of regenerated bone with high mechanical strength and orientation along the bone axis. Although both bone volume and bone matrix orientation are important for faster restoration of long bones with segmental defects, researchers have primarily focused on the former. Artificial bone scaffolds with uniaxial channels, (e.g., honeycomb (HC) scaffolds), are considered adequate for regenerating bone oriented along the bone axis. The channel size may affect the orientation, amount, and strength of the regenerated bone. In this study, we investigated the effects of channel size in carbonate apatite HC scaffolds on the orientation of bones regenerated in segmental bone defects and determined the adequate channel size. Carbonate apatite HC scaffolds, with different channel sizes (350, 550, 730, and 890 μm in length on the side of the square aperture), were fabricated by extrusion molding of a mixture of calcium carbonate and organic binder, debinding, and subsequent phosphatization to convert the composition from calcium carbonate to carbonate apatite. No significant difference in the amounts of regenerated bones was observed for different channel sizes. However, bone along the bone axis was formed in the channels ≤550 μm in size but not in channels ≥730 μm. The HC scaffolds with a channel size of 350 μm regenerated bone with higher bending strength than those with a channel size of 890 μm. However, bone regenerated with the HC scaffolds having channel sizes of 350, 550, and 730 μm showed equal bending strength. Thus, the adequate channel size for fast regeneration of high-strength bone, oriented to the bone axis, is ≤730 μm. To the best of our knowledge, this is the first study to report the effect of channel size on bone orientation and strength. The findings of this study are relevant to the fast repair of segmental bone defects.

Synthesis and characterization of hydroxyapatite/SiO2/gelatin composites as bone scaffold candidates

This study aims to determine the characteristics of hydroxyapatite/SiO2/gelatin composites to fulfil the bone scaffold standards. XRF analysis showed that limestone has a high CaO content of 92.89%, allowing it be used for hydroxyapatite synthesis. The wet precipitation method was used to synthesize hydroxyapatite; meanwhile, the freeze-drying method was used to synthesize the hydroxyapatite/SiO2/gelatin scaffold. FTIR analysis confirmed the characteristic peaks, which indicated the presence of compounds of hydroxyapatite (OH- and PO43-), SiO2 (Si-OH and Si-O-Si), and gelatin (N-H, C-H, and C=O). XRD analysis showed 98.1% hydroxyapatite phase and 1.9% SiO2 phase and SEM analysis showed a scaffold pore size of 155-218?m, optimal for cell attachment. Furthermore, mechanical testing resulted in a compressive strength of 1.71 MPa and porosity testing resulted in a porosity of 75%. This characterization showed the potential use of hydroxyapatite/SiO2/gelatin composites as bone scaffolds. This research can enable further development of scaffold materials in the field of tissue engineering.

Decellularization Agents on Porosity and Pore Size in Bovine Pericardium Scaffolds for Pediatric Heart Surgery

Background: Tissue engineering in pediatric and congenital heart surgery relies on developing biomaterials with extracellular matrix (ECM)-like properties. The acellular bovine pericardium membrane (BPM) is a promising scaffold due to its strength, low infection rates, and cost-effectiveness. Decellularization is essential to optimize BPM's properties for tissue regeneration. This study investigates the effects of different decellularization methods on BPM's porosity and pore size. Methods: A true experimental design was used to evaluate BPM scaffolds treated with sodium dodecyl sulfate (SDS), hydrogen peroxide (H2O2), or ASB-16, compared to a control group. Porosity and pore size were measured using image analysis software after 4 weeks of incubation. Statistical analysis was performed using the Kruskal-Wallis test, Mann-Whitney U test, and one-way ANOVA. Results: ASB-16 decellularization significantly increased BPM porosity (50.14 ± 3.71%) compared to the control (3.06 ± 0.99%) and other treatments (SDS: 6.23 ± 2.94%, H2O2: 4.47 ± 1.34%). Pore size was also significantly larger in the ASB-16 group (26.9 ± 5.93 µm) compared to SDS (8.99 ± 2.77 µm), H2O2 (3.13 ± 1.00 µm), and control (2.00 ± 0.29 µm). Conclusion: ASB-16 decellularization effectively enhances BPM porosity and pore size, making it a promising method for optimizing scaffolds in tissue engineering applications. Further research should focus on its impact on cell proliferation and tissue regeneration.

