3D printed polylactic acid/gelatin-nano-hydroxyapatite/platelet-rich plasma scaffold for critical-sized skull defect regeneration

Emerging Biomedical and Clinical Applications of 3D-Printed Poly(Lactic Acid)-Based Devices and Delivery Systems

Poly(lactic acid) (PLA) is widely used in the field of medicine due to its biocompatibility, versatility, and cost-effectiveness. Three-dimensional (3D) printing or the systematic deposition of PLA in layers has enabled the fabrication of customized scaffolds for various biomedical and clinical applications. In tissue engineering and regenerative medicine, 3D-printed PLA has been mostly used to generate bone tissue scaffolds, typically in combination with different polymers and ceramics. PLA's versatility has also allowed the development of drug-eluting constructs for the controlled release of various agents, such as antibiotics, antivirals, anti-hypertensives, chemotherapeutics, hormones, and vitamins. Additionally, 3D-printed PLA has recently been used to develop diagnostic electrodes, prostheses, orthoses, surgical instruments, and radiotherapy devices. PLA has provided a cost-effective, accessible, and safer means of improving patient care through surgical and dosimetry guides, as well as enhancing medical education through training models and simulators. Overall, the widespread use of 3D-printed PLA in biomedical and clinical settings is expected to persistently stimulate biomedical innovation and revolutionize patient care and healthcare delivery.

Evaluation of new bone formation in critical-sized rat calvarial defect using 3D printed polycaprolactone/tragacanth gum-bioactive glass composite scaffolds

Critical-sized bone defects are a major challenge in reconstructive bone surgery and usually fail to be treated due to limited remaining bone quality and extensive healing time. The combination of 3D-printed scaffolds and bioactive materials is a promising approach for bone tissue regeneration. In this study, 3D-printed alkaline-treated polycaprolactone scaffolds (M-PCL) were fabricated and integrated with tragacanth gum- 45S5 bioactive glass (TG-BG) to treat critical-sized calvarial bone defects in female adult Wistar rats. After a healing period of four and eight weeks, the new bone of blank, M-PCL, and M-PCL/TG-BG groups were harvested and assessed. Micro-computed tomography, histological, biochemical, and biomechanical analyses, gene expression, and bone matrix formation were used to assess bone regeneration. The micro-computed tomography results showed that the M-PCL/TG-BG scaffolds not only induced bone tissue formation within the bone defect but also increased BMD and BV/TV compared to blank and M-PCL groups. According to the histological analysis, there was no evidence of bony union in the calvarial defect regions of blank groups, while in M-PCL/TG-BG groups bony integration and repair were observed. The M-PCL/TG-BG scaffolds promoted the Runx2 and collagen type I expression as compared with blank and M-PCL groups. Besides, the bone regeneration in M-PCL/TG-BG groups correlated with TG-BG incorporation. Moreover, the use of M-PCL/TG-BG scaffolds promoted the biomechanical properties in the bone remodeling process. These data demonstrated that the M-PCL/TG-BG scaffolds serve as a highly promising platform for the development of bone grafts, supporting bone regeneration with bone matrix formation, and osteogenic features. Our results exhibited that the 3D-printed M-PCL/TG-BG scaffolds are a promising strategy for successful bone regeneration.

Dual cross-linked COL1/HAp bionic gradient scaffolds containing human amniotic mesenchymal stem cells promote rotator cuff tendon-bone interface healing

The tendon-bone interface heals through scar tissue, while the lack of a natural interface gradient structure and collagen fibre alignment leads to the occurrence of retearing. Therefore, the promotion of tendon healing has become the focus of regenerative medicine. The purpose of this study was to develop a gradient COL1/ hydroxyapatite (HAp) biomaterial loaded with human amniotic mesenchymal stem cells (hAMSCs). The performance of common cross-linking agents, Genipin, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS), and dual cross-linked materials were compared to select the best cross-linking mechanism to optimize the biological and mechanical properties of the scaffold. The optimal COL1/HAp-loaded with hAMSCs were implanted into the tendon-bone rotator cuff interfaces in rats and the effect on the tendon-bone healing was assessed by micro-CT, histological analysis, and biomechanical properties. The results showed that Genipin and EDC/NHS dual cross-linked COL1/HAp had good biological activity and mechanical properties and promoted the proliferation and differentiation of hAMSCs. Animal experiments showed that the group using a scaffold loaded with hAMSCs had excellent continuity and orientation of collagen fibers, increased fibrocartilage and bone formation, and significantly higher biomechanical functions than the control group at the interface at 12 weeks post operation. This study demonstrated that dual cross-linked gradient COL1/HAp-loaded hAMSCs could promote interface healing, thereby providing a feasible strategy for tendon-bone interface regeneration.

