Cysteine-grafted nonwoven geotextile: a new and efficient material for heavy metals sorption--Part B.

The development of a new material designed to trap heavy metals from sediments or wastewater, based on a polypropylene non-woven covalently grafted with cysteine, has been reported in a previous paper (Part A). The non-woven was first functionalized with acrylic acid (AA) which is used as spacer, and then cysteine was immobilized on the substrate through covalent coupling in order to obtain the so-called PP-g-AA-cysteine. Some preliminary heavy metals adsorption tests gave interesting results: at 20 °C for 24 h and in a 1000 mg/L heavy metals solution, PP-g-AA-cysteine adsorbs 95 mg Cu/g PP (CuSO4 solution), 104 mg Cu/g PP (Cu(NO3)2 solution), 135 mg Pb/g PP (Pb(NO3)2 solution) and 21 mg Cr/g PP (Cr(NO3)3 solution). In this second part of the work, heavy metals sorption tests were carried out with Cu (II), Pb (II), and Cr (III) separately, in order to determine the sorption capacity of this new sorbent as a function of (i) the heavy metals concentration in the solution, (ii) the contact time with the solution, (iii) the pH and (iv) the ionic strength of the solution containing heavy metals. Moreover, the sorption capacity of PP-g-AA-Cysteine was studied using a polluted solution consisting of a mixture of these different heavy metals. An Electron Paramagnetic Resonance study was finally carried out in order to determine the coordination geometry in the environment of the copper trapped by the PP-g-AA-cysteine.

Cysteine-grafted nonwoven geotextile: a new and efficient material for heavy metals sorption--part A.

Cysteine is an interesting biomolecule in the heavy metals trapping field, thanks to its amino, thiol and carboxylic groups. This amino acid is indeed present in some natural chelating agents: glutathione, phytochelatins and metallothioneins. However, cysteine has never been used in remediation processes. When immobilized on a polypropylene nonwoven (PP) geotextile, an innovative and eco-friendly material is obtained, with potential use in drainage and filtration of wastewaters and sediments. PP was first functionalized with acrylic acid using a low pressure cold plasma process to bring reactive carboxylic functions onto the surface (PP-g-AA). Cysteine was then covalently grafted on this modified PP. The cysteine grafting on PP-g-AA was optimized using response surface methodology, which allowed concluding that the best conditions of immersion without heating consist in: a solution containing 0.229 mol/L of cysteine for 28 h. The materials were characterized by Scanning Electron Microscopy, InfraRed Spectroscopy and X-ray Photoelectron Spectroscopy: evidence of covalent cysteine grafting was given. Preliminary sorption tests at 20 °C and pH = 4.5 with artificially polluted solutions give promising results for divalent heavy metal ions: 95 mg Cu (II) (CuSO4 solution), 104 mg Cu (II) and 135 mg Pb(II) (with NO3(-) counter-ion) per gram of PP are trapped.

Toward the understanding of the interfacial dairy fouling deposition and growth mechanisms at a stainless steel surface: a multiscale approach.

The microstructures of two dairy fouling deposits obtained at a stainless steel surface after different processing times in a pilot plate heat exchanger were investigated at different scales. Electron-Probe Micro Analysis, Time-of-Flight Secondary Ion Mass Spectrometry, Atomic Force Microscopy, and X-Ray Photo-electron Spectroscopy techniques were used for this purpose. The two model fouling solutions were made by rehydrating whey protein in water containing calcium or not. Results on samples collected after 2h processing show that the microstructure of the fouling layers is completely different depending on calcium content: the layer is thin, smooth, and homogeneous in absence of calcium and on the contrary very thick and rough in presence of calcium. Analyses on substrates submitted to 1 min fouling reveal that fouling mechanisms are initiated by the deposit of unfolded proteins on the substrate and start immediately till the first seconds of exposure with no lag time. In presence of calcium, amorphous calcium carbonate nuclei are detected in addition to unfolded proteins at the interface, and it is shown that the protein precedes the deposit of calcium on the substrate. Moreover, it is evidenced that amorphous calcium carbonate particles are stabilized by the unfolded protein. They are thus more easily trapped in the steel roughnesses and contribute to accelerate the deposit buildup, offering due to their larger characteristic dimension more roughness and favorable conditions for the subsequent unfolded protein to depose.

