Intrinsically superparamagnetic Fe-hydroxyapatite nanoparticles positively influence osteoblast-like cell behaviour

Copper Versatility in Hydroxyapatite: Valence States, Clusters, and Optical Absorption Properties

The solid-state reaction between a stoichiometric hydroxyapatite (HA) and CuO at temperatures above 1100 °C produces pure Cux-HA phases for x ≤ 0.7 with the general formula Ca10CuIx(PO4)6(OH)2-xOx. The Cu atoms are located at the center of the hexagonal tunnels between two hydroxyl ligands, as determined by Fourier analysis based on XRD data. During heat treatment, the reduction of Cu2+ ions into Cu+ is concomitant with the stabilization of copper in HA in the hexagonal tunnel. The incorporation of monovalent copper within the apatite, as revealed by XANES spectroscopy, explains the violet color of the samples. The incorporation of Cu+ ions, by substitution of a hydrogen atom by copper(I), results in the formation of linear O-Cu-O chains where the majority of which are isolated for x ≤ 0.3. In addition, the EXAFS investigation showed, thanks to the linear geometry of these clusters that results in multiple diffusion effects, the existence of [CuO]n chains with n ≥ 2, which only appear clearly for higher copper contents x ≥ 0.5. The strong covalency of the Cu-O bond in such a dumbbell configuration would lead to strong hybridization between the 3d and 4s orbitals of copper and the 2p orbitals of oxygen, as illustrated by ESR signals. In the case of Cu-doped HA prepared by coprecipitation and annealed at a lower temperature (T ≤ 600 °C), copper substitutes calcium according to the theoretical formula Ca10-xCux(PO4)6(OH)2, mainly at the Ca(2) site. This local environment is in line with the Jahn-Teller distortion induced by the Cu2+ ion (as evidenced by UV-vis-NIR, XPS, and XANES-EXAFS spectroscopy analyses) and also allows copper-copper interactions from one site to another, as observed by ESR spectroscopy. This versatility of copper in HA gives it optical properties that change from a violet color with near-IR absorption to a blue hue. In all cases, Cu-O-Cu interactions persist whatever the valence state, and heat treatment induces a redox phenomenon, with copper exchanging between two sites close to each other.

Exploring the effect of hydroxyapatite nanoparticle shape on red blood cells and blood coagulation

Aim: In this study, we evaluated the effects of two types of hydroxyapatite (HAP) nanoparticles, sharing the same surface chemistry but differing in shape, on the biological characteristics of plasma, platelets and red blood cells.Materials & methods: Initially, two different shapes (rod-shaped and sphere-shaped) of HAPs were characterized. These HAPs were then co-cultured with plasma and red blood cells to examine their impact on coagulation and hemolysis. The impact of HAPs on white blood cells count in mice were evaluated following gavage and tail vein injection.Results: Sphere-shaped HAP is more likely to adsorb onto platelet surfaces, while rod-shaped HAP is more likely to cause hemolysis. Although there are differences in the in vitro experimental results between sphere-shaped HAP and rod-shaped HAP, both types demonstrate good blood compatibility at a 20 mM concentration. Furthermore, in vivo experiments showed that sphere-shaped nano-HAP induced a more pronounced increase in white blood cell count, suggesting that it may exhibit greater toxicity.Conclusion: While differences exist in the blood compatibility test results between the two HAPs, these differences are minimal, with both results falling within a safe range. Overall, HAP demonstrates excellent blood compatibility.

Enhancement in the induction heating efficacy of sol-gel derived SiO2-CaO-Na2O-P2O5 bioglass-ceramics by incorporating magnetite nanoparticles

Magnetite (Fe3O4) nanoparticle (MNP)-substituted glass-ceramic (MSGC) powders with compositions of (45 - x)SiO2-24.5CaO-24.5Na2O-6P2O5-xFe3O4 (x = 5, 8, and 10 wt%) have been prepared by a sol-gel route by introducing Fe3O4 nanoparticles during the synthesis. The X-ray diffraction patterns of the as-prepared MSGC nanopowders revealed the presence of combeite (Na2Ca2Si3O9), magnetite, and sodium nitrate (NaNO3) crystalline phases. Heat-treatment up to 700 °C for 1 h resulted in the complete dissolution of NaNO3 along with partial conversion of magnetite into hematite (α-Fe2O3). Optimal heat-treatment of the MSGC powders at 550 °C for 1 h yielded the highest relative percentage of magnetite (without hematite) with some residual NaNO3. The saturation magnetization and heat generation capacity of the MSGC fluids increased with an increase in the MNP content. The in vitro bioactivity of the MSGC pellets was evaluated by monitoring the pH and the formation of a hydroxyapatite surface layer upon immersion in modified simulated body fluid. Proliferation of MG-63 osteoblast cells indicated that all of the MSGC compositions were non-toxic and MSGC with 10 wt% MNPs exhibited extraordinarily high cell viability. The MSGC with 10 wt% MNPs demonstrated optimal characteristics in terms of cell viability, magnetic properties, and induction heating capacity, which surpass those of the commercial magnetic fluid FluidMag-CT employed in hyperthermia treatment.

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.

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.

Enhancement of physicochemical characterization of nanocomposites on Ag+/Fe2+ codoped hydroxyapatite for antibacterial and anticancer properties

The synthesis of nanosized Ag+/Fe2+ codoped hydroxyapatite (HAp) nanocomposite materials with antibacterial and anticancer characteristics is highly attractive for advancing the development of biological applications. The objective of this study was to evaluate the antibacterial and anticancer characteristics of Ag+/Fe2+ codoped hydroxyapatite materials. We developed a facile chemical precipitation method for the fabrication of Ag+/Fe2+:HAp nanocomposites. The developed Ag+/Fe2+:HAp nanocomposite materials were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). For measuring the size of Ag+/Fe2+:HAp nanocomposites, dynamic light scattering (DLS) is an advantageous method. The chemical states and chemical composition of Ag+/Fe2+:HAp were observed by X-ray photoelectron spectroscopy (XPS) analysis. In addition, the antibacterial efficacy of Ag+/Fe2+:HAps against Gram-positive (S.aureus), and Gram-negative (S.typhi, and E.Coli) microorganisms is examined in this current study. Ag+/Fe2+:HAp nanocomposite materials have been evaluated for biological toxicity in vitro, and the results showed that the particles were excellent at identifying and killing cancer cells. In this respect, Ag+/Fe2+:HAp nanocomposites significantly impact human colon cancer cells (HT29) while have no effect on normal fibroblast cells (L929).

