Scaffold Walls Research Articles

Numerical analysis of scaffold degradation in cryogenic environment: impact of cell migration and cell apoptosis

The analysis of degradation in the presence of cell death and migration is a critical aspect of research in various biological fields, such as tissue engineering, regenerative medicine, and disease pathology. In present study, numerical study of degradation of scaffold were performed in present of cells, cell apoptosis and cell migration. A poly electrolyte complex (PEC) silk fibroin scaffold was used for degradation study. Degradation study in the presence of cells and migration were performed at fixed pH concentration 7.2. Similarly, degradation study of scaffold were performed at different pH cell apoptosis. A transient analysis of scaffold was evaluated in COMSOL 5.5 in presence of cryogenic temperature at different temperature gradient. The parameters; temperature, stress, strain tensor and deformation gradient associated with the degradation of polyelectrolyte complex scaffold were evaluated. Result shows that in both geometries minimum temperature had been achieved as 230.051 K at point P4 in series view and parallel view and at a point P3 for cell migration study for −5 k min−1 and −1 k min−1, respectively. The maximum stress had been generated for 5.57 × 107 N m−2 for the temperature gradient of −2 K min−1 at T cycle in the case of cell migration study. In contrast in series view the maximum stress 2.9 × 107 N m−2 were observed at P4 which was higher as compare to P3. Similarly, for a parallel view, maximum stress (3.93 × 107 N m−2) was obtained for point P3. It had been observed that the maximum strain tensor 5.21 × 10−3, 5.15 × 10−3 and 5.26 × 10−3 was generated in series view at 230 k on a point P3 for − 1, −2 and −5 K min−1, respectively. Similarly, the maximum strain tensor 8.16 × 10−3, 8.09 × 10−3 and 8.09 × 10−3 was generated in parallel view at 230 k on a point P3 for −1, −2 and −5 K min−1, respectively. In the presence of cells, at a point P4 for temperature gradient of −1 and −2 K min−1, it had been closed to the scaffold wall, which had a different temperature profile than the point P3 and scaffold comes to the contact with the cells. The analysis of PEC scaffold degradation in the presence of cells, including cell apoptosis and migration, offers significant insights into the relationship between scaffold properties, cell behaviour, and tissue regeneration.

Three-Dimensional Printing of Drug-Eluting Implantable PLGA Scaffolds for Bone Regeneration.

Despite rapid progress in tissue engineering, the repair and regeneration of bone defects remains challenging, especially for non-homogenous and complicated defects. We have developed and characterized biodegradable drug-eluting scaffolds for bone regeneration utilizing direct powder extrusion-based three-dimensional (3D) printing techniques. The PLGA scaffolds were fabricated using poly (lactic-co-glycolic acid) (PLGA) with inherent viscosities of 0.2 dl/g and 0.4 dl/g and ketoprofen. The effect of parameters such as the infill, geometry, and wall thickness of the drug carrier on the release kinetics of ketoprofen was studied. The release studies revealed that infill density significantly impacts the release performance, where 10% infill showed faster and almost complete release of the drug, whereas 50% infill demonstrated a sustained release. The Korsmeyer-Peppas model showed the best fit for release data irrespective of the PLGA molecular weight and infill density. It was demonstrated that printing parameters such as infill density, scaffold wall thickness, and geometry played an important role in controlling the release and, therefore, in designing customized drug-eluting scaffolds for bone regeneration.

A Combined Computational and Experimental Analysis of PLA and PCL Hybrid Nanocomposites 3D Printed Scaffolds for Bone Regeneration.

