3D printing of PEEK–cHAp scaffold for medical bone implant

Biomimetic structural design in 3D-printed scaffolds for bone tissue engineering

The rising prevalence of bone diseases in an aging population underscores the urgent need for innovative and clinically translatable solutions in bone tissue engineering. While significant progress has been made in refining the chemical properties of biomaterials, the structural design of scaffolds-a critical determinant of repair success-remains comparatively underexplored. Structural parameters such as porosity, pore size, and interconnectivity are not only essential for achieving mechanical stability but also pivotal in regulating biological processes, including vascularization, osteogenesis, and immune modulation. This review systematically categorizes scaffold architectures documented in the literature and highlights how these design parameters can be optimized to enhance bone regeneration. Advanced fabrication technologies, particularly 3D printing, are emphasized for their transformative potential in creating precise, biomimetic scaffolds that align with the complex functional demands of native bone. Furthermore, this work synthesizes diverse findings to provide a comprehensive framework for designing next-generation scaffolds. By bridging the gap between structural innovation and clinical application, this review delivers actionable strategies and a strategic roadmap for advancing the field toward improved clinical outcomes and transformative breakthroughs in regenerative medicine.

3D-Printed Scaffolds for Cranial Bone Regeneration: A Systematic Review of Design, Materials, and Computational Optimization

Cranial bone defects from trauma, congenital conditions, or surgery are challenging to treat due to the skull's limited regeneration. Traditional methods like autografts and allografts have drawbacks, including donor site issues and poor integration. 3D-printed scaffolds provide a patient-specific alternative, improving bone regeneration and integration. This review evaluates advancements in 3D-printed scaffolds for cranial bone regeneration, focusing on fabrication techniques, material innovations, and structural optimization while assessing their preclinical and clinical potential. A systematic literature search (2014-2024) was conducted using PubMed and other databases. Studies addressing scaffold properties such as porosity, pore interconnectivity, and mechanical stability were included, while non-cranial scaffold studies were excluded. Advances in 3D printing have enabled patient-specific scaffolds with optimized architecture to enhance bone regeneration, mechanical support, and nutrient transport. Bioceramics, polymers, and composites mimic native bone properties, while bioactive coatings further improve osteogenesis. However, limited clinical translation and insufficient customization remain challenges. Further preclinical and clinical trials are crucial to overcoming barriers in mechanical optimization and patient-specific scaffold fabrication, bridging the gap between research and clinical applications.

Personalised 3D-printed bioactive peek bone plate scaffold for treating femoral defects

Fractures affect millions of individuals worldwide, particularly those with osteoporosis, and often require rigid fixation for proper healing. Although traditional metal bone plates are effective, they are limited by their stiffness and inability to conform precisely to anatomical structures, leading to complications such as stress shielding and delayed healing. In this study, we utilized computer-aided design (CAD) combined with reverse engineering to develop a 3D bone plate scaffold model that perfectly matches the contours of the rabbit femur. Additionally, we employed fused deposition modeling (FDM) 3D printing to fabricate a customized polyetheretherketone (PEEK) bone plate scaffold based on the model, designed to match individual bone structures and reduce rigidity-related issues. To enhance the bioactivity of the PEEK scaffold surface, we applied plasma spraying technology to coat it with bioactive materials, including nanohydroxyapatite (HA), tantalum (Ta), and titanium (Ti). The results showed that the HA coating contained 48.06% calcium (Ca) and 16.47% phosphorus (P) and the Ti coating contained 82.32% Ti. In vitro studies showed that the bioactive scaffold effectively promoted the proliferation and differentiation of osteogenic mesenchymal stem cells, with a cell survival rate greater than 93.86%. Moreover, in vivo results from the rabbit femoral defect model showed that the bioactive scaffolds significantly accelerated bone tissue healing, with HA-coated PEEK scaffolds exhibiting exceptional bone regeneration potential. This study proposes a comprehensive strategy for customizing bone plate scaffolds, which holds significant promise for personalized precision medicine.

Experimental Investigation on the Mechanical and Dynamic Thermomechanical Properties of Polyether Ether Ketone Based on Fused Deposition Modeling

In this work, the mechanical and dynamic thermomechanical properties of PEEK based on FDM are experimentally investigated and evaluated comprehensively. The tensile failure mechanism of PEEK prepared by FDM and extrusion modeling (EM) was analyzed by fracture morphology observation. By conducting a differential scanning calorimetry (DSC) test, the crystallinity of PEEK prepared by FDM and EM was measured. The dynamic thermomechanical properties of PEEK were tested and analyzed by dynamic mechanical analysis (DMA). For FDM-prepared PEEK samples, the yield strength and elongation were 98.3 ± 0.49 MPa and 22.86 ± 2.12%, respectively. Compared with the yield strength of PEEK prepared by EM, the yield strength of PEEK prepared by FDM increased by 65.38%. The crystallinity of FDM-prepared and EM-prepared samples was calculated as 34.81% and 31.55%, respectively. Different processing methods resulted in differences in the microscopic morphology and crystallinity of two types of PEEK parts, leading to differences in mechanical properties. The internal micropores generated during the FDM processing of PEEK significantly reduced the elongation. Moreover, according to the DMA results, the glass transition activation energy of PEEK was obtained as ΔE = 685.07 kJ/mol based on the Arrhenius equation. Due to the excellent mechanical properties of PEEK prepared by FDM processing, it is promising for high-performance polymer applications in different fields.

