Hydroxyapatite Content Research Articles

Influence of Graphene, Hydroxyapatite, and Hydroxyapatite‐Niobium Pentoxide Nanoparticles on Polycaprolactone Electrospun Fibers Mats Properties

ABSTRACTPolycaprolactone (PCL) electrospun fiber mats containing varying concentrations of graphene flakes (GF), hydroxyapatite (HAp), and hydroxyapatite with niobium pentoxide (HAp5Nb) were successfully prepared by electrospinning. These composites exhibit great potential in biomedical applications, particularly as scaffolds for bone tissue engineering. The addition of GF enhances the rheological properties of the PCL solution due to the intrinsic properties resulting from their interactions. Additionally, incorporating HAp and HAp5Nb nanoparticles increases the viscosity of PCL‐based solutions, leading to the formation of thinner fiber diameters. The GF, HAp, and HAp5Nb nanoparticles were characterized using transmission electron microscopy (TEM) and x‐ray diffractometry (XRD), while the degree of disorder and heterogeneity of GF was assessed using Raman spectroscopy. The physical and chemical properties of the electrospun fiber mats were also characterized by scanning electron microscopy (SEM), XRD, fourier‐transform infrared spectroscopy (FTIR), and contact angle measurements. The cytotoxicity of PCL‐based electrospun fiber mats containing GF, HAp, and HAp5Nb nanoparticles was evaluated using mouse fibroblasts. Results showed that cell viability with 100% extract from the fiber mats was higher than with pure PCL or Dulbecco's modified Eagle's medium DMEM control, indicating that the samples were non‐toxic and promoted cell growth. This highlights their potential as scaffolds for bone tissue engineering.

Microarchitecture and Crystalline Composition: A Comprehensive Exploration of Salivary Gland Stones

ABSTRACTObjectiveTo investigate the microarchitecture and crystalline composition of sialoliths and to explore their formation mechanisms.MethodsSixty‐six sialolith samples (51 from the submandibular glands and 15 from the parotid glands) were retrospectively collected. Their diameter and quality were measured. Micro‐computed tomography, scanning electron microscopy, and polycrystalline X‐ray diffractometer (XRD) were utilized to determine their microstructure and crystalline composition.ResultsStone diameter and weight averaged at 9.6 mm and 0.31 g, respectively. Submandibular stones showed larger size and weight than parotid stones. Microstructurally, the main stones were concentric (n = 51) or mixed (n = 15). Most concentric stones occurred at submandibular glands, while 80% of the mixed stones were parotid stones. Stone surface exhibited three microscopic structures: lamellar, grape‐like, and porous, indicating their differences in mineralization process and composition. XRD revealed that all stones contained hydroxyapatite, with 57 containing whitlockite. Concentration of hydroxyapatite in concentric stones was significantly higher than that in mixed stones (p = 0.036) and correlated positively with stone diameter (p = 0.001). The microstructure and crystalline composition of multiple and recurrent stones were similar to that of single stones.ConclusionSialoliths display pronounced diversity in microarchitecture and crystalline composition, reflecting the differences in mineralization process and local microenvironments among stones.

Controlling pore size during the synthesis of hydroxyapatite nanoparticles using CTAB by the sol–gel hydrothermal method and their biological activities

