Eudes Lorençon

Carbon nanotube interaction with extracellular matrix proteins producing scaffolds for tissue engineering

In recent years, significant progress has been made in organ transplantation, surgical reconstruction, and the use of artificial prostheses to treat the loss or failure of an organ or bone tissue. In recent years, considerable attention has been given to carbon nanotubes and collagen composite materials and their applications in the field of tissue engineering due to their minimal foreign-body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth, proliferation, and differentiation. Recently, grafted collagen and some other natural and synthetic polymers with carbon nanotubes have been incorporated to increase the mechanical strength of these composites. Carbon nanotube composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering.

Influence of spontaneous calcium events on cell-cycle progression in embryonal carcinoma and adult stem cells

Spontaneous Ca(2+) events have been observed in diverse stem cell lines, including carcinoma and mesenchymal stem cells. Interestingly, during cell cycle progression, cells exhibit Ca(2+) transients during the G(1) to S transition, suggesting that these oscillations may play a role in cell cycle progression. We aimed to study the influence of promoting and blocking calcium oscillations in cell proliferation and cell cycle progression, both in neural progenitor and undifferentiated cells. We also identified which calcium stores are required for maintaining these oscillations. Both in neural progenitor and undifferentiated cells calcium oscillations were restricted to the G1/S transition, suggesting a role for these events in progression of the cell cycle. Maintenance of the oscillations required calcium influx only through inositol 1,4,5-triphosphate receptors (IP(3)Rs) and L-type channels in undifferentiated cells, while neural progenitor cells also utilized ryanodine-sensitive stores. Interestingly, promoting calcium oscillations through IP(3)R agonists increased both proliferation and levels of cell cycle regulators such as cyclins A and E. Conversely, blocking calcium events with IP(3)R antagonists had the opposite effect in both undifferentiated and neural progenitor cells. This suggests that calcium events created by IP(3)Rs may be involved in cell cycle progression and proliferation, possibly due to regulation of cyclin levels, both in undifferentiated cells and in neural progenitor cells.

Graphene-based nanomaterials: biological and medical applications and toxicity

Graphene and its derivatives, due to a wide range of unique properties that they possess, can be used as starting material for the synthesis of useful nanocomplexes for innovative therapeutic strategies and biodiagnostics. Here, we summarize the latest progress in graphene and its derivatives and their potential applications for drug delivery, gene delivery, biosensor and tissue engineering. A simple comparison with carbon nanotubes uses in biomedicine is also presented. We also discuss their in vitro and in vivo toxicity and biocompatibility in three different life kingdoms (bacterial, mammalian and plant cells). All aspects of how graphene is internalized after in vivo administration or in vitro cell exposure were brought about, and explain how blood-brain barrier can be overlapped by graphene nanomaterials.

Intracellular Ca2+ Regulation During Neuronal Differentiation of Murine Embryonal Carcinoma and Mesenchymal Stem Cells

Changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) play a central role in neuronal differentiation. However, Ca(2+) signaling in this process remains poorly understood and it is unknown whether embryonic and adult stem cells share the same signaling pathways. To clarify this issue, neuronal differentiation was analyzed in two cell lines: embryonic P19 carcinoma stem cells (CSCs) and adult murine bone-marrow mesenchymal stem cells (MSC). We studied Ca(2+) release from the endoplasmic reticulum via intracellular ryanodine-sensitive (RyR) and IP(3)-sensitive (IP(3)R) receptors. We observed that caffeine, a RyR agonist, induced a [Ca(2+)](i) response that increased throughout neuronal differentiation. We also demonstrated a functional coupling between RyRs and L- but not with N-, P-, or Q-type Ca(v)1 Ca(2+) channels, both in embryonal CSC and adult MSC. We also found that agonists of L-type channels and of RyRs increase neurogenesis and neuronal differentiation, while antagonists of these channels have the opposite effect. Thus, our data demonstrate that in both cell lines RyRs control internal Ca(2+) release following voltage-dependent Ca(2+) entry via L-type Ca(2+) channels. This study shows that both in embryonal CSC and adult MSC [Ca(2+)](i) is controlled by a common pathway, indicating that coupling of L-type Ca(2+) channels and RyRs may be a conserved mechanism necessary for neuronal differentiation.

Nanostructured δ-FeOOH: a novel photocatalyst for water splitting

We report on the first use of nanostructured δ-FeOOH as a promising photocatalyst for hydrogen production. The high surface area, interparticle mesoporosity, small particle size and band gap energy in the visible region make nanostructured δ-FeOOH a suitable candidate for use as a photocatalyst.

Direct production of carbon nanotubes/metal nanoparticles hybrids from a redox reaction between metal ions and reduced carbon nanotubes.

A method to decorate single-walled and multiwalled carbon nanotubes (CNTs) with metal nanoparticles (NPs) based on the formation of a CNT polyelectrolyte is reported. Such a method does not rely on CNT surface functionalization or the use of surfactants. It has been tested for gold (Au) and palladium (Pd). The resulting hybrids present metal NPs highly dispersed along the tube walls and with small size dispersion. The average diameters of the Au and Pd NPs were approximately 5 and approximately 3 nm, respectively. This method paves the way for large-scale decoration of CNTs with metal NPs.

Electrochemical recycling of cobalt from spent cathodes of lithium-ion batteries: its application as supercapacitor

The supercapacitive behavior of the metallic cobalt recycled from Li-ion batteries has been studied in this work. The reversibility of both redox process (CoII/CoIII) and (CoIII/CoIV) in KOH 6xa0molxa0L−1 is very high and promising for capacitive applications in electrochemical devices. The specific capacitances calculated from cyclic voltammetry and electrochemical impedance spectroscopy show a good agreement, giving the value of 625xa0Fg−1. The electrode morphology presents a high porosity, thus an electrical equivalent circuit composed of two parallel resistance and capacitance elements in series was proposed. The specific capacitance values calculated from charge/discharge curves at 0.23 and 2.3xa0mA/cm2 are 601 and 384xa0Fg−1, respectively. Thereby, it was observed that metallic cobalt recycled from ion-Li batteries is compatible with other supercapacitive materials. This shows that cobalt recycling from Li-ion batteries is economically and environmentally viable for application in supercapacitor devices.