Preparation and evaluation of parathyroid hormone incorporated CaP coating via a biomimetic method

Antimicrobial and Pro-Osteogenic Coaxially Electrospun Magnesium Oxide Nanoparticles-Polycaprolactone /Parathyroid Hormone-Polycaprolactone Composite Barrier Membrane for Guided Bone Regeneration

Introduction

An antibacterial and pro-osteogenic coaxially electrospun nanofiber guided bone regeneration (GBR) membrane was fabricated to satisfy the complicated and phased requirements of GBR process.

Methods

In this study, we synthesize dual-functional coaxially electrospun nanofiber GBR membranes by encapsulating parathyroid hormone (PTH) in the core layer and magnesium oxide nanoparticles (MgONPs) in the shell layer (MgONPs-PCL/PTH-PCL). Herein, the physicochemical characterization of MgONPs-PCL/PTH-PCL, the release rates of MgONPs and PTH, and antibacterial efficiency of the new membrane were evaluated. Furthermore, the pro-osteogenicity of the membranes was assessed both in-vitro and in-vivo.

Results

We successfully fabricated a coaxially electrospun nanofiber MgONPs-PCL/PTH-PCL membrane with the majority of nanofibers (>65%) ranged from 0.40~0.60μm in diameter. MgONPs-PCL/PTH-PCL showed outstanding antibacterial potential against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) through the release of MgONPs. We also discovered that the incorporation of MgONPs significantly prolonged the release of PTH. Furthermore, both the in-vivo and in-vitro studies demonstrated that high dosage of PTH promoted pro-osteogenicity of the membrane to improve bone regeneration efficacy with the presence of MgONPs.

Conclusion

The new composite membrane is a promising approach to enhance bone regeneration in periodontitis or peri-implantitis patients with large-volume bone defects.

Deferoxamine/magnesium modified β-tricalcium phosphate promotes the bone regeneration in osteoporotic rats

Recently, Deferoxamine (DFO) and magnesium (Mg) have been identified as critical factors for angiogenesis and bone formation. However, in current research studies, there is a lack of focus on whether DFO plus Mg can affect the regeneration of β-tricalcium phosphate (β-TCP) in osteoporosis and through what biological mechanisms. Therefore, the present work was aimed to preparation and evaluate the effect of Deferoxamine/magnesium modified β-tricalcium phosphate promotes (DFO/Mg-TCP) in ovariectomized rats model and preliminary exploration of possible mechanisms. The MC3T3-E1 cells were co-cultured with the exudate of DFO/Mg-TCP and induced to osteogenesis, and the cell viability, osteogenic activity were observed by Cell Counting Kit-8(CCK-8), Alkaline Phosphatase (ALP) staining, Alizarin Red Staining (RES) and Western Blot. In vitro experiments, CCK-8, ALP and ARS staining results show that the mineralization and osteogenic activity of MC3T3-E1increased significantly after intervention by DFO/Mg-TCP, as well as a higher levels of protein expressions including VEGF, OC, Runx-2 and HIF-1α. In vivo experiment, Micro-CT and Histological analysis evaluation show that DFO/Mg-TCP treatment presented the stronger effect on bone regeneration, bone mineralization and biomaterial degradation, when compared with OVX+Mg-TCP group and OVX+TCP group, as well as a higher VEGF, OC, Runx-2 and HIF-1α gene expression. The present study indicates that treatment with DFO/Mg-TCP was associated with increased regeneration by enhancing the function of osteoblasts in an OVX rat.

Local treatment with Sema3a could promote the osseointegration of hydroxyapatite coated titanium rod in diabetic rats

Recently, semaphorin 3A (Sema3A) has been identified as a critical gene for osteogenic differentiation of mesenchymal stem cells and increases osteoblastic bone formation. However, in current research studies, there is a lack of focus on whether Sema3a can affect the osseointegration of titanium rods in diabetes and through what biological mechanisms. Therefore, the present work was aimed to evaluate the effect of local administration with Sema3A on hydroxyapatite coated titanium rod osseointegration in diabetic rat model and preliminary exploration of possible mechanisms. The MC3T3-E1 cells were co-cultured with Sema3A and high glucose and induced to osteogenesis, and the cell viability, osteogenic activity was observed by Cell Counting Kit-8(CCK-8), Alkaline Phosphatase staining, Alizarin Red Staining, and Western Blot. In vitro experiments, CCK-8, ALP, and ARS staining results show that the mineralization and osteogenic activity of MC3T3-E1increased significantly after intervention by Sema3A, as well as a higher levels of protein expressions including Runt-Related Transcription Factor 2, silent mating type information regulation 2 homolog-1(SIRT1), catalase (CAT), superoxide dismutase 1 (SOD1), and superoxide dismutase 2 (SOD2). In vivo experiment, a better stability and osseointegration of the titanium rod were observed after treatment with Sema3A, as well as a higher SOD1, SOD2, CAT, and SIRT1 gene expression. The present study indicates that local treatment with Sema3A was associated with increased osseointegration of titanium rod by reducing the oxidative stress of osteoblasts and enhancing the function of osteoblasts in a diabetic rat.

