Bone Tissue Engineering: 3D PCL-based Nanocomposite Scaffolds with Tailored Properties

Fabrication and Evaluation of PCL/PLGA/β-TCP Spiral-Structured Scaffolds for Bone Tissue Engineering

Natural bone is a complex material that has been carefully designed. To prepare a successful bone substitute, two challenging conditions need to be met: biocompatible and bioactive materials for cell proliferation and differentiation, and appropriate mechanical stability after implantation. Therefore, a hybrid Poly ε-caprolactone/Poly(lactic-co-glycolide)/β-tricalcium phosphate (PCL/PLGA/β-TCP) scaffold has been introduced as a suitable composition that satisfies the above two conditions. The blended PCL and PLGA can improve the scaffold's mechanical properties and biocompatibility compared to single PCL or PLGA scaffolds. In addition, the incorporated β-TCP increases the mechanical strength and osteogenic potential of PCL/PLGA scaffolds, while the polymer improves the mechanical stability of ceramic scaffolds. The PCL/PLGA/β-TCP scaffold is designed using spiral structures to provide a much better transport system through the gaps between spiral walls than conventional cylindrical scaffolds. Human fetal osteoblasts (hFOBs) were cultured on spiral PCL/PLGA/β-TCP (PPBS), cylindrical PCL/PLGA/β-TCP (PPBC), and cylindrical PCL scaffolds for a total of 28 days. The cell proliferation, viability, and osteogenic differentiation capabilities were analyzed. Compared with PCL and PPBC scaffolds, the PPBS scaffold exhibits great biocompatibility and potential to stimulate cell proliferation and differentiation and, therefore, can serve as a bone substitute for bone tissue regeneration.

An integrated design strategy coupling additive manufacturing and matrix-assisted pulsed laser evaporation (MAPLE) towards the development of a new concept 3D scaffold with improved properties for tissue regeneration

Bioinspired strategies for scaffold design and optimization were improved by the introduction of Additive Manufacturing (AM), thus allowing for replicating and reproducing complex shapes and structures in a reliable manner, adopting different kinds of polymeric and nanocomposite materials properly combined according to the features of the natural host tissues. Benefiting from recent findings in AM, a Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was employed for obtaining graphene-like material (GL) uniform coatings on 3D scaffolds for tissue repair strategies, towards the development of a new concept 3D scaffold with controlled morphological/architectural and surface features and mechanical and biological properties. The effect of the material-design combination through an integrated technological approach (i.e., MAPLE deposition of GL on 3D AM PCL scaffolds) was assessed through scanning electron microscopy, atomic force microscopy, contact angle measurements, mechanical measurements and biological analyses (cell viability assay and alkaline phosphatase activity) in conjunction with confocal laser scanning microscopy. The differentiation of hMSCs towards the osteoblast phenotype was also investigated analysing the gene expression profile. The obtained findings provided a further insight into the development of improved strategies for the functionalization or combination of GL with other materials and 3D structures in a hybrid fashion for ensuring a tighter adhesion onto the substrates, improving cell fate over time, without negatively altering the mechanical properties and behaviour of the neat constructs. In particular, the results provided interesting information, making 3D AM GL-coated scaffolds potential candidates for bone tissue engineering.

Bone Tissue Engineering and Nanotechnology: A Promising Combination for Bone Regeneration

Large bone defects are the leading contributor to disability worldwide, affecting approximately 1.71 billion people. Conventional bone graft treatments show several disadvantages that negatively impact their therapeutic outcomes and limit their clinical practice. Therefore, much effort has been made to devise new and more effective approaches. In this context, bone tissue engineering (BTE), involving the use of biomaterials which are able to mimic the natural architecture of bone, has emerged as a key strategy for the regeneration of large defects. However, although different types of biomaterials for bone regeneration have been developed and investigated, to date, none of them has been able to completely fulfill the requirements of an ideal implantable material. In this context, in recent years, the field of nanotechnology and the application of nanomaterials to regenerative medicine have gained significant attention from researchers. Nanotechnology has revolutionized the BTE field due to the possibility of generating nanoengineered particles that are able to overcome the current limitations in regenerative strategies, including reduced cell proliferation and differentiation, the inadequate mechanical strength of biomaterials, and poor production of extrinsic factors which are necessary for efficient osteogenesis. In this review, we report on the latest in vitro and in vivo studies on the impact of nanotechnology in the field of BTE, focusing on the effects of nanoparticles on the properties of cells and the use of biomaterials for bone regeneration.