Anticoagulant and antimicrobial finishing of non-woven polypropylene textiles.

The aim of this work is to prepare non-woven polypropylene (PP) textile functionalized with bioactive molecules in order to improve its anticoagulation and antibacterial properties. This paper describes the optimization of the grafting process of acrylic acid (AA) on low-pressure cold-plasma pre-activated PP, the characterization of the modified substrates and the effect of these modifications on the in vitro biological response towards cells. Then, the immobilization of gentamicin (aminoglycoside antibiotic) and heparin (anticoagulation agent) has been carried out on the grafted samples by either ionic interactions or covalent linkages. Their bioactivity has been investigated and related to the nature of their interactions with the substrate. For gentamicin-immobilized AA-grafted samples, an inhibition radius and a reduction of 99% of the adhesion of Escherichia coli have been observed when gentamicin was linked by ionic interactions, allowing the release of the antibiotic. By contrast, for heparin-immobilized AA-grafted PP samples, a strong increase of the anticoagulant effect up to 35 min has been highlighted when heparin was covalently bonded on the substrate, by contact with the blood drop.

Physico-chemical and hygienic property modifications of stainless steel surfaces induced by conditioning with food and detergent.

The effect of repeated conditioning procedures (25 runs), consisting of soiling (milk and meat products) and cleaning steps, on the hygienic status, physico-chemical properties and surface chemical composition of stainless steel (SS) surfaces, was investigated. Five SSs differing in grade and finish were used. Both soiling and surface cleaning/conditioning procedures resulted in a similar increase in the surface contamination with carbon, while the changes in the basic component of the surface free energy depended on the conditioning procedure. The passive film was also affected, the Fe/Cr ratio in particular. The hygienic status was also changed, especially with milk as shown by monitoring the number of residual adhering Bacillus cereus spores after contaminating the surface with spores followed by cleaning. The results show that in food environments, the presence and the nature of conditioning molecules play a major role in the hygienic status of SS surfaces.

Biological behaviour of an endothelial cell line (HPMEC) on vascular prostheses grafted with hydroxypropylgamma-cyclodextrine (HPgamma-CD) and hydroxypropylbeta-cyclodextrine (HPbeta-CD).

The cytocompatibility of cyclodextrins (CDs) grafting on vascular polyester (PET) prostheses for further loading with biomolecules was investigated in this study. Viability tests demonstrated no toxicity of HP-CDs and PolyHP-CDs at 4,000 mg/l with survival rates of 80 to 96%. Proliferation tests using the human pulmonary microvascular endothelial cell line (HPMEC-ST1) revealed an excellent biocompatibility for Melinex (Film form of PET). For Polythese and Polymaille, a good proliferation rate was observed at 3 days (60-80%) but decreased at 6 days (56-73%). For all CD-grafted samples, low proliferation rates were observed after 6 days (35-38%). Vitality tests revealed excellent functional capacities of HPMEC cells after 3 and 6 days for all samples. Adhesion kinetics tests showed a similar adhesion of HPMEC cells on control and Melinex. A low adhesion was observed on Polythese and especially on Polymaille compared to control. After CD grafting, the cell adhesion was decreased. The woven or knitted architecture and CD grafting were the most likely causes of this weak adhesion. The adhesion kinetic test was confirmed by SEM observations and immunocytochemistry. The low proliferation of HPMEC on virgin prostheses and especially on grafted prostheses was not due to a cytotoxic effect, but to the physical surface characteristics of the prostheses.

