Osteoinductive biomaterials--properties and relevance in bone repair

Material Composition and Implantation Site Affect in vivo Device Degradation Rate

Successful tissue engineering requires biomedical devices that initially stabilize wounds, then degrade as tissue is regenerated. However, the material degradation rates reported in literature are often conflicting. Incorporation of in situ monitoring functionality into implanted devices would allow real time assessment of degradation and potential failure. This necessitates introduction of contrast agent as most biomedical devices are composed of polymeric materials with no inherent contrast in medical imaging modalities. In the present study, computed tomography (CT)-visible radiopaque composites were created by adding 5-20wt% tantalum oxide (TaOx) nanoparticles into polymers with distinct degradation profiles: polycaprolactone (PCL), poly(lactide-co-glycolide) (PLGA) 85:15 and PLGA 50:50, representing slow, medium and fast degrading materials respectively. Radiopaque phantoms, mimicking porous tissue engineering devices, were implanted into mice intramuscularly or intraperitoneally, and monitored via CT over 20 weeks. Changes in phantom volume, including collapse and swelling, were visualized over time. Phantom degradation profile was determined by polymer matrix, regardless of nanoparticle addition and foreign body response was dictated by the implant site. In addition, degradation kinetics were significantly affected in mid-degrading materials, transitioning from linear degradation intramuscularly to exponential degradation intraperitoneally, due to differences in inflammatory responses and fluid flow. Nanoparticle excretion from degraded phantoms lagged behind polymer, and future studies will modulate nanoparticle clearance. Utilizing in situ monitoring, this study seeks to unify literature and facilitate better tissue engineering devices, by highlighting the relative effect of composition and implant site on important materials properties.

Engineering of Bioresorbable Polymers for Tissue Engineering and Drug Delivery Applications

Herein, the recent advances in the development of resorbable polymeric-based biomaterials, their geometrical forms, resorption mechanisms, and their capabilities in various biomedical applications are critically reviewed. A comprehensive discussion of the engineering approaches for the fabrication of polymeric resorbable scaffolds for tissue engineering, drug delivery, surgical, cardiological, aesthetical, dental and cardiovascular applications, are also explained. Furthermore, to understand the internal structures of resorbable scaffolds, representative studies of their evaluation by medical imaging techniques, e.g., cardiac computer tomography, are succinctly highlighted. This approach provides crucial clinical insights which help to improve the materials' suitable and viable characteristics for them to meet the highly restrictive medical requirements. Finally, the aspects of the legal regulations and the associated challenges in translating research into desirable clinical and marketable materials of polymeric-based formulations, are presented.

Supra-Alveolar Bone Regeneration: Progress, Challenges, and Future Perspectives

Periodontitis is a highly prevalent disease that damages the supporting tissues of a tooth, including the alveolar bone. Alveolar bone loss owing to periodontitis is broadly categorized as supra-alveolar and intra-alveolar bone loss. In intra-alveolar bone loss, the defect has an angular or oblique orientation to the long axis of the tooth in an apical direction. In contrast, the defect is perpendicular to the long axis of the tooth in supra-alveolar bone loss. Unlike intra-alveolar bone defects, supra-alveolar bone defects lack supporting adjacent space, which makes supra-alveolar bone regeneration more challenging. In addition, the limited availability of resources in terms of vascularity and underlying tissues is another obstacle to supra-alveolar bone regeneration. Currently, supra-alveolar bone loss is the least predictable periodontal defect type in regenerative periodontal therapy. In addition, supra-alveolar bone loss is much more common than other alveolar bone loss. Despite its prevalence, research on supra-alveolar bone regeneration remains sparse, indicating an unmet need for significant research efforts in this area. This review summarize recent advances, obstacles, and future directions in the field of supra-alveolar bone regeneration. We discuss the biomaterials, bioactive molecules, and cells that have been tested for supra-alveolar bone regeneration, followed by pre-clinical and clinical approaches employed in this field. Additionally, we highlight obstacles and present future directions that will propel supra-alveolar bone research forward.

Composite bone graft of CaO-MgO-SiO2 glass-ceramics and CaSO4 ceramics for boosting bone formation rate

This study develops a composite bone graft of CaO-MgO-SiO2 glass-ceramic and CaSO4 [abbreviated as (CMS)3-x(CS)x] via the sponge replication technique with weight fractions of x = 0, 1, 1.5, 2, and 3. The (CMS)1.5(CS)1.5 composite displays a superior degradability and, a suitable compressive strength of ∼3 MPa, and excellent cell proliferation and differentiation. The in vivo rat femur test in the hybrid-pore (CMS)1.5(CS)1.5 composite granules achieves a higher rate of bone formation, which is ∼2.7 times better than that of the commercial HAP/β-TCP at 12 weeks. Improved expressions of osteocyte and mature osteocyte marker genes, namely (Spp1, Dmp1, and Fgf23), were observed in the (CMS)1.5(CS)1.5 group, indicating a faster differentiation into mature bone tissue. The ions release of (CMS)1.5(CS)1.5 through the ERK1/2 signaling pathway promotes osteogenic differentiation. The high bone generation rate can be attributed to faster active ions release and modified surface topography. This work highlights an excellent bone graft candidate for clinical applications in orthopedic surgery.

Research trends of bio-application of major components in lignocellulosic biomass (cellulose, hemicellulose and lignin) in orthopedics fields based on the bibliometric analysis: A review

Cellulose, hemicellulose, and lignin are the major bio-components in lignocellulosic biomass (BC-LB), which possess excellent biomechanical properties and biocompatibility to satisfy the demands of orthopedic applications. To understand the basis and trends in the development of major bio-components in BC-LB in orthopedics, the bibliometric technology was applied to get unique insights based on the published papers (741) in the Web of Science (WOS) database from January 1st, 2001, to February 14th, 2023. The analysis includes the annual distributions of publications, keywords co-linearity, research hotspots exploration, author collaboration networks, published journals, and clustering of co-cited literature. The results reveal a steady growth in publications focusing on the application of BC-LB in orthopedics, with China and the United States leading in research output. The "International Journal of Biological Macromolecules" was identified as the most cited journal for BC-LB research in orthopedics. The research hotspots encompassed bone tissue engineering, cartilage tissue engineering, and drug delivery systems, indicating the fundamental research and potential development in these areas. This study also highlights the challenges associated with the clinical application of BC-LB in orthopedics and provides valuable insights for future advancements in the field.

Alveolar Repair Using Cancellous Bone and Beta Tricalcium Phosphate Seeded With Adipose-Derived Stem Cell

INTRODUCTION

Adipose-derived stem cells (ADSCs) have been subject of several studies due to their abundance, ease of preparation, and application in bone regeneration. We aim to compare effectiveness of alveolar reconstruction utilizing human cancellous freeze-dried graft (HCG) and beta tricalcium phosphate (BTP), both seeded with human ADSC (hADSC) and autologous bone graft (ABG).

MATERIAL AND METHODS

A 5 × 5 mm alveolar defect in 36 male Wistar rats were treated using: ABG (C), HCG-hADSC (H1), and BTP-hADSC (H2). At 1 and 8 weeks after surgery, runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osterix (OSX), and bone morphogenetic protein 2 (BMP2; g/mL) were quantified using immunohistochemistry, while bone tissue volume (BV, mm3), bone tissue volume fraction (BF, percentage), and trabecular thickness of bone (TT, mm) were assessed using micro-computed tomography (CT).

RESULTS

One week after surgery, H2 was higher in RUNX2, OSX, ALP, and BMP2 than C (P < .05). Only RUNX2 and OSX were found to be higher in H1 than C, while ALP and BMP2 were higher in H2 than H1. Micro-CT revealed that H2 had a higher TT than C and C had a higher TT than H1 (P < .05). Eight weeks after surgery, both H2 and H1 was higher in RUNX2, OSX, ALP, and BMP2 than C (P < .05). RUNX2 and BMP2 were found to be higher in H1 than H2. Micro-CT revealed that H2 had higher BV and TT than C and H1 (P < .05).

CONCLUSIONS

Exogenous hADSC strengthened the effectiveness of HCG and BTP to accelerate osteogenesis, osteoconduction, and osteoinduction. The latter was the most successful in bone formation, followed by HCG and ABG.

