Hydroxyapatite with magnetic core: Synthesis methods, properties, adsorption and medical applications

Ultra-high capacity and selectivity for uranium fixation by carbon nanosphere supported hydroxyapatite nanorod adsorbent

Uranium (U(VI)) has chemical and radiological toxicity, so the effective treatment of uranium-containing wastewater is crucial for both environmental safety and human health. Here, a carbon nanosphere (CNS) supported hydroxyapatite (HAP) nanorod (HAP/CNS) adsorbent was prepared using a simple glucose-assisted hydrothermal method toeffectively immobilize U(VI). Glucose not only derived CNS, but also facilitated HAP crystallization, prohibited HAP aggregation, and introduced oxygen-containing functional groups (i.e., COOH). The optimized HAP/CNS possessed a fantastic adsorption capability of 3080.3 mg/g for U(VI), nearly three times that of HAP and much higher than many reported HAP-based adsorbents. Notably, HAP/CNS was less affected by coexisting ions (distribution coefficient, Kd, researched 6.0 × 104 mL/g) and humic acid, and maintained good capability for real wastewater. The pseudo-second-order kinetic model and Langmuir isotherm model could better explain U(VI) removal behavior by HAP/CNS. Results showed that HAP/CNS and UO22+ combined to form a new uranium-containing compound, i.e., calcium-uranium mica (Ca(UO2)2(PO4)2·3H2O) via ion exchange and dissolution-precipitation, which should be the main reason for the ultra-high capacity and selectivity of HAP/CNS. Additionally, the hydrophilic oxygen-containing functional groups synergistically facilitated U(VI) fixation through complexation. This work introduces a superior adsorbent for purifying uranium-contaminated wastewater and elucidates its synergetic mechanism in uranium fixation.

The fate of antibiotics during phosphate recovery processes - A critical review

The principles of circular economy encourage the recovery of phosphorus from nutrient-rich waste streams such as animal manure, domestic wastewater, and urine to supplement existing sources of raw phosphorus. However, these waste streams also contain a wide variety of contaminants of emerging concern including antibiotics, and the recovery of phosphorus from these waste streams results in the co-occurrence of antibiotics with the recovered phosphorus products. This paper provides a comprehensive overview of the fate of environmentally relevant antibiotics in three major existing and upcoming phosphorus recovery processes: precipitation-, membrane-, and adsorption-based treatment. In general, the co-occurrence of antibiotics in recovered phosphorus increases with the presence of dissolved organic matter (DOM) and cations due to π-π interaction and cationic bridge formation, respectively. Additionally, antibiotics display pH-based speciation resulting in electrostatic interactions with recovered phosphorus at pH > 7.0. Furthermore, this critical review establishes a new metric, the relative antibiotic-to‑phosphorus (RAP), defined as the ratio of the concentration of antibiotics to phosphorus in recovered phosphorus to that of the phosphorus-rich waste. Precipitation-based methods, particularly struvite, demonstrated the lowest RAP, while the RAP in carbon-based adsorbents was 1.8 × 108 times higher than in membrane-based processes. In reviewing literature on the fate of antibiotics in phosphorus recovery processes, several research needs are also highlighted: the fate of non-tetracycline antibiotics, simultaneous investigation of phosphorus and antibiotic fate in membrane- and adsorption-based methods, treatment methods to mitigate the co-occurrence of antibiotics in recovered phosphorus product, and the release of antibiotics from recovered phosphate products.

Adsorption of Ni(II) from Aqueous Solution by Wheat Straw Modified with Mercaptopropionyl Functional Groups

Mercaptopropionyl wheat straw (MPWS) was prepared as an adsorbent by modifying wheat straw with mercaptopropionyl groups, and the ability of MPWS for the removal of Ni(II) from aqueous solution was examined. The removal of Ni(II) by using MPWS was identified through investigating the impacts of MPWS dosage, adsorption temperature, and adsorption time. Different models for the adsorption isotherm and kinetics were utilized to fit the experimental results and elucidate the mechanism of MPWS for Ni(II). Environmental interference factors, including initial Ni(II) concentration, pH value, inorganic matters, and organic matters in wastewater, were examined to evaluate the antienvironmental disturbance capability of MPWS during Ni(II) adsorption. A removal rate of Ni(II) as high as 99.02% was achieved at pH 6.0 with an adsorption temperature of 30 °C and a contact time of 100 min. The experimental results exhibited excellent alignment with both pseudo-second-order kinetic model, Freundlich isothermal model, Redlich-Peterson model, and Hill model. Furthermore, coexisting substances in the environment could inhibit the adsorption process of Ni(II) by MPWS; however, this inhibition could be mitigated or eliminated by increasing the amount of absorbent MPWS. Overall, MPWS displays remarkable resistance against environmental interference during its application for removing Ni(II) from wastewater.

A review of hydroxyapatite synthesis for heavy metal adsorption assisted by machine learning

Heavy metals (HMs) represent a persistent and significant threat to aquatic ecosystems. Hydroxyapatite (HAp) has emerged as a utilized material in the remediation of environmental HMs, owing to its exceptionally high porosity, expansive surface area, and the presence of three-dimensional ordered channels. An in-depth study of the synthesis strategy of HAp and its adsorption properties can help reduce the cost of remediating HMs in aquatic environments and alleviate the water shortage. In this paper, we reviewed 466 works of literature on the adsorption of heavy metals by HAp based on the Web of Science database between 2013 and 2023 that focused on the adsorption of heavy metals by HAp. We meticulously synthesized the findings related to the synthesis conditions-namely precipitation, hydrothermal, and calcination-as well as the characterization parameters and the adsorption capacity of HAp for heavy metals such as Pb2+, Cd2+, Cu2+, Zn2+, and Ni2+. Synthesizing advanced materials by reducing the number of experiments is essential to accelerate material development. Machine learning (ML) holds significant promise in material discovery and performance enhancement. We have consolidated the qualitative and quantitative relationships between HAp synthesis conditions, characterization parameters, and heavy metal adsorption capacity across previous studies, utilizing both the Statistical Package for Social Sciences (SPSS) and ML techniques. Building on the most recognized heavy metal adsorption mechanisms, we have evaluated the influence of characterization parameters on adsorption performance. We have outlined the optimal synthetic conditions for enhancing the adsorption of Pb2+, Cd2+, Cu2+, Zn2+, and Ni2+ through precipitation, hydrothermal, and calcination methods, offering a practical guide for the targeted synthesis of HAp tailored to specific heavy metal adsorption capacities.