Improved Biocompatibility in Laser-Polished Implants

This research aims to enhance the surface quality, mechanical properties, and biocompatibility of PEEK (polyether-ether-ketone) biomimetic dental implants through laser polishing. The objective is to improve osseointegration and implant durability by reducing surface roughness, increasing hydrophilicity, and enhancing mechanical strength. The methodology involved fabricating PEEK implants via FDM and applying laser polishing. The significant findings showed a 66.7% reduction in surface roughness, Ra reduced from 2.4 µm to 0.8 µm, and a 25.3% improvement in hydrophilicity, water contact angle decreased from 87° to 65°. Mechanical tests revealed a 6.3% increase in tensile strength (96 MPa to 102 MPa) and a 50% improvement in fatigue resistance (100,000 to 150,000 cycles). The strength analysis result showed a 10% increase in stiffness storage modulus from 1400 MPa to 1500 MPa. Error analysis showed a standard deviation of ±3% across all tests. In conclusion, laser polishing significantly improves the surface, mechanical, and biological performance of PEEK implants, making it a promising approach for advancing biomimetic dental implant technology.

Innovative PEEK in Dentistry of Enhanced Adhesion and Sustainability through AI-Driven Surface Treatments

This research investigates using Polyether ether ketone (PEEK) in dental prosthetics, focusing on enhancing the mechanical properties, adhesion capabilities, and environmental sustainability through AI-driven data analysis and advanced surface treatments. The objectives include improving PEEK's adhesion to dental types of cement, assessing its biocompatibility, and evaluating its environmental impact compared to traditional materials. The methodologies employed involve surface treatments such as plasma treatment and chemical etching, mechanical testing under ASTM standards, biocompatibility assessments, and lifecycle analysis. AI models predict and optimize mechanical properties based on extensive data. Significant findings indicate that surface-treated PEEK exhibits superior adhesion properties, maintaining robust mechanical integrity with no cytotoxic effects and supporting its use in direct contact with human tissues. Lifecycle analysis suggests PEEK offers a reduced environmental footprint due to lower energy-intensive production processes and recyclability. AI-driven analysis further enhances the material's performance prediction and optimization, ensuring better clinical outcomes. The study concludes that with improved surface treatments and AI optimization, PEEK is a promising alternative to conventional dental materials, combining enhanced performance with environmental sustainability, paving the way for broader acceptance in dental applications.

Challenges to Improve Extrusion-Based Additive Manufacturing Process of Thermoplastics toward Sustainable Development

This review aims to present the different approaches to lessen the environmental impact of the extrusion-based additive manufacturing (MEX) process of thermoplastic-based resins and protect the ecosystem. The benefits and drawbacks of each alternative, including the use of biomaterials or recycled materials as feedstock, energy efficiency, and polluting emissions reduction, have been examined. First, the technological option of using a pellet-fed printer was compared to a filament-fed printer. Then, common biopolymers utilized in MEX applications are discussed, along with methods for improving the mechanical properties of associated printed products. The introduction of natural fillers in thermoplastic resins and the use of biocomposite filaments have been proposed to improve the specific performance of printed items, highlighting the numerous challenges related to their extrusion. Various polymers and fillers derived from recycling are presented as feeding raw materials for printers to reduce waste accumulation, showing the inferior qualities of the resulting goods when compared to printed products made from virgin materials. Finally, the energy consumption and emissions released into the atmosphere during the printing process are discussed, with the potential for both aspects to be controlled through material selection and operating conditions.

Beyond hype: unveiling the Real challenges in clinical translation of 3D printed bone scaffolds and the fresh prospects of bioprinted organoids

Bone defects pose significant challenges in healthcare, with over 2 million bone repair surgeries performed globally each year. As a burgeoning force in the field of bone tissue engineering, 3D printing offers novel solutions to traditional bone transplantation procedures. However, current 3D-printed bone scaffolds still face three critical challenges in material selection, printing methods, cellular self-organization and co-culture, significantly impeding their clinical application. In this comprehensive review, we delve into the performance criteria that ideal bone scaffolds should possess, with a particular focus on the three core challenges faced by 3D printing technology during clinical translation. We summarize the latest advancements in non-traditional materials and advanced printing techniques, emphasizing the importance of integrating organ-like technologies with bioprinting. This combined approach enables more precise simulation of natural tissue structure and function. Our aim in writing this review is to propose effective strategies to address these challenges and promote the clinical translation of 3D-printed scaffolds for bone defect treatment.

AI-Driven Data Analysis of Quantifying Environmental Impact and Efficiency of Shape Memory Polymers

This research investigates the environmental sustainability and biomedical applications of shape memory polymers (SMPs), focusing on their integration into 4D printing technologies. The objectives include comparing the carbon footprint, embodied energy, and water consumption of SMPs with traditional materials such as metals and conventional polymers and evaluating their potential in medical implants, drug delivery systems, and tissue engineering. The methodology involves a comprehensive literature review and AI-driven data analysis to provide robust, scalable insights into the environmental and functional performance of SMPs. Thermomechanical modeling, phase transformation kinetics, and heat transfer analyses are employed to understand the behavior of SMPs under various conditions. Significant findings reveal that SMPs exhibit considerably lower environmental impacts than traditional materials, reducing greenhouse gas emissions by approximately 40%, water consumption by 30%, and embodied energy by 25%. These polymers also demonstrate superior functionality and adaptability in biomedical applications due to their ability to change shape in response to external stimuli. The study concludes that SMPs are promising sustainable alternatives for biomedical applications, offering enhanced patient outcomes and reduced environmental footprints. Integrating SMPs into 4D printing technologies is poised to revolutionize healthcare manufacturing processes and product life cycles, promoting sustainable and efficient medical practices.