Effect of Surface Chemistry on Hemolysis, Thrombogenicity, and Toxicity of Carbon Nanotube Doped Thermally Sprayed Hydroxyapatite Implants

Assessing blood compatibility is crucial before in vivo procedures and is considered more reliable than many in vitro tests. This study examines the physiochemical properties and blood compatibility of bioactive powders ((0.5-2 wt % carbon nanotube (CNT)/alumina)-20 wt %)) produced through a heterocoagulation colloidal technique followed by ball milling with hydroxyapatite (HAp). The 1 wt % CNT composite demonstrated a surface charge ∼5 times higher than HAp at pH 7.4, with a value of -11 mV compared to -2 mV. This increase in electrostatic charge is desirable for achieving hemocompatibility, as evidenced by a range of blood compatibility assessments, including hemolysis, blood clotting, platelet adhesion, platelet activation, and coagulation assays (prothrombin time (PT) and activated partial thrombin time (aPTT)). The 1 wt % CNT composite exhibited hemolysis ranging from 2 to 7%, indicating its hemocompatibility. In the blood clot investigation, the absorbance values for 1-2 wt % CNT samples were 0.927 ± 0.038 and 1.184 ± 0.128, respectively, indicating their nonthrombogenicity. Additionally, the percentage of platelet adhered on the 1 wt % CNT sample (∼5.67%) showed a ∼2.5-fold decrement compared to the clinically used negative control, polypropylene (∼13.73%). The PT and aPTT experiments showed no difference in the coagulation time for CNT samples even at higher concentrations, unlike HAC2 (80 mg). In conclusion, the 1 wt % CNT sample was nontoxic to human blood, making it more hemocompatible, nonhemolytic, and nonthrombogenic than other samples. This reliable study reduces the need for additional in vitro and in vivo studies before clinical trials, saving time and cost.

A review on the application of chitosan-based polymers in liver tissue engineering

Chitosan-based polymers have enormous structural tendencies to build bioactive materials with novel characteristics, functions, and various applications, mainly in liver tissue engineering (LTE). The specific physicochemical, biological, mechanical, and biodegradation properties give the effective ways to blend these biopolymers with synthetic and natural polymers to fabricate scaffolds matrixes, sponges, and complexes. A variety of natural and synthetic biomaterials, including chitosan (CS), alginate (Alg), collagen (CN), gelatin (GL), hyaluronic acid (HA), hydroxyapatite (HAp), polyethylene glycol (PEG), polycaprolactone (PCL), poly(lactic-co-glycolic) acid (PGLA), polylactic acid (PLA), and silk fibroin gained considerable attention due to their structure-properties relationship. The incorporation of CS within the polymer matrix results in increased mechanical strength and also imparts biological behavior to the designed PU formulations. The significant and growing interest in the LTE sector, this review aims to be a detailed exploration of CS-based polymers biomaterials for LTE. A brief explanation of the sources and extraction, properties, structure, and scope of CS is described in the introduction. After that, a full overview of the liver, its anatomy, issues, hepatocyte transplantation, LTE, and CS LTE applications are discussed.

Biphasic calcium phosphate recruits Tregs to promote bone regeneration

The use of bone substitute materials is crucial for the healing of large bone defects. Immune response induced by bone substitute materials is essential in bone regeneration. Prior research has mainly concentrated on innate immune cells, such as macrophages. Existing research suggests that T lymphocytes, as adaptive immune cells, play an indispensable role in bone regeneration. However, the mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. This study demonstrates that CD4+ T cells are indispensable for ectopic osteogenesis by biphasic calcium phosphate (BCP). Subsequently, the recruitment of CD4+ T cells is closely associated with the activation of calcium channels in macrophages by BCP to release chemokines Ccl3 and Ccl17. Finally, these recruited CD4+ T cells are predominantly Tregs, which play a significant role in ectopic osteogenesis by BCP. These findings not only shed light on the immune-regenerative process after bone substitute material implantation but also establish a theoretical basis for developing bone substitute materials for promoting bone tissue regeneration. STATEMENT OF SIGNIFICANCE: Bone substitute material implantation is essential in the healing of large bone defects. Existing research suggests that T lymphocytes are instrumental in bone regeneration. However, the specific mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. In this study, we demonstrate that activation of calcium channels in macrophages by biphasic calcium phosphate (BCP) causes them to release the chemokines Ccl3 and Ccl17 to recruit CD4+ T cells, predominantly Tregs, which play a crucial role in ectopic osteogenesis by BCP. Our findings provide a theoretical foundation for developing bone substitute material for bone tissue regeneration.

Composite Remineralization of Bone-Collagen Matrices by Low-Temperature Ceramics and Serum Albumin: A New Approach to the Creation of Highly Effective Osteoplastic Materials

This study examined the effectiveness of coating demineralized bone matrix (DBM) with amorphous calcium phosphate (DBM + CaP), as well as a composite of DBM, calcium phosphate, and serum albumin (DBM + CaP + BSA). The intact structure of DBM promotes the transformation of amorphous calcium phosphate (CaP) into dicalcium phosphate dihydrate (DCPD) with a characteristic plate shape and particle size of 5-35 µm. The inclusion of BSA in the coating resulted in a better and more uniform distribution of CaP on the surface of DBM trabeculae. MG63 cells showed that both the obtained forms of CaP and its complex with BSA did not exhibit cytotoxicity up to a concentration of 10 mg/mL in vitro. Ectopic (subcutaneous) implantation in rats revealed pronounced biocompatibility, as well as strong osteoconductive, osteoinductive, and osteogenic effects for both DBM + CaP and DBM + CaP + BSA, but more pronounced effects for DBM + CaP + BSA. In addition, for the DBM + CaP + BSA samples, there was a pronounced full physiological intrafibrillar biomineralization and proangiogenic effect with the formation of bone-morrow-like niches, accompanied by pronounced processes of intramedullary hematopoiesis, indicating a powerful osteogenic effect of this composite.

Recent Progress in Advanced Polyester Elastomers for Tissue Engineering and Bioelectronics

Polyester elastomers are highly flexible and elastic materials that have demonstrated considerable potential in various biomedical applications including cardiac, vascular, neural, and bone tissue engineering and bioelectronics. Polyesters are desirable candidates for future commercial implants due to their biocompatibility, biodegradability, tunable mechanical properties, and facile synthesis and fabrication methods. The incorporation of bioactive components further improves the therapeutic effects of polyester elastomers in biomedical applications. In this review, novel structural modification methods that contribute to outstanding mechanical behaviors of polyester elastomers are discussed. Recent advances in the application of polyester elastomers in tissue engineering and bioelectronics are outlined and analyzed. A prospective of the future research and development on polyester elastomers is also provided.

Multipotent Mesenchymal Cells Homing and Differentiation on Poly(ε-caprolactone) Blended with 20% Tricalcium Phosphate and Polylactic Acid Incorporating 10% Hydroxyapatite 3D-Printed Scaffolds via a Commercial Fused Deposition Modeling 3D Device

As highlighted by the 'Global Burden of Disease Study 2019' conducted by the World Health Organization, ensuring fair access to medical care through affordable and targeted treatments remains crucial for an ethical global healthcare system. Given the escalating demand for advanced and urgently needed solutions in regenerative bone procedures, the critical role of biopolymers emerges as a paramount necessity, offering a groundbreaking avenue to address pressing medical needs and revolutionize the landscape of bone regeneration therapies. Polymers emerge as excellent solutions due to their versatility, making them reliable materials for 3D printing. The development and widespread adoption of this technology would impact production costs and enhance access to related healthcare services. For instance, in dentistry, the use of commercial polymers blended with β-tricalcium phosphate (TCP) is driven by the need to print a standardized product with osteoconductive features. However, modernization is required to bridge the gap between biomaterial innovation and the ability to print them through commercial printing devices. Here we showed, for the first time, the metabolic behavior and the lineage commitment of bone marrow-derived multipotent mesenchymal cells (MSCs) on the 3D-printed substrates poly(e-caprolactone) combined with 20% tricalcium phosphate (PCL + 20% β-TCP) and L-polylactic acid (PLLA) combined with 10% hydroxyapatite (PLLA + 10% HA). Although there are limitations in printing additive-enriched polymers with a predictable and short half-life, the tested 3D-printed biomaterials were highly efficient in supporting osteoinductivity. Indeed, considering different temporal sequences, both 3D-printed biomaterials resulted as optimal scaffolds for MSCs' commitment toward mature bone cells. Of interest, PLLA + 10% HA substrates hold the confirmation as the finest material for osteoinduction of MSCs.

