Calcium Phosphate-Based Biomaterials for Bone Repair

Alendronate as Bioactive Coating on Titanium Surfaces: An Investigation of CaP-Alendronate Interactions

The surface modification of dental implants plays an important role in establishing a successful interaction of the implant with the surrounding tissue, as the bioactivity and osseointegration properties are strongly dependent on the physicochemical properties of the implant surface. A surface coating with bioactive molecules that stimulate the formation of a mineral calcium phosphate (CaP) layer has a positive effect on the bone bonding process, as biomineralization is crucial for improving the osseointegration process and rapid bone ingrowth. In this work, the spontaneous deposition of calcium phosphate on the titanium surface covered with chemically stable and covalently bound alendronate molecules was investigated using an integrated experimental and theoretical approach. The initial nucleation of CaP was investigated using quantum chemical calculations at the density functional theory (DFT) level. Negative Gibbs free energies show a spontaneous nucleation of CaP on the biomolecule-covered titanium oxide surface. The deposition of calcium and phosphate ions on the alendronate-modified titanium oxide surface is governed by Ca2+-phosphonate (-PO3H) interactions and supported by hydrogen bonding between the phosphate group of CaP and the amino group of the alendronate molecule. The morphological and structural properties of CaP deposit were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy. This integrated experimental-theoretical study highlights the spontaneous formation of CaP on the alendronate-coated titanium surface, confirming the bioactivity ability of the alendronate coating. The results provide valuable guidance for the promising forthcoming advancements in the development of biomaterials and surface modification of dental implants.

Biomineral-Based Composite Materials in Regenerative Medicine

Regenerative medicine aims to address substantial defects by amplifying the body's natural regenerative abilities and preserving the health of tissues and organs. To achieve these goals, materials that can provide the spatial and biological support for cell proliferation and differentiation, as well as the micro-environment essential for the intended tissue, are needed. Scaffolds such as polymers and metallic materials provide three-dimensional structures for cells to attach to and grow in defects. These materials have limitations in terms of mechanical properties or biocompatibility. In contrast, biominerals are formed by living organisms through biomineralization, which also includes minerals created by replicating this process. Incorporating biominerals into conventional materials allows for enhanced strength, durability, and biocompatibility. Specifically, biominerals can improve the bond between the implant and tissue by mimicking the micro-environment. This enhances cell differentiation and tissue regeneration. Furthermore, biomineral composites have wound healing and antimicrobial properties, which can aid in wound repair. Additionally, biominerals can be engineered as drug carriers, which can efficiently deliver drugs to their intended targets, minimizing side effects and increasing therapeutic efficacy. This article examines the role of biominerals and their composite materials in regenerative medicine applications and discusses their properties, synthesis methods, and potential uses.

Hydroxyapatite/alginate/gellan gum inks with osteoconduction and osteogenic potential for bioprinting bone tissue analogues

There is a growing demand for engineered bone tissues custom-designed to match the patient-specific defect size and in vitro models for studying bone diseases and/or drug screening. Herein, we propose a bioprinted bone tissue construct using SaOs-2 cells within alginate/gellan gum/hydroxyapatite inks. Different ink formulations were developed with varying hydroxyapatite content and then evaluated for viscoelasticity, printability, biomineralization properties, post-printing viability, proliferation, metabolic activity, and osteogenic phenotype of SaOs-2-encapsulated cells. Results indicate that ink formulations exhibit non-Newtonian shear-thinning behaviour, maintaining shape integrity and structural stability post-printing. Ink mineralization rates increase with the hydroxyapatite content, rendering them suitable for bone defect strategies. Post-printed cells in the developed constructs remain live, spreading, and metabolically active but do not proliferate. Osteogenic gene and protein expression, both early and late, show upregulation at day 7 relative to day 1, followed by downregulation at day 14. Lower hydroxyapatite content inks demonstrate up to fourfold upregulation in genes and proteins at most time points. Additionally, these constructs release calcium and phosphate at levels conducive to mineralization. Overall, the tissue-engineered miniaturized constructs not only meet the criteria for early-stage bone defect/fracture regeneration but also serve as a promising platform for drug screening and evaluating potential therapeutic treatments.

In Vivo feature of the regenerative potential of chitosan and alginate based osteoplastic composites doped with calcium phosphates, zinc ions, and vitamin D2

PURPOSE

In vivo comparison of the regenerative potential of two calcium phosphate-biopolymer osteoplastic composites: а) based on alginate (Alg) and hydroxyapatite (HA) - Alg/HA/CS/Zn/D2, b) based on chitosan (CS) and brushite (DCPD) - CS/DCPD/D2.

MATERIALS AND METHODS

36 white male laboratory rats aged six months were used. A defect to the bone marrow canal in the middle of the femur diaphysis was made with a dental bur of 2 mm. The bone defect healed under the blood clot (control) in the different animal groups and was filled with Alg/HA/CS/Zn/D2 and CS/DCPD/D2. The regeneration of the bone defect was studied on the 30th, 90th, and 140th days by computer tomography (CT).

RESULTS

On the 30th day, all groups' implantation site optical density (OD) was significantly lower than that of the adjacent maternal bone (MB). Intensity of bone formation for Alg/HA/CS/Zn/D2 exceeds CS/DCPD/D2. On the 90th day, the bone trauma site OD with Alg/HA/CS/Zn/D2 (1725.4 ± 86 HU) and CS/DCPD/D2 (1484.9 ± 69 HU) exceeded the OD of the control (942.5 ± 55 HU). On the 140th day, the OD of Alg/HA/CS/Zn/D2 and CS/DCPD/D2 implantation sites was higher than Control and MB OD. Visually, the area of the past injury with the Alg/HA/CS/Zn/D2 could be detected only by the presence of an endosteal bone callus and in the case of CS/DCPD/D2 - by the shadow of the remaining biomaterial in the bone marrow canal.

CONCLUSIONS

According to CT data, Alg/HA/CS/Zn/D2 and CS/DCPD/D2 contribute to the complete healing of the femoral diaphysis defect in 140 days, but the regenerative potential of Alg/HA/CS/Zn/D2 from 30 days to 140 days is higher than CS/DCPD/D2 biomaterial.

