Synergistic Effects of Beta Tri‐Calcium Phosphate and Porcine‐Derived Decellularized Bone Extracellular Matrix in 3D‐Printed Polycaprolactone Scaffold on Bone Regeneration

Bone‐derived extracellular matrix (ECM) is widely used in studies on bone regeneration because of its ability to provide a microenvironment of native bone tissue. However, a hydrogel, which is a main type of ECM application, is limited to use for bone graft substitutes due to relative lack of mechanical properties. The present study aims to fabricate a scaffold for guiding effective bone regeneration. A polycaprolactone (PCL)/beta‐tricalcium phosphate (β‐TCP)/bone decellularized extracellular matrix (dECM) scaffold capable of providing physical and physiological environment are fabricated using 3D printing technology and decoration method. PCL/β‐TCP/bone dECM scaffolds exhibit excellent cell seeding efficiency, proliferation, and early and late osteogenic differentiation capacity in vitro. In addition, outstanding results of bone regeneration are observed in PCL/β‐TCP/bone dECM scaffold group in the rabbit calvarial defect model in vivo. These results indicate that PCL/β‐TCP/bone dECM scaffolds have an outstanding potential as bone graft substitutes for effective bone regeneration.     

3D and Porous RGDC‐Functionalized Polyester‐Based Scaffolds as a Niche to Induce Osteogenic Differentiation of Human Bone Marrow Stem Cells

Polyester‐based scaffolds covalently functionalized with arginine‐glycine‐aspartic acid‐cysteine (RGDC) peptide sequences support the proliferation and osteogenic differentiation of stem cells. The aim is to create an optimized 3D niche to sustain human bone marrow stem cell (hBMSC) viability and osteogenic commitment, without reliance on differentiation media. Scaffolds consisting of poly(lactide‐co‐trimethylene carbonate), poly(LA‐co‐TMC), and functionalized poly(lactide) copolymers with pendant thiol groups are prepared by salt‐leaching technique. The availability of functional groups on scaffold surfaces allows for an easy and straightforward method to covalently attach RGDC peptide motifs without affecting the polymerization degree. The strategy enables the chemical binding of bioactive motifs on the surfaces of 3D scaffolds and avoids conventional methods that require harsh conditions. Gene and protein levels and mineral deposition indicate the osteogenic commitment of hBMSC cultured on the RGDC functionalized surfaces. The osteogenic commitment of hBMSC is enhanced on functionalized surfaces compared with nonfunctionalized surfaces and without supplementing media with osteogenic factors. Poly(LA‐co‐TMC) scaffolds have potential as scaffolds for osteoblast culture and bone grafts. Furthermore, these results contribute to the development of biomimetic materials and allow a deeper comprehension of the importance of RGD peptides on stem cell transition toward osteoblastic lineage.     

Mass‐producible Nano‐featured Polystyrene Surfaces for Regulating the Differentiation of Human Adipose‐derived Stem Cells

In this study, we report an efficient and cost‐effective method of fabricating polystyrene (PS) nano‐featured substrates containing nanopore (NPo) and nanopillar (NPi) arrays based on hot embossing using nickel nano‐stamps. We investigate the behavior of adipose‐derived stem cells (ASCs), including adhesion, morphology, proliferation and differentiation, on the replicated PS surfaces. Compared to a flat substrate, NPo‐ and NPi‐featured substrates do not alter the morphology of stem cells. However, both NPo‐ and NPi‐featured substrates induce different integrin expression and lower formation of focal adhesion complexes. In addition, ASCs on the NPo‐featured substrate exhibit greater adipogenic differentiation, while the NPi‐featured substrate induces higher osteogenic differentiation.

     

Controlling the Poly(ε‐caprolactone) Degradation to Maintain the Stemness and Function of Adipose‐Derived Mesenchymal Stem Cells in Vascular Regeneration Application

Biodegradable poly(ε‐caprolactone) (PCL) scaffolds with adipose‐derived mesenchymal stem cells (ADSCs) have been used in vascular regeneration studies. An evaluation method of the effect of PCL degradation products (DP) on the viability, stemness, and differentiation capacities of ADSCs is established. ADSCs are cultured in medium containing different concentrations of PCL DP before evaluating the effect of PCL DP on the cell apoptosis and proliferation, cell surface antigens, adipogenic and osteogenic differentiation capacities, and capacities to differentiate into endothelial cells and smooth muscle cells. The results demonstrate that PCL DP exceed 0.05 mg mL^?1 may change the stemness and differentiation capacities of ADSCs. Therefore, to control the proper concentration of PCL DP is essential for ADSCs in vascular regeneration application.     

