Nano Hydroxyapatite Research Articles

Remineralizing Potential of Natural Nano-Hydroxyapatite Obtained from Epinephelus chlorostigma in Artificially Induced Early Enamel Lesion: An In Vitro Study.

Dental caries is a common problem in adolescents, leading to permanent loss of teeth or cavitation. Caries is a continuous process wherein demineralization and remineralization occur regularly. Hydroxyapatite (HA) is one of the most biocompatible and bioactive materials, as it closely resembles the mineral composition of teeth. The present study deals with isolating hydroxyapatite from fish bone (Epinephelus chlorostigma) by alkaline hydrolysis and thermal calcination. The isolated nano HA was characterized using FT-IR, XRD, TGA, FE-SEM-EDX, and HR-TEM analysis. The nano HA isolated by alkaline hydrolysis is nontoxic, and the cells are viable. The isolated HA enhances the proliferation of L929 cells. The remineralization potential of the extracted nano HA was evaluated in healthy premolars by DIAGNOdent/laser fluorescence quantification, surface microhardness test, and SEM-EDX analysis. Surface morphological observations in SEM and EDX analyses show that thermally calcined HA and alkali-treated HA can induce mineralization and deposit minerals. Therefore, HA obtained from Epinephelus chlorostigma could be a potential biomaterial for treating early caries.

Application of bone morphogenetic protein 2 derived peptide loaded onto nano hydroxyapatite for periodontal bone regeneration

To explore the feasibility of utilizing a nano drug delivery system for the promotion of periodontal bone regeneration, we constructed a hydroxyapatite-bone morphogenetic protein-2 (HA-BMP-2) nanocomposite. Through characterization by X-ray diffraction and Fourier transform infrared spectroscopy, the synthesized nanocomposite was confirmed to be HA, and nano HA (nHA) could prolong the half-life of BMP-2 by 10 times. In the cell test, we found that compared with nHA, nHA-BMP-2 improved the activity and migration of human periodontal ligament stem cells (HPLSCs) to promote the reconstruction of bone defects. Moreover, nHA-BMP-2 could improve the mineralization of HPLSCs, including increased levels of alkaline phosphatase, collagen I, and osteocalcin, thus enhancing osteogenesis. In the animal experiments, nHA-BPM-2 was further confirmed to effectively improve the area of new bone formation, bone density, bone volume percentage, and trabecular number in periodontal bone defect areas and reduce the repair time. Therefore, nHA-BMP-2 shows great potential for periodontal bone regeneration.

Effect of Smoke Exposure on Gene Expression in Bone Healing around Implants Coated with Nanohydroxyapatite.

This study evaluated the effect of smoke exposure on the expression of genes related to bone metabolism in implants coated with nanohydroxyapatite (NHA). A total of 36 rats were exposed to cigarette smoke for 60 days. The animals were allocated into three groups: machined implants (MAC), dual acid-etched implants (DAE), and NHA-coated implants (NHA). Implants were installed in the left tibia of the rats after 30 days of smoke exposure. The implants were retrieved 7 and 30 days after implantation, and the adjacent bone analyzed using a real-time polymerase chain reaction for gene expression of alkaline phosphatase (ALP), osteopontin (OPN), receptor activator of the nuclear factor kappa ligand (RANKL), osteoprotegerin (OPG), the RANKL/OPG ratio, osteocalcin (OCN) and runt-related transcription factor 2 (Runx2). After 7 days, Runx2, OPN and OPG expression demonstrated significantly higher levels for the NHA surface treatment relative to DAE and MAC surfaces. NHA presented the lowest RANKL and RANKL/OPG levels. After 30 days, NHA-coated implants showed significantly higher levels of Runx2, ALP, OPN, OPG, OC, RANKL and RANKL/OPG relative to DAE and MAC implants. The results indicated a greater osteogenic and high osteoclastic activity around NHA implants, in comparison to DAE and MAC implants.

Evaluation of Human Osteoblasts on NIPS Micro-Patterned PCL Carriers Containing Nanohydroxyapatite and Reduced Graphene Oxide Using PSµM.