Bone tissue regeneration by 58S bioactive glass scaffolds containing exosome: an in vivo study

Exosomes, the naturally secreted nanocarriers of cells, have recently been demonstrated to have therapeutic benefits in a variety of disease models where parent cells are not present. However, the use of exosomes in bone defect regeneration has been unusual, and little is documented about the underlying processes. In recent study we produced and characterized exosomes derived human endometrial mesenchymal stem stromal cells and 58S bioactive glass scaffolds; in following, in this research exosome loaded scaffolds synthetized and release of exosome, porosity and bioactivity of them were assessed. More over the effect of scaffolds on repair of critical-size bone defects in rat's calvaria was evaluated by histological examination and micro computed tomography (µ CT). The findings confirmed that constructed porous scaffolds consistently release exosomes; additionally, in vivo findings including Hematoxilin & Eosin staining, Immunohistochemistry, Masson's trichrome, histomorphometric analysis, and µ CT clarified that our implant has osteogenic properties. We discovered that Exo-treated scaffolds might promote osteogenesis especially compared to pure scaffolds, indicating that produced scaffolds containing exosomes could be a potential replacement in bone tissue engineering.

Development of Biocompatible Digital Light Processing Resins for Additive Manufacturing Using Visible Light-Induced RAFT Polymerization

Patients with bone diseases often experience increased bone fragility. When bone injuries exceed the body's natural healing capacity, they become significant obstacles. The global rise in the aging population and the escalating obesity pandemic are anticipated to lead to a notable increase in acute bone injuries in the coming years. Our research developed a novel DLP resin for 3D printing, utilizing poly(ethylene glycol diacrylate) (PEGDA) and various monomers through the PET-RAFT polymerization method. To enhance the performance of bone scaffolds, triply periodic minimal surfaces (TPMS) were incorporated into the printed structure, promoting porosity and pore interconnectivity without reducing the mechanical resistance of the printed piece. The gyroid TPMS structure was the one that showed the highest mechanical resistance (0.94 ± 0.117 and 1.66 ± 0.240 MPa) for both variants of resin composition. Additionally, bioactive particles were introduced to enhance the material's biocompatibility, showcasing the potential for incorporating active compounds for specific applications. The inclusion of bioceramic particles produces an increase of 13% in bioactivity signal for osteogenic differentiation (alkaline phosphatase essay) compared to that of control resins. Our findings highlight the substantial improvement in printing precision and resolution achieved by including the photoabsorber, Rose Bengal, in the synthesized resin. This enhancement allows for creating intricately detailed and accurately defined 3D-printed parts. Furthermore, the TPMS gyroid structure significantly enhances the material's mechanical resistance, while including bioactive compounds significantly boosts the polymeric resin's biocompatibility and bioactivity (osteogenic differentiation).

Understanding of trabecular-cortical transition zone: Numerical and experimental assessment of multi-morphology scaffolds

Applications of additive manufacturing (AM) in tissue engineering develop rapidly. AM offers layer-by-layer creation of complex objects, developed to restore functionality of, or replace, damaged tissues. Porous 3D-printed functional gradient structures are of particular interest: their special architecture makes it possible to simulate the heterogeneity of the replaced tissue and, by continuously changing the mechanical properties, to avoid the concentration of stresses that can be caused by abrupt geometric changes. Such structures also allow combinations of different types of unit cells and a smooth transition between them, making design of personalised scaffolds with optimal parameters for the replacement of damaged host tissue at the interface between tissues possible. This paper presents the results of development of scaffold structures with gradients of porosity and multi-morphology using unit cells based on triply periodic minimal surfaces (TPMS). The mechanical behaviour of additively manufactured scaffold prototypes made of polylactide acid (PLA) was studied under compressive loading. Strain fields on their surface were captured using the Vic-3d Micro-DIC digital image correlation system and compared with those obtained with detailed numerical simulations, employing elastic-plastic properties of PLA, obtained in experiments. The effect of gradient parameters and unit-cell morphology on the stress distribution in scaffolds was analysed. A smooth gradient transition between cells with different morphologies was found to reduce the probability of structural failure under intense compressive loading. A good agreement between numerical results and experimental data was achieved, which justifies application of the developed approach to design of personalised bone scaffolds.