Characterization of Blow-Spun Polyurethane Scaffolds-Influence of Fiber Alignment and Fiber Diameter on Pericyte Growth.

In this study, fibrous polyurethane (PU) materials with average fiber diameter of 200, 500, and 1000 nm were produced using a solution blow spinning (SBS) process. The effects of the rotation speed of the collector (in the range of 200-25 000 rpm) on the fiber alignment and diameter were investigated. The results showed that fiber alignment was influenced by the rotation speed of the collector, and such alignment was possible when the fiber diameter was within a specific range. Homogeneously oriented fibers were obtained only for a fiber diameter ≥500 nm. Moreover, the changes in fiber orientation and fiber diameter (resulting from changes in the rotation speed of the collector) were more noticeable for materials with an average fiber diameter of 1000 nm in comparison to 500 nm, which suggests that the larger the fiber diameter, the better the controlled architectures that can be obtained. The porosity of the produced scaffolds was about 65-70%, except for materials with a fiber diameter of 1000 nm and aligned fibers, which had a higher porosity (76%). Thus, the scaffold pore size increased with increasing fiber diameter but decreased with increasing fiber alignment. The mechanical properties of fibrous materials strongly depend on the direction of stretching, whereby the fiber orientation influences the mechanical strength only for materials with a fiber diameter of 1000 nm. Furthermore, the fiber diameter and alignment affected the pericyte growth. Significant differences in cell growth were observed after 7 days of cell culture between materials with a fiber diameter of 1000 nm (cell coverage 96-99%) and those with a fiber diameter of 500 nm (cell coverage 70-90%). By appropriately setting the SBS process parameters, scaffolds can be easily adapted to the cell requirements, which is of great importance in producing complex 3D structures for guided tissue regeneration.

Thickening tissue by thinning electrospun scaffolds for skeletal muscle tissue engineering

AbstractElectrospun scaffolds with aligned fiber orientation are widely used in tissue engineering, such as muscle, heart, nerve, tendon, and cartilage, due to their ability to guide cell morphology and induce cellular functions. However, the dense fibrous structure of the scaffolds poses a critical obstacle to engineering highly cellular and thick 3D tissues, as it prevents cell infiltration. While many techniques have been developed to increase the pore size of electrospun scaffolds and improve cell infiltration/migration, it often leads to a decrease in direct cell‐cell contact, compromising cell differentiation and tissue maturation. This study presents an alternative approach by reducing the thickness of scaffolds to the cellular scale and stacking or rolling the cell‐scaffold complex into 3D constructs. We devise a series of novel tools to fabricate, characterize, and manipulate ultra‐thin electrospun scaffolds, which demonstrate high reproducibility, resolution, and cellularity. Our study provides a solution to the cell infiltration issue in muscle tissue engineering and is highly versatile, and can be applied to various fields that require structures with high‐resolution gradients in a layered pattern or complex spatial distribution in a rolled pattern.

Quantitative Evaluation of the Pore and Window Sizes of Tissue Engineering Scaffolds on Scanning Electron Microscope Images Using Deep Learning.

The morphological characteristics of tissue engineering scaffolds, such as pore and window diameters, are crucial, as they directly impact cell-material interactions, attachment, spreading, infiltration of the cells, degradation rate and the mechanical properties of the scaffolds. Scanning electron microscopy (SEM) is one of the most commonly used techniques for characterizing the microarchitecture of tissue engineering scaffolds due to its advantages, such as being easily accessible and having a short examination time. However, SEM images provide qualitative data that need to be manually measured using software such as ImageJ to quantify the morphological features of the scaffolds. As it is not practical to measure each pore/window in the SEM images as it requires extensive time and effort, only the number of pores/windows is measured and assumed to represent the whole sample, which may cause user bias. Additionally, depending on the number of samples and groups, a study may require measuring thousands of samples and the human error rate may increase. To overcome such problems, in this study, a deep learning model (Pore D2) was developed to quantify the morphological features (such as the pore size and window size) of the open-porous scaffolds automatically for the first time. The developed algorithm was tested on emulsion-templated scaffolds fabricated under different fabrication conditions, such as changing mixing speed, temperature, and surfactant concentration, which resulted in scaffolds with various morphologies. Along with the developed model, blind manual measurements were taken, and the results showed that the developed tool is capable of quantifying pore and window sizes with a high accuracy. Quantifying the morphological features of scaffolds fabricated under different circumstances and controlling these features enable us to engineer tissue engineering scaffolds precisely for specific applications. Pore D2, an open-source software, is available for everyone at the following link: https://github.com/ilaydakaraca/PoreD2.

