Facile microwave-assisted synthesis of Te-doped hydroxyapatite nanorods and nanosheets and their characterizations for bone cement applications

Extraction and Physicochemical Characterization of Hydroxyapatites From Horse Humerus Bones of Different Ages (1, 3, 6, and 8 Years old) Calcined at Low Temperature

The aim of this work is to investigate the changes in the physicochemical properties of hydroxyapatite (HAp) extracted from horse humerus bones of different ages (1, 3, 6, and 8 years) subjected to low temperature calcination (600°C). Thermal analysis revealed significant mass loss due to water, collagen, organic compounds, carbonates, and age-related magnesium out-diffusion. Higher fat content in older bones contributed to increased mass loss. Phosphorus content remained constant across age groups, while calcium and sodium showed age-related fluctuations. Magnesium levels decreased with age, emphasizing its importance for early bone development. The Ca/P ratio deviated from the stoichiometric values due to additional ions from biogenic sources. Infrared spectroscopy identified functional groups in carbonated HAp, with changes observed before and after calcination. The full width at half maximum (FWHM) of the 961 cm-1 band decreased with age, indicating improved crystalline quality. The molar absorption coefficients provided information on the changes in molecular concentration and emphasized the differences between the age groups. X-ray analysis revealed nanocrystalline HAp in all samples, with crystallite size increasing with age. Rietveld analysis showed that the lattice parameters were affected by the presence of organic material, but the lattice constants remained stable, confirming high crystallinity independent of age. TEM analysis confirmed nanocrystalline structures, with crystallite size increasing with age. SEM images showed the characteristic porosity of calcined HAp, with particle size correlating positively with age. Calcination at 600°C preserved the nanoscale properties and microcrystal formation. Raman spectroscopy confirmed the identity of HAp, with FWHM variations indicating age-related changes in crystalline quality. EHAp1 showed increased FWHM, indicating lower crystalline quality and increased trace element content.

Use of Biomaterials in 3D Printing as a Solution to Microbial Infections in Arthroplasty and Osseous Reconstruction

The incidence of microbial infections in orthopedic prosthetic surgeries is a perennial problem that increases morbidity and mortality, representing one of the major complications of such medical interventions. The emergence of novel technologies, especially 3D printing, represents a promising avenue of development for reducing the risk of such eventualities. There are already a host of biomaterials, suitable for 3D printing, that are being tested for antimicrobial properties when they are coated with bioactive compounds, such as antibiotics, or combined with hydrogels with antimicrobial and antioxidant properties, such as chitosan and metal nanoparticles, among others. The materials discussed in the context of this paper comprise beta-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), hydroxyapatite, lithium disilicate glass, polyetheretherketone (PEEK), poly(propylene fumarate) (PPF), poly(trimethylene carbonate) (PTMC), and zirconia. While the recent research results are promising, further development is required to address the increasing antibiotic resistance exhibited by several common pathogens, the potential for fungal infections, and the potential toxicity of some metal nanoparticles. Other solutions, like the incorporation of phytochemicals, should also be explored. Incorporating artificial intelligence (AI) in the development of certain orthopedic implants and the potential use of AI against bacterial infections might represent viable solutions to these problems. Finally, there are some legal considerations associated with the use of biomaterials and the widespread use of 3D printing, which must be taken into account.

The Effect of Doping on the Electrical and Dielectric Properties of Hydroxyapatite for Medical Applications: From Powders to Thin Films

Recently, the favorable electrical properties of biomaterials have been acknowledged as crucial for various medical applications, including both bone healing and growth processes. This review will specifically concentrate on calcium phosphate (CaP)-based bioceramics, with a notable emphasis on hydroxyapatite (HA), among the diverse range of synthetic biomaterials. HA is currently the subject of extensive research in the medical field, particularly in dentistry and orthopedics. The existing literature encompasses numerous studies exploring the physical-chemical, mechanical, and biological properties of HA-based materials produced in various forms (i.e., powders, pellets, and/or thin films) using various physical and chemical vapor deposition techniques. In comparison, there is a relative scarcity of research on the electrical and dielectric properties of HA, which have been demonstrated to be essential for understanding dipole polarization and surface charge. It is noteworthy that these electrical and dielectric properties also offer valuable insights into the structure and functioning of biological tissues and cells. In this respect, electrical impedance studies on living tissues have been performed to assess the condition of cell membranes and estimate cell shape and size. The need to fill the gap and correlate the physical-chemical, mechanical, and biological characteristics with the electrical and dielectric properties could represent a step forward in providing new avenues for the development of the next-generation of high-performance HA-doped biomaterials for future top medical applications. Therefore, this review focuses on the electrical and dielectric properties of HA-based biomaterials, covering a range from powders and pellets to thin films, with a particular emphasis on the impact of the various dopants used. Therefore, it will be revealed that each dopant possesses unique properties capable of enhancing the overall characteristics of the produced structures. Considering that the electrical and dielectric properties of HA-based biomaterials have not been extensively explored thus far, the aim of this review is to compile and thoroughly discuss the latest research findings in the field, with special attention given to biomedical applications.

