Facet-Controlled Growth of Hydroxyapatite for Effectively Removing Pb from Aqueous Solutions

To address the growing concerns regarding severe water pollution, effective and environmentally friendly adsorbents must be identified. In this study, we prepared hydroxyapatite (HAp, Ca10(PO4)6(OH)2) as an eco-friendly absorbent via simple precipitation and obtained rod- (r-HAp) and plate-shaped HAp (p-HAp). The approach to obtaining p-HAp involved a low pH titration rate, promoting growth along the c-axis due to the adsorption of OH- on the (110) facet. Conversely, r-HAp was obtained by maintaining a high concentration of OH- during the initial stage through rapid pH titration, leading to a stronger restrictive effect on the growth of positively charged a(b)-planes. p-HAp demonstrated superior adsorption capacity, removing Pb through dissolution and recrystallization, achieving an impressive 625 mg/g within a 60 min reaction time compared to r-HAp. Our findings afford insights into the Pb removal mechanisms of HAp with different morphologies and can aid in the development of water purification strategies against heavy metal contamination.

A novel non-enzymatic electrochemical uric acid sensing method based on nanohydroxyapatite from eggshell biowaste immobilized on a zinc oxide nanoparticle modified activated carbon electrode (Hap-Esb/ZnONPs/ACE)

Hydroxyapatite-derived eggshell biowaste (Hap-Esb) has been fabricated and developed for the electrochemical detection of uric acid (UA). The physicochemical characteristics of the Hap-Esb and modified electrodes were evaluated using a scanning electron microscope and X-ray Diffraction analysis. Utilized as UA sensors, the electrochemical behavior of modified electrodes (Hap-Esb/ZnONPs/ACE) was assessed using cyclic voltammetry (CV). The superior peak current response observed for the oxidation of UA at Hap-Esb/ZnONPs/ACE, which was 13 times higher than that of the Hap-Esb/activated carbon electrode (Hap-Esb/ACE) is attributed to the simple immobilization of Hap-Esb on zinc oxide nanoparticle-modified ACE. The UA sensor exhibited a linear range at 0.01 to 1 μM, low detection limit (0.0086 μM), and excellent stability, which surpass the existing Hap-based electrodes reported in the literature. The facile UA sensor subsequently realized is also advantaged by its simplicity, repeatability, reproducibility, and low cost, applicable for real sample analysis (human urine sample).

Geopolymer composite spheres derived from graphene-modified fly ash/slag: Facile synthesis and removal of lead ions in wastewater

Geopolymer composite spheres derived from potassium-activated graphene-modified slag/fly ash powder were produced in a polyethylene glycol (PEG 400) solvent. The effect of graphene type (graphene oxide (GO) and few-layered graphene (GNP)) on the pore structure and lead ions (Pb²⁺) removal performance of the spheres were evaluated. The results showed that the composite spheres modified with GOs (0.1-0.4 wt%) and GNPs (1-4 wt%) could be spheroidized with an improved performance to adsorb Pb²⁺ in solution. The graphene-containing spheres reached a maximum BET surface area of 68.85 m²/g. Pseudo-second-order and Langmuir isotherm models could express the adsorption process, which was controlled by both monolayer adsorption and chemisorption. The obtained spheres also showed high adsorption capacities for Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ ions. Chemical, physical, electrostatic, ion exchange and cation-π interaction were attributed to the adsorption mechanism of the spheres. The spheres showed good cycling ability compared to those without graphene, which had potential application in heavy metal wastewater treatment.

Adsorption of As(III) and As(V) by Fe/C composite nanoparticles synthesized via a one-pot hydrothermal approach without the addition of carbon sources

Arsenic remediation from contaminated water has become a serious issue worldwide. Carbon-encapsulated Fe nanoparticle composites (Fe/C CNPs) were created utilizing a one-pot hydrothermal process with ferrocene and no carbon sources. The Fe/C CNPs produced were characterized using a variety of techniques. As(III) and As(IV) (V) were modeled using a pseudo-second-order kinetic model. The Langmuir model described As(III) adsorption on Fe/C CNPs with an extreme adsorption ability of 5.85 mg g^-1, indicating monolayer adsorption. On the other hand, (V) adsorption was well matched with the Freundlich model, with a high adsorption volume of 5.05 mg g^-1, demonstrating multilayer adsorption onto the surface of Fe/C CNPs. These findings imply that the Fe/C CNPs generated can be utilized to remediate As-contaminated water.

S. N. SN, Lakshmipathy M, Sagadevan S, Mohammad F, Al-Lohedan HA, Paiman S, Oh WC. Nanoformulations of core–shell type hydroxyapatite-coated gum acacia with enhanced bioactivity and controlled drug delivery for biomedical applications

In this work, nanospherical hydroxyapatite (HAP) was prepared that has combined properties of controlled drug delivery, biocompatibility, and antibacterial activity to have applications in the biomedical sector.