Hybrid Implants Based on Calcium-Magnesium Silicate Ceramic Diopside as a Carrier of Recombinant BMP-2 and Demineralized Bone Matrix as a Scaffold: Ectopic Osteogenesis in Intramuscular Implantation in Mice

High efficiency of hybrid implants based on calcium-magnesium silicate ceramic, diopside, as a carrier of recombinant BMP-2 and xenogenic demineralized bone matrix (DBM) as a scaffold for bone tissue regeneration was demonstrated previously using the model of critical size cranial defects in mice. In order to investigate the possibility of using these implants for growing autologous bone tissue using in vivo bioreactor principle in the patient's own body, effectiveness of ectopic osteogenesis induced by them in intramuscular implantation in mice was studied. At the dose of 7 μg of BMP-2 per implant, dense agglomeration of cells, probably skeletal muscle satellite precursor cells, was observed one week after implantation with areas of intense chondrogenesis, initial stage of indirect osteogenesis, around the implants. After 12 weeks, a dense bone capsule of trabecular structure was formed covered with periosteum and mature bone marrow located in the spaces between the trabeculae. The capsule volume was about 8-10 times the volume of the original implant. There were practically no signs of inflammation and foreign body reaction. Microcomputed tomography data showed significant increase of the relative bone volume, number of trabeculae, and bone tissue density in the group of mice with BMP-2-containing implant in comparison with the group without BMP-2. Considering that DBM can be obtained in practically unlimited quantities with required size and shape, and that BMP-2 is obtained by synthesis in E. coli cells and is relatively inexpensive, further development of the in vivo bioreactor model based on the hybrid implants constructed from BMP-2, diopside, and xenogenic DBM seems promising.

Antimicrobial and Biodegradable 3D Printed Scaffolds for Orthopedic Infections

In bone tissue engineering, the performance of scaffolds underpins the success of the healing of bone. Microbial infection is the most challenging issue for orthopedists. The application of scaffolds for healing bone defects is prone to microbial infection. To address this challenge, scaffolds with a desirable shape and significant mechanical, physical, and biological characteristics are crucial. 3D printing of antibacterial scaffolds with suitable mechanical strength and excellent biocompatibility is an appealing strategy to surmount issues of microbial infection. The spectacular progress in developing antimicrobial scaffolds, along with beneficial mechanical and biological properties, has sparked further research for possible clinical applications. Herein, the significance of antibacterial scaffolds designed by 3D, 4D, and 5D printing technologies for bone tissue engineering is critically investigated. Materials such as antibiotics, polymers, peptides, graphene, metals/ceramics/glass, and antibacterial coatings are used to impart the antimicrobial features for the 3D scaffolds. Polymeric or metallic biodegradable and antibacterial 3D-printed scaffolds in orthopedics disclose exceptional mechanical and degradation behavior, biocompatibility, osteogenesis, and long-term antibacterial efficiency. The commercialization aspect of antibacterial 3D-printed scaffolds and technical challenges are also discussed briefly. Finally, the discussion on the unmet demands and prevailing challenges for ideal scaffold materials for fighting against bone infections is included along with a highlight of emerging strategies in this field.

An overview of 3D printed metal implants in orthopedic applications: Present and future perspectives

With the ability to produce components with complex and precise structures, additive manufacturing or 3D printing techniques are now widely applied in both industry and consumer markets. The emergence of tissue engineering has facilitated the application of 3D printing in the field of biomedical implants. 3D printed implants with proper structural design can not only eliminate the stress shielding effect but also improve in vivo biocompatibility and functionality. By combining medical images derived from technologies such as X-ray scanning, CT, MRI, or ultrasonic scanning, 3D printing can be used to create patient-specific implants with almost the same anatomical structures as the injured tissues. Numerous clinical trials have already been conducted with customized implants. However, the limited availability of raw materials for printing and a lack of guidance from related regulations or laws may impede the development of 3D printing in medical implants. This review provides information on the current state of 3D printing techniques in orthopedic implant applications. The current challenges and future perspectives are also included.

Retrograde Drilling, Ossoscopy, and Autologous Bone Grafting: An Alternative Technique for Treatment of Osteochondral Lesion of the Talus Stage 2 and 3 in Adults

BACKGROUND

Symptomatic osteochondral lesions of the talus (OLTs) often require surgical intervention. There are various surgical methods. A generally valid, stage-dependent therapeutic algorithm does not exist. The aim of our study is to show long- term results of an alternative technique that combines retrograde drilling, debridement performed under arthroscopic visualization, and autologous bone grafting.

METHODS

The surgical technique was performed in 24 patients with medial or lateral OLTs, and the data were analyzed retrospectively. In our technique, the affected subchondral bone was overdrilled retrogradely and resected under arthroscopic visualization (ossoscopy) without violating the cartilage. The resulting defect was filled with autologous bone from the medial tibia metaphysis. Outcome parameters were the numeric rating scale (NRS), the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, and range of motion (ROM). The Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score was assessed and a possible correlation with the clinical outcome scores was calculated. Data concerning complication rates were also collected.

RESULTS

The mean surface size of the OLTs was 0.9 ± 0.3 cm2. The mean follow-up was 89 months. The AOFAS score improved significantly from 57.7 points preoperatively to 88.8 points at the final follow-up (P < .0001). The pain value measured by the NRS decreased significantly from 8 to a pain level of 2. ROM improved in 37.5% of the patients for dorsiflexion and 29.2% for plantarflexion. There were no significant correlations between the MOCART score and the AOFAS score or the pain value on NRS.

CONCLUSION

Retrograde drilling, ossoscopy, and autologous bone grafting for OLTs is a promising technique with good long-term results. The patients' satisfaction rate, especially in OLT stages 2 and 3, was excellent.

LEVEL OF EVIDENCE

Level IV, case series.

A Novel Hydroxyapatite/Vitamin B12 Nanoformula for Treatment of Bone Damage: Preparation, Characterization, and Anti-Arthritic, Anti-Inflammatory, and Antioxidant Activities in Chemically Induced Arthritic Rats

The usage of nanomaterials for rheumatoid arthritis (RA) treatment can improve bioavailability and enable selective targeting. The current study prepares and evaluates the in vivo biological effects of a novel hydroxyapatite/vitamin B₁₂ nanoformula in Complete Freund's adjuvant-induced arthritis in rats. The synthesized nanoformula was characterized using XRD, FTIR, BET analysis, HERTEM, SEM, particle size, and zeta potential. We synthesized pure HAP NPs with 71.01% loading weight percentages of Vit B12 and 49 mg/g loading capacity. Loading of vitamin B₁₂ on hydroxyapatite was modeled by Monte Carlo simulation. Anti-arthritic, anti-inflammatory, and antioxidant effects of the prepared nanoformula were assessed. Treated arthritic rats showed lower levels of RF and CRP, IL-1β, TNF-α, IL-17, and ADAMTS-5, but higher IL-4 and TIMP-3 levels. In addition, the prepared nanoformula increased GSH content and GST antioxidant activity while decreasing LPO levels. Furthermore, it reduced the expression of TGF-β mRNA. Histopathological examinations revealed an improvement in joint injuries through the reduction of inflammatory cell infiltration, cartilage deterioration, and bone damage caused by Complete Freund's adjuvant. These findings indicate that the anti-arthritic, antioxidant, and anti-inflammatory properties of the prepared nanoformula could be useful for the development of new anti-arthritic treatments.

Biomimetic Remineralized Three-Dimensional Collagen Bone Matrices with an Enhanced Osteostimulating Effect

Bone grafts with a high potential for osseointegration, capable of providing a complete and effective regeneration of bone tissue, remain an urgent and unresolved issue. The presented work proposes an approach to develop composite biomimetic bone material for reconstructive surgery by deposition (remineralization) on the surface of high-purity, demineralized bone collagen matrix calcium phosphate layers. Histological and elemental analysis have shown reproduction of the bone tissue matrix architectonics, and a high-purity degree of the obtained collagen scaffolds; the cell culture and confocal microscopy have demonstrated a high biocompatibility of the materials obtained. Adsorption spectroscopy, scanning electron microscopy, microcomputed tomography (microCT) and infrared spectroscopy, and X-ray diffraction have proven the efficiency of the deposition of calcium phosphates on the surface of bone collagen scaffolds. Cell culture and confocal microscopy methods have shown high biocompatibility of both demineralized and remineralized bone matrices. In the model of heterotopic implantation in rats, at the term of seven weeks, an intensive intratrabecular infiltration of calcium phosphate precipitates, and a pronounced synthetic activity of osteoblast remodeling and rebuilding implanted materials, were revealed in remineralized bone collagen matrices in contrast to demineralized ones. Thus, remineralization of highly purified demineralized bone matrices significantly enhanced their osteostimulating ability. The data obtained are of interest for the creation of new highly effective osteoplastic materials for bone tissue regeneration and augmentation.

