Yaohua He

Enhanced osteogenesis and angiogenesis by mesoporous hydroxyapatite microspheres-derived simvastatin sustained release system for superior bone regeneration

Biomaterials with both excellent osteogenic and angiogenic activities are desirable to repair massive bone defects. In this study, simvastatin with both osteogenic and angiogenic activities was incorporated into the mesoporous hydroxyapatite microspheres (MHMs) synthesized through a microwave-assisted hydrothermal method using fructose 1,6-bisphosphate trisodium salt (FBP) as an organic phosphorous source. The effects of the simvastatin-loaded MHMs (S-MHMs) on the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) and angiogenesis in EA.hy926 cells were investigated. The results showed that the S-MHMs not only enhanced the expression of osteogenic markers in rBMSCs but also promoted the migration and tube formation of EA.hy926 cells. Furthermore, the S-MHMs were incorporated into collagen matrix to construct a novel S-MHMs/collagen composite scaffold. With the aid of MHMs, the water-insoluble simvastatin was homogenously incorporated into the hydrophilic collagen matrix and presented a sustained release profile. In vivo experiments showed that the S-MHMs/collagen scaffolds enhanced the bone regeneration and neovascularization simultaneously. These results demonstrated that the water-insoluble simvastatin could be incorporated into the MHMs and maintained its biological activities, more importantly, the S-MHMs/collagen scaffolds fabricated in this study are of immense potential in bone defect repair by enhancing osteogenesis and angiogenesis simultaneously.

Strontium-Doped Amorphous Calcium Phosphate Porous Microspheres Synthesized through a Microwave-Hydrothermal Method Using Fructose 1,6-Bisphosphate as an Organic Phosphorus Source: Application in Drug Delivery and Enhanced Bone Regeneration.

Nanostructured calcium phosphate porous microspheres are of great potential in drug delivery and bone regeneration due to their large specific surface area, biocompatibility, and similarity to inorganic component of osseous tissue. In this work, strontium (Sr)-doped amorphous calcium phosphate porous microspheres (SrAPMs) were synthesized through a microwave-hydrothermal method using fructose 1,6-bisphosphate trisodium salt as the source of phosphate ions. The SrAPMs showed a mesoporous structure and a relatively high specific area. Compared with the hydroxyapatite nanorods prepared by using Na2HPO4·12H2O as the phosphorus source, the SrAPMs with a higher specific surface area were more effective in drug loading using vancomycin as the antiobiotics of choice and consequently having a higher antibacterial efficiency both on agar plates and in broths. Furthermore, to assess the potential application of SrAPMs in bone defect repair, a novel biomimetic bone tissue-engineering scaffold consisting of collagen (Coll) and SrAPMs was constructed using a freeze-drying fabrication process. Incorporation of the SrAPMs not only improved the mechanical properties, but also enhanced the osteogenesis of rat bone marrow mesenchymal stem cells. The in vivo experiments demonstrated that the SrAPMs/Coll scaffolds remarkably enhanced new bone formation compared with the Coll and APMs/Coll scaffolds in a rat critical-sized calvarial defect model at 8 weeks postimplantation. In summary, SrAPMs developed in this work are promising as antibiotic carriers and may encourage bone formation when combined with collagen.

In vitro and in vivo evaluation of MgF2 coated AZ31 magnesium alloy porous scaffolds for bone regeneration

Porous magnesium scaffolds are attracting increasing attention because of their degradability and good mechanical property. In this work, a porous and degradable AZ31 magnesium alloy scaffold was fabricated using laser perforation technique. To enhance the corrosion resistance and cytocompatibility of the AZ31 scaffolds, a fluoride treatment was used to acquire the MgF2 coating. Enhanced corrosion resistance was confirmed by immersion and electrochemical tests. Due to the protection provided by the MgF2 coating, the magnesium release and pH increase resulting from the degradation of the FAZ31 scaffolds were controllable. Moreover, in vitro studies revealed that the MgF2 coated AZ31 (FAZ31) scaffolds enhanced the proliferation and attachment of rat bone marrow stromal cells (rBMSCs) compared with the AZ31 scaffolds. In addition, our present data indicated that the extract of the FAZ31 scaffold could enhance the osteogenic differentiation of rBMSCs. To compare the in vivo bone regenerative capacity of the AZ31 and FAZ31 scaffolds, a rabbit femoral condyle defect model was used. Micro-computed tomography (micro-CT) and histological examination were performed to evaluate the degradation of the scaffolds and bone volume changes. In addition to the enhanced the corrosion resistance, the FAZ31 scaffolds were more biocompatible and induced significantly more new bone formation in vivo. Conversely, bone resorption was observed from the AZ31 scaffolds. These promising results suggest potential clinical applications of the fluoride pretreated AZ31 scaffold for bone tissue repair and regeneration.

