An injectable, biodegradable calcium phosphate cement containing poly lactic-co-glycolic acid as a bone substitute in ex vivo human vertebral compression fracture and rabbit bone defect models

Poly (lactic-co-glycolic acid)-encapsulated Endostar-loaded calcium phosphate cement as anti-tumor bone cement for the treatment of bone metastasis in lung cancer

Lung cancer is one of the most common malignant tumors in the world. In approximately 30%-40% of lung cancer patients, bone metastases ensues with osteolytic destruction. Worse still, intractable pain, pathological fracture, and nerve compression caused by bone metastases are currently the bottleneck of research, diagnosis, and treatment of lung cancer. Therefore, the present study aims at investigating the effectiveness of a new composite material made of calcium phosphate cement (CPC) and Endostar on repairing bone defects in vitro and in vivo. As indicated in results, the mechanical properties of CPC+Endostar and CPC+PLGA+Endostar do not differ from those of pure CPC. The PLGA-embedded Endostar slow-release microspheres were designed and prepared, and were combined with CPC. Poly (lactic-co-glycolic acid (PLGA) is a biodegradable polymer material in vivo, so the effect on its mechanical properties is negligible. CPC+Endostar and CPC+PLGA+Endostar have been proved to inhibit cell proliferation, promote apoptosis and block cell cycle in G2 phase; the expression levels of osteoclast-related genes CXCL2, TGF-β1, IGF-1, IL-6, and RANKL were significantly decreased while osteogenic ability and alkaline phosphatase activity observably enhanced. In vivo studies have revealed that the expression levels of TRAP, RANKL, and Caspase3 in CPC+PLGA+ENDO-treated tumor tissues after 3 weeks were higher than those in other groups with the prolongation of animal treatment time, while the expression levels of OPN and BCL2 were lower than those in other groups. In hematoxylin and eosin and TUNEL staining, 3 weeks of CPC+PLGA+ENDO-treatment yielded higher tissue necrosis and apoptosis than other groups; computed tomography and magnetic resonance imaging results showed the posterior edge bone damage reduced as a result of the CPC+PLGA+ENDO grafting in vertebral pedicle. Overall, the feasibility and reliability of CPC-loaded Endostar in the treatment of bone metastasis in lung cancer were investigated in this study, so as to promote the basic research and treatment of bone metastasis in lung cancer and other malignant tumors.

In Vivo Assessment of High-Strength and Corrosion-Controlled Magnesium-Based Bone Implants

The biodegradable nature of magnesium in aqueous mediums makes it an attractive material for various biomedical applications when it is not recommended that the material stay permanently in the body. Some of the main challenges that hinder the use of magnesium for bone fracture repair are its limited mechanical strength and fast corrosion rates. To this end, we developed a novel Mg-Zn-Ca-Mn-based alloy and post-fabrication methods that can deliver high-strength and corrosion-controlled implant materials to address these challenges. This study is focused on assessing the in vitro corrosion and in vivo biocompatibility of the developed magnesium-based alloy and post-fabrication processes. The developed heat treatment process resulted in an increase in the microhardness from 71.9 ± 5.4 HV for the as-cast Mg alloy to as high as 98.1 ± 6.5 HV for the heat-treated Mg alloy, and the ceramic coating resulted in a significant reduction in the corrosion rate from 10.37 mm/yr for the uncoated alloy to 0.03 mm/yr after coating. The in vivo assessments showed positive levels of biocompatibility in terms of degradation rates and integration of the implants in a rabbit model. In the rabbit studies, the implants became integrated into the bone defect and showed minimal evidence of an immune response. The results of this study show that it is possible to produce biocompatible Mg-based implants with stronger and more corrosion-controlled properties based on the developed Mg-Zn-Ca-Mn-based alloy and post-fabrication methods.

Magnesium (Mg2 +), Strontium (Sr2 +), and Zinc (Zn2 +) Co-substituted Bone Cements Based on Nano-hydroxyapatite/Monetite for Bone Regeneration

New bone cement type that combines Sr2 + /Mg2 + or Sr2 + /Zn2 + co-substituted nano-hydroxyapatite (n-HAs) with calcium phosphate dibasic and chitosan/gelatin polymers was developed to increase adhesion and cellular response. The cements were physicochemically described and tested in vitro using cell cultures. All cements exhibited quite hydrophilic and had high washout resistance. Cement releases Ca2 + , Mg2 + , Sr2 + , and Zn2 + in concentrations that are suitable for osteoblast proliferation and development. All of the cements stimulated cell proliferation in fibroblasts, endothelial cells, and osteoblasts, were non-cytotoxic, and produced apatite. Cements containing co-substituted n-HAs had excellent cytocompatibility, which improved osteoblast adhesion and cell proliferation. These cements had osteoinductive potential, stimulating extracellular matrix (ECM) mineralization and differentiation of MC3T3-E1 cells by increasing ALP and NO production. The ions Ca2 + , Mg2 + , Zn2 + , and Sr2 + appear to cooperate in promoting osteoblast function. The C3 cement (HA-SrMg5%), which was made up of n-HA co-substituted with 5 mol% Sr and 5 mol% Mg, showed exceptional osteoinductive capacity in terms of bone regeneration, indicating that this new bone cement could be a promising material for bone replacement.

