Polypropylene Surgical Mesh Research Articles

VIABILITY OF BLOOD LEUKOCYTES OF RATS AFTER IMPLANTATION OF POLYPROPYLENE SURGICAL MESH WITH A TANTALUM-BASED COATING AND ITS DERIVATIVES

Aim. To investigate the viability and types of cell death of peripheral blood leukocytes in experimental animals after implantation of surgical meshes with a tantalum-based coating and its derivatives. Materials and methods. The experimental group included 40 male rats of the WAG population. Polypropylene surgical mesh was surgically implanted between the abdominal wall and sections of the large intestine with different types of coatings. After 28 days, collected blood was analyzed by a BD FACSCanto™ II flow cytometer. Results. It was determined that there were no significant changes in the viability of blood leukocytes between the animals of the intact group and the group of animals that underwent surgery without implantation. Analysis of leukocyte viability in groups of rats implanted with tantalum and tantalum oxide-coated meshes showed a slight decrease in viable cells compared with the results of the intact group. At the same time, the percentage of necrotic cells showed a slight increase. In the group of rats implanted with a mesh with tantalum nitride-coated, a decrease in viable leukocytes was determined in comparison with the results of the intact group by 12,9%, while the percentage of necrotic leukocytes was 3,8% higher. A 16,2% decrease in viable leukocytes was determined in the group of rats implanted with a non-coated mesh compared to the results of the intact group. At the same time, the percentage of necrotic cells was 6,9% higher. Conclusions. Implantation of uncoated and tantalum nitride-coated surgical meshes was found to decrease the percentage of viable blood leukocytes in rats compared to intact animals, while implantation of tantalum- and tantalum-oxide-coated surgical meshes did not significantly decrease viable white blood cells. leukocytes.

Визначення білків гострої фази в крові щурів після імплантації поліпропіленових хірургічних сіток із покриттям на основі танталу та його похідних

At present, more than 30 types of polypropylene surgical meshes are available in the world, but the statistics regarding the secondary inflammatory process after implantation still remain disappointing. Since polypropylene surgical meshes do not decompose well in the body, they can stimulate the surrounding tissuesto develop an inflammatory process that causes adhesions. For the past 50 years, tantalum has been successfully used to produce biocompatible medical implants in surgery, orthopedics, and dentistry. Its excellent anti-inflammatory and antibacterial properties have been repeatedly noted, indicating the possibility of its use as a coating for mesh implants. In order to better predict the outcome after implantation of biomedical materials, it is important to determine the content of acute phase proteins, namely C-reactive protein, haptoglobin and ceruloplasmin. The aim of the study is to determine the content of acute phase proteins, namely C-reactive protein, haptoglobin and ceruloplasmin in the blood of rats after implantation of surgical meshes coated on the basis of tantalum, tantalum oxide and tantalum nitride. Materials and methods. The experimental group included 40 male rats of the WAG population. With the help of surgical intervention, a polypropylene surgical mesh measuring 15x15 mm was implanted between the abdominal wall and various sections of the colon. 28 days after surgery, the experimental animals were decapitated by cervical dislocation. Blood samples were used to determine the content of C-reactive protein, the content of haptoglobin and the content of ceruloplasmin. Results and discussion. The content of C-reactive protein in the blood of rats was statistically 260 % higher in the experimental group implanted with uncoated surgical mesh and 228.8 % higher in the experimental group implanted with polypropylene surgical mesh with tantalum nitride coating in compared with the results in the group of intact animals. Haptoglobin content was statistically 110.5 % higher and ceruloplasmin was statistically 52.6 % higher in the uncoated surgical mesh group compared to the results of the intact animal group. We obtained similar results in the experimental group, which was implanted with a polypropylene surgical mesh with a coating based on tantalum nitride. The content of haptoglobin was 130 % higher and the content of ceruloplasmin was 50.6 % higher statistically compared to the results of the group of intact animals. The C-reactive protein content was 113.3 % and 95.5 % higher, respectively, in the groups implanted with polypropylene surgical meshes with a coating based on tantalum and tantalum oxide compared to the results in the group of intact animals. The content of haptoglobin in the tantalum-based coating group was 83.8 % higher and the content of ceruloplasmin was 32.6 % higher compared to the results obtained in the group of intact animals. In the tantalum oxide- based group, the haptoglobin content was 60.1 % higher and the ceruloplasmin content was 29.3 % higher compared to the results obtained in the intact animal group. Conclusion. Based on the results of the study, it was established that polypropylene surgical meshes coated with tantalum and tantalum oxide significantly reduce the inflammatory reaction compared to uncoated meshes and meshes coated with tantalum nitride. This is supported by lower levels of key inflammatory markers, indicating improved biocompatibility and anti-inflammatory effects of tantalum and tantalum oxide coatings.

