Formation of Fe and Ni substituted LiMn2-XMXO4 nanopowders and their crystal and electronic structure and magnetic properties

The Pechini sol-gel method was applied to obtain LiMn2-xTxO4 (T = Ni, Fe; x = 0.1 to 0.5) nanopowders. Crystal and electronic structures, chemical composition and magnetic properties of the materials were characterized by X-ray diffraction, XPS, SEM/EDX microscopy, prompt gamma-ray activation analysis (PGAA), Mössbauer spectroscopy and magnetic susceptibility, respectively. XRD measurements showed that the LiMn2-xNixO4 were single phase for x = 0.1 and 0.2. Three samples with higher Ni content contained some addition of a second phase. Analysis of the oxidation state of the dopants by XPS revealed ionic Ni2+ and Fe3+. Mössbauer spectroscopy also confirmed 3+ oxidation state of iron and its location in octahedral sites, which excluded the inverse spinel configuration. XPS examinations showed that Mn3+ ions dominated in the iron substituted series whereas the Mn4+ was dominant in the nickel serie

Long term influence of carbon nanoparticles on health and liver status in rats

Due to their excellent biocompatibility, carbon nanoparticles have been widely investigated for prospective biomedical applications. However, their impact on an organism with prolonged exposure is still not well understood. Here, we performed an experiment investigating diamond, graphene oxide and graphite nanoparticles, which were repeatedly administrated intraperitoneally into Wistar rats for four weeks. Some of the animals was sacrificed after the last injection, whereas the rest were sacrificed twelve weeks after the last exposure. We evaluated blood morphology and biochemistry, as well as the redox and inflammatory state of the liver. The results show the retention of nanoparticles within the peritoneal cavity in the form of prominent aggregates in proximity to the injection site, as well as the presence of some nanoparticles in the mesentery. Small aggregates were also visible in the liver serosa, suggesting possible transportation to the liver. However, none of the tested nanoparticles affected the health of animals. This lack of toxic effect may suggest the potential applicability of nanoparticles as drug carriers for local therapies, ensuring accumulation and slow release of drugs into a targeted tissue without harmful systemic side effects

In vitro and in vivo effects of graphene oxide and reduced graphene oxide on glioblastoma

Graphene and its related counterparts are considered the future of advanced nanomaterials owing to their exemplary properties. However, information about their toxicity and biocompatibility is limited. The objective of this study is to evaluate the toxicity of graphene oxide (GO) and reduced graphene oxide (rGO) platelets, using U87 and U118 glioma cell lines for an in vitro model and U87 tumors cultured on chicken embryo chorioallantoic membrane for an in vivo model. The in vitro investigation consisted of structural analysis of GO and rGO platelets using transmission elec tron microscopy, evaluation of cell morphology and ultrastructure, assessment of cell viability by XTT assay, and investigation of cell proliferation by BrdU assay. Toxicity in U87 glioma tumors was evaluated by calculation of weight and volume of tumors and analyses of ultrastructure, histology, and protein expression. The in vitro results indicate that GO and rGO enter glioma cells and have different cytotoxicity. Both types of platelets reduced cell viability and proliferation with increasing doses, but rGO was more toxic than GO. The mass and volume of tumors were reduced in vivo after injection of GO and rGO. Moreover, the level of apoptotic markers increased in rGO-treated tumors. We show that rGO induces cell death mostly through apoptosis, indicating the potential applicability of graphene in cancer therapy

Gradient chitosan hydrogels modified with graphene derivatives and hydroxyapatite : physiochemical properties and initial cytocompatibility evaluation

In this study, we investigated preparation of gradient chitosan-matrix hydrogels through a novel freezing–gelling–thawing method. The influence of three types of graphene family materials (GFM), i.e., graphene oxide (GO), reduced graphene oxide (rGO), and poly(ethylene glycol) grafted graphene oxide (GO-PEG), as well as hydroxyapatite (HAp) on the physicochemical and biological properties of the composite hydrogels was examined in view of their potential applicability as tissue engineering scaffolds. The substrates and the hydrogel samples were thoroughly characterized by X-ray photoelectron spectroscopy, X-ray diffractometry, infrared spectroscopy, digital and scanning electron microscopy, rheological and mechanical analysis, in vitro chemical stability and bioactivity assays, as well as initial cytocompatibility evaluation with human umbilical cord Wharton’s jelly mesenchymal stem cells (hUC-MSCs). We followed the green-chemistry approach and avoided toxic cross-linking agents, using instead specific interactions of our polymer matrix with tannic acid, non-toxic physical cross-linker, and graphene derivatives. It was shown that the most promising are the gradient hydrogels modified with GO-PEG and HAp