The content and surface topology of tissue engineering scaffolds are two important parameters in regulating the cell behavior. In this study, a phase separation micromolding (PSµM) method was implemented to develop micro-groove-imprinted poly(ε-caprolactone) (PCL)–nano hydroxyapatite (nHAp)–reduced graphene oxide (rGO) ternary blend constructs. Physical and chemical characterizations of cell-devoid constructs were performed by FTIR, XRD, TGA, DSC, porosity, swelling, wettability analysis, tensile and compression mechanical tests. The in vitro biological performance of human osteoblasts cultured on micro-patterned blend constructs was evaluated by MTT and alamarBlue viability assays. The findings revealed that nHAp and rGO significantly promote cell viability and proliferation, while the micro-pattern determines the direction of cell migration. Alkaline phosphatase and Ca2+ analyses were carried out to determine the osteogenic properties of cell-laden constructs. This study describes a simple method to generate topologically modified ternary blend PCL/nHAp/rGO constructs using the PSµM method, which contributes to cell proliferation and migration, which is particularly important in regenerative medicine.

Microbial biomineralization of hydroxyapatite nanocrystals using Bacillus tequilensis

In this research, biomimetic deposition of “bone-like” apatite by novel Gram-positive bacterium Bacillus tequilensis was investigated. Hydroxyapatite (HA) was produced by Bacillus tequilensis using defined biomineralization media and dried. Calcination was carried out at different temperatures (100 °C–900 °C) and HA nanopowder was analysed for its structural phase composition, crystallinity, crystallite size and functional groups. X-ray diffractometry (XRD) indicated that increasing temperatures increased the crystallinity of HA nanocrystals. The presence of carbonate groups was evidenced by Fourier transform infrared (FTIR) spectrum and the purity of synthesized apatite nanocrystals was validated by absence of secondary peaks in XRD studies. Scanning electron microscopy (SEM) images depicted those uniform spherical agglomerates of HA comprised of nanosized crystallites. Transmission electron microscope (TEM) results identified needle-like crystal morphologies with average dimensions of 30–60 nm length and 3–10 nm width. Rich trace ion deposition was illustrated by energy dispersive x-ray spectroscopy (EDS) and quantified using inductively coupled plasma optical emission spectrometer (ICP-OES). Overall, microbial biomineralization by Bacillus tequilensis produced nanocrystals of HA that mimicked “bone-like apatite” as evidenced by pure phase, B-type carbonated form, poor crystallinity and trace amounts of vital elements (Mg, Na, K, Zn, Sr, Cl). Moreover, in vitro cytotoxicity studies revealed more than 80% cell viability highlighting the biocompatible nature of synthesized nano HA. Thereby, Bacillus tequilensis biomineralized nano HA reflects as a suitable candidate for applications in biomedicine addressing bone injuries and aiding regeneration.

Preparation and properties of nano silica-based bioactive glass/apatite/sodium alginate composite hydrogel

In this paper, given the lack of osteogenic activity of sodium alginate (SA) hydrogel and to simulate the composition of natural bone, ionic-crosslinking NBG/n-HA/SA hydrogel scaffolds were prepared by using nano bioactive glass (NBG) and nano hydroxyapatite (n-HA) with high bioactivity as composite calcium sources and reinforcement phases, and D-gluconic acid δ-lactone (GDL) as the coagulant. The results showed that the mixture of the precursor forming the network had good injectability and plasticity. When the dosage of GDL was 0.75 g, the gelling time of the composite hydrogel could be regulated within 4–8 min, and the hydrogel had high compressive strength (170–220 kPa), as well. When the mass ratio of calcium source to SA was 1:1, the crosslinking network was relatively uniform with a considerable number of large pores around 40 μm in the structure. In the immersion experiment in vitro, it was found that the composite hydrogel could promote the deposition of bone-like apatite on the material's surface. Meanwhile, the cell experiments in vitro verified that the NBG/n-HA/SA composite hydrogel had good cytocompatibility without cytotoxicity. Moreover, the composite hydrogel could enhance the activity of ALP of mouse bone marrow mesenchymal stem cells, and thus, it had good osteogenic activity.