Environmental Hazards of Nanobiomaterials (Hydroxyapatite-Based NMs)-A Case Study with Folsomia candida-Effects from Long Term Exposure

Hydroxyapatite (HA) is a calcium phosphate used in many fields, including biomedical applications. In particular, ion-doped HA nanomaterials (nHA) are developed for their increased bioactivity, particularly in the fields of regenerative medicine and nanomedicine. In this study, we assessed the ecotoxicological impact of five nHA materials: a synthesized calcium hydroxyapatite (CaP-HA), superparamagnetic iron-doped hydroxyapatite (Fe-HA), titanium-doped hydroxyapatite (Ti-HA), alginate/titanium-doped hydroxyapatite hybrid composite (Ti-HA-Alg), and a commercial HA. The soil ecotoxicology model species Folsomia candida (Collembola) was used, and besides the standard reproduction test (28 days), an extension to the standard for one more generation was performed (56 days). Assessed endpoints included the standard survival and reproduction, and additionally, growth. Exposure via the standard (28 days) did not cause toxicity, but reproduction increased in commercial HA (significantly at 320 mg HA/kg) whereas via the extension (56 days) it decreased in all tested concentrations. Juveniles' size (56 days) was reduced in all tested nHA materials, except commercial HA. nHA materials seem to trigger a compromise between reproduction and growth. Long-term effects could not be predicted based on the standard shorter exposure; hence, the testing of at least two generations (56 days) is recommended to assess the toxicity of nanomaterials, particularly in F. candida. Further, we found that the inclusion of size as additional endpoint is highly relevant.

Safer and Sustainable-by-Design Hydroxyapatite Nanobiomaterials for Biomedical Applications: Assessment of Environmental Hazards

Developments in the nanotechnology area occur ensuring compliance with regulatory requirements, not only in terms of safety requirements, but also to meet sustainability goals. Hence, safer and sustainable-by-design (SSbD) materials are also aimed for during developmental process. Similar to with any new materials their safety must be assessed. Nanobiomaterials can offer large advantages in the biomedical field, in areas such as tissue repair and regeneration, cancer therapy, etc. For example, although hydroxyapatite-based nanomaterials (nHA) are among the most studied biomaterials, its ecotoxicological effects are mostly unknown. In the present study we investigated the toxicity of seven nHA-based materials, covering both different biomedical applications, e.g., iron-doped hydroxyapatite designed for theragnostic applications), hybrid collagen/hydroxyapatite composites, designed for bone tissue regeneration, and SSbD alternative materials such as titanium-doped hydroxyapatite/alginate composite, designed as sunscreen. The effects were assessed using the soil model Enchytraeus crypticus (Oligochaeta) in the natural standard LUFA 2.2 soil. The assessed endpoints included the 2, 3 and 4 days avoidance behavior (short-term), 28 days survival, size and reproduction (long term based on the OECD standard reproduction test), and 56 days survival and reproduction (longer-term OECD extension). Although overall results showed little to no toxicity among the tested nHA, there was a significant decrease in animals' size for Ti-containing nHA. Moreover, there was a tendency for higher toxicity at the lowest concentrations (i.e., 100 mg/kg). This requires further investigation to ensure safety.

Smart biomaterials and their potential applications in tissue engineering

Smart biomaterials have been rapidly advancing ever since the concept of tissue engineering was proposed. Interacting with human cells, smart biomaterials can play a key role in novel tissue morphogenesis. Various aspects of biomaterials utilized in or being sought for the goal of encouraging bone regeneration, skin graft engineering, and nerve conduits are discussed in this review. Beginning with bone, this study summarizes all the available bioceramics and materials along with their properties used singly or in conjunction with each other to create scaffolds for bone tissue engineering. A quick overview of the skin-based nanocomposite biomaterials possessing antibacterial properties for wound healing is outlined along with skin regeneration therapies using infrared radiation, electrospinning, and piezoelectricity, which aid in wound healing. Furthermore, a brief overview of bioengineered artificial skin grafts made of various natural and synthetic polymers has been presented. Finally, by examining the interactions between natural and synthetic-based biomaterials and the biological environment, their strengths and drawbacks for constructing peripheral nerve conduits are highlighted. The description of the preclinical outcome of nerve regeneration in injury healed with various natural-based conduits receives special attention. The organic and synthetic worlds collide at the interface of nanomaterials and biological systems, producing a new scientific field including nanomaterial design for tissue engineering.

Simultaneous Substitution of Fe and Sr in Beta-Tricalcium Phosphate: Synthesis, Structural, Magnetic, Degradation, and Cell Adhesion Properties

β-tricalcium phosphate is a promising bone graft substitute material with biocompatibility and high osteoinductivity. However, research on the ideal degradation and absorption for better clinical application remains a challenge. Now, we focus on modifying physicochemical properties and improving biological properties through essential ion co-substitution (Fe and Sr) in β-TCPs. Fe- and Sr-substituted and Fe/Sr co-substituted β-TCP were synthesized by aqueous co-precipitation with substitution levels ranging from 0.2 to 1.0 mol%. The β-TCP phase was detected by X-ray diffraction and Fourier transform infrared spectroscopy. Changes in Ca–O and P–O bond lengths of the co-substituted samples were observed through X-ray photoelectron spectroscopy. The results of VSM represent the M-H graph having a combination of diamagnetic and ferromagnetic properties. A TRIS–HCl solution immersion test showed that the degradation and resorption functions act synergistically on the surface of the co-substituted sample. Cell adhesion tests demonstrated that Fe enhances the initial adhesion and proliferation behavior of hDPSCs. The present work suggests that Fe and Sr co-substitution in β-TCP can be a candidate for promising bone graft materials in tissue engineering fields. In addition, the possibility of application of hyperthermia for cancer treatment can be expected.

Effects of Zinc, Magnesium, and Iron Ions on Bone Tissue Engineering

Large-sized bone defects are a great challenge in clinics and considerably impair the quality of patients' daily life. Tissue engineering strategies using cells, scaffolds, and bioactive molecules to regulate the microenvironment in bone regeneration is a promising approach. Zinc, magnesium, and iron ions are natural elements in bone tissue and participate in many physiological processes of bone metabolism and therefore have great potential for bone tissue engineering and regeneration. In this review, we performed a systematic analysis on the effects of zinc, magnesium, and iron ions in bone tissue engineering. We focus on the role of these ions in properties of scaffolds (mechanical strength, degradation, osteogenesis, antibacterial properties, etc.). We hope that our summary of the current research achievements and our notifications of potential strategies to improve the effects of zinc, magnesium, and iron ions in scaffolds for bone repair and regeneration will find new inspiration and breakthroughs to inspire future research.