A combined computational and experimental study of 3D-printed scaffolds made from hybrid nanocomposite materials for potential applications in bone tissue engineering is presented. Polycaprolactone (PCL) and polylactic acid (PLA), enhanced with chitosan (CS) and multiwalled carbon nanotubes (MWCNTs), were investigated in respect of their mechanical characteristics and responses in fluidic environments. A novel scaffold geometry was designed, considering the requirements of cellular proliferation and mechanical properties. Specimens with the same dimensions and porosity of 45% were studied to fully describe and understand the yielding behavior. Mechanical testing indicated higher apparent moduli in the PLA-based scaffolds, while compressive strength decreased with CS/MWCNTs reinforcement due to nanoscale challenges in 3D printing. Mechanical modeling revealed lower stresses in the PLA scaffolds, attributed to the molecular mass of the filler. Despite modeling challenges, adjustments improved simulation accuracy, aligning well with experimental values. Material and reinforcement choices significantly influenced responses to mechanical loads, emphasizing optimal structural robustness. Computational fluid dynamics emphasized the significance of scaffold permeability and wall shear stress in influencing bone tissue growth. For an inlet velocity of 0.1 mm/s, the permeability value was estimated at 4.41 × 10-9 m2, which is in the acceptable range close to human natural bone permeability. The average wall shear stress (WSS) value that indicates the mechanical stimuli produced by cells was calculated to be 2.48 mPa, which is within the range of the reported literature values for promoting a higher proliferation rate and improving osteogenic differentiation. Overall, a holistic approach was utilized to achieve a delicate balance between structural robustness and optimal fluidic conditions, in order to enhance the overall performance of scaffolds in tissue engineering applications.

Enhanced Cell Penetration and Pluripotency Maintenance of hiPSCs in 3D Natural Chitosan Scaffolds.

Human induced pluripotent stem cells (hiPSCs) cultured in three-dimensional (3D) matrices hold great promise in disease modeling, drug discovery and tissue regeneration. Uniform cell distribution in a 3D structure is critical to the growth and function of hiPSCs, yet cell seeding in 3D matrices often remains superficial, leading to limited cell proliferation and compromised pluripotency. Here, we report an approach to improve cell penetration depth of hiPSCs in 3D scaffolds modified with hiPSCs conditioned medium (CM). We showed that extra-cellular matrix (ECM) components were successfully deposited onto the scaffold wall surface after CM treatment and promoted homogeneous cell adhesion during initial seeding. Compared to plain, unmodified scaffolds, the CM treated scaffold improved spatial cell distribution uniformity and upregulated pluripotency markers. Notably, the expression of 29 genes associated with 11 signaling pathways participated in the pluripotency maintenance of hiPSCs exhibited > 2-fold change in hiPSCs grown in the CM treated scaffolds than 2D counterparts, demonstrating that CM treated scaffolds can support a more primitive and undifferentiated phenotype of hiPSCs. This study introduced a simple and effective method to enhance cell penetration and maintain cell pluripotency in 3D matrices. This article is protected by copyright. All rights reserved.

Effect of nozzle diameter and cross-linking on the micro-structure, compressive and biodegradation properties of 3D printed gelatin/collagen/hydroxyapatite hydrogel

Since the existing polymeric hydrogel inks lack printability, shape fidelity and the desired mechanical properties for bone tissue regeneration, a hydrogel comprised of gelatin (G), collagen (C), and hydroxyapatite (H) nanoparticles is utilized for extrusion-based 3D printing. The rheological characterization of the composite GCH inks was performed to evaluate their printability, while the cuboid column model scaffolds were printed at a printing speed of 8 mm/s by using different needle inner diameters (500 μm/21G, 250 μm/25G, and 200 μm/27G), followed by carbodiimide induced crosslinking for 12 or 24 h. The samples were tested for their micro-structure, swelling, compression and stiffness performance, before and after incubation in an HBSS solution for up to 14 days. The wall diameter of a 3D printed scaffold decreases and pore size increases primarily with the decreasing inner diameter of the nozzles, and secondarily by increasing the crosslinking time. This was supported with their swelling capacity and the creation of new CaP crystals on the scaffold walls' top surfaces by the time of incubation, necessary for cells’ adhesion, proliferation and growth.The compressive modulus and stiffness of the scaffolds increases proportionally with the increase of their wall diameter and the time of crosslinking, and is inversely proportional to their pores size. The scaffold with the smaller pores provides superior modulus and stiffness, even after 14 days of incubation in the physiological solution (i.e. from ∼0.94 to ∼0.71 MPa and from 17 to 20 kPa to 5–9 kPa, respectively). This is comparative with the reported values for gelatin-based composites, and in the range for hard tissue regeneration at non-load bearing sites, as well as cartilage applications.