Electrospun polymer nanocomposite membrane as a promising seed coat for controlled release of agrichemicals and improved germination: Towards a better agricultural prospect

This work was an attempt to boost crop productivity using biocompatible electrospun polycaprolactone nanofiber seed coating on Zea Mays seeds with incorporation of synthesized nano hydroxyapatite (fertilizer high in phosphorus) and zinc oxide nanoparticles (micronutrients). The structure, morphology, and physical characteristics of the fabricated fibres were studied. A regulated release of nutrients from the fibre scaffolds was seen in the pH, conductivity measurements and metal release study. While in storage the seed is protected by the electrospun porous polymer nanofibrous membrane layer, which also enables water and gas exchange and enhances the seed's ability to sprout. Early stages of seed germination are improved by the controlled rate of water absorption in polymer nanofibers covered seeds, as seen by studies of swelling and imbibition. According to statistical analysis, the presence of nutrients in the area around the seedling had a substantial impact on the stand establishment and germination percentage.

Nanocomposite based drug delivery for periodontal disease

Periodontal disease is the term used to describe some pathological conditions characterized by degeneration and inflammation of gums, periodontal ligaments, alveolar bone, and dental cementum. Periodontal disease involves destruction of alveolar bone around the teeth leading to defects or rather loss of the tooth if left untreated. This condition is caused by a chronic, mixed infection of Gram-negative and Gram-positive bacteria. Chlorhexidine (CHX) gluconate is an antiseptic, antifungal and bactericidal agent. CHX inhibits plaque formation by binding to anionic salivary glycoproteins and bacteria. Nano Hydroxyapatite (nHAP) is calcium phosphate in morphology and composition like the human hard tissues. Delivery of medications directly into the periodontal pockets alters the inflammatory response and reduces the pathogenic microbiota, an aspect which has attracted great interes. Result: The CHX Nanocomposites were non-toxic to human cells and promoted cell adhesion, proliferation, and spreading. The CHX Nanocomposites were found to be satisfactory in all respects, and CHX encapsulated in nanocomposites may be attractive candidates for the treatment of periodontal disease.

Estradiol and zinc-doped nano hydroxyapatite as therapeutic agents in the prevention of osteoporosis; oxidative stress status, inflammation, bone turnover, bone mineral density, and histological alterations in ovariectomized rats.

Osteoporosis (OP) is a serious health problem, and the most popular therapeutic strategy for OP is hormone replacement (estrogen); however, it increases the risk of reproductive cancers. Hydroxyapatite (HA) nanoparticles have a similar chemical structure to the bone mineral component and can be used as a new remedy for OP. This study was designed to investigate the osteoporosis-protective potential of nano zinc hydroxyapatite (ZnHA-NPs) and/or estradiol (E2) combined therapy. A total of 35 adult female rats were assigned into five groups (n = 7): 1) control group; 2) ovariectomized group (OVX); 3) OVX received oral estradiol replacement therapy (OVX/E2); 4) OVX received ZnHA replacement therapy (OVX/ZnHA); and 5) OVX received both estradiol and ZnHA-NPs combined therapy (OVX/E2+ZnHA). After 3 months of treatment, serum bone markers and estrogen level, oxidative/antioxidant, and inflammatory cytokines were determined. Additionally, femoral expression of estrogen receptors alpha and beta (ESR1; ESR2), receptor activator of nuclear factor-kappa B (RANKL) ligand, osteoprotegerin (OPG), bone mineral density (BMD), histological alterations, and immunohistochemical expression of vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) were assessed. ALP, PINP, Ca, and P concentrations improved significantly (p < 0.05) in all treatment groups, especially in the OVX/E + ZnHA group. MDA and NO were higher in OVX rats, while SOD activity and GSH were lower (p < 0.05). E2 alone or with ZnHA-NPs restored the estimated antioxidant molecules and cytokines toward normal levels in OVX rats (p < 0.05). On the other hand, E2 and ZnHA increased OPG and OC expression in femurs while decreasing ESR1, ESR2, and NF-kB expression (p < 0.05). The combination treatment was superior in the restoration of normal femoral histoarchitecture and both cortical and trabecular BMD (p < 0.05). Overall, the combined therapy of OVX/E2+ZnHA was more effective than the individual treatments in attenuating excessive bone turnover and preventing osteoporosis.

