The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedures.
The main objective of this research is to prove the viability of obtaining magnesium (Mg) filled polylactic acid (PLA) biocomposites as filament feedstock for material extrusion-based additive manufacturing (AM). These materials can be used for medical applications, thus benefiting of all the advantages offered by AM technology in terms of design freedom and product customization. Filaments were produced from two PLA + magnesium + vitamin E (α-tocopherol) compositions and then used for manufacturing test samples and ACL (anterior cruciate ligament) screws on a low-cost 3D printer. Filaments and implant screws were characterized using SEM (scanning electron microscopy), FTIR (fourier transform infrared spectrometry), and DSC (differential scanning calorimetry) analysis. Although the filament manufacturing process could not ensure a uniform distribution of Mg particles within the PLA matrix, a good integration was noticed, probably due to the use of vitamin E as a precursor. The results also show that the composite biomaterials can ensure and maintain implant screws structural integrity during the additive manufacturing process.
Succeeding in the
substitution of pharmaceutical compounds with
ions deliverable with the use of resorbable biomaterials could have
far-reaching benefits for medicine and economy. Calcium phosphates
are known as excellent accommodators of foreign ions. Manganese, the
fifth most abundant metal on Earth was studied here as an ionic dopant
in β-tricalcium phosphate (β-TCP) ceramics. β-TCP
containing different amounts of Mn2+ ions per Mn
x
Ca3–x
(PO4)2 formula (x = 0, 0.001, 0.01, and 0.1)
was investigated for a range of physicochemical and biological properties.
The results suggested the role of Mn2+ as a structure booster,
not breaker. Mn2+ ions increased the size of coherent X-ray
scattering regions averaged across all crystallographic directions
and also lowered the temperature of transformation of the hydroxyapatite
precursor to β-TCP. The particle size increased fivefold, from
20 to 100 nm, in the 650–750 °C region, indicating that
the reaction of formation of β-TCP was accompanied by a considerable
degree of grain growth. The splitting of the antisymmetric stretching
mode of the phosphate tetrahedron occurred proportionally to the Mn2+ content in the material, while electron paramagnetic resonance
spectra suggested that Mn2+ might substitute for three
out of five possible calcium ion positions in the unit cell of β-TCP.
The biological effects of Mn-free β-TCP and Mn-doped β-TCP
were selective: moderately proliferative to mammalian cells, moderately
inhibitory to bacteria, and insignificant to fungi. Unlike pure β-TCP,
β-TCP doped with the highest concentration of Mn2+ ions significantly inhibited the growth of all bacterial species
tested: Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Enterococcus faecalis. The overall effect against
the Gram-positive bacteria was more intense than against the Gram-negative
microorganisms. Meanwhile, β-TCP alone had an augmentative effect
of the viability of adipose-derived mesenchymal stem cells (ADMSCs)
and the addition of Mn2+ tended to reduce the extent of
this augmentative effect, but without imparting any toxicity. For
all Mn-doped β-TCP concentrations except the highest, the cell
viability after 72 h incubation was significantly higher than that
of the negative control. Assays evaluating the effect of Mn2+-containing β-TCP formulations on the differentiation of ADMSCs
into three different lineagesosteogenic, adipogenic, and chondrogenicdemonstrated
no inhibitory or adverse effects compared to pure β-TCP and
powder-free positive controls. Still, β-TCP delivering the lowest
amount of Mn2+ seemed most effective in sustaining the
differentiation process toward all three phenotypes, indicating that
the dose of Mn2+ in β-TCP need not be excessive to
be effective.
Chemical modification of cellulose by phosphorylation enhances its bioactivity and provides new derivatives and materials with specific end uses. In the present study, cellulose derivatized with phosphorous acid was obtained using the reaction of microcrystalline cellulose with phosphorous acid-urea mixture, in molten state, in comparison with others methods that used different solvents and catalysts. Completely water soluble films with a substitution degree close to one were obtained and characterized by analytical and spectral analysis (FT-IR, (31)P NMR), contact angle, metallographic microscopy and atomic force microscopy (AFM). 31P NMR spectra of derivatized cellulose showed a signal at 2.58 ppm (assigned to P-O-C6) while the doublets at 4.99-5.29 and at 7.38 ppm were assigned to P-O-C2 and P-O-C3, respectively; thus, the formation of monosubstituted phosphorous acid esters of cellulose is advocated. Contact angle measurements showed that the work of adhesion is more important in water than in ethylene glycol, for the phosphorous acid derivatized cellulose. The cytocompatibility of this hydrosoluble derivatized cellulose was tested by direct contact and also by indirect assays on normal human dermal fibroblasts and on osteoblast-like cells (human osteosarcoma). Cell growth on phosphorylated cellulose pellicle and the results from viability assays had shown a good cytocompatibility and lack of toxicity. Phosphorous acid derivatized cellulose would offer a promising biomaterial, useful as scaffolds for new biopolymer composites, and subject for further development as an ionic crosslinker.
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