Abstract Nanorod and nanosphere hydroxyapatite (HAP) particles were synthesized by the sol–gel hydrothermal method. The size of the synthesized HAP nanoparticles was controlled using cetyltrimethylammonium bromide (CTAB) as a templating agent with molar concentrations (HAP + 0.01 M CTAB, HAP + 0.03 M CTAB, and HAP + 0.1 M CTAB). The purity, size, shape, and elemental composition of HAP were determined using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy, which enabled us to determine the nanostructure formation. Further, Brunauer–Emmett–Teller analysis of the samples proves the size of the pores to be 7–10 nm. Thus, by altering the concentration of CTAB, HAP nanorods were induced along the c-axis. The zeta potential values of −34.7 and −28.7 mV confirmed the stability of pure HAP and HAP + 0.01 M CTAB. Further, the biological activities of the HAP nanoparticles were determined. In the anti-microbial activity test, an increase in the inhibition with an increase in the concentration of pure HAP to 0.1 M CTAB + HAP was observed against S. aureus, S. pyrogens, B. subtilis, E. aerogens, K. pneumoniae, and P. vulgaris. About 76% of antioxidant activity was obtained from the experiments. The drug-release behavior of doxorubicin-loaded pure HAP and CTAB-coated HAP also indicates that the % of drug delivery depends on the pores, which further depends on the CTAB concentration. The cytotoxic assay also revealed potential inhibitory effects against human cancer cell lines (MCF-7), with 65% cell viability recorded at a concentration of 500 μg/ml. These findings indicate that the pore size and shape of HAP play significant roles in their biological activities.

In Vitro Hydroxyapatite Nucleation in Cationically Cured Epoxy Composites with Pulverized Date Seed.

Recently, driven by a growing focus on environmental sustainability and cost-effectiveness, researchers have shown a keen interest in creating useful materials from bio-wastes, particularly for their potential applications in the biomedical field. Current research has been conducted on the impact of date seed powder (DSP) on hydroxyapatite (HA) formation, specifically in relation to the promotion of bone health and regeneration. HA is an essential component of bone tissue and plays a crucial role in maintaining bone strength and structure. Date seed (DS) was used in two forms i.e., grains and powder, with unmodified and modified surface chemistries. Prepared composites were tested in vitro by soaking them in simulated body fluid (SBF). X-ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) confirmed HA formation in all soaked samples. Thermogravimetric analysis (TGA) results indicated an improvement in thermal stability after soaking, suggesting a higher concentration of HA. Unsoaked samples were observed to have higher heat flow than soaked samples. The high gel content (GCs) over 90% and low hydrophilicity (less than 5%) of DSP-based composites were proven to be beneficial in HA nucleation. Antibacterial activity showed that the addition of DS filler yielded superior results compared to the pristine sample. Additionally, the modified samples demonstrated better antibacterial results than the unmodified ones.

3D-printed zinc oxide nanoparticles modified barium titanate/hydroxyapatite ultrasound-responsive piezoelectric ceramic composite scaffold for treating infected bone defects

Clinically, infectious bone defects represent a significant threat, leading to osteonecrosis, severely compromising patient prognosis, and prolonging hospital stays. Thus, there is an urgent need to develop a bone graft substitute that combines broad-spectrum antibacterial efficacy and bone-inductive properties, providing an effective treatment option for infectious bone defects. In this study, the precision of digital light processing (DLP) 3D printing technology was utilized to construct a scaffold, incorporating zinc oxide nanoparticles (ZnO-NPs) modified barium titanate (BT) with hydroxyapatite (HA), resulting in a piezoelectric ceramic scaffold designed for the repair of infected bone defects. The results indicated that the addition of ZnO-NPs significantly improved the piezoelectric properties of BT, facilitating a higher HA content within the ceramic scaffold system, which is essential for bone regeneration. In vitro antibacterial assessments highlighted the scaffold's potent antibacterial capabilities. Moreover, combining the synergistic effects of low-intensity pulsed ultrasound (LIPUS) and piezoelectricity, results demonstrated that the scaffold promoted notable osteogenic and angiogenic potential, enhancing bone growth and repair. Furthermore, transcriptomics analysis results suggested that the early growth response-1 (EGR1) gene might be crucial in this process. This study introduces a novel method for constructing piezoelectric ceramic scaffolds exhibiting outstanding osteogenic, angiogenic, and antibacterial properties under the combined influence of LIPUS, offering a promising treatment strategy for infectious bone defects.

3D Printing and Property of Biomimetic Hydroxyapatite Scaffold.