Evaluation of zinc-doped mesoporous hydroxyapatite microspheres for the construction of a novel biomimetic scaffold optimized for bone augmentation

Biomaterials with high osteogenic activity are desirable for sufficient healing of bone defects resulting from trauma, tumor, infection, and congenital abnormalities. Synthetic materials mimicking the structure and composition of human trabecular bone are of considerable potential in bone augmentation. In the present study, a zinc (Zn)-doped mesoporous hydroxyapatite microspheres (Zn-MHMs)/collagen scaffold (Zn-MHMs/Coll) was developed through a lyophilization fabrication process and designed to mimic the trabecular bone. The Zn-MHMs were synthesized through a microwave-hydrothermal method by using creatine phosphate as an organic phosphorus source. Zn-MHMs that consist of hydroxyapatite nanosheets showed relatively uniform spherical morphology, mesoporous hollow structure, high specific surface area, and homogeneous Zn distribution. They were additionally investigated as a drug nanocarrier, which was efficient in drug delivery and presented a pH-responsive drug release behavior. Furthermore, they were incorporated into the collagen matrix to construct a biomimetic scaffold optimized for bone tissue regeneration. The Zn-MHMs/Coll scaffolds showed an interconnected pore structure in the range of 100–300 μm and a sustained release of Zn ions. More importantly, the Zn-MHMs/Coll scaffolds could enhance the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells. Finally, the bone defect repair results of critical-sized femoral condyle defect rat model demonstrated that the Zn-MHMs/Coll scaffolds could enhance bone regeneration compared with the Coll or MHMs/Coll scaffolds. The results suggest that the biomimetic Zn-MHMs/Coll scaffolds may be of enormous potential in bone repair and regeneration.

Copper-doped mesoporous hydroxyapatite microspheres synthesized by a microwave-hydrothermal method using creatine phosphate as an organic phosphorus source: application in drug delivery and enhanced bone regeneration

The development of multifunctional biomaterials with drug delivery ability, and pro-osteogenic and pro-angiogenic activities has garnered increasing interest in the field of regenerative medicine. In the present study, hypoxia-mimicking copper (Cu)-doped mesoporous hydroxyapatite (HAP) microspheres (Cu-MHMs) were successfully synthesized through a microwave-hydrothermal method by using creatine phosphate as an organic phosphorus source. The Cu-MHMs doped with 0.2, 0.5 and 1 mol% Cu were prepared. The Cu-MHMs consisting of HAP nanorods or nanosheets exhibited a hierarchically mesoporous hollow structure and a high specific surface area. Then the Cu-MHMs were investigated as a drug nanocarrier using doxorubicin hydrochloride (DOX) as a model drug. The Cu-MHMs showed a relatively high drug-loading capacity and a pH-responsive drug release behavior. Furthermore, the Cu-MHMs were incorporated into a chitosan (CS) matrix to construct a biomimetic scaffold optimized for bone regeneration. The Cu-MHM/CS composite scaffolds maintained high degrees of porosity and showed a sustained release of Cu ions. More importantly, the Cu-MHM/CS scaffolds not only enhanced the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) but also promoted the migration and tube formation of EA.hy926 cells. When implanted in rat critical-sized calvarial defects, the Cu-MHM/CS scaffolds significantly enhanced bone regeneration accompanied by more new blood vessel formation at 8 weeks post-operation compared with the MHM/CS scaffolds. These results suggest that the hypoxia-mimicking Cu-MHM/CS scaffolds could encourage bone regeneration by enhancing osteogenesis and angiogenesis simultaneously, which bodes well for the reconstruction of vascularized tissue-engineered bone.

