Properties Of Mesh Research Articles

DNA-Guided Assembly for Fibril Proteins

Current advances in computational modelling and simulation have led to the inclusion of computer scientists as partners in the process of engineering of new nanomaterials and nanodevices. This trend is now, more than ever, visible in the field of deoxyribonucleic acid (DNA)-based nanotechnology, as DNA’s intrinsic principle of self-assembly has been proven to be highly algorithmic and programmable. As a raw material, DNA is a rather unremarkable fabric. However, as a way to achieve patterns, dynamic behavior, or nano-shape reconstruction, DNA has been proven to be one of the most functional nanomaterials. It would thus be of great potential to pair up DNA’s highly functional assembly characteristics with the mechanic properties of other well-known bio-nanomaterials, such as graphene, cellulos, or fibroin. In the current study, we perform projections regarding the structural properties of a fibril mesh (or filter) for which assembly would be guided by the controlled aggregation of DNA scaffold subunits. The formation of such a 2D fibril mesh structure is ensured by the mechanistic assembly properties borrowed from the DNA assembly apparatus. For generating inexpensive pre-experimental assessments regarding the efficiency of various assembly strategies, we introduced in this study a computational model for the simulation of fibril mesh assembly dynamical systems. Our approach was based on providing solutions towards two main circumstances. First, we created a functional computational model that is restrictive enough to be able to numerically simulate the controlled aggregation of up to 1000s of elementary fibril elements yet rich enough to provide actionable insides on the structural characteristics for the generated assembly. Second, we used the provided numerical model in order to generate projections regarding effective ways of manipulating one of the the key structural properties of such generated filters, namely the average size of the openings (gaps) within these meshes, also known as the filter’s aperture. This work is a continuation of Amarioarei et al., 2018, where a preliminary version of this research was discussed.

Non-invasive prediction of the mouse tibia mechanical properties from microCT images: comparison between different finite element models

New treatments for bone diseases require testing in animal models before clinical translation, and the mouse tibia is among the most common models. In vivo micro-Computed Tomography (microCT)-based micro-Finite Element (microFE) models can be used for predicting the bone strength non-invasively, after proper validation against experimental data. Different modelling techniques can be used to estimate the bone properties, and the accuracy associated with each is unclear. The aim of this study was to evaluate the ability of different microCT-based microFE models to predict the mechanical properties of the mouse tibia under compressive load. Twenty tibiae were microCT scanned at 10.4 µm voxel size and subsequently compressed at 0.03 mm/s until failure. Stiffness and failure load were measured from the load–displacement curves. Different microFE models were generated from each microCT image, with hexahedral or tetrahedral mesh, and homogeneous or heterogeneous material properties. Prediction accuracy was comparable among models. The best correlations between experimental and predicted mechanical properties, as well as lower errors, were obtained for hexahedral models with homogeneous material properties. Experimental stiffness and predicted stiffness were reasonably well correlated (R2 = 0.53–0.65, average error of 13–17%). A lower correlation was found for failure load (R2 = 0.21–0.48, average error of 9–15%). Experimental and predicted mechanical properties normalized by the total bone mass were strongly correlated (R2 = 0.75–0.80 for stiffness, R2 = 0.55–0.81 for failure load). In conclusion, hexahedral models with homogeneous material properties based on in vivo microCT images were shown to best predict the mechanical properties of the mouse tibia.

In-vitro Characterization of a Hernia Mesh Featuring a Nanostructured Coating.