The 3D printing of a biomimetic scaffold with a high hydroxyapatite (HA) content (>80%) and excellent mechanical property is a serious challenge because of the difficulty of forming and printing, insufficient cohesion, and low mechanical property of the scaffold. In this study, hydroxyapatite whiskers (HAWs), with their superior mechanical property, biodegradability, and biocompatibility, were used to reinforce spherical HA scaffolds by 3D printing. The compressive strength and energy absorption capacity of HAW-reinforced spherical HA (HAW/HA) scaffolds increased when the HAW/HA ratio increased from 0:10 to 4:6 and then dropped with any further increases in the HAW/HA ratio. Bioceramic content (HAWs and spherical HA) in the scaffolds reached 83%, and the scaffold with a HAW/HA ratio of 4:6 (4-HAW/HA) exhibited an optimum compressive strength and energy absorption capacity. The scaffold using polyvinyl alcohol (PVA) as an additive possessed a good bonding between HA and PVA as well as a higher strength, which allowed the scaffold to bear a higher stress at the same strain. The compressive strength and toughness of the 4-HAW/HA-PVA scaffold were 1.96 and 1.63 times that of the 4-HAW/HA scaffold with hydroxypropyl methyl cellulose (HPMC), respectively. The mechanical property and inorganic components of the biomimetic HAW/HA scaffold were similar to those of human bone, which would make it ideal for repairing bone defects.

Influence of Hydroxyapatite and Gelatin Content on Crosslinking Dynamics and HDFn Cell Viability in Alginate Bioinks for 3D Bioprinting.

This study investigates how varying concentrations of hydroxyapatite (OHAp) and the addition of gelatin influence the ionic crosslinking time of alginate-based bioinks, as well as the shear stress experienced by neonatal human dermal fibroblasts (HDFn) during extrusion. These factors are crucial for validating bioinks and developing viable 3D bioprinted models. Four bioink formulations were created with a 50/50 ratio of alginate to gelatin, incorporating different calcium phosphate concentrations (0%, 1%, 5%, and 10%). The bioink compositions were confirmed via Fourier Transform Infrared (FT-IR) spectroscopy, and rheological analyses evaluated their pseudoplastic behavior, printability limits, and crosslinking times. The results indicated a notable increase in the consistency index (k) from 0.32 for the 0% OHAp formulation to 0.48 for the 10% OHAp formulation, suggesting improved viscoelastic properties. The elastic modulus recovery after crosslinking rose significantly from 245 Pa to 455 Pa. HDFn experienced a shear stress of up to 1.5436 Pa at the tip during extrusion with the HDFn-ALG5-GEL5-OHAp10 bioinks, calculated at a shear rate as low as 2 s-1. Viability assays confirmed over 70% cell viability 24 h post-extrusion and 92% viability after 7 days for the 10% OHAp formulation, highlighting the potential of hydroxyapatite-enhanced bioinks in tissue engineering applications.

Synthesis and In Vitro Testing of Mg-6Zn-xHAp Biocomposites from Beef Bone as Biodegradable Bone Implant Material

This study aimed to develop biodegradable Mg-6Zn hydroxyapatite (Mg-6Zn HAp) biocomposites for potential use in bone replacement applications. The hydroxyapatite (HAp) powders, sourced from cow bone, were synthesized through an eco-friendly and cost-effective process, leveraging bioresources for material sustainability. The Mg-6Zn and HAp powders were mechanically mixed through ball milling for six hours to ensure homogeneity. The resultant powder mixture was then subjected to isostatic pressing at a high pressure of 570 MPa, forming a dense coin-shaped composite with a 1.5 cm diameter. This coin was consolidated in a capsule furnace at elevated temperatures for one hour to enhance material integrity. The Mg-6Zn HAp alloy was thoroughly characterized using X-ray diffraction (XRD) to assess phase formation and crystallographic structure, and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDX) to examine microstructural features and elemental composition. For composite preparation, varying amounts of HAp (5%, 8%, and 12%) were incorporated into the Mg-6Zn matrix. SEM analyses revealed a uniform distribution of HAp particles along the boundaries of matrix particles, enhancing composite structure and stability. Results demonstrated that with an increase in HAp content, there was a corresponding improvement in the relative density and hardness of the composites. The corrosion rate decreased with higher HAp content, indicating improved biocompatibility and stability in physiological environments. This suggests that the Mg-6Zn HAp biocomposites, with their tailored microstructure and enhanced mechanical properties, hold promise for use in biodegradable bone replacement applications.