Hydroxyapatite Nanowire@Magnesium Silicate Core–Shell Hierarchical Nanocomposite: Synthesis and Application in Bone Regeneration

Multifunctional biomaterials that simultaneously combine high biocompatibility, biodegradability, and bioactivity are promising for applications in various biomedical fields such as bone defect repair and drug delivery. Herein, the synthesis of hydroxyapatite nanowire@magnesium silicate nanosheets (HANW@MS) core-shell porous hierarchical nanocomposites (nanobrushes) is reported. The morphology of the magnesium silicate (MS) shell can be controlled by simply varying the solvothermal temperature and the amount of Mg2+ ions. Compared with hydroxyapatite nanowires (HANWs), the HANW@MS core-shell porous hierarchical nanobrushes exhibit remarkably increased specific surface area and pore volume, endowing the HANW@MS core-shell porous hierarchical nanobrushes with high-performance drug loading and sustained release. Moreover, the porous scaffold of HANW@MS/chitosan (HANW@MS/CS) is prepared by incorporating the HANW@MS core-shell porous hierarchical nanobrushes into the chitosan (CS) matrix. The HANW@MS/CS porous scaffold not only promotes the attachment and growth of rat bone marrow derived mesenchymal stem cells (rBMSCs), but also induces the expression of osteogenic differentiation related genes and the vascular endothelial growth factor (VEGF) gene of rBMSCs. Furthermore, the HANW@MS/CS porous scaffold can obviously stimulate in vivo bone regeneration, owing to its high bioactive performance on the osteogenic differentiation of rBMSCs and in vivo angiogenesis. Since Ca, Mg, Si, and P elements are essential in human bone tissue, HANW@MS core-shell porous hierarchical nanobrushes with multifunctional properties are expected to be promising for various biomedical applications such as bone defect repair and drug delivery.

Platelet-Rich Plasma-Loaded Poly(d,l-lactide)-Poly(ethylene glycol)-Poly(d,l-lactide) Hydrogel Dressing Promotes Full-Thickness Skin Wound Healing in a Rodent Model

Traditional therapeutic methods for skin wounds have many disadvantages, and new wound dressings that can facilitate the healing process are thus urgently needed. Platelet-rich plasma (PRP) contains multiple growth factors (GFs) and shows a significant capacity to heal soft tissue wounds. However, these GFs have a short half-life and deactivate rapidly; we therefore need a sustained delivery system to overcome this shortcoming. In this study, poly(d,l-lactide)-poly(ethylene glycol)-poly(d,l-lactide) (PDLLA-PEG-PDLLA: PLEL) hydrogel was successfully created as delivery vehicle for PRP GFs and was evaluated systematically. PLEL hydrogel was injectable at room temperature and exhibited a smart thermosensitive in situ gel-formation behavior at body temperature. In vitro cell culture showed PRP-loaded PLEL hydrogel (PRP/PLEL) had little cytotoxicity, and promoted EaHy926 proliferation, migration and tube formation; the factor release assay additionally indicated that PLEL realized the controlled release of PRP GFs for as long as 14 days. When employed to treat rodents’ full-thickness skin defects, PRP/PLEL showed a significantly better ability to raise the number of both newly formed and mature blood vessels compared to the control, PLEL and PRP groups. Furthermore, the PRP/PLEL-treated group displayed faster wound closure, better reepithelialization and collagen formation. Taken together, PRP/PLEL provides a promising strategy for promoting angiogenesis and skin wound healing, which extends the potential of this dressing for clinical application.

Design of a novel wound dressing consisting of alginate hydrogel and simvastatin-incorporated mesoporous hydroxyapatite microspheres for cutaneous wound healing