Copper Nanocluster-Doped Luminescent Hydroxyapatite Nanoparticles for Antibacterial and Antibiofilm Applications

Novel strategies in the field of nanotechnology for the development of suitable multifunctional drug delivery vehicles have been pursued with promising upshots. Luminescent copper nanocluster-doped hydroxyapatite nanoparticles (HAP NPs) were synthesized and applied for the delivery of antibacterial drug kanamycin. The negatively charged doped HAP NPs could electrostatically interact with the positively charged kanamycin. The kanamycin-loaded doped HAP NPs showed pronounced activity in the case of Gram-negative bacteria compared to that in Gram-positive bacteria. Upon interaction with the bacteria, kanamycin could probably generate harmful agents such as hydroxyl radical that leads to bacterial cell damage. After being incorporated with copper nanoclusters (Cu NCs), the doped HAP NPs were applied for the bioimaging of bacterial cells. The biocompatibility of doped HAP NPs was also studied in HeLa cells. As compared to copper nanoclusters, the doped HAP NPs showed excellent biocompatibility even at higher concentrations of copper. The kanamycin-loaded doped HAP NPs were further applied toward Pseudomonas aeruginosa biofilm eradication. Thus, the as-synthesized copper nanocluster-doped HAP NPs were applied as nanocarriers for antibiotic drug delivery, bioimaging, and antibiofilm applications.

A novel approach to preparation of nano-adsorbent from agricultural wastes (Saccharum officinarum leaves) and its environmental application

Saccharum officinarum leaves (SL) assisted nano-silica (NS) were synthesized and used as adsorbent to remove Pb²⁺ and Zn²⁺ from aqueous solutions. The crystalline nature, functional group, and morphology structure of synthesized NS were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission-scanning electron microscopy (FESEM) with EDS mapping, and transmission electron microscopy (TEM). The surface area and charge of the NS were also analyzed by Brunauer-Emmett-Teller (BET) and zeta potential analysis. Removal efficiency of Pb²⁺ and Zn²⁺ from aqueous solutions was carried out under batch mode studies (pH, dose, equilibrium time with initial heavy weight metal ion concentration). The adsorption parameters were determined using pseudo-first-order, pseudo-second-order, Langmuir, and Freundlich models. The kinetics and isotherms data were well fitted with pseudo-second-order and both Langmuir and Freundlich isotherm models. The maximum adsorption capacities for Pb²⁺ and Zn²⁺ onto NS at room temperature (37 °C) were found to be 148 mg/g and 137 mg/g, respectively. Finally, we conclude that the NS synthesized from SL leaves (agricultural waste material) were found to be economically viable, promising adsorbent for metal ions from aqueous solutions and also efficient technology for waste management.

Hollow mesoporous hydroxyapatite nanostructures; smart nanocarriers with high drug loading and controlled releasing features

We report the development of effective drug loaded nanocarriers to combat multidrug resistant infection especially in case of osteomyelitis. The hollow mesoporous hydroxyapatite nanoparticles (hmHANPs) and solid/non-hollow hydroxyapatite nanoparticles (sHANPs) were synthesized by core-shell and co-precipitation techniques respectively. High encapsulation of the drug (ciprofloxacin) was observed in hmHANPs as compared to sHANPs, which may be due to the hollow porous structure of hmHANPs. These nanoparticles were characterized by scanning electron microscope (FESEM), N₂ adsorption/desorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). Approximately 80% of the encapsulated drug was released at pH 4.5 within 5 days in case of hmHANPs while at pH 7.4, a sustained drug release profile was obtained and only 48.73% of the drug was released after 9 days. The results of kinetic drug release revealed that drug loaded hmHANPs showed fickian diffusion and anomalous drug diffusion mechanism at pH 4.5 and 7.4 respectively. Owing to their porous structure and high drug loading capacity, hmHANPs showed enhanced antibacterial activity against Staphylococcus aureus and Escherichia coli (drug resistant strains of osteomyelitis) in comparison to that with sHANPs. In addition, hmHANPs showed a pH sensitive drug release profile, high surface area (105.33 m²/g) with increased pore volume (0.533 cm³/g) and superior antimicrobial activity against osteomyelitis as compared to sHANPs.