Promising New Horizons in Medicine: Medical Advancements with Nanocomposite Manufacturing via 3D Printing

Three-dimensional printing technology has fundamentally revolutionized the product development processes in several industries. Three-dimensional printing enables the creation of tailored prostheses and other medical equipment, anatomical models for surgical planning and training, and even innovative means of directly giving drugs to patients. Polymers and their composites have found broad usage in the healthcare business due to their many beneficial properties. As a result, the application of 3D printing technology in the medical area has transformed the design and manufacturing of medical devices and prosthetics. Polymers and their composites have become attractive materials in this industry because of their unique mechanical, thermal, electrical, and optical qualities. This review article presents a comprehensive analysis of the current state-of-the-art applications of polymer and its composites in the medical field using 3D printing technology. It covers the latest research developments in the design and manufacturing of patient-specific medical devices, prostheses, and anatomical models for surgical planning and training. The article also discusses the use of 3D printing technology for drug delivery systems (DDS) and tissue engineering. Various 3D printing techniques, such as stereolithography, fused deposition modeling (FDM), and selective laser sintering (SLS), are reviewed, along with their benefits and drawbacks. Legal and regulatory issues related to the use of 3D printing technology in the medical field are also addressed. The article concludes with an outlook on the future potential of polymer and its composites in 3D printing technology for the medical field. The research findings indicate that 3D printing technology has enormous potential to revolutionize the development and manufacture of medical devices, leading to improved patient outcomes and better healthcare services.

Bioactive and Biodegradable Polycaprolactone-Based Nanocomposite for Bone Repair Applications

This study investigated the relationship between the structure and mechanical properties of polycaprolactone (PCL) nanocomposites reinforced with baghdadite, a newly introduced bioactive agent. The baghdadite nanoparticles were synthesised using the sol-gel method and incorporated into PCL films using the solvent casting technique. The results showed that adding baghdadite to PCL improved the nanocomposites' tensile strength and elastic modulus, consistent with the results obtained from the prediction models of mechanical properties. The tensile strength increased from 16 to 21 MPa, and the elastic modulus enhanced from 149 to 194 MPa with fillers compared to test specimens without fillers. The thermal properties of the nanocomposites were also improved, with the degradation temperature increasing from 388 °C to 402 °C when 10% baghdadite was added to PCL. Furthermore, it was found that the nanocomposites containing baghdadite showed an apatite-like layer on their surfaces when exposed to simulated body solution (SBF) for 28 days, especially in the film containing 20% nanoparticles (PB20), which exhibited higher apatite density. The addition of baghdadite nanoparticles into pure PCL also improved the viability of MG63 cells, increasing the viability percentage on day five from 103 in PCL to 136 in PB20. Additionally, PB20 showed a favourable degradation rate in PBS solution, increasing mass loss from 2.63 to 4.08 per cent over four weeks. Overall, this study provides valuable insights into the structure-property relationships of biodegradable-bioactive nanocomposites, particularly those reinforced with new bioactive agents.

Synthesis and evaluation of poly(propylene fumarate)-grafted graphene oxide as nanofiller for porous scaffolds

In an effort to obtain porous scaffolds with improved mechanical properties and biocompatibility, the current study discusses nanocomposite materials based on poly(propylene fumarate)/N-vinyl pyrrolidone(PPF/NVP) networks reinforced with polymer-modified graphene oxide (GO@PPF). The GO@PPF nanofiller was synthesized through a facile and convenient surface esterification reaction, and the successful functionalization was demonstrated by complementary techniques such as FT-IR, XPS, TGA and TEM. The PPF/NVP/GO@PPF porous scaffolds obtained using NaCl as a porogen were further characterized in terms of morphology, mechanical properties, sol fraction, and in vitro degradability. SEM and nanoCT examinations of NaCl-leached samples revealed networks of interconnected pores, fairly uniform in size and shape. We show that the incorporation of GO@PPF in the polymer matrix leads to a significant enhancement in the mechanical properties, which we attribute to the formation of denser and more homogenous networks, as suggested by a decreased sol fraction for the scaffolds containing a higher amount of GO@PPF. Moreover, the surface of mineralized PPF/NVP/GO@PPG scaffolds is uniformly covered in hydroxyapatite-like crystals having a morphology and Ca/P ratio similar to bone tissue. Furthermore, the preliminary biocompatibility assessment revealed a good interaction between PPF/PVP/GO@PPF scaffolds and murine pre-osteoblasts in terms of cell viability and proliferation.