A Foam‐Expansion and Wall‐Evolution Model for Scaffold Fabrication Using Supercritical CO2 Foaming

AbstractSupercritical CO2 foaming (SCF) is a green and highly controllable technique to fabricate polymer scaffolds. In the current work, SCF was modeled mathematically by combining a foam‐expansion model (FEM) and a wall‐evolution model (WEM). The model package is clearly presented, its solution strategy is precisely described, and its superiority over FEM is demonstrated. The model was validated by using experimental data of poly(ε‐caprolactone) scaffolds fabricated by the SCF technique at 300 bar and 50 °C with first and second pressure releases of 28.6 and 200 bar min−1, respectively. It was revealed that coupling FEM and WEM enables the prediction of scaffold density, pore radius, pore geometry, and wall thickness at the same time.

270 Neonipple Formation After Implantation Of Acellular Ovine Xenograft

OBJECTIVES/GOALS: To determine if decellularized costal cartilage (DCC), which could theoretically be obtained “off the shelf,” would provide similar results to autologous cartilage grafts previously studied in this lab, thereby widening the application of our novel nipple engineering approach to all patients undergoing nipple reconstruction. METHODS/STUDY POPULATION: PLA scaffolds (diameter: 1.0 cm, height: 1.0 cm) were printed using a PRUSA 3D printer and sterilized. Lamb costal cartilage was minced (1 mm3) or zested (<0.2 mm3) and then decellularized. The quality of decellularization was assessed using DNA quantification and histological analysis. DCC was then packed into PLA scaffolds and implanted subcutaneously into immunocompetent Sprague Dawley rats using a CV flap technique. The constructs were explanted and evaluated up to 6 months after implantation. RESULTS/ANTICIPATED RESULTS: All nipple reconstructions showed well-preserved diameter and projection due to persistence of the external scaffolds at 1, 3, and 6 months. Mass and volume of engineered tissue was well-preserved over all timepoints. Compared to implantation values, engineered zested nipples demonstrated a 12% mass increase and a 22% volume increase at 6 months. Minced nipples illustrated a similar mass and volume gain with a 21% increase in mass and a 13% increase in volume at 6 months secondary to infiltration of fibrovascular tissue and growth through scaffold wall pores, respectively. Histologic analysis demonstrated a mild inflammatory infiltrate 1 month after implantation which was replaced by fibrovascular tissue by 3 months that remained stable through 6 months. The processed DCC structure remained unchanged over time. DISCUSSION/SIGNIFICANCE: Using acellular ovine xenograft within bioabsorbable scaffolds, we have engineered neonipples that maintain their volume for at least 6 months. DCC architecture is well-preserved with minimal evidence of immune-mediated degradation. By using DCC, this novel approach to nipple engineering may be applied to any patient requiring reconstruction.

Near-field electrospinning of polydioxanone small diameter vascular graft scaffolds

The ideal “off the shelf” tissue engineering, small-diameter (SD) vascular graft hinges on designing a scaffold to act as a template that facilitates transmural ingrowth of capillaries to regenerate an endothelized neointimal surface. Towards this goal, we explored two types of near-field electrospun (NFES) polydioxanone (PDO) architectures, as SD vascular graft scaffolds. The first architecture type consisted of a 200 × 200 μm and 500 × 500 μm grid geometry with random fiber infill, while the second architecture consisted of aligned fibers written in a 45°/45° and 20°/70° offset from the long axis written, both on a 4 mm diameter cylindrical mandrel. These vascular graft scaffolds were evaluated for their effective pore size, mechanical properties, and platelet-material interactions compared to traditionally electrospun (TES) scaffolds and Gore-Tex® vascular grafts. It was found that effective pore size, given by 9.9 and 97 μm microsphere filtration through the scaffold wall for NFES scaffolds, was significantly more permeable compared to TES scaffolds and Gore-Tex® vascular grafts. Furthermore, ultimate tensile strength, percent elongation, suture retention, burst pressure, and Young's modulus were all tailorable compared to TES scaffold characterization. Lastly, platelet adhesion was attenuated on NFES scaffolds compared to TES scaffold which approximates the low level of platelet adhesion measured on Gore-Tex®, with all samples showing minimal platelet activation given by P-selectin surface expression. Together, these results suggest a highly tailorable process for the creation of the next generation of small-diameter vascular grafts.