The Role of Nanomaterials in Diagnosis and Targeted Drug Delivery

Nanomaterials have evolved into the most useful resources in all spheres of life. Their small size imparts them with unique properties and they can also be designed and engineered according to the specific need. The use of nanoparticles (NPs) in medicine is particularly quite revolutionary as it has opened new therapeutic avenues to diagnose, treat and manage diseases in an efficient and timely manner. The review article presents the biomedical applications of nanomaterials including bioimaging, magnetic hypothermia and photoablation therapy, with a particular focus on disease diagnosis and targeted drug delivery. Nanobiosensors are highly specific and can be delivered into cells to investigate important biomarkers. They are also used for targeted drug delivery and deliver theranostic agents to specific sites of interest. Other than these factors, the review also explores the role of nano-based drug delivery systems for the management and treatment of nervous system disorders, tuberculosis and orthopaedics. The nano-capsulated drugs can be transported by blood to the targeted site for a sustained release over a prolonged period. Some other applications like their role in invasive surgery, photodynamic therapy and quantum dot imaging have also been explored. Despite that, the safety concerns related to nanomedicine are also pertinent to comprehend as well as the biodistribution of NPs in the body and the mechanistic insight.

Boron-Doped Nano Hydroxyapatite Grafts for Bone Regeneration in Rat Mandibular Defects

The aim of this study was to evaluate the potential effects of boron-doped nano hydroxyapatite grafts on craniofacial bone regeneration in critical bone defects in the mandibular corpus of rats, in terms of scintigraphic and histopathological aspects. Forty Wistar albino rats, with an average weight of 200-220 g, aged 16-18 weeks, and all male, were used in the study. The rats were randomly assigned to five groups, each containing 8 rats, as follows: group C1 (no procedure applied to the mandible), group C2 (surgical defect created in the mandible but no treatment applied), group nHA (nano hydroxyapatite applied to the surgical defect area), group nHA + B1 (nano hydroxyapatite + 1% boron applied to the surgical defect area), and group nHA + B2 (nano hydroxyapatite + 2% boron applied to the surgical defect area). A standard 4 × 4 mm full-thickness transosseous bone defect was created in the mandibular corpus of all rats, except for those in group C1. The bone defect in the rats in group C2 was left to heal naturally. Nano hydroxyapatite (nHA), nano hydroxyapatite + 1% boron, and nano hydroxyapatite + 2% boron were applied to the surgical defect areas of the other three groups, respectively. Bone scintigraphy was performed on all rats on days 0 (following the surgical procedure) and 28 of the experimental period. At the end of the 28th day, the animals were sacrificed, and tissue samples were collected for histological examination. A standard grading system was used to evaluate fracture healing. When the groups were compared in terms of bone healing histopathological scores, a statistically significant difference was observed between group C1 and the other groups (p < 0.005). In the statistical evaluation made according to the histopathological mean scores, the least improvement was observed in group C2. No statistically significant difference was observed between group nHA and group nHA + B1 and group C2 and between group nHA and group nHA + B1 in terms of bone healing scores (p > 0.005). A statistically significant difference was found between group nHA + B2 and group C2 (p = 0.026). Although there was no statistically significant difference in histopathological scores, the mean score closest to group C1 was observed in group nHA + B2. A statistically significant difference was observed between the groups in the scintigraphic evaluation performed on the 28th day of the experimental procedure, and the difference was between group C1 and group nHA + B1 and between group nHA and group nHA + B1 (p = 0.004; p = 0.028, p < 0.005). In the comparison of the values obtained on days 0 and 28 within the group, a statistically significant change was observed in group nHA + B1 and group nHA + B2 (p < 0.005). When the results of the present study were evaluated, it was thought that the boron-doped nHA graft biomaterials may have positive effects on bone healing. Providing a different perspective for the development of an alternative new treatment modality that can be locally applied in the treatment of fractures a serious and common health problem can be interpreted as an important outcome of the present study. We believe that this study will serve as a preliminary study for more comprehensive future studies on this subject.

Composites of hydroxyapatite and their application in adsorption, medicine and as catalysts

Composites of hydroxyapatite, recognized by its peculiar crystal architecture and distinctive attributes showcased the potential in adsorbing heavy metal ions and radioactive elements as well as selected organic substances. In this paper, the intrinsic mechanism of adsorption by composites hydroxyapatite was proved for the first time. Subsequently, selectivity and competitiveness of composites of hydroxyapatite for a variety of environments containing various interferences from cations, anions, and organic molecules are elucidated. Next, composites of hydroxyapatite were further categorized according to their morphological dimensions. Adsorption properties and intrinsic mechanisms were investigated based on different morphologies. It was shown that although composites of hydroxyapatite were characterized by excellent adsorption capacity and cost-effectiveness, their application is often challenging due to inherent fragility and agglomeration, technical problems required for their handling as well as difficulty in recycling. Finally, to address these issues, the paper discusses the tendency of hydroxyapatite composites to adsorb heavy metal ions and radioactive elements as well as the limitations of their applications. Summarizing the limitations and future directions of modification of HAP in the field of heavy metal ions and different substances contamination abatement, the paper provides insightful perspectives for its gradual improvement and rational application.

