Comparative study of particle size analysis of hydroxyapatite-based nanomaterials

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm³ was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

Nano Hydroxyapatite for Biomedical Applications Derived from Chemical and Natural Sources by Simple Precipitation Method

In the past, bone fractures due to accidents were rectified by surgery and reconstruction of bone structure. In recent times, researchers have been made to find a solution by producing alternate biomaterials. Hydroxyapatite (HAp) is one of the most important bioactive materials used as a substitute for human hard tissue because of its composition being very similar to human bones and teeth. A study has proved that HAp has been used for bone regeneration in clinical trials in the mid-1980. HAp has been used as implant coatings and graft materials and also used as granules, cement, and pastes for bone regenerative applications. HAp coatings on bioimplants improved biocompatibility, bioactivity, and biological fixation. Moreover, some of the deposition methods can be employed to increase the cellular responses of bone regeneration such as sputtering, spraying, electrodeposition, and pulsed layer deposition. The researcher has prepared hydroxyapatite from chemical and natural sources. The surface area and intrinsic properties of the HAp play a vital role in bone-related applications. This can be achieved by synthesizing the HAp from natural sources rather than synthetic materials. The HAp obtained from the chemical source is not fulfilling the requirements of the natural bone. A variety of biowaste materials such as eggshell, crab shell, snail shell, bovine bone, fishbone, and fish scales are available in nature and can be converted to useful calcium source for HAp. The present study is to produce the HAp from biowaste materials like eggshell and chemical sources using the wet precipitation method. The synthesized HAp is coated on the Ti6Al4V alloy using the electrodeposition method, and it is immersed in SBF solution at 37 °C for corrosion testing. The coated samples are investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), electrochemical study, field emission scanning electron icroscopy (FESEM), energy dispersive X-ray analysis (EDAX), AFM, and antibacterial activity with two different microorganisms. FTIR and XRD confirm the functional groups and crystallinity of the HAp. The good antibacterial activity of the HAp is observed against two bacterial strains. The corrosion studies reveal that the HAp derived from a natural source is eco-friendly and nontoxic and has excellent corrosion resistivity and cell adhesion properties. A strong bond is formed between the naturally derived HAp with bone tissue which is involved in the bio-resorption process and does not pose any side effect to the human body compared to synthetically derived HAp. In addition, the biowaste materials are converted to useful biomaterials and can reduce environmental pollution.

Mechanical Properties of Differently Nanostructured and High-Pressure Compressed Hydroxyapatite-Based Materials for Bone Tissue Regeneration

Hydroxyapatite (HAp) has long been considered the gold standard in the biomedical field, considering its composition and close resemblance to human bone. However, the brittle nature of hydroxyapatite (HAp) biomaterial, constrained by its low fracture toughness (of up to 1.2 vs. 2–12 MPa m1/2 of human bone), remains one of the significant factors impairing its use in bone regeneration. In the present study, HAp nanoparticles synthesized by the solid-state (SHAp) and sonochemical (EHAp) approaches using eggshell-derived calcium hydroxide and ammonium dihydrogen orthophosphate as precursors are compared with those synthesized using commercially available calcium hydroxide and ammonium dihydrogen orthophosphate as precursors (CHAp) employing sonochemical method. The HAp samples were then compressed into compact materials using a uniaxial high-pressure compression technique at a preoptimized load and subsequently characterized for mechanical properties using the Vickers indentation method and compressive strength testing. The analysis revealed that the material with smaller particle size (30–40 nm) and crystalline nature (EHAp and CHAp) resulted in mechanically robust materials (σm = 54.53 MPa and 47.72 MPa) with high elastic modulus (E = 4011.1 MPa and 2750.25 MPa) and density/hardness-dependent fracture toughness (σf = 4.34 MPa m1/2and 6.57 MPa m1/2) than SHAp (σm =28.40 MPa, E = 2116.75 MPa, σf = 5.39 MPa m1/2). The CHAp material was found to be the most suitable for applications in bone regeneration.

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.

Biomaterial-Based Nanocomposite for Osteogenic Repurposing of Doxycycline

Background

Besides its antimicrobial action, doxycycline (DX) has lately been repurposed as a small-molecule drug for osteogenic purposes. However, osteogenic DX application is impeded by its dose-dependent cytotoxicity. Further, high-dose DX impairs cell differentiation and mineralization.

Purpose

Integrating DX into a biomaterial-based delivery system that can control its release would not only ameliorate its cytotoxic actions but also augment its osteogenic activity. In this work, we managed to engineer novel composite DX–hydroxyapatite–polycaprolactone nanoparticles (DX/HAp/PCL) to modify DX osteogenic potential.