Surface and Structural Studies of Age-Related Changes in Dental Enamel: An Animal Model

In the animal kingdom, continuously erupting incisors provided an attractive model for studying the enamel matrix and mineral composition of teeth during development. Enamel, the hardest mineral tissue in the vertebrates, is a tissue sensitive to external conditions, reflecting various disturbances in its structure. The developing dental enamel was monitored in a series of incisor samples extending the first four weeks of postnatal life in the spiny mouse. The age-dependent changes in enamel surface morphology in the micrometre and nanometre-scale and a qualitative assessment of its mechanical features were examined by applying scanning electron microscopy (SEM) and atomic force microscopy (AFM). At the same time, structural studies using XRD and vibrational spectroscopy made it possible to assess crystallinity and carbonate content in enamel mineral composition. Finally, a model for predicting the maturation based on chemical composition and structural factors was constructed using artificial neural networks (ANNs). The research presented here can extend the existing knowledge by proposing a pattern of enamel development that could be used as a comparative material in environmental, nutritional, and pharmaceutical research.

Functional role of inorganic trace elements in dentin apatite tissue-Part 1: Mg, Sr, Zn, and Fe

Many essential elements exist in nature with significant influence on dentin and bone apatite tissue. Hydroxyapatite (HAp) is the major inorganic crystalline structure of dentin that provides a site for various physiological functions such as surface layer ion exchange. Decades of apatite research have shown that enamel is a high-substituted crystalline apatite, but recent findings suggest that dentin apatite may play a more important role in regulating ion exchange as well as mineral crystallinity. This article is the first part of a review series on the functional role of inorganic trace elements including magnesium, strontium, zinc, and iron in dentin hydroxyapatite. The morphology, physiology, crystallinity, and solubility of these elements as they get substituted into the HAp lattice are extensively discussed. An electronic search was performed on the role of these elements in dentin apatite from January 2007 to September 2021. The relationship between different elements and their role in the mineral upkeep of dentin apatite was evaluated. Several studies recognized the role of these elements in dentinal apatite composition and its subsequent effects on morphology, crystallinity, and solubility. These elements are of great importance in physiological processes and an essential part of living organisms. Magnesium and strontium stimulate osteoblast activity, while zinc can improve overall bone quality with its antibacterial properties. Iron nanoparticles are also vital in promoting bone tissue growth as they donate or accept electrons in redox reactions. Thus, understanding how these elements impact dentin apatite structure is of great clinical significance.

Engineered Magnetic Nanocomposites to Modulate Cellular Function

Magnetic nanoparticles (MNPs) have various applications in biomedicine, including imaging, drug delivery and release, genetic modification, cell guidance, and patterning. By combining MNPs with polymers, magnetic nanocomposites (MNCs) with diverse morphologies (core-shell particles, matrix-dispersed particles, microspheres, etc.) can be generated. These MNCs retain the ability of MNPs to be controlled remotely using external magnetic fields. While the effects of these biomaterials on the cell biology are still poorly understood, such information can help the biophysical modulation of various cellular functions, including proliferation, adhesion, and differentiation. After recalling the basic properties of MNPs and polymers, and describing their coassembly into nanocomposites, this review focuses on how polymeric MNCs can be used in several ways to affect cell behavior. A special emphasis is given to 3D cell culture models and transplantable grafts, which are used for regenerative medicine, underlining the impact of MNCs in regulating stem cell differentiation and engineering living tissues. Recent advances in the use of MNCs for tissue regeneration are critically discussed, particularly with regard to their prospective involvement in human therapy and in the construction of advanced functional materials such as magnetically operated biomedical robots.

Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller.

Regulation of stem cell fate using nanostructure-mediated physical signals

One of the major issues in tissue engineering is regulation of stem cell differentiation toward specific lineages. Unlike biological and chemical signals, physical signals with adjustable properties can be applied to stem cells in a timely and localized manner, thus making them a hot topic for research in the fields of biomaterials, tissue engineering, and cell biology. According to the signals sensed by cells, physical signals used for regulating stem cell fate can be classified into six categories: mechanical, light, thermal, electrical, acoustic, and magnetic. In most cases, external macroscopic physical fields cannot be used to modulate stem cell fate, as only the localized physical signals accepted by the surface receptors can regulate stem cell differentiation via nanoscale fibrin polysaccharide fibers. However, surface receptors related to certain kinds of physical signals are still unknown. Recently, significant progress has been made in the development of functional materials for energy conversion. Consequently, localized physical fields can be produced by absorbing energy from an external physical field and subsequently releasing another type of localized energy through functional nanostructures. Based on the above concepts, we propose a methodology that can be utilized for stem cell engineering and for the regulation of stem cell fate via nanostructure-mediated physical signals. In this review, the combined effect of various approaches and mechanisms of physical signals provides a perspective on stem cell fate promotion by nanostructure-mediated physical signals. We expect that this review will aid the development of remote-controlled and wireless platforms to physically guide stem cell differentiation both in vitro and in vivo, using optimized stimulation parameters and mechanistic investigations while driving the progress of research in the fields of materials science, cell biology, and clinical research.

Magnetic and radio-labeled bio-hybrid scaffolds to promote and track in vivo the progress of bone regeneration

This work describes the preparation, characterization and functionalization with magnetic nanoparticles of a bone tissue-mimetic scaffold composed of collagen and hydroxyapatite obtained through a biomineralization process. Bone remodeling takes place over several weeks and the possibility to follow it in vivo in a quick and reliable way is still an outstanding issue. Therefore, this work aims to produce an implantable material that can be followed in vivo during bone regeneration by using the existing non-invasive imaging techniques (MRI). To this aim, suitably designed biocompatible SPIONs were linked to the hybrid scaffold using two different strategies, one involving naked SPIONs (nMNPs) and the other using coated and activated SPIONs (MNPs) exposing carboxylic acid functions allowing a covalent attachment between MNPs and collagen molecules. Physico-chemical characterization was carried out to investigate the morphology, crystallinity and stability of the functionalized materials followed by MRI analyses and evaluation of a radiotracer uptake ([^99mTc]Tc-MDP). Cell proliferation assays in vitro were carried out to check the cytotoxicity and demonstrated no side effects due to the SPIONs. The achieved results demonstrated that the naked and coated SPIONs are more homogeneously distributed in the scaffold when incorporated during the synthesis process. This work demonstrated a suitable approach to develop a biomaterial for bone regeneration that allows the monitoring of the healing progress even for long-term follow-up studies.

Bioactive Calcium Phosphate-Based Composites for Bone Regeneration

Calcium phosphates (CaPs) are widely accepted biomaterials able to promote the regeneration of bone tissue. However, the regeneration of critical-sized bone defects has been considered challenging, and the development of bioceramics exhibiting enhanced bioactivity, bioresorbability and mechanical performance is highly demanded. In this respect, the tuning of their chemical composition, crystal size and morphology have been the matter of intense research in the last decades, including the preparation of composites. The development of effective bioceramic composite scaffolds relies on effective manufacturing techniques able to control the final multi-scale porosity of the devices, relevant to ensure osteointegration and bio-competent mechanical performance. In this context, the present work provides an overview about the reported strategies to develop and optimize bioceramics, while also highlighting future perspectives in the development of bioactive ceramic composites for bone tissue regeneration.

