Experimental study on the use of a chlorhexidine-loaded carboxymethylcellulose gel as antibacterial coating for hernia repair meshes

21 p.Purpose: Biomaterials with an antimicrobial coating could avoid mesh-associated infection following hernia repair. This study assesses the use of a chlorhexidine-loaded carboxymethylcellulose gel in a model of Staphylococcus aureus mesh infection. Methods: A 1% carboxymethylcellulose gel containing 0.05% chlorhexidine was prepared and tested in vitro and in vivo. The in vitro tests were antibacterial activity (S. aureus; agar diffusion test) and gel cytotoxicity compared to aqueous 0.05% chlorhexidine (fibroblasts; alamarBlue). For the in vivo study, partial abdominal wall defects (5 × 2 cm) were created in New Zealand white rabbits (n = 15) and inoculated with 0.25 mL of S. aureus ( 106 CFU/mL). Defects were repaired with a lightweight polypropylene mesh (Optilene) without coating (n = 3) or coated with a carboxymethylcellulose gel (n = 6) or chlorhexidine-loaded carboxymethylcellulose gel (n = 6). Fourteen days after surgery, bacterial adhesion to the implant (sonication, immunohistochemistry), host tissue incorporation (light microscopy) and macrophage reaction (immunohistochemistry) were examined. Results: Carboxymethylcellulose significantly reduced the toxicity of chlorhexidine (p < 0.001) without limiting its antibacterial activity. While control and gel-coated implants were intensely contaminated, the chlorhexidine-gel-coated meses showed a bacteria-free surface, and only one specimen showed infection signs. The macrophage reaction in this last group was reduced compared to the control (p < 0.05) and gel groups. Conclusions: When incorporated in the carboxymethylcellulose gel, chlorhexidine showed reduced toxicity yet maintained its bactericidal effect at the surgery site. Our findings suggest that this antibacterial gel-coated polypropylene meshes for hernia repair prevent bacterial adhesion to the mesh surface and have no detrimental effects on wound repair.Ministerio de Ciencia, Innovación y Universidade

Preclinical bioassay of a novel antibacterial mesh for the repair of abdominal hernia defects

25 p.Background: In hernia surgery, soaking of meshes in antibiotics before implantation is a prophylactic strategy for minimizing the risk of infection while providing minimal, local, drug doses. This study describes the development and application of an antibacterial mesh coating comprising a carboxymethylcellulose gel loaded with rifampicin in a preclinical model of Staphylococcus aureus and S. epidermidis infection in rabbits. Methods: Antibacterial activity and cytocompatibility (with fibroblasts) of unloaded carboxymethylcellulose gel and 0.13 mg/mL rifampicin-carboxymethylcellulose gel were assessed in vitro. Then, partial abdominal wall defects (5 x 2 cm) were created in New Zealand white rabbits (n = 34), the wound inoculated with 0.25 mL of 106 CFU Staphylococcus aureus/ S. epidermidis (n = 17 each), and the defect then repaired with a lightweight, monofilament, large pore polypropylene mesh either uncoated (n = 3) or coated with carboxymethylcellulose gel (n = 7) or rifampicin-carboxymethylcellulose gel (n = 7). By postoperative day 14, coating performance was evaluated by determining bacterial adhesion (via sonication), host tissue incorporation (via histology), macrophage response via immunostaining), and bloodstream drug diffusion (via high-performance liquid chromatography). Results: In vitro, rifampicin-carboxymethylcellulose gel demonstrated great activity against Staphylococcus aureus/S. epidermidis, while being innocuous for fibroblasts. In vivo, rifampicincarboxymethylcellulose gel-coated implants displayed full bacterial clearance and optimal tissue integration, irrespective of the strain of Staphylococcus. In contrast, uncoated and carboxymethylcellulose gel-coated implants exhibited macro/microscopic signs of infection and impaired tissue integration. Macrophage responses were less in rifampicin-carboxymethylcellulose gel implants than in uncoated mesh (Staphylococcus aureus/S. epidermidis; P < .01) and carboxymethylcellulose gel (S. epidermidis; P < .05) implants. Bloodstream levels of rifampicin were undetectable. Conclusion: Soaking meshes in rifampicin-carboxymethylcellulose gel inhibited effectively the bacterial adhesion to the mesh without compromising the tissue repair. This antibiotic gel constitutes an easy-touse and effective prophylactic strategy that potentially reduce the prevalence of postoperative mesh infectionMinisterio de Ciencia, Innovación y Universidade

Mesh fixation using a cyanoacrylate applied as a spray improves abdominal wall tissue repair

