Incorporation of surface-modified hydroxyapatite into poly(methyl methacrylate) to improve biological activity and bone ingrowth

Mechanical and Bioactive Properties of PMMA Bone Cement: A Review

Over the past few decades, poly(methyl methacrylate) (PMMA) based bone cement has been clinically used extensively in orthopedics for arthroplasty and kyphoplasty, due to its biocompatibility and excellent primary fixation to the host bone. In this focused review, we discuss the use of various fillers and secondary chemical moieties to improve the bioactivity and the physicochemical properties. The viscosity of the PMMA blend formulations and working time are crucial to achieving intimate contact with the osseous tissue, which is highly sensitive to organic or inorganic fillers. Hydroxyapatite as a reinforcement resulted in compromised mechanical properties of the modified cement. The possible mechanisms of the additive- or filler-dependent strengthening or weakening of the PMMA blend are critically reviewed. The addition of layered double hydroxides with surface functionalization appears to be a promising approach to enhance the bonding of filler with the PMMA matrix. Such an approach consequently improves the mechanical properties, owing to enhanced dispersion as well as contributions from crack bridging. Finally, the use of emerging alternatives, such as nanoparticles, and the use of natural biomolecules were highlighted to improve bioactivity and antibacterial properties.

Surface Modification of Nano-Hydroxyapatite/Polymer Composite for Bone Tissue Repair Applications: A Review

Nano-hydroxyapatite (n-HA) is the main inorganic component of natural bone, which has been widely used as a reinforcing filler for polymers in bone materials, and it can promote cell adhesion, proliferation, and differentiation. It can also produce interactions between cells and material surfaces through selective protein adsorption and has therefore always been a research hotspot in orthopedic materials. However, n-HA nano-particles are inherently easy to agglomerate and difficult to disperse evenly in the polymer. In addition, there are differences in trace elements between n-HA nano-particles and biological apatite, so the biological activity needs to be improved, and the slow degradation in vivo, which has seriously hindered the application of n-HA in bone fields, is unacceptable. Therefore, the modification of n-HA has been extensively reported in the literature. This article reviewed the physical modification and various chemical modification methods of n-HA in recent years, as well as their modification effects. In particular, various chemical modification methods and their modification effects were reviewed in detail. Finally, a summary and suggestions for the modification of n-HA were proposed, which would provide significant reference for achieving high-performance n-HA in biomedical applications.

Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status

Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.

PMMA bone cement with L-arginine/nano fish bone nanocomplex for apatite formation

Bone cement is one of the materials used in orthopaedics that serves various functions, such as binding bone implants, replacing damaged bones and filling spaces within bones. Various materials have been used to synthesize bone cement, and one promising material for further research is fish bone waste-based bone cement. This study investigates the potential of fish bone waste-based bone cement by incorporating nano fish bone (NFB) and L-arginine (L-Arg) protein into polymethyl methacrylate (PMMA) to examine apatite growth. NFB derived from the Salmo salar fish positively influences osteoblast cell proliferation and differentiation, while L-Arg enhances biocompatibility and antibiotic properties. The NFB/L-Arg combination holds promise in accelerating new bone formation and cell growth, both of which are crucial for fracture healing and bone remodelling. Tensile strength tests reveal the superior performance of BC-PMMA-1-NFB/L-Arg (36.11 MPa) compared with commercial PMMA (32 MPa). Immersion tests with simulated body fluid (SBF) solution for 7 days reveal accelerated apatite layer formation, emphasizing the potential benefits of NFB/L-Arg in bone cement applications.

Enhanced mechanic properties of calcium phosphate cements via mussel-inspired adhesive as bone substitute: Highlights of their interactions

BACKGROUND

Inspired by natural bones, many organic components were added to Calcium Phosphate Cements (CPCs) to improve their mechanical strength. However, the strength of these composite CPCs is limited by the low strength of organic components itself and the weak interaction between organic components and CPCs.

