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.

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.

Propofol and remifentanil for intubation without muscle relaxant: the effect of the order of injection.

BACKGROUND: Common practice in intubation without muscle relaxant is to inject the opioid drug prior to the hypnotic drug. Because remifentanil reaches adequate cerebral concentration more rapidly than does propofol, we tested the hypothesis that injection of remifentanil after propofol might lead to better intubating conditions. METHODS: Thirty ASA I-II patients scheduled for elective surgery and with no anticipated difficult intubation were enrolled in the study. Five minutes after midazolam 30 microg kg(-1), patients were randomized into two groups: group PR received propofol 2.5 mg kg(-1) followed by remifentanil 1 microg kg(-1), and group RP received remifentanil 1 microg kg(-1) followed by propofol 2.5 mg kg(-1). Intubating conditions were compared using a well-validated score, and continuous arterial pressure was recorded non-invasively. RESULTS: Compared with group RP, intubating conditions were significantly better in group PR. The mean arterial pressure decrease was more pronounced in group RP. CONCLUSIONS: We therefore conclude that in premedicated healthy patients with no anticipated risk of difficult intubation, intubating and haemodynamic conditions are better when remifentanil is injected after propofol.

Diagnosis of nosocomial pneumonia in cancer patients undergoing mechanical ventilation: a prospective comparison of the plugged telescoping catheter with the protected specimen brush.

STUDY OBJECTIVES: Quantitative culture of protected samples of lower respiratory tract secretions obtained by a fiberoptic protected specimen brush (PSB) is widely accepted for the diagnosis of ventilator-associated pneumonia (VAP), but this diagnostic procedure is time consuming, expensive, and may give rise to iatrogenic complications, especially in cancer patients who often present with thrombocytopenia. The plugged telescoping catheter (PTC) could be a satisfactory alternative to the PSB in this setting. The aim of the present study was to evaluate the interest of the PTC to diagnose VAP in ventilated cancer patients. DESIGN: A prospective observational study. SETTING: A 15-bed medical-surgical ICU in a comprehensive cancer center. PATIENTS AND INTERVENTIONS: Over a 9-month period, 42 patients suspected of having bacterial VAP during mechanical ventilation underwent 69 bronchial samplings: a blinded PTC and a fiberoptic PSB were performed successively in each case. A positive culture for both sampling procedures was defined as the recovery of > or = 10(3) cfu/mL of at least one potential pathogen. The PSB result was taken as the reference standard. MEASUREMENTS AND RESULTS: The overall agreement between the techniques was 87% (60/69). PTC had a sensitivity of 67%, a specificity of 93%, a positive predictive value of 71%, and a negative predictive value of 91%. CONCLUSIONS: We conclude that the accuracy of the blinded PTC compares well with that of the PSB for the diagnosis of VAP in cancer patients. The sensitivity of the PTC observed herein, which is slightly lower than that described in previous studies, may be due to the blinded nature of the method: the indications for initial or secondary coupling with a directed sampling method in patients with suspicion of localized pneumonia remain to be determined.

Safety of tracheotomy in neutropenic patients: a retrospective study of 26 consecutive cases.

OBJECTIVE: To evaluate the safety of tracheotomy in neutropenic ventilated cancer patients, in terms of infectious and haemorrhagic complications. DESIGN: Retrospective study. SETTING: A medical-surgical intensive care unit in a Cancer-hospital. PATIENTS AND PARTICIPANTS: 26 consecutive patients undergoing a tracheotomy in neutropenic period, from 1987 to 1990. INTERVENTIONS: Tracheotomy, performed at the bedside or in operating room. MEASUREMENTS AND RESULTS: In all neutropenic patients undergoing a tracheotomy, the characteristics and duration of both neutropenia and mechanical ventilation have been recorded. Stomal bleeding and infection, and infectious pneumonias and alveolar haemorrhage have been carefully reviewed. Platelets were transfused in 23 of the 26 patients at the time of the procedure; no local haemorrhage was observed. Neither stomal nor pulmonary infections secondary to tracheotomy were noted. No respiratory worsening was attributable to the tracheotomy. Nineteen patients (73%) died in ICU, without direct link between tracheotomy and death. CONCLUSIONS: These findings suggest that a tracheotomy can be safely performed in neutropenic patients requiring mechanical ventilation.