Towards optimized tissue regeneration: a new 3D printable bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate

Introduction

Autologous platelet concentrate (APC) are pro-angiogenic and can promote wound healing and tissue repair, also in combination with other biomaterials. However, challenging defect situations remain demanding. 3D bioprinting of an APC based bioink encapsulated in a hydrogel could overcome this limitation with enhanced physio-mechanical interface, growth factor retention/secretion and defect-personalized shape to ultimately enhance regeneration.

Methods

This study used extrusion-based bioprinting to create a novel bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate. Chemico-physical testing exhibited an amorphous structure characterized by high shape fidelity. Cytotoxicity assay and incubation of human osteogenic sarcoma cells (SaOs2) exposed excellent biocompatibility. enzyme-linked immunosorbent assay analysis confirmed pro-angiogenic growth factor release of the printed constructs, and co-incubation with HUVECS displayed proper cell viability and proliferation. Chorioallantoic membrane (CAM) assay explored the pro-angiogenic potential of the prints in vivo. Detailed proteome and secretome analysis revealed a substantial amount and homologous presence of pro-angiogenic proteins in the 3D construct.

Results

This study demonstrated a 3D bioprinting approach to fabricate a novel bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate with high shape fidelity, biocompatibility, and substantial pro-angiogenic properties.

Conclusion

This approach may be suitable for challenging physiological and anatomical defect situations when translated into clinical use.

Development of bioactive short fiber-reinforced printable hydrogels with tunable mechanical and osteogenic properties for bone repair

Personalized bone-regenerative materials have attracted substantial interest in recent years. Modern clinical settings demand the use of engineered materials incorporating patient-derived cells, cytokines, antibodies, and biomarkers to enhance the process of regeneration. In this work, we formulated short microfiber-reinforced hydrogels with platelet-rich fibrin (PRF) to engineer implantable multi-material core-shell bone grafts. By employing 3D bioprinting technology, we fabricated a core-shell bone graft from a hybrid composite hydroxyapatite-coated poly(lactic acid) (PLA) fiber-reinforced methacryolyl gelatin (GelMA)/alginate hydrogel. The overall concept involves 3D bioprinting of long bone mimic microstructures that resemble a core-shell cancellous-cortical structure, with a stiffer shell and a softer core with our engineered biomaterial. We observed a significantly enhanced stiffness in the hydrogel scaffold incorporated with hydroxyapatite (HA)-coated PLA microfibers compared to the pristine hydrogel construct. Furthermore, HA non-coated PLA microfibers were mixed with PRF and GelMA/alginate hydrogel to introduce a slow release of growth factors which can further enhance cell maturation and differentiation. These patient-specific bone grafts deliver cytokines and growth factors with distinct spatiotemporal release profiles to enhance tissue regeneration. The biocompatible and bio-responsive bone mimetic core-shell multi-material structures enhance osteogenesis and can be customized to have materials at a specific location, geometry, and material combination.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor β, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

Combination effect of Chinese kidney-tonifying granules and platelet-rich plasma gels on enhancing bone healing in rat models with femur defects

BACKGROUND

The traditional Chinese kidney-tonifying granules, known as Bushen Zhongyao Keli (BSZYKL), have been found to stimulate calcium salt deposition, enhance bone formation, and foster bone growth within the bone matrix at sites of bone defects. On the other hand, platelet-rich plasma (PRP) is enriched with various growth factors capable of facilitating the repair of bone defects and enhancing bone strength following fractures. This study is dedicated to investigating the combined efficacy of BSZYKL and PRP gel (PRP-G) in the treatment of bone defects.

METHODS

We established a femur defect model in male Sprague-Dawley (SD) rats and filled the defect areas with autologous coccygeal bone and PRP-G. For 8 consecutive weeks, those rats were given with intragastric administration of BSZYKL. Biomechanical characteristics of the femur were assessed 28 days after intramuscular administration. On day 56, bone formation was examined using X-ray, micro-CT, and transmission electron microscopy. Additionally, we analyzed the expression of bone formation markers, Runx2 and Osterix, in femur tissues through qPCR, Western blotting, and immunohistochemistry.