Chitosan scaffolds with mesoporous hydroxyapatite and mesoporous bioactive glass

Bone regeneration is one of the most well-known fields in tissue regeneration. The major focus concerns polymeric/ceramic composite scaffolds. In this work, several composite scaffolds based on chitosan (CH), with low and high molecular weights, and different concentrations of ceramics like mesoporous bioactive glass (MBG), mesoporous hydroxyapatite (MHAp) and both MBG and MHAp (MC) were produced by lyophilization. The purpose is to identify the best combination regarding optimal morphology and properties. The tests of the scaffolds present a highly porous structure with interconnected pores. The compression modulus increases with ceramic concentration in the scaffolds. Furthermore, the 75%MBG (835 ± 160 kPa) and 50%MC (1070 ± 205 kPa) samples are the ones that mostly enhance increases in mechanical properties. The swelling capacity increases with MBG and MC, respectively, to 700% and 900% and decreases to 400% when MHAp concentration increases. All scaffolds are non-cytotoxic at 12.5 mg/mL. The CHL scaffolds improve cell adhesion and proliferation compared to CHH, and the MC scaffold samples, show better results than those produced with just MBG or MHAp. The composite scaffolds of chitosan with MBG and MHAp, have revealed to be the best combination due to their enhanced performance in bone tissue engineering.

Osteoregenerative efficacy of a novel synthetic, resorbable Ca/P/S-based bone graft substitute in intra- and peri-articular fractures: a brief medical image-based report

Background

When a fracture goes into or around a joint, it usually damages the cartilage at the ends of bones and other joint tissue. As a result, the affected joints are prone to traumatic arthritis, leading to stiffness. Repairing bone damage, maintaining joint integrity, and avoiding subchondral and metaphyseal defects caused by comminuted fractures is often a great challenge for orthopedic surgeons. Tissue engineering of synthetic bone substitutes has proven beneficial to the attachment and proliferation of bone cells, promoting the formation of mature tissues with sufficient mechanical strength and has become a promising alternative to autograft methods. The purpose of this study is to retrospectively evaluate the clinical outcome and efficacy of a novel synthetic, highly biocompatible, and fully resorbable Ca/P/S-based bone substitute based on medical image findings.

Materials and methods

A synthetic, inorganic and highly porous Ca/P/S-based bone-substituting material (Ezechbone® Granule, CBS-400) has been developed by National Cheng-Kung University. We collected fourteen cases of complex intra- and peri-articular fractures with Ezechbone® Granule bone grafting between 2019/11 and 2021/11. We studied the evidence of bone healing by reviewing, interpreting and analyzing the medical image recordings.

Results

In the present study, CBS-400 was observed to quickly integrate into surrounding bone within three weeks after grafting during the initial callus formation of the early stage of repair. All of these cases healed entirely within three months. In addition, the patient may return to daily life function after 3.5 months of follow-up and rehabilitation treatment.

Conclusions

Ezechbone® Granule CBS-400 was proved capable of promoting bone healing and early rehabilitation to prevent soft tissue adhesions and joint contractures. Moreover, it has a high potential for avoiding ectopic bone formation or abnormal synostosis.

Trial registration

The Institutional Review Board at National Cheng Kung University Hospital (NCKUH) approved the study protocol (A-ER-109-031, 3-13-2020).

3D Biocomposites Comprising Marine Collagen and Silica-Based Materials Inspired on the Composition of Marine Sponge Skeletons Envisaging Bone Tissue Regeneration

Ocean resources are a priceless repository of unique species and bioactive compounds with denouement properties that can be used in the fabrication of advanced biomaterials as new templates for supporting the cell culture envisaging tissue engineering approaches. The collagen of marine origin can be sustainably isolated from the underrated fish processing industry by-products, while silica and related materials can be found in the spicules of marine sponges and diatoms frustules. Aiming to address the potential of biomaterials composed from marine collagen and silica-based materials in the context of bone regeneration, four different 3D porous structure formulations (COL, COL:BG, COL:D.E, and COL:BS) were fabricated by freeze-drying. The skins of Atlantic cod (Gadus morhua) were used as raw materials for the collagen (COL) isolation, which was successfully characterized by SDS-PAGE, FTIR, CD, and amino acid analyses, and identified as a type I collagen, produced with a 1.5% yield and a preserved characteristic triple helix conformation. Bioactive glass 45S5 bioglass® (BG), diatomaceous earth (D.E.) powder, and biosilica (BS) isolated from the Axinella infundibuliformis sponge were chosen as silica-based materials, which were obtained as microparticles and characterized by distinct morphological features. The biomaterials revealed microporous structures, showing a porosity higher than 85%, a mean pore size range of 138-315 μm depending on their composition, with 70% interconnectivity which can be favorable for cell migration and ensure the needed nutrient supply. In vitro, biological assays were conducted by culturing L929 fibroblast-like cells, which confirmed not only the non-toxic nature of the developed biomaterials but also their capability to support cell adhesion and proliferation, particularly the COL:BS biomaterials, as observed by calcein-AM staining upon seven days of culture. Moreover, phalloidin and DAPI staining revealed well-spread cells, populating the entire construct. This study established marine collagen/silica biocomposites as potential scaffolds for tissue engineering, setting the basis for future studies, particularly envisaging the regeneration of non-load-bearing bone tissues.

Rubbing-Assisted Approach for Fabricating Oriented Nanobiomaterials

The highly-oriented structures in biological tissues play an important role in determining the functions of the tissues. In order to artificially fabricate oriented nanostructures similar to biological tissues, it is necessary to understand the oriented mechanism and invent the techniques for controlling the oriented structure of nanobiomaterials. In this review, the oriented structures in biological tissues were reviewed and the techniques for producing highly-oriented nanobiomaterials by imitating the oriented organic/inorganic nanocomposite mechanism of the biological tissues were summarized. In particular, we introduce a fabrication technology for the highly-oriented structure of nanobiomaterials on the surface of a rubbed polyimide film that has physicochemical anisotropy in order to further form the highly-oriented organic/inorganic nanocomposite structures based on interface interaction. This is an effective technology to fabricate one-directional nanobiomaterials by a biomimetic process, indicating the potential for wide application in the biomedical field.

Microfluidic 3D Platform to Evaluate Endothelial Progenitor Cell Recruitment by Bioactive Materials

Most of the conventional in vitro models to test biomaterial-driven vascularization are too simplistic to recapitulate the complex interactions taking place in the actual cell microenvironment, which results in a poor prediction of the in vivo performance of the material. However, during the last decade, cell culture models based on microfluidic technology have allowed attaining unprecedented levels of tissue biomimicry. In this work, we propose a microfluidic-based 3D model to evaluate the effect of bioactive biomaterials capable of releasing signalling cues (such as ions or proteins) in the recruitment of endogenous endothelial progenitor cells, a key step in the vascularization process. The usability of the platform is demonstrated using experimentally-validated finite element models and migration and proliferation studies with rat endothelial progenitor cells (rEPCs) and bone marrow-derived rat mesenchymal stromal cells (BM-rMSCs). As a proof of concept of biomaterial evaluation, the response of rEPCs to an electrospun composite made of polylactic acid with calcium phosphates nanoparticles (PLA+CaP) was compared in a co-culture microenvironment with BM-rMSC to a regular PLA control. Our results show a significantly higher rEPCs migration and the upregulation of several pro-inflammatory and proangiogenic proteins in the case of the PLA+CaP. The effects of osteopontin (OPN) on the rEPCs migratory response were also studied using this platform, suggesting its important role in mediating their recruitment to a calcium-rich microenvironment. This new tool could be applied to screen the capacity of a variety of bioactive scaffolds to induce vascularization and accelerate the preclinical testing of biomaterials. STATEMENT OF SIGNIFICANCE: : For many years researchers have used neovascularization models to evaluate bioactive biomaterials both in vitro, with low predictive results due to their poor biomimicry and minimal control over cell cues such as spatiotemporal biomolecule signaling, and in vivo models, presenting drawbacks such as being highly costly, time-consuming, poor human extrapolation, and ethically controversial. We describe a compact microphysiological platform designed for the evaluation of proangiogenesis in biomaterials through the quantification of the level of sprouting in a mimicked endothelium able to react to gradients of biomaterial-released signals in a fibrin-based extracellular matrix. This model is a useful tool to perform preclinical trustworthy studies in tissue regeneration and to better understand the different elements involved in the complex process of vascularization.