Study of Polysulfone-Impregnated Hydroxyapatite for Ultrafiltration in Whey Protein Separation.

Polysulfone (Psf) ultrafiltration flat-sheet membranes were modified with hydroxyapatite (HA) powder during preparation using the wet-phase inversion method. HA was incorporated to enhance the protein separation capabilities. The asymmetric Psf membranes were synthesized using NMP as the solvent. Through Scanning Electron Microscopy (SEM) analysis, it was revealed that HA was distributed across the membrane. Incorporating HA led to higher flux, the improved rejection of protein, and enhanced surface hydrophilicity. The permeability flux increased with HA concentration, peaking at 0.3 wt.%, resulting in a 38% improvement to 65 LMH/bar. Whey protein separation was evaluated using the model proteins BSA and lysozyme, representing α-Lactalbumin. The results of protein rejection for the blend membranes indicated that the rejection rates for BSA and lysozyme increased to 97.2% and 73%, respectively. Both the native and blend membranes showed similar BSA rejection rates; however, the blend membranes demonstrated better performance in lysozyme separation, indicating superior selectivity compared to native membranes. The modified membranes exhibited improved hydrophilicity, with water contact angles decreasing from 66° to 53°, alongside improved antifouling properties, indicated by a lower flux decline ratio value. This simple and economical modification method enhances permeability without sacrificing separation efficiency, hence facilitating the scalability of membrane production in the whey protein separation industry.

Boosting α to β transformation of PVDF/HFP through natural hydroxyapatite derived from animal bones for eco-friendly energy harvesters

Appropriate additives can significantly enhance the piezoelectric properties of piezoelectric materials. In particular, eco-friendly ceramics made from natural sources, such as animal bones, can be produced in a low-energy process and contribute to a lower carbon footprint. In this study, hydroxyapatite (HA) particles were produced by synthesizing natural bovine bone by means of mechanosynthesis route and employed as nucleating agents to enhance self-polarization of piezoelectric polymers. With a simple and eco-friendly manufacturing process, the HA is embedded in polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). Scanning electron microscope (SEM), and Fourier transform infrared spectroscopy analysis (FTIR) were used to examine the distribution uniformity of hydroxyapatite particles and investigate the effect of particles on the crystallinity of polymer composite. In addition, electrical and piezoelectric measurements were conducted to illustrate the effect of HA contents on the performance of the realized films. By increasing the contents of HP, the relative fraction of β-phase increased sharply for 20 wt % HA/PVDF-HFP film, leading to high piezoelectric performance. The films made with 20 wt%HA/PVDF-HFP had a maximum output voltage of 2 V and a maximum output power of 1.75 μW and were 0.8 V and 0.25 μW for the pristine PVDF-HFP film illustrating the significant role of HA for α-to β-phase transformation. Furthermore, adding 20 wt % hydroxyapatite (HA) to PVDF-HFP enhanced the dielectric properties. Under walking, the realized biocomposite was able to harvest body energy into useable electricity up to 4 V. In this study, bio-derived materials are shown to have great potential for affordable eco-friendly nanogenerators that produce electricity from body movements.

One-Pot Hybridization of Microfibrillated Cellulose and Hydroxyapatite as a Versatile Route to Eco-Friendly Mechanical Materials.

Hydroxyapatite was crystallized in an alkaline dispersion of mechanically fibrillated cellulose to prepare their composites with hydroxyapatite contents of 26-86 wt %. The composite powder was uniaxially pressed at 120 °C and 300 MPa to obtain the compacts. Three-point bending tests revealed that the bending strengths of the compacts were 40-100 MPa, and the elastic moduli were 4-9 GPa. The composite containing 43% hydroxyapatite showed the largest bending strength and the largest work of fracture, and the composite containing 62% hydroxyapatite showed the largest elastic modulus. The composites, derived from the bioderived eco-friendly materials, showed the mechanical properties comparable to those of engineering plastics such as polyamide-6. Scanning electron microscopic observation of the fracture surface showed that the organic phase was discontinuous when the hydroxyapatite weight fraction was increased from 43% to 62%, and the compacts with a discontinuous organic phase lost toughness.