Facile synthesis of biocompatible magnetic titania nanorods for T1-magnetic resonance imaging and enhanced phototherapy of cancers

Cancer treatment has been recently energized by nanomaterials that simultaneously offer diagnostic and therapeutic effects. Among the imaging and treatment modalities in frontline research today, magnetic resonance imaging (MRI) and phototherapy have gained significant interest due to their noninvasiveness among other intriguing benefits. Herein, Fe(iii) was adsorbed on titanium dioxide to develop magnetic Fe-TiO₂ nanocomposites (NCs) which leverage the Fe moiety in a double-edge-sword approach to: (i) achieve T₁-weighted MRI contrast enhancement, and (ii) improve the well-established photodynamic therapeutic efficacy of TiO₂ nanoparticles. Interestingly, the proposed NCs exhibit classic T₁ MRI contrast agent properties (r₁ = 1.16 mM^-1 s^-1) that are comparable to those of clinically available contrast agents. Moreover, the NCs induce negligible cytotoxicity in traditional methods and show remarkable support to the proliferation of intestine organoids, an advanced toxicity evaluation system based on three-dimensional organoids, which could benefit their potential safe application for in vivo cancer theranostics. Aided by the Fenton reaction contribution of the Fe component of the Fe-TiO₂ NCs, considerable photo-killing of cancer cells is achieved upon UV irradiation at very low (2.5 mW cm^-2) intensity in typical cancer PDT. It is therefore expected that this study will guide the engineering of other biocompatible magnetic titania-based nanosystems with multi-faceted properties for biomedical applications.

Nature-Inspired Unconventional Approaches to Develop 3D Bioceramic Scaffolds with Enhanced Regenerative Ability

Material science is a relevant discipline in support of regenerative medicine. Indeed, tissue regeneration requires the use of scaffolds able to guide and sustain the natural cell metabolism towards tissue regrowth. This need is particularly important in musculoskeletal regeneration, such as in the case of diseased bone or osteocartilaginous regions for which calcium phosphate-based scaffolds are considered as the golden solution. However, various technological barriers related to conventional ceramic processing have thus far hampered the achievement of biomimetic and bioactive scaffolds as effective solutions for still unmet clinical needs in orthopaedics. Driven by such highly impacting socioeconomic needs, new nature-inspired approaches promise to make a technological leap forward in the development of advanced biomaterials. The present review illustrates ion-doped apatites as biomimetic materials whose bioactivity resides in their unstable chemical composition and nanocrystallinity, both of which are, however, destroyed by the classical sintering treatment. In the following, recent nature-inspired methods preventing the use of high-temperature treatments, based on (i) chemically hardening bioceramics, (ii) biomineralisation process, and (iii) biomorphic transformations, are illustrated. These methods can generate products with advanced biofunctional properties, particularly biomorphic transformations represent an emerging approach that could pave the way to a technological leap forward in medicine and also in various other application fields.

Medicated Hydroxyapatite/Collagen Hybrid Scaffolds for Bone Regeneration and Local Antimicrobial Therapy to Prevent Bone Infections

Microbial infections occurring during bone surgical treatment, the cause of osteomyelitis and implant failures, are still an open challenge in orthopedics. Conventional therapies are often ineffective and associated with serious side effects due to the amount of drugs administered by systemic routes. In this study, a medicated osteoinductive and bioresorbable bone graft was designed and investigated for its ability to control antibiotic drug release in situ. This represents an ideal solution for the eradication or prevention of infection, while simultaneously repairing bone defects. Vancomycin hydrochloride and gentamicin sulfate, here considered for testing, were loaded into a previously developed and largely investigated hybrid bone-mimetic scaffold made of collagen fibers biomineralized with magnesium doped-hydroxyapatite (MgHA/Coll), which in the last ten years has widely demonstrated its effective potential in bone tissue regeneration. Here, we have explored whether it can be used as a controlled local delivery system for antibiotic drugs. An easy loading method was selected in order to be reproducible, quickly, in the operating room. The maintenance of the antibacterial efficiency of the released drugs and the biosafety of medicated scaffolds were assessed with microbiological and in vitro tests, which demonstrated that the MgHA/Coll scaffolds were safe and effective as a local delivery system for an extended duration therapy—promising results for the prevention of bone defect-related infections in orthopedic surgeries.

Internal structures and mechanical properties of magnetic gels and suspensions

We present results of theoretical and computer study of linear chain-like and complicated labyrinth structures in magnetic gels and suspensions as well as effect of these internal structures on macroscopic elastic properties of the composites. Our results show that at a certain threshold deformation, the structures experience a rupture which provokes a fall down of the macroscopic elastic stress, induced by the deformation. This effect is detected for both shear and tensile deformations. The results of calculations are compared with experimental data’s.

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

This review presents the actual state of knowledge and recent research results on the magnetic composite synthesized from iron oxide (γ-Fe₂O₃ or Fe₃O₄) and hydroxyapatite. It can be obtained applying some methods, i.e. chemical precipitation, hydrothermal, sol-gel, and biomimetic or combined techniques which exhibit characteristic properties affecting the form of the prepared product. More specific details are discussed in this paper. A comparison of the discussed synthesis methods is presented. On the basis of selected publications, a comparison of the results of the analysis by XRD, FTIR, SEM and EDX methods for hydroxyapatite with a magnetic core was also presented. Moreover, the characteristics large adsorption capacity and specific area allow employing nanocomposites as adsorbents particularly in removal of toxic metal ions. Nowadays this issue is extremely vital due to large amounts of pollutants in the environment and greater ecological awareness of people. Moreover, magnetic hydroxyapatite can be also applied as a catalyst in various syntheses or oxidation reactions as well as in medicine in magnetic resonance imaging, hyperthermia treatment, drug delivery and release, bone regeneration or cell therapy.