Wound dressings with pro-angiogenic activity are desirable for the rapid healing of full-thickness cutaneous wounds. It is well accepted that simvastatin can stimulate angiogenesis in addition to its lipid-lowering efficacy. However, the construction of a hydrogel-based wound dressing containing simvastatin remains a challenge due to its water-insolubility. In the present study, a novel wound dressing composed of alginate hydrogel (AH) and simvastatin-incorporated mesoporous hydroxyapatite microspheres (S-MHMs) was constructed for the sustained drug release of simvastatin. We first investigated the effect of simvastatin on the angiogenic differentiation of human umbilical vein endothelial cells (HUVECs). The in vitro results revealed that simvastatin significantly promoted the migration and tube formation of HUVECs. Furthermore, the activation of the Akt and Erk signaling pathways was detected in HUVECs upon treatment with simvastatin, and enhanced tube formation was reversed by LY294002 and PD98059, which indicated that both the Akt and Erk signaling pathways were involved in the process of angiogenesis induced by simvastatin. Moreover, simvastatin significantly up-regulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), which play essential roles in angiogenesis. For the in vivo experiments, simvastatin was incorporated into mesoporous hydroxyapatite microspheres (MHMs) synthesized using fructose 1,6-bisphosphate trisodium salt (FBP) as the phosphorous source by the microwave-assisted hydrothermal method. An simvastatin-loaded MHMs (S-MHMs) incorporated alginate hydrogel (S-MHMs/AH) was prepared as a wound dressing to promote the full-thickness cutaneous wound healing. The results demonstrated that S-MHMs/AH significantly enhanced new blood vessel formation and accelerated the reepithelialization of the cutaneous wounds. The present study suggests the potential application of the S-MHMs/AH composite as a novel dressing for wound healing.

Preparation of in situ forming and injectable alginate/mesoporous Sr-containing calcium silicate composite cement for bone repair

Injectable biomaterials to aid bone regeneration are worth investigating in bone tissue engineering due to minimized invasive damages. In this study, a novel in situ formed composite cement consisting of alginate and Sr-containing mesoporous calcium silicate nanoparticles (mSCS) has been designed. Firstly, mSCS were fabricated with Sr-substitution for Ca in mesoporous calcium silicate nanoparticles. The morphology, particle size, element mapping and mesoporous structure of the mSCS nanoparticles were characterized. The results showed that the nanoparticles were in the range from 200 nm to 300 nm, and had a surface area of about 312 m2 g−1. Then the mSCS materials were mixed with a sodium alginate solution. The alginate component in the composite cement was internally crosslinked by locally released Ca2+/Sr2+ cations from mSCS through the addition of D-gluconic acid δ-lactone (GDL). Characterization results showed that GDL accelerated the gelation rate of cement and thus increased the injectability coefficient to more than 90% after 2 minutes of setting. The higher amount of GDL enhanced the tridimensional network formation rate and improved the compressive strength and Youngs modulus of the cement. In addition, scanning electron microscopy (SEM) observations demonstrated that the alginate hydrogel provided extra micropores (tens of micrometers) for cell growth. The mSCS induced fast bone-like apatite deposition on the surface of all the cements after 3 days of SBF immersion. In vitro human bone mesenchymal stem cell (hBMSC) tests, including Cell Counting Kit-8 (CCK-8) assay and alkaline phosphatase (ALP) activity evaluation, revealed that the injectable mSCS–alginate cement had significant biocompatibility and low cytotoxicity, and moreover could support hBMSC proliferation and osteogenesis differentiation.

Synergistic effect of a biodegradable Mg–Zn alloy on osteogenic activity and anti-biofilm ability: an in vitro and in vivo study

It is desirable for orthopaedic implants to possess good osteointegration and anti-biofilm ability simultaneously for the prevention of implant associated infections and promotion of osteointegration. In this study, both of the anti-biofilm ability and osteogenic activity of a Mg–Zn alloy as a novel magnesium alloy were investigated systematically. The in vitro findings revealed that the Mg–Zn alloy promoted osteogenic differentiation and gene expression in the rat bone mesenchymal stem cells (rBMSCs), and showed better antibacterial ability than titanium (Ti). Good antibacterial ability was also observed in vivo in a rat distal femur model; the micro-CT and histological results revealed superior osteointegration of the Mg–Zn alloy in vivo despite the presence of methicillin-resistant Staphylococcus aureus (MRSA). The alkaline pH together with magnesium and zinc ions released from the Mg–Zn alloy may have synergistic effects on the antibacterial ability and osteogenic activity of the Mg–Zn alloy. The results demonstrate that the Mg–Zn alloy possesses osteointegration ability even in the presence of MRSA.