Development of biodegradable Zn-based porous scaffolds with elaborate triply periodic minimal surface structure via Vat photopolymerization-assisted template replacement strategy

Herein, a novel strategy, namely Vat photopolymerization-assisted template replacement method was developed to achieve elaborate triply periodic minimal surface structure and different pore sizes in biodegradable Zn-based porous scaffolds. The pore structure, microstructure, phase constitution, degradation properties, mechanical performance, in vitro cytocompatibility and antibacterial activity were systematically investigated. As a result, triply periodic minimal surface structures with different pore sizes were successfully obtained in Zn–1Mg porous scaffolds. The actual porosity closely matched the designed porosity, demonstrating the efficacy of the new strategy in achieving precise pore structures with a difference below 2%. Zn–1Mg scaffolds, designed with a pore size of 780 mm, exhibited a uniaxial compressive strength of 59.95 MPa and an elastic modulus of 3.07 GPa. Furthermore, the mechanical integrity was well-maintained even after 28 days of immersion, attributed to the substantial deposition of calcium-phosphate-rich corrosion products within the porous structure. More importantly, a suitable weight loss rate of about 15% were confirmed after 28 days immersion, indicating a period for total degradation of approximately 13 months based on a linear degradation assumption. Further, the experimental scaffolds demonstrated good cytocompatibility with MC3T3-E1 preblast cells and exhibited significant antibacterial activity against both Staphylococcus aureus and Escherichia coli.

Additively-manufactured gradient porous bio-scaffolds: Permeability, cytocompatibility and mechanical properties

The additive manufacturing technology enables the customization of artificial bone scaffolds, especially those with internal gradient porous structures (GS). It is of great significance to study the correlation between parametric design of GS and its properties. In this study, GS scaffolds were obtained by triply periodic minimal surfaces (TPMS) parametric design and fabricated by selective laser sintering. The stress distribution and permeability of GS scaffolds were elucidated by a combination of numerical simulation and experimental testing. Experimental tests indicated that the pore size of GS scaffold is in the range of 570 ∼ 1440 μm, corresponding to the average compressive strength of 3.0 ∼ 9.3 MPa, respectively. The test permeability of GS scaffolds ranged from 1.241 × 10-9 to 2.231 × 10-9 m2, all within the range of human bones (2.56 × 10-11 to 7.43 × 10-8 m2). Moreover, in vitro biomineralization and biological testing of GS scaffolds showed excellent calcium-phosphorus formation induction and biocompatibility. In summary, GS scaffold successfully realizes flexible control of structural parameters, especially GP-type scaffolds with radial gradient porous structures exhibit mechanical properties and permeability comparable to natural bone tissue, and even effectively regulate cell behavior. Therefore, the GS scaffolds proposed in this work is expected to exhibit great application potential in orthopedic implants.

Fabricating biomimetic porous PEEK scaffolds for bone implants

Poly-ether-ether-ketone (PEEK) is a high strength polymer with strong potential for medical use, especially for bone implants. In this research, a novel method of making biomimetic porous PEEK scaffolds is developed. PEEK and polyethersulfone (PES) are blended at a proper ratio to generate a co-continuous phase structure. With solid-state foaming, PES is efficiently removed by leaching to yield interconnected porous PEEK scaffolds. The pore size and pore gradient of the PEEK scaffolds can be easily controlled by controlling the annealing time and temperature of the PEEK/PES blend. This study presents the conditions of the proposed fabrication process and compares the fabricated porous PEEK scaffolds with those fabricated using other methods. It is shown that the structural morphology and mechanical properties of the fabricated porous PEEK is generally comparable to those of trabecular bones, suggesting these scaffolds could be excellent candidates for bone implant applications.

Additively manufactured porous scaffolds by design for treatment of bone defects.