Three-Dimensional Printing of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] Biodegradable Scaffolds: Properties, In Vitro and In Vivo Evaluation

The results of constructing 3D scaffolds from degradable poly(3-hydrosbutyrpate-co-3-hydroxyvalerate) using FDM technology and studying the structure, mechanical properties, biocompatibility in vitro, and osteoplastic properties in vivo are presented. In the process of obtaining granules, filaments, and scaffolds from the initial polymer material, a slight change in the crystallization and glass transition temperature and a noticeable decrease in molecular weight (by 40%) were registered. During the compression test, depending on the direction of load application (parallel or perpendicular to the layers of the scaffold), the 3D scaffolds had a Young's modulus of 207.52 ± 19.12 and 241.34 ± 7.62 MPa and compressive stress tensile strength of 19.45 ± 2.10 and 22.43 ± 1.89 MPa, respectively. SEM, fluorescent staining with DAPI, and calorimetric MTT tests showed the high biological compatibility of scaffolds and active colonization by NIH 3T3 fibroblasts, which retained their metabolic activity for a long time (up to 10 days). The osteoplastic properties of the 3D scaffolds were studied in the segmental osteotomy test on a model defect in the diaphyseal zone of the femur in domestic Landrace pigs. X-ray and histological analysis confirmed the formation of fully mature bone tissue and complete restoration of the defect in 150 days of observation. The results allow us to conclude that the constructed resorbable 3D scaffolds are promising for bone grafting.

Post processing of low cost Aligners fabricated by additive manufacturing process to enhance the surface quality and functionality

Additive Manufacturing (AM) processes have ample advantages compared to traditional manufacturing processes, including mass customization, material efficiency, bioprinting, and fabrication of complex geometries with reduced lead time. Despite such benefits, it suffers most from staircase effects that deteriorate the fabricated part's surface quality. Nowadays, additively manufactured aligners are suitable for treating malocclusion and temporomandibular defects of teeth. Fused Deposition Modelling (FDM) is one of the best substitutes for clear aligners production to reduce per-unit cost. Glycol-modified Polyethylene Terephthalate (PETG) is opted as the material to fabricate the clear aligners due to its biocompatibility and non-toxicity. However, the poor surface quality of the additively manufactured is a major challenge in developing clear aligners with the FDM. A novel experimental setup is designed and developed to enable Chemical Vapor Smoothing (CVS) to enhance the surface quality of the clear aligners. Furthermore, based on the Surface roughness, the comparison is made between the surface quality polished with various chemicals (namely methylethylketone (also known as 2-butanone), toluene and, cyclohexanone). Moreover, Response Surface Methodology (RSM) is used to analyze the impact of different process parameters (i.e., the chemical volume, exposure time, and workpiece orientation) on the surface quality of the clear aligners. Moreover, RSM shows that the impact of the clear aligners orientation on %ΔRa during the CVS is higher than other process parameters. Results demonstrate that cyclohexanone produces more uniform surface quality with a 92.73% reduction in surface roughness compared to methylethylketone and toluene on PETG, i.e., 89.66% and 88.63%, respectively. The developed surface finishing method is capable of producing uniform, smooth surfaces over the FDM-fabricated PETG clear aligners.

Enhancement of Fracture Toughness in carbonate doped Hydroxyapatite based nanocomposites: Rietveld analysis and Mechanical behaviour

Highly nanocrystalline carbonated hydroxyapatite (CHAp) is synthesized by hydrothermal technique with four different stoichiometric compositions for microstructural and mechanical analysis. HAp is one of the most biocompatible material and addition of carbonate ions lead to increase in fracture toughness highly required in biomedical applications. The structural properties and its purity as single phase is confirmed by X-ray diffraction. Lattice imperfections and structural defects is investigated using XRD pattern model simulation, i.e. Rietveld's analysis. The substitution of CO₃^2- in HAp structure leads to a decrease in crystallinity which ultimately lessens crystallite size of sample as verified by XRD analysis. FE-SEM micrographs confirms the formation of nanorods with cuboidal morphology and porous structure of HAp and CHAp samples. The particle size distribution histogram validates the constant decrease in size due to carbonate addition. The mechanical testing of prepared samples revealed the increase in mechanical strength from 6.12 MPa to 11.52 MPa due to the addition of carbonate content, which leads to a rise in fracture toughness, a significant property of an implant material from 2.93 kN to 4.22 kN. The cumulative effect of CO₃^2- substitution on HAp structure and mechanical properties has been generalized for the application as biomedical implant material or biomedical smart materials.