Nanoparticles and bone microenvironment: a comprehensive review for malignant bone tumor diagnosis and treatment

Malignant bone tumors, which are difficult to treat with current clinical strategies, originate from bone tissues and can be classified into primary and secondary types. Due to the specificity of the bone microenvironment, the results of traditional means of treating bone tumors are often unsatisfactory, so there is an urgent need to develop new treatments for malignant bone tumors. Recently, nanoparticle-based approaches have shown great potential in diagnosis and treatment. Nanoparticles (NPs) have gained significant attention due to their versatility, making them highly suitable for applications in bone tissue engineering, advanced imaging techniques, and targeted drug delivery. For diagnosis, NPs enhance imaging contrast and sensitivity by integrating targeting ligands, which significantly improve the specific recognition and localization of tumor cells for early detection. For treatment, NPs enable targeted drug delivery, increasing drug accumulation at tumor sites while reducing systemic toxicity. In conclusion, understanding bone microenvironment and using the unique properties of NPs holds great promise in improving disease management, enhancing treatment outcomes, and ultimately improving the quality of life for patients with malignant bone tumors. Further research and development will undoubtedly contribute to the advancement of personalized medicine in the field of bone oncology.

Grave-to-cradle dry reforming of plastics via Joule heating

Both plastics and CO2 are waste carbon resources, and their accumulation in nature has led to severe environmental pollution. However, simultaneously converting plastic waste and CO2 into value-added chemicals remains a challenge. Here we demonstrate a catalytic reforming process that converts plastics and CO2 into syngas over an electrified FeCrAl heating wire. The temperature of the electrified heating wire can quickly exceed 800 °C, facilitating the decomposition of polyethylene into gaseous hydrocarbons. The high-temperature heating wire promote the CO2 deoxygenation, resulting in the generation of CO, as well as the dehydrogenation of gaseous hydrocarbons. Significantly, the additional O species from CO2 and the carbon species from hydrocarbons can react to form CO, maintaining the high catalytic activity of the electrified heating wire. This novel approach is of paramount to achieving a circular economy in addressing the ongoing environmental crisis caused by the accumulation of plastic waste and excessive CO2 emissions.

Incorporating mannose-functionalized hydroxyapatite/metal-organic framework into the hyaluronic acid hydrogel film: A potential dual-targeted oral anticancer delivery system

The recent challenge in enhancing the targeted delivery of anticancer drugs to cancer cells is improving the bioavailability and therapeutic efficacy of drug delivery systems while minimizing their systemic side effects. In this study, the MIL-88(Fe) metal-organic framework was synthesized using the in situ method in the presence of hydroxyapatite nanoparticles (HAP) toward the HAP/MIL-88(Fe) (HM) nanocomposite preparation. It was then functionalized with mannose (M) as an anticancer receptor through the Steglich esterification method. Various analyses confirmed the successful synthesis of MHM. For drug release investigation, 5-Fu was loaded into the MHM, which was then coated with a hyaluronic acid (HA) hydrogel film. Characterization analyses verified the structure of the resulting HA/5-Fu-MHM hydrogel film. In vitro drug release experiments showed that the release of 5-Fu drug from HA/5-Fu-MHM could be controlled with pH, reducing its release rate in the acidic environment of the stomach while increasing it in the intestinal environment. Cytotoxicity results of the HA/5-Fu-MHM hydrogel film against HT29 cancer cells showed enhanced cytotoxicity due to the mannose and hyaluronic acid in its structure, which triggers a dual-targeted drug delivery system. The obtained results indicate that the prepared hydrogel films can be a promising bio-platform for colon cancer treatment.

Enhanced mechanical properties and biocompatibility of hydroxyapatite scaffolds by magnesium and titanium oxides for bone tissue applications

Significant attention has been devoted to bioactive implants for bone tissue applications, particularly composite scaffolds based on hydroxyapatite (HaP). This study explores the effects of Magnesium and Titanium oxides on the characteristics of HaP-based composite (HMT) scaffolds. The ceramic nanopowders were synthesized using in situ sol-gel, and then the scaffolds were fabricated by gel-casting technique, followed by heat treatment at 1200 °C. The thermal, microstructural, and structural properties of the samples were investigated by different characterization techniques. It was observed that the formation of the MgTiO3 phase in the composite scaffold was likely the key factor contributing to the improved mechanical properties. Finally, to evaluate bioactivity and biodegradability, scaffolds were immersed in simulated body fluid (SBF) buffer and analyzed by Field Emission Scanning Electron Microscopy (FESEM), and the viability of human fibroblast cells was assessed using the MTT assay. The composite scaffolds containing the MgTiO3 phase showed greater HaP layer formation on the scaffold surface, indicating enhanced biocompatibility.