Methods

Employing a 2³-factorial design, we first optimized HApN for surface-area attributes to maximize DX loading. Composite DX/HAp/PCL were then realized using a simple emulsification technique, characterized using various in vitro methods, and evaluated for in vitro osteogenesis.

Results

The developed HApN exhibited a favorable crystalline structure, Ca:P elemental ratio (1.67), mesoporous nature, and large surface area. DX/HAp/PCL achieved the highest reported entrapment efficiency (94.77%±1.23%) of DX in PCL-based particles. The developed composite system achieved controlled release of the water-soluble DX over 24 days. Moreover, the novel composite nanosystem managed to significantly ameliorate DX cytotoxicity on bone-marrow stem cells, as well as enhance its overall proliferation potential. Alkaline phosphatase and mineralization assays revealed superior osteodifferentiation potential of the composite system. Quantification of gene expression demonstrated that while DX solution was able to drive bone-marrow stem cells down the osteogenic lineage into immature osteoblasts after 10-day culture, the innovative composite system allowed maturation of osteodifferentiated cells. To the best of our knowledge, this is the first work to elaborate the impact of DX on the expression of osteogenic genes: RUNX2, OSP, and BSP. Further, the osteogenicity of a DX-loaded particulate-delivery system has not been previously investigated.

Conclusion

Our findings indicate that repurposing low-dose DX in complementary biomaterial-based nanosystems can offer a prominent osteogenic candidate for bone-regeneration purposes.

Hybrid bioactive hydroxyapatite/polycaprolactone nanoparticles for enhanced osteogenesis

Hydroxyapatite nanoparticles (HApN) are largely employed as osteogenic inorganic material. Inorganic/polymeric hybrid nanostructures can provide versatile bioactivity for superior osteogenicity, particularly as nanoparticles. Herein, we present hybrid biomaterial-based hydroxyapatite/polycaprolactone nanoparticles (HAp/PCL NPs) realized using simple preparation techniques to augment HApN osteogenicity. Using wet chemical precipitation, we optimized HApN crystalline properties utilizing a 2³-factorial design. Optimized HApN exhibited typical Ca/P elemental ratio with high reaction yield. Surface area analysis revealed their mesoporous nature and high surface area. Hybrid HAp/PCL NPs prepared using direct emulsification-solvent evaporation maintained HApN crystallinity with no observed chemical interactions. To the best of our knowledge, we are the first to elaborate the biocompatibility and osteogenicity of nanoparticulate hybrid HAp/PCL. Hybrid HAp/PCL NPs outperformed HApN regarding mesenchymal cell proliferation and osteodifferentiation with reduction of possible cytotoxicity. Unlike HApN, hybrid HAp/PCL NPs presented moderate expression of early osteogenic markers, Runx-2 and osteopontin and significantly elevated expression of the late osteogenic marker, bone sialoprotein after 10-day culture. Our results indicate that hybrid bioactive HAp/PCL NPs could offer a more prominent osteogenic potential than plain HApN for bone regenerative applications as a standalone nanoplatform or as part of complex engineered systems.

Thermal Stabilization of Polyoxymethylene by PEG-Functionalized Hydroxyapatite: Examining the Effects of Reduced Formaldehyde Release and Enhanced Bioactivity

Nanostructured hydroxyapatite (HA) functionalized with poly(ethylene glycol) (HA-g-PEG) of different molar mass was used as a thermal stabilizer to prepare polyoxymethylene (POM) composites by a melt processing method. The chemical and crystalline structure of (HA-g-PEG) and POM/HA-g-PEG composites was investigated by means of FTIR and XRD. The thermal properties, degree of crystallinity, and melting behaviour of POM-based composites were analysed with TG, DSC, and TOPEM DSC methods. The tensile strength, Young’s modulus, toughness, and wettability of POM were investigated as well. A preliminary assessment of bioactivity, in vitro chemical stability, and formaldehyde release from POM/HA-g-PEG composites by Schiff’s test was also performed. An SEM/EDX method was used to observe the morphology of POM/HA-g-PEG composites. The results indicate that the addition of 1% HA-g-PEG slightly increases the melting temperature and degree of crystallinity. In small amounts, HA-g-PEG particles probably act as nucleating agents for the POM crystallization process. Incorporation of 5% HA-g-PEG to POM caused a decrease in the crystallinity of the polymer matrix, as a result, some mechanical properties of POM/HA-g-PEG composites also decreased. The thermal stability of POM/HA-g-PEG composites improved significantly from 309°C for unmodified POM to 342°C for POM/10.0% HA-g-PEG 600. The most effective thermal stabilizer was synthesized with the lowest mass-average molar mass PEG. The in vitro bioactivity test confirmed that, as the average molar mass of PEG in HA-g-PEG hybrids increased, POM-based composites indicated higher bioactivity. The in vitro chemical stability analysis results showed that both the POM matrix and the HA-g-PEG additive remain stable during the whole incubation time. Importantly, after seven days of dynamic incubation, no formaldehyde was detected in all filtrates, which is crucial in biomedical applications, among others.