OBJECTIVE

Firstly, a composite CPC containing mussel-inspired adhesive, Poly-(Dopamine Methacrylamide-co-2-methoxy Ethylacrylate) (pDM) was developed. Secondly, the interactions between pDM and CPC and their effect on mechanical properties were investigated.

METHODS

The interactions between pDM and CPC were performed by Nuclear Magnetic Resonance, Laser Raman, X-ray Photoelectron Spectroscopy, Fourier Transform-Infrared Spectroscopy and X-ray Diffraction Analysis.

RESULTS

The toughness and compressive strength of pDM-CPC scaffold were both significantly enhanced, because of the enhanced interface binding strength among CPC and pDM due to their interaction and the improved mechanical strength of pDM owing to its self-oxidation cross-linking. The toughness of pDM-CPC scaffolds increased with the increased contents of pDM, while pDM-CPC scaffold containing 35 wt.% pDM had the highest compressive strength of all, which the latter was more than five times compared to that of CPC.

CONCLUSION

The mechanically strong pDM-CPC scaffolds has potential application in bone regeneration as well as in craniofacial and orthopedic repair.

Feldspar-Modified Methacrylic Composite for Fabrication of Prosthetic Teeth

This study was aimed at investigating poly(methyl methacrylate) (PMMA), modified with a silanized feldspar filler at 10 wt.% and 30 wt.%, as a dental material system for the production of prosthetic teeth. Samples of this composite were subjected to a compressive strength test, three-layer methacrylic teeth were fabricated with the said materials, and their connection to a denture plate was examined. The biocompatibility of the materials was assessed via cytotoxicity tests on human gingival fibroblasts (HGFs) and Chinese hamster ovarian cells (CHO-K1). The addition of feldspar significantly improved the material's compressive strength, with neat PMMA reaching 107 MPa, and the addition of 30% feldspar raising it up to 159 MPa. As observed, composite teeth (cervical part made of neat PMMA, dentin with 10 wt.%, and enamel with 30 wt.% of feldspar) had good adhesion to the denture plate. Neither of the tested materials revealed any cytotoxic effects. In the case of hamster fibroblasts, increased cell viability was observed, with only morphological changes being noticed. Samples containing 10% or 30% of inorganic filler were determined to be safe for treated cells. The use of silanized feldspar to fabricate composite teeth increased their hardness, which is of significant clinical importance for the duration of use of non-retained dentures.

PCL-nHAC/Mg-Ca alloy composite and preliminary study of its osteogenesis property

Owing to their excellent properties, magnesium alloys are widely used in bone tissue engineering. However, considerable work has been conducted to control the degradation rate and improve the cytocompatibility of magnesium alloys. In this study, low-cost production introduced a new bone repair composite (PCL-nHAC/Mg-Ca), which was composed of nano-hydroxylapatite-collagen (nHAC), polycaprolactone (PCL) and Mg-Ca alloy substrate treated by micro- arc oxidation (MAO). The experimental results showed that compared with the Mg-Ca alloy treated by MAO alone, the PCL-nHAC/Mg-Ca composite has a porous structure and a slower degradation rate. Cell experiments showed that the PCL-nHAC/Mg-Ca composite had good biocompatibility and significantly enhanced the proliferation of the MC3T3-E1 cells. The rabbit skull defect model further proved that the PCL-nHAC/Mg-Ca composite could regulate the degradation rate of the Mg-Ca alloy and promote the formation of bone tissue. Histological analyses showed that the PCL-nHAC/Mg-Ca composite had good stability in vivo and could better accelerate bone formation.