ГЕНЕРАЦІЯ АКТИВНИХ ФОРМ КИСНЮ ЛЕЙКОЦИТАМИ КРОВІ ЩУРІВ ПІСЛЯ ІМПЛАНТАЦІЇ ХІРУРГІЧНОЇ СІТКИ З ПОКРИТТЯМ НА ОСНОВІ ТАНТАЛУ

Introduction. Over the past 20 years, polypropylene has become the main material used in hernioplasty, and has proven itself as an excellent material for the restoration of the abdominal wall during hernia repair. Since polypropylene surgical meshes do not decompose well in the body, they can stimulate the development of an inflammatory process in the surrounding tissues, which subsequently causes adhesions. The development of a postoperative inflammatory process after implantation of polypropylene surgical meshes is observed in 30–40 % of patients. This affects the management of the postoperative period, increases the time of stay of patients in the hospital and their period of convalescence. These data force scientists to continue the search for the optimal surgical mesh, which would suit specialists not only from the side of the physical properties of the surgical mesh, but also from the side of its biocompatible and anti-inflammatory properties. Tantalum is successfully used to produce biocompatible medical implants in surgery, orthopedics and dentistry. In previous studies, we have repeatedly noted its excellent anti-inflammatory and antibacterial properties, indicating the possibility of its use as a coating for mesh implants. One of the typical responses to surgical intervention is the generation of reactive oxygen species by leukocyte neutrophils, which are signaling molecules that damage the endothelium of vessels and promote the migration of cells of the immune system to the center of inflammation. The aim of the study – to determine the generation of reactive oxygen species in leukocytes of rats of the control group and experimental rats with implantation of uncoated and tantalum-based surgical meshes. Materials and Methods. ROS generation was assessed in rat blood leukocytes using the dye 2,7-dichlo­ro­dihydrofluorescein diacetate (H2DCFDA) by flow cytometry 28 days after implantation of uncoated and tantalum-coated surgical meshes. Results and Discussion. Analyzing the obtained results, it was determined that the use of tantalum-based surgical meshes does not cause excessive generation of ROS by leukocytes, in contrast to the use of an implant without a coating. Implantation of uncoated surgical mesh caused excessive production of reactive oxygen species in blood leukocytes of rats, as evidenced by statistically significant differences in the mean fluorescence intensity of 2,7- dichlorodihydrofluorescein diacetate. Conclusions. The use of tantalum-based surgical meshes causes less generation of ROS in leukocytes compared to the use of uncoated surgical meshes, and does not provoke the development of adhesions and purulent-septic processes in the postoperative period, which is confirmed by a morphological study. This determines the possibility of their use in surgical practice to improve the durability and stability of use as biomedical implants and prevention of adhesion formation.

Determination of the status of the antioxidant system in rats after implantation of polypropylene surgical mesh with a coating based on tantalum and its derivatives