Local administration with tauroursodeoxycholic acid could improve osseointegration of hydroxyapatite-coated titanium implants in ovariectomized rats

Despite advances in the pathogenesis of Tauroursodeoxycholic acid (TUDCA) on bone, the understanding of the effects and mechanisms of bone osseointegration in TUDCA-associated Hydroxyapatite (HA)-coated titanium implants remains poor. Therefore, the present work was aimed to evaluate the effect of local administration with TUDCA on HA-coated titanium implants osseointegration in ovariectomized(OVX) rats and further investigation of the possible mechanism. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into three groups: sham operation(Sham) group, OVX group and TUDCA group, and all the rats from Sham group and OVX group received HA implants and animals belonging to group TUDCA received TUDCA-HA implants until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. TUDCA increased new bone formation around the surface of titanium rods and push-out force other than group OVX. Histology, Micro-CT and biochemical analysis results showed systemic TUDCA showed positive effects than OVX group on bone formation in osteopenic rats, with beneficial effect on via activation OPG/RANKL pathway and BMP-2/Smad1 pathway and microarchitecture as well as by reducing protein expression of TNF-α and IFN-γ. The present study suggests that local use of TUDCA may bring benefits to the osseointegration of HA-coated titanium implants in patients with osteoporosis, and this effect may be related to the inhibition of inflammatory reaction and promotion of osteogenesis.

Synergistic use of biomaterials and licensed therapeutics to manipulate bone remodelling and promote non-union fracture repair

Disrupted bone metabolism can lead to delayed fracture healing or non-union, often requiring intervention to correct. Although the current clinical gold standard bone graft implants and commercial bone graft substitutes are effective, they possess inherent drawbacks and are limited in their therapeutic capacity for delayed union and non-union repair. Research into advanced biomaterials and therapeutic biomolecules has shown great potential for driving bone regeneration, although few have achieved commercial success or clinical translation. There are a number of therapeutics, which influence bone remodelling, currently licensed for clinical use. Providing an alternative local delivery context for these therapies, can enhance their efficacy and is an emerging trend in bone regenerative therapeutic strategies. This review aims to provide an overview of how biomaterial design has advanced from currently available commercial bone graft substitutes to accommodate previously licensed therapeutics that target local bone restoration and healing in a synergistic manner, and the challenges faced in progressing this research towards clinical reality.

Sequential delivery of BMP-7 and IGF-I to enhance the osteoinductive property of deproteinized bovine bone

Calcium phosphate coated deproteinized bovine bone with sequential delivery of BMP-7 and IGF-I has osteoinductive property to promote bone regeneration.

A review paper on biomimetic calcium phosphate coatings

Biomimetic calcium phosphate coatings have been developed for bone regeneration and repair because of their biocompatibility, osteoconductivity, and easy preparation. They can be rendered osteoinductive by incorporating an osteogenic agent, such as bone morphogenetic protein 2 (BMP-2), into the crystalline lattice work in physiological situations. The biomimetic calcium phosphate coating enables a controlled, slow and local release of BMP-2 when it undergoes cell mediated coating degradation induced by multinuclear cells, such as osteoclasts and foreign body giant cells, which mimics a physiologically similar release mode, to achieve sustained ectopic or orthotopic bone formation. Therefore, biomimetic calcium phosphate coatings are considered to be a promising delivery vehicle for osteogenic agents. In this review, we present an overview of biomimetic calcium phosphate coatings including their preparation techniques, physico-chemical properties, potential as drug carrier, and their pre-clinical application both in ectopic and orthotopic animal models. We briefly review some features of hydroxyapatite coatings and their clinical applications to gain insight into the clinical applications of biomimetic calcium phosphate coatings in the near future.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

3-D Scaffold Platform for Optimized Non-viral Transfection of Multipotent Stem Cells