There has been increasing attention to produce porous scaffolds that mimic human bone properties for enhancement of tissue ingrowth, regeneration, and integration. Additive manufacturing (AM) technologies, i.e., three dimensional (3D) printing, have played a substantial role in engineering porous scaffolds for clinical applications owing to their high level of design and fabrication flexibility. To this end, this review article attempts to provide a detailed overview on the main design considerations of porous scaffolds such as permeability, adhesion, vascularisation, and interfacial features and their interplay to affect bone regeneration and osseointegration. Physiology of bone regeneration was initially explained that was followed by analysing the impacts of porosity, pore size, permeability and surface chemistry of porous scaffolds on bone regeneration in defects. Importantly, major 3D printing methods employed for fabrication of porous bone substitutes were also discussed. Advancements of MA technologies have allowed for the production of bone scaffolds with complex geometries in polymers, composites and metals with well-tailored architectural, mechanical, and mass transport features. In this way, a particular attention was devoted to reviewing 3D printed scaffolds with triply periodic minimal surface (TPMS) geometries that mimic the hierarchical structure of human bones. In overall, this review enlighten a design pathway to produce patient-specific 3D-printed bone substitutions with high regeneration and osseointegration capacity for repairing large bone defects.

Simulation and physical validation of metal triply periodic minimal surfaces-based scaffolds for bioengineering applications

Metallic scaffolds are used as implants to help heal bones. Sheet-based Triply Periodic Minimal Surfaces (TPMS) are of interest due to their high surface-to-volume ratio (S/V) and customisable stiffness. They can be realised using Additive Manufacturing (AM). Other studies investigate porosity and pore size of scaffolds, but they frequently overlook S/V, which is critical for cellular response. Additionally, the limitation of AM (esp. Selective Laser Melting (SLM)) resides in the discrepancies between as-designed and as-built physical and mechanical properties of those structures, and this also needs addressing. This work investigates three types of pure Titanium TPMS scaffolds, with an emphasis on as-designed vs as-built discrepancies and the significance of S/V. As-designed scaffolds reported 70-75% porosity and 25-35 cm-1 S/V, and stiffness was measured using finite element analysis (FEA) obtaining 6.7-9.3 GPa. The as-built scaffolds had 59-70% porosity and 33-42 cm-1 S/V. Laboratory compression testing revealed an effective Young's modulus of 5-9 GPa, comparable to bone tissue. Image-based simulation methods were employed on the as-built samples which reported the stiffness range of 8.3-15 GPa, overestimating it by 54%. It is hypothesised that these discrepancies stem from the secondary roughness on the surfaces, cracks and entrapped voids created during the SLM process, causing reduction in porosity, yet not contributing to structure’s strength. The cyber-physical validation methods presented in this work are a good way to quantify these discrepancies, allowing feedback to the design stages for more predictable as-built structures.

Microporous Annealed Particle (MAP) Scaffold Pore Size Influences Mesenchymal Stem Cell Metabolism and Proliferation Without Changing CD73, CD90, and CD105 Expression Over Two Weeks.

Scaffold pore architecture is shown to influence stem cell fate through various avenues. It is demonstrated that microporous annealed particle (MAP) microgel diameter can be tuned to control scaffold pore size and, in turn, modulate mesenchymal stem cell (MSC) survivability, proliferation, metabolism, and migration, thereby enhancing bioactivity and guiding future applications of MAP for regenerative medicine.

Preparation of Highly Porous Scaffolds with Controllable Pore Size from Microbial Polyesters

Microbial polyesters saw limited use in the field of tissue engineering, even though the biocompatibility of these polymers makes them ideal candidates for this role. The primary factor that hinders the proliferation of microbial polyesters in this market is that their processing with conventional techniques, such as electrospinning or 3D printing, is challenging. However, the full potential of these biopolymers could still be utilized by applying unconventional manufacturing methods, such as those based on the concept of salt leaching. An implementation of this concept facilitates the production of scaffolds that simultaneously have high porosity and excellent permeability. Moreover, the average pore size can also be varied in the range from 50 to 400 µm, which was reported to be optimal for the cultivation of eucaryotic cell cultures. By adjusting the pore size, the scaffold can be tailored to the eucaryotic cells the tissue consists of. Furthermore, we have developed an entirely new computational method for the approximation of the pore size distribution of the scaffolds. The method relies on 3D data reconstructed by the software of a digital optical microscope and also facilitates the modeling of the average pore size of scaffolds. Thus, besides the control of the pore size, our method enables its prediction as well.

Influence of structural parameters of 3D-printed triply periodic minimal surface gyroid porous scaffolds on compression performance, cell response, and bone regeneration.