Nanotechnological approach and bio-inspired materials to face degenerative diseases in aging

The aging of the world population is increasingly claimed as an alarming situation, since an ever-raising number of persons in advanced age but still physically active is expected to suffer from invalidating and degenerative diseases. The impairment of the endogenous healing potential provoked by the aging requires the development of more effective and personalized therapies, based on new biomaterials and devices able to direct the cell fate to stimulate and sustain the regrowth of damaged or diseased tissues. To obtain satisfactory results, also in cases where the cell senescence, typical of the elderly, makes the regeneration process harder and longer, the new solutions have to possess excellent ability to mimic the physiological extracellular environment and thus exert biomimetic stimuli on stem cells. To this purpose, the "biomimetic concept" is today recognized as elective to fabricate bioactive and bioresorbable devices such as hybrid osteochondral scaffolds and bioactive bone cements closely resembling the natural hard tissues and with enhanced regenerative ability. The review will illustrate some recent results related to these new biomimetic materials developed for application in different districts of the musculoskeletal system, namely bony, osteochondral and periodontal regions, and the spine. Further, it will be shown how new bioactive and superparamagnetic calcium phosphate nanoparticles can give enhanced results in cardiac regeneration and cancer therapy. Since tissue regeneration will be a major demand in the incoming decades, the high potential of biomimetic materials and devices is promising to significantly increase the healing rate and improve the clinical outcomes even in aged patients.

Mesoporous Iron(III)-Doped Hydroxyapatite Nanopowders Obtained via Iron Oxalate

Mesoporous hydroxyapatite (HA) and iron(III)-doped HA (Fe-HA) are attractive materials for biomedical, catalytic, and environmental applications. In the present study, the nanopowders of HA and Fe-HA with a specific surface area up to 194.5 m²/g were synthesized by a simple precipitation route using iron oxalate as a source of Fe³⁺ cations. The influence of Fe³⁺ amount on the phase composition, powders morphology, Brunauer–Emmett–Teller (BET) specific surface area (S), and pore size distribution were investigated, as well as electron paramagnetic resonance and Mössbauer spectroscopy analysis were performed. According to obtained data, the Fe³⁺ ions were incorporated in the HA lattice, and also amorphous Fe oxides were formed contributed to the gradual increase in the S and pore volume of the powders. The Density Functional Theory calculations supported these findings and revealed Fe³⁺ inclusion in the crystalline region with the hybridization among Fe-3d and O-2p orbitals and a partly covalent bond formation, whilst the inclusion of Fe oxides assumed crystallinity damage and rather occurred in amorphous regions of HA nanomaterial. In vitro tests based on the MG-63 cell line demonstrated that the introduction of Fe³⁺ does not cause cytotoxicity and led to the enhanced cytocompatibility of HA.

Chemo-Mechanical Modulation of Cell Motions Using DNA Nanosprings

Cell motions such as migration and change in cellular morphology are essential activities for multicellular organism in response to environmental stimuli. These activities are a result of coordinated clustering/declustering of integrin molecules at the cell membrane. Here, we prepared DNA origami nanosprings to modulate cell motions by targeting the clustering of integrin molecules. Each nanospring was modified with arginyl-glycyl-aspartic acid (RGD) domains with a spacing such that when the nanospring is coiled, the RGD ligands trigger the clustering of integrin molecules, which changes cell motions. The coiling or uncoiling of the nanospring is controlled, respectively, by the formation or dissolution of an i-motif structure between neighboring piers in the DNA origami nanodevice. At slightly acidic pH (<6.5), the folding of the i-motif leads to the coiling of the nanospring, which inhibits the motion of HeLa cells. At neutrality (pH 7.4), the unfolding of the i-motif allows cells to resume mechanical movement as the nanospring becomes uncoiled. We anticipate that this pH-responsive DNA nanoassembly is valuable to inhibit the migration of metastatic cancer cells in acidic extracellular environment. Such a chemo-mechanical modulation provides a new mechanism for cells to mechanically respond to endogenous chemical cues.

Development of Iron-Doped Hydroxyapatite Coatings

It is known that iron is found as a trace element in bone tissue, the main inorganic constituent of which is hydroxyapatite. Therefore, iron-doped hydroxyapatite (HApFe) materials could be new alternatives for many biomedical applications. A facile dip coating process was used to elaborate the iron-doped hydroxyapatite (HApFe) nanocomposite coatings. The HApFe suspension used to prepare the coatings was achieved using a co-precipitation method, which was adapted in the laboratory. The quality of the HApFe suspension was assessed through dynamic light scattering (DLS), ultrasonic measurements, and zeta potential values. The hydroxyapatite XRD patterns were observed in the HApFe nanocomposite with no significant shifting of peak positions, thus suggesting that the incorporation of iron did not significantly modify the hydroxyapatite structure. The morphology of the HApFe nanoparticles was evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used in order to investigate the morphologies of HApFe particles and coatings, while their chemical compositions were assessed using energy-dispersive X-ray spectroscopy (EDS). The SEM results suggested that the HApFe consists mainly of spherical nanometric particles and that the surfaces of the coatings are continuous and homogeneous. Additionally, the EDS spectra highlighted the purity of the samples and confirmed the presence of calcium, phosphorous, and iron in the analyzed sample. The in vitro cytotoxicity of the HApFe suspensions and coatings was evidenced using osteoblast cells. The MTT assay showed that both the HApFe suspensions and coatings exhibited biocompatible properties.

Bio-inspired polymeric iron-doped hydroxyapatite microspheres as a tunable carrier of rhBMP-2

Hybrid superparamagnetic microspheres with bone-like composition, previously developed by a bio-inspired assembling/mineralization process, are evaluated for their ability to uptake and deliver recombinant human bone morphogenetic protein-2 (rhBMP-2) in therapeutically-relevant doses along with prolonged release profiles. The comparison with hybrid non-magnetic and with non-mineralized microspheres highlights the role of nanocrystalline, nanosize mineral phases when they exhibit surface charged groups enabling the chemical linking with the growth factor and thus moderating the release kinetics. All the microspheres show excellent osteogenic ability with human mesenchymal stem cells whereas the hybrid mineralized ones show a slow and sustained release of rhBMP-2 along 14 days of soaking into cell culture medium with substantially bioactive effect, as reported by assay with C2C12 BRE-Luc cell line. It is also shown that the release extent can be modulated by the application of pulsed electromagnetic field, thus showing the potential of remote controlling the bioactivity of the new micro-devices which is promising for future application of hybrid biomimetic microspheres in precisely designed and personalized therapies.

Nanostructured Biomaterials for Bone Regeneration

This review article addresses the various aspects of nano-biomaterials used in or being pursued for the purpose of promoting bone regeneration. In the last decade, significant growth in the fields of polymer sciences, nanotechnology, and biotechnology has resulted in the development of new nano-biomaterials. These are extensively explored as drug delivery carriers and as implantable devices. At the interface of nanomaterials and biological systems, the organic and synthetic worlds have merged over the past two decades, forming a new scientific field incorporating nano-material design for biological applications. For this field to evolve, there is a need to understand the dynamic forces and molecular components that shape these interactions and influence function, while also considering safety. While there is still much to learn about the bio-physicochemical interactions at the interface, we are at a point where pockets of accumulated knowledge can provide a conceptual framework to guide further exploration and inform future product development. This review is intended as a resource for academics, scientists, and physicians working in the field of orthopedics and bone repair.