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Synthesis of novel magnetic hydroxyapatite-biomass nanocomposite for arsenic and fluoride adsorption

A magnetic nanocomposite of hydroxyapatite and biomass (HAp-CM) was synthesized through a combined ultrasonic and hydrothermal method, aiming for efficient adsorption of arsenic (As) and fluoride (F-) from drinking water in natural environments. The characterization of HAp-CM was carried out using TG, FTIR, XRD, SEM, SEM-EDS, and TEM techniques, along with the determination of pHpzc charge. FTIR analysis suggested that coordinating links are the main interactions that allow the formation of the nanocomposite. XRD data indicated that the crystalline structure of the constituent materials remained unaffected during the formation of HAp-CM. SEM-EDS analysis revelated a Ca/P molar ratio of 1.78. Adsorption assays conducted in batches demonstrated that As and F- followed a PSO kinetic model. Furthermore, As adsorption fitting well to the Langmuir model, while F- adsorption could be explained by both Langmuir and Freundlich models. The maximum adsorption capacity of HAp-CM was found to be 5.0 mg g-1 for As and 10.2 mg g-1 for F-. The influence of sorbent dosage, pH, and the presence of coexisting species on adsorption capacity was explored. The pH significantly affected the nanocomposite's efficiency in removing both pollutants. The presence of various coexisting species had different effects on F- removal efficiency, while As adsorption efficiency was generally enhanced, except in the case of PO43-. The competitive adsorption between F- and As on HAp-CM was also examined. The achieved results demonstrate that HAp-CM has great potential for use in a natural environment, particularly in groundwater remediation as a preliminary treatment for water consumption.

Laser-assisted synthesis of nano-hydroxyapatite and functionalization with bone active molecules for bone regeneration

The main goal of bone tissue engineering research is to replace the allogenic and autologous bone graft substitutes that can promote bone repair. Owing to excellent biocompatibility and osteoconductivity, hydroxyapatite is in extensive research and high demand for both medical and non-medical applications. Although various methods have been developed for the synthesis of hydroxyapatite, in the present study we have shown the use of nanosecond laser energy in the wet precipitation method of nano-hydroxyapatite (nHAP) synthesis without using ammonium solution or any other chemicals for pH maintenance. Here, the present study aimed to fabricate the nanohydroxyapatite using a nanosecond laser. The X-ray diffraction and Fourier transform infrared spectroscopy have confirmed the hydroxyapatite formation under laser irradiation in less time without aging. A transmission electron microscopy confirmed the nano size of synthesized nHAP, which is comparable to conventional nHAP. The length and width of the laser-assisted nHAP were found to be in the range of 50-200 nm and 15-20 nm, respectively, at various laser parameters. The crystallite size obtained by Debye Scherrer formulae was found to be in the range of ∼ 16-36 nm. In addition, laser-assisted nHAP based composite cryogel (nanohydroxyapatite/gelatin/collagen I) was synthesized and impregnated with bioactive molecules (bone morphogenic protein and zoledronic acid) that demonstrated significant osteogenic potential both in vitro in cell experiment and in vivo rat muscle pouch model (abdomen and tibia muscles). Dual-energy X-ray analysis, micro-CT, and histological analysis confirmed ectopic bone regeneration. Micro-CT based histomorphometry showed a higher amount (more than 10-fold) of mineralization for animal groups implanted with composite cryogels loaded with bioactive molecules compared to only composite cryogels groups. Our findings thus demonstrate a controlled and rapid synthetic method for the synthesis of nHAP with various physical, chemical, and biological properties exhibited as comparable to conventionally synthesized nHAP.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

3D bioprinting technology to construct bone reconstruction research model and its feasibility evaluation

Objective: To explore and construct a 3D bone remodeling research model displaying stability, repeatability, and precise simulation of the physiological and biochemical environment in vivo. Methods: In this study, 3D bioprinting was used to construct a bone reconstruction model. Sodium alginate (SA), hydroxyapatite (HA) and gelatin (Gel) were mixed into hydrogel as scaffold material. The osteoblast precursor cells MC3T3-E1 and osteoclast precursor cells RAW264.7 were used as seed cells, which may or may not be separated by polycarbonate membrane. The cytokines osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) were used to induce cell differentiation. The function of scaffolds in the process of bone remodeling was analyzed by detecting the related markers of osteoblasts (alkaline phosphatase, ALP) and osteoclasts (tartrate resistant acid phosphatase, TRAP). Results: The scaffold showed good biocompatibility and low toxicity. The surface morphology aided cell adhesion and growth. The scaffold had optimum degradability, water absorption capacity and porosity, which are in line with the conditions of biological experiments. The effect of induced differentiation of cells was the best when cultured alone. After direct contact between the two types of cells at 2D or 3D level, the induced differentiation of cells was inhibited to varying degrees, although they still showed osteogenesis and osteoclast. After the cells were induced by indirect contact culture, the effect of induced differentiation improved when compared with direct contact culture, although it was still not as good as that of single culture. On the whole, the effect of inducing differentiation at 3D level was the same as that at 2D level, and its relative gene expression and enzyme activity were higher than that in the control group. Hence the scaffold used in this study could induce osteogenesis as well as osteoclast, thereby rendering it more effective in inducing new bone formation. Conclusion: This method can be used to construct the model of 3D bone remodeling mechanism.

Enhanced photocatalytic and antibacterial activities of novel Ag-HA bioceramic nanocatalyst for waste-water treatment

Hydroxyapatite (HA), the most common bioceramic material, offers attractive properties as a catalyst support. Highly crystalline mono-dispersed silver doped hydroxyapatite (Ag-HA) nanorods of 60 nm length was developed via hydrothermal processing. Silver dopant offered enhanced chemisorption for crystal violet (CV) contaminant. Silver was found to intensify negative charge on the catalyst surface; in this regard enhanced chemisorption of positively charged contaminants was accomplished. Silver dopant experienced decrease in the binding energy of valence electron for oxygen, calcium, and phosphorous using X-ray photoelectron spectroscopy XPS/ESCA; this finding could promote electron-hole generation and light absorption. Removal efficiency of Ag-HA nanocomposite for CV reached 88% after the synergistic effect with 1.0 mM H2O2; silver dopant could initiate H2O2 cleavage and intensify the release of active ȮH radicals. Whereas HA suffers from lack of microbial resistance; Ag-HA nanocomposite demonstrated high activity against Gram-positive (S. aureus) bacteria with zone of inhibition (ZOI) mm value of 18.0 mm, and high biofilm inhibition of 91.1%. Ag-HA nanocompsite experienced distinctive characerisitcs for utilization as green bioceramic photocatalyst for wastewater treatment.

