Can 3D-Printed Bioactive Glasses Be the Future of Bone Tissue Engineering?

The Biological Properties of Co-Doped Monetite Are Influenced by Thermal Treatment

Calcium phosphates, notably monetite, are valued biomaterials for bone applications owing to their osteogenic properties and rapid uptake by bone cells. This study investigates the enhancement of these properties through Cobalt doping, which is known to induce hypoxia and promote bone cell differentiation. Heat treatments at 700°C, 900°C, and 1050°C are applied to both monetite and Cobalt-doped monetite, facilitating the development of purer, more crystalline phases with varied particle sizes and optimized cellular responses. Comprehensive physicochemical characterization through XRD, FTIR, Raman, SEM/EDS, and ASAP analyses shows significant phase transformations into pyrophosphate, influencing the materials' structural and functional attributes. When utilized to condition a culture medium for MC3T3-E1 cells, these materials demonstrate non-cytotoxic behavior and provoke specific gene responses associated with the osteoblastic phenotype, angiogenesis, adhesion, and extracellular matrix remodeling. Significantly, non-heat-treated Cobalt-doped Monetite retains properties advantageous for clinical applications such as dental and orthopedic implants, where lower processing temperatures are crucial. This attribute, combined with the material's straightforward production, highlights its practicality and potential cost-effectiveness. Further research is essential to assess the long-term safety and efficacy of these materials in clinical settings. Our findings underscore the promising role of Cobalt-doped Monetite in advancing bone repair and regeneration, setting the stage for future innovations in treating bone lesions, enhancing implant integration, and developing advanced prosthetic coatings within the field of tissue engineering.

Microcrystallization Effects in Borosilicate Bioactive Glasses: Controllable Release of Bioactive Elements and In Vitro Degradation Properties

Borosilicate bioactive glasses exhibit excellent bioactivity and degradation properties; however, they suffer from the rapid release of bioactive elements at the initial stage of their degradation. Excessive local concentrations (such as those of B) can affect cell proliferation. Moreover, the degradation and mineralization ability of these glasses deteriorate at the later stages. Aiming to balance the release of bioactive elements during the whole process, herein, a borosilicate bioactive glass 18SiO2-6Na2O-8K2O-8MgO-22CaO-2P2O5-36B2O3 (mol%) was prepared using the melting method. Further, the effects of microcrystallization on the release of bioactive elements and in vitro degradation were studied. Results show that after heat treatment at temperatures over 620 °C, multiple microcrystalline phases, including Ca2SiO4, CaB2O4, and CaMgB2O5, form in the glass. The glass samples heat-treated within the range of 620-640 °C undergo appropriate devitrification degrees, decelerating the rate of pH increase of the immersion solution during the initial stage in comparison to those treated at lower temperatures. This results in a more continuous release of all bioactive elements and allows better control of the overall degradation. Contrarily, the more extensive devitrification degrees of glass samples heat-treated at higher temperatures reverse the pH increase and degradation trends. Since bone marrow mesenchymal stem cells and mouse embryonic osteoblast cells are pH-sensitive, inducing a suitable degree of devitrification proved to favor cell viability and enhance the mineralization capacity. Thus, different microcrystallization degrees provide new approaches for controlling the degradation and release of bioactive elements, resulting in the simultaneous enhancement of biosafety and bioactivity.

Musculoskeletal Biomaterials: Stimulated and Synergized with Low Intensity Pulsed Ultrasound

Clinical biophysical stimulating strategies, which have significant effects on improving the function of organs or treating diseases by causing the salutary response of body, have shown many advantages, such as non-invasiveness, few side effects, and controllable treatment process. As a critical technique for stimulation, the low intensity pulsed ultrasound (LIPUS) has been explored in regulating osteogenesis, which has presented great promise in bone repair by delivering a combined effect with biomaterials. This review summarizes the musculoskeletal biomaterials that can be synergized with LIPUS for enhanced biomedical application, including bone regeneration, spinal fusion, osteonecrosis/osteolysis, cartilage repair, and nerve regeneration. Different types of biomaterials are categorized for summary and evaluation. In each subtype, the verified biological mechanisms are listed in a table or graphs to prove how LIPUS was effective in improving musculoskeletal tissue regeneration. Meanwhile, the acoustic excitation parameters of LIPUS that were promising to be effective for further musculoskeletal tissue engineering are discussed, as well as their limitations and some perspectives for future research. Overall, coupled with biomimetic scaffolds and platforms, LIPUS may be a powerful therapeutic approach to accelerate musculoskeletal tissue repair and even in other regenerative medicine applications.