Vascular prostheses with controlled release of antibiotics Part 2. In vitro biological evaluation of vascular prostheses treated by cyclodextrins.

Viability tests by the colony forming method show no toxicity for all CDs (beta-CD, gamma-CD, HPbeta-CD and HPgamma-CD) and their associated polymer. A survival rate of 100% is observed for all CDs at high concentration 400 ppm. Proliferation tests revealed a low proliferation of L132 cells on grafted vascular prostheses and untreated prostheses and good proliferation on Melinex (film form of PET). A proliferation of 17% is observed after 3 days of incubation and decrease at 4% after 6 days on prostheses. Melinex exhibits a proliferation rate as the controls. Vitality tests confirm proliferation tests and show a good vitality of cells even for low cell amounts. From these experiments it becomes obvious that the decreasing proliferation rate is not a cytotoxic effect but is due to the chemical and/or physical surface characteristics. A similar result is obtained for cell adhesion kinetics between grafted vascular prostheses and control. After 2 h adhesion, a lower adhesion is observed on untreated prostheses. Theses results were confirmed by immunochemistry and morphology tests. This cell adhesion inhibiting effect of the PET prostheses contributes to a better "survival" of vascular prostheses without secondary obstruction or stenosis.

Vascular prostheses with controlled release of antibiotics Part 1: Surface modification with cyclodextrins of PET prostheses.

Vascular prostheses were functionalised with the aim to obtain a slow release of antibiotics in order to reduce postoperative infections. The original process that we present in this paper is based on the use of a family of cage molecules named cyclodextrins (CD). These compounds have the ability to form reversible inclusion complexes with drugs such as antibiotics. The aim of this work was to graft CD onto the prosthesis, so that an antibiotic can be bound on it by this inclusion phenomenon, and then be progressively released over a prolonged period by a complex dissociation mechanism. This paper presents the first part of this research program and concerns mainly the study of the functionalization parameters. It presents surface characterization results of the modified prostheses. The PET prostheses were immersed into a solution containing a cross linking agent, cyclodextrins (beta-CD, gamma-CD, HP-beta-CD and HP-gamma-CD) and a catalyst and were padded. Grafting occurred by the mean of a thermofixation step at a temperature comprised between 140 and 180 degrees C. It was observed that the support was permanently modified when the CD polymer that coated the fibres resisted to the final washing process. Grafting rates of 12 wt% in CD polymer could be reached. It was also observed that the fibre coating reaction induced an increase of the permeability of the grafts.

Physico-chemical and biological evaluation of excimer laser irradiated polyethylene terephthalate (pet) surfaces.

The aim of this work was to investigate the consequences of excimer laser irradiation on the physico-chemical and biological properties of polyethylene terephthalate (PET) films, currently used for medical devices. Three PET films from different origins were studied in the present work, chosen with respect to their chemical and physical properties, which are of high importance for ulterior medical application as vascular prostheses. Multiple assays were carried out to characterize the physical and chemical effects of the laser irradiation: surface morphology tests (light microscopy, Dektak profilometer and confocal laser scanning microscopy) showed the strong transformation of the surface with the laser treatment. Contact angle measurements revealed a significant increase of the surface energy for each PET depending on the applied fluency. Finally XPS characterization of the surface demonstrated the appearance of new chemical species favorable for cell attachment. This aspect had to be strongly considered regarding to the multiple biological effects of laser irradiated surfaces on living cells. Different cell culture experiments were carried out with L132 human epithelial cells after 6-days culture: proliferation and vitality rate, cell adhesion and cell morphology. Results clearly revealed that laser treatment improved cell proliferation (up to 140% with respect to controls), vitality (10% higher than controls), morphology and adhesion kinetics (more than 16% of control). A significant correlation (R2=0.906) was also established on one PET between the fluencies of laser treatment and the cellular response. These results emphasized high importance of the choice of the PET material for a medical application: only one of the three considered PET films showed really improved cellular response.