Injectable nanofiber-reinforced bone cement with controlled biodegradability for minimally-invasive bone regeneration

Injectable materials show their special merits in regeneration of damaged/degenerated bones in minimally-invasive approach. Injectable calcium phosphate bone cement (CPC) has attracted broad attention for its bioactivity, as compared to non-degradable polymethyl methacrylate cement. However, its brittleness, poor anti-washout property and uncontrollable biodegradability are the main challenges to limit its further clinical application mainly because of its stone-like dense structure and fragile inorganic-salt weakness. Herein, we developed a kind of injectable CPC bone cement with porous structure and improved robustness by incorporating poly(lactide-co-glycolic acid) (PLGA) nanofiber into CPC, with carboxymethyl cellulose (CMC) to offer good injectability as well as anti-wash-out capacity. Furthermore, the introduction of PLGA and CMC also enabled a formation of initial porous structure in the cements, where PLGA nanofiber endowed the cement with a dynamically controllable biodegradability which provided room for cell movement and bone ingrowth. Interestingly, the reinforced biodegradable cement afforded a sustainable provision of Ca²⁺ bioactive components, together with its porous structure, to improve synergistically new bone formation and osteo-integration in vivo by using a rat model of femur condyle defect. Further study on regenerative mechanisms indicated that the good minimally-invasive bone regeneration may come from the synergistic enhanced osteogenic effect of calcium ion enrichment and the improved revascularization capacity contributed from the porosity as well as the lactic acid released from PLGA nanofiber. These results indicate the injectable bone cement with high strength, anti-washout property and controllable biodegradability is a promising candidate for bone regeneration in a minimally-invasive approach.

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Poly (lactide-co-glycolide) nanofiber incorporation reinforces the brittle CPC bone cement.

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The introduction of carboxymethyl cellulose offers good injectability and anti-washout resistance.

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PLGA nanofiber controllable biodegradability dynamically creates potential pores for bone formation and ingrowth.

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The cement continuously releases Ca²⁺ and lactic acid to improve bone regeneration and revascularization efficacy.

Role of Implantable Drug Delivery Devices with Dual Platform Capabilities in the Prevention and Treatment of Bacterial Osteomyelitis

As medicine advances and physicians are able to provide patients with innovative solutions, including placement of temporary or permanent medical devices that drastically improve quality of life of the patient, there is the persistent, recurring problem of chronic bacterial infection, including osteomyelitis. Osteomyelitis can manifest as a result of traumatic or contaminated wounds or implant-associated infections. This bacterial infection can persist as a result of inadequate treatment regimens or the presence of biofilm on implanted medical devices. One strategy to mitigate these concerns is the use of implantable medical devices that simultaneously act as local drug delivery devices (DDDs). This classification of device has the potential to prevent or aid in clearing chronic bacterial infection by delivering effective doses of antibiotics to the area of interest and can be engineered to simultaneously aid in tissue regeneration. This review will provide a background on bacterial infection and current therapies as well as current and prospective implantable DDDs, with a particular emphasis on local DDDs to combat bacterial osteomyelitis.

Ursolic acid loaded-mesoporous bioglass/chitosan porous scaffolds as drug delivery system for bone regeneration

Bioglass scaffolds have great application potentials in orthopedics, and Ursolic acid (UA) can effectively promote in vivo new bone formation. Herein, we for the first time developed the mesoporous bioglass/chitosan porous scaffolds loaded with UA (MBG/CS/UA) for enhanced bone regeneration. The MBG microspheres with particle sizes of ~300 nm and pore sizes of ~3.9 nm were uniformly dispersed on the CS films. The mesoporous structure within the MBG microspheres and the hydrogen bonding between the scaffolds and UA drugs made the MBG/CS/UA scaffolds have controlled drug release performances. The as-released UA drugs from the scaffolds increased remarkably the alkaline phosphatase activity, osteogenic differentiation related gene type I collagen, runt-related transcription factor 2 expression, and osteoblast-associated protein expression. Moreover, the results of micro-CT images, histomorphological observations demonstrated that the MBG/CS/UA scaffolds improved new bone formation ability. Therefore, the MBG/CS/UA porous scaffolds can be used as novel bone tissue engineering materials.