Design, construction and mechanical testing of digital 3D anatomical data-based PCL-HA bone tissue engineering scaffold.

The study aims to investigate the techniques of design and construction of CT 3D reconstructional data-based polycaprolactone (PCL)-hydroxyapatite (HA) scaffold. Femoral and lumbar spinal specimens of eight male New Zealand white rabbits were performed CT and laser scanning data-based 3D printing scaffold processing using PCL-HA powder. Each group was performed eight scaffolds. The CAD-based 3D printed porous cylindrical stents were 16 piece × 3 groups, including the orthogonal scaffold, the Pozi-hole scaffold and the triangular hole scaffold. The gross forms, fiber scaffold diameters and porosities of the scaffolds were measured, and the mechanical testing was performed towards eight pieces of the three kinds of cylindrical scaffolds, respectively. The loading force, deformation, maximum-affordable pressure and deformation value were recorded. The pore-connection rate of each scaffold was 100 % within each group, there was no significant difference in the gross parameters and micro-structural parameters of each scaffold when compared with the design values (P > 0.05). There was no significant difference in the loading force, deformation and deformation value under the maximum-affordable pressure of the three different cylinder scaffolds when the load was above 320 N. The combination of CT and CAD reverse technology could accomplish the design and manufacturing of complex bone tissue engineering scaffolds, with no significant difference in the impacts of the microstructures towards the physical properties of different porous scaffolds under large load.

Melt Electrowriting Combined with Fused Deposition Modeling Printing for the Fabrication of Three-Dimensional Biomimetic Scaffolds for Osteotendinous Junction Regeneration.

Purpose: This study aims to explore a novel scaffold for osteotendinous junction regeneration and to preliminarily verify its osteogenic and tenogenic abilities in vitro. Methods: A polycaprolactone (PCL) scaffold with aligned and orthogonal fibers was created using melt electrowriting (MEW) and fused deposition modeling (FDM). The scaffold was coated with Type I collagen, and hydroxyapatite was carefully added to separate the regions intended for bone and tendon regeneration, before being rolled into a cylindrical shape. Human adipose-derived stem cells (hADSCs) were seeded to evaluate viability and differentiation. Scaffold characterization was performed with Scanning Electron Microscope (SEM). Osteogenesis was assessed by alkaline phosphatase (ALP) and Alizarin red staining, while immunostaining and transcription-quantitative polymerase chain reaction (RT-qPCR) evaluated osteogenic and tendogenic markers. Results: Scaffolds were developed in four variations: aligned (A), collagen-coated aligned (A+C), orthogonal (O), and mineral-coated orthogonal (O+M). SEM analysis confirmed surface morphology and energy-dispersive X-ray spectroscopy (EDS) verified mineral coating on O+M types. Hydrophilicity and mechanical properties were optimized in modified scaffolds, with A+C showing increased tensile strength and O+M improved in compression. hADSCs demonstrated good viability and morphology across scaffolds, withO+M scaffolds showing higher cell proliferation and osteogenic potential, and A and A+C scaffolds supporting tenogenic differentiation. Conclusion: This study confirms the potential of a novel PCL scaffold with distinct regions for osteogenic and tenogenic differentiation, supporting the regeneration of osteotendinous junctions in vitro.

Surface-Modified Nano-Hydroxyapatite Uniformly Dispersed on High-Porous GelMA Scaffold Surfaces for Enhanced Osteochondral Regeneration.