The effect of metal rate on the gamma shielding parameters of hydroxyapatite at medical treatment energies

The hydroxyapatite (HAp) is a kind of biomaterial which is used for bone treatment applications. We have scrutinized the gamma attenuation parameters such as such as the effective atomic number (Zeff), electron density (Nel), mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half value layer (HVL), tenth value layer (TVL) and mean free path (MFP) for only single liquid gamma source and a narrow beam geometry for the energy (medical treatment energy) ranging from 778 keV to 1408 keV (Eu-152) for the animal bone, iron, cobalt, copper, and zinc decorated Nano hydroxyapatite (nFeHAp, nCoHAp, nCuHAp, and nZnHAp) artificial bone powders. The gamma-rays were counted with using Ultra Low Energy Germanium detection system with a resolution 150 eV at 5,95 keV and a high purity germanium detector with a resolution of 1.85 keV at 1.33 MeV experimentally. The gamma ray attenuation parameters are calculated for the metal doped hydroxyapatite and compare with the animal bone. The results were compared with the output XCOM NIST data. While the mass absorption coefficient values for animal bone range from 0.08 to 0.05 at current energy levels, the values for metal-added artificial bone powders range from 0.07 to 0.05. While the linear absorption coefficient values for existing energy values for animal bone range from 0.04 to 0.02, they range from 0.03 to 0.02 for metal-added artificial bone powders. Mean free path values for real bone range from 24 to 36 at current energies, while half value layer values range from 16 to 25 and tenth value layer values range from 56 to 83. For metal-doped artificial bone powders, these parameters range from 26 to 35, 18 to 24, and 61 to 80, respectively. The results points that, the data of the gamma ray attenuation parameters are very close to the value of the animal bone due to the removal of calcium atoms from the structure when metal is added.

A study on the development of scaffold fabrication using citric acid polyester – nanohydroxyapatite composite

ABSTRACT. Nano hydroxyapatite (n-HAp) and its composites have shown a great development in the field of tissue regeneration and in controlled drug delivery due to its good biocompatibility and bioactivity behavior. Furthermore, HAp-based nanocomposites enhance mechanical properties. These synthetic HAp nanocomposites can also be tailored to fabricate scaffold with controlled porosity which facilitate the growth of the cell in the field of tissue engineering. In this paper, we focus on the synthesis of nano hydroxyapatite (n-HAp) by sol-gel method. The synthesized nano powders were calcined at 500 oC and characterized by FT-IR, XRD and TEM. We have also described the synthesis of citric acid-based polyester by melt polycondensation method without adding catalyst. The monomers used were citric acid, 1,6-hexane diol and sebacic acid. The corresponding synthesized n-HAp/polyester composite have potential application in soft tissue engineering. The structures of polyester and its nanocomposite were studied by FT-IR and 1H NMR spectral studies. The thermal and mechanical properties of polyester, composites and cytotoxicity activity (MTT assay) using vero cells were also studied. Porous scaffold of the nano HAp/Polyester was fabricated by solvent-casting particulate leaching technique which is useful in the development of tissue engineering applications. SEM and TEM studies were carried out for nano HAp, polyester, composites and scaffold.&#x0D; &#x0D; KEY WORDS: Cytotoxicity, Polycondensation, Sol-gel, Solvent-casting, Tissue engineering&#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(4), 923-934. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i4.17

Green Template-Mediated Synthesis of Biowaste Nano-Hydroxyapatite: A Systematic Literature Review.