Optimization of non-viral gene delivery from biomaterials is of critical importance, as several material parameters are known to influence non-viral transfection efficiency. A series of previous studies have achieved screening of gene delivery vectors on two dimensional (2D) substrates, which have direct relevance to cell culture applications. There is an additional need to create screening systems that are 3-dimensional (3D), and can thus be applied to emerging tissue engineering applications. Here, we report an enhanced throughput, 3D scaffold platform to screen for the influence of mineral coating properties on stem cell transfection. Mineral coatings with a range of physicochemical properties were formed on the scaffolds within a 96-well plate format, while maintaining an interconnected macroporous scaffold structure. A series of general gene delivery parameters, including plasmid amount, N/P ratio, and cell density, were efficiently screened in scaffolds using a luciferase-encoding plasmid as a reporter. In addition, human mesenchymal stem cell (hMSC) transfection with a plasmid encoding bone morphogenetic protein-2 (BMP-2) was successfully optimized by screening a library of mineral coatings, resulting in over 5-fold increases in BMP-2 production when compared to standard techniques. Notably, the majority of BMP-2 was incorporated into the mineral coating following secretion from the cells. The 3D mineral coated scaffold platform described here may accelerate gene delivery optimization and improve the predictability of the screening systems, which could facilitate translation of gene delivery to clinical applications.

Multilayered Inorganic Microparticles for Tunable Dual Growth Factor Delivery

There is an increasing need to control the type, quantity, and timing of growth factors released during tissue healing. Sophisticated delivery systems offering the ability to deliver multiple growth factors with independently tunable kinetics are highly desirable. Here, a multilayered, mineral coated micro-particle (MCMs) platform that can serve as an adaptable dual growth factor delivery system is developed. Bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF) are bound to the mineral coatings with high binding efficiencies of up to 80%. BMP-2 is firstly bound onto a 1st mineral coating layer; then VEGF is bound onto a 2nd mineral coating layer. The release of BMP-2 is sustained over a period of 50 days while the release of VEGF is a typical two-phase release with rapid release in the first 14 days and more sustained release for the following 36 days. Notably, the release behaviors of both growth factors can be independently tailored by changing the intrinsic properties of the mineral coatings. Furthermore, the release of BMP-2 can be tuned by changing the thickness of the 2nd layer. This injectable microparticle based delivery platform with tunable growth factor release has immense potential for applications in tissue engineering and regenerative medicine.

Local strategies to prevent and treat osteoporosis

Despite advances in systemic osteoporosis therapeutic outcomes, management of fragility fractures and implant fixation in osteoporotic bone remain difficult clinical challenges. Low initial bone density and a prolonged healing response can lead to fracture nonunion and aseptic implant loosening. Local treatment strategies could be used to prevent fracture, accelerate healing, and increase implant fixation by locally stimulating anabolic pathways or inhibiting catabolic pathways. Local strategies under investigation include direct drug release from injectable materials or implant surface coatings. Common locally delivered drugs include bisphosphonates, parathyroid hormone, and bone morphogenetic proteins, yet additional compounds targeting novel pathways in bone biology are also being actively explored. Mechanical stimulation via low intensity pulsed ultrasound, alone or in combination with drug therapy, may also prove effective to promote local bone healing and implant fixation within osteoporotic bone.

Modulation of Host Osseointegration during Bone Regeneration by Controlling Exogenous Stem Cells Differentiation Using a Material Approach

Stem cell-based tissue engineering for large bone defect healing has attracted enormous attention in regenerative medicine. However, sufficient osseointegration of the grafts combined with exogenous stem cells still remains a major challenge. Here we developed a material approach to modulate the integration of the grafts to the host tissue when exogenous bone marrow stromal cells (BMSCs) were used as donor cells. Distinctive osseointegration of bone grafts was observed as we varied the content of hydroxyapatite (HA) in the tissue scaffolds implanted in a mouse femur model. More than 80% of new bone was formed in the first two weeks of implantation in high HA content scaffold but lack of host integration while only less than 5% of the new bone was formed during this time period in the no HA group but with much stronger host integration. Cell origin analysis leveraging GFP reporter indicates new bone in HA containing groups was mainly derived from donor BMSCs. In comparison, both host and donor cells were found on new bone surface in the no HA groups which led to seamless bridging between host tissue and the scaffold. Most importantly, host integration during bone formation is closely dictated to the content of HA present in the scaffolds. Taken together, we demonstrate a material approach to modulate the osseointegration of bone grafts in the context of exogenous stem cell-based bone healing strategy which might lead to fully functional bone tissue regeneration.