Microwave-assisted synthesis of praseodymium (Pr)-doped ZnS QDs such as nanoparticles for optoelectronic applications

Praseodymium (Pr)-doped ZnS nanoparticles were synthesized using a low-cost microwave-assisted technique and investigations on their structure, morphology, optical properties, Raman resonance, dielectric properties, and luminescence were conducted. Broad X-ray diffraction peaks suggested the formation of low-dimensional Pr-doped ZnS nanoparticles with a cubic structure that was validated using transmission electron microscopy (TEM)/high-resolution TEM analysis. The energy gaps were identified using diffuse reflectance spectroscopy and it was found that the values varied between 3.54eV and 3.61eV for different samples. Vibrational experiments on Pr-doped ZnS nanoparticles revealed significant Raman modes at ~270 and ~350 cm-1 that were associated with optical phonon modes that are shifted to lower wavenumbers, indicating phonon confinement in the synthesized products. The photoluminescence (PL) spectra of all samples demonstrated that the pure and Pr-doped ZnS nanoparticles were three-level laser active materials. Energy-dispersive X-ray spectroscopy and mapping study confirmed the homogeneous presence of Pr in ZnS. TEM studies showed that the particles were of very small size and in the cubic phase. The samples had high dielectric constant values between 13 and 24 and low loss values, according to the dielectric analysis. With an increase in frequency and a change in the Pr content of ZnS, an intense peak could be seen in the PL spectra at a wavelength of 360 nm, and some other peaks observed corresponded to the transition of Pr3+ . The produced nanoparticles were appropriate for optoelectronic applications due to their short dimension, high energy gap, high dielectric constant, and low loss values.

Latest Research of Doped Hydroxyapatite for Bone Tissue Engineering

Bone tissue engineering has attracted great interest in the last few years, as the frequency of tissue-damaging or degenerative diseases has increased exponentially. To obtain an ideal treatment solution, researchers have focused on the development of optimum biomaterials to be applied for the enhancement of bioactivity and the regeneration process, which are necessary to support the proper healing process of osseous tissues. In this regard, hydroxyapatite (HA) has been the most widely used material in the biomedical field due to its great biocompatibility and similarity with the native apatite from the human bone. However, HA still presents some deficiencies related to its mechanical properties, which are essential for HA to be applied in load-bearing applications. Bioactivity is another vital property of HA and is necessary to further improve regeneration and antibacterial activity. These drawbacks can be solved by doping the material with trace elements, adapting the properties of the material, and, finally, sustaining bone regeneration without the occurrence of implant failure. Considering these aspects, in this review, we have presented some general information about HA properties, synthesis methods, applications, and the necessity for the addition of doping ions into its structure. Also, we have presented their influence on the properties of HA, as well as the latest applications of doped materials in the biomedical field.

Recent Trends in Hydroxyapatite Supplementation for Osteoregenerative Purposes

Bone regeneration has gained attention in the biomedical field, which has led to the development of materials and synthesis methods meant to improve osseointegration and cellular bone activity. The properties of hydroxyapatite, a type of calcium phosphate, have been researched to determine its advantages for bone tissue engineering, particularly its biocompatibility and ability to interact with bone cells. Recently, the advantages of utilizing nanomolecules of hydroxyapatite, combined with various substances, in order to enhance and combine their characteristics, have been reported in the literature. This review will outline the cellular and molecular roles of hydroxypatite, its interactions with bone cells, and its nano-combinations with various ions and natural products and their effects on bone growth, development, and bone repair.

