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 emission of carcinogenic, teratogenic, and mutagenic polycyclic aromatic hydrocarbons (PAHs) during municipal solid waste incineration (MSWI) of fly ash (FA) has attracted significant attention. Hydrothermal treatment (HT) has emerged as a practical approach for degrading PAHs during MSWI of FA by utilizing magnetite (Fe3O4) as a catalyst and hydrogen peroxide (H2O2) as an oxidizing agent. In this study, as an alternative to traditional hydroxyapatite (HAP), eggshell-derived magnetic hydroxyapatite (MHAP) was synthesized and applied in the hydrothermal catalytic degradation of PAHs in MSWI FA in an H2O2 system for the first time. The degradation efficiency of the PAHs is influenced not only by H2O2 but also by the choice of hydroxyapatite. Adding HAP or MHAP during hydrothermal treatment with H2O2 substantially reduced the overall PAH concentration and toxicity equivalent quantity (TEQ), superior to that without H2O2. MHAP demonstrated superior catalytic activity compared to HAP in the presence of H2O2 in the hydrothermal system. The hydrothermal detoxification of the PAHs increased with increasing MHAP dosage. By employing 0.5 mol/L H2O2 as the oxidant and 15 wt% MHAP as the catalyst, a total PAH degradation rate of 88.9 % was achieved, with a remarkable TEQ degradation rate of 98.3 %. Notably, the level of 4-6-ring PAHs, particularly benzo(a) pyrene (BaP) and dibenz(a,h)anthracene (DahA), with a TEQ of 1.0, was significantly reduced (by 69.4 % and 46.0 %, respectively). MHAP remained stable during the hydrothermal catalytic process, whereas H2O2 was effectively activated by MHAP and decomposed to produce strongly oxidizing hydroxyl (•OH) under hydrothermal conditions. •OH produced from the decomposition of H2O2 and metals on the surface of MHAP act as catalytically active centers, efficiently converting high-ring PAHs to low-ring PAHs. These findings provide valuable insights and a technological foundation for PAH detoxification in MSWI FA via hydrothermal catalytic oxidation.

Progressive aging harms bone tissue structure and function and, thus, requires effective therapies focusing on permanent tissue regeneration rather than partial cure, beginning with regenerative medicine. Due to advances in tissue engineering, stimulating osteogenesis with biomimetic nanoparticles to create a regenerative niche has gained attention for its efficacy and cost-effectiveness. In particular, hydroxyapatite (HAP, Ca10(PO4)6(OH)2) has gained significant interest in orthopedic applications as a major inorganic mineral of native bone. Recently, magnetic nanoparticles (MNPs) have also been noted for their multifunctional potential for hyperthermia, MRI contrast agents, drug delivery, and mechanosensitive receptor manipulation to induce cell differentiation, etc. Thus, the present study synthesizes HAP-decorated MNPs (MHAP NPs) via the wet chemical co-precipitation method. Synthesized MHAP NPs were evaluated against the preosteoblast MC3T3-E1 cells towards concentration-dependent cytotoxicity, proliferation, morphology staining, ROS generation, and osteogenic differentiation. The result evidenced that MHAP NPs concentration up to 10 µg/mL was non-toxic even with the time-dependent proliferation studies. As nanoparticle concentration increased, FACS apoptosis assay and ROS data showed a significant rise in apoptosis and ROS generation. The MC3T3-E1 cells cocultured with 5 µg/mL MHAP NPs showed significant osteogenic differentiation potential. Thus, MHAP NPs synthesized with simple wet chemistry could be employed in bone regenerative therapy.

In the present study, the aim was to develop a magneto-responsive nanocomposite for application in drug delivery by the integration of magnetic nanoparticles into an inorganic architecture, hydroxyapatite. The magnetic mesoporous hydroxyapatite nanocomposites, MMHAPs, were synthesized using a template-free method and fully characterized by XRD, FT-IR, TEM, FE-SEM, VSM, ICP, BET, and UV-Vis spectroscopy. MMHAPs exhibited a rod-like shape with a structure of large mesopores and high surface area. A sample of the nanocomposites with well-defined properties, MMHAP(2), was selected as a carrier for delivery of chemotherapy drug, doxorubicin (Dox). Then, it was coated with polyethylene glycol (P) and folic acid (F), providing aqueous stability and tumor targeting, respectively. The evaluation of drug release profile revealed that the release of drug occurs in a time-staggered manner under low pH conditions, which simulate the internal condition of lysosome. More important, a significant drug release was observed under a static magnetic field (SMF), displaying a magnetically triggered release. According to the toxicity assessment, MMHAP(2) did not show any noticeable toxic effect against the tumor cells (Saos-2) and normal cells (HEK-293) up to 100 μg ml-1 in the presence or absence of SMF. In contrast, the drug-loaded nanocomposite, F.P.D@MMHAP(2), possesses high antitumor efficacy particularly in the presence of SMF. Moreover, it was found that the cellular internalization of F.P.D@MMHAP(2) could be increased by SMF, providing therapeutic efficiency enhancement. The high cytotoxic effect of F.P.D@MMHAP(2) with the help of SMF caused apoptosis in the tumor cells, which was preceded by a disturbance in the intracellular redox state and then caspase activation. Based on the data obtained, F.P.D@MMHAP(2) is a pH- and magneto-responsive platform opening up a new perspective in terms of its exploitation in cancer therapy.

Magnetic hydroxyapatite (HAp) is being widely investigated for various applications in medical engineering and nanocomposite for transformation reaction. The present work describes an efficient procedure for the synthesis of phenacyl derivatives employing a novel, green and magnetically retrievable nanocomposite via the grafting of β-cyclodextrin moieties on the magnetic hydroxyapatite surface, γ-Fe2O3@HAp-CD. The structure and composition of the nanocomposite was performed by different methods and analyzed by Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), transmission electron microscopy (TEM), Thermo-Gravimetric Analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and Brunauer Emmett Teller (BET) and vibrating sample magnetometry (VSM). Our results indicate that conjugation with β-CD improves the catalytic activity in the reaction.