Assessment of Cell-Material Interactions in Three Dimensions through Dispersed Coaggregation of Microsized Biomaterials into Tissue Spheroids

In biomaterials R&D, conventional monolayer cell culture on flat/planar material samples, such as films, is still commonly employed at early stages of the assessment of interactions of cells with candidate materials considered for a biomedical application. In this feasibility study, an approach for the assessment of 3D cell-material interactions through dispersed coaggregation of microparticles from biomaterials into tissue spheroids is presented. Biomaterial microparticles can be created comparatively quickly and easily, allow the miniaturization of the assessment platform, and enable an unhindered remodeling of the dynamic cell-biomaterial system at any time. The aggregation of the microsized biomaterials and the cells is supported by low-attachment round-bottom microwells from thin polymer films arranged in densely packed arrays. The study is conducted by the example of MG63 osteoblast-like and human mesenchymal stem/stromal cells, and a small library of model microbiomaterials related to bone repair and regeneration. For the proof of concept, example interactions including cell adhesion to the material, the hybrid spheroids' morphology, size, and shape, material-associated cell death, cell metabolic activity, cell proliferation, and (osteogenic) differentiation are investigated. The cells in the spheroids are shown to respond to differences in the microbiomaterials' properties, their amounts, and the duration of interaction with them.

Clinical and Radiologic Outcome of First Metatarsophalangeal Joint Arthrodesis Using a Human Allogeneic Cortical Bone Screw

Background:

Different fixation techniques are established for first metatarsophalangeal joint (MTPJ) arthrodesis, including compression screws, plates, Kirschner wires, metal- and bioabsorbable screws as well as staples. The purpose of this study was to investigate and present first clinical and radiologic results using a novel human, allogeneic cortical bone screw for arthrodesis of the first MTPJ.

Methods:

Arthrodesis of the first MTPJ was performed in 31 patients with hallux rigidus. Percentage union and time to union were the first outcomes; visual analog scale for pain, hallux valgus angle (HVA), intermetatarsal angle, and American Orthopaedic Foot & Ankle Society (AOFAS) hallux score were secondary outcomes.

Results:

Median time to union was 89 days, and union was observed in all patients. There were 4 complications (2 osteolysis margin, 1 cystic brightening, and 1 severe swelling at the first follow-up) all of that resolved at last follow-up. Pain significantly decreased from visual analog scale 8.0 to 0.2 points ( P < .0001). The HVA decreased from 30.4 to 10.2 degrees in the patient group with deformities. The total AOFAS score increased significantly from 48 to 87 ( P < .0001).

Conclusion:

Primary and revision arthrodesis of hallux rigidus with the human, allogeneic cortical bone screw reveals satisfying results similar to clinical and radiologic outcomes of other surgical techniques. Within 1 year, the human, allogeneic cortical bone screw is fully remodeled to host bone.

Level of Evidence:

Level IV, retrospective case series without control group.

Preparation and characterization of two novel osteoinductive fishbone-derived biphasic calcium phosphate bone graft substitutes

Many studies have reported on the conversion of natural resources into xenografts with hydroxyapatite (HA) as major component, but the extraction of biphasic calcium phosphate (HA/β-TCP) from animal bones and transformation into bone graft substitutes are rarely reported. In this research, two kinds of fish bones were made into granular porous biphasic calcium phosphate bone graft substitutes with particle sizes between 500 to 1000 μm through a series of preparation procedures (Salmo salar calcined at 900°C named Sa900 and Anoplopoma fimbria calcined at 800°C named An800). The chemical composition was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The morphology and porous structure of the scaffolds were comparatively analyzed by scanning electron microscopy (SEM) and mercury porosimeter. The specific surface area of materials was measured by the nitrogen adsorption technique based on BET theory. Cytotoxicity and ectopic osteogenesis were also carried out to investigate the biocompatibility and osteoinductive potential of these materials. The results showed that both fishbone-derived scaffolds were composed of HA and β-TCP with different proportions, and numerous interconnected pores with different sizes were observed at the surface of materials. An800 had higher total porosity reaching 74.8% with higher interconnectivity and micropores mostly distributed at 0.27 μm and 0.12 μm, while Sa900 had a higher specific surface area and higher intraparticle porosity with nanopores mostly distributed at 0.07 μm. CCK-8 assays and Live/dead staining demonstrated excellent biocompatibility. Material-induced osteoid formation were observed on the interface of both internal pores and periphery of materials after implantation in muscle pouch of Wistar rats for 8 weeks which indicated some extent of osteoinductive potential of materials. The possible mechanism of material-induced osteogenesis and the effects of chemical composition, surface topography, and spatial structure on osteogenesis were also discussed in this paper.

Clinical Reference Strategy for the Selection of Treatment Materials for Maxillofacial Bone Transplantation: A Systematic Review and Network Meta-Analysis

Bone graft materials have mixed effects of bone repair in the field of oral maxillofacial surgery. The qualitative analyses performed by previous studies imply that autogenous odontogenic materials and autogenous bone have similar effects on bone repair in clinical jaw bone transplantation. This retrospective systematic assessment and network meta-analysis aimed to analyze the best effect of clinical application of autogenous odontogenic materials and autogenous, allogeneic, and xenogeneic bone grafts in bone defect repair. A systematic review was performed by searching the PubMed, Cochrane Library, and other journal databases using selected keywords and Medical Subject Headings search terms. 10 Papers (n = 466) that met the inclusion criteria were selected. The assessment of heterogeneity did not reveal any overall statistical difference or heterogeneity (P = 0.051 > 0.05), whereas the comparison between autogenous and allogeneic bone grafts revealed local heterogeneity (P = 0.071 < 0.1). Risk of bias revealed nine unclear studies and one high-risk study. The overall consistency was good (P = 0.065 > 0.05), and the local inconsistency test did not reveal any inconsistency. The publication bias was good. The confidence regarding the ranking of bone graft materials after GRADE classification was moderate. The effects on bone repair in the descending order were as follows: autogenous odontogenic materials, xenogeneic bone, autogenous bone, and allogeneic bone. This result indicates that the autogenous odontogenic materials displayed stronger effects on bone repair compared to other bone graft materials. Autogenous odontogenic materials have broad development prospects in oral maxillofacial surgery.

3D-printed bioactive ceramic scaffolds with biomimetic micro/nano-HAp surfaces mediated cell fate and promoted bone augmentation of the bone–implant interface in vivo

Calcium phosphate bio-ceramics are osteo-conductive, but it remains a challenge to promote the induction of bone augmentation and capillary formation. The surface micro/nano-topography of materials can be recognized by cells and then the cell fate are mediated. Traditional regulation methods of carving surface structures on bio-ceramics employ mineral reagents and organic additives, which might introduce impurity phases and affect the biological results. In a previous study, a facile and novel method was utilized with ultrapure water as the unique reagent for hydrothermal treatment, and a uniform hydroxyapatite (HAp) surface layer was constructed on composite ceramics (β-TCP/CaSiO₃) in situ. Further combined with 3D printing technology, biomimetic hierarchical structure scaffolds were fabricated with interconnected porous composite ceramic scaffolds as the architecture and micro/nano-rod hybrid HAp as the surface layer. The obtained HAp surface layer favoured cell adhesion, alleviated the cytotoxicity of precursor scaffolds, and upregulated the cellular differentiation of mBMSCs and gene expression of HUVECs in vitro. In vivo studies showed that capillary formation, bone augmentation and new bone matrix formation were upregulated after the HAp surface layer was obtained, and the results confirmed that the fabricated biomimetic hierarchical structure scaffold could be an effective candidate for bone regeneration.

