3D printed strontium-zinc-phosphate bioceramic scaffolds with multiple biological functions for bone tissue regeneration

LIPUS activated piezoelectric pPLLA/SrSiO3 composite scaffold promotes osteochondral regeneration through P2RX1 mediated Ca2+ signaling pathway

Addressing the concurrent repair of cartilage and subchondral bone presents a significant challenge yet is crucial for the effective treatment of severe joint injuries. This study introduces a novel biodegradable composite scaffold, integrating piezoelectric poly-l-lactic acid (pPLLA) with strontium-enriched silicate bioceramic (SrSiO3). This innovative scaffold continually releases bioactive Sr2+ and SiO32- ions while generating an electrical charge under low-intensity pulsed ultrasound (LIPUS) stimulation, a clinically recognized method. The scaffold's unique dual action, emanating both chemical and electrical signals, activates the purinergic receptor P2X 1 (P2RX1) calcium ion channel, promoting an influx of intracellular calcium ions. This process results in a synergistic enhancement of both chondrogenic activities of rat chondrocytes (rCCs) and osteogenic activities of rat bone marrow mesenchymal stem cells (rBMSCs). Furthermore, the scaffold's effectiveness in integrating articular cartilage and subchondral bone repair is confirmed in a rat model of joint osteochondral injury. This study thereby offers a groundbreaking approach for treating severe osteoarticular cartilage defects.

Immunomodulation in Bone Tissue Engineering: Recent Advancements in Scaffold Design and Biological Modifications for Enhanced Regeneration

Bone defects, whether caused by trauma, cancer, infectious diseases, or surgery, can significantly impair people's quality of life. Although autografts are the gold standard for treating bone defects, they often fall short in adequately forming bone tissue. The field of bone tissue engineering has made strides in using scaffolds with various biomaterials, stem cells, and growth factors to enhance bone healing. However, some biological structures do not yield satisfactory therapeutic outcomes for new bone formation. Recent studies have shed light on the crucial role of immunomodulation, specifically the interaction between the implanted scaffold and host immune systems, in bone regeneration. Immune cells, particularly macrophages, are pivotal in the inflammatory response, angiogenesis, and osteogenesis. This review delves into the immune system's mechanism toward foreign bodies and the recent advancements in scaffolds' physical and biological properties that foster bone regeneration by modulating macrophage polarization to an anti-inflammatory phenotype and enhancing the osteoimmune microenvironment.

Advances in 3D printing technology for preparing bone tissue engineering scaffolds from biodegradable materials

Introduction

Bone tissue engineering (BTE) provides an effective repair solution by implanting osteoblasts or stem cells into biocompatible and biodegradable scaffolds to promote bone regeneration. In recent years, the rapid development of 3D bioprinting has enabled its extensive application in fabricating BTE scaffolds. Based on three-dimensional computer models and specialized "bio-inks," this technology offers new pathways for customizing BTE scaffolds. This study reviews the current status and future prospects of scaffold materials for BTE in 3D bioprinting.

Methods

This literature review collected recent studies on BTE and 3D bioprinting, analyzing the advantages and limitations of various scaffold materials for 3D printing, including bioceramics, metals, natural polymers, and synthetic polymers. Key characteristics like biocompatibility, mechanical properties, and degradation rates of these materials were systematically compared.

Results

The study highlights the diverse performances of materials used in BTE scaffolds. Bioceramics exhibit excellent biocompatibility but suffer from brittleness; metals offer high strength but may induce chronic inflammation; natural polymers are biocompatible yet have poor mechanical properties, while synthetic polymers offer strong tunability but may produce acidic by-products during degradation. Additionally, integrating 3D bioprinting with composite materials could enhance scaffold biocompatibility and mechanical properties, presenting viable solutions to current challenges.

Discussion

This review summarizes recent advances in 3D bioprinting for BTE scaffold applications, exploring the strengths and limitations of various materials and proposing composite material combinations to improve scaffold performance. By optimizing material selection and combinations, 3D bioprinting shows promise for creating customized scaffolds, offering a new technical route for clinical applications of BTE. This research provides a unique perspective and theoretical support for advancing 3D bioprinting technology in bone regeneration, outlining future directions for BTE materials and 3D bioprinting technology development.

Ti3C2Tx MXene-Decorated 3D-Printed Ceramic Scaffolds for Enhancing Osteogenesis by Spatiotemporally Orchestrating Inflammatory and Bone Repair Responses