Mimicking Natural Microenvironments: Design of 3D-Aligned Hybrid Scaffold for Dentin Regeneration

Tooth loss is a common consequence of a huge number of causes and can decrease the quality of humans’ life. Tooth is a complex organ composed of soft connective tissues and mineralized tissues of which dentin is the most voluminous component whose formation is regulated by a very complex process displaying several similarities with osteogenesis. Calcium phosphates, in particular hydroxyapatite (HA), is the phase present in higher amount into the structure of dentin, characterized by microscopic longitudinal dentinal tubules. To address the challenge of dental tissue regeneration, here we propose a novel biomimetic approach, to design hybrid scaffolds resembling the physico-chemical features of the natural mineralized tissues, suitable to recreate an appropriate microenvironment that stimulates cell colonization and proliferation, therefore effective for improving regenerative approach in dental applications. Biomineralization is the adopted synthesis as a nature inspired process consisting in the nucleation of magnesium-doped-hydroxyapatite (MgHA) nanocrystals on the gelatin (Gel) matrix generating hybrid flakes (Gel/MgHA) featured by a Gel:MgHA weight ratio close to 20:80 and size of 50–70 μm. Chemical and topotactic constrains affect the formation of MgHA mineral phase on the organic template, generating quasi-amorphous MgHA as revealed by XRD analysis and Ca/P ratio lower than 1.67, resembling the chemical and biological features of the natural apatite. The Gel/MgHA was then merged into the polymeric blend made of chitosan (Chit) and Gel to obtain a 3D porous scaffold with polymers: MgHA weight ratio of 40:60 and featured by an aligned porous structure as obtained by controlled freeze-drying process. The overall composite shows a swelling ratio of about 15 times after 6 h in PBS. The chemical stability was assured by means of a dehydrothermal cross-linking treatment (DHT) keeping the degradation lower than 20% after 28 days, while cell adhesion and proliferation were evaluated using a mouse fibroblast cell line.

Analysis of the osteogenic and mechanical characteristics of iron (Fe2+/Fe3+)-doped β‑calcium pyrophosphate

The calcium phosphate is the main mineral constituent of bone. Although there has been significant amount of research on finding ideal synthetic bone, no suitable scaffold material has yet been found. In this investigation, the iron doped brushite (CaHPO₄·2H₂O) has been investigated for osteogenic potential and mechanical properties. The synthesis of iron-oxide doping in the form of Fe^2+,3+-ions were carried out using the solution based method in which the ammonium hydrogen phosphate and calcium nitrate solutions were used in stoichiometric ratio for synthesizing CaHPO₄·2H₂O, with doping concentrations of Fe^2+,3+-ions between 5 mol% and 30 mol%. The synthesized powders were analysed using X-ray powder diffraction, FTIR, SEM and Raman spectroscopic techniques. The heat treatment of synthesized powder was carried out at 1000 °C in air for 5 h, and it was found that the dominant crystalline phase in samples with <20 mol% was β-CPP, which also formed an iron-rich solid solution phase. Increasing the concentrations of Fe^2+,3+-ions enhances the phase fraction of FePO₄ and amorphous phase. Amongst the Fe^2+,3+-doped β-CPP minerals, it was found that the 10 mol% Fe^2+,3+-doped β-CPP offers the best combination of bio-mechanical and osteogenic properties as a scaffold for bone tissue regenerative engineering.

Synthesis and Characterization of Sintered Sr/Fe-Modified Hydroxyapatite Bioceramics for Bone Tissue Engineering Applications

In the current study, Sr/Fe co-substituted hydroxyapatite (HAp) bioceramics were prepared by the sonication-assisted aqueous chemical precipitation method followed by sintering at 1100 °C for bone tissue regeneration applications. The sintered bioceramics were analyzed for various structural and chemical properties through X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy, which confirmed the phase purity of HAp and Sr/Fe co-substitution into its lattice. The Vickers hardness measurement, high blood compatibility (less than 5% hemolysis), and ability to support the adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells suggest the suitability of Sr/Fe:HAp bioceramics for bone implant applications. The physicochemical analysis revealed that the developed Sr/Fe:HAp bioceramics exhibited a polyphasic nature (HAp and βTCP) with almost identical structural morphology having a particle size less than 0.8 μm. The dielectric constant (ε') and dielectric loss (ε″) were potentially affected by the incorporated foreign ions together with the polyphasic nature of the material. The Sr/Fe co-substituted samples demonstrated extended drug (5-fluorouracil and amoxicillin) release profiles at the pH of physiological medium. The multifunctional properties of the developed HAp bioceramics enabled them to be an auspicious candidate for potential biomedical applications, including targeted drug-delivery applications, heating mediator in hyperthermia, and bone tissue repair implants.

Hierarchically designed bone scaffolds: From internal cues to external stimuli

Bone tissue engineering utilizes three critical elements - cells, scaffolds, and bioactive factors - to recapitulate the bone tissue microenvironment, inducing the formation of new bone. Recent advances in materials development have enabled the production of scaffolds that more effectively mimic the hierarchical features of bone matrix, ranging from molecular composition to nano/micro-scale biochemical and physical features. This review summarizes recent advances within the field in utilizing these features of native bone to guide the hierarchical design of materials and scaffolds. Biomimetic strategies discussed in this review cover several levels of hierarchical design, including the development of element-doped compositions of bioceramics, the usage of molecular templates for in vitro biomineralization at the nanoscale, the fabrication of biomimetic scaffold architecture at the micro- and nanoscale, and the application of external physical stimuli at the macroscale to regulate bone growth. Developments at each level are discussed with an emphasis on their in vitro and in vivo outcomes in promoting osteogenic tissue development. Ultimately, these hierarchically designed scaffolds can complement or even replace the usage of cells and biological elements, which present clinical and regulatory barriers to translation. As the field progresses ever closer to clinical translation, the creation of viable therapies will thus benefit from further development of hierarchically designed materials and scaffolds.

