3D printing technology and its combination with nanotechnology in bone tissue engineering.

With the graying of the world's population, the morbidity of age-related chronic degenerative bone diseases, such as osteoporosis and osteoarthritis, is increasing yearly, leading to an increased risk of bone defects, while current treatment methods face many problems, such as shortage of grafts and an incomplete repair. Therefore, bone tissue engineering offers an alternative solution for regenerating and repairing bone tissues by constructing bioactive scaffolds with porous structures that provide mechanical support to damaged bone tissue while promoting angiogenesis and cell adhesion, proliferation, and activity. 3D printing technology has become the primary scaffold manufacturing method due to its ability to precisely control the internal pore structure and complex spatial shape of bone scaffolds. In contrast, the fast development of nanotechnology has provided more possibilities for the internal structure and biological function of scaffolds. This review focuses on the application of 3D printing technology in bone tissue engineering and nanotechnology in the field of bone tissue regeneration and repair, and explores the prospects for the integration of the two technologies.

Cu-Sr Bilayer Bioactive Glass Nanoparticles/Polydopamine Functionalized Polyetheretherketone Enhances Osteogenic Activity and Prevents Implant-Associated Infections through Spatiotemporal Immunomodulation.

Key factors contributing to implantation failures include implant-associated infections (IAIs) and insufficient osseointegration of the implants. Polyetheretherketone (PEEK) is widely used in orthopedics, yet its clinical applications are restricted due to its poor osteogenic and antibacterial properties as well as inadequate immune responses. To overcome these drawbacks, a novel spatiotemporal immunomodulation approach is proposed, chelating Cu-Sr bilayer bioactive glass nanoparticles (CS-BGNs) onto the PEEK surface via polydopamine (PDA). The CS-BGNs possess a bilayer core-shell structure where copper is distributed in the outer layer and strontium is clustered in the inner layer. The results show that CS-BGNs/PDA functionalized PEEK demonstrates a controlled and sequential release of Cu2+ and Sr2+ . In the early stage, Cu2+ from the outer layer releases rapidly, while Sr2+ from the inner layer releases in the late stage. This well-ordered release pattern modulates the phenotypic transition of macrophages, which induces M1 polarization in the early stage and M2 polarization in the late stage. Combined with the direct effects of Cu2+ and Sr2+ , the spatiotemporal immunomodulation not only benefits the early antibacterial and tissue-healing process, but also promotes the long-term process of osseointegration, providing new perspectives on the design of novel immunomodulatory biomaterials.

ZnO nanoparticles attenuate polymer-wear-particle induced inflammatory osteolysis by regulating the MEK-ERK-COX-2 axis.

Background/Objectives: Advanced thermoplastic materials, such as polyether-ether-ketone (PEEK) and highly cross-linked polyethylene (HXLPE), have been increasingly used as orthopaedic implant materials. Similar to other implants, PEEK-on-HXLPE prostheses produce debris from polymer wear that may activate the immune response, which can cause osteolysis, and ultimately implant failure. In this study, we examined whether the anti-inflammatory properties of zinc oxide nanoparticles (ZnO NPs) could attenuate polymer wear particle-induced inflammation. Methods: RAW264.7 â€‹cells were cultured with PEEK or PE particles and gradient concentrations of ZnO NPs. Intracellular mRNA expression and protein levels of pro-inflammatory factors TNF-α, IL-1ß, and IL-6 were detected. An air pouch mouse model was constructed to examine the inflammatory response and expression of pro-inflammatory factors in vivo. Furthermore, an osteolysis rat model was used to evaluate the activation of osteoclasts and destruction of bone tissue induced by polymer particles with or without ZnO NPs. Protein expression of the MEK-ERK-COX-2 pathway was also examined by western blotting to elucidate the mechanism underlying particle-induced anti-inflammatory effects. Results: ZnO NPs (≤50 â€‹nm, 5 â€‹µg/mL) showed no obvious cytotoxicity and attenuated PEEK or PE particle-induced inflammation and inflammatory osteolysis by reducing MEK and ERK phosphorylation and decreasing COX-2 expression. Conclusion: ZnO NPs (≤50 â€‹nm, 5 â€‹µg/mL) attenuated polymer wear particle-induced inflammation via regulation of the MEK-ERK-COX-2 axis. Further, ZnO NPs reduced bone tissue damage caused by particle-induced inflammatory osteolysis. The translational potential of this article: Polymer wear particles can induce inflammation and osteolysis in the body after arthroplasty. ZnO NPs attenuated polymer particle-induced inflammation and inflammatory osteolysis. Topical use of ZnO NPs and blended ZnO NP/polymer composites may provide promising approaches for inhibiting polymer wear particle-induced inflammatory osteolysis, thus expanding the range of polymers used in joint prostheses.