Inflammatory responses play a central role in coordinating biomaterial-mediated tissue regeneration. However, precise modulation of dynamic variations in microenvironmental inflammation post-implantation remains challenging. In this study, the traditional β-tricalcium phosphate-based scaffold is remodeled via ultrathin MXene-Ti3C2 decoration and Zn2+/Sr2+ ion-substitution, endowing the scaffold with excellent reactive oxygen species-scavenging ability, near-infrared responsivity, and enhanced mechanical properties. The induction of mild hyperthermia around the implant via periodic near-infrared irradiation facilitates spatiotemporal regulation of inflammatory cytokines secreted by a spectrum of macrophage phenotypes. The process initially amplifies the pro-inflammatory response, then accelerates M1-to-M2 macrophage polarization transition, yielding a satisfactory pattern of osteo-immunomodulation during the natural bone healing process. Later, sustained release of Zn2+/Sr2+ ions with gradual degradation of the 3D scaffold maintains the favorable reparative M2-dominated immunological microenvironment that supports new bone mineralization. Precise temporal immunoregulation of the bone healing process by the intelligent 3D scaffold enhances bone regeneration in a rat cranial defect model. This strategy paves the way for the application of β-tricalcium phosphate-based materials to guide the dynamic inflammatory and bone tissue responses toward a favorable outcome, making clinical treatment more predictable and durable. The findings also demonstrate that near-infrared irradiation-derived mild hyperthermia is a promising method of immunomodulation.

Improvement in mechanical strength and biological function of 3D-printed trimagnesium phosphate bioceramic scaffolds by incorporating strontium orthosilicate

Trimagnesium phosphate (TMP) bioceramic scaffolds are deemed as promising bone grafts, but their mechanical and biological properties are yet to be improved. In the study, strontium orthosilicate (SrOS) was used to modify the TMP scaffolds, whose macroporous structure was constructed by the filament deposition-type 3D printing method. The new phases of SrMg2(PO4)2 and Sr2MgSi2O7, which showed nanocrystalline topography, were produced in the 3D-printed TMP/SrOS bioceramic composite scaffolds. The compressive strength (1.8-64.1 MPa) and porosity (39.7%-71.4%) of the TMP/SrOS scaffolds could be readily tailored by changing the amounts of SrOS additives and the sintering temperature. The TMP/SrOS scaffolds gradually degraded in the aqueous solution, consequently releasing ions of magnesium, strontium and silicon. In contrast with the TMP scaffolds, the TMP/SrOS bioceramic scaffolds had profoundly higher compressive strength, and enhanced cell proliferative and osteogenic activities. The TMP/SrOS scaffolds incorporated with 5 wt% SrOS had the highest mechanical strength and beneficial cellular function, which made them promising for treating different sites of bone defects.

Incorporation of Zinc-Strontium Phosphate into Gallic Acid-Gelatin Composite Hydrogel with Multiple Biological Functions for Bone Tissue Regeneration

Large bone defects resulting from fractures and diseases have become a significant medical concern, usually impeding spontaneous healing through the body's self-repair mechanism. Calcium phosphate (CaP) bioceramics are widely utilized for bone regeneration, owing to their exceptional biocompatibility and osteoconductivity. However, their bioactivities in repairing healing-impaired bone defects characterized by conditions such as ischemia and infection remain limited. Recently, an emerging bioceramics zinc-strontium phosphate (ZSP, Zn2Sr(PO4)2) has received increasing attention due to its remarkable antibacterial and angiogenic abilities, while its plausible biomedical utility on tissue regeneration is nonetheless few. In this study, gallic acid-grafted gelatin (GGA) with antioxidant properties was injected into hydrogels to scavenge reactive oxygen species and regulate bone microenvironment while simultaneously incorporating ZSP to form GGA-ZSP hydrogels. The GGA-ZSP hydrogel exhibits low swelling, and in vitro cell experiments have demonstrated its favorable biocompatibility, osteogenic induction potential, and ability to promote vascular regeneration. In an in vivo bone defect model, the GGA-ZSP hydrogel significantly enhanced the bone regeneration rates. This study demonstrated that the GGA-ZSP hydrogel has pretty environmentally friendly therapeutic effects in osteogenic differentiation and massive bone defect repair.

3D-printed porous zinc scaffold combined with bioactive serum exosomes promotes bone defect repair in rabbit radius

Currently, the repair of large bone defects still faces numerous challenges, with the most crucial being the lack of large bone grafts with good osteogenic properties. In this study, a novel bone repair implant (degradable porous zinc scaffold/BF Exo composite implant) was developed by utilizing laser melting rapid prototyping 3D printing technology to fabricate a porous zinc scaffold, combining it under vacuum conditions with highly bioactive serum exosomes (BF EXO) and Poloxamer 407 thermosensitive hydrogel. The electron microscope revealed the presence of tea saucer-shaped exosomes with a double-layered membrane structure, ranging in diameter from 30-150 nm, with an average size of 86.3 nm and a concentration of 3.28E+09 particles/mL. In vitro experiments demonstrated that the zinc scaffold displayed no significant cytotoxicity, and loading exosomes enhanced the zinc scaffold's ability to promote osteogenic cell activity while inhibiting osteoclast activity. In vivo experiments on rabbits indicated that the hepatic and renal toxicity of the zinc scaffold decreased over time, and the loading of exosomes alleviated the hepatic and renal toxic effects of the zinc scaffold. Throughout various stages of repairing radial bone defects in rabbits, loading exosomes reinforced the zinc scaffold's capacity to enhance osteogenic cell activity, suppress osteoclast activity, and promote angiogenesis. This effect may be attributed to BF Exo's regulation of p38/STAT1 signaling. This study signifies that the combined treatment of degradable porous zinc scaffolds and BF Exo is an effective and biocompatible strategy for bone defect repair therapy.