RESULTS

Rats receiving the combined treatment of BSZYKL and PRP-G exhibited drastically enhanced femoral peak torsion, failure angle, energy absorption capacity, and torsional stiffness as compared to control group. This combination therapy also led to marked improvements in bone volume, mass, and microarchitecture, accompanied by elevated expressions of Runx2 and Osterix when compared to control group. Notably, the synergistic effects of BSZYKL and PRP-G in treating bone defects surpassed the effects of either treatment alone.

CONCLUSIONS

These findings revealed the potential of BSZYKL in combination with PRP-G in improving bone defects.

Osseointegration enhancement by controlling dispersion state of carbonate apatite in polylactic acid implant

Osteoconductive ceramics (OCs) are often used to endow polylactic acid (PLA) with osseointegration ability. Conventionally, OC powder is dispersed in PLA. However, considering cell attachment to the implant, OCs may be more favorable when they exist in the form of aggregations, such as granules, and are larger than the cells rather than being dispersed like a powder. In this study, to clarify the effects of the dispersion state of OCs on the osseointegration ability, carbonate apatite (CAp), a bone mineral analog that is osteoconductive and bioresorbable, powder-PLA (P-PLA), and CAp granule-PLA (G-PLA) composite implants were fabricated via thermal pressing. The powder and granule sizes of CAp were approximately 1 and 300-600 µm, respectively. G-PLA exhibited a higher water wettability and released calcium and phosphate ions faster than P-PLA. When cylindrical G-PLA, P-PLA, and PLA were implanted in rabbit tibial bone defects, G-PLA promoted bone maturation compared to P-PLA and pure PLA. Furthermore, G-PLA bonded directly to the host bone, whereas P-PLA bonded across the osteoid layers. Consequently, the bone-to-implant contact of G-PLA was 1.8- and 5.6-fold higher than those of P-PLA and PLA, respectively. Furthermore, the adhesive shear strength of G-PLA was 1.9- and 3.0-fold higher than those of P-PLA and PLA, respectively. Thus, G-PLA achieved earlier and stronger osseointegration than P-PLA or PLA. The findings of this study highlight the significance of the state of dispersion of OCs in implants as a novel strategy for material development.

The Influence of Extracellular Vesicles Secreted by Dural Cells on Osteoblasts

To explore the influence of extracellular vesicles secreted by dural cells (Dura-EVs) on osteoblasts. Our methodology involves assessing the effects of these EVs at concentrations of 50ug/ml, 100ug/ml, and 200ug/ml on osteoblasts proliferation, differentiation, migration, osteogenesis, and inhibition of apoptosis. We also treated a cranial defect model with injections of these Dura-EVs and monitored the healing rate of cranial defects. Tissue sections were analyzed using Hematoxylin and Eosin (H & E), Masson's trichrome, and immunofluorescence (IF) staining. Our results suggest that Dura-EVs can enhance osteoblasts proliferation, migration, differentiation, and osteogenesis in a dose-dependent manner in vitro. In vivo, Dura-EVs may promote the repair of skull defects. Dura-EVs have an important influence on osteoblasts, our findings shed light on a novel aspect of the dura mater's contribution to cranial osteogenesis.

Enhancing bone tissue engineering with 3D-Printed polycaprolactone scaffolds integrated with tragacanth gum/bioactive glass

Tissue-engineered bone substitutes, characterized by favorable physicochemical, mechanical, and biological properties, present a promising alternative for addressing bone defects. In this study, we employed an innovative 3D host-guest scaffold model, where the host component served as a mechanical support, while the guest component facilitated osteogenic effects. More specifically, we fabricated a triangular porous polycaprolactone framework (host) using advanced 3D printing techniques, and subsequently filled the framework's pores with tragacanth gum-45S5 bioactive glass as the guest component. Comprehensive assessments were conducted to evaluate the physical, mechanical, and biological properties of the designed scaffolds. Remarkably, successful integration of the guest component within the framework was achieved, resulting in enhanced bioactivity and increased strength. Our findings demonstrated that the scaffolds exhibited ion release (Si, Ca, and P), surface apatite formation, and biodegradation. Additionally, in vitro cell culture assays revealed that the scaffolds demonstrated significant improvements in cell viability, proliferation, and attachment. Significantly, the multi-compartment scaffolds exhibited remarkable osteogenic properties, indicated by a substantial increase in the expression of osteopontin, osteocalcin, and matrix deposition. Based on our results, the framework provided robust mechanical support during the new bone formation process, while the guest component matrix created a conducive micro-environment for cellular adhesion, osteogenic functionality, and matrix production. These multi-compartment scaffolds hold great potential as a viable alternative to autografts and offer promising clinical applications for bone defect repair in the future.