How Magnetic Composites are Effective Anticancer Therapeutics? A Comprehensive Review of the Literature

Chemotherapy is the most prominent route in cancer therapy for prolonging the lifespan of cancer patients. However, its non-target specificity and the resulting off-target cytotoxicities have been reported. Recent in vitro and in vivo studies using magnetic nanocomposites (MNCs) for magnetothermal chemotherapy may potentially improve the therapeutic outcome by increasing the target selectivity. In this review, magnetic hyperthermia therapy and magnetic targeting using drug-loaded MNCs are revisited, focusing on magnetism, the fabrication and structures of magnetic nanoparticles, surface modifications, biocompatible coating, shape, size, and other important physicochemical properties of MNCs, along with the parameters of the hyperthermia therapy and external magnetic field. Due to the limited drug-loading capacity and low biocompatibility, the use of magnetic nanoparticles (MNPs) as drug delivery system has lost traction. In contrast, MNCs show higher biocompatibility, multifunctional physicochemical properties, high drug encapsulation, and multi-stages of controlled release for localized synergistic chemo-thermotherapy. Further, combining various forms of magnetic cores and pH-sensitive coating agents can generate a more robust pH, magneto, and thermo-responsive drug delivery system. Thus, MNCs are ideal candidate as smart and remotely guided drug delivery system due to a) their magneto effects and guide-ability by the external magnetic fields, b) on-demand drug release performance, and c) thermo-chemosensitization under an applied alternating magnetic field where the tumor is selectively incinerated without harming surrounding non-tumor tissues. Given the important effects of synthesis methods, surface modifications, and coating of MNCs on their anticancer properties, we reviewed the most recent studies on magnetic hyperthermia, targeted drug delivery systems in cancer therapy, and magnetothermal chemotherapy to provide insights on the current development of MNC-based anticancer nanocarrier.

Selected Textural and Electrochemical Properties of Nanocomposite Fillers Based on the Mixture of Rose Clay/Hydroxyapatite/Nanosilica for Cosmetic Applications

In order to improve the properties and characteristics of rose clay composites with acai, hydroxyapatite (HA), and nanosilica, the systems were mechanically treated. This treatment provides the preparation of better nanostructured composites with natural and synthetic nanomaterials with improved properties. The materials were characterized using XRD, nitrogen adsorption and desorption, particle sizing, zeta potential, and surface charge density measurements. For the systems tested in the aqueous media, the pH value of the point of zero charge (pH_PZC) ranges from 8 to 9.9. However, the isoelectric point (pH_IEP) values for all composites are below pH 2. This large difference between pH_PZC and pH_IEP is due to the complexity of the electrical double layer (EDL) and the relation of these points to different layers of the EDL. The tested samples as composite/electrolyte solutions are colloidally unstable. The toxicity level of the ingredients and release of anthocyanins as bioactive substances from acai in the composites were determined. The composites demonstrate an enhanced release of anthocyanins. There are some regularities in the characteristics depending on the type of components, morphology, and textural features of solids. The morphological, electrochemical, and structural characteristics of the components have changed in composites. The release of anthocyanins is greater for the composites characterized by minimal confined space effects in comparison with rose clay alone. The morphological, electrochemical, and structural characteristics allow us to expect high efficiency of composites as bioactive systems that are interesting for practical applications in cosmetics.

Preparation and characterization of FsHA/FsCol beads: Cell attachment and cytotoxicity studies

The present study was conducted to prepare the fish scales' hydroxyapatite/collagen beads (FsHA/FsCol) and characterize their biological, physical, and chemical properties. A new method was used to prepare FsHA/FsCol composite beads by infiltrating the beads of FsHA in the solution of FsCol as a green method. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) analysis, Fourier-transform infrared (FTIR) spectroscopy analysis and energy dispersive X-ray analysis (EDX), used to evaluate the physical-chemical properties of the synthesized samples. Meanwhile, the cytotoxic and attachment studies of the FsHA/FsCol beads were used to investigate the biological features against the MG-63 human cell line. The results specified the efficiency of the new method, functional groups of FsCol were indicated to be present inside the beads of FsHA according to the XRD analysis which shows the functional peaks of FsCol. The SEM image were conformed successfully use starch as a porous agent to increasing the porous of the FsHA beads after adding 20 wt% of it. Alamar Blue assay has been used to evaluate the cytotoxicity of FsHA/FsCol beads the results were shown 87% average cell viability of the MG-63 human cell line on the beads and attached very well to the surface of the composites, indicating no toxicity being exerted by all the composites at high concentrations.

The Impact of Solution Ionic Strength, Hardness, and pH on the Sorption Efficiency of Polychlorinated Biphenyls in Magnetic Nanocomposite Microparticle (MNM) Gels

Environmental conditions of groundwater and surface water greatly vary as a function of location. Factors such as ionic strength, water hardness, and solution pH can change the physical and chemical properties of the nanocomposites used in remediation and the pollutants of interest. In this work, magnetic nanocomposite microparticle (MNM) gels are used as sorbents for remediation of PCB 126 as model organic contaminant. Three MNM systems are used: curcumin multiacrylate MNMs (CMA MNMs), quercetin multiacrylate MNMs (QMA MNMs), and polyethylene glycol-400-dimethacrylate MNMs (PEG MNMs). The effect of ionic strength, water hardness, and pH were studied on the sorption efficiency of the MNMs for PCB 126 by performing equilibrium binding studies. It is seen that the ionic strength and water hardness have a minimal effect on the MNM gel system sorption of PCB 126. However, a decrease in binding was observed when the pH increased from 6.5 to 8.5, attributed to anion-π interactions between the buffer ions in solution and the PCB molecules as well as with the aromatic rings of the MNM gel systems. Overall, the results indicate that the developed MNM gels can be used as magnetic sorbents for polychlorinated biphenyls in groundwater and surface water remediation, provided that the solution pH is controlled.