Mineralized Synthetic Matrices as an Instructive Microenvironment for Osteogenic Differentiation of Human Mesenchymal Stem Cells

The effect of substrate‐mediated signals on osteogenic differentiation of hMSCs is studied using a synthetic bone‐like material comprising both organic and inorganic components that supports adhesion, spreading, and proliferation of hMSCs. hMSCs undergo osteogenic differentiation even in the absence of osteogenesis‐inducing supplements. They exhibit higher expressions of Runx2, BSP, and OCN compared to their matrix‐rigidity‐matched, non‐mineralized hydrogel counterparts. The mineralized‐hydrogel‐assisted osteogenic differentiation of hMSCs could be attributed to their exposure to high local concentrations of calcium and phosphate ions in conjunction with chemical and topological cues arising from the hydrogel‐bound calcium phosphate mineral layer.

     

An Injectable,Bifunctional Hydrogel with Photothermal Effects for Tumor Therapy and Bone Regeneration

Significant attention has been focused on bone tumor therapy recently. At present, the treatment in clinic typically requires surgical intervention. However, a few tumor cells remain around bone defects after surgery and subsequently proliferate within several days. Thus, fabrication of biomaterials with dual functions of tumor therapy and bone regeneration is significant. Herein, the injectable hydrogel containing cisplatin (DDP) and polydopamine‐decorated nano‐hydroxyapatite is prepared via Schiff base reaction between the aldehyde groups on oxidized sodium alginate and amino groups on chitosan. The hydrogel exhibits sustained release properties for DDP due to the immobilization of DDP via abundant functional groups on polydopamine (PDA). Additionally, given the intense absorption of PDA in the near‐infrared region, the hydrogel exhibits excellent photothermal effects when exposed to the NIR laser (808 nm). Based on the properties, the hydrogel effectively ablates tumor cells (4T1 cells) in vitro and suppresses tumor growth in vivo. Furthermore, the hydrogel promotes the adhesion and proliferation of bone mesenchymal stem cells in vitro due to the abundant functional groups on PDA and further induces bone regeneration in vivo. Therefore, the study extends research on novel biomaterials with dual functions of tumor therapy and bone regeneration.     

Micro‐Nanostructures of Cellulose‐Collagen for Critical Sized Bone Defect Healing

Bone tissue engineering strategies utilize biodegradable polymeric matrices alone or in combination with cells and factors to provide mechanical support to bone, while promoting cell proliferation, differentiation, and tissue ingrowth. The performance of mechanically competent, micro‐nanostructured polymeric matrices, in combination with bone marrow stromal cells (BMSCs), is evaluated in a critical sized bone defect. Cellulose acetate (CA) is used to fabricate a porous microstructured matrix. Type I collagen is then allowed to self‐assemble on these microstructures to create a natural polymer‐based, micro‐nanostructured matrix (CAc). Poly (lactic‐co‐glycolic acid) matrices with identical microstructures serve as controls. Significantly higher number of implanted host cells are distributed in the natural polymer based micro‐nanostructures with greater bone density and more uniform cell distribution. Additionally, a twofold increase in collagen content is observed with natural polymer based scaffolds. This study establishes the benefits of natural polymer derived micro‐nanostructures in combination with donor derived BMSCs to repair and regenerate critical sized bone defects. Natural polymer based materials with mechanically competent micro‐nanostructures may serve as an alternative material platform for bone regeneration.     

球形羟基磷灰石纳米颗粒的可控合成及其对间充质干细胞生长分化的影响

本文采用CTAB为添加剂进行球形纳米相羟基磷灰石(nHAP)的可控合成，并采用透射电子显微镜(TEM)、X-射线衍射仪(XRD)、傅立叶变换红外光谱仪(FTIR)和精密接触角测量仪对所制得的纳米颗粒的物性进行了表征。结果表明所制得的纳米颗粒为部分结晶的羟基磷灰石，颗粒为均匀球形，粒径约为20 nm，具有很好的亲水性。由该纳米颗粒构成的生长基质有利于骨髓间充质干细胞的贴壁、增殖以及成骨分化，是一种良好的骨组织工程支架材料。     

In Vivo Osteogenic Differentiation of Human Dental Pulp Stem Cells Embedded in an Injectable In Vivo‐Forming Hydrogel

In this study, human dental pulp stem cells (hDPSCs) are examined as a cellular source for bone tissue engineering using an in vivo‐forming hydrogel. The hDPSCs are easily harvested in large quantities from extracted teeth. The stemness of harvested hDPSCs indicates their relative tolerance to ex vivo manipulation in culture. The in vitro osteogenic differentiation of hDPSCs is characterized using Alizarin Red S (ARS), von Kossa (VK), and alkaline phosphatase (ALP) staining. The solution of hDPSCs and a methoxy polyethylene glycol‐polycaprolactone block copolymer (PC) is easily prepared by simple mixing at room temperature and in no more than 10 s it forms in vivo hydrogels after subcutaneous injection into rats. In vivo osteogenic differentiation of hDPSCs in the in vivo‐forming hydrogel is confirmed by micro‐computed tomography (CT), histological staining, and gene expression. Micro‐CT analysis shows evidence of significant tissue‐engineered bone formation in hDPSCs‐loaded hydrogel in the presence of osteogenic factors. Differentiated osteoblasts in in vivo‐forming hydrogel are identified by ARS and VK staining and are found to exhibit characteristic expression of genes like osteonectin, osteopontin, and osteocalcin. In conclusion, hDPSCs embedded in an in vivo‐forming hydrogel may provide benefits as a noninvasive formulation for bone tissue engineering applications.