Abdominal hernia repair is a frequently performed surgical procedure worldwide. Currently, the use of polypropylene (PP) surgical meshes for the repair of abdominal hernias constitutes the primary surgical approach, being widely accepted as superior to primary suture repair. Surgical meshes act as a reinforcement for the weakened or damaged tissues and support tissue restoration. However, implanted meshes could suffer from poor integration with the surrounding tissues. In this context, the present study describes the preliminary evaluation of a PCL-Gel-based nanofibrous coating as an element to develop a multicomponent hernia mesh device (meshPCL-Gel) that could overcome this limitation thanks to the presence of a nanostructured biomimetic substrate for enhanced cell attachment and new tissue formation. Through the electrospinning technique, a commercial PP hernia mesh was coated with a nanofibrous membrane from a polycaprolactone (PCL) and gelatin (Gel) blend (PCL-Gel). Resulting PCL-Gel nanofibers were homogeneous and defect-free, with an average diameter of 0.15 ± 0.04 μm. The presence of Gel decreased PCL hydrophobicity, so that membranes average water contact angle dropped from 138.9 ± 1.1° (PCL) to 99.9 ± 21.6°, while it slightly influenced mechanical properties, which remained comparable to those of PCL (E = 15.7 ± 2.7 MPa, σR= 7.7 ± 0.6 εR = 118.8 ± 13.2%). Hydrolytic and enzymatic degradation was conducted on PCL-Gel up to 28 days, with maximum weight losses around 20 and 40%, respectively. The meshPCL-Gel device was obtained with few simple steps, with no influences on the original mechanical properties of the bare mesh, and good stability under physiological conditions. The biocompatibility of meshPCL-Gel was assessed by culturing BJ human fibroblasts on the device, up to 7 days. After 24 h, cells adhered to the nanofibrous substrate, and after 72 h their metabolic activity was about 70% with respect to control cells. The absence of detectable lactate dehydrogenase in the culture medium indicated that no necrosis induction occurred. Hence, the developed nanostructured coating provided the meshPCL-Gel device with chemical and topographical cues similar to the native extracellular matrix ones, that could be exploited for enhancing the biological response and, consequently, mesh integration, in abdominal wall hernia repair.

Gamma-ray induced modifications on CdS nanorod mesh:Structural, optical, and electrical properties

In present research work, gamma ray (γ-ray) induced modifications on the cadmium sulphide (CdS) nanorod mesh are investigated. CdS nanorod mesh is deposited on the glass substrate via chemical bath deposition. The samples are irradiated with Co-60 γ-rays with varying dose up to 200 kGy. Structural, optical, and electrical properties of CdS nanorod mesh are examined after exposure to gamma radiation. XRD pattern of pristine and gamma irradiated CdS nanorods revealed no phase transformation but variation in the relative intensity is visible. Moreover, the crystallite size is found to increase with the gamma dose. In addition, FESEM imaging displayed the morphology of pristine and gamma irradiated CdS nanorods. Furthermore, optical properties are also studied to check the effect of gamma irradiation on the respective parameters. The gamma radiation also produces significant changes in the transport properties of CdS nanorods. With gamma dose, CdS nanorod mesh displayed an increment in the current values due to ionization, defects and grain coalescence.

Effect of Loop Length On Thermal Comfort Properties of Mesh Knitted Fabrics

In this study, it is aimed to change the loop length of knitted fabrics with a mesh structure and to investigate the effect of loop length differences on thermal and moisture transmission properties. For this purpose, six fabrics with different loop lengths were produced in two different knittings and yarn types. Thermal conductivity, thermal absorptivity, thermal resistance, air permeability and moisture management properties of these fabrics were measured according to standard test methods. The results showed that as the yarn gets finer and loop length increases, the air permeability values will increase. It was observed that as the loop length increase, the overall moisture management capacity (OMMC) and thermal absorptivity of the fabrics will decrease. The thermal resistance values of two ply textured polyester mesh knitted fabrics decreased with increasing density and the highest loop length two ply textured polyester mesh knitted fabric showed the highest thermal resistance value.

Empirical Analysis of the Impact Strength of Textile Knitted Barrier Meshes

Abstract The assumptions of instrumental methodology for measuring dynamic loads of knitted barrier meshes were defined. A test stand was built, original in terms of both mechanical construction and electronic measuring system, connected to a computer data analysis system. Maximum values of dynamic forces in the mesh fastening strings were determined. The correctness of the strain gauges construction and measurement data transmission systems was confirmed. Tests of multidirectional resistance to dynamic loads in the mesh fastening strings were carried out. The experiment involved dropping a ball with a mass of 5 kg and a diameter of 10 cm, from a height of 1 m and 2 m onto the mesh surface. The potential impact energy equaled Ep1 = 49.05 J and Ep2 = 98.1 J. The tests showed that the highest force values were observed for meshes with square-shaped a-jour structure, and for mesh with diamond-shaped a-jour geometry the force values were lower. A symmetrical forces distribution was observed in all the strings. The highest forces were recorded in the middle strings and the lowest in the outer ones. The conducted tests confirmed the correctness of the adopted constructional solutions of test stand for identification of dynamic stress distribution in mesh fastening strings. The developed method is a useful verification tool for numerical analysis of mechanical properties of barrier meshes.