Smart Device for Biologically Enhanced Functional Regeneration of Osteo-Tendon Interface.

The spontaneous healing of a tendon laceration results in the formation of scar tissue, which has lower functionality than the original tissue. Moreover, chronic non-healing tendon injuries frequently require surgical treatment. Several types of scaffolds have been developed using the tissue engineering approach, to complement surgical procedures and to enhance the healing process at the injured site. In this work, an electrospun hybrid tubular scaffold was designed to mimic tissue fibrous arrangement and extracellular matrix (ECM) composition, and to be extemporaneously loaded into the inner cavity with human platelet lysate (PL), with the aim of leading to complete post-surgery functional regeneration of the tissue for functional regeneration of the osteo–tendon interface. For this purpose, pullulan (P)/chitosan (CH) based polymer solutions were enriched with hydroxyapatite nanoparticles (HP) and electrospun. The nanofibers were collected vertically along the length of the scaffold to mimic the fascicle direction of the tendon tissue. The scaffold obtained showed tendon-like mechanical performance, depending on HP content and tube size. The PL proteins were able to cross the scaffold wall, and in vitro studies have demonstrated that tenocytes and osteoblasts are able to adhere to and proliferate onto the scaffold in the presence of PL; moreover, they were also able to produce either collagen or sialoproteins, respectively—important components of ECM. These results suggest that HP and PL have a synergic effect, endorsing PL-loaded HP-doped aligned tubular scaffolds as an effective strategy to support new tissue formation in tendon-to-bone interface regeneration.

Identifying structure-property relationships of micro-architectured porous scaffolds through 3D printing and finite element analysis

This study integrates 3D printing and finite element analysis (FEA) to investigate the effect of micro-architectural characteristics on the mechanical properties of porous scaffolds. The studied characteristics include the thickness of the scaffold walls and the number of domains at the cross-section. We use 3D printing to fabricate scaffolds of deliberately designed microstructures to enable strict architecture control of the scaffolds. The longitudinal compressive properties of different scaffolds are first analyzed through experimental testing. Then, FEA is conducted to investigate the mechanical properties and the deformation mechanisms of the scaffolds. We find that decreasing wall thickness leads to failure mechanism transition from wall compression failure to buckling instability. For scaffolds with different wall thicknesses, the failure mechanisms and the critical loads are evaluated using the theory of thin plate buckling. For the characteristic of the number of domains, both experimental and FEA results show increasing effective stiffness with increasing domains. Interestingly, we find that with the material properties extracted from a single wall scaffold, the computational models tend to overestimate the effective compression modulus of scaffolds with larger numbers of walls or domains than the experimental data. This observation indicates possible size-dependent material properties in 3D printed structs. Our study demonstrates that integrating experiments and computational modeling can provide fundamental insights into the mechanical properties and deformation mechanisms of micro-architectured scaffolds and unveil unique small-scale material behaviors.

Porous Architecture Evaluation of Silk Fibroin Scaffold from Direct Dissolution Salt Leaching Method

AbstractTissue engineering scaffold is used to facilitate and support cell/tissue growth. Fabrication of silk fibroin scaffold using newly developed direct dissolution salt leaching method is successfully done. This method significantly reduces the processing time compared to the traditional method. Cells attachment, cells growth, cells migration, and diffusion of nutrients and waste are affected by the architecture scaffold. In this study, 3D analysis on porous architecture evaluation of direct dissolution salt leaching scaffolds is conducted. Scaffolds are fabricated from different NaCl particle sizes of 158, 250, 378, and 503 μm at 12% w/v silk fibroin concentration. Scaffold architecture is evaluated using microcomputed tomography (micro‐CT) method. Evaluation of scaffold architecture shows that the use of larger NaCl particle size increases the scaffold pore size. The relationship between scaffold pore size and scaffold porosity, scaffold wall thickness, pore interconnectivity, scaffold specific surface area is established, which is important for tissue formation.