3D-printed polyether-ether ketone/carboxymethyl cellulose scaffolds coated with Zn-Mn doped mesoporous bioactive glass nanoparticles

Patient-specific fabrication of scaffold/implant requires an engineering approach to manufacture the ideal scaffold. Herein, we design and 3D print scaffolds comprised of polyether-ether-ketone (PEEK) and sodium-carboxymethyl cellulose (Na-CMC). The fabricated scaffold was dip coated with Zn and Mn doped bioactive glass nanoparticles (Zn-Mn MBGNs). The synthesized ink exhibit suitable shear-thinning behavior for direct ink write (DIW) 3D printing. The scaffolds were crafted with precision, featuring 85% porosity, 0.3 mm layer height, and 1.5 mm/s printing speed at room temperature. Scanning electron microscopy images reveal a well-defined scaffold with an average pore size of 600 ± 30 μm. The energy dispersive X-ray spectroscopy analysis confirmed a well dispersed/uniform coating of Zn-Mn MBGNs on the PEEK/Na-CMC scaffold. Fourier transform infrared spectroscopy approved the presence of PEEK, CMC, and Zn-Mn MBGNs. The tensile test revealed a Young's modulus of 2.05 GPa. Antibacterial assays demonstrate inhibition zone against Staphylococcus aureus and Escherichia Coli strains. Chick Chorioallantoic Membrane assays also present significant angiogenesis potential, owing to the antigenic nature of Zn-Mn MBGNs. WST-8 cell viability assays depicted cell proliferation, with a 103% viability after 7 days of culture. This study suggests that the PEEK/Na-CMC scaffolds coated with Zn-Mn MBGNs are an excellent candidate for osteoporotic fracture treatment. Thus, the fabricated scaffold can offer multifaceted properties for enhanced patient outcomes in the bone tissue regeneration.

A Hierarchical Nano to Micro Scale Modelling of 3D Printed Nano-Reinforced Polylactic Acid: Micropolar Modelling and Molecular Dynamics Simulation

Fused deposition modelling (FDM) is an additive manufacturing technique widely used for rapid prototyping. This method facilitates the creation of parts with intricate geometries, making it suitable for advanced applications in fields such as tissue engineering, aerospace, and electronics. Despite its advantages, FDM often results in the formation of voids between the deposited filaments, which can compromise mechanical properties. However, in some cases, such as the design of scaffolds for bone regeneration, increased porosity can be advantageous as it allows for better permeability. On the other hand, the introduction of nano-additives into the FDM material enhances design flexibility and can significantly improve the mechanical properties. Therefore, modelling FDM-produced components involves complexities at two different scales: nanoscales and microscales. Material deformation is primarily influenced by atomic-scale phenomena, especially with nanoscopic constituents, whereas the distribution of nano-reinforcements and FDM-induced heterogeneities lies at the microscale. This work presents multiscale modelling that bridges the nano and microscales to predict the mechanical properties of FDM-manufactured components. At the nanoscale, molecular dynamic simulations unravel the atomistic intricacies that dictate the behaviour of the base material containing nanoscopic reinforcements. Simulations are conducted on polylactic acid (PLA) and PLA reinforced with silver nanoparticles, with the properties derived from MD simulations transferred to the microscale model. At the microscale, non-classical micropolar theory is utilised, which can account for materials' heterogeneity through internal scale parameters while avoiding direct discretization. The developed mechanical model offers a comprehensive framework for designing 3D-printed PLA nanocomposites with tailored mechanical properties.

Construction of antibacterial bone implants and their application in bone regeneration

Bacterial infection represents a prevalent challenge during the bone repair process, often resulting in implant failure. However, the extensive use of antibiotics has limited local antibacterial effects at the infection site and is prone to side effects. In order to address the issue of bacterial infection during the transplantation of bone implants, four types of bone scaffold implants with long-term antimicrobial functionality have been constructed, including direct contact antimicrobial scaffold, dissolution-penetration antimicrobial scaffold, photocatalytic antimicrobial scaffold, and multimodal synergistic antimicrobial scaffold. The direct contact antimicrobial scaffold involves the physical penetration or disruption of bacterial cell membranes by the scaffold surface or hindrance of bacterial adhesion through surface charge, microstructure, and other factors. The dissolution-penetration antimicrobial scaffold releases antimicrobial substances from the scaffold's interior through degradation and other means to achieve local antimicrobial effects. The photocatalytic antimicrobial scaffold utilizes the absorption of light to generate reactive oxygen species (ROS) with enhanced chemical reactivity for antimicrobial activity. ROS can cause damage to bacterial cell membranes, deoxyribonucleic acid (DNA), proteins, and other components. The multimodal synergistic antimicrobial scaffold involves the combined use of multiple antimicrobial methods to achieve synergistic effects and effectively overcome the limitations of individual antimicrobial approaches. Additionally, the biocompatibility issues of the antimicrobial bone scaffold are also discussed, including in vitro cell adhesion, proliferation, and osteogenic differentiation, as well as in vivo bone repair and vascularization. Finally, the challenges and prospects of antimicrobial bone implants are summarized. The development of antimicrobial bone implants can provide effective solutions to bacterial infection issues in bone defect repair in the foreseeable future.

Bibliometric Analysis-Based Review of Fused Deposition Modeling 3D Printing Method (1994-2020)

This study aimed at the detailed bibliometric analysis (BA) of fused deposition modeling (FDM) to understand the trend and research area. Web of Science database was used for extracting data using keywords, and 2793 documents were analyzed. From the analysis, the most influential and productive authors, countries, sources, and so on were identified and corresponding interrelations were represented by a three-field plot. Lotka's law was derived for author productivity and its reliability was verified by the Kolmogorov-Smirnov (K-S) test. Bradford's law was used for identifying the core sources contributing to the field of FDM. From the trend topic analysis, it was found that initially the research was focused upon removing error related to deposition as well as part orientation, but with the course of time, it diversified to include topics such as optimization of printing parameters, materials, and applications. Based on the inferences from BA, the article also discusses on current research trend and highlights certain future areas for research work.