Assessment of Thorax Finite Element Model Response for Behind Armor Blunt Trauma Impact Loading Using an Epidemiological Database.

Nonperforating ballistic impacts on thoracic armor can cause blunt injuries, known as behind-armor blunt trauma (BABT). To evaluate the potential for this injury, the back face deformation (BFD) imprinted into a clay backing is measured; however, the link between BFD and potential for injury is uncertain. Computational human body models (HBMs) have the potential to provide an improved understanding of BABT injury risk to inform armor design but require assessment with relevant loading scenarios. In this study, a methodology was developed to apply BABT loading to a computational thorax model, enhanced with refined finite element mesh and high-deformation rate mechanical properties. The model was assessed using an epidemiological BABT survivor database. BABT impact boundary conditions for 10 cases from the database were recreated using experimentally measured deformation for specific armor/projectile combinations, and applied to the thorax model using a novel prescribed displacement methodology. The computational thorax model demonstrated numerical stability under BABT impact conditions. The predicted number of rib fractures, the magnitude of pulmonary contusion, and injury rank, increased with armor BFD, back face velocity, and input energy to the thorax. In three of the 10 cases, the model overpredicted the number of rib fractures, attributed to impact location positional sensitivity and limited details from the database. The integration of an HBM with the BABT loading method predicted rib fractures and injury ranks that were in good agreement with available medical records, providing a potential tool for future armor evaluation and injury assessment.

Voss Surfaces: A Design Space for Geodesic Gridshells

The design of envelopes with complex geometries often leads to construction challenges. To overcome these difficulties, resorting to discrete differential geometry proved successful by establishing close links between mesh properties and the existence of good fabrication, assembling and mechanical properties. In this paper, the design of a special family of structures, called geodesic shells, is addressed using Voss nets, a family of discrete surfaces. The use of discrete Voss surfaces ensures that the structure can be built from simply connected, initially straight laths, and covered with flat panels. These advantageous constructive properties arise from the existence of a conjugate network of geodesic curves on the underlying smooth surface. Here, a review of Voss nets is presented and particular attention is given to the projection of normal vectors on the unit sphere. This projection, called Gauss map, creates a dual net which unveils the remarkable characteristics of Voss nets. Then, based on the previous study, two generation methods are introduced. One enables the exploration and the deformation of Voss nets while the second provides a more direct computational technique. The application of theses methodologies is discussed alongside formal examples.

Psychometric Properties and Factor Analysis of Hindi Version of the Meta-Emotion Scale

This study was carried out to establish the construct, convergent and predictive validity of Hindi translation of Meta-emotions Scale in Hindi speaking Indian cultural context. For the purpose 16 to 78 years old 1324 men and women participants with High School education from Chowk and adjoining areas of Varanasi city of Uttar Pradesh, India, completed the Hindi version of 28-items Metaemotions Scale (MES). Factor analysis (principal components) on Hindi version of MES (MES-H) by applying Varimex rotation method with the loading equal to or more than 0.400, Eigen value equal to 1.00, and Scree plot suggested two to three factors, and finally, confirmatory factor analysis by AMO Sindicated a two factor model with an acceptable goodness of model fit on 19 items. The content of 10 items of the first factor and 9 items of second factor yielded two behavioral components, i.e., Positive Meta-emotions and Negative Meta-emotions. The psychometric properties of the MES-H demonstrated good internal consistency with acceptable reliability, construct and convergent validity. The gender and age differences analyses also indicated that women manifested significantly higher positive meta-emotions and negative meta-emotions in comparison to men, and older as compared to younger participants demonstrated significantly high levels of positive meta-emotions indicating good predictive validity. These findings indicated that the MES-Hindi may be considered as a reliable and valid measurement of meta-emotions in Hindi speaking Indian cultural context.

Characterizing the Molecular Architecture of Hydrogels and Crosslinked Polymer Networks beyond Flory-Rehner-I. Theory.