Metformin-loaded β-TCP/CTS/SBA-15 composite scaffolds promote alveolar bone regeneration in a rat model of periodontitis

Periodontitis is a progressive infectious inflammatory disease, which leads to alveolar bone resorption and loss of periodontal attachment. It is imperative for us to develop a therapeutic scaffold to repair the alveolar bone defect of periodontitis. In this study, we designed a new composite scaffold loading metformin (MET) by using the freeze-drying method, which was composed of β-tricalcium phosphate (β-TCP), chitosan (CTS) and the mesoporous silica (SBA-15). The scaffolds were expected to combine the excellent biocompatibility of CTS, the good bioactivity of β-TCP, and the anti-inflammatory properties of MET. The MET-loaded β-TCP/CTS/SBA-15 scaffolds showed improved cell adhesion, appropriate porosity and good biocompatibility in vitro. This MET composite scaffold was implanted in the alveolar bone defects area of rats with periodontitis. After 12 weeks, Micro-CT and histological analysis were performed to evaluate different degrees of healing and mineralization. Results showed that the MET-loaded β-TCP/CTS/SBA-15 scaffolds promoted alveolar bone regeneration in a rat model of periodontitis. To our knowledge, this is the first report that MET-loaded β-TCP/CTS/SBA-15 scaffolds have a positive effect on alveolar bone regeneration in periodontitis. Our findings might provide a new and promising strategy for repairing alveolar bone defects under the condition of periodontitis.

PMMA Bone Cements Modified with Silane-Treated and PMMA-Grafted Hydroxyapatite Nanocrystals: Preparation and Characterization

In this study, vinyltrimethoxysilane-treated hydroxyapatite (vHAP) and PMMA-grafted HAP (gHAP) were successfully prepared from original HAP (oHAP). Three kinds of HAP (oHAP, vHAP and g HAP) were used as additives for the preparation of three groups of HAP-modified PMMA bone cements (oHAP-BC, vHAP-BC and gHAP-BC). The setting, bending and compression properties of the bone cements were conducted according to ISO 5833:2002. The obtained results showed that the maximum temperature while curing the HAP-modified bone cements (HAP-BCs) decreased from 64.9 to 60.8 °C and the setting time increased from 8.1 to 14.0 min, respectively, with increasing HAP loading from 0 to 15 wt.%. The vHAP-BC and gHAP-BC groups exhibited higher mechanical properties than the required values in ISO 5833. Electron microscopy images showed that the vHAP and gHAP nanoparticles were dispersed better in the polymerized PMMA matrix than the oHAP nanoparticles. FTIR analysis indicated the polar interaction between the PO₄ groups of the HAP nanoparticles and the ester groups of the polymerized PMMA matrix. Thermal gravimetric analysis indicated that mixtures of ZrO₂/HAPs were not able to significantly improve the thermal stability of the HAP-BCs. DSC diagrams showed that the incorporation of gHAP to PMMA bone cement with loadings lower than 10 wt.% can increase T_g by about 2.4 °C.

Boosting cell proliferation in three-dimensional polyacrylates/nanohydroxyapatite scaffolds synthesized by deep eutectic solvent-based emulsion templating

Among three-dimensional (3D) scaffold fabrication methods, porous polymers templated using high internal phase emulsions (HIPEs) have emerged as an attractive method due to the facile generation of interconnected porosity through a variety of synthetic routes. These include a bottom-up approach to selectively incorporate nanomaterials onto the inner walls in a nonaqueous environment. In this work, novel nonaqueous HIPEs made of different (meth)acrylate monomers and a deep eutectic solvent (DES) were formulated with nonfunctionalized nanohydroxyapatite (NHA), which also played the role of cosurfactant. Free radical polymerization of HIPEs yielded free-standing nanocomposites with 3D interconnected macroporosity and nonfunctionalized NHA selectively decorating the scaffolds' inner surface. The influence of different polymer functionalities, acrylate or methacrylate, their alkyl tail length, and the presence of NHA on MC3T3-E1 preosteoblast cell proliferation in vitro, reactive oxygen species (ROS) production and alkaline phosphatase (ALP) activity were evaluated. All materials presented promising biocompatibility, non-hemolytic activity, negligible inflammatory response along to remarkably enhanced cell proliferation (e.g., up to 160-fold cell proliferation increase compared with polystyrene plate) in vitro, which open the path for the development of scaffolds in regenerative medicine. It is noteworthy that polyHIPEs studied here were obtained using a green synthetic protocol where nonfunctionalized nanoparticles can be selectively incorporated into a scaffolds' inner walls. This versatile technique allows for the simple construction of 3D bioactive nanocomposite scaffolds with varied compositions for cell culture.