Cellular performance comparison of biomimetic calcium phosphate coating and alkaline-treated titanium surface

The influence of biomimetic calcium phosphate coating on osteoblasts behavior in vitro is not well established yet. In this study, we investigated the behavior of osteoblastic rat osteosarcoma 17/2.8 cells (ROS17/2.8) on two groups of biomaterial surfaces: alkaline-treated titanium surface (ATT) and biomimetic calcium phosphate coated ATT (CaP). The cell attachment, proliferation, differentiation, and morphology on these surfaces were extensively evaluated to reveal the impact of substrate surface on osteoblastic cell responses. It was found that the ROS17/2.8 cells cultured on the ATT surface had higher attachment and proliferation rates compared to those on the CaP surface. Our results also showed that the calcium phosphate coatings generated in this work have an inhibiting effect on osteoblast adhesion and further influenced the proliferation and differentiation of osteoblast compared to the ATT surface in vitro. Cells on the ATT surface also exhibited a higher alkaline phosphatase activity than on the CaP surface after two weeks of culture. Immunofluorescence staining and scanning electron microscopy results showed that the cells adhered and spread faster on the ATT surface than on the CaP surface. These results collectively suggested that substrate surface properties directly influence cell adhesion on different biomaterials, which would result in further influence on the cell proliferation and differentiation.

Covalent Immobilization of Collagen on Titanium through Polydopamine Coating to Improve Cellular Performances of MC3T3-E1 Cells

Surface modification of orthopedic implants is critical for improving the clinical performance of these medical devices. Herein, collagen was covalently immobilized onto a titanium implant surface via a novel adherent polydopamine coating inspired by mussel adhesive proteins. The formation and composition of the collagen coating was characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Fluorescent labeled collagen was also used to examine the formation and uniformity of the collagen coating. The resultant collagen coating with a polydopamine supporting substrate demonstrated better uniformity and distribution on the titanium surface compared to a physical adsorption of collagen. The covalent immobilized collagen coating is biologically active, as evidenced by its ability to enhance MC3T3-E1 cell adhesion, support cell proliferation and promote early stage osteogenic differentiation of pre-osteoblasts. Our study suggests covalent immobilization of collagen through the polydopamine coating might be an efficient way to improve the cellular performance of implant surfaces.

Recommendations and considerations for the use of biologics in orthopedic surgery

Reconstruction of extensive bone defects remains technically challenging and has considerable medical and financial impact on our society. Surgical procedures often require a bone/substitute graft to enhance and accelerate bone repair. Bone autografts are associated with morbidity related to bone harvesting and are limited in quantity. Alternatively, bone allografts expose the patient to the risk of transmission of infectious disease. Synthetic bone graft substitutes, such as calcium sulfates, hydroxyapatite, tricalcium phosphate, and combinations, circumvent some of the disadvantages of auto- and allografts, but have limited indications. Biomedical research has made possible the stimulation of the body's own healing mechanisms, either by delivering exogenous growth factors locally, or by stimulating their local production by gene transfer. Among all known factors having osteoinductive properties, only two bone morphogenetic proteins (for specific indications) and demineralized bone matrix have been approved for clinical use. In addition, ongoing research is exploring the efficacy of cell therapy and tissue engineering. The present report examines the composition, biological properties, indications, clinical experience and regulations of several of the biotherapeutics employed for bone reconstruction.

Calcium phosphate cements as drug delivery materials

Calcium phosphate cements are used as synthetic bone grafts, with several advantages, such as their osteoconductivity and injectability. Moreover, their low-temperature setting reaction and intrinsic porosity allow for the incorporation of drugs and active principles in the material. It is the aim of the present work to: a) provide an overview of the different approaches taken in the application of calcium phosphate cements for drug delivery in the skeletal system, and b) identify the most significant achievements. The drugs or active principles associated to calcium phosphate cements are classified in three groups, i) low molecular weight drugs; ii) high molecular weight biomolecules; and iii) ions.

Biomimetic CaP coating incorporated with parathyroid hormone improves the osseointegration of titanium implant

Parathyroid hormone (PTH) is a well-known therapeutic agent for osteoporosis treatment, however, the inconvenience of daily administration and side effect from systematic administration severely limits its application in clinic. PTH has been incorporated into a biomimetic calcium phosphate (CaP) coating via a co-precipitation method in a modified simulated body fluid. The aim of the current study is to evaluate the osseointegration response of PTH incorporated CaP coating on titanium implants. Implants with different doses of PTH were inserted into tibiae of mice and evaluated by X-ray, micro-CT, histology and back-scattered scanning electron microscopy. Improved osseointegration of the implants loaded with PTH was observed compared to CaP coating only after 28 days of implantation in mouse tibiae. Micro-CT analysis showed better bone integration around the implant incorporated with PTH. Bone area and bone contact evaluations have demonstrated that peri-implant bone regeneration is highly dependent on the dosage of PTH incorporated. The higher the PTH content, the more bone formed surrounding the implant. Therefore, our results suggest that biomimetic CaP coating could be a useful a carrier for PTH local delivery, which results in improved bone-to-implant integration.