Reconstruction of Craniomaxillofacial Bone Defects with 3D-Printed Bioceramic Implants: Scoping Review and Clinical Case Series

Reconstruction of craniomaxillofacial bone defects using 3D-printed hydroxyapatite (HA) bioceramic patient-specific implants (PSIs) is a new technique with great potential. This study aimed to investigate the advantages, disadvantages, and clinical outcomes of these implants in craniomaxillofacial surgeries. The PubMed and Embase databases were searched for patients with craniomaxillofacial bone defects treated with bioceramic PSIs. Clinical outcomes such as biocompatibility, biomechanical properties, and aesthetics were evaluated and compared to those of commonly used titanium or poly-ether-ether-ketone (PEEK) implants and autologous bone grafts. Two clinical cases are presented to illustrate the surgical procedure and clinical outcomes of HA bioceramic PSIs. Literature review showed better a biocompatibility of HA PSIs than titanium and PEEK. The initial biomechanical properties were inferior to those of autologous bone grafts, PEEK, and titanium but improved when integrated. Satisfactory aesthetic results were found in our two clinical cases with good stability and absence of bone resorption or infection. Radiological signs of osteogenesis were observed in the two clinical cases six months postoperatively. HA bioceramic PSIs have excellent biocompatible properties and imitate natural bone biomechanically and radiologically. They are a well-suited alternative for conventional biomaterials in the reconstruction of load-sharing bone defects in the craniomaxillofacial region.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces

Block copolymer (BCP) surfaces permit an exquisite level of nanoscale control in biomolecular assemblies solely based on self-assembly. Owing to this, BCP-based biomolecular assembly represents a much-needed, new paradigm for creating nanobiosensors and nanobiomaterials without the need for costly and time-consuming fabrication steps. Research endeavors in the BCP nanobiotechnology field have led to stimulating results that can promote our current understanding of biomolecular interactions at a solid interface to the never-explored size regimes comparable to individual biomolecules. Encouraging research outcomes have also been reported for the stability and activity of biomolecules bound on BCP thin film surfaces. A wide range of single and multicomponent biomolecules and BCP systems has been assessed to substantiate the potential utility in practical applications as next-generation nanobiosensors, nanobiodevices, and biomaterials. To this end, this Review highlights pioneering research efforts made in the BCP nanobiotechnology area. The discussions will be focused on those works particularly pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties unique to nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, and specific examples in biosensing. Systems involving the incorporation of biomolecules as one of the blocks in BCPs, i.e., DNA-BCP hybrids, protein-BCP conjugates, and isolated BCP micelles of bioligand carriers used in drug delivery, are outside of the scope of this Review. Looking ahead, there awaits plenty of exciting research opportunities to advance the research field of BCP nanobiotechnology by capitalizing on the fundamental groundwork laid so far for the biomolecular interactions on BCP surfaces. In order to better guide the path forward, key fundamental questions yet to be addressed by the field are identified. In addition, future research directions of BCP nanobiotechnology are contemplated in the concluding section of this Review.

Biomineralization of Polyelectrolyte-Functionalized Electrospun Fibers: Optimization and In Vitro Validation for Bone Applications

In recent years, polyelectrolytes have been successfully used as an alternative to non-collagenous proteins to promote interfibrillar biomineralization, to reproduce the spatial intercalation of mineral phases among collagen fibrils, and to design bioinspired scaffolds for hard tissue regeneration. Herein, hybrid nanofibers were fabricated via electrospinning, by using a mixture of Poly ɛ-caprolactone (PCL) and cationic cellulose derivatives, i.e., cellulose-bearing imidazolium tosylate (CIMD). The obtained fibers were self-assembled with Sodium Alginate (SA) by polyelectrolyte interactions with CIMD onto the fiber surface and, then, treated with simulated body fluid (SBF) to promote the precipitation of calcium phosphate (CaP) deposits. FTIR analysis confirmed the presence of SA and CaP, while SEM equipped with EDX analysis mapped the calcium phosphate constituent elements, estimating an average Ca/P ratio of about 1.33-falling in the range of biological apatites. Moreover, in vitro studies have confirmed the good response of mesenchymal cells (hMSCs) on biomineralized samples, since day 3, with a significant improvement in the presence of SA, due to the interaction of SA with CaP deposits. More interestingly, after a decay of metabolic activity on day 7, a relevant increase in cell proliferation can be recognized, in agreement with the beginning of the differentiation phase, confirmed by ALP results. Antibacterial tests performed by using different bacteria populations confirmed that nanofibers with an SA-CIMD complex show an optimal inhibitory response against S. mutans, S. aureus, and E. coli, with no significant decay due to the effect of CaP, in comparison with non-biomineralized controls. All these data suggest a promising use of these biomineralized fibers as bioinspired membranes with efficient antimicrobial and osteoconductive cues suitable to support bone healing/regeneration.

Impact of ZrO2 Content on the Formation of Sr-Enriched Phosphates in Al2O3/ZrO2 Nanocomposites for Bone Tissue Engineering

This study investigates the profound impact of the ZrO2 inclusion volume on the characteristics of Al2O3/ZrO2 nanocomposites, particularly influencing the formation of calcium phosphates on the surface. This research, aimed at advancing tissue engineering, prepared nanocomposites with 5, 10, and 15 vol% ZrO2, subjecting them to chemical surface treatment for enhanced calcium phosphate deposition sites. Biomimetic coating with Sr-enriched simulated body fluid (SBF) further enhanced the bioactivity of nanocomposites. While the ZrO2 concentration heightened the oxygen availability on nanocomposite surfaces, the quantity of Sr-containing phosphate was comparatively less influenced than the formation of calcium phosphate phases. Notably, the coated nanocomposites exhibited a high cell viability and no toxicity, signifying their potential in bone tissue engineering. Overall, these findings contribute to the development of regenerative biomaterials, holding promise for enhancing bone regeneration therapies.

An innovative 3D hydroxyapatite patient-specific implant for maxillofacial bone reconstruction: A case series of 13 patients

The study aimed to evaluate and discuss the use of an innovative PSI made of porous hydroxyapatite, with interconnected porosity promoting osteointegration, called MyBone Custom® implant (MBCI), for maxillofacial bone reconstruction. A multicentric cohort of 13 patients underwent maxillofacial bone reconstruction surgery using MBCIs for various applications, from genioplasty to orbital floor reconstruction, including zygomatic and mandibular bone reconstruction, both for segmental defects and bone augmentation. The mean follow-up period was 9 months (1-22 months). No infections, displacements, or postoperative fractures were reported. Perioperative modifications of the MBCIs were possible when necessary. Additionally, surgeons reported significant time saved during surgery. For patients with postoperative CT scans, osteointegration signs were visible at the 6-month postoperative follow-up control, and continuous osteointegration was observed after 1 year. The advantages and disadvantages compared with current techniques used are discussed. MBCIs offer new bone reconstruction possibilities with long-term perspectives, while precluding the drawbacks of titanium and PEEK. The low level of postoperative complications associated with the high osteointegration potential of MBCIs paves the way to more extensive use of this new hydroxyapatite PSI in maxillofacial bone reconstruction.

Inorganic Phosphate as "Bioenergetic Messenger" Triggers M2-Type Macrophage Polarization

The effects of calcium phosphate (CaP) materials on macrophage polarization state vary with their physicochemical properties. The study aims to elucidate the impact of phosphate ion-mediated energy metabolism on M2 macrophage polarization and the corresponding regulatory mechanism. The phosphate ions released from CaP ceramic as bioenergetic factor is identified; its concentration is closely associated with the polarized state. After being taken up by the sodium-dependent phosphate transporter 1, extracellular phosphate ions produce energy via oxidative phosphorylation by facilitating tricarboxylic acid flux, thereby contributing to M2 macrophage polarization. Further mechanistic analysis reveals that the elevation of the bioenergetic basis can drive macrophage M2 polarization via the AMP-activated protein kinase-mammalian target of rapamycin (AMPK-mTOR) axis. Another regulatory effect is that of the adenosine triphosphate (ATP), a signaling molecule. Intracellular ATP is released into the extracellular space and degraded to adenosine, which serves as a signaling molecule through the A2b adenosine receptor to activate the cyclic adenosine monophosphate (cAMP) pathway, thereby promoting M2 macrophage polarization. Overall, these findings may transform the existing knowledge on cell metabolism and energy homeostasis from bystanders to pivotal factors guiding M2 macrophage polarization and have implications for the future design of biomimetic CaP scaffolds.