An immunomodulatory and osteogenic bacterial cellulose scaffold for bone regeneration via regulating the immune microenvironment

Creating a bone homeostasis microenvironment that balances osteogenesis and immunity is a substantial challenge for bone regeneration. Here, we prepared an immunomodulatory and osteogenic bacterial cellulose scaffold (FOBS) via a facile one-pot approach. The aldehyde groups were generated via selective oxidation of the hydroxyl groups of bacterial cellulose, offering the bonding sites for dopamine through a Schiff base reaction. At the same time, the deposition of Ca2+ and PO43− was promoted on the aldehyde cellulose scaffold because of the high affinity of the catechol moiety for Ca2+. Compared with that of the unmodified scaffold, the hydroxyapatite content of FOBS increased by 47.1 % according to the ICP results. Interestingly, FOBS regulated the immune microenvironment to accelerate the conversion of M1 to M2 macrophages. The expressions of ARG-1 and Dectin-1 (M2) in the FOBS group increased by >100 %. The expression of osteogenic differentiation of BMSCs was also upregulated. In a rat cranial defect model, the BV/TV of FOBS was significantly increased. Further immunohistochemical analysis revealed that an improved immune microenvironment promoted the osteogenic differentiation of stem cells in vivo. This work provides an effective and easy-to-operate strategy for the development of the bone tissue engineering scaffolds.

Coaxial Electrospun wound dressing integrated with Ag-doped hydroxyapatite for wound healing: Tetracycline delivery

The human body's natural defense against inflammation in wounds can sometimes be insufficient. Introducing a wound dressing with this capability could significantly enhance the healing process. This study aimed to create a PVP/PVA-based coaxial electrospun wound dressing integrated with tetracycline-loaded Ag-doped hydroxyapatite (Ag@iHA) in three concentrations [G1, G2, and G3]) with a focus on drug release and antibacterial activity. Nanoparticles were analyzed using DLS, Zeta potential, SEM, EDX, XRD, and FTIR. The final wound dressing was studied from the viewpoint of physicochemical properties biologically, and finally, it was assessed under an in vivo study (9 Wistar rats, six days). Drug release was measured at three pH (5.4, 7, and 9). The results showed a remarkable success in the integration of silver ion in the hydroxyapatite structure, with a 90–600 nm size. Increasing the content of hydroxyapatite improved the quality of nanofibers that were produced. The nanofibers had high hydrophilicity (<5˚) and swelling rates (70–118 %), which were wholly degraded after 14 days. The amount of the released drug was completely different at each pH and was higher in an alkaline environment, as seen in wounds. The survival percentage (>90 %) of L929 cells showed the biocompatibility of nanofibers. In the animal study, all groups reduced the growth of microorganisms, but the most efficacy belonged to the G3 group. In conclusion, this novel wound dressing has the potential to significantly accelerate the body's natural healing process by controlling the growth of microorganisms.

Development of hydroxyapatite/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/gelatin composite nanofibers to improve bone‐forming cell proliferation and mineral deposition