Thin polymer films based on poly(vinyl alcohol) containing graphene oxide and reduced graphene oxide with functional properties

10 pags., 7 figs., 2 tabs.In this article, the effect of the addition of graphene oxide (GO) and reduced graphene oxide (rGO) on the mechanical properties, thermal stability, and electrical conductivity of polyvinyl alcohol (PVA) has been investigated. Different weight percentages of nanofillers ranging from 0.5 to 5 wt% have been combined with PVA. The ultrasonic technique has been applied to disperse nanofillers in the PVA solution. The nanocomposite films have been prepared via solution casting technique and the dispersion of nanofillers into the PVA has been studied through optical microscopy. The microstructure, crystallization behavior, and interfacial interaction were characterized through X-ray diffraction and Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis have been applied to study the thermal properties of the prepared nanocomposites. The DSC results revealed that the crystallization temperature and melting temperature were enhanced in the presence of GO nanofiller. Besides, the tensile strength at break was improved along with the addition of GO; however, elongation at break for PVA/GO and PVA/rGO was diminished. Moreover, all specimens showed insulating behavior and the only sample was electrically conducting, which contain a high amount of rGO (5 wt%).Spanish Ministry of Science and Innovation, Grant/Award Number:PID2019-107514GB-I0

Graphene functionalized with arginine decreases the development of glioblastoma multiforme tumor in a gene-dependent manner

Our previous studies revealed that graphene had anticancer properties in experiments in vitro with glioblastoma multiforme (GBM) cells and in tumors cultured in vivo. We hypothesized that the addition of arginine or proline to graphene solutions might counteract graphene agglomeration and increase the activity of graphene. Experiments were performed in vitro with GBM U87 cells and in vivo with GBM tumors cultured on chicken embryo chorioallantoic membranes. The measurements included cell morphology, mortality, viability, tumor morphology, histology, and gene expression. The cells and tumors were treated with reduced graphene oxide (rGO) and rGO functionalized with arginine (rGO + Arg) or proline (rGO + Pro). The results confirmed the anticancer effect of graphene on GBM cells and tumor tissue. After functionalization with amino acids, nanoparticles were distributed more specifically, and the flakes of graphene were less agglomerated. The molecule of rGO + Arg did not increase the expression of TP53 in comparison to rGO, but did not increase the expression of MDM2 or the MDM2/TP53 ratio in the tumor, suggesting that arginine may block MDM2 expression. The expression of NQO1, known to be a strong protector of p53 protein in tumor tissue, was greatly increased. The results indicate that the complex of rGO + Arg has potential in GBM therapy

Impact of graphene-based surfaces on the basic biological properties of human umbilical cord mesenchymal stem cells : implications for ex vivo cell expansion aimed at tissue repair

The potential therapeutic applications of mesenchymal stem/stromal cells (MSCs) and biomaterials have attracted a great amount of interest in the field of biomedical engineering. MSCs are multipotent adult stem cells characterized as cells with specific features, e.g., high differentiation potential, low immunogenicity, immunomodulatory properties, and efficient in vitro expansion ability. Human umbilical cord Wharton’s jelly-derived MSCs (hUC-MSCs) are a new, important cell type that may be used for therapeutic purposes, i.e., for autologous and allogeneic transplantations. To improve the therapeutic efficiency of hUC-MSCs, novel biomaterials have been considered for use as scaffolds dedicated to the propagation and differentiation of these cells. Nowadays, some of the most promising materials for tissue engineering include graphene and its derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO). Due to their physicochemical properties, they can be easily modified with biomolecules, which enable their interaction with different types of cells, including MSCs. In this study, we demonstrate the impact of graphene-based substrates (GO, rGO) on the biological properties of hUC-MSCs. The size of the GO flakes and the reduction level of GO have been considered as important factors determining the most favorable surface for hUC-MSCs growth. The obtained results revealed that GO and rGO are suitable scaffolds for hUC-MSCs. hUC-MSCs cultured on: (i) a thin layer of GO and (ii) an rGO surface with a low reduction level demonstrated a viability and proliferation rate comparable to those estimated under standard culture conditions. Interestingly, cell culture on a highly reduced GO substrate resulted in a decreased hUC-MSCs proliferation rate and induced cell apoptosis. Moreover, our analysis demonstrated that hUC-MSCs cultured on all the tested GO and rGO scaffolds showed no alterations of their typical mesenchymal phenotype, regardless of the reduction level and size of the GO flakes. Thus, GO scaffolds and rGO scaffolds with a low reduction level exhibit potential applicability as novel, safe, and biocompatible materials for utilization in regenerative medicine