Vascular PET prostheses surface modification with cyclodextrin coating: development of a new drug delivery system.

PURPOSE: Cyclodextrins (CDs) are torus shaped cyclic oligosaccharides with a hydrophobic internal cavity and a hydrophilic external surface. We performed and analysed an antibiotic binding on Dacron (polyethyleneterephtalate, PET) vascular grafts, previously coated with CDs based polymers. METHODS: The CDs coating process was based on the pad-dry-cure method patented in our laboratory. The Dacron prostheses were immersed into a solution containing a polycarboxylic acid, a cyclodextrin and a catalyst, and placed into a thermofixation oven before impregnation with an antibiotic solution (Vancomycin). Biocompatibility tests were performed with L132 human epithelial cells. The antibiotic release in an aqueous medium was assessed by batch type experiments using UV spectroscopy. RESULTS: Viability tests confirmed that the CDs polymers coating the Dacron fibers were not toxic towards L132 cell. Cell proliferation was similar on coated and uncoated grafts. A linear release of Vancomycin was observed over 50 days. CONCLUSION: Our results demonstrate the feasibility of coating CDs onto vascular Dacron grafts. Biological tests show no toxicity of the different cyclodextrins coated. A linear release of antibiotics was depicted over 50 days, demonstrating that cyclodextrin grafting was an efficient drug delivery system.

Surface analyses of micro-arc oxidized and hydrothermally treated titanium and effect on osteoblast behavior.

Osteoblast adhesion on the implant material surface is essential for the success of any implant in which osteointegration is required. Surface properties of implant material have a critical role in the cell adhesion progress. Titanium and its alloys are widespread and increasingly used as implant material in dentistry and orthopedics because of their excellent biocompatibility, which is attributed to a passive layer of TiO2 on the surface. In this study, the micro-arc oxidizing (MAO) and hydrothermally synthesizing (HS) methods were used to modify the TiO2 layer on the titanium surface. The surface microstructure was observed by scanning electron microscopy. The surface energy was assessed. The mouse osteoblastic cell line (MC3T3-E1) was seeded on the treated surfaces to evaluate their effect on cell behavior. This included cell adhesion kinetics, cell proliferation, cell morphology, and cytoskeletal organization. The surface structure of MAO samples exhibited micropores with a diameter of 1-3 microm, whereas the MAO-HS-treated samples showed additional multiple crystalline microparticles on the microporous surface. The surface energy of MAO and MAO-HS was higher than that of titanium. The cell adhesion rate was higher on the MAO-HS surface than on the MAO and titanium surface, but without any significant difference between them. After 3 days of culture, cells proliferated significantly more on the MAO and titanium surface than on the MAO-HS surface. The cytoskeletal organization was analyzed by actin and vinculin staining on all the samples. We conclude that the MAO and MAO-HS methods change the surface energy of TiO2 layer on the titanium surface. This may have an influence on the initial cell attachment. Other surface characteristics may be involved in the cell proliferation, which is different from cell attachment on the sample surface. A longer-duration cell experiment should be conducted to see the effect on cell differentiation. Future in vivo evaluation may give further evidence to optimize the surface character of this kind of implant material.

Electrochemical and cytocompatibility assessment of NiTiNOL memory shape alloy for orthodontic use.

