HAp Nanoparticles Research Articles

Development of novel hybrid hydroxyapatite-based sensors for the ultrasensitive detection of L-tryptophan and L-tyrosine

A novel sensor using gold (Au) doped citrate-hydroxyapatite nanoparticles at different molar ratios wCitHAP-Au (w = 0.2, 0.4, 0.8) was developed. Citrate groups on the HAP nanoparticles surface makes it possible to carry out directly and homogeneously the “one-pot” deposition of the 0.5 % AuNPs from an aqueous solution. wCitHAP-0.5Au modified glassy carbon electrodes (GCE) are used in fundamental studies of the electron transfer, and in the construction of sensor devices for the determination of L-Tryptophane (TTP) and L-Tyrosine (TYR). Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) reveal the excellent electrocatalytic activity for oxidation and determination of TTP and TYR into phosphate buffer solution at pH 7 of the 0.2CitHAP-0.5Au/GCE electrode. Linear response ranges under optimal conditions were found to be 3.33 nM to 66.6 μM for TTP and 6 nM to 66.6 μM with detection limit of 3.33 nM and 6 nM, respectively. The fabricated sensor shows suitable sensitivity, stability, and can successfully applied for real samples determination.Additionally, Hirshfeld Surface (HS) analysis was conducted to gain deeper insights into the molecular properties, intermolecular interactions, and surface characteristics of the compounds studied. The HS analysis confirmed the presence of intermolecular interactions that stabilize the gold nanoparticles within the hydroxyapatite-citrate matrix, ensuring their uniform distribution and preventing aggregation.

Co-application of titanium dioxide and hydroxyapatite nanoparticles modulated chromium and salinity stress via modifying physio-biochemical attributes in Solidago canadensis L.

Climate change and human activity have led to an increase in salinity levels and the toxicity of chromium (Cr). One promising approach to modifying these stressors in plants is to use effective nanoparticles (NPs). While titanium dioxide nanoparticles (TiO2 NPs) and hydroxyapatite (HAP NPs) have been demonstrated to increase plant tolerance to abiotic stress by enhancing antioxidant capacity, lipid peroxidation, and secondary metabolites, it is unknown how these two compounds can work together in situations when salt and Cr toxicity are present. The objective of the current study was to determine the effects of foliar-applied TiO2 NPs (15mgL-1) and HAP NPs (250mgL-1) separately and in combination on growth, chlorophyll (Chl), water content, lipid peroxidation, antioxidant capacity, phenolic content, and essential oils (EOs) of Solidago canadensis L. under salinity (100mM NaCl) and Cr toxicity (100mgkg-1 soil). Salinity was more deleterious than Cr by decreasing plant weight, Chl a + b, relative water content (RWC), EO yield, and increasing malondialdehyde (MDA), electrolyte leakage (EL), superoxide dismutase (SOD) activity, and catalase (CAT) activity. The co-application of TiO2 and HAP NPs proved to be more successful. This was evidenced by the increased shoot weight (36%), root weight (29%), Chl a + b (23%), RWC (15%), total phenolic content (TPC, 34%), total flavonoid content (TFC, 28%), and EO yield (56%), but decreased MDA (21%), EL (11%), SOD (22%) and CAT activity (38%) in salt-exposed plants. The study demonstrated the effective strategy of co-applying these NPs to modify abiotic stress by enhancing phenolic compounds and EO yield as key results.

Flexible, electrospun boron nitride nanosheets (BNNS)/hydroxyapatite –PVDF nanofibers with superior piezoelectric/ferroelectric, biocompatible features for effective bone tissue regeneration