Efficacy of photobiomodulation using diode laser 650 nm combined with nano-cellulose and nano-amorphous calcium phosphate in bone healing of rabbit tibial defects assessed by H&E staining and computed tomography

BACKGROUND

The purpose of the current study was to evaluate the effect of Diode LLLT 650 nm, TEMPO oxidized Nano-fibrillated cellulose mixed with Nano-Amorphous calcium phosphate, and their combination on bone healing in rabbit tibia using H&E staining and computed tomography.

METHODS

Eighteen adult male New Zealand rabbits were selected, two circular bone defects were created in each tibia, resulting in four bony defects in each rabbit, representing the four tested groups; group A (negative control), group B (filled with mineralized nano-cellulose), group C (combination), group D (laser). Animals were euthanized after two weeks and one month, defects were assessed by CT for bone density, then histological samples were examined by H&E stain.

RESULTS

In both evaluation periods, group D recorded the greatest mean area percent of new bone formation and bone density, followed by group A, while group C recorded the lowest value. Groups A and D showed full closure of the defects, while groups B and C showed partial defect closure with retained bone graft material. H&E and CT showed that Laser group had the best results of defects healing, bone density and new bone formation, followed by the negative control group.

CONCLUSIONS

Diode laser 650nm photobiomodulation significantly improved bone defects healing. Mineralized nano-cellulose experimental bone substitute material showed a delayed effect in bone healing and graft material resorption. The combination of LLLT with the graft material had no positive outcome on bone defect healing.

Optimization of a tunable process for rapid production of calcium phosphate microparticles using a droplet-based microfluidic platform

Calcium phosphate (CaP) biomaterials are amongst the most widely used synthetic bone graft substitutes, owing to their chemical similarities to the mineral part of bone matrix and off-the-shelf availability. However, their ability to regenerate bone in critical-sized bone defects has remained inferior to the gold standard autologous bone. Hence, there is a need for methods that can be employed to efficiently produce CaPs with different properties, enabling the screening and consequent fine-tuning of the properties of CaPs towards effective bone regeneration. To this end, we propose the use of droplet microfluidics for rapid production of a variety of CaP microparticles. Particularly, this study aims to optimize the steps of a droplet microfluidic-based production process, including droplet generation, in-droplet CaP synthesis, purification and sintering, in order to obtain a library of CaP microparticles with fine-tuned properties. The results showed that size-controlled, monodisperse water-in-oil microdroplets containing calcium- and phosphate-rich solutions can be produced using a flow-focusing droplet-generator microfluidic chip. We optimized synthesis protocols based on in-droplet mineralization to obtain a range of CaP microparticles without and with inorganic additives. This was achieved by adjusting synthesis parameters, such as precursor concentration, pH value, and aging time, and applying heat treatment. In addition, our results indicated that the synthesis and fabrication parameters of CaPs in this method can alter the microstructure and the degradation behavior of CaPs. Overall, the results highlight the potential of the droplet microfluidic platform for engineering CaP microparticle biomaterials with fine-tuned properties.

Triple-Hybrid BioScaffold Based on Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates: Preparation, Characterization of Physiochemical and Biopharmaceutical Properties

Bioscaffolds, which promote cell regeneration and restore tissues' functions, have emerged as significant need in clinic. The hybrid of several biomaterials in a bioscaffold renders clinically advanced and relevant properties for applications yet add challenges in cost efficiency, production, and clinical investigation. This study proposes a facile and sustainable method to formulate a triple-hybrid bioscaffold based on Vietnamese cocoon origin Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates (nano-BCP) that can be easily molded, has high porosity (55-80%), and swelling capacity that facilitates cell proliferation and nutrient diffusion. Notably, their mechanical properties, in particular compressive strength, can easily be tuned in a range from 50 - 200 kPa by changing the amount of nano-BCP addition, which is comparable to the successful precedents for productive cell regeneration. The latter parts investigate the biopharmaceutical properties of a representative bioscaffold, including drug loading and release studies with two kinds of active compounds, salmon calcitonin and methylprednisolone. Furthermore, the bioscaffold is highly biocompatible as the results of hemocompatibility and hemostasis tests, as well as ovo chick chorioallantoic membrane investigation. The findings of the study suggest the triple-hybrid scaffold as a promising platform for multi-functional drug delivery and bone defect repair.

Surface-modified deproteinized human demineralized tooth matrix for bone regeneration: physicochemical characterization and osteoblast cell biocompatibility

Tooth presents an intriguing option as a bone graft due to its compositional similarity to bone. However, the deproteinized human demineralized tooth matrix (dpDTM), developed to overcome the limited availability of autologous tooth grafts, has suboptimal pore size and surface roughness. This study aimed to fabricate a surface-modified dpDTM using acid etching and collagen coating, followed by in vitro evaluation of physicochemical and biological properties. The dpDTM was modified into two protocols: Acid-modified dpDTM (A-dpDTM) and collagen-modified dpDTM (C-dpDTM). Results demonstrated that A-dpDTM and C-dpDTM had increased pore sizes and rougher surfaces compared to dpDTM. Collagen immobilization was evidenced by nitrogen presence exclusively in C-dpDTM. All groups had a Ca/P molar ratio of 1.67 and hydroxyapatite as the sole constituent, with 65-67% crystallinity. Degradation rates significantly increased to 30% and 20% for C-dpDTM and A-dpDTM, respectively, compared to 10% for dpDTM after 120 days. Cumulative collagen release of C-dpDTM on Day 30 was 45.16 µg/ml. Osteoblasts attachment and proliferation were enhanced on all scaffolds, especially C-dpDTM, which displayed the highest proliferation and differentiation rates. In conclusion, surface modified of dpDTM, including A-dpDTM and C-dpDTM, significantly enhances bioactivity by altering surface properties and promoting osteoblast activity, thereby demonstrating promise for bone regeneration applications.

Effects of void defects on the mechanical properties of biphasic calcium phosphate nanoparticles: A molecular dynamics investigation

Porous biphasic calcium phosphate (BCP) ceramics are widely used in bone tissue engineering, and the mechanical properties of BCP implants must be reliable. However, the effects of pore structure (e.g., shape and size) on the mechanical properties are not well understood. In this study, we used molecular dynamics simulations to investigate the influence of pore shape and size on the mechanical behavior of BCP nanoparticles. BCP void models with cylindrical and cuboid pores ranging from 2 to 16 nm in diameter were constructed, and the elastic moduli were calculated. In addition, uniaxial tensile and compressive tests were performed on the models. We found that the pore size had a more significant impact on the mechanical properties of BCP than pore shape. Further, the elastic moduli decreased nonlinearly with increasing pore size. In addition, the tensile and compressive strength also decreased with the increase in pore size, but the ductility improved. Furthermore, deformation and fracture were more likely to occur near the pores and at the phase interfaces as a result of high atomic local strain in the calcium-deficient hydroxyapatite area. The results of this work reveal the effects of pore parameters on the mechanical properties of porous BCP at the nanometer level, which may aid the design of improved porous and multiphase CaP-based biomaterials for bone regeneration.