Hydroxyapatite (HA) is a well-known calcium phosphate ingredient comparable to human bone tissue. HA has exciting applications in many fields, especially biomedical applications, such as drug delivery, osteogenesis, and dental implants. Unfortunately, hydroxyapatite-based nanomaterials are synthesized by conventional methods using reagents that are not environmentally friendly and are expensive. Therefore, extensive efforts have been made to establish a simple, efficient, and green method to form nano-hydroxyapatite (NHA) biofunctional materials with significant biocompatibility, bioactivity, and mechanical strength. Several types of biowaste have proven to be a source of calcium in forming HA, including using chicken eggshells, fish bones, and beef bones. This systematic literature review discusses the possibility of replacing synthetic chemical reagents, synthetic pathways, and toxic capping agents with a green template to synthesize NHA. This review also shed insight on the simple green manufacture of NHA with controlled shape and size.

Synthesis of nano hydroxyapatite from Hypopthalmichthys molitrix (silver carp) bone waste by two different methods: a comparative biophysical and in vitro evaluation on osteoblast MG63 cell lines.

More than a thousand tonnes of fish bone wastes can be transformed into biomedical products annually. Alkaline hydrolysis and thermal calcification were used to create nanosized hydroxyapatite (HAp) crystals from Silver carp bone wastes. Biophysical tests were used to determine the nano size and chemical composition of synthesised hydroxyapatite. Alkaline hydrolysis hydroxyapatite (AH-HAp) was 58.3nm, while Thermal calcination hydroxyapatite (TC-HAp) was 64.3nm in size, confirmed by Atomic Force Microscopy. Energy Dispersive X-ray Analysis studies showed Ca/P (Calcium phosphate) ratio of AH-HAp to be 1.65, whereas TC-HAp as 1.45, confirming AH-HAp to be organically rich along with a similar Ca/P ratio as natural HAp. Fourier Transform Infrared Spectroscopy spectra indicated HAp formation from both procedures, however AH-HAp had superior crystallinity than TC-HAp confirmed from X-Ray Diffraction spectra. MG63 osteoblast cell lines showed 91% cell viability in cytotoxicity studies and 70.1% proliferation efficiency in Alkaline Phosphatase assay, which was higher than TC-HAp. The present study shows that HAp produced via alkaline hydrolysis has better biocompatibility which enhances its applicability as a biomaterial, than HAp synthesized through thermal calcination, which tends to incinerate organic moieties.

Evaluation of Bone Response to a Nano HA Implant Surface on Sinus Lifting Procedures: Study in Rabbits.

The aim of this study was to evaluate the bone response to two different implant surfaces on sinus lift procedures in rabbits. Bilateral sinus lifting with inorganic bovine bone associated with collagen membrane and immediate implantation were performed in 16 rabbits. Custom mini-implants were randomly installed in the prepared sites: one side received a double acid-etched (DAE) surface and the other a nano-hydroxyapatite (NHA) surface. The animals were euthanized 30 and 60 days after surgery, and biopsies were collected for microtomographic and histomorphometric analysis. After 30 days, no intra- and inter-group statistical differences were observed in microtomographic analysis, while at 60 days, bone analysis showed statistically significant differences between groups (p < 0.05) for all the evaluated parameters. Histomorphometric analysis showed, after 30 days, mean % of Bone-to-Implant Contact (BIC) for DAE and NHA of 31.70 ± 10.42% vs. 40.60 ± 10.22% (p > 0.05), respectively; for % of Bone Area Fraction Occupancy (BAFO), mean values were 45.43 ± 3.597% for DAE and 57.04 ± 5.537% for NHA (p < 0.05). After 60 days, mean %BIC and %BAFO for DAE and NHA implants were statistically significant (p < 0.05). The NHA surface showed superior biological features compared to the DAE treatment, promoting higher bone formation around the implants in an experimental model of bone repair in a grafted area.

