Fabrication of Graphene Nanoplatelet-Incorporated Porous Hydroxyapatite Composites: Improved Mechanical and in Vivo Imaging Performances for Emerging Biomedical Applications

Influence of Graphene Nanoplatelets on the Performance of Axial Suspension Plasma-Sprayed Hydroxyapatite Coatings

Axial suspension plasma spraying (ASPS) is an alternative technique to atmospheric plasma spraying (APS), which uses a suspension of much finer powders (<5-micron particle size) as the feedstock. It can produce more refined microstructures than APS for biomedical implants. This paper highlights the influence of incorporated graphene nanoplatelets (GNPs) on the behavior of ASPS hydroxyapatite (HAp) coatings. The characterization of the ASPS coatings (HAp + varying GNP contents) was carried out using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), confocal Raman microscopy (CRM), white light interferometry (WLI), and contact angle measurements. The evaluation of the mechanical properties such as the hardness, roughness, adhesion strength, and porosity was carried out, along with a fretting wear performance. Additionally, the biocompatibility of the Hap + GNP coatings was evaluated using cytotoxicity testing which revealed a decrease in the cell viability from 92.7% to 85.4%, with an increase in the GNP wt.%. The visualization of the cell’s components was carried out using SEM and Laser Scanning Microscopy. Furthermore, the changes in the genetic expression of the various cellular markers were assessed to analyze the epigenetic changes in human mesenchymal stem cells. The gene expression changes suggested that GNPs upregulated the proliferation marker and downregulated the pluripotent markers by a minimum of three folds.

Protective effects of resveratrol against genotoxicity induced by nano and bulk hydroxyapatite in Drosophila melanogaster

Hydroxyapatite (HAp) is a naturally occurring calcium phosphate mineral predominantly used for its biocompatibility in a number of areas such as bone grafting, prosthesis coating in dentistry, and targeted drug delivery. Since the nano form of HAp (nHAp) has gained popularity attributed to a re-mineralizing effect in dental repair procedures, concerns have been raised over safety and biocompatibility of these nanoparticles (NP). This study, therefore, aimed to (1) investigate mechanisms of potential genotoxicity and enhanced generation of reactive oxygen species (ROS) initiated by bulk and nano forms of HAp and (2) test in vivo whether resveratrol, a type of natural phenol, might mitigate the extent of potential DNA damage. The size of nHAp was determined to be 192.13 ± 9.91 nm after dispersion using transmission electron microscopy (TEM). Drosophila melanogaster was employed as a model organism to determine the genotoxic potential and adverse effects of HAp by use of (comet assay), mutagenic and recombinogenic activity (wing spot test), and ROS-mediated damage. Drosophila wing-spot tests demonstrated that exposure to nontoxic bulk and nHAp concentrations (1, 2.5, 5 or 10 mM) produced no significant recombination effects or mutagenicity. However, bulk and nHAp at certain doses (2.5, 5 or 10 mM) induced genotoxicity in hemocytes and enhanced ROS production. Resveratrol was found to ameliorate the genotoxic effects induced by bulk HAp and nHAp in comet assay. Data demonstrate that treatment with nano and bulk Hap-induced DNA damage and increased ROS generation D. melanogaster which was alleviated by treatment with resveratrol.

Mechanisms and biological impacts of graphene and multi-walled carbon nanotubes on Drosophila melanogaster: Oxidative stress, genotoxic damage, phenotypic variations, locomotor behavior, parasitoid resistance, and cellular immune response

The use of graphene and multi-walled carbon nanotubes (MWCNTs) has now become rather common in medical applications as well as several other areas thanks to their useful physicochemical properties. While in vitro testing offers some potential, in vivo research into toxic effects of graphene and MWCNTs could yield much more reliable data. Drosophila melanogaster has recently gained significant popularity as a dynamic eukaryotic model in examining toxicity, genotoxicity, and biological effects of exposure to nanomaterials, including oxidative stress, cellular immune response against two strains (NSRef and G486) of parasitoid wasp (Leptopilina boulardi), phenotypic variations, and locomotor behavior risks. D. melanogaster was used as a model organism in our study to identify the potential risks of exposure to graphene (thickness: 2-18 nm) and MWCNTs in different properties (as pure [OD: 10-20 nm short], modified by amide [NH₂ ] [OD: 7-13 nm length: 55 μm], and modified by carboxyl [COOH] [OD: 30-50 nm and length: 0.5-2 μm]) at concentrations ranging from 0.1 to 250 μg/ml. Significant effects were observed at two high doses (100 and 250 μg/ml) of graphene or MWCNTs. This is the first study to report findings of cellular immune response against hematopoiesis and parasitoids, nanogenotoxicity, phenotypic variations, and locomotor behavior in D. melanogaster.

Antiviral performance of graphene-based materials with emphasis on COVID-19: A review

Coronavirus disease-2019 has been one of the most challenging global epidemics of modern times with a large number of casualties combined with economic hardships across the world. Considering that there is still no definitive cure for the recent viral crisis, this article provides a review of nanomaterials with antiviral activity, with an emphasis on graphene and its derivatives, including graphene oxide, reduced graphene oxide and graphene quantum dots. The possible interactions between surfaces of such nanostructured materials with coronaviruses are discussed. The antiviral mechanisms of graphene materials can be related to events such as the inactivation of virus and/or the host cell receptor, electrostatic trapping and physico-chemical destruction of viral species. These effects can be enhanced by functionalization and/or decoration of carbons with species that enhances graphene-virus interactions. The low-cost and large-scale preparation of graphene materials with enhanced antiviral performances is an interesting research direction to be explored.

Influence of sonication on the physicochemical and biological characteristics of selenium-substituted hydroxyapatites

Selenium-doped hydroxyapatite composite formed by the sonication technique investigated to have superior properties that are specifically advantageous in the tissue engineering, growth, and regeneration sector.