3D Superparamagnetic Scaffolds for Bone Mineralization under Static Magnetic Field Stimulation

We reported on three-dimensional (3D) superparamagnetic scaffolds that enhanced the mineralization of magnetic nanoparticle-free osteoblast cells. The scaffolds were fabricated with submicronic resolution by laser direct writing via two photons polymerization of Ormocore/magnetic nanoparticles (MNPs) composites and possessed complex and reproducible architectures. MNPs with a diameter of 4.9 ± 1.5 nm and saturation magnetization of 30 emu/g were added to Ormocore, in concentrations of 0, 2 and 4 mg/mL. The homogenous distribution and the concentration of the MNPs from the unpolymerized Ormocore/MNPs composite were preserved after the photopolymerization process. The MNPs in the scaffolds retained their superparamagnetic behavior. The specific magnetizations of the scaffolds with 2 and 4 mg/mL MNPs concentrations were of 14 emu/g and 17 emu/g, respectively. The MNPs reduced the shrinkage of the structures from 80.2 ± 5.3% for scaffolds without MNPs to 20.7 ± 4.7% for scaffolds with 4 mg/mL MNPs. Osteoblast cells seeded on scaffolds exposed to static magnetic field of 1.3 T deformed the regular architecture of the scaffolds and evoked faster mineralization in comparison to unstimulated samples. Scaffolds deformation and extracellular matrix mineralization under static magnetic field (SMF) exposure increased with increasing MNPs concentration. The results are discussed in the frame of gradient magnetic fields of ~3 × 10⁻⁴ T/m generated by MNPs over the cells bodies.

Magnetic calcium phosphates nanocomposites for the intracellular hyperthermia of cancers of bone and brain

Aim: Magnetic hyperthermia is limited by the low selective susceptibility of neoplastic cells interspersed within healthy tissues, which we aim to improve on. Materials & methods: Two superparamagnetic calcium phosphates nanocomposites, that is, iron-doped hydroxyapatite and iron oxide (Mag) nanoparticles coated with amorphous calcium phosphate (Mag@CaP), were synthesized and tested for selective activity against brain and bone cancers. Results: Nanoparticle uptake and intracellular localization were prerequisites for reduction of cancer viability in alternate magnetic fields of extremely low power. Sheer adsorption onto the outer membrane was not sufficient to produce this effect, which was extremely significant for Mag@CaP and iron-doped hydroxyapatite, but negligible for Mag, demonstrating benefits of combining magnetic iron with calcium phosphates. Conclusion: Such selective effects are important in the global effort to rejuvenate clinical prospects of magnetic hyperthermia.

Insights into the apatite mineralization potential of thermally processed nanocrystalline Ca10−xFex(PO4)6(OH)2

The thermal treatment of Ca_10−xFe_x(PO₄)₆(OH)₂ at different temperatures had an effect on the mineralization potential under non-cellular and cellular conditions by releasing its bioactive ions at optimal or excessive levels.

A Graded Multifunctional Hybrid Scaffold with Superparamagnetic Ability for Periodontal Regeneration

The regeneration of dental tissues is a still an unmet clinical need; in fact, no therapies have been completely successful in regenerating dental tissue complexes such as periodontium, which is also due to the lack of scaffolds that are able to guide and direct cell fate towards the reconstruction of different mineralized and non-mineralized dental tissues. In this respect, the present work develops a novel multifunctional hybrid scaffold recapitulating the different features of alveolar bone, periodontal ligament, and cementum by integrating the biomineralization process, and tape casting and electrospinning techniques. The scaffold is endowed with a superparamagnetic ability, thanks to the use of a biocompatible, bioactive superparamagnetic apatite phase, as a mineral component that is able to promote osteogenesis and to be activated by remote magnetic signals. The periodontal scaffold was obtained by engineering three different layers, recapitulating the relevant compositional and microstructural features of the target tissues, into a monolithic multifunctional graded device. Physico-chemical, morphological, and ultrastructural analyses, in association with preliminary in vitro investigations carried out with mesenchymal stem cells, confirm that the final scaffold exhibits a good mimicry of the periodontal tissue complex, with excellent cytocompatibility and cell viability, making it very promising for regenerative applications in dentistry.

Non-ergodic tube structures in magnetic gels and suspensions

We present results of a study of internal structures, which can appear in magnetic suspensions and gels filling a flat gap under the influence of a magnetic field applied perpendicular to the gap walls. The considered system consists of magnetizable microparticles with a mean diameter of ∼35 μm. Experimental observation demonstrates that the particles can form stable tube shaped structures elongated along the field direction. These structures have internal cavities. The theoretical analysis, performed in this study, shows that the tubes do not correspond to a thermodynamic equilibrium state of the system and rather present transitive non-ergodic structures. These structures are stacked in a state of local energetic minima because of the relatively large size of the particles and negligible Brownian effects. Our theoretical model is suggested to explain the physical reason of the appearance of tube-like structures.

Development of Magnetically Active Scaffolds for Bone Regeneration

This work reports on the synthesis, with the thermally induced phase separation (TIPS) technique, of poly (l-lactide) (PLLA) scaffolds containing Fe-doped hydroxyapatite (FeHA) particles for bone regeneration. Magnetization curves and X-ray diffraction indicate two magnetic particle phases: FeHA and magnetite Fe₃O₄. Magnetic nanoparticles (MNPs) are approximately 30 ± 5 nm in width and 125 ± 25 nm in length, and show typical ferromagnetic properties, including coercivity and rapid saturation magnetization. Scanning electron microscopy (SEM) images of the magnetic scaffolds reveal their complex morphology changes with MNP concentration. Similarly, at compositions of approximately 20% MNPs, the phase separation changes, passing from solid⁻liquid to liquid⁻liquid as revealed by the hill-like structures, with low peaks that give the walls in the SEM images a surface pattern of micro-ruggedness typical of nucleation mechanisms and growth. In vitro degradation experiments, carried out for more than 28 weeks, demonstrated that the MNPs delay the scaffold degradation process. Cytotoxicity is appreciated for FeHA content above 20%.

Magnetic field and nano-scaffolds with stem cells to enhance bone regeneration

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy.

A combined low-frequency electromagnetic and fluidic stimulation for a controlled drug release from superparamagnetic calcium phosphate nanoparticles: potential application for cardiovascular diseases

Alternative drug delivery approaches to treat cardiovascular diseases are currently under intense investigation. In this domain, the possibility to target the heart and tailor the amount of drug dose by using a combination of magnetic nanoparticles (NPs) and electromagnetic devices is a fascinating approach. Here, an electromagnetic device based on Helmholtz coils was generated for the application of low-frequency magnetic stimulations to manage drug release from biocompatible superparamagnetic Fe-hydroxyapatite NPs (FeHAs). Integrated with a fluidic circuit mimicking the flow of the cardiovascular environment, the device was efficient to trigger the release of a model drug (ibuprofen) from FeHAs as a function of the applied frequencies. Furthermore, the biological effects on the cardiac system of the identified electromagnetic exposure were assessed in vitro and in vivo by acute stimulation of isolated adult cardiomyocytes and in an animal model. The cardio-compatibility of FeHAs was also assessed in vitro and in an animal model. No alterations of cardiac electrophysiological properties were observed in both cases, providing the evidence that the combination of low-frequency magnetic stimulations and FeHAs might represent a promising strategy for controlled drug delivery to the failing heart.