AbstractCalcium phosphate hydroxyapatite (HA) was successfully incorporated into poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/gelatin (PHBV/GEL) nanofibers through an electrospinning process in a hexafluoroisopropanol solvent (HFIP). The PHBV/GEL was electrospun and collected using a rotating metallic network to develop highly ordered nonwoven mats. The effects of HA addition on the morphologies of the obtained fibers were investigated using SEM. The average diameter of the fibers ranged around 700–900 nm, depending on the HA content. From a mechanical perspective, the addition of HA nanoparticles showed variations in tensile strength and elastic modulus values. The lowest tensile strength measured for neat PHBV/GEL was 0.37 ± 0.08 MPa with an elastic modulus of 9.45 ± 0.65 MPa, whereas the highest tensile strength reported for 5% HA‐loaded PHBV/GEL mats was 1.1 ± 0.4 MPa with an elastic modulus of 16.9 ± 0.39 MPa. In addition, cell viability, and mineral deposition were also studied using MC3T3‐E1 pre‐osteoblasts. The in vitro experiment results showed that the HA loaded‐PHBV/GEL mats provide optimal conditions for cell growth and osteogenic differentiation of MC3T3‐E1 cells. This study reveals the potential of PHBV/GEL/HA matrices in the development of novel guided bone‐regeneration (GBR) membranes for orthopedic and craniomaxillofacial surgery, by providing favorable structural features for attachment, growth, and differentiation of osteoblast cells.Highlights Simple and cheap electrospinning strategy toward network‐like fibrous mats. Microstructure, mechanical, and biological features were evaluated. Electrospun PHBV/GEL/HA promoted calcium phosphate deposition by MC3T3‐E1 cells.

Optimizing locally delivered periodontitis therapy: Development of chitosan‐hydroxyapatite‐encapsulated drug via electrospraying

AbstractThis study presents the development of an optimized drug delivery system for periodontitis treatment utilizing chitosan‐hydroxyapatite nanoparticles. Employing the electrospraying technique, researchers encapsulated the antibiotic amoxicillin within chitosan‐hydroxyapatite composite matrices while varying the concentrations of chitosan and hydroxyapatite nanoparticles. The resulting microparticles displayed sizes ranging from 276 to 386 μm. Characterization of the produced drug encapsulations indicated that higher concentrations of chitosan and hydroxyapatite resulted in the formation of larger particles with rougher surfaces, increased mechanical strength, and enhanced thermal stability. Notably, nanoindentation analysis revealed an increase in hardness from 0.21 to 0.35 GPa, and in elastic modulus from 5.32 to 8.72 GPa with escalating chitosan and hydroxyapatite content, meeting or surpassing requirements for load‐bearing regenerative biomaterials. In vitro drug release assessments exhibited sustained amoxicillin release over 24 h, predominantly through diffusion and dissolution mechanisms. Formulations with lower polymer and mineral content showcased elevated release rates, with the F1 encapsulation (0.5% chitosan, 0.2% HAP) achieving a cumulative release of 78.3 ± 3.2% in contrast to 65.1 ± 2.7% for the F5 formulation (2.5% chitosan, 1% HAP). These encapsulations selectively modulated the overproduction of proinflammatory cytokines, including IL‐1β, IL‐6, and TNF‐α, in gingival fibroblasts and osteoblasts without compromising cell viability. An artificial neural network (ANN) model accurately forecasted the material properties and biological performance of the formulations based on their compositional variations, yielding correlation coefficients exceeding 0.97. This computational platform offers a virtual screening tool for refining regenerative and drug delivery therapies. The developed chitosan‐hydroxyapatite microparticulate system demonstrates promising potential for prolonged treatment of periodontitis through controlled antibiotic delivery, improved mechanical properties, and targeted regulation of the inflammatory response.

Injectable mineralized Sr-hydroxyapatite nanoparticles-loaded ɛ-polylysine-hyaluronic acid composite hydrogels for bone regeneration