Hydroxyapatite-based composites: Excellent materials for environmental remediation and biomedical applications

Given their unique characteristics and properties, Hydroxyapatite (HAp) nanomaterials and nanocomposites have been used in diverse advanced catalytic technologies and in the field of biomedicine, such as drug and protein carriers. This paper examines the structure and properties of the manufactured HAp as well as a variety of synthesis methods, including hydrothermal, microwave-assisted, co-precipitation, sol-gel, and solid-state approaches. Additionally, the benefits and drawbacks of various synthesis techniques and ways to get around them to spur more research are also covered. This literature discusses the various applications, including photocatalytic degradation, adsorptions, and protein and drug carriers. The photocatalytic activity is mainly focused on single-phase, doped-phase, and multi-phase HAp, while the adsorption of dyes, heavy metals, and emerging pollutants by HAp are discussed in the manuscript. Furthermore, the use of HAp in treating bone disorders, drug carriers, and protein carriers is also conferred. In light of this, the development of HAp-based nanocomposites will inspire the next generation of chemists to improve upon and create stable nanoparticles and nanocomposites capable of successfully addressing major environmental concerns. This overview's conclusion offers potential directions for future study into HAp synthesis and its numerous applications.

An Investigation of a Natural Biosorbent for Removing Methylene Blue Dye from Aqueous Solution

T he current study reports the use of zeolite prepared from a kaolin composite via physical mixing with different ratios from fiber of palm tree (Zeo-FPT) as a sustainable solid sorbent for the removal of methylene blue (MB) dye from aqueous solutions. The prepared biosorbent was fully characterized using XRD, TGA, SEM, and FTIR. The impacts of various analytical parameters, for example, contact time, dosage, MB dye concentration, and the pH of the solution, on the dye adsorption process were determined. After a contact time of 40 min, the capacity to remove MB dye was 0.438 mg g−1 at a Zeo-FPT composition ratio of 1F:1Z. At pH 8, Zeo-FPT (1F:1Z) had a removal efficiency of 87% at a sorbent dosage of 0.5 g for a concentration of MB dye in an aqueous phase of 10 mg L−1. The experimental data were also analyzed using the kinetic and adsorption isotherm models. The retention process fitted well with the pseudo-second-order model (R2 0.998), where the Qe,calc of 0.353 mg g−1 was in acceptable agreement with the Qe,exp of 0.438 mg g−1. The data also fitted well with the Freundlich isotherm model, as indicated by the correlation coefficient value (R2 0.969). The Zeo-FPT attained a high percentage (99%) in the removal of MB dye from environmental water samples (tap water, bottled water, and well water). Thus, it can be concluded that the proposed zeolite composite with fiber of palm tree (Zeo-FPT) is a suitable, environmentally friendly, and low-cost adsorbent for removing dyes from wastewater.

Highly Efficient Removal of Uranium from an Aqueous Solution by a Novel Phosphonic Acid-Functionalized Magnetic Microsphere Adsorbent

The development of adsorption materials which can efficiently isolate and enrich uranium is of great scientific significance to sustainable development and environmental protection. In this work, a novel phosphonic acid-functionalized magnetic microsphere adsorbent Fe₃O₄/P (GMA-MBA)-PO₄ was developed by functionalized Fe₃O₄/P (GMA-MBA) prepared by distill-precipitation polymerization with O-phosphoethanolamine. The adsorption process was endothermic, spontaneous and kinetically followed the pseudo second-order model. The maximum uranium adsorption capacity obtained from the Langmuir model was 333.33 mg g^-1 at 298 K. In addition, the adsorbent also had good acid resistance and superparamagnetic properties, which could be quickly separated by a magnetic field. XPS analysis showed that the adsorption of adsorbent mainly depended on the complexation of phosphonic acid group with uranium. This work offers a promising candidate for the application of magnetic adsorbents in the field of uranium separation and enrichment.

Wet End Chemical Properties of a New Kind of Fire-Resistant Paper Pulp Based on Ultralong Hydroxyapatite Nanowires

In 2014, a new type of the fire-resistant paper based on ultralong hydroxyapatite (HAP) nanowires was reported by the author’s research group, which had superior properties and promising applications in various fields, such as high-temperature resistance, fire retardance, heat insulation, electrical insulation, energy, environmental protection, and biomedicine. The wet end chemical properties of the fire-resistant paper pulp are very important for papermaking and mechanical performance of the paper, which play a guiding role in the practical production of the fire-resistant paper. In this paper, the wet end chemical properties of a new kind of fire-resistant paper pulp based on ultralong HAP nanowires are studied for the first time by focusing on the wet end chemical parameters, the effects of these parameters on the properties such as flocculation, retention, draining, and white water circulation of the fire-resistant paper pulp, and their effects on the properties of the as-prepared fire-resistant paper. The experimental results indicated that the wet end chemical properties of the new kind of fire-resistant paper pulp based on ultralong HAP nanowires were unique and entirely different from those of the traditional paper pulp based on plant fibers. The wet end chemical properties of the fire-resistant paper pulp were significantly influenced by the inorganic adhesive and its content, which affected the runnability of the paper machine and the properties of the as-prepared fire-resistant paper. The flocculation properties of the fire-resistant paper pulp based on ultralong HAP nanowires were affected by the conductivity and Zeta potential. The addition of the inorganic adhesive in the fire-resistant paper pulp based on ultralong HAP nanowires could significantly increase the conductivity of the fire-resistant paper pulp, reduce the particle size of paper pulp floccules, and increase the tensile strength of the fire-resistant paper. In addition, the fire-resistant paper pulp based on ultralong HAP nanowires in the presence of inorganic adhesive exhibited excellent antibacterial performance. This work will contribute to and accelerate the commercialization process and applications of the new type of the fire-resistant paper based on ultralong HAP nanowires.