In the early 1940s, Paul Flory and John Rehner published a series of papers on the properties of swellable polymeric networks. Originally intended for vulcanized rubber, their development has since been extensively used and extended to much more complex systems, such as hydrogels, and used to estimate the mesh size of such networks. In this article, we take a look at the development of the Flory-Rehner equation and highlight several issues that arise when using such a theory for the described hydrogel networks. We then propose a new approach and equations to accurately calculate the backbone molecular weight in-between crosslinks while explicitly accounting for the molecular mass of the crosslinker and branch segments. The approach also provides more applicable mesh dimensions, for complex networks with macromeric crosslinkers and/or a high degree of branching, as is the case of biocompatible hydrogels. The approach is finally illustrated by a case study comparing the values obtained with our proposed approach to those using the state-of-the-art approach.

Eco-Friendly All Water-Based Solution Process for Robust Ag Nano-Mesh Transparent Electrodes

Transparent conducting electrodes have attracted substantial attentions as an essential component of various optoelectronic devices. Recently, the grid-structured metal mesh electrodes are considered as highly efficient transparent electrodes that possess high optical transmittance while maintaining sufficient electrical conductivity and are suitable for flexible conductors with isotropic electrical conductivity. Here, we report a simple and effective approach for the fabrication of highly transparent Ag nano-mesh prepared by all water-based solution process. The Ag mesh electrodes were formed by combination of colloidal gold nanoparticles deposition and silver enhancement. The optical and electrical properties of the Ag mesh can be finely tuned by varying condition of gold nanoparticle deposition and silver enhancement. The smallest feature size of the obtained metal mesh patterns is about 700 nm with a thickness of 30-60 nm. The transparent electrodes with the Ag nano-mesh structure exhibit not only excellent electrical conductivity with a sheet resistance of 70 Ω/sq at a transmittance of 96.2% but also strong adhesion strength to substrate which is confirmed by peeling off test. Our all water-based solution processed metal mesh electrodes is applied to transparent heater which is able to heat up to 250 °C at 7 V. Through this study, Not only fabrication of high performance metal mesh but also low cost fabrication without any hazardous wastes is succeeded.This research was funded and conducted under [the Competency Development Program for Industry Specialists] of the Korean Ministry of Trade, Industry and Energy(MOTIE), operated by korea Insstitute for Advancement of Technology (KIAT). (No. P0012453, Next-generation Display Expert Training project for Innovation Process and Equipment, Materials Engineers)

Mechanical properties of warp-knitted hernia repair mesh with various boundary conditions

In this paper, two most representative hernia repair meshes were prepared with 0.15 mm polypropylene monofilaments via warp knitting technology, and their mechanical properties were tested in various aspects. Meanwhile, a focused investigation of the boundary conditions between the sutures and the mesh was simulated in several directions innovatively. The results revealed that the hernia repair mesh with different structures has different mechanical properties, and the mechanical properties of standard hernia repair mesh were superior to that of lightweight hernia repair mesh. In order to reduce foreign body sensation and postoperative adverse reactions significantly, the lightweight hernia repair mesh may be preferred. At the same time, the mesh should be placed in the proper direction to comply with the anisotropy of abdominal wall during operation. The area where the hernia mesh is in contact with the sutures was vulnerable to damage. The curved or wrinkled area of the hernia repair mesh increases with the increase of load, which may lead to poor tissue growth, a strong inflammatory response, and even the recurrence of the hernia. Therefore, the hernia repair meshes with different structures may require unique suture techniques. And they also should be further treated prior to implantation. This study provides a theoretical basis for development, utilization and improvement of meshes. Further research will focus on the biomechanical properties of the mesh after implantation in vivo studies.

Facile fabrication of superhydrophilic/underwater superoleophobic polyvinyl acetate/sodium silicate composite coating for the effective water/oil separation and the study on the anti-fouling property, durability and separation mechanism

