An improved extraction method for surface dosage of insecticides on treated textile fabrics.

BACKGROUND: Tens of millions of people live in mosquito-infested regions and controlling mosquito-borne diseases is one of the major interventions aimed at alleviating poverty worldwide. The use of insecticide-treated textiles is one of the most widespread control measures. This includes bed nets, battle clothing or, more generally, textiles use for clothing. These textiles are generally treated with permethrin as active ingredient, which is dosed after extraction of the active molecule present throughout the fabric (measured in mg permethrin/g of fabric) and does not take the effective concentration on the textile surfaces into account. The objective of this study was to propose an improved dosage method that enables measurement of the bioavailable or effective part of active ingredients on the surface of textile treated with insecticides. METHODS: The proposed method relies on mechanical extraction of active molecules on the surface of the textile in direct contact with either the skin or with the targeted arthropod. RESULTS: The results showed that the amount of permethrin measured using the current method is about 200 times higher than the effective surface concentration of the insecticide. In addition, the type of weave or knit influences the effective concentrations of permethrin on the surface of the textile. With the current dosage method, the variation in the concentration of permethrin depending on the type of weave is maximum 8%, whereas with the proposed method, it varies by about 50%. These results were confirmed by bioassays, in which the type of weave significantly affected (p < 10-3) the 100% knockdown time of Anopheles gambiae. CONCLUSIONS: The bioefficacy of insecticide treatments of fabrics is directly correlated with the effective concentration of insecticide on the textile surface, which can be quantified using the method proposed. This improved method could be used to redefine the limits of actual concentrations of active substance after assessment of the bioefficacy of the treatment and the risk to human health. Further, it enables assessments of the kinetics of insecticide migration in the case of long-lasting insecticide treatment.

Aging of non-implanted Natrelle™ gel breast implants.

This study questions the aging of non-implanted breast prostheses for a period of 9-60 months. Every 6 months, two non-implanted Natrelle™ prostheses were tested to measure the strength at break, the elongation at break, and the thickness of the shell. Then, the breaking stress was calculated from the preceding quantities. All these quantities were observed by separating the samples taken from the anterior and posterior sides of the prostheses. One-way ANOVA analyses (analysis of variance) were performed to define the influence of aging duration, lot membership, and side. In addition, the elongation at break and the thickness of the shell showed significant variations as a function of aging regardless of the side but without any trend emerging. For other quantities, there were significant disparities between the anterior and posterior sides of the prostheses, differences between prostheses from different lots, and similarities between prostheses from the same lot. Finally, the thickness is an important parameter. Since manufacturing is a manual process, it is necessary to check the thickness, which must be homogeneous on both sides. Always weaker on the anterior side than on the posterior side, it influences the mechanical properties. We recommend, like other studies, that its control be part of the quality controls during manufacturing.

In vitro approach to the dilative behavior of knitted vascular prosthetic grafts.

The purpose of this report is to propose an in vitro approach to predicting the long-term dilative behavior of knitted polyester prosthetic grafts. Various techniques were applied to five warp knitted fabric prosthetic grafts in order to determine the following fabric properties: knitted fabric structure, textile structure, number and respective linear density of threads and strands, and length of yarn in each stitch. Following these investigations, the prosthetic grafts underwent testing to determine specific strength at break, breaking extension, and stress-strain curve. On two prosthetic grafts, image analysis was performed during circumferential tensile strength testing in order to monitor changes in structural features as a function of stress. Changes in the distance between two wales and two courses of stitches and stitch surface were measured. In addition to surface deformation, thickness was measured, using an induction sensor. Study of fabric structure showed many differences between the five models made by different manufacturers. Knit fabric structure was Indeforma in three cases and half-tricot in two. Strand number and size varied greatly from one model to another. Pattern also varied from one model to another, with knit stitch density varying from 1 to 3. Specific strength at break testing showed great differences in the mechanical properties of the grafts. These differences were especially obvious in the first part of the rheograms, which reflects the ability of the graft to comply in response to low-strength forces, i.e., much lower than those necessary to cause rupture. Image analysis of stitch behavior under stress further confirmed differences in graft behavior depending on the fabric structure adopted by the manufacturers. The in vitro approach proposed in this study to analyze the fabric characteristics of knitted prosthetic grafts effectively revealed differences in construction and behavior. These differences could account for differences in the dilative behavior of grafts in vivo.

Fiber heart valve prosthesis: Early in vitro fatigue results.