Advanced Bioactive Glasses: The Newest Achievements and Breakthroughs in the Area

Bioactive glasses (BGs) are especially useful materials in soft and bone tissue engineering and even in dentistry. They can be the solution to many medical problems, and they have a huge role in the healing processes of bone fractures. Interestingly, they can also promote skin regeneration and wound healing. Bioactive glasses are able to attach to the bone tissues and form an apatite layer which further initiates the biomineralization process. The formed intermediate apatite layer makes a connection between the hard tissue and the bioactive glass material which results in faster healing without any complications or side effects. This review paper summarizes the most recent advancement in the preparation of diverse types of BGs, such as silicate-, borate- and phosphate-based bioactive glasses. We discuss their physical, chemical, and mechanical properties detailing how they affect their biological performances. In order to get a deeper insight into the state-of-the-art in this area, we also consider their medical applications, such as bone regeneration, wound care, and dental/bone implant coatings.

The Use of 3D Technology in the Management of Residual Asymmetry following Orthognathic Surgery: A Case Report

The purpose of this case report was to present the aesthetic result of the reconstruction of facial residual asymmetry after orthognathic surgery using a patient-specific three-dimensional (3D) mold and a custom-made polymethyl methacrylate implant. Through computer-aided design (CAD), the healthy contralateral side of the mandible was superimposed onto the side with the defect. Exocad Gallway (exocad GmbH, Darmstadt, Germany) was used to design the patient-specific implants (PSIs) of the right mandibular angle. Next, the implant mold was created using the Meshmixer software (Version 3.5, Autodesk Inc., San Rafael, CA, USA) and fabricated using additive manufacturing. During the surgical procedure, the patient-specific implant (PSI) was cast inside the resin mold using Simplex P bone cement (Stryker, Mahwah, NJ, USA). The implant was fixed using three screws. Combining both indirect (involving the dental laboratory) and direct (with surgical intervention) approaches, this innovative hybrid method, which incorporates both computer-aided design and additive manufacturing (AM), not only enhanced facial aesthetics, functional rehabilitation, and patient quality of life but also mitigated the potential risks linked to conventional grafting methods.

Additive Manufacturing of Polymer/Bioactive Glass Scaffolds for Regenerative Medicine: A Review

Tissue engineering (TE) is a branch of regenerative medicine with enormous potential to regenerate damaged tissues using synthetic grafts such as scaffolds. Polymers and bioactive glasses (BGs) are popular materials for scaffold production because of their tunable properties and ability to interact with the body for effective tissue regeneration. Due to their composition and amorphous structure, BGs possess a significant affinity with the recipient's tissue. Additive manufacturing (AM), a method that allows the creation of complex shapes and internal structures, is a promising approach for scaffold production. However, despite the promising results obtained so far, several challenges remain in the field of TE. One critical area for improvement is tailoring the mechanical properties of scaffolds to meet specific tissue requirements. In addition, achieving improved cell viability and controlled degradation of scaffolds is necessary to ensure successful tissue regeneration. This review provides a critical summary of the potential and limitations of polymer/BG scaffold production via AM covering extrusion-, lithography-, and laser-based 3D-printing techniques. The review highlights the importance of addressing the current challenges in TE to develop effective and reliable strategies for tissue regeneration.

Recent Advancements in Electrospun Chitin and Chitosan Nanofibers for Bone Tissue Engineering Applications

Treatment of large segmental bone loss caused by fractures, osteomyelitis, and non-union results in expenses of around USD 300,000 per case. Moreover, the worst-case scenario results in amputation in 10% to 14.5% of cases. Biomaterials, cells, and regulatory elements are employed in bone tissue engineering (BTE) to create biosynthetic bone grafts with effective functionalization that can aid in the restoration of such fractured bones, preventing amputation and alleviating expenses. Chitin (CT) and chitosan (CS) are two of the most prevalent natural biopolymers utilized in the fields of biomaterials and BTE. To offer the structural and biochemical cues for augmenting bone formation, CT and CS can be employed alone or in combination with other biomaterials in the form of nanofibers (NFs). When compared with several fabrication methods available to produce scaffolds, electrospinning is regarded as superior since it enables the development of nanostructured scaffolds utilizing biopolymers. Electrospun nanofibers (ENFs) offer unique characteristics, including morphological resemblance to the extracellular matrix, high surface-area-to-volume ratio, permeability, porosity, and stability. This review elaborates on the recent strategies employed utilizing CT and CS ENFs and their biocomposites in BTE. We also summarize their implementation in supporting and delivering an osteogenic response to treat critical bone defects and their perspectives on rejuvenation. The CT- and CS-based ENF composite biomaterials show promise as potential constructions for bone tissue creation.