Purpose: This study aims to investigate the impact of enhancing subchondral bone repair on the efficacy of articular cartilage restoration, thereby achieving improved osteochondral regeneration outcomes. Methods: In this study, we modified the surface of nano-hydroxyapatite (n-HAp) through alkylation reactions to prepare n-HApMA. Characterization techniques, including X-ray diffraction, infrared spectroscopy scanning, thermogravimetric analysis, particle size analysis, and electron microscopy, were employed to analyze n-HApMA. Bioinks were prepared using n-HApMA, high porosity GelMA hydrogel, and adipose tissue derived stromal cells (ADSCs). The rheological properties of the bioinks during photocuring were investigated using a rheometer. Based on these bioinks, a biphasic scaffold was constructed. The viability of cells within the scaffold was observed using live-dead cell staining, while the internal morphology was examined using scanning electron microscopy. The stiffness of the scaffold was evaluated through compression testing. Scaffolds were implanted into the osteochondral defects of New Zealand rabbit knees, and microCT was utilized to observe the subchondral bone repair. Hematoxylin and eosin (H&E) staining, Masson's trichrome staining, and Safranin O/Fast Green staining were performed to assess the regeneration of subchondral bone and cartilage. Furthermore, immunohistochemical staining was employed to detect the expression of osteogenic and chondrogenic-related molecules. Results: Scaffold characterization revealed that surface modification enables the uniform distribution of n-HApMA within the GelMA matrix. The incorporation of 5% n-HApMA notably enhanced the elastic modulus and stiffness of the 6% high-porosity GelMA in comparison to n-HAp. Moreover, in-vivo study showed that the homogeneous dispersion of n-HApMA on the GelMA matrix facilitated the osteogenic differentiation of adipose-derived stem cells (ADSCs) and promoted osteochondral tissue regeneration. Conclusion: These findings suggest potential applications of the n-HApMA/GelMA composite in the field of tissue engineering and regenerative medicine.

Hierarchical assembly of dual-responsive biomineralized polydopamine-calcium phosphate nanocomposites for enhancing chemo-photothermal therapy by autophagy inhibition.

The induction of autophagy in cancer cells would occur in response to several therapy strategies, including chemotherapy and photothermal therapy (PTT). Hence, combined autophagy inhibition has been regarded as a prevailing strategy to enhance treatment sensitivity in cancers. Herein, dual pH/thermal responsive biomineralized nanocomposites (PCNPs) were rationally designed and prepared based on the hierarchical assembly of calcium phosphate (CaP) and polydopamine (PDA). The first step in the self-assembly process involves the incorporation of hydrophobic chemotherapeutic docetaxel (DTX) into the CaP nanoparticles. Next, PDA was utilized as the coating to hierarchically self-assemble onto the surface of CaP through a simple self-polymerization of dopamine. Third, the autophagy inhibitor chloroquine (CQ) was absorbed onto the surface of PDA via non-covalent interactions, forming PCNPs/DC. CQ was the only FDA approved autophagy inhibitor in clinical trials that could inhibit autophagosome fusion and degradation. The resulting PCNPs/DC could exhibit dual pH/thermal responsive properties due to the acid-sensitive CaP core and the photothermal effect of the PDA coating. Effective inhibition of autophagy in cancer cells could be realized by blocking the lysosome and weakening the degradation of autolysosomes by PCNPs/DC. Interestingly, complementary autophagy inhibition could therefore sensitize the effects of chemo-photothermal therapy both in vitro and in vivo with negligible toxicity. Therefore, these hierarchically assembled biomineralized nanocomposites would be used as a prevailing strategy to sensitize chemo-photothermal therapy by complementary autophagy inhibition.

Combined antibacterial and osteogenic in situ effects of a bifunctional titanium alloy with nanoscale hydroxyapatite coating.

To resolve the problems of bacterial infections and the low efficiency of osteogenesis of implanted titanium alloys in clinical dental and bone therapy, we developed a bifunctional titanium alloy (Ti) with a nano-hydroxyapatite (HA) coating (HBD + BMP/HA-Ti), which enables the sustained release of the natural antimicrobial peptide human ß-defensin 3 (HBD-3) and bone morphogenetic protein-2 (BMP-2). Due to the poriferous nano-sized structure of the HA coating with a 20-30 µm thickness, the HBD + BMP/HA-Ti material had a high encapsulation efficiency (>74%) and exhibited synchronized slow release of HBD-3 and BMP-2. In an antibacterial test, HBD + BMP/HA-Ti prevented the growth of bacteria in an inoculated medium, and its surface remained free from viable bacteria after a continuous incubation with Gram-negative and Gram-positive strains for 7 days. Furthermore, good adhesion, proliferation and osteogenic differentiation of hBMSCs in contact with HBD + BMP/HA-Ti were achieved in 7 days. Therefore, the bifunctional titanium alloy HBD + BMP/HA-Ti has a great potential for eventual applications in the protection of implants against bacteria in the orthopaedic and dental clinic.