Transcatheter aortic valve replacement has become today a largely considered alternative technique to surgical valve replacement in patients with high risk for open chest surgery. Biological valve tissue used in the transcatheter devices has shown success over 5 years now, but the procedure remains expensive. Moreover, different studies point out potential degradations that the tissue can undergo when folded to lower diameter and released in calcified environment with irregular geometry, which may jeopardize the durability of the device. The use of synthetic materials, like textile in particular, to replace biological valve leaflets would help reducing the procedure costs, and limit the degradations when the valve is crimped. Textile polyester material has been extensively used in the vascular surgery and is characterized by outstanding folding and strength properties combined with proven biocompatibility. However, the friction effects that occur between filaments and between yarns within a fabric under flexure loading could be critical for the resistance of the material on the long term. The purpose of this study was to assess the early fatigue performances of textile valve prototypes under accelerated cyclic loading up to 200 Mio cycles. Durability tests show that the fibrous material undergoes rearrangements between fibrous elements within the textile construction and the mechanical properties are modified on the long term. But testing is not complete with 200 Mio cycles. The material should be tested up to a higher number of cycles in future work to test the effective long-term durability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 986-992, 2016.

Design, Degradation Mechanism and Long-Term Cytotoxicity of Poly(L-lactide) and Poly(Lactide-co-ϵ-Caprolactone) Terpolymer Film and Air-Spun Nanofiber Scaffold.

Degradable nanofiber scaffold is known to provide a suitable, versatile and temporary structure for tissue regeneration. However, synthetic nanofiber scaffold must be properly designed to display appropriate tissue response during the degradation process. In this context, this publication focuses on the design of a finely-tuned poly(lactide-co-ϵ-caprolactone) terpolymer (PLCL) that may be appropriate for vascular biomaterials applications and its comparison with well-known semi-crystalline poly(l-lactide) (PLLA). The degradation mechanism of polymer film and nanofiber scaffold and endothelial cells behavior cultured with degradation products is elucidated. The results highlights benefits of using PLCL terpolymer as vascular biomaterial compared to PLLA.

Evaluation of an air spinning process to produce tailored biosynthetic nanofibre scaffolds.

We optimised the working parameters of an innovative air spinning device to produce nanofibrous polymer scaffolds for tissue engineering applications. Scanning electron microscopy was performed on the fibre scaffolds which were then used to identify various scaffold morphologies based on the ratio of surface occupied by the polymer fibres on that covered by the entire polymer scaffold assembly. Scaffolds were then produced with the spinning experimental parameters, resulting in 90% of fibres in the overall polymer construct, and were subsequently used to perform a multiple linear regression analysis to highlight the relationship between nanofibre diameter and the air spinning parameters. Polymer solution concentration was deemed as the most significant parameter to control fibre diameter during the spinning process, despite interactions between experimental parameters. Based on these findings, viscosity measurements were performed to clarify the effect of the polymer solution property on scaffold morphology.

Compliance properties of collagen-coated polyethylene terephthalate vascular prostheses.

BACKGROUND: Compliance mismatch between native artery and a prosthetic graft used for infrainguinal bypass is said to be a factor for graft failure. The aim of this study was to develop a technique for measuring the compliance of collagen-coated polyethylene terephthalate (PET) vascular prostheses and to analyze the influence of several key properties on the elastic behavior of the grafts. METHODS: Compliance testing was performed on 3 prostheses with and without internal compliant membrane (ICM). The principle of this test was to study the dimensional changes of prostheses submitted to internal pressure from 30 to 240 mm Hg at intervals of predetermined values. RESULTS: We demonstrated that the ICM created links with the inner surface of the crimps and considerably modified the graft behavior when submitted to internal pressure. The results showed that compliance properties were dependent on the wall thickness and the crimping geometry of textile vascular prostheses. Mechanical analysis predicts the circumferential tensile behavior of these arterial grafts and validates tests for measuring compliance.

Characterization of polyelectrolyte multilayer films on polyethylene terephtalate vascular prostheses under mechanical stretching.

Layer-by-layer (LBL) polyelectrolyte films offer extensive potentials to enhance surface properties of vascular biomaterials. From the time of implantation, PET prostheses are continuously subjected to multiple mechanical stresses such as important distorsions and blood pressure. In this study, three LBL films, namely (1) poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride), (2) poly(L-lysine)/hyaluronan, and (3) poly(L-lysine)/poly(L-glutamic acid) were built on to isolated PET filaments, thread, and vascular prostheses. The three LBL films uniformly covered the surface of the PET samples with rough, totally smooth, and "wrinkled" appearances respectively for (PAH/PSS)(24), (PLL/HA)(24), and (PLL/PGA)(24) systems. We then assessed the behavior of these LBL films, in an aqueous environment [by environmental scanning electronic microscopy (ESEM)], when subjected to unidirectional longitudinal stretches. We found that stretching induces ruptures in the multilayer films on isolated filaments for longitudinal stretches of 14% for (PSS/PAH)(24), 13% for (PLL/PGA)(24), and 30% for (PLL/HA)(24) films. On threads, the rupture limit is enhanced to be respectively 26, 20, and 28%. Most interestingly, we found that on vascular prosthesis no rupture is visible in any of the three multilayers types, even for elongations of 200% (200% undergone by the PET prostheses is representative of those encountered during graft deployment) which by far exceeds elongations observed under physiological conditions (10-20%, blood pressure). In term of mechanical behaviors, these preliminary data constitute a first step toward the possible use of LBL film to coat and functionalize vascular prosthesis.