In this study, multifunctional injectable mineralized antibacterial nanocomposite hydrogels were prepared by a homogenous distribution of high content of (up to 60 wt%) Sr-substituted hydroxyapatite (Sr-HAp) nanoparticles into covalently cross-linked ɛ-polylysine (ɛ-PL) and hyaluronic acid (HA) hydrogel network. The developed bone-targeted nanocomposite hydrogels were to synergistically combine the functional properties of bioactive Sr-HAp nanoparticles and antibacterial ɛ-PL-HA hydrogels for bone tissue regeneration. Viscoelasticity, injectability, structural parameters, degradation, antibacterial activity, and in vitro biocompatibility of the fabricated nanocomposite hydrogels were characterized. Physical performances of the ɛ-PL-HA hydrogels can be tailored by altering the mass ratio of Sr-HAp. The nanocomposite hydrogels revealed good stability against enzymatic degradation, which increased from 5 to 19 weeks with increasing the mass ratio of Sr-HAp from 40 % to 60 %. The loading of the Sr-HAp at relatively high mass ratios did not suppress the fast-acting and long-term antibacterial activity of the ɛ-PL-HA hydrogels against S. aureus and E. coli. The cell studies confirmed the cytocompatibility and pre-collagen I synthesis-promoting activity of the fabricated nanocomposite hydrogels.

Corrosion Behavior and Biological Properties of ZK60/HA Composites Prepared by Laser Powder Bed Fusion.

Magnesium alloy ZK60 shows great promise as a medical metal material, but its corrosion resistance in the body is inadequate. Hydroxyapatite (HA), the primary inorganic component of human and animal bones, can form chemical bonds with body tissues at the interface, promoting the deposition of phosphorus products and creating a dense calcium and phosphorus layer. To enhance the properties of ZK60, HA was added to create HA/ZK60 composite materials. These composites, fabricated using the advanced technique of LPBF, demonstrated superior corrosion resistance and enhanced bone inductive capabilities compared to pristine ZK60. Notably, the incorporation of 3 wt% led to a significant reduction in bulk porosity, achieving a value of 0.8%. The Ecorr value increased from -1.38 V to -1.32 V, while the minimum Icorr value recorded at 33.9 μA·cm-2. Nano-HA achieved the lowest volumetric porosity and optimal corrosion resistance. Additionally, these composites significantly promoted osteogenic differentiation in bone marrow stromal cells (BMSCs), as evidenced by increased alkaline phosphatase (ALP) activity and robust calcium nodule formation, highlighting their excellent biocompatibility and osteo-inductive potential. However, when increasing the HA content to 6 wt%, the bulk porosity rose significantly to 3.3%. The Ecorr value was -1.3 V, with the Icorr value being approximately 50 μA·cm-2. This increase in porosity and weaker interfacial bonding, ultimately accelerated electrochemical corrosion. Therefore, a carefully balanced amount of HA significantly enhances the performance of the ZK60 magnesium alloy, while excessive amounts can be detrimental.

Photoactivated riboflavin-doped hydroxy apatite nanospheres infiltered in orthodontic adhesives.

To assess micro-tensile bond strength (μTBS), degree of conversion (DC), microleakage (ML) antibacterial efficacy, and adhesive remnant index (ARI) of orthodontic brackets to enamel with different concentrations of photoactivated riboflavin-doped hydroxyapatite (HA) nanospheres (NS) (0%,1%,5% and 10%) and 0.5 wt% RF alone in orthodontic adhesive. Samples were included on the predefined inclusion criteria and positioned up to the cementoenamel junction (CEJ). Hydroxy apatite nanospheres (HANS) commercially bought were doped with RF. Surface characterization of HANS and RF-doped HANS were assessed along with EDX analysis. Samples were grouped based on experimental orthodontic adhesive modification. Group 1: Transbond XT no modification, Group 2: experimental Transbond XT 0.5 wt% RF, Group 3: experimental Transbond XT 0.5 wt% RF-doped 1% HANS, Group 4: experimental Transbond XT 0.5 wt % RF-doped 5% HANS and Group 5: Experimental Transbond XT 0.5 wt% RF-doped 10% HANS. Brackets were placed based on different adhesive modifications and samples underwent thermocycling. Samples were evaluated for μTBS, DC, and ML. The type of failure was assessed using ARI. Adhesive modified and un-modified in four different concentrations (0%, 1%, 5%, and 10%) and 0.5 wt% RF only were used to test efficacy against Streptococcus mutans (S.mutans). The survival rate of S.mutans and ML was determined using the Kruskal-Wallis Test. For the analysis of μTBS, ANOVA was employed, followed by a post-hoc Tukey HSD multiple comparisons test. The highest μTBS and lowest ML were observed in Group 2 experimental Transbond XT 0.5 wt% RF only. The lowest μTBS, highest ML, and lowest DC was seen in Group 5 experimental Transbond XT 0.5 wt% RF-doped 10% HANS. Samples in Group 1 in which Transbond XT was used as adhesive demonstrated significantly the highest microbial count of S.mutans and DC. Photoactivated RF-doped HANS in 1% and 0.5 wt% Riboflavin alone in orthodontic adhesive for metallic bracket bonding improved micro tensile bond strength, ML, DC, and antibacterial scores. RESEARCH HIGHLIGHTS: The highest μTBS and lowest ML were observed in Group 2 experimental Transbond XT 0.5 wt% RF only. The lowest μTBS, highest ML, and lowest DC was seen in Group 5 experimental Transbond XT 0.5 wt% RF-doped 10% HA-NS. Samples in Group 1 in which Transbond XT was used as adhesive demonstrated significantly the highest microbial count of S.mutans and DC.

