Stéphane Lucas | Université de Namur (University of Namur) (original) (raw)

Papers by Stéphane Lucas

Optics Express, May 26, 2016

Photonic structures encased by a permeable envelope give rise to iridescent blue color in the sca... more Photonic structures encased by a permeable envelope give rise to iridescent blue color in the scales covering the male Hoplia coerulea beetle. This structure comprises a periodic porous multilayer. The color of these scales is known for changing from blue to green upon contact with water despite the presence of the envelope. This optical system has been referred to as a photonic cell due to the role of the envelope that mediates fluid exchanges with the surrounding environment. Following from previously studied liquid-induced changes in the color appearance of H. coerulea, we measured vapor-induced color changes in its appearance. This response to vapor exposure was marked by reflectance redshift and an increase in peak reflectance intensity. Different physico-chemical processes were investigated to explain the increase in reflectance intensity, a property not usually associated with vapor-induced optical signature changes. These simulations indicated the optical response arose from physisorption of a liquid film on the beetle scales followed by liquid penetration through the envelope and the filling of micropores within the body of the photonic structure.

Nanomedicine, Feb 1, 2019

This study aimed at developing antibody-functionalized gold nanoparticles (AuNPs) to selectively ... more This study aimed at developing antibody-functionalized gold nanoparticles (AuNPs) to selectively target cancer cells and probing their potential radiosensitizing effects under proton irradiation. Materials & methods: AuNPs were conjugated with cetuximab (Ctxb-AuNPs). Ctxb-AuNP uptake was evaluated by transmission electron microscopy and atomic absorption spectroscopy. Radioenhancing effect was assessed using conventional clonogenic assay. Results & conclusion: Ctxb-AuNPs specifically bound to and accumulated in EGFR-overexpressing A431 cells, compared with EGFR-negative MDA-MB-453 cells. Ctxb-AuNPs enhanced the effect of proton irradiation in A431 cells but not in MDA-MB-453 cells. These data indicate, for the first time, that combining enhanced uptake by specific targeting and radioenhancing effect, using conjugated AuNPs, is a promising strategy to increase cell killing by protontherapy.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, Apr 1, 1990

It has been established that nitrogen implantation into metals can alter their surface properties... more It has been established that nitrogen implantation into metals can alter their surface properties such as friction, wear, corrosion, etc. Recent studies have shown that nitrogen implantation into aluminium leads to the formation of aluminium nitride which has interesting tribological, electronic and optical properties. For a given implantation energy, the characteristics of the nitrogen profile, e.g. thickness, shape and concentration, depend strongly on the experimental conditions during the implantation. In order to study the influence of the implantation parameters, aluminium samples have been bombarded with "NC of 100 keV to different doses ((1-20)X 10" Nf/cm2), at several temperatures (25-300 o C). Distributions of the implanted species were investigated by nuclear reaction analysis (NRA) and by Rutherford backscattering spectroscopy (RBS). The chemical bonds of aluminium in the matrix were studied by using low-energy electron-induced X-ray spectroscopy (LEEIXS). It is shown that aluminium nitride is formed and that the nitrogen distribution presents a surface peak when the implantation temperature is higher than 200 o C.

International Journal of Molecular Sciences, Jan 5, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Nanomaterials, Jan 2, 2023

Micron, Dec 1, 2014

Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. ... more Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerisedallylamine, an organic compound with the formula C 3 H 5 NH 2. We discuss the use of energy-filtered TEM in the low-energy-loss range as a contrast enhancement mechanism for imaging the organic shells of such particles. We also study electron-beam-induced crystallization and amorphization of the shells and the formation of graphitic-like layers that contain both C and N. The resistance of the samples to irradiation by high-energy electrons, which is relevant for optical tuning and for understanding the degree to which such hybrid nanostructures are stable in the presence of biomedical radiation, is also discussed.