Performance of 3D printed porous polyetheretherketone composite scaffolds combined with nano-hydroxyapatite/carbon fiber in bone tissue engineering: a biological evaluation

Polyetheretherketone (PEEK) has been one of the most promising materials in bone tissue engineering in recent years, with characteristics such as biosafety, corrosion resistance, and wear resistance. However, the weak bioactivity of PEEK leads to its poor integration with bone tissues, restricting its application in biomedical fields. This research effectively fabricated composite porous scaffolds using a combination of PEEK, nano-hydroxyapatite (nHA), and carbon fiber (CF) by the process of fused deposition molding (FDM). The experimental study aimed to assess the impact of varying concentrations of nHA and CF on the biological performance of scaffolds. The incorporation of 10% CF has been shown to enhance the overall mechanical characteristics of composite PEEK scaffolds, including increased tensile strength and improved mechanical strength. Additionally, the addition of 20% nHA resulted in a significant increase in the surface roughness of the scaffolds. The high hydrophilicity of the PEEK composite scaffolds facilitated the in vitro inoculation of MC3T3-E1 cells. The findings of the study demonstrated that the inclusion of 20% nHA and 10% CF in the scaffolds resulted in improved cell attachment and proliferation compared to other scaffolds. This suggests that the incorporation of 20% nHA and 10% CF positively influenced the properties of the scaffolds, potentially facilitating bone regeneration. In vitro biocompatibility experiments showed that PEEK composite scaffolds have good biosafety. The investigation on osteoblast differentiation revealed that the intensity of calcium nodule staining intensified, along with an increase in the expression of osteoblast transcription factors and alkaline phosphatase activities. These findings suggest that scaffolds containing 20% nHA and 10% CF have favorable properties for bone induction. Hence, the integration of porous PEEK composite scaffolds with nHA and CF presents a promising avenue for the restoration of bone defects using materials in the field of bone tissue engineering.

Advances in 3D Printing of Highly Bioadaptive Bone Tissue Engineering Scaffolds

The number of patients with bone defects caused by trauma, bone tumors, and osteoporosis has increased considerably. The repair of irregular, recurring, and large bone defects poses a great challenge to clinicians. Bone tissue engineering is emerging as an appropriate strategy to replace autologous bone grafting in the repair of critically sized bone defects. However, the suitability of bone tissue engineering scaffolds in terms of structure, mechanics, degradation, and the microenvironment is inadequate. Three-dimensional (3D) printing is an advanced additive-manufacturing technology widely used for bone repair. 3D printing constructs personalized structurally adapted scaffolds based on 3D models reconstructed from CT images. The contradiction between the mechanics and degradation is resolved by altering the stacking structure. The local microenvironment of the implant is improved by designing an internal pore structure and a spatiotemporal factor release system. Therefore, there has been a boom in the 3D printing of personalized bone repair scaffolds. In this review, successful research on the preparation of highly bioadaptive bone tissue engineering scaffolds using 3D printing is presented. The mechanisms of structural, mechanical, degradation, and microenvironmental adaptations of bone prostheses and their interactions were elucidated to provide a feasible strategy for constructing highly bioadaptive bone tissue engineering scaffolds.

Waste to wonder to explore possibilities with recycled materials in 3D printing

In a world grappling with environmental challenges and the need for sustainable manufacturing practices, the convergence of 3D printing and recycling emerges as a promising solution. This research paper explores the potential of combining these two technologies and comprehensively analyses their synergistic effects. The study delves into the printability of recycled materials, evaluating their suitability for 3D printing and comparing their performance with conventional materials. The environmental impact of 3D printing with recycled materials is examined through a sustainability analysis and a life cycle assessment of recycled 3D printed objects. The findings reveal significant benefits, including enhanced resource efficiency, waste reduction, and customisation possibilities. The research also identifies challenges and opportunities for scaling up the use of recycled materials in 3D printing, highlighting the importance of collaboration, innovation, and regulations. With potential applications spanning various industries, from prototyping to construction and healthcare, the implications of this research are far-reaching. By embracing sustainable practices, industry collaboration, and innovation, the integration of 3D printing and recycling can pave the way for a more sustainable future, where resource conservation, circularity, and customised production are at the forefront of manufacturing.

Research progress of 3D printed poly (ether ether ketone) in the reconstruction of craniomaxillofacial bone defects

The clinical challenge of bone defects in the craniomaxillofacial region, which can lead to significant physiological dysfunction and psychological distress, persists due to the complex and unique anatomy of craniomaxillofacial bones. These critical-sized defects require the use of bone grafts or substitutes for effective reconstruction. However, current biomaterials and methods have specific limitations in meeting the clinical demands for structural reinforcement, mechanical support, exceptional biological performance, and aesthetically pleasing reconstruction of the facial structure. These drawbacks have led to a growing need for novel materials and technologies. The growing development of 3D printing can offer significant advantages to address these issues, as demonstrated by the fabrication of patient-specific bioactive constructs with controlled structural design for complex bone defects in medical applications using this technology. Poly (ether ether ketone) (PEEK), among a number of materials used, is gaining recognition as a feasible substitute for a customized structure that closely resembles natural bone. It has proven to be an excellent, conformable, and 3D-printable material with the potential to replace traditional autografts and titanium implants. However, its biological inertness poses certain limitations. Therefore, this review summarizes the distinctive features of craniomaxillofacial bones and current methods for bone reconstruction, and then focuses on the increasingly applied 3D printed PEEK constructs in this field and an update on the advanced modifications for improved mechanical properties, biological performance, and antibacterial capacity. Exploring the potential of 3D printed PEEK is expected to lead to more cost-effective, biocompatible, and personalized treatment of craniomaxillofacial bone defects in clinical applications.

Optimization and manufacture of polyetheretherketone patient specific cranial implants by material extrusion - A clinical perspective

Polyetheretherketone (PEEK) is a high performing thermoplastic that has established itself as a 'gold-standard' material for cranial reconstruction. Traditionally, milled PEEK patient specific cranial implants (PSCIs) exhibit uniform levels of smoothness (excusing suture/drainage holes) to the touch (<1 μm) and homogenous coloration throughout. They also demonstrate predictable and repeatable levels of mechanical performance, as they are machined from isotropic material blocks. The combination of such factors inspires confidence from the surgeon and in turn, approval for implantation. However, manufacturing lead-times and affiliated costs to fabricate a PSCI are high. To simplify their production and reduce expenditure, hospitals are exploring the production of in-house PEEK PSCIs by material extrusion-based additive manufacturing. From a geometrical and morphological perspective, such implants have been produced with good-to-satisfactory clinical results. However, lack of clinical adoption persists. To determine the reasoning behind this, it was necessary to assess the benefits and limitations of current printed PEEK PSCIs in order to establish the status quo. Afterwards, a review on individual PEEK printing variables was performed in order to identify a combination of parameters that could enhance the aesthetics and performance of the PSCIs to that of milled implants/cranial bone. The findings from this review could be used as a baseline to help standardize the production of PEEK PSCIs by material extrusion in the hospital.

