Fabrication and characterization of a bioactive polymethylmethacrylate-based porous cement loaded with strontium/calcium apatite nanoparticles

Printable and Tunable Bioresin with Strategically Decorated Molecular Structures

As personalized medicine rapidly evolves, there is a critical demand for advanced biocompatible materials surpassing current additive manufacturing capabilities. This study presents a novel printable bioresin engineered with tunable mechanical, thermal, and biocompatibility properties through strategic molecular modifications. The study introduces a new bioresin comprising methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), and a photoinitiator, which is further enhanced by incorporating high molecular weight polymethyl methacrylate (PMMA) to improve biostability and mechanical performance. The integration of printable PMMA presents several synthesis and processing challenges, necessitating substantial modifications to the 3D printing process. Additionally, the bioresin is functionalized with antibacterial silver oxide and bone-growth-promoting hydroxyapatite at various weight ratios to extend its application further. The results demonstrate the agile printability of the novel bioresin and its potential for transformative impact in biomedical applications, offering a versatile material platform for additive manufacturing-enabled personalized medicine. This work highlights the adaptability of the novel printable bioresin for real-life applications and its capacity for multiscale structural tailoring, potentially achieving properties comparable to native tissues and extending beyond conventional additive manufacturing techniques.

Strontium-containing mineralized phospholipid coatings improve osseointegration in osteoporotic rats

Surface treatments play an important role in enhancing the osseointegration of Titanium (Ti) and its alloys. This study introduces a method employing biomimetic hydroxyapatite (Hap) deposition guided by molecularly organized phospholipids, affixed to the metal implant surface. Using the Langmuir-Blodgett technique, phospholipids were deposited onto Ti-screws by using CaCl2 or CaCl2/SrCl2 aqueous solution in the subphase of a Langmuir trough in the target proportion (i.e. 10 and 90 mol% of Sr2+ in relation of Ca2+) followed by immersion in phosphate buffer and in supersaturated simulated body fluid. Coating composition and morphology were evaluated using infrared spectroscopy and scanning electron microscopy, respectively, while contact angle measurements assessed coating wettability and surface energy. Randomized screws were then implanted into the tibias of healthy and osteoporotic female rats (G1: Control-Machined, G2: Hap, G3: HapSr10, G4: HapSr90). Osseointegration, assessed 60 days post-implantation, included reverse torque, fluorochrome area, bone tissue-screw contact area, and linear extent of bone-screw contact. Results, grouped by surface treatment (Machined, Hap, HapSr10, HapSr90), revealed that the deposition of Hap, HapSr10, and HapSr90 resulted in thin and rough coatings composed of hydroxyapatite (Hap) on the screw surface with nanoscale pores. The coatings resulted in increased wettability and surface energy of Ti surfaces. The minerals are chemically similar to natural bone apatite as revealed by FTIR analysis. In vivo analyses indicated higher torque values for strontium-containing surfaces in the osteoporotic group (p = 0.02) and, in the control group superior torque for screw removal on the Hap surface (p = 0.023). Hydroxyapatite-treated surfaces enhance morphology, composition, and reactivity, promoting screw osseointegration in healthy and osteoporotic female rats. The incorporation of strontium into the mineral phase has been proposed to not only stimulate osteoblast activity but also reduce osteoclastic resorption, which may explain the improved outcomes observed here in experimental osteoporotic conditions.

Porous metal materials for applications in orthopedic field: A review on mechanisms in bone healing

Background

Porous metal materials have been widely studied for applications in orthopedic field, owing to their excellent features and properties in bone healing. Porous metal materials with different compositions, manufacturing methods, and porosities have been developed. Whereas, the systematic mechanisms on how porous metal materials promote bone healing still remain unclear.

Methods

This review is concerned on the porous metal materials from three aspects with accounts of specific mechanisms, inflammatory regulation, angiogenesis and osteogenesis. We place great emphasis on different cells regulated by porous metal materials, including mesenchymal stem cells (MSCs), macrophages, endothelial cells (ECs), etc.

Result

The design of porous metal materials is diversified, with its varying pore sizes, porosity material types, modification methods and coatings help researchers create the most experimentally suitable and clinically effective scaffolds. Related signal pathways presented from different functions showed that porous metal materials could change the behavior of cells and the amount of cytokines, achieving good influence on osteogenesis.

Conclusion

This article summarizes the current progress achieved in the mechanism of porous metal materials promoting bone healing. By modulating the cellular behavior and physiological status of a spectrum of cellular constituents, such as macrophages, osteoblasts, and osteoclasts, porous metal materials are capable of activating different pathways and releasing regulatory factors, thus exerting pivotal influence on improving the bone healing effect.