Comparative evaluation of remineralizing efficacy of silver containing fluoride, nano hydroxyapatite and self assembling peptide on early enamel carious lesions under atomic force microscope

Aim: To evaluate and compare the efficacy of 3 different materials on remineralization of early enamel carious lesions. Materials and Methods:80 maxillary single rooted premolars were divided into four groups(n=20). Group 1: Control,Group 2 : Silver diamine fluoride ,Group 3 : Nano-hydroxyapatite and Group 4: Self assembling peptide. Each group except control group were subdivided into two subgroups. All the materials were demineralized in demineralizing solution for 96 hours, which was daily renewed after 24 hours until uniform early carious lesion were formed. After the formation of lesions, half of specimens from each tested subgroups had the material applied and the half of the specimens didn’t. All the specimens were immersed together in 20 mL of artificial saliva at 37ċ for 24 h. After 24 hours experimental materials were rubbed off using cotton pellate socked in acetone. All the specimens were then washed with distilled water and again immersed in fresh artificial saliva for 48 hours at 37ċ in an incubator. Saliva was exchanged after 24 hours with fresh saliva. The pair of negative control group was only immersed in artificial saliva for 24 and 48 hours continuously and saliva was not exchanged during this period.

Exploring MgO/HA ceramic nano-composites for biodegradable implants: Exploring biological properties and micromechanics

The release of Mg ions from Mg-based implants during biodegradation can promote bone repair through osteoblast migration. However, the high pH values (alkaline stresses) associated with this process can be harmful for osteoblasts. Therefore, surface modifications are required which allow to adjust the Mg ion concentration within a tolerable range. The present work investigates the effect of anodizing of magnesium/hydroxyapatite metal matrix nano composites (Mg/HA-ncomposites) on micromechanical behavior and on biological properties. The results will be implemented into a design strategy for improved Mg/HA-ncomposites. The HIPed Mg/HA-ncomposites with varied content of nano hydroxyapatite (n-HA) particles (0, 0.75, 1.8, and 3 wt%) were anodized in a 6 M KOH solution at 1.50 V and 50 °C for 2 h to develop magnesium oxide/hydroxyapatite surface ceramic matrix nano-composite (MgO/HA-ncomposite). The specimens were evaluated by immersing the materials into simulated body fluid (SBF), seeding of human mesenchymal stem cells on the surfaces, and performing nano-indentation and nano-scratch tests. The results show that the uniform distribution of 1.8 wt% n-HA particles in the MgO converted layer strengthens its adhesion as compared to the other types of MgO/HA-ncomposites. Furthermore, the cell spreading of human mesenchymal stem cells on the composite of 1.8 wt% n-HA improves after the anodizing process and after a one-day cell culture. In summary, the present combined micromechanical and biological study has shown that the MgO/HA-ncomposite of 1.8 wt% n-HA represents a promising biomaterial for bio-absorbable bone implants and that it outperforms pure Mg-surfaces.

Comparative evaluation of remineralizing efficacy of silver containing fluoride, nano hydroxyapatite and self assembling peptide on early enamel carious lesions under atomic force microscope

Aim: To evaluate and compare the efficacy of 3 different materials on remineralization of early enamel carious lesions. Materials and Methods:80 maxillary single rooted premolars were divided into four groups(n=20). Group 1: Control,Group 2 : Silver diamine fluoride ,Group 3 : Nano-hydroxyapatite and Group 4: Self assembling peptide. Each group except control group were subdivided into two subgroups. All the materials were demineralized in demineralizing solution for 96 hours, which was daily renewed after 24 hours until uniform early carious lesion were formed. After the formation of lesions, half of specimens from each tested subgroups had the material applied and the half of the specimens didn’t. All the specimens were immersed together in 20 mL of artificial saliva at 37ċ for 24 h. After 24 hours experimental materials were rubbed off using cotton pellate socked in acetone. All the specimens were then washed with distilled water and again immersed in fresh artificial saliva for 48 hours at 37ċ in an incubator. Saliva was exchanged after 24 hours with fresh saliva. The pair of negative control group was only immersed in artificial saliva for 24 and 48 hours continuously and saliva was not exchanged during this period.