3D printed porous sulfonated polyetheretherketone scaffold for cartilage repair: Potential and limitation.

Objective: The treatment of cartilage lesions has always been a difficult problem. Although cartilage tissue engineering provides alternative treatment options for cartilage lesions, biodegradable tissue engineering scaffolds have limitations. Methods: In this study, we constructed a porous PEEK scaffold via 3D printing, surface-engineered with concentrated sulfuric acid for 15 s (SPK-15), 30 s (SPK-30), and 60 s (SPK-60). We systematically evaluated the physical and chemical characteristics and biofunctionalities of the scaffolds, and then evaluated the macrophage polarization modulating ability and anti-inflammatory effects of the sulfonated PEEK, and observed the cartilage-protective effect of SPK using a co-culture study. We further evaluated the repair effect of PEEK and SPK by implanting the prosthetic scaffold into a cartilage defect in a rabbit model. Results: Compared to the PEEK, SPK-15 and SPK-60 scaffolds, SPK-30 has a good micro/nanostructure, appropriate biomechanical properties (compressive modulus, 43 ± 5 MPa; Shaw hardness, 20.6 ± 1.3 HD; close to native cartilage, 30 ± 8 MPa, 17.8 ± 0.8 HD), and superior biofunctionalities. Compared to PEEK, sulfonated PEEK can favor macrophage polarization to the M2 phenotype, which increases anti-inflammatory cytokine secretion. Furthermore, SPK can also prevent macrophage-induced cartilage degeneration. The in-vivo animal experiment demonstrates that SPK can favor new tissue ingrowth and integration, prevent peri-scaffold cartilage degeneration and patellar cartilage degeneration, inhibit inflammatory cytokine secretion, and promote cartilage function restoration. Conclusion: The present study confirmed that the 3D printed porous sulfonated PEEK scaffold could promote cartilage functional repair, and suggests a new promising strategy for treating cartilage defects with a functional prosthesis that spontaneously inhibits nearby cartilage degeneration. Translational potential of this article: In the present study, we propose a new cartilage repair strategy based on a porous, non-biodegradable polyetheretherketone (PEEK) scaffold, which may bring up a new treatment route for elderly patients with cartilage lesions in the future.

Porous Bioactive Prosthesis With Chitosan/Mesoporous Silica Nanoparticles Microspheres Sequentially and Sustainedly Releasing Platelet-Derived Growth Factor-BB and Kartogenin: A New Treatment Strategy for Osteoarticular Lesions.

Osteochondral lesions represent a major clinical challenge, especially in the elderly. Traditional treatment strategies, such as arthroplasty or tissue engineering, have limitations and drawbacks. In this study, we presented a new treatment concept for the application of an innovative porous bioactive prosthesis with regenerative activity for the treatment of osteoarticular lesions. For regenerative activity, we fabricated chitosan/mesoporous silica nanoparticles (CS/MSNs) composite microspheres via the microfluidic method as a dual-factor carrier for the sequential release of platelet-derived growth factor BB (PDGF-BB) and kartogenin (KGN). We then integrated the factor carrier and a nondegradable polyetheretherketone (PEEK) scaffold through a surface modification technique to construct the porous sulfonated PEEK (SPK) @polydopamine (polydopamine)-CS/MSNs scaffold. We systematically evaluated the biocompatibility and biofunctionality of the SPK@PDA-CS/MSNs scaffold and implanted the scaffold in an in vivo cartilage defect model in rabbits. These results suggest that the SPK@PDA-CS/MSNs scaffold is biocompatible, promotes cell migration, enhances chondrogenic differentiation of BMSCs in vitro, and promotes cartilage regeneration in vivo. The porous bioactive prosthesis with regenerative activity presented first in this study may comprise a new therapeutic concept for osteoarticular lesions.

Mg-BGNs/DCECM Composite Scaffold for Cartilage Regeneration: A Preliminary In Vitro Study.