19 p.Background: Tissue adhesives are a feasible option to fix a hernia repair mesh, avoiding tissue trauma of suture fixation. Classically, they are applied in the form of a drop, although novel applications such as spray are emerging. This study compares the use of a new experimental cyanoacrylate (n-butyl) in the form of a spray or drops. Materials and methods: Three study groups of New Zealand White rabbits were established (n ? 6 each) according to the method used to fix a 5 3 cm polypropylene mesh in a partial abdominal wall defect model: control group (polypropylene stitches), adhesive drops group, and adhesive spray group. Morphological, immunohistochemical, and biomechanical strength studies were performed at 14 d postimplant. Collagen 1/3 gene ratio was determined by quantitative reverse transcription polymerase chain reaction. Results: In the drops group, the adhesive obstructed the mesh pores and prevented tissue infiltration at the points of application. When the adhesive was applied as a spray, although more numerous, adhesive deposits were smaller and allowed for better host tissue infiltration into the mesh. The inflammatory response was similar in the adhesive groups and more intense than in the control group. Collagen 1/3 mRNA ratio was significantly higher in the spray than the control group. The mechanical resistance of the meshes was similar in all three groups. * Corresponding author. Department of Surgery, Medical and Social Sciences. Faculty of Medicine and Health Sciences, University of Alcala, Ctra. Madrid-Barcelona, Km 33,600, Alcala de Henares, 28871 Madrid, Spain. Tel.: þ34 91 8854540; fax: þ34 91 8854885. E-mail address: [email protected] (J.M. Bellon). 1 These authors contributed equally to this work. 0022-4804/$ e see front matter ª 2019 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jss.2019.08.020 Conclusions: The application of the cyanoacrylate adhesive in the form of spray to fix polypropylene meshes in an animal model had a similar inflammatory response compared with droplet application. Neither application impacted the mechanical strength of the repaired area. An increased in collagen 1/3 ratio was found with cyanoacrylate spray compared with suture, and future studies should focus on this pathway.Ministerio de Economía y Competitivida

Behaviour at the peritoneal interface of next generation prosthetic materials for hernia repair

22 p.Background When using a prosthetic material in hernia repair, the behaviour of the mesh at the peritoneal interface is especially important for implant success. Biomaterials developed for their intraperitoneal placement are known as composites and are made up of two different-structure materials, one is responsible for good integration within host tissue and the other is responsible to make contact with the viscera. This study examines the behaviour at the peritoneal level of two composites, the fully degradable Phasix-ST® and the partially degradable Symbotex®. A polypropylene mesh (Optilene®) served as control. Methods Sequential laparoscopy from 3 to 90 days, in a preclinical model in the New Zealand white rabbit, allowed monitoring adhesion formation. Morphological studies were performed to analyse the neoperitoneum formed in the repair process. Total macrophages were identified by immunohistochemical labelling. To identify the different macrophage phenotypes, complementary DNAs were amplified by qRT-PCR using specific primers for M1 (TNF-?/CXCL9) and M2 (MRC1/IL-10) macrophages. Results The percentage of firm and integrated adhesions remained very high in the control group over time. Both composites showed a significant decrease in adhesions at all study times and in qualitative terms were mainly loose. Significant differences were also observed from 7 days onwards between the two composites, increasing the values in Phasix over time. Neoperitoneum thickness for Phasix was significantly greater than those of the other meshes, showing mature and organized neoformed connective tissue. Immunohistochemically, a significantly higher percentage of macrophages was observed in Symbotex. mRNA expression levels for the M2 repair-type macrophages were highest for Phasix but significant differences only emerged for IL-10. Conclusions Fewer adhesions formed to the Symbotex than Phasix implants. Ninety days after implant, total macrophage counts were significantly higher for Symbotex, yet Phasix showed the greater expression of M2 markers related to the tissue repair process.Ministerio de Economía y Competitivida

Thermo-responsive antimicrobial hydrogel for the in-situ coating of mesh materials for hernia repair

The prophylactic coating of prosthetic mesh materials for hernia repair with antimicrobial compounds is commonly performed before implantation of the mesh in the abdominal wall. We propose a novel alternative, which is a rifampicin-loaded thermo-responsive hydrogel formulation, to be applied on the mesh after its implantation. This formulation becomes a gel in-situ once reached body temperature, allowing an optimal coating of the mesh along with the surrounding tissues. In vitro, the hydrogel cytotoxicity was assessed using rabbit fibroblasts and antimicrobial e_cacy was determined against Staphylococcus aureus. An in vivo rabbit model of hernia repair was performed; implanted polypropylene meshes (5 x 2 cm) were challenged with S. aureus (106 CFU), for two study groups?unloaded (n = 4) and 0.1 mg/cm2 rifampicin-loaded hydrogel (n = 8). In vitro, antibacterial activity of the hydrogel lasted for 5 days, without sign of cytotoxicity. Fourteen days after implantation, meshes coated with drug-free hydrogel developed a strong infection and resulted in poor tissue integration. Coating meshes with the rifampicin-loaded hydrogel fully prevented implant infection and permitted an optimal tissue integration. Due to its great performance, this, degradable, thermo-responsive antimicrobial hydrogel could potentially be a strong prophylactic armamentarium to be combined with prosthesis in the surgical field.info:eu-repo/grantAgreement/European Hernia Society/2019 info:eu-repo/grantAgreement/MICINN //SAF2017-89481-Pinfo:eu-repo/grantAgreement/MICINN //SAF2017-89481-