     

Nano‐Bio Engineered Carbon Dot‐Peptide Functionalized Water Dispersible Hyperbranched Polyurethane for Bone Tissue Regeneration

The present study delves into a combined bio‐nano‐macromolecular approach for bone tissue engineering. This approach relies on the properties of an ideal scaffold material imbued with all the chemical premises required for fostering cellular growth and differentiation. A tannic acid based water dispersible hyperbranched polyurethane is fabricated with bio‐nanohybrids of carbon dot and four different peptides (viz. SVVYGLR, PRGDSGYRGDS, IPP, and CGGKVGKACCVPTKLSPISVLYK) to impart target specific in vivo bone healing ability. This polymeric bio‐nanocomposite is blended with 10 wt% of gelatin and examined as a non‐invasive delivery vehicle. In vitro assessment of the developed polymeric system reveals good osteoblast adhesion, proliferation, and differentiation. Aided by this panel of peptides, the polymeric bio‐nanocomposite exhibits in vivo ectopic bone formation ability. The study on in vivo mineralization and vascularization reveals the occurrence of calcification and blood vessel formation. Thus, the study demonstrates carbon dot/peptide functionalized hyperbranched polyurethane gel for bone tissue engineering application.

     

Functional PLGA Scaffolds for Chondrogenesis of Bone‐Marrow‐Derived Mesenchymal Stem Cells

Two chondrogenic factors, Dex and TGF‐β1, were incorporated into PLGA scaffolds and their chondrogenic potential was evaluated. The Dex‐loaded PLGA scaffold was grafted with AA and heparin, the heparin‐immobilized one was then reacted with TGF‐β1, yielding a PLGA/Dex‐TGF (PLGA/D/T) scaffold. The scaffolds were seeded with rabbit MSCs and cultured for 4 weeks. The results show that the scaffolds including chondrogenic factors strongly upregulated the expression of cartilage‐specific genes and clearly displayed type‐II collagen immunofluorescence. The functionalized PLGA scaffolds could provide an appropriate niche for chondrogenic differentiation of MSC without a constant medium supply of Dex and TGF‐β1.

     

Poly(l‐Lactic Acid)/Gelatin Fibrous Scaffold Loaded with Simvastatin/Beta‐Cyclodextrin‐Modified Hydroxyapatite Inclusion Complex for Bone Tissue Regeneration

Recently, the application of nanostructured materials in the field of tissue engineering has garnered attention to mediate treatment and regeneration of bone defects. In this study, poly(l ‐lactic acid) (PLLA)/gelatin (PG) fibrous scaffolds are fabricated and β‐cyclodextrin (βCD) grafted nano‐hydroxyapatite (HAp) is coated onto the fibrous scaffold surface via an interaction between βCD and adamantane. Simvastatin (SIM), which is known to promote osteoblast viability and differentiation, is loaded into the remaining βCD. The specimen morphologies are characterized by scanning electron microscopy. The release profile of SIM from the drug loaded scaffold is also evaluated. In vitro proliferation and osteogenic differentiation of human adipose derived stem cells on SIM/HAp coated PG composite scaffolds is characterized by alkaline phosphatase (ALP) activity, mineralization (Alizarin Red S staining), and real time Polymerase chain reaction (PCR). The scaffolds are then implanted into rabbit calvarial defects and analyzed by microcomputed tomography for bone formation after four and eight weeks. These results demonstrate that SIM loaded PLLA/gelatin/HAp‐(βCD) scaffolds promote significantly higher ALP activity, mineralization, osteogenic gene expression, and bone regeneration than control scaffolds. This suggests the potential application of this material toward bone tissue engineering.

     

Physically Crosslinked Nanocomposites from Silicate‐Crosslinked PEO: Mechanical Properties and Osteogenic Differentiation of Human Mesenchymal Stem Cells

The mechanical and biological properties of silicate‐crosslinked PEO nanocomposites are studied. A strong correlation is observed between silicate concentration and mechanical properties. In vitro cell culture studies reveal that an increase in silicate concentration enhances the attachment and proliferation of human mesenchymal stem cells significantly. An upregulation in the expression of osteocalcin on nanocomposites compared to the tissue culture polystyrene control is observed. Together, these results suggest that silicate‐based nanocomposites are bioactive and have the potential to be used in a range of biotechnological and biomedical applications such as injectable matrices, biomedical coatings, drug delivery, and regenerative medicine.