Lamellar Septa-like Structured Carbonate Apatite Scaffolds with Layer-by-Layer Fracture Behavior for Bone Regeneration

Generally, ceramics are brittle, and porosity is inversely correlated with strength, which is one of the challenges of ceramic scaffolds. Here, we demonstrate that lamellar septum-like carbonate apatite scaffolds have the potential to overcome these challenges. They were fabricated by exploiting the cellular structure of the cuttlebone, removing the organic components from the cuttlebone, and performing hydrothermal treatment. Scanning electron microscopy revealed that the scaffolds had a cellular structure with walls between lamellar septa. The interwall and interseptal sizes were 80-180 and 300-500 μm, respectively. The size of the region enclosed by the walls and septa coincided with the macropore size detected by mercury intrusion porosimetry. Although the scaffold porosity was extremely high (93.2%), the scaffold could be handled without disintegration. The compressive stress-strain curve demonstrated that the scaffolds showed layer-by-layer fracture behavior, which seemed beneficial for avoiding catastrophic failure under impact. When the scaffolds were implanted into rabbit femurs, new bone and blood vessels formed within the scaffold cells at 4 weeks. At 12 weeks, the scaffolds were almost entirely replaced with new bone. Thus, the lamellar septum-like cellular-structured carbonate apatite is a promising scaffold for achieving early bone regeneration and compression resistance.

Amorphous, Carbonated Calcium Phosphate and Biopolymer-Composite-Coated Si3N4/MWCNTs as Potential Novel Implant Materials

A biodegradable amorphous carbonated calcium phosphate (caCP)-incorporated polycaprolactone (PCL) composite layer was successfully deposited by a spin coater. In this specific coating, the PCL acts as a bioadhesive, since it provides a better adherence of the coatings to the substrate compared to powder coatings. The caCP-PCL coatings were deposited and formed thin layers on the surface of a Si3N4-3 wt% MWCNT (multiwalled carbon nanotube) substrate, which is an emerging type of implant material in the biomedical field. The composite coatings were examined regarding their morphology, structure and biological performance. The biocompatibility of the samples was tested in vitro with MC3T3-E1 preosteoblast cells. Owing to the caCP-PCL thin layer, the cell viability values were considerably increased compared to the substrate material. The ALP and LDH tests showed numerous living cells on the investrigated coatings. The morphology of the MC3T3-E1 cells was examined by fluorescent staining (calcein and DAPI) and scanning electron microscopy, both of which revealed a well-spread, adhered and confluent monolayer of cells. All performed biocompatibility tests were positive and indicated the applicability of the deposited thin composite layers as possible candidates for orthopaedic implants for an extended period.

Consolidation of Spray-Dried Amorphous Calcium Phosphate by Ultrafast Compression: Chemical and Structural Overview

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, these aims can be achieved by the choice of amorphous calcium phosphates (ACPs). Because of their metastable property, these compounds are however to-date seldom used in bulk form. In this work, we used a non-conventional "cold sintering" approach based on ultrafast low-pressure RT compaction to successfully consolidate ACP pellets while preserving their amorphous nature (XRD). Complementary spectroscopic analyses (FTIR, Raman, solid-state NMR) and thermal analyses showed that the starting powder underwent slight physicochemical modifications, with a partial loss of water and local change in the HPO42- ion environment. The creation of an open porous structure, which is especially adapted for non-load bearing bone defects, was also observed. Moreover, the pellets obtained exhibited sufficient mechanical resistance allowing for manipulation, surgical placement and eventual cutting/reshaping in the operation room. Three-dimensional porous scaffolds of cold-sintered reactive ACP, fabricated through this low-energy, ultrafast consolidation process, show promise toward the development of highly bioactive and tailorable biomaterials for bone regeneration, also permitting combinations with various thermosensitive drugs.

Titanium Dioxide Promotes the Growth and Aggregation of Calcium Phosphate and Monosodium Urate Mixed Crystals

The increased utilization of titanium dioxide (TiO2) nanoparticles (TNPs) in various industrial and consumer products has raised concerns regarding its harmful effect due to its accumulation within the different systems of the human body. Here, we focused on the influence of TNPs on the growth and aggregation of two crucial crystalline substances, calcium phosphate (CaP) and monosodium urate (MSU), particularly its implications in gout disease. In this study, we adopted microscopic techniques and generated kinetic models to examine the interactions between TNPs, CaP and MSU, and crystallization, under controlled laboratory conditions. Our findings reveal that TNPs not only facilitate the growth of these crystals but also promote their co-aggregations. Crystal dissolution kinetics also exhibit that an increase in TNPs concentration corresponds to a reduction in the dissolution rate of CaP and MSU crystals in presence of the dissoluting agent hydroxycitrate (Hcit). These observations suggest that TNPs can stabilize CaP+MSU mixed crystals, which underscores the significance of TNPs' exposure in the pathogenesis of gout disease.

Bone-like apatite formation in biocompatible phosphate-crosslinked bacterial cellulose-based hydrogels for bone tissue engineering applications

Addressing major bone injuries is a challenge in bone regeneration, necessitating innovative 3D hydrogel-based therapeutic approaches to enhance scaffold properties for better bioactivity. Bacterial cellulose (BC) is an excellent scaffold for bone tissue engineering due to its biocompatibility, high porosity, substantial surface area, and remarkable mechanical strength. However, its practical application is limited due to a lack of inherent osteogenic activity and biomineralization ability. In this study, we synthesized bone-like apatite in biocompatible BC hydrogel by introducing phosphate groups. Hydrogels were prepared using fibrous BC, acrylamide (AM), and bis [2-methacryloyloxy] ethyl phosphate (BMEP) as a crosslinker through free radical polymerization (P-BC-PAM). P-BC-PAM hydrogels exhibited outstanding compressive mechanical properties, highly interconnected porous structures, good swelling, and biodegradable properties. BMEP content significantly influenced the physicochemical and biological properties of the hydrogels. Increasing BMEP content enhanced the fibrous structure, porosity from 85.1 % to 89.5 %, and compressive mechanical strength. The optimized hydrogel (2.0P-BC-PAM) displayed maximum compressive stress, toughness, and elastic modulus at 75 % strain: 221 ± 0.08 kPa, 24,674.2 ± 978 kPa, and 11 ± 0.47 kPa, respectively. P-BC-PAM hydrogels underwent biomineralization in simulated body fluid (SBF) for 14 days, forming bone-like apatite with a Ca/P ratio of 1.75, similar to hydroxyapatite. Confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM), this suggests their potential as scaffolds for bone tissue engineering. MC3T3-E1 osteoblast cells effectively attached and proliferated on P-BC-PAM. In summary, this study contributes insights into developing phosphate-functionalized BC-based hydrogels with potential applications in bone tissue engineering.