Development of biodegradable customized tibial scaffold with advanced architected materials utilizing additive manufacturing

In the last decade, the development of customized biodegradable scaffolds and implants has attracted increased scientific interest due to the fact that additive manufacturing technologies allow for the rapid production of implants with high geometric complexity constructed via commercial biodegradable polymers. In this study, innovative designs of tibial scaffold in form of bone-brick configuration were developed to fill the bone gap utilizing advanced architected materials and bio-inspired diffusion canals. The architected materials and canals provide high porosity, as well as a high surface area to volume ratio in the scaffold facilitating that way in the tissue regeneration process and in withstanding the applied external loads. The cellular structures applied in this work were the Schwarz Diamond (SD) and a hybrid SD&FCC hybrid cellular material, which is a completely new architected material that derived from the combination of SD and Face Centered Cubic (FCC) structures. These designs were additively manufactured utilizing two biodegradable materials namely Polylactic acid (PLA) and Polycaprolactone (PCL), using the Fused Filament Fabrication (FFF) technique, in order to avoid the surgery, for the scaffold's removal after the bone regeneration. Furthermore, the additively manufactured scaffolds were examined in terms of compatibility and assembly with the bone's physical model, as well as, in terms of mechanical behavior under realistic static loads. In addition, non-linear finite element models (FEMs) were developed based on the experimental data to accurately simulate the mechanical response of the examined scaffolds. The Finite Element Analysis (FEA) results were compared with the experimental response and afterwards the stress concentration regions were observed and identified. Τhe proposed design of scaffold with SD&FCC lattice structure made of PLA material with a relative density of 20% revealed the best overall performance, showing that it is the most suitable candidate for further investigation (in-vivo test, clinical trials, etc.) and commercialization.

Fabrication and Testing of Multi-Hierarchical Porous Scaffolds Designed for Bone Regeneration via Additive Manufacturing Processes

Bone implants or replacements are very scarce due to the low donor availability and the high rate of body rejection. For this reason, tissue engineering strategies have been developed as alternative solutions to this problem. This research sought to create a cellular scaffold with an intricate and complex network of interconnected pores and microchannels using salt leaching and additive manufacturing (3D printing) methods that mimic the hierarchical internal structure of the bone. A biocompatible hydrogel film (based on poly-ethylene glycol) was used to cover the surface of different polymeric scaffolds. This thin film was then exposed to various stimuli to spontaneously form wrinkled micropatterns, with the aim of increasing the contact area and the material’s biocompatibility. The main innovation of this study was to include these wrinkled micropatterns on the surface of the scaffold by taking advantage of thin polymer film surface instabilities. On the other hand, salt and nano-hydroxyapatite (nHA) particles were included in the polymeric matrix to create a modified filament for 3D printing. The printed part was leached to eliminate porogen particles, leaving homogenously distributed pores on the structure. The pores have a mean size of 26.4 ± 9.9 μm, resulting in a global scaffold porosity of ~42% (including pores and microchannels). The presence of nHA particles, which display a homogeneous distribution according to the FE-SEM and EDX results, have a slight influence on the mechanical resistance of the material, but incredibly, despite being a bioactive compound for bone cells, did not show a significant increase in cell viability on the scaffold surface. However, the synergistic effect between the presence of the hydrogel and the pores on the material does produce an increase in cell viability compared to the control sample and the bare PCL material.

Bone tissue growth in ultrasonically stimulated bioinspired scaffolds

We develop computational models of bone growth in ultrasonically stimulated porous tissue scaffolds with uniform square pores and a bioinspired structure. While bone growth in the bioinspired scaffolds is slower, it produces amounts of bone comparable to the square pore scaffold, making the bioinspired structure ideal for enhancing bone growth with better structural integrity. Controlling the initial mesenchymal stem cell distribution in the scaffolds also affects the growth rate and total bone formation, which could be further useful for controlling bone growth in the scaffold based on an individual's physiology.

