Recent Advances in the Preparation of Barium Sulfate Nanoparticles: A Mini-Review

The potential for barium sulphate nanoparticles to be used in a variety of important fields has sparked a lot of attention. Methods for obtaining this material by milling (top-down approach) are not very popular due to the difficulty of controlling the size and shape of particles, as well as changes in their physicochemical properties during milling. More promising is the bottom-up approach, which is the interaction of Ba2+ and SO42− ions in a liquid environment. Direct precipitation is the simplest method; however, it does not allow control of the particle size. Microemulsions, microreactors membrane dispersion, as well as spinning disc reactors are used to overcome drawbacks of direct precipitation and allow control of particle size and shape. This is ensured mainly by intensive controlled micromixing of the precursors with concentrations close to saturated ones. The present review focuses on recent advances in the production of barium sulfate nanoparticles using various approaches, as well as their advantages and limitations. The issues of scaling up the techniques are also considered, and promising methods for obtaining BaSO4 nanoparticles are also discussed.

Rapid Fabrication of MgNH4PO4·H2O/SrHPO4 Porous Composite Scaffolds with Improved Radiopacity via 3D Printing Process

Although bone repair scaffolds are required to possess high radiopacity to be distinguished from natural bone tissues in clinical applications, the intrinsic radiopacity of them is usually insufficient. For improving the radiopacity, combining X-ray contrast agents with bone repair scaffolds is an effective method. In the present research, MgNH₄PO₄·H₂O/SrHPO₄ 3D porous composite scaffolds with improved radiopacity were fabricated via the 3D printing technique. Here, SrHPO₄ was firstly used as a radiopaque agent to improve the radiopacity of magnesium phosphate scaffolds. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were used to characterize the phases, morphologies, and element compositions of the 3D porous composite scaffolds. The radiography image showed that greater SrHPO₄ contents corresponded to higher radiopacity. When the SrHPO₄ content reached 9.34%, the radiopacity of the composite scaffolds was equal to that of a 6.8 mm Al ladder. The porosity and in vitro degradation of the porous composite scaffolds were studied in detail. The results show that magnesium phosphate scaffolds with various Sr contents could sustainably degrade and release the Mg, Sr, and P elements during the experiment period of 28 days. In addition, the cytotoxicity on MC3T3-E1 osteoblast precursor cells was evaluated, and the results show that the porous composite scaffolds with a SrHPO₄ content of 9.34% possessed superior cytocompatibility compared to that of the pure MgNH₄PO₄·H₂O scaffolds when the extract concentration was 0.1 g/mL. Cell adhesion experiments showed that all of the scaffolds could support MC3T3-E1 cellular attachment well. This research indicates that MgNH₄PO₄·H₂O/SrHPO₄ porous composite scaffolds have potential applications in the bone repair fields.

Absorptive and expansive behaviors of poly(methyl methacrylate-co-acrylic acid) bone cement

Some additives had provided the expansion capacity to the polymethylmethacrylate (PMMA) bone cement and also reduced its maximum reaction temperature. However, the corresponding modified bone cement displayed inferior simulated body fluid (SBF) absorption capacity and expansion behavior, the mechanism of SBF absorption and the trend of expansion stress were ignored additionally. In this study, a homogeneous distribution of poly (methyl methacrylate-co-acrylic acid) [P(MMA-AA)] microspheres led to the formation of microchannels that favored the delivery of SBF to the interior, causing an increased absorption capacity and enhanced expansion behavior before solidification of the bone cement, with the maximum equilibrium absorption ratio and the expansion ratio reaching 27.3 % and 26.3 %, respectively, at an AA content of 50 %. In addition, the expansion stress induced by the expansion behavior experienced a gradual increase from the 0 s to 2590s, followed by a sharp climbed in a short period ranging from 2590s to 2900s, finally reaching maximum stress of 82.1 MPa. Furthermore, the expansion stress within the maximum value could be obtained by controlling the AA content in the P(MMA-AA) bone cement. With the above characteristics, the prepared P(MMA-AA) bone cement has potential applications as a filling and adhesive material in arthroplasties, vertebroplasties, joint replacements, bone screws, and dentistry.

Poly(propylene fumarate)/magnesium calcium phosphate injectable bone composite: Effect of filler size and its weight fraction on mechanical properties

This study aimed to produce a composite of poly(propylene fumarate)/magnesium calcium phosphate as a substitutional implant in the treatment of trabecular bone defects. So, the effect of magnesium calcium phosphate particle size, magnesium calcium phosphate:poly(propylene fumarate) weight ratio on compressive strength, Young's modulus, and toughness was assessed by considering effective fracture mechanisms. Micro-sized (∼30 µm) and nano-sized (∼50 nm) magnesium calcium phosphate particles were synthesized via emulsion precipitation and planetary milling methods, respectively, and added to poly(propylene fumarate) up to 20 wt.%. Compressive strength, Young's modulus, and toughness of the composites were measured by compressive test, and effective fracture mechanisms were evaluated by imaging fracture surface. In both micro- and nano-composites, the highest compressive strength was obtained by adding 10 wt.% magnesium calcium phosphate particles, and the enhancement in nano-composite was superior to micro-one. The micrographs of fracture surface revealed different mechanisms such as crack pinning, void plastic growth, and particle cleavage. According to the results, the produced composite can be considered as a candidate for substituting hard tissue.