Current surface modification strategies to improve the binding efficiency of emerging biomaterial polyetheretherketone (PEEK) with bone and soft tissue: A literature review

PURPOSE

The aim of this study was to review the literature on current surface modification strategies used to improve the binding efficiency of an emerging biological material, polyetheretherketone (PEEK), with bone and soft tissues.

STUDY SELECTION

This review was based on articles retrieved from PubMed, Google Scholar, Web of Science, and ScienceDirect databases. The main keywords used during the search were "polyetheretherketone (PEEK)," "implant," "surface modification," "biomaterials," "bone," "osseointegration," and "soft tissue."

RESULTS

The suitability of PEEK surface modification strategies has been critically analyzed and summarized here. Many cell and in vivo experiments in small animals have shown that the use of advanced modification technologies with appropriate surface modification strategies can effectively improve the surface inertness of PEEK, thereby improving its binding efficiency with bone and soft tissues.

CONCLUSIONS

Surface modifications of PEEK have revealed new possibilities for implant treatment; however, most results are based on in vitro or short-term in vivo evaluations in small animals. To achieve a broad application of PEEK in the field of oral implantology, more in vivo experiments and long-term clinical evaluations are needed to investigate the effects of various surface modifications on the tissue integration ability of PEEK to develop an ideal implant material.

Box-Behnken modeling to quantify the impact of control parameters on the energy and tensile efficiency of PEEK in MEX 3D-printing

Currently, energy efficiency and saving in production engineering, including Material Extrusion (MEX) Additive Manufacturing, are of key importance to ensure process sustainability and cost-effectiveness. The functionality of parts made with MEX 3D-printing remains solid, especially for expensive high-performance polymers, for biomedical, automotive, and aerospace industries. Herein, the energy and tensile strength metrics are investigated over three key process control parameters (Nozzle Temperature, Layer Thickness, and Printing Speed), with the aid of laboratory-scale PEEK filaments fabricated with melt extrusion. A double optimization is attempted for the production by consuming minimum energy, of PEEK parts with improved strength. A three-level Box-Behnken design with five replicas for each experimental run was employed. Statistical analysis of the experimental findings proved that LT is the most decisive control setting for mechanical strength. An LT of 0.1 mm maximized the tensile endurance (∼74 MPa), but at the same time, it was responsible for the worst energy (∼0.58 MJ) and printing time (∼900 s) expenditure. The experimental and statistical findings are further discussed and interpreted using fractographic SEM and optical microscopy, revealing the 3D printing quality and the fracture mechanisms in the samples. Thermogravimetric analysis (TGA) was performed. The findings hold measurable engineering and industrial merit, since they may be utilized to achieve an optimum case-dependent compromise between the usually contradictory goals of productivity, energy performance, and mechanical functionality.

Polyetheretherketone development in bone tissue engineering and orthopedic surgery

Polyetheretherketone (PEEK) has been widely used in the medical field as an implant material, especially in bone tissue engineering and orthopedic surgery, in recent years. This material exhibits superior stability at high temperatures and is biosecured without harmful reactions. However, the chemical and biological inertness of PEEK still limits its applications. Recently, many approaches have been applied to improve its performance, including the modulation of physical morphology, chemical composition and antimicrobial agents, which advanced the osteointegration as well as antibacterial properties of PEEK materials. Based on the evolution of PEEK biomedical devices, many studies on the use of PEEK implants in spine surgery, joint surgery and trauma repair have been performed in the past few years, in most of which PEEK implants show better outcomes than traditional metal implants. This paper summarizes recent studies on the modification and application of biomedical PEEK materials, which provides further research directions for PEEK implants.

Influence of Process Parameters on the Characteristics of Additively Manufactured Parts Made from Advanced Biopolymers

Over the past few decades, additive manufacturing (AM) has become a reliable tool for prototyping and low-volume production. In recent years, the market share of such products has increased rapidly as these manufacturing concepts allow for greater part complexity compared to conventional manufacturing technologies. Furthermore, as recyclability and biocompatibility have become more important in material selection, biopolymers have also become widely used in AM. This article provides an overview of AM with advanced biopolymers in fields from medicine to food packaging. Various AM technologies are presented, focusing on the biopolymers used, selected part fabrication strategies, and influential parameters of the technologies presented. It should be emphasized that inkjet bioprinting, stereolithography, selective laser sintering, fused deposition modeling, extrusion-based bioprinting, and scaffold-free printing are the most commonly used AM technologies for the production of parts from advanced biopolymers. Achievable part complexity will be discussed with emphasis on manufacturable features, layer thickness, production accuracy, materials applied, and part strength in correlation with key AM technologies and their parameters crucial for producing representative examples, anatomical models, specialized medical instruments, medical implants, time-dependent prosthetic features, etc. Future trends of advanced biopolymers focused on establishing target-time-dependent part properties through 4D additive manufacturing are also discussed.