Piezoelectric/ferroelectric scaffolds are emerging tools in tissue engineering that offer new platforms for the repair and regeneration of damaged soft and hard tissues by means of electrical stimulation. In line with this, boron nitride nanosheets (BNNS)/hydroxyapatite (H)-polyvinylidene fluoride (PVDF) based piezoelectric electrospun nanofibers were developed for effective bone tissue regeneration. BNNS were prepared through a sequential process involving lithium intercalation, followed by hydrothermal exfoliation. Four distinct sets of nanofibers were prepared by altering the concentration of BNNS (2.5 wt%, 5 wt%, 10 wt%) while maintaining a constant concentration of HAP nanoparticles (2.5 wt%) in the PVDF polymer matrix. The piezoelectric/ferroelectric performance of the PVDF-H-BNNS nanofibers were found to be enhanced with the addition of BNNS. The PVDF-H-BNNS nanofibers, with an effective contact area of 1 cm2, exhibited remarkable piezoelectric characteristics, exhibiting a peak voltage of 13 V and a current of 1.63 µA under the influence of 10 N force at a frequency of 10 Hz, showcasing their exceptional electromechanical response. The cytocompatibility studies of PVDF-H-BNNS nanofibers on MG-63 and HOS cell lines reveals excellent viability of nanofibers, akin to that control. Cell proliferation investigations conducted with MG-63 and HOS cell lines on PVDF-H-BNNS showcased the remarkable biocompatibility of the engineered membranes. The PVDF-H-BNNS piezoelectric nanofibers, having exceptional piezo-response and enhanced cytocompatibility, hold promise as ideal candidates for applications in the field of bone tissue engineering.

Hydroxyapatite biomaterials: a comprehensive review of their properties, structures, clinical applications, and producing techniques

Abstract Before employing a biomedical material in medical applications, a researcher must possess comprehensive knowledge regarding its chemical, physical, biological, structural, and mechanical properties. Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is a vital constituent of the calcium orthophosphate group. The material exhibits good dielectric and biological compatibility, diamagnetic behavior, thermal stability, osteoconductivity, and bioactivity. Additionally, it has a Ca:P molar ratio of 1.67. Because HAp has a chemical composition that is quite similar to normal bone and teeth, it has the potential to be used as a material for implant implantation in fractured portions of the human skeletal system. Many ways for generating HAp nanoparticles have been found as a result of the increasing usage of HAp in medicine. The conditions under which HAp is generated determine its physical and chemical properties, crystalline structure, and form. This study provides detailed information on the HAp’s characteristics and manufacturing procedures, as well as revealing the structure and its properties.

Zn and Ni doped hydroxyapatite: Study of the influence of the type of energy source on the photocatalytic activity and antimicrobial properties

The present work aimed to produce HAp nanoparticles doped with Zn and Ni in order to analyze the incorporation of these elements in the catalytic and antimicrobial properties of HAp. The samples were obtained by the microwave-assisted hydrothermal method in 30 min at 150 °C. XRD and FTIR results showed that HAp was formed without the presence of secondary phases, and Rietveld refinement indicated a reduction in crystallite size after doping. Nanorod-like morphologies were observed by SEM-FEG with reduction in particle size and increase in specific surface area. Furthermore, the hidden gap at 3.26 eV, photoluminescence indicated that there was a predominance of deep defects and XPS showed the presence of dopants on the HAp surface. The catalytic results in the degradation of methylene blue dye indicated that the zinc-doped sample removed 97.85 % under sunlight, 66.81 % under UV light and 70.64 % under ultrasound. After four cycles of reuse under sunlight, good photocatalytic performance was maintained, and inhibition tests indicated that holes and hydroxyls are the active radicals. Antimicrobial activity tests showed that zinc-doped and co-doped samples were efficient in inhibiting Gram-negative bacteria (Escherichia coli). This work brings a promising alternative application for hydroxyapatite in environmental and microbial remediation.

A novel porous lignocellulosic standing hierarchical hydroxyapatite for enhanced aqueous copper(II) removal

Potentially toxic metal-polluted water resources are a heavily discussed topic the pollution by potentially toxic metals can cause significant health risks. Nanomaterials are actively developed towards providing high specific surface area and creating active adsorption sites for the treatment and remediation of these polluted waters. In an effort to tackle the limitations of conventional type adsorbents, nano-hydroxyapatite (HAp) was developed in this study by in situ generation onto wood powder, resulting in the formation of uniform hybrid powder (HAp@wood composite) structure consisting of HAp nanoparticles that showed the removal efficiency up to 80 % after 10 min; the maximum adsorption capacity for Cu(II) ions (98.95 mg/g-HAp) was higher compared to agglomerated nano-HAp (72.85 mg/g-HAp). The adsorption capacity of Cu(II) remained stable (89.85–107.66 mg/g-HAp) during the four adsorption-desorption cycles in multi-component system, thereby demonstrating high selectivity for Cu(II). This approach of using nanoparticle is relatively simple yet effective in improving the adsorption of potentially toxic metals and the developed approach can be used to develop advanced nanocomposites in commercial wastewater treatment.