Synthesis of a Magnetic Carnation-like Hydroxyapatite/Basic Calcium Carbonate Nanocomposite and Its Adsorption Behaviors for Lead Ions in Water

Calcium-enriched compounds have great potential in the treatment of heavy-metal contaminated wastewater. Preparing stable basic calcium carbonate (BCC), which is a calcium-enriched compound, and applying it in practice is a great challenge. This work investigated the formation process of hierarchical hydroxyapatite (HAP)/BCC nanocomposites and their adsorption behaviors regarding lead ions (Pb2+). The morphology of the HAP/BCC nanocomposite was controlled by the addition of monododecyl phosphate (MDP). The carnation-like HAP/BCC nanocomposite was achieved with the addition of 30 g of MDP. The carnation-like HAP/BCC nanocomposite had a high Pb2+ adsorption capacity of 860 mg g-1. The pseudo-second-order and Freundlich model simulation results indicated that the adsorptions of Pb2+ on the nanocomposites belonged to the chemisorption and multilayer adsorption processes. The main effective adsorption components for the nanocomposites were calcium-enriched HAP and BCC. Through the Ca2+ ions exchanging with Pb2+, the HAP and BCC phases were converted to hydroxyl-pyromorphite (Pb-HAP) and hydrocerussite (Pb3(CO3)2(OH)2), respectively. The carnation-like HAP/BCC nanocomposite has great potential in the treatment of heavy metal ions. This facile method provides a new method for preparing a stable HAP/BCC nanocomposite and applying it in practice.

Surface-Fabrication of Fluorescent Hydroxyapatite for Cancer Cell Imaging and Bio-Printing Applications

Hydroxyapatite (HAP) materials are widely applied as biomedical materials due to their stable performance, low cost, good biocompatibility and biodegradability. Here, a green, fast and efficient strategy was designed to construct a fluorescent nanosystem for cell imaging and drug delivery based on polyethyleneimine (PEI) and functionalized HAP via simple physical adsorption. First, HAP nanorods were functionalized with riboflavin sodium phosphate (HE) to provide them with fluorescence properties based on ligand-exchange process. Next, PEI was attached on the surface of HE-functionalized HAP (HAP-HE@PEI) via electrostatic attraction. The fluorescent HAP-HE@PEI nanosystem could be rapidly taken up by NIH-3T3 fibroblast cells and successfully applied to for cell imaging. Additionally, doxorubicin hydrochloride (DOX) containing HAP-HE@PEI with high loading capacity was prepared, and in-vitro release results show that the maximum release of DOX at pH 5.4 (31.83%) was significantly higher than that at pH 7.2 (9.90%), which can be used as a drug delivery tool for cancer therapy. Finally, HAP-HE@PEI as the 3D inkjet printing ink were printed with GelMA hydrogel, showing a great biocompatible property for 3D cell culture of RAW 264.7 macrophage cells. Altogether, because of the enhanced affinity with the cell membrane of HAP-HE@PEI, this green, fast and efficient strategy may provide a prospective candidate for bio-imaging, drug delivery and bio-printing.

Removal of 142Pr from nuclear purity water using hydroxyapatite

The adsorption of praseodymium using hydroxyapatite was evaluated. The hydroxyapatite (HAP) was characterized by X-ray diffraction (JCPDS 01-04-3708), scanning electron microscopy, BET specific surface area (54.2 m²/g), and point of zero charge (6.5). Adsorption kinetics and isotherms were evaluated at pH of 3 and ¹⁴²Pr was determined using a gamma spectrometer. The adsorption of praseodymium was fast (1 min of contact) with an adsorption capacity of 1.68 mg/g and the data were best adjusted to the pseudo-second-order model, whereas the data of adsorption isotherm were best adjusted to the Langmuir model with a maximum adsorption capacity of 39.16 ± 0.20 mg/g. The thermodynamic parameters indicated that a physicochemical mechanism took place in the adsorption of praseodymium by HAP (adsorption enthalpy = 31.65 kJ/mol), the randomness of the system increased (adsorption entropy = 0.16 kJ/mol), and according with Gibbs free energy, the adsorption process was spontaneous at high temperature. The praseodymium in the hydroxyapatite is stable, it could not be desorbed using different solutions (ammonium sulfate, calcium chloride, sodium chloride, hydrochloric acid, and sodium hydroxide).