For the past 10 years, specialists in hernioplasty have noted that there is a problem with the occurrence of an adhesion process after the implantation of surgical meshes. In the future, tantalum-based coatings may become an inhibitor of the development of adhesion and inflammatory processes after surgical mesh implantation. The aim of our study was to determine the state of the antioxidant system by the activity of superoxide dismutase 1 and catalase in the blood of rats after implantation of surgical meshes coated on the basis of tantalum, tantalum oxide and tantalum nitride. After acclimatization, which lasted 21 days, the experimental animals were divided into 6 groups by random sampling: the first (intact) group included 6 rats. The second group included 6 rats that underwent surgery, but without implementation of a surgical mesh. The third group included 7 rats with an implanted surgical mesh coated with tantalum. The fourth group included 7 rats with an implanted surgical mesh covered with tantalum oxide. The fifth group includes 7 rats with an implanted surgical mesh covered with tantalum nitride. The sixth group included 7 rats with an implanted surgical mesh without a coating. To achieve the goal, 40 laboratory rats were implanted with surgical meshes between the abdominal wall and various sections of the large intestine. After 28 days, the activity of SuperOxide Dismutase 1 (SOD 1) and catalase was determined in the blood of the animals. SOD 1 activity was statistically 126.3% higher, and catalase activity was 92.5% higher in the experimental group with surgical mesh without coating. SOD 1 activity was 126.6% higher and catalase activity was 100.0% higher in the experimental group with tantalum nitride coated surgical mesh. In the groups implanted with polypropylene surgical meshes coated with tantalum and tantalum oxide, the activity of SOD 1 was higher by 86.2% and 97.1%, respectively, and the activity of catalase was higher by 70.3% and 67.6%, respectively. As a result of the study, we came to the conclusion that coatings made of tantalum and tantalum oxide demonstrate high biocompatibility in comparison with the results of a group of experimental animals that were implanted with a surgical mesh without a coating. The use of tantalum and tantalum oxide coatings provides a protective effect of the implant against oxidative damage, which indicates their potential to improve the effectiveness of the use of surgical meshes. Keywords: tantalum oxide, superoxide dismutase 1, catalase.

Accelerated in vitro oxidative degradation testing of polypropylene surgical mesh.

Polypropylene (PP) surgical mesh had reasonable success in repair of hernia and treatment of stress urinary incontinence (SUI); however, their use for the repair of pelvic organ prolapse (POP) resulted in highly variable results with lifelong complications in some patients. One of several factors that could be associated with mesh-related POP complications is changes in the properties of the implanted surgical mesh due to oxidative degradation of PP in vivo. Currently, there are no standardized in vitro bench testing methods available for assessing the susceptibility to oxidative degradation and estimating long-term in vivo stability of surgical mesh. In this work, we adapted a previously reported automated reactive accelerated aging (aRAA) system, which uses elevated temperatures and high concentrations of hydrogen peroxide (H2 O2 ), for accelerated bench-top oxidative degradation testing of PP surgical mesh. Since H2 O2 is highly unstable at elevated temperatures and for prolonged periods, the aRAA system involves a feedback loop based on electrochemical detection methods to maintain consistent H2 O2 concentration in test solutions. Four PP mesh samples with varying mesh knit designs, filament diameter, weight, and % porosity, were selected for testing using aRAA up to 4 weeks and characterized using thermal analysis, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and scanning electron microscopy (SEM). Additionally, the oxidation index (OI) values were calculated based on the FTIR-ATR spectra to estimate the oxidative degradation and oxidation reaction kinetics of PP surgical mesh. The OI values and surface damage in the form of surface flaking, peeling, and formation of transverse cracks increased with aRAA aging time. The aRAA test method introduced here could be used to standardize the assessment of long-term stability of surgical mesh and may also be adopted for accelerated oxidative degradation testing of other polymer-based medical devices.

Characterization and quantification of oxidative stress induced particle debris from polypropylene surgical mesh

AbstractExplanted polypropylene (PP) surgical mesh has frequently been reported to show surface alterations, such as cracks and flaking. However, to date the consequence of PP mesh degradation is not clearly understood, particularly its potential to influence the biological host response of surrounding tissues. Of particular concern is a possible host reaction to polypropylene particles released through degradation of surgical mesh in vivo. This concern is driven by previous studies which have postulated that an oxidative stress environment has the potential to etch away particles from the surface of a PP fibers. The release of such particles is of considerable significance as particles in the nano‐ to micro range have been shown to have the capacity to irritate cells and stimulate the immune system. The authors are not aware of any previous studies that have attempted to characterize, quantify or identify any particles released from PP mesh after exposure to an oxidative stress environment. Characterization of the PP mesh, post oxidative stress exposure, including identification of particles was achieved through application of a range of techniques: low voltage‐scanning electron microscopy (LV‐SEM), pyrolysis gas chromatography mass spectrometry (Pyr‐GCMS), nano‐Fourier transform infrared spectroscopy (nano‐FTIR), scattering‐type, scanning near‐field optical microscopy (s‐SNOM), atomic force microscopy (AFM), attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) and uniaxial tensile testing. The findings of this study indicate that oxidative stress alone is a major factor in the production of PP particle debris. PP debris identified within solution, using Pyr‐GCMS, was shown to be in order of the micron scale.