Gallium-Doped Hydroxyapatite: Shape Transformation and Osteogenesis Activity.

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells.

Hydrothermal synthesis of antibacterial silver@cuprous oxide core-shell/hydroxyapatite (Ag@Cu2O/HAp) hetero-nanohybrids

ABSTRACT In the present work, we examined the antibacterial activity of novel silver@cuprous oxide core-shell/hydroxyapatite (Ag@Cu2O/HAp) hetero-nanohybrids against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. The hydrothermal technique was used to easily synthesise Ag@Cu2O/HAp core-shell nanohybrid structures. Immobilisation of Ag@Cu2O core shells on HAp nanoparticles was done by controlling the relative concentrations of Ag, Cu2O, and HAp. The Ag@Cu2O/HAp nanohybrids were characterised using XRD, FTIR, Raman, UV-vis, SEM, EDX, TEM, and SAED methods. By observing the growth of S. aureus and E. coli populations in the presence and absence of Ag, Ag@Cu2O, HAp, and Ag@Cu2O/HAp nanoparticles, their antibacterial impact was compared. MIC Alamar Blue assay was performed to study the cytotoxicity of Ag@Cu2O/HAp nanomaterials. In addition, reactive oxygen species (ROS) studies were conducted to understand the type of active species produced under light and dark conditions. The possible photochemical and antibacterial mechanisms of the Ag@Cu2O/HAp nanohybrids against S. aureus and E. coli bacteria were proposed. In addition, the promising antibacterial nature of Ag@Cu2O/HAp materials suggests that they are good candidates for industrial and biomedical applications.

Evaluation of the acute toxicity by Artemia salina of hydroxyapatite nanoparticles obtained via sol-gel in an aqueous medium without using additives

Hydroxyapatite (Hap) is one of the most important calcium phosphate bioceramics applied to bone tissue regeneration. Synthesizing Hap nanoparticles from easily accessible and low-cost alternative sources of calcium precursors remains a challenge, as well as defining an ideal and reproducible synthesis route without using additives to control the pH of the reaction and entirely performed at room temperature. This study proposes a route for the synthesis of hydroxyapatite by the sol-gel method without the addition of additives for pH control, carried out at room temperature. The Hap samples were characterized by FTIR, XRD, SEM, and BET. The synthesized Hap presented a spherical morphology without the formation of unwanted phases or residues. Samples calcined at 600 and 750 °C resulted in stoichiometric hydroxyapatite with 100% purity and average particle sizes of 24 and 53 nm, respectively. On the other hand, the samples calcined at 900 and 1050 °C presented a specific content of β-calcium phosphate and average particle sizes of 118 and 732 nm, respectively. Acute toxicity was evaluated by Artemia salina nauplii instar I and II for 24 and 48 h of exposure. The tests were conducted on 10, 100, and 1000 ppm of Hap dissolutions. The highest death rate and more significant morphological alterations were observed in A. salina nauplii instar II, exposed to Hap at a concentration of 1000 ppm for 48 h.

Hydroxyapatite nanoparticles: an alternative to conventional phosphorus fertilizers in acidic culture media

BackgroundTraditional phosphorus fertilizers generally have low efficiencies due to their immobilization in soil, and a large part of these fertilizers are not plant-available. Also, phosphorus resources are non-renewable. In recent years, a great deal of attention has been paid to nanofertilizers because of their slow or controlled release and also their very small particle size which increases the solubility and uptake of nanoparticles in plant. Hydroxyapatite nanoparticles are of great importance as phosphorus nanofertilizer thanks to their very low toxicity, biocompatibility, and the fact that products obtained from their degradation, i.e., phosphate and calcium ions, are naturally available in soils.ResultsIn this study, hydroxyapatite nanoparticles were synthesized using the wet chemical precipitation method in three formulations and characterized with various techniques including electron microscopy, atomic force microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and elemental analysis. Chemical and microscopic analyses showed that phosphorus was distributed in different parts of the wheat (Triticum aestivum L.) plant. To investigate the fertilizing effects of the nanoparticles, hydroxyapatite nanoparticles were used in different culture media including alkaline soil, acidic soil, the mixture of peat moss and perlite, and cocopeat. Based on our observations, hydroxyapatite nanoparticles showed fertilizing properties in all media. However, fertilizing potential strongly depended on the culture media. HAP nanoparticles demonstrated a high potential to be used as a fertilizer in acidic media. Nevertheless, only a slight fertilizing effect was observed in alkaline soils. Furthermore, the findings of our study showed fertilizing properties of powder hydroxyapatite nanoparticles without the need to convert them to suspension. Moreover, hydroxyapatite nanoparticles in all the three formulations showed low toxicity in such a way that their toxicity was even less than that of triple super phosphate.ConclusionsHydroxyapatite nanoparticles in both suspension and powder forms can be considered an alternative to conventional phosphorus fertilizers in acidic culture media. Our study revealed that hydroxyapatite nanoparticles were likely dissolved in the culture media and absorbed by plant mainly in the phosphate form.Graphical