Cross Talk Between Cells and the Current Bioceramics in Bone Regeneration: A Comprehensive Review

The conventional approach for addressing bone defects and stubborn non-unions typically involves the use of autogenous bone grafts. Nevertheless, obtaining these grafts can be challenging, and the procedure can lead to significant morbidity. Three primary treatment strategies for managing bone defects and non-unions prove resistant to conventional treatments: synthetic bone graft substitutes (BGS), a combination of BGS with bioactive molecules, and the use of BGS in conjunction with stem cells. In the realm of synthetic BGS, a multitude of biomaterials have emerged for creating scaffolds in bone tissue engineering (TE). These materials encompass biometals like titanium, iron, magnesium, and zinc, as well as bioceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP). Bone TE scaffolds serve as temporary implants, fostering tissue ingrowth and the regeneration of new bone. They are meticulously designed to enhance bone healing by optimizing geometric, mechanical, and biological properties. These scaffolds undergo continual remodeling facilitated by bone cells like osteoblasts and osteoclasts. Through various signaling pathways, stem cells and bone cells work together to regulate bone regeneration when a portion of bone is damaged or deformed. By targeting signaling pathways, bone TE can improve bone defects through effective therapies. This review provided insights into the interplay between cells and the current state of bioceramics in the context of bone regeneration.

Model-Based Design to Enhance Neotissue Formation in Additively Manufactured Calcium-Phosphate-Based Scaffolds

In biomaterial-based bone tissue engineering, optimizing scaffold structure and composition remains an active field of research. Additive manufacturing has enabled the production of custom designs in a variety of materials. This study aims to improve the design of calcium-phosphate-based additively manufactured scaffolds, the material of choice in oral bone regeneration, by using a combination of in silico and in vitro tools. Computer models are increasingly used to assist in design optimization by providing a rational way of merging different requirements into a single design. The starting point for this study was an in-house developed in silico model describing the in vitro formation of neotissue, i.e., cells and the extracellular matrix they produced. The level set method was applied to simulate the interface between the neotissue and the void space inside the scaffold pores. In order to calibrate the model, a custom disk-shaped scaffold was produced with prismatic canals of different geometries (circle, hexagon, square, triangle) and inner diameters (0.5 mm, 0.7 mm, 1 mm, 2 mm). The disks were produced with three biomaterials (hydroxyapatite, tricalcium phosphate, and a blend of both). After seeding with skeletal progenitor cells and a cell culture for up to 21 days, the extent of neotissue growth in the disks' canals was analyzed using fluorescence microscopy. The results clearly demonstrated that in the presence of calcium-phosphate-based materials, the curvature-based growth principle was maintained. Bayesian optimization was used to determine the model parameters for the different biomaterials used. Subsequently, the calibrated model was used to predict neotissue growth in a 3D gyroid structure. The predicted results were in line with the experimentally obtained ones, demonstrating the potential of the calibrated model to be used as a tool in the design and optimization of 3D-printed calcium-phosphate-based biomaterials for bone regeneration.

The roles of calcium signaling and calcium deposition in microbial multicellularity

Calcium signaling is an essential mediator of signal-controlling gene expression in most developmental systems. In addition, calcium has established extracellular functions as a structural component of biogenic minerals found in complex tissues. In bacteria, the formation of calcium carbonate structures is associated with complex colony morphology. Genes promoting the formation of biogenic minerals are essential for proper biofilm development and protection against antimicrobial solutes and toxins. Here we review recent findings on the role of calcium and calcium signaling as emerging regulators of biofilm formation in beneficial bacteria, as well as essential mediators of biofilm formation and virulence in human pathogens. The presented analysis concludes that the new understanding of calcium signaling may help to improve the performance of beneficial strains for sustainable agriculture, microbiome manipulation, and sustainable construction. Unraveling the roles of calcium may also promote the development of novel therapies against biofilm infections that target calcium uptake, calcium sensors, and calcium carbonate deposition.

Synthesis Technology of Magnesium-Doped Nanometer Hydroxyapatite: A Review

Ion substitution techniques for nanoparticles have become an important neighborhood of biomedical engineering and have led to the development of innovative bioactive materials for health systems. Magnesium-doped nanohydroxyapatite (Mg-nHA) has good bone conductivity, biological activity, flexural strength, and fracture toughness due to particle doping technology, making it an ideal candidate material for biomedical applications. In this Review, we have systematically presented the synthesis methods of Mg-nHA and their application in the field of biomedical science and highlighted the pros and cons of each method. Finally, some future prospects for this important neighborhood are proposed. The purpose of this Review is to provide readers with an understanding of this new field of research on bioactive materials with innovative functions and systematically introduce the latest technologies for obtaining uniform, continuous, and morphologically diverse Mg-nHA.

Towards Polycaprolactone-Based Scaffolds for Alveolar Bone Tissue Engineering: A Biomimetic Approach in a 3D Printing Technique

The alveolar bone is a unique type of bone, and the goal of bone tissue engineering (BTE) is to develop methods to facilitate its regeneration. Currently, an emerging trend involves the fabrication of polycaprolactone (PCL)-based scaffolds using a three-dimensional (3D) printing technique to enhance an osteoconductive architecture. These scaffolds are further modified with hydroxyapatite (HA), type I collagen (CGI), or chitosan (CS) to impart high osteoinductive potential. In conjunction with cell therapy, these scaffolds may serve as an appealing alternative to bone autografts. This review discusses research gaps in the designing of 3D-printed PCL-based scaffolds from a biomimetic perspective. The article begins with a systematic analysis of biological mineralisation (biomineralisation) and ossification to optimise the scaffold's structural, mechanical, degradation, and surface properties. This scaffold-designing strategy lays the groundwork for developing a research pathway that spans fundamental principles such as molecular dynamics (MD) simulations and fabrication techniques. Ultimately, this paves the way for systematic in vitro and in vivo studies, leading to potential clinical applications.

Spectral Analysis of Strontium-Doped Calcium Phosphate/Chitosan Composite Films

Strontium-doped calcium phosphate/chitosan films were synthetized on silicon substrates using the radio-frequency magnetron sputtering technique and the matrix-assisted pulsed laser evaporation technique. The deposition conditions associated with the radio-frequency magnetron sputtering discharge, in particular, include the high temperature at the substrate, which promotes the formation of strontium-doped tetra calcium phosphate layers. The physical and chemical processes associated with the deposition of chitosan on strontium-doped calcium phosphate layers were investigated using Fourier Transform Infrared Spectroscopy, Energy Dispersive X-ray Spectroscopy, and Scanning Electron Microscopy. Mass spectrometry coupled with laser induced ablation of the composite films proved to be a useful tool in the detection of the molecular ions characteristic to chitosan chemical structure.