In this study, multi-scale triply periodic minimal surface (TPMS) porous scaffolds with uniform and radial gradient distribution on pore size were printed based on the selective laser melting technology, and the influences of porosity, pore size and radial pore size distribution on compression mechanical properties, cell behavior, and bone regeneration behavior were analyzed. The results showed that the compression performance of the uniform porous scaffolds with high porosity was similar to that of cancellous bone of pig tibia, and the gradient porous scaffolds have higher elastic modulus and compressive toughness. After 4 days of cell culture, cells were distributed on the surface of scaffolds mostly, and the number of adherent cells was higher on the small pore size porous scaffolds; After 7 days, the area and density of cell proliferation on the scaffolds were improved; After 14 days, the cells on the small pore size scaffolds tended to migrate to adjacent pores. Animal implantation experiments showed that collagen fiber osteoid was intermittent on scaffolds with high porosity and large pore size, which was not conducive to bone formation. The appropriate pore size and porosity of bone regeneration were 792 um and 83%, respectively, and the regenerative ability of gradient pore size was better than that of uniform pore size. Our study explains the rules of TPMS gyroid structure parameters on compression performance, cell response and bone regeneration, and provides a reference value for the design of bone repair scaffolds for clinical orthopedics.

Improving pore size of electrospun gelatin scaffolds containing graphene oxide using PEG as a sacrificial agent for bone tissue engineering

In this study, polyethylene glycol (PEG), as a sacrificial agent, and gelatin containing graphene oxide (GO) are co-electrospun to prepare scaffolds. Based on pore size measurements, removal of PEG leads to an increase in the pore size of modified scaffolds, resulting in easier infiltration. Moreover, noticeable elastic modulus of GO increased the mechanical strength. Alizarin red staining indicated proliferation and differentiation of human bone marrow-derived mesenchymal stem cells seeded on the modified scaffolds. Thus, gelatin scaffold containing 0.5% GO with 20% PEG at the ratio of 80:20 for gelatin–PEG was selected as the optimal scaffold for bone tissue engineering approaches.

Regeneration of Mechanically Enhanced Tissue-Engineered Cartilage Based on the Decalcified Bone Matrix Framework.

Human decalcified bone matrix (HDBM) is a framework with a porous structure and good biocompatibility. Nevertheless, its oversized pores lead to massive cell loss when seeding chondrocytes directly over it. Gelatin (GT) is a type of protein obtained by partial hydrolysis of collagen. The GT scaffold can be prepared from the GT solution through freeze-drying. More importantly, the pore size of the GT scaffold can be controlled by optimizing the concentration of the GT solution. Similarly, when different concentrations of gelatin are combined with HDBM and then freeze-dried, the pore size of the HDBM can be modified to different degrees. In this study, the HDBM framework was modified with 0.3, 0.6, and 0.9%GT, resulting in an improved pore size and adhesion rate. Results showed that the HDBM framework with 0.6%GT (HDBM-0.6%GT) had an average pore size of 200 μm, which was more suitable for chondrocyte seeding. Additionally, our study validated that porcine decalcified bone matrix (PDBM) had a proper pore structure. Chondrocytes were in vitro seeded on the three frameworks for 4 weeks and then implanted in nude mice and autologous goats, respectively. The in vivo cartilage regeneration results showed that HDBM-0.6%GT and PDBM frameworks compensated for the oversized pores of the HDBM framework. Moreover, they showed successfully regenerated more mature cartilage tissue with a certain shape in animals.

Regenerative Engineering of a Biphasic Patient-Fitted Temporomandibular Joint Condylar Prosthesis.