Clinical, Radiological, and Histological Assessment of Magnetic Nanoparticles as Pulpotomy Medicament in Primary Molars

AIM AND OBJECTIVES

Aim of the study was to evaluate the success of magnetic nanoparticles (MNPs) as pulpotomy medicament by clinical, radiologic, and histological assessment in primary molars.

MATERIALS AND METHODS

The sample included 30 primary molars from 25 children aged between 3 and 9 years requiring pulpotomy treatment. Pulpotomy was carried out with MNPs. The teeth were evaluated after a period of 3, 6, and 12 months clinically and with the aid of radiographs. After 1 year, 10 teeth were extracted for histological evaluation under field emission scanning electron microscope (FE-SEM; ZEISS, Model No. Supra 55vp).

RESULTS

Of the samples, 98% showed clinical success rate with absence of pain, swelling, mobility, and abscess formation. After 3 months, 98% radiological success with absence of periodontal ligament widening, root resorption, and inter-radicular radiolucency was noted. Histological examination carried out under FE-SEM revealed a zone of odontoblastic proliferation at the interface between MNPs and odontoblastic layer of pulp and viable pulpal cells from the canal orifice till apical foramen.

CONCLUSION

Magnetic nanoparticles can be recommended as an effective pulpotomy medicament with hard tissue barrier formation and preservation of vitality of remaining radicular pulp.How to cite this article: Konyala HR, Mareddy AR, Puppala N, Reddy NV, Mallela MK, Susheela KP. Clinical, Radiological, and Histological Assessment of Magnetic Nanoparticles as Pulpotomy Medicament in Primary Molars. Int J Clin Pediatr Dent 2018;11(4):283-287.

Shear Elasticity of Magnetic Gels with Internal Structures

We present the results of the theoretical modeling of the elastic shear properties of a magnetic gel, consisting of soft matrix and embedded, fine magnetizable particles, which are united in linear chain-like structures. We suppose that the composite is placed in a magnetic field, perpendicular to the direction of the sample shear. Our results show that the field can significantly enhance the mechanical rigidity of the soft composite. Theoretical results are in quantitative agreement with the experiments.

On the use of superparamagnetic hydroxyapatite nanoparticles as an agent for magnetic and nuclear in vivo imaging

The identification of alternative biocompatible magnetic NPs for advanced clinical application is becoming an important need due to raising concerns about iron accumulation in soft issues associated to the administration of superparamagnetic iron oxide nanoparticles (NPs). Here, we report on the performance of previously synthetized iron-doped hydroxyapatite (FeHA) NPs as contrast agent for magnetic resonance imaging (MRI). The MRI contrast abilities of FeHA and Endorem® (dextran coated iron oxide NPs) were assessed by ¹H nuclear magnetic resonance relaxometry and their performance in healthy mice was monitored by a 7 Tesla scanner. FeHA applied a higher contrast enhancement, and had a longer endurance in the liver with respect to Endorem® at iron equality. Additionally, a proof of concept of FeHA use as scintigraphy imaging agent for positron emission tomography (PET) and single photon emission computed tomography (SPECT) was given labeling FeHA with ^99mTc-MDP by a straightforward surface functionalization process. Scintigraphy/x-ray fused imaging and ex vivo studies confirmed its dominant accumulation in the liver, and secondarily in other organs of the mononuclear phagocyte system. FeHA efficiency as MRI-T₂ and PET-SPECT imaging agent combined to its already reported intrinsic biocompatibility qualifies it as a promising material for innovative nanomedical applications.

STATEMENT OF SIGNIFICANCE

The ability of iron-doped hydroxyapatite nanoaprticles (FeHA) to work in vivo as imaging agents for magnetic resonance (MR) and nuclear imaging is demonstrated. FeHA applied an higher MR contrast in the liver, spleen and kidneys of mice with respect to Endorem®. The successful radiolabeling of FeHA allowed for scintigraphy/X-ray and ex vivo biodistribution studies, confirming MR results and envisioning FeHA application for dual-imaging.

Magnetic properties and cytocompatibility of transition-metal-incorporated hydroxyapatite

A detailed magnetization study, along with an assessment of the cellular proliferation, has been carried out on transition-metal-doped hydroxyapatite (HA), Ca_10-xM_x(PO₄)₆(OH)₂, where M = Mn, Co, and Fe. In particular, a series of MnHA powder samples with an x value of 0.04 ≤ x ≤ 1.21, one CoHA (x = 0.48) and one FeHA sample (x = 1.06) were synthesized using a wet chemical method along with an ion-exchange procedure. Characterization by transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) indicated that the substitution of M elements does not change the morphology and crystalline structure of pure HA that showing a single phased HA nano-rod. In every case, the magnetization isotherms for 10 K ≤ T ≤ 300 K were linear through the origin characteristic of a paramagnetic response with no indication of superparamagnetic behavior, hysteresis, or magnetic ordering. The magnetic behavior for all samples could be fit to the Curie-Weiss law yielding values for the M ion magnetic moments. The Mn²⁺ magnetic moments were close to the spin-only value of S = 5/2 or 5.92 μ_B, while the Co²⁺ moment (4.41 μ_B) was larger than the spin-only value for S = 3/2, indicating an orbital contribution due to incomplete quenching. The magnetic behavior for the FeHA sample showed a possible spin-state transition. In addition, no statistically significant differences were observed when cells were treated with the same dose of HA or MnHA up to 50 μg/mL, suggesting that the substituted Mn introduces no cytotoxicity to the HA powders.

Recent progress on fabrication and drug delivery applications of nanostructured hydroxyapatite

Through this brief review, we provide a comprehensive historical background of the development of nanostructured hydroxyapatite (nHAp), and its application potentials for controlled drug delivery, drug conjugation, and other biomedical treatments. Aspects associated with efficient utilization of hydroxyapatite (HAp) nanostructures such as their synthesis, interaction with drug molecules, and other concerns, which need to be resolved before they could be used as a potential drug carrier in body system, are discussed. This review focuses on the evolution of perceptions, practices, and accomplishments in providing improved delivery systems for drugs until date. The pioneering developments that have presaged today's fascinating state of the art drug delivery systems based on HAp and HAp-based composite nanostructures are also discussed. Special emphasis has been given to describe the application and effectiveness of modified HAp as drug carrier agent for different diseases such as bone-related disorders, carriers for antibiotics, anti-inflammatory, carcinogenic drugs, medical imaging, and protein delivery agents. As only a very few published works made comprehensive evaluation of HAp nanostructures for drug delivery applications, we try to cover the three major areas: concepts, practices and achievements, and applications, which have been consolidated and patented for their practical usage. The review covers a broad spectrum of nHAp and HAp modified inorganic drug carriers, emphasizing some of their specific aspects those needed to be considered for future drug delivery applications. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Nanotechnology Approaches to Biology > Cells at the Nanoscale.