Mechanical performance and bioactivation of 3D-printed PEEK for high-performance implant manufacture: a review

Polyetheretherketone (PEEK) has stood out as the leading high-performance thermoplastic for the replacement of metals in orthopaedic, trauma and spinal implant applications due to its high biocompatibility and mechanical properties. Despite its potential for custom-made medical devices, 3D-printed PEEK's mechanical performance depends on processing parameters and its bioinertness may hinder bone opposition to the implant. Concerning these challenges, this review focuses on the available literature addressing the improvement of the mechanical performance of PEEK processed through "fused filament fabrication" (FFF) along with literature on bioactivation of PEEK for improved osseointegration. The reviewed research suggests that improvements can be achieved in mechanical performance of 3D-printed PEEK with adequate FFF parametrization while different bioactivation techniques can be used to improve the bioperformance of 3D-printed PEEK. The adequate approaches towards these procedures can increase PEEK's potential for the manufacture of high-performance custom-made implantable devices that display improved bone-implant integration and prevent stress shielding of the treated bone.

Additive manufactured polyether-ether-ketone composite scaffolds with hydroxyapatite filler and porous structure promoted the integration with soft tissue

Additive Manufactured (AM) Polyether-ether-ketone (PEEK) orthopaedic implants offer new opportunities for bone substitutes. However, owing to its chemical inertness, the integration between PEEK implants and soft tissue represents a major challenge threatening the early success of the PEEK implants. Here we investigated the influence of hydroxyapatite (HA) fillers and porous structure of AM HA/PEEK scaffolds on the integration with soft tissue through in-vitro cellular experiments and in-vivo rabbit experiments. Among the animal experiments, HA/PEEK composite scaffolds with HA contents of 0, 20 wt%, 40 wt% and pore sizes of 0.8 mm, 1.6 mm were manufactured by fused filament fabrication. The results indicated that HA promoted the proliferation and adhesion of myofibroblasts on PEEK-based composites by releasing Ca²⁺ to active FAK and its downstream proteins, while the surface morphology of the scaffolds was also roughened by the HA particles, both of which led to the tighter adhesion between HA/PEEK scaffolds and soft tissue in-vivo. The macroscopic bonding force between soft tissue and scaffolds was dominated by the pore size of the scaffolds but was hardly affected by neither the HA content and nor the surface morphology. Scaffolds with larger pore size bonded more strongly to the soft tissue, and the maximum bonding force reached to 5.61 ± 2.55 N for 40 wt% HA/PEEK scaffolds with pore size of 1.6 mm, which was higher than that between natural bone and soft tissue of rabbits. Although the larger pore size and higher HA content of the PEEK-based scaffolds facilitated the bonding with the soft tissue, the consequent outcome of reduced mechanical properties has to be compromised in the design of the porous PEEK-based composite implants. The present study provides engineering-accessible synergistic strategies on material components and porous architecture of AM PEEK orthopaedic implants for improving the integration with soft tissue.

Silicon dioxide nanoparticles decorated on graphene oxide nanosheets and their application in poly(l-lactic acid) scaffold

INTRODUCTION

The aggregation of graphene oxide (GO) is considered as main challenge, although GO possesses excellent mechanical properties which arouses widespread attention as reinforcement for polymers.

OBJECTIVES

In this study, silicon dioxide (SiO₂) nanoparticles were decorated onto surface of GO nanosheets through in situ growth method for promoting dispersion of GO in poly(l-lactic acid) (PLLA) bone scaffold.

METHODS

Hydroxyl and carboxyl functional groups of GO provided sites for SiO₂ nucleation, and SiO₂ grew with hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) and finally formed nanoparticles onto surface of GO with covalent bonds. Then, the GO@ SiO₂ nanocomposite was blended with PLLA for the fabrication of bone scaffold by selective laser sintering (SLS).

RESULT

The results indicated that the obtained SiO₂ were distributed relatively uniformly on surface of GO under TEOS concentration of 0.10 mol/L (GO@SiO₂-10), and the covering of SiO₂ on GO could increase interlayer distance of GO nanosheets from 0.799 nm to 0.894 nm, thus reducing van der Waals forces between GO nanosheets and facilitating the dispersion. Tensile and compressive strength of scaffold containing GO@SiO₂ hybrids were significantly enhanced, especially for the scaffold containing GO@SiO₂-10 hybrids with enhancement of 30.95 % in tensile strength and 66.33 % in compressive strength compared with the scaffold containing GO. Additionally, cell adhesion and fluorescence experiments demonstrated excellent cytocompatibility of the scaffold.

CONCLUSIONS

The good dispersion of GO@SiO₂ enhances the mechanical properties and cytocompatibility of scaffold, making it a potential candidate for bone tissue engineering applications.

Low-Temperature Printed Hierarchically Porous Induced-Biomineralization Polyaryletherketone Scaffold for Bone Tissue Engineering

Polyetheretherketone (PEEK) as a popular orthopaedic implant is usually fabricated into a hierarchically porous structure for improving osteogenic activity. However, the applications are limited due to the excessively high processing temperature and uncontrollably tedious modification routes. Here, an amorphous polyaryletherketone with carboxyl groups (PAEK-COOH) is synthesized and fabricated to the hierarchically controllable porous scaffolds via a low-temperature 3D-printing process. The prepared PAEK-COOH scaffolds present controllable porous structures ranging from nano- to micro-scale, and their mechanical strengths are comparable to that of trabecular bone. More importantly, the in vitro experiments show that the nanoporous surface is conducive to promoting cellular adhesion, and carboxyl groups can induce hydroxyapatite mineralization via electrostatic interaction. The in vivo experiments demonstrate that the PAEK-COOH scaffolds offer much better osseointegration without additional active ingredients, compared to that of PEEK. Therefore, this work will not only develop a promising candidate for bone tissue engineering, but provide a viable method to design PAEK biomaterials.