Long term comparative evaluation of two types of absorbable meshes in partial abdominal wall defects: an experimental study in rabbits

26 p.Purpose: Synthetic prosthetic materials that are fully absorbable seek to reduce the host foreign body reaction and promote host tissue regeneration. This preclinical trial was designed to analyse, in the long term, the behaviour of two prosthetic meshes, one synthetic and one composed of porcine collagen, in abdominal wall reconstruction. Methods: Partial defects were created in the abdominal walls of New Zealand rabbits and repaired using a synthetic absorbable mesh (Phasix?) or a non-crosslinked collagen bioprosthesis (Protexa?). After 3, 6, 12 and 18 months, specimens were recovered for light microscopy and collagen expression analysis to examine new host tissue incorporation, macrophage response and biomechanical strength. Results: Both materials showed good host tissue incorporation in line with their spatial structure. At 18 months postimplant, Protexa? was highly reabsorbed while the biodegradation of Phasix? was still incomplete. Collagenization of both materials was good. Macrophage counts steadily decreased over time in response to Phasix?, yet persisted in the collagen meshes. At 18 months, zones of loose tissue were observed at the implant site in the absence of herniation in both implant types. The stress?stretch behaviour of Phasix? implants decreased over time, being more pronounced during the period of 12?18 months. Nevertheless, the abdominal wall repaired with Protexa? became stiffer over time. Conclusion: Eighteen months after the implant both materials showed good compatibility but the biodegradation of Phasix? and Protexa? was incomplete. No signs of hernia were observed at 18 months with the stress?stretch relations being similar for both implants, regardless of the more compliant abdominal wall repaired with Protexa? at short term.Ministerio de Economía y Competitivida

Antibacterial polypropylene mesh fixation with a cyanoacrylate adhesive improves its response to infection

22 p.Background: Antibacterial meshes for hernia repair seek to avoid infection in the patient. As thesebiomaterials are especially prone to bacteria settling at their sutured borders, this study examines whether the use of a cyanoacrylate tissue adhesive could improve mesh behavior at the fixation zones. Methods: First, antibacterial polypropylene meshes were prepared by soaking in 0.05% chlorhexidine, and the response of n-hexyl cyanoacrylate to contamination with Staphylococcus aureus ATCC25923 was assessed in vitro. Then, in a preclinical model, partial defects (5 x 3 cm) were created in the abdominal wall of 18 New Zealand White rabbits and repaired with mesh to establish the following 3 study groups: (1) mesh without chlorhexidine fixed with cyanoacrylate, (2) antibacterial mesh fixed with sutures, and (3) antibacterial mesh fixed with cyanoacrylate (n = 6 each). The implants were inoculated with 106 CFU/ mL of S aureus. At 14 days after surgery, bacterial adhesion to the implant and its integration within host tissue were determined through microbiological, histological and immunohistochemical procedures. Results: As observed in vitro, the cyanoacrylate gave rise to a 1.5-cm bacteria-free margin around the prosthetic mesh. In vivo, the tissue adhesive prevented bacterial adhesion to the fixation zones, reducing infection of chlorhexidine-free meshes and optimizing the efficacy of the antibacterial meshes compared with those fixed with sutures. Conclusion: These findings indicated that cyanoacrylate fixation does not affect mesh integration into the host tissue. Likewise, the antibacterial behavior and tissue response of a chlorhexidine-treated polypropylene mesh is improved when cyanoacrylate is used for its fixation.Ministerio de Ciencia, Innovación y Universidade

Antibacterial biopolymer gel coating on meshes used for abdominal hernia repair promotes effective wound repair in the presence of infection