Additive manufacturing of sustainable biomaterials for biomedical applications

Biopolymers are promising environmentally benign materials applicable in multifarious applications. They are especially favorable in implantable biomedical devices thanks to their excellent unique properties, including bioactivity, renewability, bioresorbability, biocompatibility, biodegradability and hydrophilicity. Additive manufacturing (AM) is a flexible and intricate manufacturing technology, which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems. Three-dimensional (3D) printing of these sustainable materials is applied in functional clinical settings including wound dressing, drug delivery systems, medical implants and tissue engineering. The present review highlights recent advancements in different types of biopolymers, such as proteins and polysaccharides, which are employed to develop different biomedical products by using extrusion, vat polymerization, laser and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional (4D) bioprinting techniques. This review also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds. This work also addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AM techniques. Ideally, there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas. We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future.

A triphasic biomimetic BMSC-loaded scaffold for osteochondral integrated regeneration in rabbits and pigs

Osteochondral tissue involves cartilage, calcified cartilage and subchondral bone. These tissues differ significantly in chemical compositions, structures, mechanical properties and cellular compositions. Therefore, the repairing materials face different osteochondral tissue regeneration needs and rates. In this study, we fabricated an osteochondral tissue-inspired triphasic material, which was composed of a poly(lactide-co-glycolide) (PLGA) scaffold loaded with fibrin hydrogel, bone marrow stromal cells (BMSCs) and transforming growth factor-β1 (TGF-β1) for cartilage tissue, a bilayer poly(L-lactide-co-caprolactone) (PLCL)-fibrous membrane loaded with chondroitin sulfate and bioactive glass, respectively, for calcified cartilage, and a 3D-printed calcium silicate ceramic scaffold for subchondral bone. The triphasic scaffold was press-fitted into the osteochondral defects in rabbit (cylindrical defects with a diameter of 4 mm and a depth of 4 mm) and minipig knee joints (cylindrical defects with a diameter of 10 mm and a depth of 6 mm). The μ-CT and histological analysis showed that the triphasic scaffold was partly degraded, and significantly promoted the regeneration of hyaline cartilage after they were implanted in vivo. The superficial cartilage showed good recovery and uniformity. The calcified cartilage layer (CCL) fibrous membrane was in favor of a better cartilage regeneration morphology, a continuous cartilage structure and less fibrocartilage tissue formation. The bone tissue grew into the material, while the CCL membrane limited bone overgrowth. The newly generated osteochondral tissues were well integrated with the surrounding tissues too.

A Review on Manufacturing Processes of Biocomposites Based on Poly(α-Esters) and Bioactive Glass Fillers for Bone Regeneration

The incorporation of bioactive and biocompatible fillers improve the bone cell adhesion, proliferation and differentiation, thus facilitating new bone tissue formation upon implantation. During these last 20 years, those biocomposites have been explored for making complex geometry devices likes screws or 3D porous scaffolds for the repair of bone defects. This review provides an overview of the current development of manufacturing process with synthetic biodegradable poly(α-ester)s reinforced with bioactive fillers for bone tissue engineering applications. Firstly, the properties of poly(α-ester), bioactive fillers, as well as their composites will be defined. Then, the different works based on these biocomposites will be classified according to their manufacturing process. New processing techniques, particularly additive manufacturing processes, open up a new range of possibilities. These techniques have shown the possibility to customize bone implants for each patient and even create scaffolds with a complex structure similar to bone. At the end of this manuscript, a contextualization exercise will be performed to identify the main issues of process/resorbable biocomposites combination identified in the literature and especially for resorbable load-bearing applications.