Multi-objective Shape Optimization of Bone Scaffolds: Enhancement of Mechanical Properties and Permeability

Porous scaffolds have recently attracted attention in bone tissue engineering. The implanted scaffolds are supposed to satisfy the mechanical and biological requirements. In this study, two porous structures named MFCC-1 (modified face centered cubic-1) and MFCC-2 (modified face centered cubic-2) are introduced. The proposed porous architectures are evaluated, optimized, and tested to enhance mechanical and biological properties. The geometric parameters of the scaffolds with porosities ranging from 70% to 90% are optimized to find a compromise between the effective Young's modulus and permeability, as well as satisfying the pore size and specific surface area requirements. To optimize the effective Young's modulus and permeability, we integrated a mathematical formulation, finite element analysis, and computational fluid dynamics simulations. For validation, the optimized scaffolds were 3D-printed, tested, and compared with two different orthogonal cylindrical struts (OCS) scaffold architectures. The MFCC designs are preferred to the generic OCS scaffolds from various perspectives: a) the MFCC architecture allows scaffold designs with porosities up to 96%; b) the very porous architecture of MFCC scaffolds allows achieving high permeabilities, which could potentially improve the cell diffusion; c) despite having a higher porosity compared to the OCS scaffolds, MFCC scaffolds improve mechanical performance regarding Young's modulus, stress concentration, and apparent yield strength; d) the proposed structures with different porosities are able to cover all the range of permeability for the human trabecular bones. The optimized MFCC designs have simple architectures and can be easily fabricated and used to improve the quality of load-bearing orthopedic scaffolds. STATEMENT OF SIGNIFICANCE: Porous scaffolds are increasingly being studied to repair large bone defects. A scaffold is supposed to withstand mechanical loads and provide an appropriate environment for bone cell growth after implantation. These mechanical and biological requirements are usually contradicting; improving the mechanical performance would require a reduction in porosity and a lower porosity is likely to reduce the biological performance of the scaffold. Various studies have shown that the mechanical and biological performance of bone scaffolds can be improved by internal architecture modification. In this study, we propose two scaffold architectures named MFCC-1 and MFCC-2 and provide an optimization framework to simultaneously optimize their stiffness and permeability to improve their mechanical and biological performances.

When Electrospun Fiber Support Matters: In Vitro Ovine Long-Term Folliculogenesis on Poly (Epsilon Caprolactone) (PCL)-Patterned Fibers

Current assisted reproduction technologies (ART) are insufficient to cover the slice of the population needing to restore fertility, as well as to amplify the reproductive performance of domestic animals or endangered species. The design of dedicated reproductive scaffolds has opened the possibility to better recapitulate the reproductive 3D ovarian environment, thus potentially innovating in vitro folliculogenesis (ivF) techniques. To this aim, the present research has been designed to compare ovine preantral follicles in vitro culture on poly(epsilon-caprolactone) (PCL)-based electrospun scaffolds designed with different topology (Random vs. Patterned fibers) with a previously validated system. The ivF performances were assessed after 14 days under 3D-oil, Two-Step (7 days in 3D-oil and on scaffold), or One-Step PCL protocols (14 days on PCL-scaffold) by assessing morphological and functional outcomes. The results show that Two- and One-Step PCL ivF protocols, when performed on patterned scaffolds, were both able to support follicle growth, antrum formation, and the upregulation of follicle marker genes leading to a greater oocyte meiotic competence than in the 3D-oil system. In conclusion, the One-Step approach could be proposed as a practical and valid strategy to support a synergic follicle-oocyte in vitro development, providing an innovative tool to enhance the availability of matured gametes on an individual basis for ART purposes.

The State of Starch/Hydroxyapatite Composite Scaffold in Bone Tissue Engineering with Consideration for Dielectric Measurement as an Alternative Characterization Technique

Hydroxyapatite (HA) has been widely used as a scaffold in tissue engineering. HA possesses high mechanical stress and exhibits particularly excellent biocompatibility owing to its similarity to natural bone. Nonetheless, this ceramic scaffold has limited applications due to its apparent brittleness. Therefore, this had presented some difficulties when shaping implants out of HA and for sustaining a high mechanical load. Fortunately, these drawbacks can be improved by combining HA with other biomaterials. Starch was heavily considered for biomedical device applications in favor of its low cost, wide availability, and biocompatibility properties that complement HA. This review provides an insight into starch/HA composites used in the fabrication of bone tissue scaffolds and numerous factors that influence the scaffold properties. Moreover, an alternative characterization of scaffolds via dielectric and free space measurement as a potential contactless and nondestructive measurement method is also highlighted.