Characterization in respect to degradation of titanium-coated polypropylene surgical mesh explanted from humans.

Titanium-coated polypropylene (Ti-PP) mesh was introduced in 2002 as a surgical mesh for the treatment of hernias and shortly after for pelvic floor surgery, with the aim of improving biocompatibility when compared to non-titanised/regular PP mesh implants. The application of a titanium coating could also be beneficial to address concerns regarding the exposure of PP in an in vivo environment. Many studies have shown that PP, although it is widely accepted as a stable polymer, is subject to oxidation and degradation, such degradation affects the mechanical behavior, that is, the stiffness and tensile strength of PP mesh. Despite the wide clinical use of Ti-PP surgical meshes, no study has yet investigated the residual material properties post clinical deployment and subsequent explantation. In this study, two explanted Ti-PP mesh samples each having different incorporation durations from two patients were examined. Material analysis conducted within this study includes the following techniques: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, low voltage - scanning electron microscopy (LV-SEM), backscattered electron (BSE) imaging, energy dispersive X-ray spectroscopy (EDS) and secondary election hyperspectral imaging (SEHI). The hypothesis of this study is that the Ti coating successfully shields the PP mesh from oxidative stress in vivo and thus protects it from degradation. The results of this analysis show for the first time evidence of bulk oxidation, surface degradation, and environmental stress cracking on explanted Ti-PP meshes.

8-isoprostane as a marker of oxidative stress in experimental animals after implantation of surgical mesh with a coating based on tantalum and its derivatives

Nowadays, the world observes the problem of adhesion process after implantation of polypropylene surgical meshes, which occurs in about 30–40 % of patients in the postoperative period. Over the past 30 years, tantalum and its derivatives have proven themselves as materials for biomedical implants in dentistry and orthopedics. In the future, tantalum-based coatings may become an inhibitor of the development of adhesion and inflammatory processes after surgical mesh implantation. In order to better predict the implantation of biomedical materials, it is important to determine the markers of the development of oxidative stress. A change in the concentration of biomarkers of the state of the oxidants system, in particular 8-isoprostane, can indicate the development of pathological conditions under the conditions of oxidative stress, which can have a significant impact on the viability of cells after surgical intervention. The aim of the study is to determine the concentration of 8-isoprostane in the blood of rats after implantation of surgical meshes coated with tantalum and tantalum oxide. Materials and methods. The experimental group included 36 male rats of the WAG population weighing 240 ± 20 g. A 15x15 mm polypropylene surgical mesh was surgically implanted between the abdominal wall and various sections of the colon. Anesthesia was performed using the intraperitoneal route of administration of the drug «Relax» BioTestLab, Ukraine) at a dose of 8 mg/kg. After 28 days, the experimental animals were decapitated by cervical dislocation, and blood was immediately collected in sterile K2 EDTA VACUTAINER tubes (BD Vacutainer®). Blood samples were used to determine the content of 8-isoprostane in the blood by enzyme-linked immunosorbent assay using the «8-isoprostane EIA KIT» kit (Cayman Chemical Company, USA) according to the manufacturer’s instructions on the «Solar» PV-1251C spectrophotometer. Results and discussion. The content of 8-isoprostane in blood plasma was statistically 158,6 % higher in the experimental group implanted with uncoated surgical mesh and 171,5 % higher in the experimental group implanted with polypropylene surgical mesh with tantalum nitride coating in comparison with the results of the control group. The concentration of 8-isoprostane in the blood of rats after implantation of polypropylene surgical meshes with a coating based on tantalum and tantalum oxide was higher by 102,6 % and 111,1 %, respectively, compared to the results obtained in the group of intact animals, which indicates their better biocompatibility compared to the results of the groups implanted with uncoated and coated tantalum nitride surgical mesh. Conclusion. The obtained results indicate that coatings based on tantalum and tantalum oxide inhibit lipid peroxidation and demonstrate excellent biocompatibility and anti-inflammatory effect, which makes it possible to consider their future use in hernioplasty.