Mechanical alloying and high-repetition-pulsed-laser based manufacturing method for nanostructured hydroxyapatite films on cobalt-chromium substrates

In this study, we report a manufacturing process for coating nanostructured and hierarchically porous Hydroxyapatite (HA) films on cobalt-chromium (CoCr) substrates. Nanoparticles of HAP are prepared using three different methods: ball milling of sol–gel synthesized HAP, mechanical alloying of calcium oxide (CaO) and diammonium phosphate (DAP), and mechanical alloying of eggshell and diammonium phosphate. The nanoparticle's characterization showed the presence of nanophase HAP in sol–gel synthesized powders and synthesis of apatite phases in mechanically alloyed powders. Small droplets of nanoparticle ethanol suspensions were injected on the substrate and irradiated with high-repetition-rate picosecond pulsed laser to coat the CoCr samples. Characterization of the deposited films showed bonding of HAP nanoparticles to a film with nanostructured morphology and hierarchical porosity and the incorporation of CoCr from the substrate into the first few deposited layers of HAP nanoparticles. The two-step manufacturing process results in bioactive and biocompatible HAP films with morphology that is desirable for the growth and infiltration of biological cells.

Fabrication and Characterisation of Calcium Sulphate Hemihydrate Enhanced with Zn- or B-Doped Hydroxyapatite Nanoparticles for Hard Tissue Restoration.

A composite based on calcium sulphate hemihydrate enhanced with Zn- or B-doped hydroxyapatite nanoparticles was fabricated and evaluated for bone graft applications. The investigations of their structural and morphological properties were performed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy techniques. To study the bioactive properties of the obtained composites, soaking tests in simulated body fluid (SBF) were performed. The results showed that the addition of 2% Zn results in an increase of 2.27% in crystallinity, while the addition of boron causes an increase of 5.61% compared to the undoped HAp sample. The crystallite size was found to be 10.69 ± 1.59 nm for HAp@B, and in the case of HAp@Zn, the size reaches 16.63 ± 1.83 nm, compared to HAp, whose crystallite size value was 19.44 ± 3.13 nm. The mechanical resistance of the samples doped with zinc was the highest and decreased by about 6% after immersion in SBF. Mixing HAp nanoparticles with gypsum improved cell viability compared to HAp for all concentrations (except for 200 µg/mL). Cell density decreased with increasing nanoparticle concentration, compared to gypsum, where the cell density was not significantly affected. The degree of cellular differentiation of osteoblast-type cells was more accentuated in the case of samples treated with G+HAp@B nanoparticles compared to HAp@B. Cell viability in these samples decreased inversely proportionally to the concentration of administered nanoparticles. From the point of view of cell density, this confirmed the quantitative data.

Structural and biological properties of novel Vanadium and Strontium co-doped HAp for tissue engineering applications