Influence of Mesenchymal Stem Cells Seeding on Morphology of Tissue-Engineered Vascular Graft Based on Poly (L-lactide) Scaffold

Introduction - The problem of small-diameter vascular grafts still exists in modern vascular surgery. Autologous or synthetic vascular grafts are used routinely for arterial bypass in patients with cardiovascular diseases. However, some patients either lack suitable autologous tissue or cannot receive synthetic grafts. Such patients could benefit from a vascular graft produced by tissue engineering. The aim of the study is to evaluate the effects of adipose-derived mesenchymal stem cells (AD-MSC) on the formation of tissue-engineered vascular graft (TEVG). Methods - Tubular scaffolds 1.1 mm inner diameter were obtained by the electrospinning method on the basis of nano- and microfibers of poly(L-lactide) (PLLA). AD-MSC were seeded on the scaffolds by the developed filtration method. The subsequent culturing for 14 days was carried out in the constructed flow bioreactor. Cell distribution in the scaffold wall was assessed by the fluorescence microscopy. Obtained grafts were implanted into rat aorta: group 1 without AD-MSC (n=36) with follow-up till 16 months, group 2 with seeded AD-MSC (n=36) with follow-up till 16 months. The material was subjected to histological examination, electron microscopy, immunohistochemistry CD 31+, aSMA and morphometric analysis (cell counting, neointima and neoadventia thickness). To track AD-MSC in vivo PKH-26 labeling and subsequent fluorescence microscopy were performed in 2, 7 and 14 days. Results - Filtration seeding and subsequent cultivation in the flow bioreactor led to a uniform distribution of AD-MSC in the scaffold wall. Graft patency in the first group was 86%, in the second 96%. All grafts formed neointima, with no signs of hyperplasia in the area of anastomoses. The total resorption of PLLA fibers in group 1 was observed by histological examination, new vascular wall consisted of endothelial lining and connective tissue without smooth muscle cells (SMC); in all cases aneurysm formation was detected. Total cells number of implant wall was more in group 2, including SMC that formed neomedia. Also the outer connective tissue layer was much thicker. Histology identified the uniform formation of new tissues in group 2 with no signs of aneurysm. Conclusion - AD-MSC seeding leads to the formation of TEVG, morphologically similar to the natural structure of the vessels. The study was supported by Russian Science Foundation (project 14-33-00003)

In situ preparation of hierarchically porous β-tricalcium phosphate bioceramic scaffolds by the sol-gel method combined with F127

A hierarchically porous β-tricalcium phosphate (β-TCP) bioceramic scaffold was prepared by in situ foaming using the sol-gel method, and a nonionic surfactant Pluronic F127 (EO99PO65EO99) was used as the template. The average size of the connecting macropores in the scaffolds increases in the range of 200–500 μm as the amount of the surfactant F127 decreases. The size of micropores on the scaffold wall is between 0.5 and 5 μm, and the microporosity reduces with an increase in the sintering temperature. In addition, the morphology of grains is rough and contains 3-10-nm nanopores and nanoscale “groove” pores due to the removal of F127 as a “soft templating” material. Finally, immersion experiments with simulated body fluids (SBF) in vitro showed that the scaffold had good bioactivity. The hierarchically porous β-TCP bioceramic prepared by this method has the advantages of low cost and a simple process; thus, this material is ideal for repairing bone defects in orthopaedics.