In this study, hydrophilic stainless steel meshes for water/oil separation were successfully prepared through the etching and subsequent modification of a polyvinyl alcohol (PVA)–sodium silicate (Na2SiO3) composite. The effects of the surface structure and component on the wetting behavior, separation efficiency, and separation flux were investigated. The long-term stability and anti-abrasion property were also studied. Furthermore, the separation mechanism of the hydrophilic mesh for water/oil separation was proposed based on investigations of the surface roughness, wetting behavior, separation efficiency, and separation flux. The results revealed that Na2SiO3 and PVA-Na2SiO3 coated meshes exhibit superhydrophilicity and underwater superoleophobicity (water contact angle (WCA): <10°, underwater oil contact angle (UOCA): >150°). Most of the prepared meshes could be used for the gravity-driven separation of the water/oil mixture and were characterized by a high separation efficiency (>97.0 %) and a high separation flux (over 1450 L/m2 h). However, during the repetition separation, the superhydrophilic meshes exhibited more stable water films and higher separation fluxes than the other meshes, reflecting the superior anti-oil pollution property of the superhydrophilic meshes. Furthermore, the increase in the roughness of the hydrophobic surface would lead to oil accumulation and growing oil pollution, thereby yielding a considerable decrease in the separation flux after 10-cycle repetition separation. A stable UOCA was obtained for the prepared meshes after abrasion testing. However, compared with the other meshes, the meshes with poor hydrophilicity and a small pore size were more easily polluted by oil and were characterized by lower separation flux during the repetition separation. The results of the mechanism study revealed that the separation efficiency and the separation flux were mainly influenced by the surface roughness, wetting behavior, and water-absorption ability of the surface. Hence, the water film strength was vital for the anti-oil pollution property of the water-removing separation mesh.

Elimination of vortices by wave generation as a hydraulic anti-vortex method

Free-surface vortex formation is one of the undesirable hydraulic phenomena that may occur at intakes during the dewatering reservoir. This research is meant to investigate the effect of waves on formed vortices in vertical intakes numerically by applying STAR-CCM + software. The simulation was conducted to model the free surface and turbulence by volume of fluid and large eddy simulation methods, respectively. Sensitivity analysis was undertaken on different mesh sizes to select appropriate mesh dimensions. Then, verification was performed by Sun and Liu (J Hydraul Res 53:787–796, 2015) experimental data. Results showed that waves reduce or eliminate hydraulic parameters of the formed vortices such as vortex strength, tangential, radial, and axial velocity components. The reduction appeared by average values of 32%, 30%, 22%, and 25% in vortex strength, tangential, radial, and axial velocity components, respectively. Waves also led to decrement in the length and diameter of air-core of vortices about 45% for the former and more than 50% for the latter. In addition, it was concluded that the smaller the waves, the greater their effects would appear on the elimination of the vortex phenomenon. Finally, a relationship between the wave properties, as a hydraulic approach to anti-vortex, and vortex parameters was developed.

Co-electrospun nano-/microfibrous composite scaffolds with structural and chemical gradients for bone tissue engineering

Recent trends in scaffold design for tissue engineering have focused on providing structural, mechanical and chemical cues for guiding cell behaviors. In this study, we presented a structural/compositional gradient nano-/microfibrous mesh by co-electrospinning, using silk fibroin-poly(ε-caprolactone) (SF-PCL) nanofibers and PCL microfibers. The pore size, porosity, and physical property of the gradient meshes were qualified. Cell proliferation of mouse osteoblast-like MC3T3-E1 cells was carried out to estimate the effect of structural and compositional gradients on biocompatibility. Furthermore, the 2-D mesh was rolled up and the compressive property of 3-D cylinder was investigated. The results suggested that the rolled-up gradient cylinder scaffold exhibited higher osteogenic differentiation compared to the pristine nanofibrous cylinder sample. By incorporating Chinese medicine ginsenoside Rg1, sustained release was achieved in composite meshes. Rg1-containing nanofibrous meshes and Rg1 gradient cylinders enhanced the cell proliferation of human umbilical vein endothelial cells (HUVECs). The developed fibrous scaffold may provide structural, compositional, and chemical gradients for bone regeneration. BriefsStructural and chemical gradient fibrous scaffold fabricated by co-electrospinning.