14 p.Prosthetic mesh infection is a devastating complication of abdominal hernia repair which impairs natural healing in the implant area, leading to increased rates of patient morbidity, mortality, and prolonged hospitalization. This preclinical study was designed to assess the effects on abdominal wall tissue repair of coating meshes with a chlorhexidine or rifampicin-carboxymethylcellulose biopolymer gel in a Staphylococcus aureus (S. aureus) infection model. Partial abdominal wall defects were created in New Zealand white rabbits (n = 20). Four study groups were established according to whether the meshes were coated or not with each of the antibacterial gels. Three groups were inoculated with S. aureus and finally repaired with lightweight polypropylene mesh. Fourteen days after surgery, implanted meshes were recovered for analysis of the gene and protein expression of collagens, macrophage phenotypes, and mRNA expression of vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs). Compared to uncoated meshes, those coated with either biopolymer gel showed higher collagen 1/3 messenger RNA and collagen I protein expression, relatively increased VEGF mRNA expression, a significantly reduced macrophage response, and lower relative amounts of MMPs mRNAs. Our findings suggest that following mesh implant these coatings may help improving abdominal wall tissue repair in the presence of infectionMinisterio de Ciencia e Innovació

Self-adhesive hydrogel meshes reduce tissue incorporation and mechanical behavior versus microgrips self-fixation: a preclinical study.

Purpose: Atraumatic mesh fixation for abdominal hernia repair has been developed to avoid the disadvantages of classical fixation with sutures, which is considered a cause of chronic pain and discomfort. This study was designed to analyze, in the short and medium term, the biological and mechanical behavior of two self-fixing meshes compared to that of a polypropylene (PP) mesh fixed with a cyanoacrylate (CA) tissue adhesive. Methods: Partial abdominal wall defects (6 × 4 cm) were created in New Zealand rabbits (n = 36) and repaired using a selfadhesive hydrogel mesh (Adhesix?), a self-gripping mesh (ProGrip?) or a PP mesh fixed with CA (Surgipro? CA). After 14 and 90 days, the host tissue incorporation, macrophage response and biomechanical strength were examined. Results: At 14 and 90 days, the ProGrip and Surgipro CA meshes showed good host tissue incorporation; however, the Adhesix implants presented poor integration, seroma formation and a higher degree of shrinkage. The Adhesix hydrogel was completely reabsorbed at 14 days, whereas ProGrip microhooks were observed at all study times. The macrophage response was higher in the ProGrip and Surgipro CA groups at 14 and 90 days, respectively, and decreased over time. At 90 days, the ProGrip implants showed the highest tensile strength values and the Adhesix implants showed the highest failure stretch. Conclusion: Meshes with mechanical microgrip self-fixation (ProGrip) show better biological and mechanical behavior than those with adhesive hydrogel (Adhesix) in a preclinical model of abdominal hernia repair in rabbits.Agencia Estatal de Investigació

Evaluation of synthetic reticular hybrid meshes designed for intraperitoneal abdominal wall repair: Preclinical and in vitro behavior.

INTRODUCTION:Reticular hybrid meshes represent an alternative material for intraperitoneal repair of abdominal hernias. These consist of a reticular mesh coated or interwoven/knitted with inert materials. This study assesses the performance of two reticular polypropylene-containing hybrid meshes, TiMESH (coated with titanium) and DynaMesh (interwoven with polyvinylidene fluoride), in vitro, as well as their efficiency in adhesion prevention and tissue incorporation in an intraperitoneal model. METHODS:The mesothelialization capacity of TiMESH and DynaMesh was evaluated in vitro and compared to that of Surgipro (reticular bare polypropylene) and Preclude (laminar expanded polytetrafluoroethylene). Mesh fragments were placed on the intact parietal peritoneum of New Zealand white rabbits (n = 24), and laparoscopy performed 7 days post-surgery. Fourteen days post-implantation, adhesions were evaluated and host tissue incorporation, macrophage response, collagen expression (immunohistochemistry/RT-PCR) and neoperitoneum formation assessed. Adhesions and omental tissue were also examined. RESULTS:Mesh pores in reticular meshes were devoid of cells in the in vitro study. TiMESH, DynaMesh and Surgipro showed similar adhesion rates at 7/14 days and optimal tissue integration, with significant differences in comparison to Preclude. The greatest presence of macrophages was observed for TiMESH and was significant versus that for Preclude. Hybrid meshes revealed significantly higher collagen 1 mRNA expression in implants, with no differences in the levels of collagen 3. Omental samples from animals with a reticular mesh showed significantly greater collagen 1 mRNA levels. CONCLUSIONS:The reticular structure of a mesh limits the formation of a continuous mesothelial monolayer in vitro, regardless of its composition. The presence of titanium as a coating or polyvinylidene fluoride interwoven with polypropylene in a reticular structure did not prevent adhesions. The hybrid meshes showed proper integration and an increase in the mRNA Col 1 levels in the implant area compared to Surgipro or Preclude