Platinum nanoparticles induce damage to DNA and inhibit DNA replication

Sparsely tested group of platinum nanoparticles (PtNPs) may have a comparable effect as complex platinum compounds. The aim of this study was to observe the effect of PtNPs in in vitro amplification of DNA fragment of phage λ, on the bacterial cultures (Staphylococcus aureus), human foreskin fibroblasts and erythrocytes. In vitro synthesized PtNPs were characterized by dynamic light scattering (PtNPs size range 4.8-11.7 nm), zeta potential measurements (-15 mV at pH 7.4), X-ray fluorescence, UV/vis spectrophotometry and atomic absorption spectrometry. The PtNPs inhibited the DNA replication and affected the secondary structure of DNA at higher concentrations, which was confirmed by polymerase chain reaction, DNA sequencing and DNA denaturation experiments. Further, cisplatin (CisPt), as traditional chemotherapy agent, was used in all parallel experiments. Moreover, the encapsulation of PtNPs in liposomes (LipoPtNPs) caused an approximately 2.4x higher of DNA damage in comparison with CisPt, LipoCisPt and PtNPs. The encapsulation of PtNPs in liposomes also increased their antibacterial, cytostatic and cytotoxic effect, which was determined by the method of growth curves on S. aureus and HFF cells. In addition, both the bare and encapsulated PtNPs caused lower oxidative stress (determined by GSH/GSSG ratio) in the human erythrocytes compared to the bare and encapsulated CisPt. CisPt was used in all parallel experiments as traditional chemotherapy agent.

Bio-scaffolds produced from irradiated squid pen and crab chitosan with hydroxyapatite/β-tricalcium phosphate for bone-tissue engineering

In this study, bio-scaffolds have been developed using irradiated chitosan from different sources - squid pen (RS) and crab shell (RC) - with hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) at a chitosan/HA/β-TCP ratio of 50/30/20. The bio-scaffolds were prepared at two different freezing temperature (-20°C and -80°C) followed by lyophilisation. To enhance the mechanical properties, the bio-scaffolds were cross-linked using sodium tripolyphosphate (TPP) followed by lyophilisation. The composition and morphology of the bio-scaffolds were characterized using XRD, SEM, TEM and μ-CT. The pore size of the porous scaffolds ranged from 90 to 220μm and the scaffolds had 70-80% porosity. The scaffolds had a water uptake ratio of more than 10, and a controlled biodegradation in the range of 30-40%. These results suggest that the physical and biological properties of chitosan-based bio-scaffolds can be a promising biomaterial for bone-tissue regeneration.

Development and characterization of hydroxyapatite/β-TCP/chitosan composites for tissue engineering applications

Calcium phosphate ceramics that mimic bone composition provide interesting possibilities for the advancement in bone tissue engineering. The present study reports on a chitosan composite reinforced by hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) obtained from waste mussel shells and cross-linked using tripolyphosphate (TPP). The ratios of the ceramic components in composites were 20/10/70, 30/20/50 and 40/30/30 (HA/β-TCP/CH, w/w %). Biodegradation rate, structural properties and in-vitro degradation of the bone-like composite scaffolds were investigated. The optimum amount of TPP required for composite was 2.5% and glycerol was used as plasticizer at an optimized concentration of 1%. Tripolyphosphate cross-linked chitosan composites were developed by freezing and lyophilisation. The Young's modulus of the scaffolds was increased from 4kPa to 17kPa and the porosity of composites dropped from 85 to 68% by increasing the HA/β-TCP ratio. After 28days in physiological solution, bone-like composite scaffolds with a higher ratio of HA/β-TCP (e.g. 40/30/30) showed about 2% lower biodegradation in comparison to scaffolds with a lower ratio of HA/β-TCP (i.e. 20/10/70). The obtained data suggest that the chitosan based bone-like composites could be potential candidates for biomedical applications.