Facile preparation of radium-doped, functionalized nanoparticles as carriers for targeted alpha therapy

A facile preparation of nanoparticles with enhanced properties obtained by co-precipitation containing radium-224 and functional groups to connect target (bio)molecules for therapeutic applications in oncology is described.

Radiopaque Fully Degradable Nanocomposites for Coronary Stents

Bioresorbable scaffolds (BRS) were introduced to overcome limitations of current metallic drug-eluting stents and poly-L-lactide (PLLA) has been used in the fabrication of BRS due to its biodegradability and biocompatibility. However, such polymers have weaker mechanical properties as compared to metals, limiting their use in BRS. We hypothesized that nanofillers can be used to enhance the mechanical properties considerably in PLLA. To this end, polymer-matrix composites consisting of PLLA reinforced with 5-20 wt% barium sulfate (BaSO4) nanofillers as a potential BRS material was evaluated. Stearic-acid (SA) modified BaSO4 nanofillers were used to examine the effect of functionalization. Rigid nanofillers improved the tensile modulus and strength of PLLA (60% and 110% respectively), while the use of SA-BaSO4 caused a significant increase (~110%) in the elongation at break. Enhancement in mechanical properties is attributed to functionalization which decreased the agglomeration of the nanofillers and improved dispersion. The nanocomposites were also radiopaque. Finite element analysis (FEA) showed that scaffold fabricated from the novel nanocomposite material has improved scaffolding ability, specifically that the strut thickness could be decreased compared to the conventional PLLA scaffold. In conclusion, BaSO4/PLLA-based nanocomposites could potentially be used as materials for BRS with improved mechanical and radiopaque properties.

Nafion®-coated mesoporous Pd film toward remarkably enhanced detection of lactic acid

Mesoporous metal films can detect biomarkers with high sensitivity. Further coating the mesoporous metal with polymers enhances sensing selectivity by favoring specific biomarkers against other interferents. In the present study, we report the fabrication of a Nafion®-coated mesoporous Pd film to filtrate interferents present in sweat during non-invasive biosensing. By using a Nafion®-coated mesoporous Pd film, lactic acid, a metabolite present in sweat, can be successfully detected with high sensitivity.

Controllable synthesis of nanostructured BaSO4 and BaSO3 crystals on the basis of DMSO oxidation chemistry

Controllable synthesis of BaSO₄ or BaSO₃ crystals on the basis of a SO₂ release method.

The Effect of Nanoparticles and Alternative Monomer on the Exothermic Temperature of PMMA Bone Cement

Poly methyl methacrylate (PMMA) cement produce exothermic reaction during its polymerization process, which damage the surrounding bone tissue during orthopedic surgery. Nanoparticles additives (magnesium oxide, hydroxyapatite, chitosan, barium sulfate and silica) and alternative monomers (glycidyl methacrylate(GMA) tri-methaxysilyl propyl methacrylate (3MPMA)), can be incorporated with the PMMA beads and methyl methacrylate (MMA) monomers, respectively, to reduce the exothermic temperature. A comparative study of the addition of these additives and monomer at different concentration on exothermic temperature of PMMA is not known and significant for designing improved PMMA cement for orthopedic applications. The goal of this study is two folds: (1) to evaluate the effect of the inclusion of the above additives with PMMA on the exothermic temperature of PMMA, (2) to evaluate the effect of the inclusion of the above alternative monomers on the exothermic temperature of PMMA. A commercial bone cement was used in this study as PMMA cement. Two wt% and six wt% of the above nanoparticle were mixed with PMMA beads. Two and six wt% of the above alterative monomers were mixed with MMA monomers. Bead and monomer ratio of 2:1 was maintained to prepare the cement samples. A 4-channel thermocouple was used to determine the temperature changes of the samples in an insulated acrylic mold during the curing period. This study found maximum curing temperature on the 2 wt% Magnesium oxide added PMMA specimen was significantly lower than other samples. Addition of 3MPMA and GMA to MMA decreased the maximum curing temperatures and curing time of specimens compared to other samples.

Mesoporous strontium doped nano sized sulphate hydroxyapatite as a novel biomaterial for bone tissue applications

In this study a novel nano-structured hydroxyapatite (HA) incorporated with different fractions of Sr²⁺ and SO₄²⁻ ions has been synthesized using the wet precipitation method and characterized.

Bone cements for percutaneous vertebroplasty and balloon kyphoplasty: Current status and future developments

Osteoporotic vertebral compression fractures (OVCFs) have gradually evolved into a serious health care problem globally. In order to reduce the morbidity of OVCF patients and improve their life quality, two minimally invasive surgery procedures, vertebroplasty (VP) and balloon kyphoplasty (BKP), have been developed. Both VP and BKP require the injection of bone cement into the vertebrae of patients to stabilize fractured vertebra. As such, bone cement as the filling material plays an essential role in the effectiveness of these treatments. In this review article, we summarize the bone cements that are currently available in the market and those still under development. Two major categories of bone cements, nondegradable acrylic bone cements (ABCs) and degradable calcium phosphate cements (CPCs), are introduced in detail. We also provide our perspectives on the future development of bone cements for VP and BKP.

Synthesis and characterization of novel TiO2-poly(propylene fumarate) nanocomposites for bone cementation

A novel composite material made from poly(propylene fumarate) (PPF) and titania nanofibers has been synthesized for potential use as an orthopaedic biomaterial with TiO₂ nanofibers chemically linked to the PPF matrix as a reinforcing phase to enhance its mechanical properties.