Micromechanical Measurements and Biocompatibility of the High Porosity Ti Scaffold Made with Saccharose as a Space Holder

The paper presents mechanical properties of the porous Ti scaffold made with saccharose as a space holder. The Ti scaffolds had the porosity of 50, 60 and 70% and were made using 100 and 325 mesh Ti as a scaffold material. The pores were established using saccharose spherical space holder particles of 0.7–0.9 mm in diameter. The local mechanical properties of the Ti scaffold have been measured using nanoindenter. Several loading-unloading characteristics of the thin scaffold walls in the microscale have been measured. It has been observed that Ti scaffolds have very high mechanical properties measured in the microscale that are correlated with partial scaffold oxidation and a formation of TiO2, which took place during the production stages. The scaffold is composed mainly of Ti oxide and the structure has been identified by XRD as well as XPS. The highest mechanical properties have scaffolds composed of 100 mesh Ti particles, compared to 325 mesh Ti. The microscale tests measurements are rather slightly affected by the pore presence and are under influence of Ti particles. The MTT test shows slightly higher proliferation of NHost cells on porous Ti scaffold in comparison to the reference Ti sample.

Gel casting of β-TCP scaffolds: Effects of foaming time and polymer coating

Three-dimensional interconnected porous structure and ideal mechanical strength are essential for biological scaffold for bone tissue engineering application. However, ceramic scaffold is very brittle and exhibit low strength. The main aim of this study is to investigate the effect of foaming time on the microstructure and mechanical properties of porous beta tricalcium phosphate (β-TCP) scaffold. The effect of polymer coating on the β-TCP scaffold was also investigated. Porous β-TCP scaffolds were fabricated using the gel casting method by varying the foaming time (60s and 90s) followed by sintering at 1100°C. Porous β-TCP scaffold was coated with polymer coating by using dipping method. Results indicate that increased foaming time results in higher porosity and lower compression strength. It is observed that polymer coating improved around 116% compressive strength in comparison to that of uncoated scaffold. Fourier transform infrared (FTIR) confirm the presence of gelatin on scaffold walls. Based on the morphology observed by scanning electron microscope (SEM), it is found that the scaffold fabricated by gel casting method showed open pores characteristic.

Computational Fluid Dynamics Study of the Effects of Surface Roughness on Permeability and Fluid Flow-Induced Wall Shear Stress in Scaffolds.

In this work, we investigated surface roughness effects on bone scaffold permeability and fluid flow-induced wall shear stress (WSS) using computational fluid dynamics (CFD) analysis. Scaffolds are made of interconnected microchannels, whose fluid flow can be examined from the perspective of fluid flow dynamics. Given that the roughness of microchannel surfaces serves a non-negligible function in the fluid dynamics within the channels, it is believed that the wall roughness of scaffolds can play an important role in their permeability and WSS. Given the criticality of permeability and WSS in the effective biological functioning of scaffolds, we investigated manufacturing-induced surface roughness effects on the two aforementioned biocompatibility characteristics. To this end, three scaffolds with square pores of different sizes (300, 600, and 900µm) and identical porosity (63%) were designed. Six roughness levels (0, 4, 8, 12, 16, and 20µm) were established for the scaffold walls, thus enabling us to develop 18 scaffold models. The pressure drop and WSS in the scaffolds were then measured by CFD. Scaffold permeability was calculated using Darcy's law, with reference to geometrical parameters and the pressure drop derived from the CFD analysis. In all the scaffolds, high roughness decreased permeability and WSS. A significant difference in WSS reduction was found between the models with smooth scaffolds and the models with scaffolds that had a roughness of 20µm. Except for the scaffold with a pore size of 300µm, all the others showed no considerable change in permeability at different roughness levels.

Improving Sorbents for Glycerol Capture in Biodiesel Refinement.

Biodiesel is produced by transesterification of animal fat, vegetable oil, or waste cooking oil with alcohol. After production costs, the economic viability of biodiesel is dependent on what steps are necessary to remove impurities following synthesis and the effectiveness of quality control analysis. Solid-phase extraction offers a potentially advantageous approach in biodiesel processing applications. Nanoporous scaffolds were investigated for adsorption of glycerol, a side product of biodiesel synthesis that is detrimental to engine combustion when present. Materials were synthesized with varying pore wall composition, including ethane and diethylbenzene bridging groups, and sulfonated to promote hydrogen bonding interactions with glycerol. Materials bearing sulfonate groups throughout the scaffold walls as well as those post-synthetically grafted onto the surfaces show notably superior performance for uptake of glycerol. The sorbents are effective when used in biodiesel mixtures, removing greater than 90% of glycerol from a biodiesel preparation.