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Simple and practical process to construct surface structure layer in situ with little impurities.

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Combined with the 3D printing technology to fabricate architecture of the pre-treated matrix.

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Study the angiogenesis and osteogenesis (for mesenchymal stem cells) separately.

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Improving tissue growth in vivo: capillary formation, bone-augmentation and new bone matrix formation.

The Application of an Allogenic Bone Screw for Stabilization of a Modified Chevron Osteotomy: A Prospective Analysis

Background: Distal first metatarsal osteotomies are commonly performed operative procedures for hallux valgus deformity, and usually involve fixation with a metal screw. However, various bioabsorbable osteosynthesis materials have been in use for a number of years. One recent innovation is the Shark Screw®, a human cortical bone allograft. This study aimed to evaluate the efficacy and safety of this allogeneic screw in the stabilization of Reversed L-Shaped osteotomy, a modified Chevron osteotomy. Methods: In a prospective study, 15 patients underwent a Reversed L-Shaped osteotomy stabilized with the allogenic bone screw Radiological data on osteointegration of the screw and correction of the intermetatarsal angle were recorded. Furthermore, each follow-up examination included the collection of clinical data, the American Orthopedic Foot and Ankle Society (AOFAS) score, evaluation of pain level, and patient’s overall satisfaction. Results: Full osseous fusion of the osteotomy was seen in all patients. The bone screws were radiographically integrated after approximately 6.5 (±2.6) months. Neither nonunion nor failure occurred in any of our cases. Furthermore, we did not find any potential graft reaction. The AOFAS score improved significantly from 51.6 (±15.2) points to 90.9 (±10.3) (p < 0.001). The preoperative hallux valgus angle and intermetatarsal angle decreased significantly from 24.8 (±4.9) degrees to 7.2 (±4.4) degrees (p < 0.001) and 12.6 (±3.2) degrees to 4.8 (±1.3) degrees (p < 0.001), respectively. Conclusions: With this study, we demonstrated the efficiency of the allogenic bone screw (Shark Screw®) in regard to clinical and radiological short-term outcomes.

Osteogenic Induction with Silicon Hydroxyapatite Using Modified Autologous Adipose Tissue-Derived Stromal Vascular Fraction: In Vitro and Qualitative Histomorphometric Analysis

Large bone defects requiring invasive surgical procedures have long been a problem for orthopedic surgeons. Despite the use of autologous bone grafting, satisfactory results are often not achieved due to associated limitations. Biomaterials are viable alternatives and have lately been used in association with Stromal Vascular Fraction (SVF), stem cells, and signaling factors for bone tissue engineering (BTE). The objective of the current study was to assess the biocompatibility of Silicon Hydroxyapatite (Si-HA) and to improve osteogenic potential by using autologous adipose-derived SVF with Si-HA in a rabbit bone defect model. Si-HA granules synthesized using a wet precipitation method were used. They were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). A hemolysis assay was used to assess the hemolytic effects of Si-HA, while cell viability was assessed through Alamar Blue assay using MC3T3 mouse osteoblasts. The osteogenic potential of Si-HA both alone and with enzymatically/non-enzymatically-derived SVF (modified) was performed by implantation in a rabbit tibia model followed by histomorphometric analysis and SEM of dissected bone after six weeks. The results showed that Si-HA granules were microporous and phase pure and that the addition of Silicon did not influence Si-HA phase composition. Si-HA granules were found to be non-hemolytic on the hemolysis assay and non-toxic to MC3T3 mouse osteoblasts on the Alamar Blue assay. Six weeks following implantation Si-HA showed high biocompatibility, with increased bone formation in all groups compared to control. Histologically more mature bone was formed in the Si-HA implanted along with non-enzymatically-derived modified SVF. Bone formation was observed on and around Si-HA, reflecting osseointegration. In conclusion, Si-HA is osteoconductive and promotes osteogenesis, and its use with SVF enhances osteogenesis.

Osteoconductive Effect of a Nanocomposite Membrane Treated with UV Radiation

Modulation of the bio-regenerative characteristics of materials is an indispensable requirement in tissue engineering. Particularly, in bone tissue engineering, the promotion of the osteoconductive phenomenon determines the elemental property of a material be used therapeutically. In addition to the chemical qualities of the constituent materials, the three-dimensional surface structure plays a fundamental role that various methods are expected to modulate in a number of ways, one most promising of which is the use of different types of radiation. In the present manuscript, we demonstrate in a calvarial defect model, that treatment with ultraviolet irradiation allows modification of the osteoconductive characteristics in a biomaterial formed by gelatin and chitosan, together with the inclusion of hydroxyapatite and titanium oxide nanoparticles.

Eggshell Microparticle Reinforced Scaffolds for Regeneration of Critical Sized Cranial Defects

Scaffold-based approaches for bone regeneration have been studied using a wide range of biomaterials as reinforcing agents to improve the mechanical strength and bioactivity of the 3D constructs. Eggshells are sustainable and inexpensive materials with unique biological and chemical properties to support bone differentiation. The incorporation of eggshell particles within hydrogels yields highly osteoinductive and osteoconductive scaffolds. This study reveals the effects of microparticles of whole eggshells, eggshells without a membrane, and a pristine eggshell membrane on osteogenic differentiation in protein-derived hydrogels. The in vitro studies showed that gels reinforced with eggshells with and without a membrane demonstrated comparable cellular proliferation, osteogenic gene expression, and osteogenic differentiation. Subsequently, in vivo studies were performed to implant eggshell microparticle-reinforced composite hydrogel scaffolds into critical-sized cranial defects in Sprague Dawley (SD) rats for up to 12 weeks to study bone regeneration. The in vivo results showed that the eggshell microparticle-based scaffolds supported an average bone volume of 60 mm³ and a bone density of 2000 HU 12 weeks post implantation. Furthermore, histological analyses of the explanted scaffolds showed that the eggshell microparticle-reinforced scaffolds permitted tissue infiltration and induced bone tissue formation over 12 weeks. The histology staining also indicated that these scaffolds induced significantly higher bone regeneration at 6 and 12 weeks as compared to the blank (no scaffold) and pristine gel scaffolds. The eggshell microparticle-reinforced scaffolds also supported significantly higher bone formation, remodeling, and vascularization over 6 and 12 weeks as confirmed by immunohistochemistry analysis. Collectively, our results indicated that eggshell microparticle-reinforced scaffolds facilitated significant bone regeneration in critical-sized cranial defects.

Octacalcium Phosphate for Bone Tissue Engineering: Synthesis, Modification, and In Vitro Biocompatibility Assessment

Octacalcium phosphate (OCP, Ca₈H₂(PO₄)₆·5H₂O) is known to be a possible precursor of biological hydroxyapatite formation of organic bone tissue. OCP has higher biocompatibility and osseointegration rate compared to other calcium phosphates. In this work, the synthesis of low-temperature calcium phosphate compounds and substituted forms of those at physiological temperatures is shown. Strontium is used to improve bioactive properties of the material. Strontium was inserted into the OCP structure by ionic substitution in solutions. The processes of phase formation of low-temperature OCP with theoretical substitution of strontium for calcium up to 50 at.% in conditions close to physiological, i.e., temperature 35–37 °C and normal pressure, were described. The effect of strontium substitution range on changes in the crystal lattice of materials, the microstructural features, surface morphology and biological properties in vitro has been established. The results of the study indicate the effectiveness of using strontium in OCP for improving biocompatibility of OCP based composite materials intended for bone repair.

High-strength, porous additively manufactured implants with optimized mechanical osseointegration

Optimization of porous titanium alloy scaffolds designed for orthopedic implants requires balancing mechanical properties and osseointegrative performance. The tradeoff between scaffold porosity and the stiffness/strength must be optimized towards the goal to improve long term load sharing while simultaneously promoting osseointegration. Osseointegration into porous titanium implants covering a wide range of porosity (0%-90%) and manufactured by laser powder bed fusion (LPBF) was evaluated with an established ovine cortical and cancellous defect model. Direct apposition and remodeling of woven bone was observed at the implant surface, as well as bone formation within the interstices of the pores. A linear relationship was observed between the porosity and benchtop mechanical properties of the scaffolds, while a non-linear relationship was observed between porosity and the ex vivo cortical bone-implant interfacial shear strength. Our study supports the hypothesis of porosity dependent performance tradeoffs, and establishes generalized relationships between porosity and performance for design of topological optimized implants for osseointegration. These results are widely applicable for orthopedic implant design for arthroplasty components, arthrodesis devices such as spinal interbody fusion implants, and patient matched implants for treatment of large bone defects.