Cartilage lesions can lead to progressive cartilage degeneration; moreover, they involve the subchondral bone, resulting in osteoarthritis (OA) onset and progression. Bioactive glasses, with the dual function of supporting both bone and cartilage regeneration, have become a promising biomaterial for cartilage/bone engineering applications. This is especially true for those containing therapeutic ions, which act as ion delivery systems and may further promote cartilage repair. In this study, we successfully fabricated Mg-containing bioactive glass nanospheres (Mg-BGNs) and constructed three different scaffolds, DCECM, Mg-BGNs-1/DCECM (1% Mg-BGNs), and Mg-BGNs-2/DCECM (10% Mg-BGNs) scaffold, by incorporating Mg-BGNs into decellularized cartilage extracellular matrix (DCECM). All three scaffolds showed favorable microarchitectural and ion controlled-release properties within the ideal range of pore size for tissue engineering applications. Furthermore, all scaffolds showed excellent biocompatibility and no signs of toxicity. Most importantly, the addition of Mg-BGNs to the DCECM scaffolds significantly promoted cell proliferation and enhanced chondrogenic differentiation induction of mesenchymal stem cells (MSCs) in pellet culture in a dose-dependent manner. Collectively, the multifunctional Mg-BGNs/DCECM composite scaffold not only demonstrated biocompatibility but also a significant chondrogenic response. Our study suggests that the Mg-BGNs/DCECM composite scaffold would be a promising tissue engineering tool for osteochondral lesions, with the ability to simultaneously stimulate articular cartilage and subchondral bone regeneration.

p300/CBP inhibitor A-485 inhibits the differentiation of osteoclasts and protects against osteoporotic bone loss.

Osteoporosis is one of the most common metabolic bone diseases among pre- and post-menopausal women. Despite numerous advances in the treatment of osteoporosis in recent years, the outcomes remain poor due to severe side effects. In this study, we investigated whether A-485, a highly selective catalytic p300/CBP inhibitor, could attenuate RANKL-induced osteoclast differentiation and explored the underlying molecular mechanisms. The protective role of A-485 in osteoporosis was verified using a mouse model of ovariectomy (OVX)-induced bone loss and micro-CT scanning. A-485 inhibited RANKL-induced osteoclast differentiation in vitro by reducing the number of tartrate-resistant acid phosphatase-positive osteoclasts without inducing significant cytotoxicity. In particular, A-485 dose-dependently disrupted F-actin ring formation and downregulated the expression of genes associated with osteoclast differentiation, such as CTSK, c-Fos, TRAF6, VATPs-d2, DC-STAMP, and NFATc1, in a time- and dose-dependent manner. Moreover, A-485 inhibited the RANKL-induced phosphorylation of MAPK pathways and attenuated OVX-induced bone loss in the mouse model while rescuing the loss of bone mineral density. Our in vitro and in vivo findings suggest for the first time that A-485 has the potential to prevent postmenopausal osteoporosis and could therefore be considered as a therapeutic molecule against osteoporosis.

A partial hemi-resurfacing preliminary study of a novel magnetic resonance imaging compatible polyetheretherketone mini-prosthesis for focal osteochondral defects.

BACKGROUND: The use of partial articular resurfacing surgery with a mini-implant has been gradually increasing; the implant is mainly made of cobalt-chromium metal material, and cartilage changes cannot be monitored after implantation. Thus, we aimed to develop a novel local articular resurfacing polyetheretherketone (PEEK) mini-implant and investigate its feasibility for postoperative magnetic resonance imaging (MRI) monitoring of implant location, bone changes, and cartilage degeneration without artefacts. METHODS: Nine skeletally mature female standardised goats were used and divided into the sham, PEEK, and cobalt-chromium-molybdenum alloy (Co-Cr-Mo) groups. The animals underwent local articular resurfacing operation with Co-Cr-Mo alloy (Co-Cr-Mo group) and PEEK (PEEK group) mini-implants. X-ray, computed tomography, and MRI examinations were performed at 12 weeks postoperatively. The sham group underwent a similar surgical procedure to expose the femoral head but without implantation. Gross necropsy and surface topography measurement of the articular cartilage of the acetabulum were performed after sacrificing the animals. Imaging artefacts and opposing cartilage degeneration in the acetabulum were also examined. RESULTS: Cartilage damage occurred in both the Co-Cr-Mo and PEEK groups, and the damaged cartilage area was markedly larger in the Co-Cr-Mo group than in the PEEK group, as assessed by gross necropsy and histological staining. The mean surface roughness of the opposing cartilage was approximately 65.3, 117.4, and 188.4 â€‹µm â€‹at 12 weeks in the sham, PEEK, and Co-Cr-Mo groups, respectively. The Co-Cr-Mo mini-implant was visualised on radiographs, but computed tomography and MR images were markedly affected by artefacts, whereas the opposing cartilage and surrounding tissue were clear on MR images in the PEEK group. Opposing cartilage damage and subchondral bone marrow oedema could be detected by MRI in the PEEK group. CONCLUSIONS: The PEEK mini-implant can be a novel alternative to the Co-Cr-Mo mini-implant in articular resurfacing to treat focal osteochondral defects with less cartilage damage. It is feasible to postoperatively monitor the PEEK implant location, surrounding bone changes, and opposing cartilage degeneration by MRI without artefacts. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The use of MRI to monitor changes in the opposing cartilage after prosthesis implantation has not been widely applied because MR images are generally affected by artefacts generated by the metal prosthesis. This study revealed that the PEEK mini-implant can be a novel alternative to the Co-Cr-Mo mini-implant in articular resurfacing to treat focal osteochondral defects, and it is feasible to monitor the PEEK implant location, surrounding bone changes, and opposing cartilage damage/degeneration by MRI without artefacts postoperatively.