New-generation synthetic implants for the surgical correction of pelvic organ prolapse and stress urinary incontinence: design and testing

Introduction. Up to 50.0% of postpartum women experience stress urinary incontinence (SUI) and pelvic organ prolapse (POP). One of the most common and pathogenetically substantiated methods for surgical correction of severe SIU and POP is prosthetic reconstruction of the pelvic floor, involves the use of monofilament polypropylene surgical meshes through vaginal or laparoscopic access.. However, this way is associated with specific problems, i.e., primarily mucosal erosions, and pelvic pain. This has served as a trigger for the development of new materials that reduce the likelihood of such side effects.Objective. To develop the new-generation synthetic implants for surgical correction of stress urinary incontinence and pelvic organ prolapse.Materials and methods. The main development stages: 1. design of an experimental sample of a synthetic implant (evaluation of basic, physical and mechanical properties). 2. test of an experimental sample obtained in vitro.Results. A bioresorbable polypropylene ligature delivery system was developed and manufactured in two variants: for the POP correction (mesh tape with a width of 13 – 15 mm) and for the SUI correction (mesh tape with a width of 10 – 11 mm).Conclusion. Based on the results of the in vitro tests, we can conclude that the synthetic implants developed are able to provide physiological longitudinal (axial) support of the necessary pelvic floor sections and reduce the risk of postoperative complications. Further in vivo studies are required to assess the response of living tissue to the implantation of this type of synthetic implants.

Dual-Responsive Polypropylene Meshes Actuating as Thermal and SERS Sensors.

Polypropylene (PP) surgical meshes, with different knitted architectures, were chemically functionalized with gold nanoparticles (AuNPs) and 4-mercaptothiazole (4-MB) to transform their fibers into a surface enhanced Raman scattering (SERS) detectable plastic material. The application of a thin layer of poly[N-isopropylacrylamide-co-N,N'-methylene bis(acrylamide)] (PNIPAAm-co-MBA) graft copolymer, covalently polymerized to the mesh-gold substrate, caused the conversion of the inert plastic into a thermoresponsive material, resulting in the first PP implantable mesh with both SERS and temperature stimulus responses. AuNPs were homogeneously distributed over the PP yarns, offering a clear SERS recognition together with higher PNIPAAm lower critical solution temperature (LCST ∼ 37 °C) than without the metallic particles (LCST ∼ 32 °C). An infrared thermographic camera was used to observe the polymer-hydrogel folding-unfolding process and to identify the new value of the LCST, connected with the heat generation by plasmonic-resonance gold NPs. The development of SERS PP prosthesis will be relevant for the bioimaging and biomarker detection of the implant by using the plasmonic effect and Raman vibrational spectroscopy for minimally invasive interventions (such as laparoscopy), to prevent patient inflammatory processes. Furthermore, Raman sources have been proved to not damage the cells, like happens with near-infrared irradiation, representing another advantage of moving to SERS approaches. The findings reported here offer unprecedented application possibilities in the biomedical field by extrapolating the material functionalization to other nonabsorbable polymer made devices (e.g., surgical sutures, grapes, wound dressings, among others).

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.

A novel characterisation approach to reveal the mechano-chemical effects of oxidation and dynamic distension on polypropylene surgical mesh.

Polypropylene (PP) surgical mesh, used successfully for the surgical repair of abdominal hernias, is associated with serious clinical complications when used in the pelvic floor for repair of stress urinary incontinence or support of pelvic organ prolapse. While manufacturers claim that the material is inert and non-degradable, there is a growing body of evidence that asserts PP fibres are subject to oxidative damage and indeed explanted material from patients suffering with clinical complications has shown some evidence of fibre cracking and oxidation. It has been proposed that a pathological cellular response to the surgical mesh contributes to the medical complications; however, the mechanisms that trigger the specific host response against the material are not well understood. Specifically, this study was constructed to investigate the mechano–chemical effects of oxidation and dynamic distension on polypropylene surgical mesh. To do this we used a novel advanced spectroscopical characterisation technique, secondary electron hyperspectral imaging (SEHI), which is based on the collection of secondary electron emission spectra in a scanning electron microscope (SEM) to reveal mechanical–chemical reactions within PP meshes.

