Magnetism in Dentistry: Review and Future Perspectives

A Review of Biomimetic and Biodegradable Magnetic Scaffolds for Bone Tissue Engineering and Oncology

Bone defects characterized by limited regenerative properties are considered a priority in surgical practice, as they are associated with reduced quality of life and high costs. In bone tissue engineering, different types of scaffolds are used. These implants represent structures with well-established properties that play an important role as delivery vectors or cellular systems for cells, growth factors, bioactive molecules, chemical compounds, and drugs. The scaffold must provide a microenvironment with increased regenerative potential at the damage site. Magnetic nanoparticles are linked to an intrinsic magnetic field, and when they are incorporated into biomimetic scaffold structures, they can sustain osteoconduction, osteoinduction, and angiogenesis. Some studies have shown that combining ferromagnetic or superparamagnetic nanoparticles and external stimuli such as an electromagnetic field or laser light can enhance osteogenesis and angiogenesis and even lead to cancer cell death. These therapies are based on in vitro and in vivo studies and could be included in clinical trials for large bone defect regeneration and cancer treatments in the near future. We highlight the scaffolds' main attributes and focus on natural and synthetic polymeric biomaterials combined with magnetic nanoparticles and their production methods. Then, we underline the structural and morphological aspects of the magnetic scaffolds and their mechanical, thermal, and magnetic properties. Great attention is devoted to the magnetic field effects on bone cells, biocompatibility, and osteogenic impact of the polymeric scaffolds reinforced with magnetic nanoparticles. We explain the biological processes activated due to magnetic particles' presence and underline their possible toxic effects. We present some studies regarding animal tests and potential clinical applications of magnetic polymeric scaffolds.

The fabrication of halloysite nanotube-based multicomponent hydrogel scaffolds for bone healing

Bone tissue engineering, as an alternative for common available therapeutic approaches, has been developed to focus on reconstructing of the missing tissues and restoring their functionality. In this work, three-dimensional (3D) nanocomposite scaffolds of polycaprolactone-polyethylene glycol-polycaprolactone/gelatin (PCEC/Gel) were prepared by freeze-drying method. Biocompatible nanohydroxyapatite (nHA), iron oxide nanoparticle (Fe₃O₄) and halloysite nanotube (HNT) powders were added to the polymer matrix aiming to combine the osteogenic activity of nHA or Fe₃O₄ with high mechanical strength of HNT. The scanning electron microscope (SEM) methods was utilized to characterize the nanotube morphology of HNT as well as nanoparticles of Fe₃O₄ and nHA. Prepared scaffolds were characterized via Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and SEM methods. In addition, the physical behavior of scaffolds was evaluated to explore the influence of HNT on the physicochemical properties of composites. Cell viability and attachment were investigated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay and SEM on human dental pulp-derived mesenchymal stem cells (h-DPSCs) in-vitro. Cell proliferation was observed without any cytotoxicity effect on h-DPSCs for all examined scaffolds. Alizarin red (ARS) and alkaline phosphatase (ALP) staining were carried out to determine the osteoconductivity of scaffolds. The data demonstrated that all PCEC/Gel/HNT hydrogel scaffolds supported osteoblast differentiation of hDPSCs with moderate effects on cell proliferation. Moreover, PCEC/Gel/HNT/nHA with proper mechanical strength showed better biological activity compared to PCEC/Gel/HNT/Fe₃O₄ and PCEC/Gel/HNT scaffolds. Therefore, this study suggested that with proper fillers content, PCEC/Gel/HNT nanocomposite hydrogels alone or in a complex with nHA, Fe₃O₄ could be a suitable candidate for hard tissue regeneration.