Advances in Biodegradable 3D Printed Scaffolds with Carbon-Based Nanomaterials for Bone Regeneration

Bone possesses an inherent capacity to fix itself. However, when a defect larger than a critical size appears, external solutions must be applied. Traditionally, an autograft has been the most used solution in these situations. However, it presents some issues such as donor-site morbidity. In this context, porous biodegradable scaffolds have emerged as an interesting solution. They act as external support for cell growth and degrade when the defect is repaired. For an adequate performance, these scaffolds must meet specific requirements: biocompatibility, interconnected porosity, mechanical properties and biodegradability. To obtain the required porosity, many methods have conventionally been used (e.g., electrospinning, freeze-drying and salt-leaching). However, from the development of additive manufacturing methods a promising solution for this application has been proposed since such methods allow the complete customisation and control of scaffold geometry and porosity. Furthermore, carbon-based nanomaterials present the potential to impart osteoconductivity and antimicrobial properties and reinforce the matrix from a mechanical perspective. These properties make them ideal for use as nanomaterials to improve the properties and performance of scaffolds for bone tissue engineering. This work explores the potential research opportunities and challenges of 3D printed biodegradable composite-based scaffolds containing carbon-based nanomaterials for bone tissue engineering applications.

Tissue-specific mesenchymal stem cell-dependent osteogenesis in highly porous chitosan-based bone analogs

Among conventional fabrication techniques, freeze‐drying process has widely been investigated for polymeric implants. However, the understanding of the stem cell progenitor‐dependent cell functionality modulation and quantitative analysis of early osseointegration of highly porous scaffolds have not been explored. Here, we developed a novel, highly porous, multimaterial composite, chitosan/hydroxyapatite/polycaprolactone (CHT/HA/PCL). The in vitro studies have been performed using mesenchymal stem cells (MSCs) from three tissue sources: human bone marrow‐derived MSCs (BM‐MSCs), adipose‐derived MSCs (AD‐MSCs), and Wharton's jelly‐derived MSCs (WJ‐MSCs). Although cell attachment and metabolic activity [3‐4,5‐dimethylthiazol‐2yl‐(2,5 diphenyl‐2H‐tetrazoliumbromide) assay] were ore enhanced in WJ‐MSC‐laden CHT/HA/PCL composites, scanning electron microscopy, real‐time gene expression (alkaline phosphatase [ALP], collagen type I [Col I], osteocalcin [OCN], and bone morphogenetic protein 4 [BMP‐4]), and immunostaining (COL I, β‐CATENIN, OCN, and SCLEROSTIN [SOST]) demonstrated pronounced osteogenesis with terminal differentiation on BM‐MSC‐laden CHT/HA/PCL composites only. The enhanced cell functionality on CHT/HA/PCL composites was explained in terms of interplay among the surface properties and the optimal source of MSCs. In addition, osteogenesis in rat tibial model over 6 weeks confirmed a better ratio of bone volume to the total volume for BM‐MSC‐laden composites over scaffold‐only and defect‐only groups. The clinically conformant combination of 3D porous architecture with pore sizes varying in the range of 20 to 200  μm together with controlled in vitro degradation and early osseointegration establish the potential of CHT/HA/PCL composite as a potential cancellous bone analog.

Design and fabrication of bone tissue scaffolds based on PCL/PHBV containing hydroxyapatite nanoparticles: dual-leaching technique