Gelatin and Bioactive Glass Composites for Tissue Engineering: A Review

Nano-/micron-sized bioactive glass (BG) particles are attractive candidates for both soft and hard tissue engineering. They can chemically bond to the host tissues, enhance new tissue formation, activate cell proliferation, stimulate the genetic expression of proteins, and trigger unique anti-bacterial, anti-inflammatory, and anti-cancer functionalities. Recently, composites based on biopolymers and BG particles have been developed with various state-of-the-art techniques for tissue engineering. Gelatin, a semi-synthetic biopolymer, has attracted the attention of researchers because it is derived from the most abundant protein in the body, viz., collagen. It is a polymer that can be dissolved in water and processed to acquire different configurations, such as hydrogels, fibers, films, and scaffolds. Searching "bioactive glass gelatin" in the tile on Scopus renders 80 highly relevant articles published in the last ~10 years, which signifies the importance of such composites. First, this review addresses the basic concepts of soft and hard tissue engineering, including the healing mechanisms and limitations ahead. Then, current knowledge on gelatin/BG composites including composition, processing and properties is summarized and discussed both for soft and hard tissue applications. This review explores physical, chemical and mechanical features and ion-release effects of such composites concerning osteogenic and angiogenic responses in vivo and in vitro. Additionally, recent developments of BG/gelatin composites using 3D/4D printing for tissue engineering are presented. Finally, the perspectives and current challenges in developing desirable composites for the regeneration of different tissues are outlined.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Clinical Applications of Poly-Methyl-Methacrylate in Neurosurgery: The In Vivo Cranial Bone Reconstruction

BACKGROUND

Biomaterials and biotechnology are becoming increasingly important fields in modern medicine. For cranial bone defects of various aetiologies, artificial materials, such as poly-methyl-methacrylate, are often used. We report our clinical experience with poly-methyl-methacrylate for a novel in vivo bone defect closure and artificial bone flap development in various neurosurgical operations.

METHODS

The experimental study included 12 patients at a single centre in 2018. They presented with cranial bone defects after various neurosurgical procedures, including tumour, traumatic brain injury and vascular pathologies. The patients underwent an in vivo bone reconstruction from poly-methyl-methacrylate, which was performed immediately after the tumour removal in the tumour group, whereas the trauma and vascular patients required a second surgery for cranial bone reconstruction due to the bone decompression. The artificial bone flap was modelled in vivo just before the skin closure. Clinical and surgical data were reviewed.

RESULTS

All patients had significant bony destruction or unusable bone flap. The tumour group included five patients with meningiomas destruction and the trauma group comprised four patients, all with severe traumatic brain injury. In the vascular group, there were three patients. The average modelling time for the artificial flap modelling was approximately 10 min. The convenient location of the bone defect enabled a relatively straightforward and fast reconstruction procedure. No deformations of flaps or other complications were encountered, except in one patient, who suffered a postoperative infection.

CONCLUSIONS

Poly-methyl-methacrylate can be used as a suitable material to deliver good cranioplasty cosmesis. It offers an optimal dural covering and brain protection and allows fast intraoperative reconstruction with excellent cosmetic effect during the one-stage procedure. The observations of our study support the use of poly-methyl-methacrylate for the ad hoc reconstruction of cranial bone defects.

Design Strategies and Biomimetic Approaches for Calcium Phosphate Scaffolds in Bone Tissue Regeneration

Bone is a complex biologic tissue, which is extremely relevant for various physiological functions, in addition to movement, organ protection, and weight bearing. The repair of critical size bone defects is a still unmet clinical need, and over the past decades, material scientists have been expending efforts to find effective technological solutions, based on the use of scaffolds. In this context, biomimetics which is intended as the ability of a scaffold to reproduce compositional and structural features of the host tissues, is increasingly considered as a guide for this purpose. However, the achievement of implants that mimic the very complex bone composition, multi-scale structure, and mechanics is still an open challenge. Indeed, despite the fact that calcium phosphates are widely recognized as elective biomaterials to fabricate regenerative bone scaffolds, their processing into 3D devices with suitable cell-instructing features is still prevented by insurmountable drawbacks. With respect to biomaterials science, new approaches maybe conceived to gain ground and promise for a substantial leap forward in this field. The present review provides an overview of physicochemical and structural features of bone tissue that are responsible for its biologic behavior. Moreover, relevant and recent technological approaches, also inspired by natural processes and structures, are described, which can be considered as a leverage for future development of next generation bioactive medical devices.