Microstructure, mechanical and tribological characteristics of AZ91D-HAp-TiB2 hybrid nanocomposites synthesized through the stir casting route

The aim of this study is to develop a novel magnesium-based nanohybrid composite for potential orthopaedic bioimplant applications. The hybrid nanocomposites were fabricated with AZ91D magnesium alloy as the matrix and hydroxyapatite (HAp) and TiB2 nanoparticles as reinforcements, through the stir casting route. The nanocomposites were synthesized with a fixed concentration of HAp (5 wt%) and different concentrations of TiB2 (2, 4 and 6 wt%). The microstructure of the fabricated composites revealed that the grains are significantly refined with the addition of nanoparticles. The AZ91D-5wt%HAp-2wt%TiB2 hybrid nanocomposite is observed with relatively low porosity, without significant agglomeration of the reinforcement particles, and exhibited the highest tensile and compressive strength with considerably higher ductility than the base AZ91D alloy and the nanocomposites with 4 and 6 wt% TiB2 (about 21% and 34% improvement in compressive and tensile strengths, respectively, compared to the AZ91D alloy). The refinement of grains due to the addition of nanoreinforcements and the alleviation of micro-strain up to a certain extent due to the presence of HAp nanoparticles together with the negligible porosity and agglomeration are the major reasons for the superior strength and ductility. The wear test results showed that the nanocomposite with 2 wt% TiB2 has superior tribological properties. The studies revealed that the AZ91D-5 wt% HAp-2 wt% TiB2 hybrid nanocomposite is a potential material for temporary orthopaedic bioimplants due to its superior strength, ductility, and tribological properties together with the possible enhanced biocompatibility and corrosion resistance due to the presence of HAp particles.

Toward the Production of Hydroxyapatite/Poly(Ether-Ether-Ketone) (PEEK) Biocomposites: Exploring the Physicochemical, Mechanical, Cytotoxic and Antimicrobial Properties.

The development of hydroxyapatite (HAp) and polyether ether ketone (PEEK) biocomposites has been extensively studied for bone repair applications due to the synergistic properties of the involved materials. In this study, we aimed to develop HAp/PEEK biocomposites using high-energy ball milling, with HAp concentrations (20%, 40%, and 60% w/v) in PEEK, to evaluate their physicochemical, mechanical, cytotoxicity, and antimicrobial properties for potential applications in Tissue Engineering (TE). The biocomposites were characterized by structure, morphology, apparent porosity, diametral compression strength, cytotoxicity, and antimicrobial activity. The study results demonstrated that the HAp/PEEK biocomposites were successfully synthesized. The C2 biocomposite, containing 40% HAp, stood out due to the optimal distribution of HAp particles in the PEEK matrix, resulting in higher compression strength (246 MPa) and a homogeneous microstructure. It exhibited antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, with no cytotoxicity observed. These properties make the C2 biocomposite promising for regenerative medicine applications, combining mechanical strength, bioactivity, and biocompatibility.