Mechanical and Histological Characteristics of Phasix™ ST Mesh in a Porcine Model of Hernia Repair

Purpose The objective of this study was to determine mechanical and histological properties of Phasix™ ST Mesh in various defect sizes and characterize the tissue replacing Phasix™ ST Mesh in a porcine model of ventral hernia repair. Methods Simulated hernia defects were surgically created in the midline of twenty-four (n = 24) Yucatan pigs. Treatment groups included 8 cm defect sutured closed (buttress) and unclosed 4 cm and 8 cm defect groups. Phasix™ ST Mesh (15 cm diameter circle) was implanted laparoscopically and fixated circumferentially with SorbaFix™ Absorbable Fixation System fasteners. The repair sites underwent mechanical, molecular weight, and histological evaluation at 48 and 72 weeks postimplantation. Results Mechanical testing of Phasix™ ST Mesh-repaired sites revealed similar strengths at both time points for all three repair types, p > 0.05 in all cases (48 weeks: 142.4 ± 6.0 N, 142.3 ± 16.5 N, and 168.8 ± 38.5 N; 72 weeks: 110.0 ± 18.3 N, 138.6 ± 42.2 N, and 160.6 ± 42.0 N for 4 cm defect, 8 cm defect, and 8 cm buttress, respectively. mean ± SEM) No significant differences were observed over time except at 72 weeks postimplantation when the 4 cm defect group exhibited significantly lower strength than the T0 strength of Phasix™ ST Mesh (204.6 ± 5.0 N, p < 0.05). The molecular weight of Phasix™ ST Mesh decreased over time, regardless of repair type. Histological analysis showed comparable mature collagen/fibrovascular tissue around and within the Phasix™ ST Mesh interstices, including the segment of mesh overlying the defect. Conclusion Phasix™ ST Mesh-repaired sites exhibited similar mechanical strengths and histological properties across all defect sizes in this porcine model.

Optimization of Dynamic Mechanical Properties of Knitted Barrier Meshes

Abstract This article focuses on the analysis of mechanical properties of knitted barrier meshes and refers to general problems related to safety engineering. The conducted analysis of the effectiveness of absorbing impact energy by textile barriers, which positively affect the human body, clearly indicates the possibility of applying them in the field of road engineering as a new generation of road barriers. The characteristic features of the new generation of barriers are their openwork multiaxial structure based on various geometric shapes of the a-jour structure. Twenty models of barrier meshes with a-jour structure in the shape of tetragons (squares and diamonds), triangles, regular polygons (hexagons, octagons, and dodecagons), and circles were designed. Simulation research that aimed to optimize the structure of knitted openwork meshes to obtain minimum reduced stresses in strings, knots, and arms of the mesh was performed. The preferred solution is the four-axial eight-thread mesh with square-shaped a-jour structure with stress equal to Δб = 0.43 GPa/kg and the mesh with thickened diamond-shaped a-jour geometry with stress equal to Δб = 0.53 GPa/kg. Low stress values were also recorded for a four-axial six-thread mesh with square a-jour structure, for which Δб = 0.66 GPa/kg. The analyzed mesh models were implemented in the form of dozen designs of stitch constructions based on warp-knitting technology.

О методе расчета модуля непрерывности обратного оператора и его модификаций с приложением к нелинейным задачам геоэлектрики

Рассматриваются априорные оценки неоднозначности (погрешности) приближенных решений условно-корректных нелинейных обратных задач, основанные на модуле непрерывности обратного оператора и его модификациях. Установлена связь модуля непрерывности обратного оператора с разрешающей способностью геофизического метода. Показано, что в классе кусочно-постоянных решений, определенных на заданной сетке параметризации, модуль непрерывности обратного оператора и его модификации монотонно возрастают с увеличением размерности сетки. Предложен метод построения оптимальной сетки параметризации, которая имеет максимальную размерность при условии, что модуль непрерывности обратного оператора не превышает заданной величины. Представлен численный алгоритм расчета модуля непрерывности обратного оператора и его модификаций с использованием алгоритмов Монте-Карло, исследуются вопросы сходимости алгоритма. Предлагаемый метод применим также для расчета классических апостериорных оценок погрешности. Приводятся численные примеры для нелинейных обратных задач геоэлектрики. The article considers a priori estimates of the ambiguity (error) of approximate solutions of conditionally correct nonlinear inverse problems based on the modulus of continuity of the inverse operator and its modifications. It is shown that in the class of piecewise constant solutions defined on a given parametrization grid, the modulus of continuity of the inverse operator and its modifications monotonously increase with increasing mesh dimension. A method is proposed for constructing an optimal parameterization grid that has a maximum dimension provided that the modulus of continuity of the inverse operator does not exceed a given value. A numerical algorithm for calculating the modulus of continuity of the inverse operator and its modifications using Monte Carlo algorithms is presented; questions of convergence of the algorithm are investigated. The proposed method is also applicable for calculating classical posterior error estimates. Numerical examples are given for nonlinear inverse problems of geoelectrics.