Overcoming Planktonic and Intracellular Staphylococcus aureus-Associated Infection with a Cell-Penetrating Peptide-Conjugated Antimicrobial Peptide.

Staphylococcus aureus is a primary pathogen responsible for causing postoperative infections as it survives and persists in host cells, including osteoblasts and macrophages. These cells then serve as reservoirs resulting in chronic infections. Most traditional antibiotics have poor effects on intracellular S. aureus because they cannot enter the cell. Herein, a cell-penetrating peptide TAT-KR-12 was derived from the trans-activating transcription (TAT) peptide and KR-12 (residues 18-29 of human cathelicidin LL-37). The TAT acts as a "trojan horse" to deliver KR-12 peptide into the cells to kill S. aureus. Moreover, effective antibacterial properties and biocompatibility were observed in vitro, demonstrating that TAT-KR-12 is effective not only in eliminating planktonic S. aureus, but also in eliminating intracellular S. aureus cells in vitro. TAT-KR-12, as with LL-37, also elicits strong anti-inflammatory activities in LPS-stimulated macrophages, as demonstrated by significant inhibition of NO, TNF-α, and IL-1ß expression and secretion from LPS-stimulated RAW264.7 cells. In the subcutaneous infection mouse model of planktonic and intracellular infections, the growth of S. aureusin vivo is evidently inhibited without cytotoxicity. These results suggest that the novel antimicrobial TAT-KR-12 may prove to be an effective treatment option to overcome antibiotic resistance caused by intracellular bacterial infections.

KR-12 coating of polyetheretherketone (PEEK) surface via polydopamine improves osteointegration and antibacterial activity in vivo.

Polyetheretherketone (PEEK) is considered to be a promising bone implant material owing to its biocompatibility and elastic modulus, which is similar to that of natural bone. However, the clinical potential of PEEK is severely limited by its bioinertness, which leads to poor osseointegration, and the lack of antibacterial properties. In this study, the antimicrobial peptide, KR-12, was immobilized on the surface of PEEK implants with the assistance of polydopamine (PDA) to inhibit bacterial infection as well as to promote osteogenesis and osseointegration. Compared to unmodified PEEK, the PEEK with immobilized KR-12 showed significantly improved antibacterial activity against Staphylococcus aureus (ATCC 25923), both in vitro and in vivo. For the in vitro and in vivo evaluation of the osteogenic properties of modified PEEK, rat bone mesenchymal stem cells (rBMSCs) and a rat femoral defect model were used, respectively. The in vitro studies showed that compared to rBMSCs treated with unmodified PEEK, those treated with KR-12-coated PEEK exhibited improved adhesion, proliferation, and osteogenic differentiation. Moreover, micro-computed tomography and histological analysis suggested that the KR-12 coating promoted osteointegration in vivo in rat femurs. Taken together, these results suggest that the KR-12 coating could improve the antibacterial ability of pure or PDA-coated PEEK against Staphylococcus aureus (ATCC 25923), both in vitro and in vivo. Overall, KR-12 combined with the PDA film coating synergistically induced osteogenic effects both in vitro and in vivo. Thus, the surface-modified material, which exhibits both anti-bacterial and osteointegration properties, shows considerable potential for use as an orthopedic implant.