Cytotoxicity and cell response of preosteoblast in calcium sulfate-augmented PMMA bone cement

Poly(methyl methacrylate) (PMMA) has been widely used in orthopedic applications, but bone ingrowth and toxic monomer release are drawback of this material. Particle reinforcement with osteoconductive substitute, such as calcium sulfate (CaSO₄), is one of the solutions used to modify PMMA bone cement. The current study investigated the mechanical, chemical and biological properties of CaSO₄-augmented bone cement. Mechanical strength was measured by a material testing machine. The concentration of methyl methacrylate (MMA) monomer from the various formulations of PMMA mixed with CaSO₄was measured by ultra-performance liquid chromatography (UPLC). CCK-8 assay and ALP assay were performed to evaluate cytotoxicity of released MMA monomer and cell differentiation. The attachment of cells to CaSO₄-augmented bone cement discs was observed by confocal and scanning electron microscopy, and surface topography was also evaluated by atomic force microscopy. The results revealed that increased CaSO₄weight ratios led to compromised mechanical strength and increased MMA monomer release. Cell density and cell differentiation on CaSO₄-augmented bone cement discs were decreased at CaSO₄weight ratios above 10%. In addition, the presence of micropores on the surface and surface roughness were both increased for PMMA composite discs containing higher levels of CaSO₄. These results demonstrated that fewer MC3T3-E1 cells on the surface of CaSO₄-PMMA composites was correlated to increased MMA monomer release, micropore number and surface roughness. In summary, the augmentation of a higher proportion of CaSO₄(>10 wt. %) to PMMA did not promote the biological properties of traditional PMMA bone cement.

Preparation of ROS active and photothermal responsive hydroxyapatite nanoplatforms for anticancer therapy

Photothermal responsive nanoplatforms are attracting for photothermal therapy (PTT) of cancer. Herein, we propose a strategy to prepare IR-780 modified hydroxyapatite (HAP) nanorods as photothermic agents (HAP@IR-780). The results demonstrated that the obtained HAP@IR-780 was photothermal responsive under near-infrared laser irradiation the photothermal conversion efficiency was 69.3%, and it remained photostability after 4 cycles of irradiation. This advantage overcomes the optical instability of IR780. MTT and cellular uptake research proved that HAP@IR-780 was biocompatible in appropriate concentration range (0-20 μg/mL) without laser irradiation. Concentration-dependent internalization and reactive oxygen species (ROS) related apoptosis of HAP@IR-780 for MCF-7 cells were observed. Animal experiments showed that the gathered HAP@IR-780 at the tumor site reached a photothermal responsive temperature up to 57.9 °C, which could almost ablate the tumor with volumes as large as 1500 mm³. In general, our photothermal material has good photothermal conversion characteristics, and may have the least safety problems while showing excellent therapeutic effects. Therefore, HAP@IR-780 has a brilliant prospect in the field of tumor photothermal therapy.

Bioactive, Ion-Releasing PMMA Bone Cement Filled with Functional Graphenic Materials

Graphene oxide and functionalized graphenic materials (FGMs) have promise as platforms for imparting programmable bioactivity to poly(methyl methacrylate) (PMMA)-based bone cement. To date, however, graphenic fillers have only been feasible in PMMA cements at extremely low loadings, limiting the bioactive effects. At higher loadings, graphenic fillers decrease cement strength by aggregating and interfering with curing process. Here, these challenges are addressed by combining bioactive FGM fillers with a custom cement formulation. These cements contain an order of magnitude more graphenic filler than previous reports. Even at 1 wt% FGM, these cements have compressive strengths of 78- 88 MPa, flexural strengths of 74-81 MPa, and flexural stiffnesses of 1.8-1.9 GPa, surpassing the ASTM requirements for bone cement and competing with traditional PMMA cement. Further, by utilizing designer FGMs with programmed bioactivity, these cements demonstrate controlled release of osteogenic calcium ions (releasing a total of 5 ± 2 µmol of Ca2+ per gram of cement over 28 d) and stimulate a 290% increase in expression of alkaline phosphatase in human mesenchymal stem cells in vitro. Also, design criteria are described to guide creation of future generations of bone cements that utilize FGMs as platforms to achieve dynamic biological activity.