New 3D Printed Scaffolds Based on Walstromite Synthesized by Sol-Gel Method

This study explores the potential utilization of walstromite (BaCa2Si3O9) as a foundational material for creating new bioceramics in the form of scaffolds through 3D printing technology. To achieve this objective, this study investigates the chemical-mineralogical, morphological, and structural characteristics, as well as the biological properties, of walstromite-based bioceramics. The precursor mixture for walstromite synthesis is prepared through the sol-gel method, utilizing pure reagents. The resulting dried gelatinous precipitate is analyzed through complex thermal analysis, leading to the determination of the optimal calcination temperature. Subsequently, the calcined powder is characterized via X-ray diffraction and scanning electron microscopy, indicating the presence of calcium and barium silicates, as well as monocalcium silicate. This powder is then employed in additive 3D printing, resulting in ceramic scaffolds. The specific ceramic properties of the scaffold, such as apparent density, absorption, open porosity, and compressive strength, are assessed and fall within practical use limits. X-ray diffraction analysis confirms the formation of walstromite as a single phase in the ceramic scaffold. In vitro studies involving immersion in simulated body fluid (SBF) for 7 and 14 days, as well as contact with osteoblast-like cells, reveal the scaffold's ability to form a phosphate layer on its surface and its biocompatibility. This study concludes that the walstromite-based ceramic scaffold exhibits promising characteristics for potential applications in bone regeneration and tissue engineering.

Zinc-based biomaterials for bone repair and regeneration: mechanism and applications

Zinc (Zn) is one of the most important trace elements in the human body and plays a key role in various physiological processes, especially in bone metabolism. Zn-containing materials have been reported to enhance bone repair through promoting cell proliferation, osteogenic activity, angiogenesis, and inhibiting osteoclast differentiation. Therefore, Zn-based biomaterials are potential substitutes for traditional bone grafts. In this review, the specific mechanisms of bone formation promotion by Zn-based biomaterials were discussed, and recent developments in their application in bone tissue engineering were summarized. Moreover, the challenges and perspectives of Zn-based biomaterials were concluded, revealing their attractive potential and development directions in the future.

Influence of Ag and/or Sr Dopants on the Mechanical Properties and In Vitro Degradation of β-Tricalcium Phosphate-Based Ceramics

β-tricalcium phosphate has good biodegradability and biocompatibility; it is widely perceived as a good material for treating bone deficiency. In this research, different contents of strontium (Sr) and silver (Ag) ion-doped β-tricalcium phosphate powders were prepared using the sol-gel method. After obtaining the best ratio of pore-forming agent and binder, the as-synthesized powders were sintered in a muffle for 5 h at 1000 °C to obtain the samples. Then, these samples were degraded in vitro in simulated body fluids. The samples were tested using a series of characterization methods before and after degradation. Results showed that the amount of Sr and/or Ag doping had an effect on the crystallinity and structural parameters of the samples. After degradation, though the compressive strength of these samples decreased overall, the compressive strength of the undoped samples was higher than that of the doped samples. Notably, apatite-like materials were observed on the surface of the samples. All the results indicate that Sr and/or Ag β-TCP has good osteogenesis and proper mechanical properties; it will be applied as a prospective biomaterial in the area of bone repair.

A 3D-printed orthopedic implant with dual-effect synergy based on MoS2 and hydroxyapatite nanoparticles for tumor therapy and bone regeneration

Treatments for malignant bone tumors are urgently needed to be developed due to the dilemma of precise resection of tumor tissue and subsequent bone defects. Although polyether-ether-ketone (PEEK) has widely attracted attention in the orthopedic field, its bioinertness and poor osteogenic properties significantly restrict its applications in bone tumor treatment. To tackle the daunting issue, we use a hydrothermal technique to fabricate novel PEEK scaffolds modified with molybdenum disulfide (MoS₂) nanosheets and hydroxyapatite (HA) nanoparticles. Our dual-effect synergistic PEEK scaffolds exhibit perfect photothermal therapeutic (PTT) property dependent on molybdous ion (Mo²⁺) concentration and laser power density, superior to conventional PEEK scaffolds. Under near-infrared (NIR) irradiation, the viability of MG63 osteosarcoma cells is significantly reduced by modified PEEK scaffolds, indicating a tumor-killing potential in vitro. Furthermore, the incorporation of HA nanoparticles on the surface of PEEK bolsters proliferation and adherence of MC3T3-E1 cells, boosting mineralization for further bone defect repair. The results of micro-computed tomography (micro-CT) and histological analysis of 4-week treated rat femora demonstrate the preeminent photothermal and osteogenesis capacity of 3D-printed modified scaffolds in vivo. In conclusion, the dual-effect synergistic orthopedic implant with photothermal anticancer property and osteogenic induction activity strikes a balance between tumor treatment and bone development promotion, offering a promising future therapeutic option.