Physicochemical Characterization and Antibacterial Activity of Titanium/Shellac-Coated Hydroxyapatite Composites

Titanium and hydroxyapatite are widely used as materials for implants. Titanium has good mechanical properties, good corrosion resistance, and a high modulus of elasticity. Hydroxyapatite has good biocompatibility, bioactivity, and significant osteoinductivity. In this study, powder metallurgy was used as a method to combine titanium and hydroxyapatite for use in implants. Shellac was used as a binder between ceramic and metal due to its lower melting point. The surface morphology and chemical properties were evaluated by scanning electron microscopy–energy dispersive X-ray (SEM-EDX), whereby the SEM revealed the appearance of micropores in the Ti-HA composites during the sintering process, and the EDX showed that the final product had high amounts of Ti and Ca and low P. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses were used to achieve the chemical characterization of composites, whereby a weak diffraction peak was observed in the XRD spectrum of Ti-HA composites, and the FTIR analysis confirmed that the composites had carbonate (CO3)2−, phosphate (PO4)3−, and hydroxyl (OH)− groups. Oxygen was sufficient due to the sintering process being conducted in an air environment. The antibacterial activities were characterized using the disc diffusion method with Escherichia coli and Staphylococcus aureus bacteria, whereby the prepared Ti-HA composites had a greater antibacterial effect on E. coli than on S. aureus. Finally, pH changes were observed during the 24 h incubation. The result showed that the Ti-HA composite did not contain chemical compounds that could cause harmful effects for humans and had good antibacterial activity against E. coli.

Investigation of Inclusion States of Silicate and Carbonate Ions in Hydroxyapatite Particles Prepared under the Presence of Sodium Silicate

Biological hydroxyapatite (HA) contains the different minor ions which favour its bio-reactivity in vivo. In this study, the preparation of HA particles containing both silicate and carbonate ions under the presence of sodium silicate was investigated, and the physicochemical properties were evaluated according to the contents and states of silicate and carbonate ions. The increment in the silicate ion reduced the crystallinity and expanded the crystalline size along with a-axis. Solid-state ²⁹Si–NMR spectra indicated the increase in the adsorption of oligomeric silicate species on the HA particle surfaces in addition to the substitution state of silicate ions, suggesting the occurrence of the surface coating of silicates on the surfaces. The possible states of carbonate and silicate ions at the HA surfaces will provide the bioactivity.

Highly enhanced adsorption performance to uranium(VI) by facile synthesized hydroxyapatite aerogel

In order to protect environment and save uranium resources, it was necessary to find a highly efficient adsorbent for uranium recovery from wastewater. In this work, we used a freeze-drying-calcination method to synthesize HAP aerogel to effectively remove uranium. Compared with commercially available nano-hydroxyapatite, HAP aerogel presented better adsorption performance. This was because the as-prepared HAP aerogel presented continuous porous structure, which could provide more active sites for the adsorption to uranium. The uranium removal efficiency of HAP aerogel arrived 99.4% within 10 min and the maximum adsorption capacity was up to 2087.6 mg g^-1 at pH = 4.0 and 298 K. In addition, the immobilization of uranium on HAP aerogel was chemisorption, which was probably due to adsorption, dissolution-precipitation and ions exchange. These results indicated that the as-prepared HAP aerogel could be widely used as a high efficiency and potential adsorbent for the treatment of uranium-containing wastewater in the future.

Synthesis of Hydroxyapatite/Iron Oxide Composite and Comparison of Selected Structural, Surface, and Electrochemical Properties

The paper presents the synthesis of a hydroxyapatite/iron oxide composite utilizing the wet chemical method, as well as the comparison of several selected material characteristics. As follows from the literature reports, hydroxyapatite is a common mineral possessing numerous significant properties. Nowadays, there is an increase in the amount of research on possible modifications of this compound. The promising way to improve hydroxyapatite features is its combination with iron oxide. Particularly, there can be two forms that are distinguished, namely Fe₃O₄ and γ-Fe₂O₃. These oxides exhibit valuable properties, particularly magnetism. A combination of the mentioned materials leads to multifunctional composite formation with many potential applications, as follows from several studies. However, this area of science is not fully developed. There are still many aspects to be examined. The synthesized composite and its components were analyzed by employing the following methods. The X-ray diffraction analysis revealed formation of hydroxyapatite and Fe₂O₃ crystalline phases. Moreover, porosimetry proved a larger specific area for the composite sample in comparison with other materials. The results obtained using the SEM method confirmed an external layer of hydroxyapatite and spherical shapes of internal Fe₂O₃ particles. Furthermore, the X-ray photoelectron spectroscopy data presented characteristic peaks of Fe, Ca, P, and O atoms in all samples. The Fourier Transform Infrared spectra displayed all the specific vibrations typical of the analyzed materials. What is more, the Vibrating Sample Magnetometer method confirmed the paramagnetic nature of the samples. It could be concluded that the synthesized composite has intermediate properties between the components used in the formation process. The results suggest that these composites are superparamagnetic. This type of material architecture would be well suited for biomedical applications.

Hydroxyapatite-based adsorbents: Applications in sequestering heavy metals and dyes

Hydroxyapatite (HAp) is a calcium phosphate material that was used primarily in bone regeneration and repair as a result of its chemical similarity with bone. However, HAp has emerged as a very promising adsorbent for sequestering contaminants like heavy metals, dyes, hydrocarbons as well as other emerging pollutants from wastewater as a result of its versatility and encouraging adsorptive properties. Contaminants like heavy metals and dyes have been a major source of environmental concern. Research studies involving the use of HAp as adsorbents for the adsorptive treatment of heavy metal- and dye-contaminated wastewater have become increasingly popular due to its eco-friendliness, easy synthesis, unique adsorption properties etc. Various methods are available for the synthesis of HAp and its composites with some of these methods used in combination with other methods to obtain more efficient HAp-based adsorbents. In this work, the adsorptive removal of heavy metals and dyes by HAp and its composites was extensively reviewed as well as the parametric effects of process factors like contact time, solution pH, temperature, solute concentration etc on the adsorption process. Kinetic, thermodynamic, and isotherm models for elucidating the adsorption process were also considered. Generally, from the works reviewed, HAp-based adsorbents were found to be very effective for sequestering heavy metals and dyes from solution and thus presents a low-cost option for adsorptive wastewater treatment.