Tetracalcium Phosphate Biocement Hardened with a Mixture of Phytic Acid-Phytase in the Healing Process of Osteochondral Defects in Sheep

Hyaline articular cartilage has unique physiological, biological, and biomechanical properties with very limited self-healing ability, which makes the process of cartilage regeneration extremely difficult. Therefore, research is currently focused on finding new and potentially better treatment options. The main objective of this in vivo study was to evaluate a novel biocement CX consisting of tetracalcium phosphate-monetit biocement hardened with a phytic acid-phytase mixture for the regeneration of osteochondral defects in sheep. The results were compared with tetracalcium phosphate-monetit biocement with classic fast-setting cement systems and untreated defects. After 6 months, the animals were sacrificed, and the samples were evaluated using macroscopic and histologic methods as well as X-ray, CT, and MR-imaging techniques. In contrast to the formation of fibrous or fibrocartilaginous tissue on the untreated side, treatment with biocements resulted in the formation of tissue with a dominant hyaline cartilage structure, although fine fibres were present (p < 0.001). There were no signs of pathomorphological changes or inflammation. Continuous formation of subchondral bone and hyaline cartilage layers was present even though residual biocement was observed in the trabecular bone. We consider biocement CX to be highly biocompatible and suitable for the treatment of osteochondral defects.

Mineralized Microgels via Electrohydrodynamic Atomization: Optimization and In Vitro Model for Dentin-Pulp Complex

There is growing interest in the use of micro-sized hydrogels, including bioactive signals, as efficient platforms for tissue regeneration because they are able to mimic cell niche structure and selected functionalities. Herein, it is proposed to optimize bioactive composite microgels via electrohydrodynamic atomization (EHDA) to regenerate the dentin-pulp complex. The addition of disodium phosphate (Na2HPO4) salts as mineral precursors triggered an in situ reaction with divalent ions in solution, thus promoting the encapsulation of different amounts of apatite-like phases. Morphological analysis via image analysis of optical images confirmed a narrow distribution of perfectly rounded particles, with an average diameter ranging from 223 ± 18 μm to 502 ± 64 μm as a function of mineral content and process parameters used. FTIR, TEM, and EDAX analyses confirmed the formation of calcium phosphates with a characteristic Ca/P ratio close to 1.67 and a needle-like crystal shape. In vitro studies-using dental pulp stem cells (DPSCs) in crown sections of natural teeth slices-showed an increase in cell viability until 14 days, recording a decay of proliferation at 21 days, independent on the mineral amount, suggesting that differentiation is started, as confirmed by the increase of ALP activity at 14 days. In this view, mineralized microgels could be successfully used to support in vitro osteogenesis, working as an interesting model to study dental tissue regeneration.

Advancing Dentistry through Bioprinting: Personalization of Oral Tissues

Despite significant advancements in dental tissue restoration and the use of prostheses for addressing tooth loss, the prevailing clinical approaches remain somewhat inadequate for replicating native dental tissue characteristics. The emergence of three-dimensional (3D) bioprinting offers a promising innovation within the fields of regenerative medicine and tissue engineering. This technology offers notable precision and efficiency, thereby introducing a fresh avenue for tissue regeneration. Unlike the traditional framework encompassing scaffolds, cells, and signaling factors, 3D bioprinting constitutes a contemporary addition to the arsenal of tissue engineering tools. The ongoing shift from conventional dentistry to a more personalized paradigm, principally under the guidance of bioprinting, is poised to exert a significant influence in the foreseeable future. This systematic review undertakes the task of aggregating and analyzing insights related to the application of bioprinting in the context of regenerative dentistry. Adhering to PRISMA guidelines, an exhaustive literature survey spanning the years 2019 to 2023 was performed across prominent databases including PubMed, Scopus, Google Scholar, and ScienceDirect. The landscape of regenerative dentistry has ushered in novel prospects for dentoalveolar treatments and personalized interventions. This review expounds on contemporary accomplishments and avenues for the regeneration of pulp-dentin, bone, periodontal tissues, and gingival tissues. The progressive strides achieved in the realm of bioprinting hold the potential to not only enhance the quality of life but also to catalyze transformative shifts within the domains of medical and dental practices.

Fused Deposition Modeling Printed PLA/Nano β-TCP Composite Bone Tissue Engineering Scaffolds for Promoting Osteogenic Induction Function

Purpose

Large bone defects caused by congenital defects, infections, degenerative diseases, trauma, and tumors often require personalized shapes and rapid reconstruction of the bone tissue. Three-dimensional (3D)-printed bone tissue engineering scaffolds exhibit promising application potential. Fused deposition modeling (FDM) technology can flexibly select and prepare printed biomaterials and design and fabricate bionic microstructures to promote personalized large bone defect repair. FDM-3D printing technology was used to prepare polylactic acid (PLA)/nano β-tricalcium phosphate (TCP) composite bone tissue engineering scaffolds in this study. The ability of the bone-tissue-engineered scaffold to repair bone defects was evaluated in vivo and in vitro.

Methods

PLA/nano-TCP composite bone tissue engineering scaffolds were prepared using FDM-3D printing technology. The characterization data of the scaffolds were obtained using relevant detection methods. The physical and chemical properties, biocompatibility, and in vitro osteogenic capacity of the scaffolds were investigated, and their bone repair capacity was evaluated using an in vivo animal model of rabbit femur bone defects.

Results

The FDM-printed PLA/nano β-TCP composite scaffolds exhibited good personalized porosity and shape, and their osteogenic ability, biocompatibility, and bone repair ability in vivo were superior to those of pure PLA. The merits of biodegradable PLA and bioactive nano β-TCP ceramics were combined to improve the overall biological performance of the composites.

Conclusion

The FDM-printed PLA/nano-β-TCP composite scaffold with a ratio of 7:3 exhibited good personalized porosity and shape, as well as good osteogenic ability, biocompatibility, and bone repair ability. This study provides a promising strategy for treating large bone defects.

Regulation of Osteoimmune Microenvironment and Osteogenesis by 3D-Printed PLAG/black Phosphorus Scaffolds for Bone Regeneration

The treatment of bone defects remains a significant challenge to be solved clinically. Immunomodulatory properties of orthopedic biomaterials have significance in regulating osteoimmune microenvironment for osteogenesis. A lactic acid-co-glycolic acid (PLGA) scaffold incorporates black phosphorus (BP) fabricated by 3D printing technology to investigate the effect of BP on osteoimmunomodulation and osteogenesis in site. The PLGA/BP scaffold exhibits suitable biocompatibility, biodegradability, and mechanical properties as an excellent microenvironment to support new bone formation. The studies' result also demonstrate that the PLGA/BP scaffolds are able to recruit and stimulate macrophages M2 polarization, inhibit inflammation, and promote human bone marrow mesenchymal stem cells (hBMSCs) proliferation and differentiation, which in turn promotes bone regeneration in the distal femoral defect region of steroid-associated osteonecrosis (SAON) rat model. Moreover, it is screened and demonstrated that PLGA/BP scaffolds can promote osteogenic differentiation by transcriptomic analysis, and PLGA/BP scaffolds promote osteogenic differentiation and mineralization by activating PI3K-AKT signaling pathway in hBMSC cells. In this study, it is shown that the innovative PLGA/BP scaffolds are extremely effective in stimulating bone regeneration by regulating macrophage M2 polarization and a new strategy for the development of biomaterials that can be used to repair bone defects is offered.