Thin Solid Films, Nov 1, 2009

Highly dispersed and homogeneous titanium dioxide (TiO 2) nanoparticles were synthesized by a sol... more Highly dispersed and homogeneous titanium dioxide (TiO 2) nanoparticles were synthesized by a solvothermal method with polymer gel. Polymer gel is essential for the highly dispersed and homogeneous nanoparticles. First, polyvinyl alcohol (PVA) was dissolved in water at 70°C and cooled to room temperature. Ammonium citratoperoxotitanate(IV) [(NH 4) 8 [Ti 4 (C 6 H 4 O 7) 4 (O 2) 4 ]・ 8H 2 O] was subsequently added and dissolved in the PVA solution. Next, water was evaporated from the PVA gel using a microwave. This polymer gel and ethanol as a reaction medium were placed into the Teflon reactor of a stainless-steel autoclave with an internal volume of 100 ml. Thereafter, the autoclave was sealed and kept at 230°C for 18 h. After solvothermal synthesis, the polymer gel was collected and dissolved in water at 50°C-70°C. X-ray diffraction (XRD) measurement, scanning electron microscope (SEM), and transmission electron microscope (TEM) observations were performed for the remaining unresolved polymer gel. XRD confirmed the presence of anatase TiO2. The crystallite particle size was estimated as 6.4 nm (D 101) from the XRD 101 peak using the Scherrer's equation. Highly dispersed and homogeneous TiO 2 nanoparticles were obtained from TEM observation with a particle distribution of 5.6 ± 1.2 nm.

Particle and Fibre Toxicology, Jan 3, 2020

Background: The regulatory definition(s) of nanomaterials (NMs) frequently uses the term 'agglome... more Background: The regulatory definition(s) of nanomaterials (NMs) frequently uses the term 'agglomerates and aggregates' (AA) despite the paucity of evidence that AA are significantly relevant from a nanotoxicological perspective. This knowledge gap greatly affects the safety assessment and regulation of NMs, such as synthetic amorphous silica (SAS). SAS is used in a large panel of industrial applications. They are primarily produced as nanosized particles (1-100 nm in diameter) and considered safe as they form large aggregates (> 100 nm) during the production process. So far, it is indeed believed that large aggregates represent a weaker hazard compared to their nano counterpart. Thus, we assessed the impact of SAS aggregation on in vitro cytotoxicity/biological activity to address the toxicological relevance of aggregates of different sizes. Results: We used a precipitated SAS dispersed by different methods, generating 4 ad-hoc suspensions with different aggregate size distributions. Their effect on cell metabolic activity, cell viability, epithelial barrier integrity, total glutathione content and, IL-8 and IL-6 secretion were investigated after 24 h exposure in human bronchial epithelial (HBE), colon epithelial (Caco2) and monocytic cells (THP-1). We observed that the de-aggregated suspension (DE-AGGR), predominantly composed of nano-sized aggregates, induced stronger effects in all the cell lines than the aggregated suspension (AGGR). We then compared DE-AGGR with 2 suspensions fractionated from AGGR: the precipitated fraction (PREC) and the supernatant fraction (SuperN). Very large aggregates in PREC were found to be the least cytotoxic/biologically active compared to other suspensions. SuperN, which contains aggregates larger in size (> 100 nm) than in DE-AGGR but smaller than PREC, exhibited similar activity as DE-AGGR. Conclusion: Overall, aggregation resulted in reduced toxicological activity of SAS. However, when comparing aggregates of different sizes, it appeared that aggregates > 100 nm were not necessarily less cytotoxic than their nano-sized counterparts. This study suggests that aggregates of SAS are toxicologically relevant for the definition of NMs.

Nanomedicine, Nov 1, 2018

To identify new mechanisms responsible for the radiosensitization effect of gold nanoparticles (G... more To identify new mechanisms responsible for the radiosensitization effect of gold nanoparticles (GNPs). Materials & methods: A549 lung carcinoma cells were incubated with 10-nm GNPs during 6 or 24 h before to be exposed to 25 keV/μm protons or 225 kV x-rays. Results: GNP incubation led to a timedependent mitochondria membrane depolarization, oxidative stress and to x-ray and proton radiosensitization. Moreover, a marked inhibition of thioredoxin reductase was observed. Irradiation of cells invalidated for thioredoxin reductase evidenced a radiosensitization effect, suggesting that this enzyme is a potential GNP target. Conclusion: We suggest that GNPs play a radiosensitizer role by weakening detoxification systems. Altogether, these results open up promising novel strategies for the development of nanotechnologies associated to radiotherapy.

Journal of Nanoparticle Research, Jul 18, 2009

Owing to their phenomenal electrical and mechanical properties, carbon nanotubes (CNT) have been ... more Owing to their phenomenal electrical and mechanical properties, carbon nanotubes (CNT) have been an area of intense research since their discovery in 1991. Different applications for these nanoparticles have been proposed, among others, in electronics and optics but also in the medical field. In parallel, emerging studies have suggested potential toxic effects of CNT while others did not, generating some