Synthesis, Characterization, Antibacterial, Antifungal, Antioxidant, and Anticancer Activities of Nickel-Doped Hydroxyapatite Nanoparticles

The purpose of this research was to investigate the possible antibacterial, antifungal, antioxidant, and anticancer effects of nickel (Ni2+)-doped hydroxyapatite (HAp) nanoparticles (NPs) synthesized using the sol–gel approach. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), field-emission scanning electron microscopy (FESEM), and elemental analysis were used to characterize the Ni2+-doped HApNPs. X-ray diffraction investigation showed that the nanoscale structure of Ni2+-doped HApNPs was hexagonal, with an average crystallite size of 39.91 nm. Ni2+-doped HApNPs were found to be almost spherical in form and 40–50 nm in size, as determined by FESEM analysis. According to EDAX, the atomic percentages of Ca, O, P, and Ni were 20.93, 65.21, 13.32, and 0.55, respectively. Ni2+-doped HApNPs exhibited substantial antibacterial properties when tested in vitro against several pathogens, including Escherichia coli, Shigella flexneri, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Antibacterial activity, at 50 mg tested concentration, demonstrated superior effects on G-ve bacteria than G+ve pathogens. The antifungal activity of Oidium caricae, Aspergillus flavus, and A. niger revealed a zone of inhibition of 23, 11, and 5 mm, respectively. These actions rely on the organism’s cell wall structure, size, and shape. Incorporating Ni2+ into HApNPs allows them to function as powerful antioxidants. Ni2+-doped HApNPs had a good cytotoxic impact against the HeLa cell line, which improved with increasing concentration and was detected at a 68.81 µg/mL dosage. According to the findings of this study, the Ni2+-doped HApNPs are extremely promising biologically active candidates owing to their improved functional features.

Synthesis and Characterization of Yttrium-Doped Hydroxyapatite Nanoparticles and Their Potential Antimicrobial Activity

This study reports a detailed analysis of the yttrium doping effects into hydroxyapatite (HAp) nano-structures at different amounts (e.g., 0, 1, 2.5, 5, 7.5, 10, and 15%) on the structural, spectroscopic, dielectric, and antimicrobial properties. For this purpose, seven HAp samples having the Y-contents mentioned above were prepared using the microwave-assisted sol-gel precipitation technique. The structure of synthesized samples was fully described via X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared (FTIR). Raman spectroscopy and dielectric measurements were used to characterize the spectroscopic properties. Furthermore, the samples’ antimicrobial features have been assisted through the agar disk diffusion technique. This study showed that the crystallinity decreased with the adding of Y-ions inside the HAp matrix. The Y-contents have influenced the crystallite size, lattice parameters, dislocation density, lattice strain, and unit cell volume. The surface morphology is composed of the agglomerated smaller particles. Remarkable changes in the dielectric properties were observed with the adding of Y-ions. The alternating current conductivity obeys the Jonscher’s relation. Y-doped hydroxyapatite nanoparticles have a considerable inhibitory effect against bacteria and fungi (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans). The Y-doped hydroxyapatite nanoparticles are a promising material for bone cement engineering with a potential bio-activity

A review on the synthesis and properties of hydroxyapatite for biomedical applications

Hydroxyapatite (HA or HAp) is one of the most preferred biomaterials, specifically for bone tissue engineering. HAp is available naturally and is also chemically synthesized. The properties, shape, size and crystalline structure and applications of HAp vary widely depending on the source and extraction methods used. In addition to conventional chemical approaches such as precipitation or sol-gel techniques, newer methods such as microwave synthesis and atomic-layer deposition provide an opportunity to generate HAp with desirable structure and properties. Various methods used for the synthesis of HAp have their own pros and cons. Hence, it is essential to understand the role of specific methods and conditions on the properties and structure of HAps in order to obtain HAp with properties suitable for specific applications. In addition to pure HAp, substantial efforts have been made to dope HAp with various minerals or bioentities to enhance their suitability for medical, environmental remediation and other approaches. In this review, we provide an overview of the various chemical methods used to produce HAp, properties of the HAp produced and its potential applications. Particular focus of this paper is on the co-relation between properties and processes used to synthesis HAp. This review will enable readers to quickly understand the importance of synthesis methods and conditions on the properties of HAp and choose appropriate means to generate HAp with desired properties for specific applications.