Microporous Hydroxyapatite-Based Ceramics Alter the Physiology of Endothelial Cells through Physical and Chemical Cues

Incorporation of silicate ions in calcium phosphate ceramics (CPC) and modification of their multiscale architecture are two strategies for improving the vascularization of scaffolds for bone regenerative medicine. The response of endothelial cells, actors for vascularization, to the chemical and physical cues of biomaterial surfaces is little documented, although essential. We aimed to characterize in vitro the response of an endothelial cell line, C166, cultivated on the surface CPCs varying either in terms of their chemistry (pure versus silicon-doped HA) or their microstructure (dense versus microporous). Adhesion, metabolic activity, and proliferation were significantly altered on microporous ceramics, but the secretion of the pro-angiogenic VEGF-A increased from 262 to 386 pg/mL on porous compared to dense silicon-doped HA ceramics after 168 h. A tubulogenesis assay was set up directly on the ceramics. Two configurations were designed for discriminating the influence of the chemistry from that of the surface physical properties. The formation of tubule-like structures was qualitatively more frequent on dense ceramics. Microporous ceramics induced calcium depletion in the culture medium (from 2 down to 0.5 mmol/L), which is deleterious for C166. Importantly, this effect might be associated with the in vitro static cell culture. No influence of silicon doping of HA on C166 behavior was detected.

Latest Research of Doped Hydroxyapatite for Bone Tissue Engineering

Bone tissue engineering has attracted great interest in the last few years, as the frequency of tissue-damaging or degenerative diseases has increased exponentially. To obtain an ideal treatment solution, researchers have focused on the development of optimum biomaterials to be applied for the enhancement of bioactivity and the regeneration process, which are necessary to support the proper healing process of osseous tissues. In this regard, hydroxyapatite (HA) has been the most widely used material in the biomedical field due to its great biocompatibility and similarity with the native apatite from the human bone. However, HA still presents some deficiencies related to its mechanical properties, which are essential for HA to be applied in load-bearing applications. Bioactivity is another vital property of HA and is necessary to further improve regeneration and antibacterial activity. These drawbacks can be solved by doping the material with trace elements, adapting the properties of the material, and, finally, sustaining bone regeneration without the occurrence of implant failure. Considering these aspects, in this review, we have presented some general information about HA properties, synthesis methods, applications, and the necessity for the addition of doping ions into its structure. Also, we have presented their influence on the properties of HA, as well as the latest applications of doped materials in the biomedical field.

Physicochemical Characterization of Thermally Processed Goose Bone Ash for Bone Regeneration

Goose bone is traditionally applied for many ailments including bone fractures. Goose bone that consists of calcium phosphate plays a major role in bone regeneration. In this study, the production of goose bone ash (GBA) was translated from a traditional process into one of a laboratory scale via thermal and mechanical methods. The GBA was thermally processed via calcination at 300 °C and 900 °C. The differences in physicochemical properties between studied GBA (SGBA) and commercial GBA (CGBA) were elucidated via Fourier transform infrared (FT-IR), X-ray fluorescence (XRF), X-ray diffraction (XRD) and electron diffraction X-Ray (EDX). The morphological properties of SGBA and CGBA were characterized using field emission scanning electron microscopy (FESEM) in which nano-sized particles were detected. The results showed that the SGBA of 300 °C had comparable physicochemical properties to those of CGBA. A high processing temperature was associated with decreasing organic compounds and increasing crystallinity. The finding from EDX suggests that sintering at 900 °C (SGBA 900) demonstrated the presence of hydroxyapatite in the mineralogical phase and had a Ca/P atomic ratio of 1.64 which is comparable to the ideal stoichiometric ratio of 1.67. Findings from this study could be used for the further exploration of GBA as a potential material for bone regeneration via the elucidation of their biological properties in the next experimental setting.

Calcium Phosphate-Based Nanomaterials: Preparation, Multifunction, and Application for Bone Tissue Engineering

Calcium phosphate is the main inorganic component of bone. Calcium phosphate-based biomaterials have demonstrated great potential in bone tissue engineering due to their superior biocompatibility, pH-responsive degradability, excellent osteoinductivity, and similar components to bone. Calcium phosphate nanomaterials have gained more and more attention for their enhanced bioactivity and better integration with host tissues. Additionally, they can also be easily functionalized with metal ions, bioactive molecules/proteins, as well as therapeutic drugs; thus, calcium phosphate-based biomaterials have been widely used in many other fields, such as drug delivery, cancer therapy, and as nanoprobes in bioimaging. Thus, the preparation methods of calcium phosphate nanomaterials were systematically reviewed, and the multifunction strategies of calcium phosphate-based biomaterials have also been comprehensively summarized. Finally, the applications and perspectives of functionalized calcium phosphate biomaterials in bone tissue engineering, including bone defect repair, bone regeneration, and drug delivery, were illustrated and discussed by presenting typical examples.

Bone Regeneration Using Mesenchymal Stromal Cells and Biocompatible Scaffolds: A Concise Review of the Current Clinical Trials

Bone regenerative medicine is a clinical approach combining live osteoblast progenitors, such as mesenchymal stromal cells (MSCs), with a biocompatible scaffold that can integrate into host bone tissue and restore its structural integrity. Over the last few years, many tissue engineering strategies have been developed and thoroughly investigated; however, limited approaches have been translated to clinical application. Consequently, the development and clinical validation of regenerative approaches remain a centerpiece of investigational efforts towards the clinical translation of advanced bioengineered scaffolds. The aim of this review was to identify the latest clinical trials related to the use of scaffolds with or without MSCs to regenerate bone defects. A revision of the literature was performed in PubMed, Embase, and Clinicaltrials.gov from 2018 up to 2023. Nine clinical trials were analyzed according to the inclusion criteria: six presented in the literature and three reported in Clinicaltrials.gov. Data were extracted covering background trial information. Six of the clinical trials added cells to scaffolds, while three used scaffolds alone. The majority of scaffolds were composed of calcium phosphate ceramic alone, such as β-tricalcium phosphate (TCP) (two clinical trials), biphasic calcium phosphate bioceramic granules (three clinical trials), and anorganic bovine bone (two clinical trials), while bone marrow was the primary source of the MSCs (five clinical trials). The MSC expansion was performed in GMP facilities, using human platelet lysate (PL) as a supplement without osteogenic factors. Only one trial reported minor adverse events. Overall, these findings highlight the importance and efficacy of cell-scaffold constructs in regenerative medicine under different conditions. Despite the encouraging clinical results obtained, further studies are needed to assess their clinical efficacy in treating bone diseases to optimize their application.