Tunable chitosan-calcium phosphate composites as cell-instructive dental pulp capping agents

Dental cavities are the most prevalent, preventable disease worldwide providing a need for robust treatment options to restore both the form and function of decaying teeth. Here is a presentation of a possible regenerative pulp capping agent that can serve to restore tooth function while regenerating healthy dentin tissue over a long period of time. To achieve this goal a material needs to crosslink quickly, be structurally rigid, and support the proliferation and differentiation of stem cells contained within the dental pulp. In this study, calcium phosphate nanoparticles were embedded in polymer hydrogels of carboxymethyl-chitosan and a diglycidyl ether. The particle size, surface, and mechanical properties of these materials were characterized. These composites have moduli up to 3 MPa, support the culture of dental pulp stem cells more than 3 weeks and exhibit osteogenic potential even without osteogenic media. These composites demonstrate a promising potential as the next generation of pulp capping materials.

In situ printing of scaffolds for reconstruction of bone defects

Bone defects are commonly caused by traumatic injuries and tumor removal and critically sized defects overwhelm the regenerative capacity of the native tissue. Reparative strategies such as auto, xeno, and allografts have proven to be insufficient to reconstruct and regenerate these defects. For the first time, we introduce the use of handheld melt spun three dimensional printers that can deposit materials directly within the defect site to properly fill the cavity and form free-standing scaffolds. Engineered composite filaments were generated from poly(caprolactone) (PCL) doped with zinc oxide nanoparticles and hydroxyapatite microparticles. The use of PCL-based materials allowed low-temperature printing to avoid overheating of the surrounding tissues. The in situ printed scaffolds showed moderate adhesion to wet bone tissue, which can prevent scaffold dislocation. The printed scaffolds showed to be osteoconductive and supported the osteodifferentiation of mesenchymal stem cells. Biocompatibility of the scaffolds upon in vivo printing subcutaneously in mice showed promising results. STATEMENT OF SIGNIFICANCE.

Incorporation of an Allogenic Cortical Bone Graft Following Arthrodesis of the First Metatarsophalangeal Joint in a Patient with Hallux Rigidus

Hallux rigidus is degenerative arthritis of the first metatarsophalangeal joint characterized by pain and stiffness in the joint with limitation of motion and functional impairment. Recently, bone grafts have been introduced in orthopedic procedures, namely osteosynthesis and arthrodesis. Allografts can induce bone formation, provide support for vascular and bone ingrowth and have a low risk of immunological rejection. A 52-year-old female patient with hallux rigidus underwent arthrodesis of the first metatarsophalangeal joint using Shark Screw^® made of allogenic cortical bone. Corrective surgery was performed after 10 weeks, and a 5 × 3 mm large part of the Shark Screw^® with the surrounding patient's bone was removed. A histological evaluation revealed a vascularized graft with the newly formed compact lamellar bone fitting exactly to the cortical graft. The bone surface was lined by plump osteoblasts with osteoid production, and osteocytes were present in the lacunae. The arthrodesis of the first metatarsophalangeal joint using an allogenic cortical bone graft results in fast, primary bone healing without immunological rejection. This case suggests that the cortical allograft is a good and safe treatment option with an excellent graft incorporation into the host bone. However, as the literature evaluating the histology of different bone grafts is scarce, further high-level evidence studies with adequate sample sizes are needed to confirm our findings.

Osteogenesis of 3D-Printed PCL/TCP/bdECM Scaffold Using Adipose-Derived Stem Cells Aggregates; An Experimental Study in the Canine Mandible

Three-dimensional (3D) printing is perceived as an innovative tool for change in tissue engineering and regenerative medicine based on research outcomes on the development of artificial organs and tissues. With advances in such technology, research is underway into 3D-printed artificial scaffolds for tissue recovery and regeneration. In this study, we fabricated artificial scaffolds by coating bone demineralized and decellularized extracellular matrix (bdECM) onto existing 3D-printed polycaprolactone/tricalcium phosphate (PCL/TCP) to enhance osteoconductivity and osteoinductivity. After injecting adipose-derived stem cells (ADSCs) in an aggregate form found to be effective in previous studies, we examined the effects of the scaffold on ossification during mandibular reconstruction in beagle dogs. Ten beagles were divided into two groups: group A (PCL/TCP/bdECM + ADSC injection; n = 5) and group B (PCL/TCP/bdECM; n = 5). The results were analyzed four and eight weeks after intervention. Computed tomography (CT) findings showed that group A had more diffuse osteoblast tissue than group B. Evidence of infection or immune rejection was not detected following histological examination. Goldner trichrome (G/T) staining revealed rich ossification in scaffold pores. ColI, Osteocalcin, and Runx2 gene expressions were determined using real-time polymerase chain reaction. Group A showed greater expression of these genes. Through Western blotting, group A showed a greater expression of genes that encode ColI, Osteocalcin, and Runx2 proteins. In conclusion, intervention group A, in which the beagles received the additional ADSC injection together with the 3D-printed PCL/TCP coated with bdECM, showed improved mandibular ossification in and around the pores of the scaffold.

Scaffolds from Self-Assembling Tetrapeptides Support 3D Spreading, Osteogenic Differentiation, and Angiogenesis of Mesenchymal Stem Cells

The apparent rise of bone disorders demands advanced treatment protocols involving tissue engineering. Here, we describe self-assembling tetrapeptide scaffolds for the growth and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The rationally designed peptides are synthetic amphiphilic self-assembling peptides composed of four amino acids that are nontoxic. These tetrapeptides can quickly solidify to nanofibrous hydrogels that resemble the extracellular matrix and provide a three-dimensional (3D) environment for cells with suitable mechanical properties. Furthermore, we can easily tune the stiffness of these peptide hydrogels by just increasing the peptide concentration, thus providing a wide range of peptide hydrogels with different stiffnesses for 3D cell culture applications. Since successful bone regeneration requires both osteogenesis and vascularization, our scaffold was found to be able to promote angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro. The results presented suggest that ultrashort peptide hydrogels are promising candidates for applications in bone tissue engineering.

Poly(Glycerol Sebacate) in Biomedical Applications-A Review of the Recent Literature

Poly(glycerol sebacate) (PGS) continues to attract attention for biomedical applications owing to its favorable combination of properties. Conventionally polymerized by a two-step polycondensation of glycerol and sebacic acid, variations of synthesis parameters, reactant concentrations or by specific chemical modifications, PGS materials can be obtained exhibiting a wide range of physicochemical, mechanical, and morphological properties for a variety of applications. PGS has been extensively used in tissue engineering (TE) of cardiovascular, nerve, cartilage, bone and corneal tissues. Applications of PGS based materials in drug delivery systems and wound healing are also well documented. Research and development in the field of PGS continue to progress, involving mainly the synthesis of modified structures using copolymers, hybrid, and composite materials. Moreover, the production of self-healing and electroactive materials has been introduced recently. After almost 20 years of research on PGS, previous publications have outlined its synthesis, modification, properties, and biomedical applications, however, a review paper covering the most recent developments in the field is lacking. The present review thus covers comprehensively literature of the last five years on PGS-based biomaterials and devices focusing on advanced modifications of PGS for applications in medicine and highlighting notable advances of PGS based systems in TE and drug delivery.

Effect of a plasma synthesized polypyrrole coverage on polylactic acid/hydroxyapatite scaffolds for bone tissue engineering

Composite biomaterials are solids that contain two or more different materials, combining the properties of their components to restore or improve the function of tissues. In this study, we report the generation of electrospun matrices with osteoconductive properties and porosity using the combination of a biodegradable polyester, polylactic acid (PLA), and hydroxyapatite (HA). Additionally, we report the effects of modifying these matrices through plasma polymerization of pyrrole on the growth and osteogenic differentiation of rabbit bone marrow stem cells. Cells were isolated, seeded and cultured on biomaterials for periods between 7 and 28 days. The matrices we obtained were formed by nano and microfibers containing up to 35.7 wt% HA, presenting a variety of apparent pore sizes to allow for the passage of nutrients to bone cells. Scanning electron microscopy showed that the fibers were coated with polypyrrole doped with iodine, and MTT assay demonstrated this increased cell proliferation and significantly improved cell viability due to the adhesive properties of the polymer. Our results show that PLA/HA/Pyrrole/Iodine matrices are favorable for bone tissue engineering.