The development of novel bioactive materials with improved physical and biological properties is crucial for advancing tissue engineering applications. In this study, we synthesized a Vanadium and Strontium co-doped hydroxyapatite (V–Sr:HAp) nanoparticle intending to enhance the performance of pure HAp. The V–Sr:HAp nanoparticles were synthesized using a microwave-assisted reflux condensation method, and their structural and chemical characteristics were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The morphology and elemental composition of the nanoparticles were examined through scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The XRD analysis confirmed the presence of characteristic peaks of HAp in each sample. SEM images revealed well-connected and highly agglomerated small sphere-like morphology in both pure HAp and V–Sr:HAp nanoparticles. The Vickers hardness test demonstrated the improved mechanical strength in V–Sr:HAp compared to pure HAp. Antibacterial efficacy was evaluated using an agar diffusion test, which showed enhanced antibacterial activity in the co-doped HAp samples against S. aureus and P. aeruginosa. Moreover, the Ca–P deposition rate on the surface of the co-doped HAp samples during biomineralization was higher. Hemolysis assay results have indicated compatibility of both pure HAp and V–Sr:HAp with human blood (<5% lysis). The results of cell viability tests demonstrate that the V and Sr co-doped HAp samples do not exhibit any cytotoxic effects and instead promote cell proliferation. Overall, the incorporation of V and Sr metal ions into HAp presents a promising bio-functional tool for tissue engineering applications, offering improved mechanical and antibacterial properties.

Novel synthesis of hydroxyapatite microtubes using gelatin as sacrificial templates and their potential as biocompatible cell supporting matrix

Hydroxyapatite microtubes (HAp MTs) were synthesized through in situ deposition of HAp nanoparticles on the gelatin microfibers as novel sacrificial templates via a bio-mineralization route followed by a sintering process. The synthesized HAp MTs were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). SEM images reveal that HAp MTs had uniform tubular hollow structures with a diameter of 50–200 µm. XRD patterns indicate that HAp MTs were mainly constructed by apatite phase. Cytotoxic evaluation shows that HAp MTs were not cytotoxic and well biocompatible with osteoblast MC3T3-E1 cells. Most importantly, each individual HAp MT supported cell attachment and proliferation, indicating a potential as biocompatible cell supporting matrix.

Fabricating hydroxyapatite functionalized biochar composite using steel slag and Hami melon peel for Pb(II) and Cd(II) removal

With rising global concerns about the discharge of large volumes of waste materials derived from industrial manufacture and human life, methods for utilizing waste materials have been greatly developed. In this study, an ingenious hydroxyapatite (Hap) functionalized hierarchical porous biochar (HB) composite is fabricated using a filtrate rich in Ca2+ ions after steel slag reuse and spent Hami melon peel as raw materials. Microstructural analyses indicate that Hap nanoparticles are loaded on HB with hierarchical pores produced from a pyrolysis process of Hami melon peel. A series of HB-Hap materials by tuning HB addition amount (0.5, 1, and 2 g) can be obtained through a coprecipitation process. As a case study, HB-0.5Hap exhibits high specific surface area of 66.92 m2/g and high-efficiency removal performance for Pb(II) and Cd(II) ions in wastewater. The maximum adsorption capacities of HB-0.5Hap are 134.4 (Pb(II)) and 60.4 (Cd(II)) mg/g, which are 1.77 and 1.23 times higher than that of pure HB, respectively. It is attributed to a synergistic mechanism involving ion exchange, chemical precipitation, surface complexation, and cation-π interaction. According to a semi-quantitative calculation, ion exchange plays a major role in the removal of Pb(II) (78.61%, the relative contribution of ion exchange mechanism) and Cd(II) (77.77%). This study demonstrates a facile, economical, and sustainable strategy for the value-added utilization of steel slag and spent Hami melon peel, which can be critical in solving environmental problems.

Remediation of uranium(VI)-containing wastewater based on a novel graphene oxide/hydroxyapatite membrane

Membrane separation technology with unique advantages was widely used in wastewater treatment, especially U(VI)-containing wastewater. However, due to the low water flux and the unsatisfactory U(VI) interception rate of the membrane, the important breakthrough in the field of practical wastewater treatment could not be achieved. A novel graphene oxide/hydroxyapatite (GO/HAP, GHP) membrane was prepared by a simple in-situ deposition self-assembly method. The GO/HAP dispersion was firstly obtained by in-situ growth of HAP nanoparticles on GO sheets and then self-assembled to prepare GO/HAP membranes by vacuum filtration. The membranes were provided with high water flux due to the fact that the addition of HAP nanoparticles effectively increased the layer spacing of graphene sheets. The flux of GHP-2 membrane to U(VI)-containing wastewater was about 273.4 L‧m−2‧h−1‧bar−1 and U(VI) retention rate was 99.4%. GHP-2 membrane also had good recycling performance and could still reach high retention rate (82.5%) after five cycles. The high rejection rate of GHP-2 membrane for U(VI) was owing to the internal induced separation mechanism. To sum up, the prepared GHP membranes had the potential for water environment renovation.