Immunology and bioinformatics analysis of injectable organic/inorganic microfluidic microspheres for promoting bone repair

Organic/inorganic composites have advantages in promoting bone repair; however, early changes in the local immune response after material implantation and the mechanisms that affect the late osteogenesis have not been revealed systematically. Herein, we prepared injectable composite poly (l-lactic acid)/nano hydroxyapatite (PLLA/nHA) porous microspheres (MS@SL@nHA) using a microfluidic technology to explore the changes in the osteo-immune microenvironment and potential mechanisms using immunology and bioinformatics. Immunological analysis revealed that macrophages (Mφ) phagocytosed the nHA released from the composite microspheres, increased the proportion of M2 Mφ, regulated the early inflammatory response, exerted strong paracrine effects, and improved the osteo-immune microenvironment. Bioinformatics analysis showed that the signal transduction and adhesion ability were enhanced after Mφ activation, the inflammatory signaling pathways were inhibited, regulating the polarization direction, and the expression of cell growth factors was up-regulated to promote late osteogenesis. In vivo studies demonstrated that the composite microspheres effectively regulated Mφ polarization, and the paracrine secreted growth factors created a microsphere-centered osteogenesis pattern at the defect site. In conclusion, we successfully prepared injectable composite PLLA/nHA porous microspheres and systematically explored the osteogenesis-related mechanisms using immunological and bioinformatics analysis to provide theoretical evidence for bone repair materials that contribute to bone differentiation.

Protective effects of resveratrol against genotoxicity induced by nano and bulk hydroxyapatite in Drosophila melanogaster

ABSTRACT Hydroxyapatite (HAp) is a naturally occurring calcium phosphate mineral predominantly used for its biocompatibility in a number of areas such as bone grafting, prosthesis coating in dentistry, and targeted drug delivery. Since the nano form of HAp (nHAp) has gained popularity attributed to a re-mineralizing effect in dental repair procedures, concerns have been raised over safety and biocompatibility of these nanoparticles (NP). This study, therefore, aimed to (1) investigate mechanisms of potential genotoxicity and enhanced generation of reactive oxygen species (ROS) initiated by bulk and nano forms of HAp and (2) test in vivo whether resveratrol, a type of natural phenol, might mitigate the extent of potential DNA damage. The size of nHAp was determined to be 192.13 ± 9.91 nm after dispersion using transmission electron microscopy (TEM). Drosophila melanogaster was employed as a model organism to determine the genotoxic potential and adverse effects of HAp by use of (comet assay), mutagenic and recombinogenic activity (wing spot test), and ROS-mediated damage. Drosophila wing-spot tests demonstrated that exposure to nontoxic bulk and nHAp concentrations (1, 2.5, 5 or 10 mM) produced no significant recombination effects or mutagenicity. However, bulk and nHAp at certain doses (2.5, 5 or 10 mM) induced genotoxicity in hemocytes and enhanced ROS production. Resveratrol was found to ameliorate the genotoxic effects induced by bulk HAp and nHAp in comet assay. Data demonstrate that treatment with nano and bulk Hap-induced DNA damage and increased ROS generation D. melanogaster which was alleviated by treatment with resveratrol.

The effect of nano and micro hydroxyapatite powder additives on surface integrity in electrical discharge machining of Ti6Al4V alloy

The current study investigates the Hydroxyapatite (HA) deposition phenomena to the modified surface of titanium (Ti) alloy in Hydroxyapatite Powder Mixed Electrical Discharge Machining (HA-PMEDM). Nano and micro size HA powders were mixed into the dielectric liquid and tested for a wide range of pulse currents and pulse-on durations. The change of surface and subsurface properties were evaluated in terms of Surface Roughness (SR), Optical and Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), and X-ray Diffraction (XRD). Finally, in-depth microhardness measurements were carried out to reveal the microhardness profile of the analyzed samples. As a result of the analysis, the effects of the process parameters on the surface roughness, surface topography, and powder deposition to the surface were evaluated. The current results reveal nano and micro powder additives deposited to the surface at different parameters during EDM. The highest rate of HA deposition to the machined surface observed when using 22 A pulse current and 100 μs pulse-on duration in micro additive dielectric liquid. Resolidified Layer (RL) and Heat Affected Layer (HAL) thicknesses vary between 5 and 50 μm, 8–83 μm respectively. Generaly, layer thicknesses in nano HA-PMEDM are higher than the micro HA-PMEDM. The hardness values of the samples machined in nano HA-PMEDM reach 1800 HV on RL. The current results support the use of HA-PMEDM to obtain functional surfaces for medical applications.