Mechanosensation across borders: fibroblasts inside a macroporous scaffold sense and respond to the mechanical environment beyond the scaffold walls.

In tissue defects, cells face distinct mechanical boundary conditions, but how this influences early stages of tissue regeneration remains largely unknown. Biomaterials are used to fill defects but also to provide specific mechanical or geometrical signals. However, they might at the same time shield mechanical information from surrounding tissues that is relevant for tissue functionalisation. This study investigated how fibroblasts in a soft macroporous biomaterial scaffold respond to distinct mechanical environments while they form microtissues. Different boundary stiffnesses counteracting scaffold contraction were provided via a newly developed in vitro setup. Online monitoring over 14days revealed 3.0 times lower microtissue contraction but 1.6 times higher contraction force for high vs. low stiffness. This difference was significant already after 48h, a very early stage of microtissue growth. The microtissue's mechanical and geometrical adaptation indicated a collective cellular behaviour and mechanical communication across scaffold pore walls. Surprisingly, the stiffness of the environment influenced cell behaviour even inside macroporous scaffolds where direct cell-cell contacts are hindered. Mechanical communication between cells via traction forces is essential for tissue adaptation to the environment and should not be blocked by rigid biomaterials. Copyright © 2017 John Wiley & Sons, Ltd.

Electrophoretic deposition of spray-dried Sr-containing mesoporous bioactive glass spheres on glass–ceramic scaffolds for bone tissue regeneration

The development of strong and bioactive scaffolds with a trabecular architecture mimicking that of cancellous bone is one of the major and still partially unmet challenges of modern biomaterials science and regenerative medicine. In this work, we exploited the electrophoretic process to deposit highly bioactive particles of mesoporous glass on the struts of a mechanically strong but almost inert glass–ceramic scaffold produced by the sponge replica method. A SiO2–CaO–SrO mesoporous glass was innovatively synthesized by aerosol-assisted spray drying in order to obtain spherical particles with high control over shape and morphology. The glass microspheres underwent morphological, chemical and textural characterizations, and the release kinetics of strontium—known for its ability to stimulate new bone formation in osteoporotic bone—were assessed upon immersion in simulated body fluid. Sr-containing mesoporous glass particles electrophoretically deposited on the scaffold walls retained a fast apatite-forming ability and formed a highly bioactive coating on the macroporous substrate without occluding the pores. The meso-macroporous hierarchical constructs produced in this research could be proposed as bioactive and mechanically strong implants for potential applications in bone tissue engineering.

Porous crosslinked polycaprolactone hydroxyapatite networks for bone tissue engineering.

In this study, porous scaffolds were produced by a thermal crosslinking of polycaprolactone diacrylate in the presence of hydroxyapatite (HA) and particulate leaching technique with sodium chloride as the water soluble porogen for bone tissue engineering applications. The prepared scaffolds were characterized using techniques such as Field Emission Scanning Electron Microscopy, Differential Scanning Calorimetry, and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy. Moreover, dynamic mechanical properties were investigated using Dynamic Mechanical Thermal Analysis. The obtained scaffolds present a porous structure with interconnected pores and porosity around 73%. It was found that the incorporation of HA particles to polycaprolactone (PCL) matrix resulted in an increased crystallinity. Moreover, both the storage modulus (E') and glass transition temperature (Tg) increased, while the loss factor (tan δ) decreased due to the hindrance of the HA particles to the mobility of polymer segments. Cytocompatability of the scaffolds was assessed by MTT assay and cell attachment studies. Osteoconductivity of the scaffolds was investigated with cells alkaline phosphatase extraction. The levels of alkaline phosphatase activity were found to be higher for PCL/HA network scaffold than for PCL network scaffold. In addition, cytocompatibility of the PCL/HA network scaffold indicated no toxicity, and cells were attached and spread to the scaffold walls.