Roberto Guzman de Villoria

Microbial colonisation of transparent glass-like carbon films triggered by a reversible radiation-induced hydrophobic to hydrophilic transition

We report a reversible wettability hydrophobic to hydrophilic transition in transparent glass-like carbon films under ultraviolet irradiation when the source emitted in the vacuum ultraviolet. The transition occurred at doses below 5 J cm−2 for devices emitting at 185 nm and was absent when using a 266 nm monochromatic laser source. Hydrophilicity, measured as the water contact angle, was higher when the films were irradiated in air with high relative humidity. Sample hydrophobicity was almost entirely restored over the following 24 h and was completely restored to the initial level when samples were stored for sufficient time under ambient conditions. Our observations were consistent with a transition caused by the dissociative adsorption of water molecules leading to the formation of polar surface groups. Over the few hours in which the surface remained hydrophilic under ambient conditions, a rapid colonisation with Escherichia coli took place with extensive biofilm formation. The percent surface colonised increased from 1.30% ± 0.4% to a maximum of 51.0% ± 2.7% for carbon films irradiated in dry air. Irradiation in the presence of water vapour led to surfaces which were more hydrophilic, but less prone to bacterial adhesion. Bacterial colonisation was favoured in films with intermediate hydrophilicity irrespective of the surface charge, measured as the zeta potential. Our study demonstrates that vacuum ultraviolet irradiation induces a wettability transition in glass-like carbon films, and that a relatively short ultraviolet dose of 185 nm irradiation renders their surfaces highly biocompatible.

Data Available Statement, manuscript: Cell survival and differentiation with nanocrystalline glass-like carbon using substantia nigra dopaminergic cells derived from transgenic mouse embryos. Rodriguez-Losada et al

Regenerative medicine requires, in many cases, physical supports to facilitate appropriate cellular architecture, cell polarization and the improvement of the correct differentiation processes of embryonic stem cells, induced pluripotent cells or adult cells. Because the interest in carbon nanomaterials has grown within the last decade in light of a wide variety of applications, the aim of this study was to test and evaluate the suitability and cytocompatibility of a particular nanometer-thin nanocrystalline glass-like carbon film (NGLC) composed of curved graphene flakes joined by an amorphous carbon matrix. This material is a disordered structure with high transparency and electrical conductivity. For this purpose, we used a cell line (SN4741) from substantia nigra dopaminergic cells derived from transgenic mouse embryos. Cells were cultured either in a powder of increasing concentrations of NGLC microflakes (82±37μm) in the medium or on top of nanometer-thin films bathed in the same culture medium. The metabolism activity of SN4741 cells in presence of NGLC was assessed using methylthiazolyldiphenyl-tetrazolium (MTT) and apoptosis/necrosis flow cytometry assay respectively. Growth and proliferation as well as senescence were demonstrated by western blot (WB) of proliferating cell nuclear antigen (PCNA), monoclonal phosphorylate Histone 3 (serine 10) (PH3) and SMP30 marker. Specific dopaminergic differentiation was confirmed by the WB analysis of tyrosine hydroxylase (TH). Cell maturation and neural capability were characterized using specific markers (SYP: synaptophysin and GIRK2: G-protein-regulated inward-rectifier potassium channel 2 protein) via immunofluorescence and coexistence measurements. The results demonstrated cell positive biocompatibility with different concentrations of NGLC. The cells underwent a process of adaptation of SN4741 cells to NGLC where their metabolism decreases. This process is related to a decrease of PH3 expression and significant increase SMP30 related to senescence processes. After 7 days, the cells increased the expression of TH and PCNA that is related to processes of DNA replication. On the other hand, cells cultured on top of the film showed axonal-like alignment, edge orientation, and network-like images after 7 days. Neuronal capability was demonstrated to a certain extent through the analysis of significant coexistence between SYP and GIRK2. Furthermore, we found a direct relationship between the thickness of the films and cell maturation. Although these findings share certain similarities to our previous findings with graphene oxide and its derivatives, this particular nanomaterial possesses the advantages of high conductivity and transparency. In conclusion, NGLC could represent a new platform for biomedical applications, such as for use in neural tissue engineering and biocompatible devices.

Enhanced Impact Energy Absorption Characteristics of Sandwich Composites through Tufting

Sandwich structures are highly demanded where a high flexural stiffness per weight ratio is needed. The main limiting factor of these materials is the core/skin interface, which tends to delaminate. Tufting is one of the most promising technologies to reinforce this interface along the z-direction. In this article, the energy absorption of tufted sandwich structures under impact loads is evaluated. Six different types of tufted specimens were tested, including both carbon and glass fiber faces with three different tufting densities. The impact behavior of a sandwich panel is proved to be effectively improved by the tufting process.