Designed Synthesis of Nanostructured Magnetic Hydroxyapatite Based Drug Nanocarrier for Anti-Cancer Drug Delivery toward the Treatment of Human Epidermoid Carcinoma

Superparamagnetic Fe₃O₄ nanoparticles on hydroxyapatite nanorod based nanostructures (Fe₃O₄/HAp) were synthesized using hydrothermal techniques at 180 °C for 12 h and were used as drug delivery nanocarriers for cancer cell therapeutic applications. The synthesized Fe₃O₄/HAp nanocomposites were characterized by X-ray diffraction analysis (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET)-analysis, and vibrating sample magnetometry (VSM). The morphologies of the Fe₃O₄/HAp nanocomposites show 15 nm Fe₃O₄ nanoparticles dispersed in the form of rods. The BET result shows that the synthesized samples have a high specific surface area of 80 m² g-1 with mesoporous structures. Magnetic measurements revealed that the sample has high saturation magnetization of 18 emu/g with low coercivity. The Fe₃O₄/HAp nanocomposites had a large specific surface area (SSA), high mesoporous volume, and good magnetic property, which made it a suitable nanocarrier for targeted drug delivery systems. The chemotherapeutic agent, andrographolide, was used to investigate the drug delivery behavior of the Fe₃O₄/HAp nanocomposites. The human epidermoid skin cancer cells (A431) were used as the model targeting cell lines by treating with andrographolide loaded Fe₃O₄/HAp nanosystems and were further evaluated for their antiproliferative activities and the induction of apoptosis. Also, the present nanocomposite shows better biocompatibility, therefore it can be used as suitable drug vehicle for cancer therapy applications.

Natural polysaccharides leading to super adsorbent hydroxyapatite nanoparticles for the removal of heavy metals and dyes from aqueous solutions

Water pollution has created a major impact on the environment mainly due to contaminated industrial effluents with toxic substances such as heavy metals and textile dyes.

Enhanced cell viability of hydroxyapatite nanowires by surfactant mediated synthesis and its growth mechanism

Hydroxyapatite (HA) nanowires were synthesized using cetyl-trimethyl-ammonium-bromide (CTAB) as a surfactant and exhibited enhanced cell viability over other HA nanostructures.

Preparation of pH-responsive mesoporous hydroxyapatite nanoparticles for intracellular controlled release of an anticancer drug

A well-defined core–shell nano-carrier (PAA–MHAPNs) was successfully synthesized based on a graft-onto method by using mesoporous hydroxyapatite nanoparticles (MHAPNs) as the core and polyacrylic acid (PAA) as the shell.

High efficient multifunctional Ag3PO4 loaded hydroxyapatite nanowires for water treatment

Organic, inorganic, and biological pollutants are typical water contaminants and they seriously affect water quality. In this study, we suggested that a novel multifunctional Ag3PO4 loaded hydroxyapatite (HAP) material can remove the typical pollutants from water. The Ag3PO4/HAP composites were synthesized facilely via in-situ precipitation of Ag3PO4 on the pre-existing HAP nanowires. By optimizing the composition of Ag3PO4 and HAP, the material could achieve an optimal photocatalytic activity to decompose rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) under visible light irradiations with enhanced pH stability. Besides, the adsorption of Pb(II) on the Ag3PO4/HAP reached a maximum capacity of 250 mg/g and this value was approximately three times as that of pure HAP. Furthermore, the composite material exhibited excellent antibacterial activities towards gram-negative bacterium (Escherichia coli) and gram-positive bacterium (Stphylococcus aureus). The results highlighted the cooperative effect between Ag3PO4 and hydroxyapatite (HAP). The simultaneous removals of dyes, toxic metal ions, and bacteria with a high efficiency followed an easy approach for the purification of contaminated water via the rationally designed material, in which the Ag3PO4/HAP composite might be developed as a general water treatment material with multiple functions.

Fabrication of hydroxyapatite/chitosan porous materials for Pb(ii) removal from aqueous solution

Hydroxyapatite/chitosan porous materials are fabricated by a freeze-drying method for Pb(ii) removal from aqueous solution.

Enzymatic electrochemical glucose biosensors by mesoporous 1D hydroxyapatite-on-2D reduced graphene oxide

A hydrothermally synthesized mesoporous 1D HAp-on-2D RGO sheets exhibiting direct electrochemistry of glucose biosensing.

Hydroxyapatite nanoparticles on dendritic α-Fe2O3 hierarchical architectures for a heterogeneous photocatalyst and adsorption of Pb(ii) ions from industrial wastewater

A facile surfactant free hydrothermal process was used to prepare dendritic α-Fe₂O₃ and hydroxyapatite (HAp) nanoparticles dispersed on dendritic α-Fe₂O₃ nanostructures used for dye degradation and Pb(ii) ions removal from industrial wastewater.

Intracellular pH-responsive mesoporous hydroxyapatite nanoparticles for targeted release of anticancer drug

The design and synthesis of multifunctional nanocarriers is becoming a more and more interesting topic, and shows promising potential for clinical applications.

Facile in situ growth of Fe3O4 nanoparticles on hydroxyapatite nanorods for pH dependent adsorption and controlled release of proteins

The magnetic hydroxyapatite nanostructures were prepared by hydrothermal technique and studied their protein adsorption and in vitro cytotoxicity in humen MGC-803 cell.