Tailoring of hydroxyapatite nanoparticle surfaces of varying morphologies to facilitate counterion diffusion and subsequent protein denaturation

Rapid advances in nanotechnology have led to the synthesis and development of various nanomaterials with complex structures and appropriate surface functionalization in recent years. Specifically designed and functionalized nanoparticles (NPs) are increasingly researched and hold great potential in biomedical applications (for example, imaging, diagnostics and therapeutics). Yet, the surface functionalization and biodegradability of NPs play a significant role in their application. Understanding the interactions occurring at the interface between the NPs and the biological components is thus crucial for predicting the fate of the NPs. In this work we study the effect of trilithium citrate functionalization of the hydroxyapatite NPs (HAp NPs) with and without cysteamine modification and their subsequent interaction with hen egg white lysozyme and corroborate the conformational changes of the protein with effective diffusion of the lithium (Li+) counter ion.

Effect of reaction temperature and pH on structural and morphological properties of hydroxyapatite from precipitation method

Hydroxyapatite nanoparticle plays a significant role in the field of biomedical industries such as tissue engineering and regenerative medicine, carriers for drug delivery, photocatalyst, biosensors, and membranes for heavy metal removal from polluted water. The present work aims to synthesize the hydroxyapatite from bio-waste materials like cuttlefish bone using a precipitation method by changing reaction temperatures (room temperature, 60 °C, 70 °C, and 80 °C), and pH (9,10,11, and 12). The structure, particle size, and crystallinity of the obtained HAp were evaluated by XRD analysis. The functional groups present in the HAp nanoparticles were analyzed and confirmed by FTIR spectroscopy. The surface morphology of the particles was analyzed by using FESEM and the particle sizes were ranging from 40 to 160 nm for different pH values. The elemental composition was determined by EDAX analysis. The antibacterial activity of the sample was tested against gram-positive and gram-negative bacteria. The zone of inhibition value against gram-negative bacteria was found to be 20 ± 0.32 mm and 16 ± 0.18 mm against gram-positive bacteria for the sample with a pH value of 10. The obtained results confirmed that the optimized temperature, time, and pH are suitable for the preparation of HAp with excellent desired properties, which is employed as a better candidate for biomedical applications.

Learning from a dark brew: how traditional coffee-making can inspire the search for improved colloidal stability

The recipe for making Turkish coffee in some parts of former Yugoslavia calls for the dilution of the turbid liquid with lukewarm water just before the boiling point is reached. The enigmatic gastronomic purpose of this step notwithstanding, here it is being used as an inspiration for deriving a simple stabilization step for protocols for the synthesis of fine particle colloids. The dilution step inspired by coffee-making was performed in a protocol for the synthesis of hydroxyapatite nanoparticles by their precipitation from supersaturated alkaline aqueous solutions. The implementation of this step in the post-precipitation stage, concurrently with boiling, evidently improved the stability of the nanoparticle colloids. The stabilization effect was limited to the suspensions where the parent solution was equilibrated with the fresh precipitate and was not reproduced in colloids comprising HAp nanoparticles redispersed in deionized water. The dilution step produced a mild and counterintuitive increase in crystallinity, suggesting complex recrystallization mechanisms driven by mutually antagonistic dissolution caused by the dilution and reprecipitation caused by the heating to be responsible for the observed increase in stability. Incongruent dissolution favoring a less entropic surface order and reduced charge screening entailing the expansion of the Debye lengths were suggested as complementary mechanisms explaining the improvements in stability caused by adding this simple and economical, yet very efficacious touch to the synthesis. It is concluded that unconventional protocols in spheres other than the scientific and heritages routinely discarded as disreputable could be sources of insight relevant to a plethora of distant domains and disciplines.

Physical modification of hydroxyapatite: the drastic enhancement of both cation (Cd2+) and anion (F−) adsorption and recycling efficiency

(1) Novel physically modified (by ultrasound and freeze-drying) HAp nanoparticles (2) drastic enhancement in the Cd2+ (208%) and F− (488%) adsorption capacities along with rapid adsorption and greater recycling efficiency compared to the reported data.