Functional repair of critically sized femoral defects treated with bioinspired titanium gyroid-sheet scaffolds

Despite the innate ability for bone to remodel and repair, its regeneration has a limit. In these cases of critically sized bone defects (CSBD), the bone deficit must be repaired using reconstructive techniques that support immediate load bearing and encourage bone bridging across the defect. High-strength porous titanium implants offer a solution for treatment of CSBD in which the scaffold can support physiological loads, provide a matrix to guide ingrowth, and carry graft materials and/or biologics. Fabrication of titanium meta-materials via additive manufacturing (AM) has unlocked the potential to modulate mechanical and biological performance to achieve a combination of properties previously unachievable. Meta-material scaffolds with topology based on triply periodic minimal surfaces (TPMS) have gained increasing interest for use in biomedical applications due to their bioinspired nature. Despite enthusiasm for TPMS-based titanium scaffolds due to their high strength to stiffness ratio, high permeability, and curvature similar to trabecular bone, there is little preclinical evidence to support their in vivo response in bone. The present study sought to evaluate the performance of gyroid-sheet titanium scaffolds produced via AM to repair a critically size femoral cortical bone defect in rats. Empty gyroid-sheet scaffolds were shown to repair segmental defects with up to 38% of torsional strength and 54% torsional stiffness of the intact femur (control) at 12-weeks. Gyroid-sheet scaffolds carrying recombinant bone morphogenic protein-2 demonstrated bridging bone growth across the length of the defect, with torsional strength and stiffness superior to that of the intact controls.

The degradation behavior of calcium-rich hydroxyapatite foams in vitro

Hydroxyapatite (HA) is a well-known regenerative biomaterial. However, the slow degradation rate of HA is still an obstacle in clinical applications. In this study, we concentrated on investigating the degradation behavior of the calcium-rich HA foams, which had a demonstrated effect on blood differentiation in previous studies. The HA foams were processed by an emulsion method and were infiltrated with calcium nitrate to create a calcium carbonate second phase, heterogeneously distributed on and under the surface of the foam. During the 28-day solubility test, the calcium carbonate phase contributed to enhanced Ca²⁺ ion release into the saline compared to phase pure HA foams. Both types of foams were biocompatible as demonstrated by human endothelial cell culture on their surface. The release of calcium ions, the degradation behavior, and the endothelial cell differentiation behavior suggest this biphasic ceramic is a candidate for bone marrow in vitro culture and a possible bone substitute material.

Cobalt Chromium Molybdenum Surface Modifications Alter the Osteogenic Differentiation Potential of Human Mesenchymal Stem Cells

Surface roughness on orthopedic implant materials has been shown to be highly influential on the behavior of osteogenic cells. Mesenchymal stem and progenitor cells (MSPCs) migrate to the interface, adhere, proliferate, and differentiate into osteoblasts, which subsequently form bone matrix. Modifications of the implant surfaces should accelerate this process and improve biocompatibility. In this study, five surface topographies on cobalt chromium molybdenum (CoCrMo) were engineered to examine the influence on MSPCs. Scanning electron microscopy revealed significant differences in the morphology of untreated CoCrMo discs in comparison with CoCrMo with a titanium nitride (TiN) coating, polished and porous coated CoCrMo surfaces, and CoCrMo with a pure titanium (cpTi) coating. Elemental analysis was performed using energy-dispersive X-ray spectroscopy (EDX). Human primary MSPCs were expanded from tissue samples of spongiosa bone and characterized according to the criteria of the International Society for Cellular Therapy. The characteristic phenotype of MSPC was confirmed by flow cytometry and multilineage differentiation. Alcaline phosphatase and osteopontin expression increased significantly in all groups about 5-fold and 10-fold, respectively, in comparison to the undifferentiated controls. The porous coated surface showed a reduced expression of osteogenic markers. Due to the osteogenic differentiation, the expression of integrin α5β1, which is particularly important for cell-material contact, increased 4–7-fold. In the dynamic process of bone biology, MSPCs cultured and differentiated on cpTi, showed significant upregulation of IL6 and leptin.

Advancing application of mesenchymal stem cell-based bone tissue regeneration

Reconstruction of bone defects, especially the critical-sized defects, with mechanical integrity to the skeleton is important for a patient's rehabilitation, however, it still remains challenge. Utilizing biomaterials of human origin bone tissue for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural bone tissue with regard to its properties. However, not only efficacious and safe but also cost-effective and convenient are important for regenerative biomaterials to achieve clinical translation and commercial success. Advances in our understanding of regenerative biomaterials and their roles in new bone formation potentially opened a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multicomponent construction of native extracellular matrix (ECM) for cell accommodation, the ECM-mimicking biomaterials and the naturally decellularized ECM scaffolds were used to create new tissues for bone restoration. On the other hand, with the going deep in understanding of mesenchymal stem cells (MSCs), they have shown great promise to jumpstart and facilitate bone healing even in diseased microenvironments with pharmacology-based endogenous MSCs rescue/mobilization, systemic/local infusion of MSCs for cytotherapy, biomaterials-based approaches, cell-sheets/-aggregates technology and usage of subcellular vesicles of MSCs to achieve scaffolds-free or cell-free delivery system, all of them have been shown can improve MSCs-mediated regeneration in preclinical studies and several clinical trials. Here, following an overview discussed autogenous/allogenic and ECM-based bone biomaterials for reconstructive surgery and applications of MSCs-mediated bone healing and tissue engineering to further offer principles and effective strategies to optimize MSCs-based bone regeneration.

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Focusing on MSCs based bone regeneration.

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Discussed cytotherapy, cell-free therapies and cell-aggregates technology in detail.

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Stating the approaches of MSCs in diseased microenvironments.

[Diamond concept for treatment of nonunions and bone defects]

Nonunions represent a very heterogeneous, rare and sometimes very complex disease picture. The causes, localization and degree of expression show a very high variability, which makes it difficult to establish uniform treatment standards. Nevertheless, the process of bone healing is subject to some essential factors, which should be ensured for a successful treatment. Over the years these factors have been better researched and were taken into consideration for the diamond concept, which was first published by Giannoudis et al. in 2007. This provides the physician with a concept that does not neglect the heterogeneity of the disease picture and is an aid to decision making for the treatment regimen in individual cases in order to guarantee the best biological and mechanical conditions. The diamond concept is nowadays widely used and many studies have already demonstrated a successful application. It must be understood as a framework, in which the various treatment options available (bone substitute materials, mesenchymal stem cells, osteosynthesis procedures etc.) are incorporated into the individual factors and therefore provides the physician with a certain freedom of choice in the selection of tools. Additionally, it is not a rigid corset and subject to medical scientific progress in its factors, so that it is exciting to see which new developments will be incorporated in the future.

Perspectives on Synthetic Materials to Guide Tissue Regeneration for Osteochondral Defect Repair

Regenerative engineering holds the potential to treat clinically pervasive osteochondral defects (OCDs). In a synthetic materials-guided approach, the scaffold's chemical and physical properties alone instruct cellular behavior in order to effect regeneration, referred to herein as "instructive" properties. While this alleviates the costs and off-target risks associated with exogenous growth factors, the scaffold must be potently instructive to achieve tissue growth. Moreover, toward achieving functionality, such a scaffold should also recapitulate the spatial complexity of the osteochondral tissues. Thus, in addition to the regeneration of the articular cartilage and underlying cancellous bone, the complex osteochondral interface, composed of calcified cartilage and subchondral bone, should also be restored. In this Perspective, we highlight recent synthetic-based, instructive osteochondral scaffolds that have leveraged new material chemistries as well as innovative fabrication strategies. In particular, scaffolds with spatially complex chemical and morphological features have been prepared with electrospinning, solvent-casting-particulate-leaching, freeze-drying, and additive manufacturing. While few synthetic scaffolds have advanced to clinical studies to treat OCDs, these recent efforts point to the promising use of the chemical and physical properties of synthetic materials for regeneration of osteochondral tissues.