Biomimetic double-sided polypropylene mesh modified by DOPA and ofloxacin loaded carboxyethyl chitosan/polyvinyl alcohol-polycaprolactone nanofibers for potential hernia repair applications

Polypropylene (PP) meshes are the most widely used as hernioplasty prostheses. As far as hernia repair is concerned, bacterial contamination and tissue adhesion would be the clinical issues. Moreover, an optimal mesh should assist the healing process of hernia defect and avoid undesired prosthesis displacements. In this present study, the commercial hernia mesh was modified to solve the mentioned problems. Accordingly, a new bi-functional PP mesh with anti-adhesion and antibacterial properties on the front and adhesion properties (reduce undesired displacements) on the backside was prepared. The backside of PP mesh was coated with polycaprolactone (PCL) nanofibers modified by mussel-inspired L-3,4-dihydroxyphenylalanine (L-DOPA) bioadhesive. The front side was composed of two different nanofibrous mats, including hybrid and two-layered mats with different antibacterial properties, drug release, and biodegradation behavior, which were based on PCL nanofibers and biomacromolecule carboxyethyl-chitosan (CECS)/polyvinyl alcohol (PVA) nanofibers containing different ofloxacin amounts. The anti-adhesion, antibacterial, and biocompatibility studies were done through in-vitro experiments. The results revealed that DOPA coated PCL/PP/hybrid meshes containing ofloxacin below 20 wt% possessed proper cell viability, AdMSCs adhesion prevention, and excellent antibacterial efficiency. Moreover, DOPA modifications not only enhanced the surface properties of the PP mesh but also improved cell adhesion, spreading, and proliferation.

Alterations in the mechanical, chemical and biocompatibility properties of low-cost polyethylene and polyester meshes after steam sterilization

IntroductionIn Africa and other Low Resource Settings (LRS), the guideline-based and thus in most cases mesh-based treatment of inguinal hernias is only feasible to a very limited extent. This has led to an increased use of low cost meshes (LCMs, mostly mosquito meshes) for patients in LRS. Most of the LCMs used are made of polyethylene or polyester, which must be sterilized before use. The aim of our investigations was to determine changes in the biocompatibility of fibroblasts as well as mechanical and chemical properties of LCMs after steam sterilization.Material and methodsTwo large-pored LCMs made of polyester and polyethylene in a size of 11 x 6 cm were cut and steam sterilized at 100, 121 and 134 °C. These probes and non-sterile meshes were then subjected to mechanical tensile tests in vertical and horizontal tension, chemical analyses and biocompatibility tests with human fibroblasts. All meshes were examined by stereomicroscopy, scanning electron microscopy (SEM), LDH (cytotoxicity) measurement, viability testing, pH, lactate and glycolysis determination.ResultsEven macroscopically, polyethylene LCMs showed massive shrinkage after steam sterilization, especially at 121 and 134 °C. While polyester meshes showed no significant changes after sterilization with regard to deformation and damage as well as tensile force and stiffness, only the unsterile polyethylene mesh and the mesh sterilized at 100 °C could be tested mechanically due to the shrinkage of the other specimen. For these meshes the tensile forces were about four times higher than for polyester LCMs. Chemical analysis showed that the typical melting point of polyester LCMs was between 254 and 269 °C. Contrary to the specifications, the polyethylene LCM did not consist of low-density polyethylene, but rather high-density polyethylene and therefore had a melting point of 137 °C, so that the marked shrinkage described above occurred. Stereomicroscopy confirmed the shrinkage of polyethylene LCMs already after sterilization at 100 °C in contrast to polyester LCMs. Surprisingly, cytotoxicity (LDH measurement) was lowest for both non-sterile LCMs, while polyethylene LCMs sterilized at 100 and 121 °C in particular showed a significant increase in cytotoxicity 48 hours after incubation with fibroblasts. Glucose metabolism showed no significant changes between sterile and non-sterile polyethylene and polyester LCMs.ConclusionThe process of steam sterilization significantly alters mechanical and structural properties of synthetic hernia mesh implants. Our findings do not support a use of low-cost meshes because of their unpredictable properties after steam sterilization.