Micro-hydroxyapatite reinforced Ti-based composite with tailored characteristics to minimize stress-shielding impact in bio-implant applications

Biomaterials having higher strength and increased bioactivity are widely researched topics in the area of scaffold and implant fabrication. Metal-based biomaterials are favorably suitable for load-bearing implants due to their outstanding mechanical and structural properties. The issue with pure metallic material used for bio-implant is the mismatch between the mechanical properties of the human body parts and the implant. The mismatch in modulus and hardness values causes damage to muscles and other body parts due to the phenomena of 'stress-shielding'. As per the rule of mixture, combining a biocompatible ceramic with metals will not only lower the overall mechanical strength, but will also enhance the composite's bioactivity. In the present work, a Metal-Ceramic composite of Ti and μ-HAp is processed through high-energy mechanical alloying. The μ-HAp powders (in a weight fraction of 1%, 2%, and 3%) were alloyed with Pure Ti powder sintered using microwave hybrid heating (MHH). The homogeneously alloyed materials were inspected for chemical and elemental characteristics using XRD, SEM-EDX, and FTIR analyses. Nano-mechanical and micro-hardness properties were inspected for the fabricated Ti- μ-HAp composites and it shows a decreasing trend. Elastic modulus declined from 130.8 GPa to 50.11 GPa for 3 wt% μ-HAp compared to pure-Ti sample. The mechanical behaviour of developed composites confirms that it can minimize the stress-shielding impact due to comparatively lesser strength and hardness than pure metallic samples.

Histological and Histomorphometric Evaluation of Implanted Photodynamic Active Biomaterials for Periodontal Bone Regeneration in an Animal Study

Recently, our group developed two different polymeric biomaterials with photodynamic antimicrobial surface activity for periodontal bone regeneration. The aim of the present study was to analyze the biocompatibility and osseointegration of these materials in vivo. Two biomaterials based on urethane dimethacrylate (BioM1) and tri-armed oligoester-urethane methacrylate (BioM2) that additionally contained ß-tricalcium phosphate and the photosensitizer mTHPC (meso-tetra(hydroxyphenyl)chlorin) were implanted in non-critical size bone defects in the femur (n = 16) and tibia (n = 8) of eight female domestic sheep. Bone specimens were harvested and histomorphometrically analyzed after 12 months. BioM1 degraded to a lower extent which resulted in a mean remnant square size of 17.4 mm², while 12.2 mm² was estimated for BioM2 (p = 0.007). For BioM1, a total percentage of new formed bone by 30.3% was found which was significant higher compared to BioM2 (8.4%, p < 0.001). Furthermore, BioM1 was afflicted by significant lower soft tissue formation (3.3%) as compared to BioM2 (29.5%). Additionally, a bone-to-biomaterial ratio of 81.9% was detected for BioM1, while 8.5% was recorded for BioM2. Implantation of BioM2 caused accumulation of inflammatory cells and led to fibrous encapsulation. BioM1 (photosensitizer-armed urethane dimethacrylate) showed favorable regenerative characteristics and can be recommended for further studies.

Antibiotic-loaded hydroxyapatite scaffolds fabricated from Nile tilapia bones for orthopaedics

This work aimed to develop new antibiotic-coated/ antibiotic-loaded hydroxyapatite (HAp) scaffolds for orthopaedic trauma, specifically to treat the infection after fixation of skeletal fracture. The HAp scaffolds were fabricated from the Nile tilapia (Oreochromis niloticus) bones and fully characterized. The HAp scaffolds were coated with 12 formulations of poly (lactic-co-glycolic acid) (PLGA) or poly (lactic acid) (PLA), blended with vancomycin. The vancomycin release, surface morphology, antibacterial properties, and the cytocompatibility of the scaffolds were conducted. The HAp powder contains elements identical to those found in human bones. This HAp powder is suitable as a starting material to build scaffolds. After the scaffold fabrication, The ratio of HAp to β-TCP changed, and the phase transformation of β-TCP to α-TCP was observed. All antibiotic-coated/ antibiotic-loaded HAp scaffolds can release vancomycin into the phosphate-buffered saline (PBS) solution. PLGA-coated scaffolds obtained faster drug release profiles than PLA-coated scaffolds. The low polymer concentration in the coating solutions (20%w/v) gave a faster drug release profile than the high polymer concentration (40%w/v). All groups showed a trace of surface erosion after being submerged in PBS for 14 days. Most of the extracts can inhibit Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA). The extracts not only caused no cytotoxicity to Saos-2 bone cells but also can increase cell growth. This study demonstrates that it is possible to use these antibiotic-coated/ antibiotic-loaded scaffolds in the clinic as an antibiotic bead replacement.

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites

Nanocrystalline calcium phosphate (CP) bioceramic coatings and their combination with biopolymers are innovative types of resorbable coatings for load-bearing implants that can promote the integration of metallic implants into human bodies. The nanocrystalline, amorphous CP particles are an advantageous form of the various calcium phosphate phases since they have a faster dissolution rate than that of crystalline hydroxyapatite. Owing to the biomineral additions (Mg, Zn, Sr) in optimized concentrations, the base CP particles became more similar to the mineral phase in human bones (dCP). The effect of biomineral addition into the CaP phases was thoroughly studied. The results showed that the shape, morphology, and amorphous characteristic slightly changed in the case of biomineral addition in low concentrations. The optimized dCP particles were then incorporated into a chosen polycaprolactone (PCL) biopolymer matrix. Very thin, non-continuous, rough layers were formed on the surface of implant substrates via the spin coating method. The SEM elemental mapping proved the perfect incorporation and distribution of dCP particles into the polymer matrix. The bioresorption rate of thin films was followed by corrosion measurements over a long period of time. The corrosion results indicated a faster dissolution rate for the dCP-PCL composite compared to the dCP and CP powder layers.

Fabrication and In Vitro Characterization of Novel Hydroxyapatite Scaffolds 3D Printed Using Polyvinyl Alcohol as a Thermoplastic Binder

This paper presents a proof-of-concept study on the biocolonization of 3D-printed hydroxyapatite scaffolds with mesenchymal stem cells (MSCs). Three-dimensional (3D) printed biomimetic bone structure made of calcium deficient hydroxyapatite (CDHA) intended as a future bone graft was made from newly developed composite material for FDM printing. The biopolymer polyvinyl alcohol serves in this material as a thermoplastic binder for 3D molding of the printed object with a passive function and is completely removed during sintering. The study presents the material, the process of fused deposition modeling (FDM) of CDHA scaffolds, and its post-processing at three temperatures (1200, 1300, and 1400 °C), as well it evaluates the cytotoxicity and biocompatibility of scaffolds with MTT and LDH release assays after 14 days. The study also includes a morphological evaluation of cellular colonization with scanning electron microscopy (SEM) in two different filament orientations (rectilinear and gyroid). The results of the MTT assay showed that the tested material was not toxic, and cells were preserved in both orientations, with most cells present on the material fired at 1300 °C. Results of the LDH release assay showed a slight increase in LDH leakage from all samples. Visual evaluation of SEM confirmed the ideal post-processing temperature of the 3D-printed FDM framework for samples fired at 1300 °C and 1400 °C, with a porosity of 0.3 mm between filaments. In conclusion, the presented fabrication and colonization of CDHA scaffolds have great potential to be used in the tissue engineering of bones.