Impact of rGO-coated PEEK and lattice on bone implant

The composite coating can effectively inhibit bacterial proliferation and promote the expression of bone-building genes in-vitro. Therefore, a novel production was used to produce poly-ether-ether-ketone, and reduced graphene oxide (PEEK-rGO) scaffolds with ratios of 1-3%, combining a different lattice for a bone implant. An inexpensive method was developed to prepare the new coatings on the PEEK scaffold with reduced graphene oxide (rGO). Mechanical testing, data analysis and cell culture tests for in-vitro biocompatibility scaffold characterisation for the PEEK composite were conducted. Novel computation microanalysis of four-dimensional (4D) printing of microstructure of PEEK-rGO concerning the grain size and three dimensional (3D) morphology was influenced by furrow segmentation of grains cell growth on the composite, which was reduced from an average of 216-155 grains and increased to 253 grains on the last day. The proposed spherical nanoparticles cell grew with time after dispersed PEEK nanoparticles in calcium hydroxyapatite (cHAp) grains. Also, the mechanical tests were carried out to validate the strength of the new composites and compare them to that of a natural bone. The established 3D-printed PEEK composite scaffolds significantly exhibited the potential of bone implants for biomimetic heterogeneous bone repair.

3D Printed Strontium and Zinc Doped Hydroxyapatite Loaded PEEK for Craniomaxillofacial Implants

In this study, Strontium (Sr) and Zinc (Zn) doped-HA nanoparticles were synthesized and incorporated into polyetheretherketone (PEEK) up to 30 wt.% and processed by a novel approach i.e., fused deposition modelling (FDM) 3D printing for the production of patient specific cranial implants with improved bioactivity and the required mechanical performance. Filaments were produced via extrusion and subsequently 3D-printed using FDM. To further improve the bioactivity of the 3D-printed parts, the samples were dip-coated in polyethylene glycol-DOPA (PEG-DOPA) solution. The printing quality was influenced by filler loading, but was not significantly influenced by the nature of doped-HA. Hence, the printing conditions were optimized for each sample. Micro-CT and Scanning Electron Microscopy (SEM) showed a uniform distribution of bioceramic particles in PEEK. Although agglomeration of particles increased with increase in filler loadings. Differential Scanning Calorimetry (DSC) showed that the melting point and crystallinity of PEEK increased with an increase in doped-HA loading from 343 °C to 355 °C and 27.7% to 34.6%, respectively. Apatite formation was confirmed on the 3D-printed samples after immersion in simulated body fluid (SBF) for 7, 14 and 28 days via SEM, X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The tensile strength and impact strength decreased from 75 MPa to 51 MPa and 14 kJ/m2 to 4 kJ/m2, respectively, while Young's modulus increased with increasing doped-HA content from 2.8 GPa to 4.2 GPa. However, the tensile strengths of composites remained in the range of human cortical bone i.e., ≥50 MPa. In addition, there was a slight increase in mechanical strength after 28 days immersion which was attributed to apatite formation. Water contact angle showed that the hydrophilicity of the samples improved after coating the 3D-printed samples with PEG-DOPA. Hence, based on the results, the 3D-printed PEEK nanocomposites with 20 wt.% doped-HA is selected as the best candidate for the 3D-printing of craniomaxillofacial implants.

Apoptotic cells derived micro/nano-sized extracellular vesicles in tissue regeneration

Extracellular vesicles (EVs), products released by cells in multiple biological activities, are currently widely accepted as functional particles and intercellular communicators. From the orthodox perspective, EVs derived from apoptotic cells (apoEVs) are responsible for cell debris clearance, while recent studies have demonstrated that apoEVs participate in tissue regeneration. However, the underlying mechanisms and particular functions in tissue regeneration promotion of apoEVs remain ambiguous. Some molecules, such as caspases, active during apoptosis also function in tissue regeneration triggered by apoptosis,. ApoEVs are generated in the process of apoptosis, carrying cell contents to manifest biological effects, and possessing biomarkers to target phagocytes. The regenerative effect of apoEVs might be due to their abilities to facilitate cell proliferation and regulate inflammation. Such regenerative effect has been observed in various tissues, including skin, bone, cardiovascular system, and kidney. Engineered apoEVs are produced to amplify the biological benefits of apoEVs, rendering them optional for drug delivery. Meanwhile, challenges exist in thorough mechanistic exploration and standardization of production. In this review, we discussed the link between apoptosis and regeneration, current comprehension of the origination and investigation strategies of apoEVs, and mechanisms in tissue regeneration by apoEVs and their applications. Challenges and prospects are also discussed here.

3D PEEK Objects Fabricated by Fused Filament Fabrication (FFF)

PEEK (poly ether ether ketone) materials printed using FFF 3D printing have been actively studied on applying electronic devices in satellites owing to their excellent light weight and thermal resistance. However, the PEEK FFF process generated cavities inside due to large shrinkage has degraded both mechanical integrity and printing reliability. Here, we have investigated the correlations between nozzle temperatures and PEEK printing behaviors such as the reliability of printed line width and surface roughness. As the temperature increased from 360 to 380 °C, the width of the printed line showed a tendency to decrease. However, the width of PEEK printed lines re-increased from 350 to 426 μm at the nozzle temperatures between 380 and 400 °C, associated with solid to liquid-like phase transition and printed out distorted and disconnected lines. The surface roughness of PEEK objects increased from 49 to 55 μm as the nozzle temperature increased from 380 to 400 °C, where PEEK is melted down and quickly solidified based on more energy and additional heating time at higher printing temperatures at 400 °C. Based on these printing trends, a reliability analysis of the printed line was performed. The printed line formed the most uniform width at 380 °C and had a highest Weibull coefficient of 28.6 using the reliability analysis technique called Weibull modulus.

Modifying a 3D-Printed Ti6Al4V Implant with Polydopamine Coating to Improve BMSCs Growth, Osteogenic Differentiation, and In Situ Osseointegration In Vivo

Nowadays, 3D printing technology has been applied in dentistry to fabricate customized implants. However, the biological performance is unsatisfactory. Polydopamine (PDA) has been used to immobilize bioactive agents on implant surfaces to endow them with multiple properties, such as anti-infection and pro-osteogenesis, benefiting rapid osseointegration. Herein, we fabricated a PDA coating on a 3D-printed implant surface (3D-PDA) via the in situ polymerization method. Then the 3D-PDA implants' pro-osteogenesis capacity and the osseointegration performance were evaluated in comparison with the 3D group. The in vitro results revealed that the PDA coating modification increased the hydrophilicity of the implants, promoting the improvement of the adhesion, propagation, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the 3D-PDA implant improved osteointegration performance in vivo. The present study suggested that PDA coating might be a feasible strategy to optimize 3D-printed implant surfaces, making a preliminary research basis for the subsequent work to immobilize bioactive factors on the 3D-printed implant surface.