Scaffolds are the important part of the tissue-engineering field that are made from different biomaterials using various techniques. In this study, new scaffold based on polycaprolactone (PCL) and poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV) containing hydroxyapatite nanopraticles (n-HA) were fabricated using the dual-leaching technique (DLT). Morphology, porosity, degradation rate, Fourier transfer infrared ray (FTIR) spectra, surface, and mechanical properties as well as capacity of cell binding and cell proliferation on the constructed scaffolds were evaluated. FTIR analysis showed that n-HA particles have some interest interactions with polymeric chains. The best 3D-structure was seen in PCL70PHBV30 scaffold using the scanning electron microscopy (SEM) and its structure improved in the presence of 3, 5 wt% of n-HA. Results of energy dispersive x-ray analysis (EDXA, map of Ca) showed that the nanoparticles have the uniform distribution within the fabricated scaffolds. Porosity analysis showed that the particulate salt leaching technique is a successful approach to building a 3D structure. Increasing of PHBV content and n-HA up to 3 and 5 wt% in the PCL matrix led to increase porosity in all samples. Mechanical properties analysis showed that values of compression modulus and strength are decreased with addition of PHBV and HA nanoparticles. These results were directly in line with the results of morphology and porosity. Cell culture experiments demonstrated that the PCL/PHBV/nHA nanocomposite scaffold has a better tendency of proliferation to cells than that of the pure PCL/PHBV scaffold. All of these results suggest promising potentials of the developed PCL/PHBV/nHA scaffolds in this study desire for bone tissue engineering.

PCL-Based Composite Scaffold Matrices for Tissue Engineering Applications

Biomaterial-based scaffolds are important cues in tissue engineering (TE) applications. Recent advances in TE have led to the development of suitable scaffold architecture for various tissue defects. In this narrative review on polycaprolactone (PCL), we have discussed in detail about the synthesis of PCL, various properties and most recent advances of using PCL and PCL blended with either natural or synthetic polymers and ceramic materials for TE applications. Further, various forms of PCL scaffolds such as porous, films and fibrous have been discussed along with the stem cells and their sources employed in various tissue repair strategies. Overall, the present review affords an insight into the properties and applications of PCL in various tissue engineering applications.

A Systematic Study on Design Initiation of Conceptual 3DPVS

An important product in biomedical and biomimetic engineering is the 3D scaffold, which mimics the real tissue in vitro to achieve the external cultivation of cells. The difference between the 3D scaffold and other biomimetic products lies in the fact that the former mimics the internal features of tissue, while the latter generally approximates the external traits of biological beings. In the field of scaffold engineering, the 3D printed vibratory scaffold, 3DPVS, has been proposed as a present-to-future novel scaffold product, and it currently stays at the stage of conceptual development. To achieve the novel design of the conceptual 3DPVS, a conceptual design process has been established by authors in their previous work, which contain three main stages, namely the design initiation, concept generation, and concept evaluation. In terms of design initiation, it is a ‘must-accomplish’ stage which generates outputs for both the subsequent concept generation and evaluation. Work of design initiation therefore is of significant value and it consists of several tasks; that is, conducting a thorough literature review, summarizing the fundamental issues preparing the general conceptual design, studying the multi-characterization of the 3DPVS, putting forward the potential base model(s), as well as indicating the ideality of the scaffold and establishing potential ideal model(s) for the 3DPVS. In this paper, design initiation will be chiefly focused upon these essential aspects to be discussed, work of which is expected to be useful in establishing a solid ground for future innovation work of the 3DPVS.

Trinity of Three-Dimensional (3D) Scaffold, Vibration, and 3D Printing on Cell Culture Application: A Systematic Review and Indicating Future Direction

Cell culture and cell scaffold engineering have previously developed in two directions. First can be 'static into dynamic', with proven effects that dynamic cultures have benefits over static ones. Researches in this direction have used several mechanical means, like external vibrators or shakers, to approximate the dynamic environments in real tissue, though such approaches could only partly address the issue. Second, can be '2D into 3D', that is, artificially created three-dimensional (3D) passive (also called 'static') scaffolds have been utilized for 3D cell culture, helping external culturing conditions mimic real tissue 3D environments in a better way as compared with traditional two-dimensional (2D) culturing. In terms of the fabrication of 3D scaffolds, 3D printing (3DP) has witnessed its high popularity in recent years with ascending applicability, and this tendency might continue to grow along with the rapid development in scaffold engineering. In this review, we first introduce cell culturing, then focus 3D cell culture scaffold, vibration stimulation for dynamic culture, and 3DP technologies fabricating 3D scaffold. Potential interconnection of these realms will be analyzed, as well as the limitations of current 3D scaffold and vibration mechanisms. In the recommendation part, further discussion on future scaffold engineering regarding 3D vibratory scaffold will be addressed, indicating 3DP as a positive bridging technology for future scaffold with integrated and localized vibratory functions.