In Situ Generation of Hydroxyapatite on Biopolymer Particles for Fabrication of Bone Scaffolds Owning Bioactivity

Hydroxyapatite (HAP) can endow a biopolymer scaffold with good bioactivity and osteoconductive ability, while the interfacial bonding is fairly weak between HAP and biopolymers. In this study, HAP was in situ generated on poly(l-lactic acid) (PLLA) particles, and then they were used to fabricate a scaffold by selective laser sintering. Detailedly, PLLA particles were first functionalized by dopamine oxide polymerization, which introduced abundance active catechol groups on the particle surface, and subsequently, the catechol groups concentrated Ca²⁺ ions by chelation in a simulated body fluid solution, and then, Ca²⁺ ions absorbed PO₄^3- ions through electrostatic interactions for in situ nucleation of HAP. The results indicated that HAP was homogeneously generated on the PLLA particle surface, and HAP and PLLA exhibited good interfacial bonding in the HAP/PLLA scaffolds. Meanwhile, the scaffolds displayed excellent bioactivity by inducing apatite precipitation and provided a good environment for human bone mesenchymal stem cell attachment, proliferation, and osteogenic differentiation. More importantly, the ingrowth of blood vessel and the formation of new bone could be stimulated by the scaffolds in vivo, and the bone volume fraction and bone mineral density increased by 44.44 and 41.73% compared with the pure PLLA scaffolds, respectively. Serum biochemical indexes fell within the normal range, which indicated that there was no harmful effect on the normal functioning of the body after implanting the scaffold.

Effects of teriparatide versus percutaneous vertebroplasty on pain relief, quality of life and cost-effectiveness in postmenopausal females with acute osteoporotic vertebral compression fracture: A prospective cohort study

BACKGROUND

Osteoporotic vertebral compression fracture (OVCF) is a common disease in senior patients. Conservative treatments (usual care) and percutaneous vertebroplasty (PVP) are typically applied to treat OVCFs; however, their efficacies are not fully satisfactory. While Teriparatide (TPTD) is effective in both anti-osteoporosis and bone healing, whether TPTD could be applied as a conservative treatment for acute OVCFs remains unclear.

METHODS

This investigation represents a real-world prospective cohort study, where 60 postmenopausal women (≥55 years old) with acute OVCFs were equally assigned to a TPTD conservative group or PVP (plus alendronate) group based on the patient's choice. TPTD (20 μg, s.c., once daily) or alendronate (70 mg, p.o., once weekly) were administrated together with 0.6 mg Caltrate and 500 iu Vitamin D3 per day. A health survey (SF-36) was conducted at 0-, 1- and 3-months post-treatment. Back pain and the Oswestry Disability Index (ODI) were measured at 0-week, 1-week, 1-month and 3-months after treatment, while the direct medical cost was analyzed at the end of the third month.

RESULTS

Both treatments with TPTD and PVP significantly and similarly improved the patients' health quality, with reduced visual analogue and ODI scores at the end of the first and third months. PVP was more effective in reducing pain at the early time point (1 week, p < 0.05). 24 of 27 patients who were rescanned with magnetic resonance imaging in the TPTD group showed bone healing. The mid-vertebral height was increased by PVP (p < 0.05) but not by TPTD. The cost of TPTD treatment was 21,868.61 ± 167.05 RMB per capita, while the cost for PVP treatment was 33,265.95 ± 1491.11 RMB per capita (p < 0.05).

CONCLUSION

TPTD conservative treatment obtained similar therapeutic effects but cost less than PVP in terms of treating acute OVCF.