The Surface Characterisation of Fused Filament Fabricated (FFF) 3D Printed PEEK/Hydroxyapatite Composites

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer which has found increasing application in orthopaedics and has shown a lot of promise for 'made-to-measure' implants via additive manufacturing approaches. However, PEEK is bioinert and needs to undergo surface modification to make it at least osteoconductive to ensure a more rapid, improved, and stable fixation that will last longer in vivo. One approach to solving this issue is to modify PEEK with bioactive agents such as hydroxyapatite (HA). The work reported in this study demonstrates the direct 3D printing of PEEK/HA composites of up to 30 weight percent (wt%) HA using a Fused Filament Fabrication (FFF) approach. The surface characteristics and in vitro properties of the composite materials were investigated. X-ray diffraction revealed the samples to be semi-crystalline in nature, with X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealing HA materials were available in the uppermost surface of all the 3D printed samples. In vitro testing of the samples at 7 days demonstrated that the PEEK/HA composite surfaces supported the adherence and growth of viable U-2 OS osteoblast like cells. These results demonstrate that FFF can deliver bioactive HA on the surface of PEEK bio-composites in a one-step 3D printing process.

3D printing of PEEK and its composite to increase biointerfaces as a biomedical material- A review

Poly ether-ether-ketone (PEEK) is a polymer with better lignin biocompatibility than other polymers. It is good for biomedical engineering applications. This research summarises the outcomes of an evaluation conducted on PEEK material composites, such as cellular calcium hydroxyapatite (CHAp) for medical applications. Prospects of PEEK for medical implant are highlighted. Critical analysis and review on 3D printing of PEEK, CHAp and their biological macromolecular behaviours are presented. An electronic search was carried out on Scupos database, Google search and peer-reviewed papers published in the last ten years. Because of the extraordinary strength and biological behaviours of PEEK and its composite of CHAp, 3D-printed PEEK has several biomedical applications, and its biological macromolecular behaviour leads to health sustainability. This work highlights its biological macromolecular behaviours as a bone implant material and the optimum 3D printing process for PEEK and CHAp for medical applications. The current problems with printing PEEK and CHAp are investigated along with their possible uses. Possible solutions to improve the 3D printability of PEEK and CHAp are explained based on scientific mechanisms. This detailed report stands to benefit both scientific community and medical industry to enhance 3D printing concepts for PEEK and CHAp.

The Direct 3D Printing of Functional PEEK/Hydroxyapatite Composites via a Fused Filament Fabrication Approach

The manufacture of polyetheretherketone/hydroxyapatite (PEEK/HA) composites is seen as a viable approach to help enhance direct bone apposition in orthopaedic implants. A range of methods have been used to produce composites, including Selective Laser Sintering and injection moulding. Such techniques have drawbacks and lack flexibility to manufacture complex, custom-designed implants. 3D printing gets around many of the restraints and provides new opportunities for innovative solutions that are structurally suited to meet the needs of the patient. This work reports the direct 3D printing of extruded PEEK/HA composite filaments via a Fused Filament Fabrication (FFF) approach. In this work samples are 3D printed by a custom modified commercial printer Ultimaker 2+ (UM2+). SEM-EDX and µCT analyses show that HA particles are evenly distributed throughout the bulk and across the surface of the native 3D printed samples, with XRD highlighting up to 50% crystallinity and crystalline domains clearly observed in SEM and HR-TEM analyses. This highlights the favourable temperature conditions during 3D printing. The yield stress and ultimate tensile strength obtained for all the samples are comparable to human femoral cortical bone. The results show how FFF 3D printing of PEEK/HA composites up to 30 wt% HA can be achieved.

Review on 3D printing: Fight against COVID-19

The outbreak of coronavirus disease in 2019 (COVID-19) caused by the SARS-CoV-2 virus and its pandemic effects have created a demand for essential medical equipment. To date, there are no specific, clinically significant licensed drugs and vaccines available for COVID-19. Hence, mapping out COVID-19 problems and preventing the spread with relevant technology are very urgent. This study is a review of the work done till October, 2020 on solving COVID-19 with 3D printing. Many patients who need to be hospitalized because of COVID-19 can only survive on bio-macromolecules antiviral respiratory assistance and other medical devices. A bio-cellular face shield with relative comfortability made of bio-macromolecules polymerized polyvinyl chloride (BPVC) and other biomaterials are produced with 3D printers. Summarily, it was evident from this review study that additive manufacturing (AM) is a proffered technology for efficient production of an improved bio-macromolecules capable of significant COVID-19 test and personal protective equipment (PPE) to reduce the effect of COVID-19 on the world economy. Innovative AM applications can play an essential role to combat invisible killers (COVID-19) and its hydra-headed pandemic effects on humans, economics and society.

Preparation and application of chitosan biomaterials in dentistry

Chitosan is a biodegradable and biocompatible natural polysaccharide that has a wide range of applications in the field of dentistry due to its functional versatility and ease of access. Recent studies find that chitosan and its derivatives can be embedded in materials for dental adhesives, barrier membranes, bone replacement, tissue regeneration, and antimicrobial agent to better manage oral diseases. In this paper, we provide a comprehensive overview on the preparation, applications, and major breakthroughs of chitosan biomaterials. Furthermore, incorporation of chitosan additives for the modification and improvement of dental materials has been discussed in depth to promote more advanced chitosan-related research in the future.