Tissue remodeling macrophages morphologically dominate at the interface of polypropylene surgical meshes in the human abdomen

BackgroundMesh implants are widely used to reinforce the abdominal wall, although the inevitable inflammatory foreign body reaction (FBR) at the interface leads to complications. Macrophages are suspected to regulate the subsequent scar formation, but it is still unclear whether adequate fibrous scar formation with collagen deposition depends mainly on the presence of M1 or M2 macrophages.MethodsThis study investigated the FBR to seven human polypropylene meshes, which were removed after a median incorporation time of 1 year due to the primary complaint of recurrence. Using immunofluorescence, the FBR was examined in six regional zones with increasing distance from the mesh fibers up to 350 µm, based on the cell densities, macrophage M1 (CD86) and M2 (CD163, CD206) phenotypes, deposition of collagen-I and -III, and expression of matrix metalloproteinase-2 (MMP-2) and -8 as indicator of collagen degradation.ResultsAll mesh–tissue complexes demonstrated a decrease in cell density and macrophages with distance to the mesh fibers. Overall, about 60% of the macrophages presented an M2 phenotype, whereas only 6% an M1 phenotype. Over 70% of macrophages showed co-expression with collagen-I or -III and over 50% with MMP-2.ConclusionsThe chronic FBR to polypropylene meshes is associated with an M2 macrophage response, which is accompanied by collagen deposition and MMP-2 expression. These findings challenge the idea that mainly M1 macrophages are related to inflammation and highlights that iatrogenic attempts to polarize these cells towards the M2 phenotype may not be a solution to ameliorate the long-term foreign body reaction.

Nonthermal plasma treatment of polymers modulates biological fouling but can cause material embrittlement

Plasma-based treatment is a prevalent strategy to alter biological response and enhance biomaterial coating quality at the surfaces of biomedical devices and implants, especially polymeric materials. Plasma, an ionized gas, is often thought to have negligible effects on the bulk properties of prosthetic substrates given that it alters the surface chemistry on only the outermost few nanometers of material. However, no studies to date have systematically explored the effects of plasma exposure on both the surface and bulk properties of a biomaterial. This work examines the time-dependent effects of a nonthermal plasma on the surface and bulk (i.e. mechanical) properties of polymeric implants, specifically polypropylene surgical meshes and sutures. Findings suggest that plasma exposure improved resistance to fibrinogen adsorption and Escherichia coli attachment, and promoted mammalian fibroblast attachment, although increased duration of exposure resulted in a state of diminishing returns. At the same time, it was observed that plasma exposure can be detrimental to the material properties of individual filaments (i.e. sutures), as well as the structural characteristics of knitted meshes, with longer exposures resulting in further embrittlement and larger changes in anisotropic behavior. Though there are few guidelines regarding appropriate mechanical properties of surgical textiles, the results from this investigation imply that there are ultimate exposure limits for plasma-based treatments of polymeric implant materials when structural properties must be preserved, and that the effects of a plasma on a given biomaterial should be examined carefully before translation to a clinical scenario.

Laparoscopy for the Treatment of Congenital Hernia: Use of Surgical Meshes and Mesenchymal Stem Cells in a Clinically Relevant Animal Model.

More than a century has passed since the first surgical mesh for hernia repair was developed, and, to date, this is still the most widely used method despite the great number of complications it poses. The purpose of this study was to combine stem cell therapy and laparoscopy for the treatment of congenital hernia in a swine animal model. Porcine bone marrow-derived mesenchymal stem cells (MSCs) were seeded on polypropylene surgical meshes using a fibrin sealant solution as a vehicle. Meshes with (cell group) or without (control group) MSCs were implanted through laparoscopy in Large White pigs with congenital abdominal hernia after the approximation of hernia borders (implantation day). A successive laparoscopic biopsy of the mesh and its surrounding tissues was performed a week after implantation, and surgical meshes were excised a month after implantation. Ultrasonography was used to measure hernia sizes. Flow cytometry, histological, and gene expression analyses of the biopsy and necropsy samples were performed. The fibrin sealant solution was easy to prepare and preserved the viability of MSCs in the surgical meshes. Ultrasonography demonstrated a significant reduction in hernia size 1 week after implantation in the cell group relative to that on the day of implantation (p < 0.05). Flow cytometry of the mesh-infiltrated cells showed a non-significant increase of M2 macrophages when the cell group was compared with the control group 1 week after implantation. A significant decrease in the gene expression of VEGF and a significant increase in TNF expression were determined in the cell group 1 month after implantation compared with gene expressions in the control group (p < 0.05). Here, we propose an easy and feasible method to combine stem cell therapy and minimally invasive surgical techniques for hernia repair. In this study, stem cell therapy did not show a great immunomodulatory or regenerative effect in overcoming hernia-related complications. However, our clinically relevant animal model with congenital hernia closely resembles the clinical human condition. Further studies should be focused on this valuable animal model to evaluate stem cell therapies in hernia surgery.