Orthodontic arcs and wires are mostly realised from alloys and constitute the motor of dental shifting. Ti-base alloys rapidly replaced the formerly used stainless steel wires due to their excellent corrosion resistance, their high mechanical characteristics and their increased biocompatibility. NiTiNOL shape memory alloys add to these advantages their ability of deforming force. NiTiNOL, highly pure Nickel (hp-Ni) and commercially pure titanium (cp-Ti) were tested by electrochemical assays in artificial saliva and in vitro biological tests with L132 cells and HEPM cells. All tests gave concordant results: the electrochemical assays, the proliferation test, the colony forming method, and the inflammatory test clearly show, that nickel is a corrosive and a cytotoxic material. Ti and NiTiNOL are cytocompatible and in particular corrosion resistant. No significant differences are observed for both materials on the electrochemical and the biological level as well. The NiTiNOL shape memory alloy is a master trump for dental practitioners to repair occlusal defects by shifting teeth under optimal biological conditions. In spite of its high Ni-content, it is biocompatible. It considerably reduces the tune of therapeutic treatment, facilitate the occlusal concept and leads to a result of high clinical quality.

[The electrochemical behavior of TiTa30 and TiNb30 alloys for implantology]. / Etude du comportement électrochimique des alliages TiTa30 et TiNb30 pour l'implantologie.

The electrochemical behavior in artificial saliva of TiNb30 and TiTa30 alloys were compared with that of commercial pure titanium. The anodic potential, the current density, the passivation potential and the galvanic corrosion vs. Au were determined. Both alloys have a similar behavior to that of pure titanium. Crevace corrosion, which is very weak in pure Ti, is completely inhibited by the addition of Nb or Ta.

[Pharmaceutical technology: development and research]. / Pharmacotechnie, développement et recherche.

Production of pharmaceutics cannot be compared to the manufacture of consumer goods: pharmaceutical manufacturing is the study and bulk manufacture of the ingredients from which medicines are made, and is concerned with the mixing, preparing, packing, of the ingredients into a dosage form for the patient, in according to the good manufacturing practices (GMP). Development and manufacture are not discrete activities but links in a single chain of activity. Research and development, pharmaceutical training, regulatory requirements: these concepts are present with three ways: bioavailability, targeting and compliance.

[HPLC used in the validation of simple methods for research of degradation products in essential drug tablets]. / Validation par HPLC de méthodes simples pour la recherche de produits de dégradation dans les comprimés de médicaments essentiels.

HPLC have been used to validate simple methods to be employed in developing countries (DC) for the quality control of drugs. As the important lack of analytical material in DC, colorimetric methods have been used. These are subjected to visual appreciation of the color intensity. Two essential drugs have been selected: aspirin, hydrochlorothiazide. For each compound, standardization of concentration's degradation product by colorimetry and HPLC have been achieved in proximity of the restricted norms of pharmacopoeia. These results have been applied to tablets exposed to stressed conditions (t(0) = 60 and humidity = 75%). The results obtained by colorimetric method were similar to HPLC's ones.

[Non-destructive quality control of tablets by photoacoustic infrared spectrometry. Analysis in primary packaging]. / Contrôle de qualité non destructif de comprimés par spectrométrie infrarouge photoacoustique. Analyse sous conditionnement primaire.

We have studied the feasibility of the photoacoustic detection in Fourier transform infrared spectrometry for the quality control of drug tablets. Beyond the non destructive character of the method, the main advantage which has been established is the precocity of impurity detection on the tablet outside. The direct recording of spectra through PVC lead to interesting results for study of tablets under blister.

Corrosion of surgical implants.

Corrosion on orthopaedic implants has been studied. Twelve intramedullary nails and twelve osteosynthesis plates were implanted up to eight and thirteen years, respectively. Analysis of biological fluids from all patients was carried out and revealed high concentrations of nickel and chromium that correlated to the implantation time. All implants were corroded by both crevice and intergranular corrosion. Intergranular corrosion is related to mechanical and heating treatments. Crevice-like corrosion is probably enhanced by sulphur present in amino-acids. Electronic probe analysis shows the reaction study between both sulphur and nickel and sulphur and chromium. These results are compared to the metal distribution in body fluids. After a certain incubation time the corrosion accelerates as is characteristic for crevice-like corrosion processes. Studies of the distribution rate of two Ni-Fe-Cr dental alloys in a cell culture system give similar results: metal-ion release increases with the exposure time.