The translational potential of this article

Porous metal materials play a vital role in the treatment of bone defects. Unfortunately, although an increasing number of studies have been concentrated on the effect of porous metal materials on osteogenesis-related cells, the comprehensive regulation of porous metal materials on the host cell functions during bone regeneration and the related intrinsic mechanisms remain unclear. This review summarizes different design methods for porous metal materials to fabricate the most suitable scaffolds for bone remodeling, and systematically reviews the corresponding mechanisms on inflammation, angiogenesis and osteogenesis of porous metal materials. This review can provide more theoretical framework and innovative optimization for the application of porous metal materials in orthopedics, dentistry, and other areas, thereby advancing their clinical utility and efficacy.

A nontoxic strontium nanoparticle that holds the potential to act upon osteocompetent cells: An in vitro and in vivo characterization

Estrogen deficiency, long-term immobilization, and/or aging are commonly related to bone mass loss, thus increasing the risk of fractures. One option for bone replacement in injuries caused by either traumas or pathologies is the use of orthopedic cement based on polymethylmethacrylate (PMMA). Nevertheless, its reduced bioactivity may induce long-term detachment from the host tissue, resulting in the failure of the implant. In view of this problem, we developed an alternative PMMA-based porous cement (pPMMA) that favors cell invasion and improves osteointegration with better biocompatibility. The cement composition was changed by adding bioactive strontium-nanoparticles that mimic the structure of bone apatite. The nanoparticles were characterized regarding their physical-chemical properties, and their effects on osteoblasts and osteoclast cultures were assessed. Initial in vivo tests were also performed using 16 New Zealand rabbits as animal models, in which the pPMMA-cement containing the strontium nanoparticles were implanted. We showed that the apatite nanoparticles in which 90% of Ca2+ ions were substituted by Sr2+ (NanoSr 90%) upregulated TNAP activity and increased matrix mineralization. Moreover, at the molecular level, NanoSr 90% upregulated the mRNA expression levels of, Sp7, and OCN. Runx2 was increased at both mRNA and protein levels. In parallel, in vivo tests revealed that pPMMA-cement containing NanoSr 90%, upregulated two markers of bone maturation, OCN and BMP2, as well as the formation of apatite minerals after implantation in the femur of rabbits. The overall data support that strontium nanoparticles hold the potential to up-regulate mineralization in osteoblasts when associated with synthetic biomaterials.

Fe3O4/PMMA with Well-Arranged Structures Synthesized through Magnetic Field-Assisted Atom Transfer Radical Polymerization

Particle- or fiber-reinforced polymer composites with controlled orientations are attracting interest and applications producing innovative materials, biological constructs, and energy devices. To gain the controlled orientations, filed-assisted synthesis is widely selected for its easy operation and control. In this paper, we designed magnetic field-assisted equipment and synthesized a magnetic polymer composite Fe3O4/PMMA with a well-arranged layers structure by combining the magnetic field with atom transfer radical polymerization (ATRP). During the polymerization of polymer composites, the magnetic nanoparticles were surrounded by monomers. With the growth of polymer chains, the magnetic particles pushed polymer chains to move according to a specific direction and form a well-arranged structure under the magnetic fields. The existence of a well-arranged layered structure of the composites gives potential guidance for controlling the micro-structure by adding an extra field during the polymerization process. The experimental results provided a possible design to influence the macroscale properties through control of the micro-structure of polymer composites.

Bioactive mineralized small intestinal submucosa acellular matrix/PMMA bone cement for vertebral bone regeneration

Polymethylmethacrylate (PMMA) bone cement extensively utilized for the treatment of osteoporotic vertebral compression fractures due to its exceptional handleability and mechanical properties. Nevertheless, the clinical application of PMMA bone cement is restricted by its poor bioactivity and excessively high modulus of elasticity. Herein, mineralized small intestinal submucosa (mSIS) was incorporated into PMMA to prepare a partially degradable bone cement (mSIS-PMMA) that provided suitable compressive strength and reduced elastic modulus compared to pure PMMA. The ability of mSIS-PMMA bone cement to promote the attachment, proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells was shown through cellular experiments carried out in vitro, and an animal osteoporosis model validated its potential to improve osseointegration. Considering these benefits, mSIS-PMMA bone cement shows promising potential as an injectable biomaterial for orthopedic procedures that require bone augmentation.