Hydroxyapatite-Supported Polyoxometalates for the Highly Selective Aerobic Oxidation of 5-Hydroxymethylfurfural or Glucose to 2,5-Diformylfuran under Atmospheric Pressure

(NH4 )5 H6 PV8 Mo4 O40 supported on hydroxyapatite (HAP) (PMo4 V8 /HAP (n)) was prepared through the ion exchange of hydroxy groups. This ion exchange favored the oxidative conversion of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF) in a one-pot cascade reaction with 96.0 % conversion and 83.8 % yield under 10 mL/min of O2 flow. PMo4 V8 /HAP (31) was used to explore the production of DFF directly from glucose with the highest yield of 47.9 % so far under atmospheric oxygen, whereas the yield of DFF increased to 54.7 % in a one-pot and two-step reaction. These results indicated that the active sites in PMo4 V8 /HAP (31) retained their activities without any interference toward one another, which enabled the production of DFF in a more cost-saving way by only using oxygen and one catalyst in a one-step reaction. Meanwhile, the rigid structure of HAP and strong interaction in PMo4 V8 /HAP (31) allowed this catalyst to be reused for at least six times with high stability and duration.

Mesoporous Mn-doped hydroxyapatite nanorods obtained via pyridinium chloride enabled microwave-assisted synthesis by utilizing Donax variabilis seashells for implant applications

Manganese-doped mesoporous hydroxyapatite (MnHAp) nanorods, a bio-apatite were synthesized via pyridinium chloride mediated microwave approach using bio-waste Donax variabilis seashells to treat orthopedic infections. This is the first report on using pyridinium chloride mediated mesoporous MnHAp nanorods synthesis. Pure and Mn doped HAp samples were examined using Raman spectroscopy, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies to confirm the prepared HAp nanorods. Furthermore, the fabrication of manganese-doped HAp was successful with the formation of a hexagonal crystal lattice without disturbing the HAp phase. It is because, at the time of synthesis, PO₄^3- ions form an electrostatic interaction with the Mn ions. Furthermore, Mn-doped HAp samples showed a reduction in their sizes of 15, 10-15, 5-10 nm width, and 80-100, 10-15, 20-30 nm length with varied pore diameters and surface area. The pure HAp, MnHAp-1, MnHAp-2, and MnHAp-3 nanorods disclose the surface area of 39.4, 18.0, 49.2, and 80.4 m² g^-1, with a pore volume of 0.0102, 0.0047, 0.0143, and 0.0447 cm³ g^-1, the corresponding pore diameter was estimated to be 6, 7, 6, and 4 nm, respectively. Moreover, antibacterial activity reveals effective bactericidal action against infections causing pathogens whereas cytotoxicity examination (MTT assay), and zebrafish results reveal their non-toxic behavior. Therefore, it is evident from the study, that rapid fabrication of mesoporous and diverse structured MnHAp nanorods could be convenient with pyridinium chloride enabled microwave-assisted method as a bactericidal biomaterial for implant applications.

Impact of Dopants on the Electrical and Optical Properties of Hydroxyapatite

This chapter deals with the effect of alternating electrical current on hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and doped HAp along with their optical response and the processes involved. The dielectric constant, permittivity and ac conductivity were analyzed to have an insight into the surface charge polarization phenomenon. Further, the magnitude and the polarity of the surface charges, microstructure, and phases also play significant role in the cell proliferation and growth on the implants. Besides, the mechanism behind the electrical properties and the healing of bone fracture are discussed. The influence of various dopants on the optical properties of HAp viz., absorbance, transmission, band gaps and defects energy levels are analyzed along with the photoluminescence and excitation independent emission. In the future outlook, the analysis of effect of doping is summarized and its impact on the next generation biomaterials are elucidated.

Microwave processing of calcium phosphate and magnesium phosphate based orthopedic bioceramics: A state-of-the-art review