Thoracic Wall Reconstruction: Surgical Planning in Extended Malignant Resections.

The reconstruction of defects in thoracic wall remains a challenge for plastic surgeons. Advances in surgical treatment of illnesses of thoracic wall have been fostering the treatment of lesions within more advanced levels. Consequently, larger and more complex defects are generated, demanding soft tissue covering and framework repair. The aim of this study was to report the experience in chest wall reconstruction and demographics of a tertiary cancer center. All patients submitted to thoracic wall reconstruction by the plastic surgery department from January 2012 to May 2018 in a tertiary cancer center were evaluated. Thirty-two patients have undergone thoracic wall reconstruction. The majority of patients in our series were submitted to surgical treatment of locally advanced breast cancer (84.3%). The most common defect location was the right anterolateral region (65.6%). The latissimus dorsi musculocutaneous flap was the most used in thoracic wall reconstructions. Three cases of thoracectomy with rib resection were reconstructed with methylmethacrylate and polypropylene surgical mesh associated with musculocutaneous flap. Four patients presented major complications, and 12 patients (37.5%) presented minor complications. There were no deaths related to procedures or instability of thoracic wall. Twenty-two patients presented progression of the disease, and 16 died due to the primary pathology. Extended resection of the chest wall is associated in most cases with advanced disease, especially advanced breast cancer. Despite poor prognosis associated to locally advanced disease, it is imperative to perform chest wall reconstruction and allow the patient to continue adjuvant therapy (radiotherapy or chemotherapy) and improve quality of life.

Surface-Functionalized Polypropylene Surgical Mesh for Enhanced Performance and Biocompatibility.

Polypropylene (PP) surgical mesh has attracted vast attention due to its chemical inertness and excellent mechanical properties. However, improvement is necessary to enhance its biocompatibility and to prevent unwanted tissue adhesion. This study addresses these issues through surface modification of plasma-activated PP mesh with a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer. Reaction time and monomer concentration have been optimized to achieve the optimal biocompatibility with reduction in protein adsorption. Attenuated total reflection-Fourier transform infrared spectra confirmed the grafting of the MPC polymer (PMPC) to the plasma-activated polypropylene (PPP) mesh. Scanning electron microscopy images and energy-dispersive X-ray (EDX) line spectra exhibited morphological changes and specifically PMPC grafting to the surface of PPP mesh, due to the presence of a significant amount of phosphorus (P) on the grafted PPP mesh. PMPC-grafted polypropylene (PPP-PMPC) showed a significant reduction in contact angle as well as the amount of adsorbed bovine serum albumin (BSA) protein in comparison with pristine PP mesh. The highest reduction in protein adsorption and the lowest contact angle were achieved at the monomer concentration of 0.3 M and the reaction time of 90 min. A longer reaction time and higher monomer concentration resulted in clogging within the mesh pores. MTT assay results (∼90% cell viability) confirmed the nontoxicity of the PMPC-grafted mesh, while optical microscopic and SEM images showed increased resistance of cell attachment to the surface of PMPC-grafted mesh. The results show that PPP-PMPC can be a promising biomaterial to address the current issues in biocompatibility and reduction in adhesion after surgery.

Methacrylic Acid Copolymer Coating Enhances Constructive Remodeling of Polypropylene Mesh by Increasing the Vascular Response.

This study reports that a methacrylic acid (MAA)-based copolymer coating generates constructive remodeling of polypropylene (PP) surgical mesh in a subcutaneous model. This coating is non-bioresorbable and follows the architecture of the mesh without impeding connective tissue integration. Following implantation, the tissue response is biased toward vascularization instead of fibrosis. The vessel density around the MAA mesh is double that of the uncoated mesh two weeks after implantation. This initial vasculature regresses after two weeks while mature vessels remain, suggesting an enhanced healing response. Concurrently, the MAA coating alters the foreign body response to the mesh. Fewer infiltrating cells, macrophages, and foreign body giant cells are found at the tissue-material interface three weeks after implantation. The coating also dampens inflammation, with lower expression levels of pro-inflammatory and fibrogenic signals (e.g., Tgf-β1, Tnf-α, and Il1-β) and similar expression levels of anti-inflammatory cytokines (e.g., Il10 and Il6) compared to the uncoated mesh. Contrary to other coatings that aim to mitigate the foreign body response to PP mesh, a MAA coating does not require the addition of any biological agents to have an effect, making the coated mesh an attractive candidate for soft tissue repair.