Regenerative medicine approaches to restore the mandibular condyle of the temporomandibular joint (TMJ) may fill an unmet patient need. In this study, a method to implant an acellular regenerative TMJ prosthesis was developed for orthotopic implantation in a pilot goat study. The scaffold incorporated a porous, polycaprolactone-hydroxyapatite (PCL-HAp, 20wt% HAp) 3D printed condyle with a cartilage-matrix-containing hydrogel. A series of material characterizations was used to determine the structure, fluid transport, and mechanical properties of 3D printed PCL-HAp. To promote marrow uptake for cell seeding, a scaffold pore size of 152 ± 68 μm resulted in a whole blood transport initial velocity of 3.7 ± 1.2 mm·s-1 transported to the full 1 cm height. The Young's modulus of PCL was increased by 67% with the addition of HAp, resulting in a stiffness of 269 ± 20 MPa for etched PCL-HAp. In addition, the bending modulus increased by 2.06-fold with the addition of HAp to 470 MPa for PCL-HAp. The prosthesis design with an integrated hydrogel was compared with unoperated contralateral control and no-hydrogel group in a goat model for 6 months. A guide was used to make the condylectomy cut, and the TMJ disc was preserved. MicroCT assessment of bone suggested variable tissue responses with some regions of bone growth and loss, although more loss may have been exhibited by the hydrogel group than the no-hydrogel group. A benchtop load transmission test suggested that the prosthesis was not shielding load to the underlying bone. Although variable, signs of neocartilage formation were exhibited by Alcian blue and collagen II staining on the anterior, functional surface of the condyle. Overall, this study demonstrated signs of functional TMJ restoration with an acellular prosthesis. There were apparent limitations to continuous, reproducible bone formation, and stratified zonal cartilage regeneration. Future work may refine the prosthesis design for a regenerative TMJ prosthesis amenable to clinical translation.

Improving osteoinduction and osteogenesis of Ti6Al4V alloy porous scaffold by regulating the pore structure.

Titanium alloy scaffolds with a porous structure have attracted much attention in bone defect repair. However, which pore structure is more beneficial to bone defect repair is controversial. In the present research, the Ti6Al4V alloy porous scaffolds with gradient pore sizes were designed and fabricated. The microstructure characterization, tests of mechanical properties, and in vitro and in vivo experiments have been performed to systematically evaluate the effect of pore size on osteoinduction and osteogenesis. The results revealed that the contact angle with water, compressive strength, and elastic modulus of the Ti6Al4V alloy porous scaffolds decreased gradually with the increase of pore size. However, there were obvious drops when the pore size of the porous scaffold was around 600μm. As the pore size increased, the proliferation and integrin β1 of RAW 264.7 macrophages seeded on Ti6Al4V alloy porous scaffolds increased at first, reaching a maximum value at a pore size of around 600μm, and then decreased subsequently. The proliferation, integrin β1, and osteogenic gene-related expressions of Bone marrow mesenchymal stem cells (BMSCs) seeded on Ti6Al4V alloy porous scaffolds with different pore sizes all exhibited similar variations which rose with increased pore size firstly, obtaining the maximum value at pore size about 600μm, and then declined. The in vivo experiments confirmed the in vitro results, and the Ti6Al4V alloy porous scaffold with a pore size of 600μm possessed the better capability to induce new bone formation. Therefore, for the design of Ti6Al4V alloy with a regular porous scaffold, the surface morphology, porosity, strength, and elastic modulus should be considered systematically, which would determine the capability of osteoinduction and osteogenesis.

Pore size-mediated macrophage M1 to M2 transition affects osseointegration of 3D-printed PEEK scaffolds.

Increasing evidence indicates that macrophages play an important role in angiogenesis and bone regeneration. Because the phenotypic polarization of macrophage is extremely sensitive to the pore size of materials, poly(ether-ether-ketone) (PEEK) scaffolds with pore sizes of 0, 200, and 400 μm were prepared, and the influence of pore size-mediated macrophage polarization on subsequent angiogenesis and osteogenesis was examined. The interaction results of macrophages and scaffolds indicated that macrophages were responsive to the pore size of three-dimensional (3D)-printed PEEK scaffolds, and large pore size scaffolds showed greater potential in inducing M1 to M2 transition of macrophage and enhanced macrophage secretion of high concentrations of osteogenesis-related and angiogenesis-related cytokines. When human umbilical vein endothelial cells (HUVECs) and bone marrow mesenchymal stem cells (BMSCs) were cultured in the conditioned medium derived from co-culture of macrophages and scaffolds, HUVECs showed good angiogenic responses in terms of cell migration and angiogenic gene expression, while BMSCs showed good osteogenic differentiation effect in in vitro mineralization and osteogenesis-related gene expression. The results of bone defect repair showed that the bone volume/total volume ratio and trabecular thickness of the large pore size PEEK scaffold were significantly higher, and it had better biomechanical properties and achieved a better osseointegration effect. Our data demonstrate that large-pore PEEK scaffolds promote angiogenesis and osteogenic differentiation in vitro and osseointegration in vivo, most likely because scaffolds with larger pore size are able to mediate a higher degree of M1 to M2 transition in macrophages.