The main theme of this paper is to review microwave-assisted synthesis and processing of calcium and magnesium phosphate bioceramics. Microwave processing of advanced materials has been an active field of research for the last three decades and has been already reviewed in the literature. Microwave processing of bioceramics is being pursued for almost the same period of time. Unfortunately, to the best of our knowledge, we are not aware of any comprehensive review in the literature. Our group has been a significant contributor to the field, and we feel that it is an appropriate time for reviewing the state-of-the-art of the field. The paper is divided into several sections. After rationalizing the motivation behind writing this paper in the introduction, the second section builds on some fundamental aspects of microwave-matter interactions. The third section, representing the synthesis aspects, is subdivided into five sub-sections focusing on various calcium and magnesium phosphates in both crystalline and amorphous forms. The fourth section focuses on magnesium phosphate-based bioceramics. The fifth and the sixth section describe results on the utility of microwave assistance in developing multi-functional coatings on medical implants and orthopedic cements respectively. The subsequent section reviews results on microwave sintering of calcium and magnesium phosphates. The paper concludes with remarks on unresolved issues and future directions of research. It is expected that this comprehensive review on the interdisciplinary topic will further propel the exploration of other novel applications of microwave technology in processing biomaterials by a diverse group of scientists and engineers. STATEMENT OF SIGNIFICANCE: 1. This review highlights the broad-spectrum capabilities of microwave applications in processing orthopedic bioceramics. 2. The article covers "processing" in the broadest sense of the word, comprising of material synthesis, sintering, coating formation, and setting of orthopedic cements. It also expands beyond conventional calcium phosphates to include the emergent family of magnesium phosphates. 3. In vitro/in vivo responses of microwave-processed bioceramics are discussed thus providing an integral understanding of biological aspects of these materials. 4. The comprehensive review on this interdisciplinary topic will help researchers in various disciplines to appreciate the significance and usefulness of microwaves in biomaterials processing. Further, we also believe that it will propel the exploration of other novel applications of microwave technology in the biomaterials sector.

Facile biogenic fabrication of hydroxyapatite nanorods using cuttlefish bone and their bactericidal and biocompatibility study

Cuttlefish bones are an inexpensive source of calcium carbonate, which are produced in large amounts by the marine food industry, leading to environmental contamination and waste. The nontoxicity, worldwide availability and low production cost of cuttlefish bone products makes them an excellent calcium carbonate precursor for the fabrication of hydroxyapatite. In the present study, a novel oil-bath-mediated precipitation method was introduced for the synthesis of hydroxyapatite (Hap) nanorods using cuttlefish bone powder as a precursor (CB-Hap NRs). The obtained CB-Hap NRs were investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques to evaluate their physicochemical properties. The crystallite size (20.86 nm) obtained from XRD data and the elemental analysis (Ca/P molar ratio was estimated to be 1.6) showed that the Hap NRs are similar to that of natural human bone (≈1.67). Moreover, the FTIR data confirmed the presence of phosphate as a functional group and the TGA data revealed the thermal stability of Hap NRs. In addition, the antibacterial study showed a significant inhibitory effect of CB-Hap NRs against S. aureus (zone of inhibition - 14.5 ± 0.5 mm) and E. coli (13 ± 0.5 mm), whereas the blood compatibility test showed that the CB-Hap NRs exhibited a concentration-mediated hemolytic effect. These biogenic CB-Hap NRs with improved physicochemical properties, blood compatibility and antibacterial efficacy could be highly beneficial for orthopedic applications in the future.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Novel and facile microwave-assisted synthesis of Mo-doped hydroxyapatite nanorods: Characterization, gamma absorption coefficient, and bioactivity

In the current work, the authors report the microwave-assisted synthesis Molybdenum-doped (from 0.05 to 5wt%) hydroxyapatite (HAp) for the first time. The morphology of Mo-doped HAp is nanorods of diameter in the range of 25-70nm and length in the range of 25nm to 200nm. The good crystalline nature was confirmed from X-ray diffraction patterns and also lattice parameters, grain size, strain and dislocation density were determined. The crystallite size was found to be in the range 16 to 30nm and crystallinity was found to be enhanced from 0.5 to 0.7 with doping. The field emission SEM micrographs show that the morphology of the synthesized nanostructures of pure and Mo-doped HAp are nanorods of few nanometers. The vibrational modes were identified using the FT-Raman and FT-IR spectroscopy. The dielectric properties were studied and the AC electrical conductivity was found to be increased with increasing the concentration of Mo ions doping in HAp. Moreover, antimicrobial studies were also carried out to understand the anti-bacterial and anti-fungi properties. The results suggest that it may be a good bio-ceramics material for bio-medical applications. Mo-doped HAp was subjected to the gamma irradiation produced from Cs-137 (662keV) and its related parameters such as linear absorption coefficient, the half-value layer (HVL) and the tenth value layer TVL were calculated and analyzed.