Designing new synthetic materials for use in the pelvic floor: what is the problem with the existing polypropylene materials?

This review identifies the clinical complications associated with the design of the current polyproplylene mesh materials used for the treatment of stress urinary incontinence and pelvic organ prolapse. Following on from this, new alternative materials under development for pelvic floor repair are reviewed. It is well accepted that the textile properties of the current polypropylene surgical meshes are not suitable for the pelvic floor environment. This together with the chemical nature of the current mesh leads to complications whenever implanted in the pelvic floor of women. New alternative materials for the repair of the pelvic floor have been developed with properties designed to be more appropriate for the biomechanical requirements and implantation requirements for the pelvic floor to reduce these clinical complications. To support this, these newer materials are being rigorously tested using more appropriate in-vitro regimes and animal models. This chapter summarizes developments in the design of new materials for pelvic floor repair. These are being subjected to preclinical testing to exclude materials, which might fail to work in this dynamic environment by either showing a poor mechanical match to the requirements of the tissue or by provoking sustained inflammation. The hope is that new materials will prove effective without causing the high incidence of unacceptable side-effects currently seen with polypropylene mesh implants.

An Unusual Delayed Complication of Urogynecologic Surgical Mesh Placement: Perirectal Abscess 10 Years After Initial Placement Treated by Endoscopic Removal and Transrectal Drain Placement: ACG Case Reports Journal Award: Presidential Poster Award

INTRODUCTION: More than 500,000 surgical procedures are done annually for management of symptomatic pelvic organ prolapse (POP) and stress urinary incontinence (SUI). Surgical mesh has been used in these surgeries for more than 20 years. However, an increasing number of reports of adverse effects have been described, particularly with transvaginal route of mesh insertion, which has led to issuance of FDA guidelines regarding the use of mesh in urogynecological procedures. Here we describe an uncommon complication of perirectal fistula and abscess associated with surgical mesh that was successfully managed with endoscopic therapy. CASE DETAILS: A 63-year old diabetic woman with urinary incontinence underwent robotic-assisted laparoscopic sacrocolpopexy (Burch procedure) along with polypropylene mesh placement in 2008. She did well until rectal bleeding 7 years later. Sigmoidoscopy showed protrusion of the mesh from the anterior wall of the rectum. During anoscopy under anesthesia, a 2cm length of mesh was cut out. She did well for 18 months before experiencing worsening low back and groin pain. CT scan revealed a 3 x 3 x 8cm fluid collection anterior to the rectum. Percutaneous drainage was attempted but a suitable window could not be found for drain placement. Long term antibiotics were given for several months, but she was readmitted for fevers. CT showed that the abscess now contained air. The patient was then referred for EUS-guided abscess drainage. Flexible endoscopy revealed purulent drainage through a pinpoint low rectal fistula. A through the scope balloon dilator was used to enlarge the fistula to 12 mm. After entry into the cavity a large piece of coiled surgical mesh was seen. The proximal margin was released using an endoscopic scissors, and a 9cm length of mesh removed. Two 7Fr x 5 cm double pigtail stents were placed in the cavity. CT 3 weeks later showed near complete resolution of the abscess and spontaneous extrusion of the stents. DISCUSSION: The use of surgical plastic mesh is common for management of POP and SUI, although increasing reports of adverse effects are being seen. The occurrence of a perirectal abscess is uncommon. This is the first reported case of endoscopic management of an abscess and removal of retained mesh. With increasing use of flexible endoscopic transrectal abscess drainage (usually under EUS guidance), this approach should be considered earlier in the management of perirectal abscesses.2164_A Figure 1. Coronal CT shows a large perirectal abscess.2164_B Figure 2. A through-the-scope dilation balloon is introduced through the fistula; purulent drainage is seen.2164_C Figure 3. After entry into the abscess cavity, a coiled piece of polypropylene surgical mesh is encountered.