Large pore size and controlled mesh elongation are relevant predictors for mesh integration quality and low shrinkage--Systematic analysis of key parameters of meshes in a novel minipig hernia model.

BACKGROUND: Prosthetic mesh implants in hernia repair are frequently used based on the fact that lower recurrence rates are detected. However, an undesirable side effect is persistent foreign body reaction that drives adhesions and shrinkage among other things in the course of time. Thereby a variety of meshes have been created in an attempt to alleviate these side effects, and particular relating to shrinkage, the ideal mesh has not been developed. Large pore size is one of the properties to get better ingrowth of the implants but could also be a risk factor to shrinkage behavior. The aim of this preclinical study was to determine optimal pore size based on mesh integration and shrinkage in a hernia minipig model. METHODS: Twenty female minipigs were each implanted at four abdominal retromuscular sites with meshes (designed and knitted specifically for this study) that had various weights and pore sizes, but similar weave. At 3 and 21 weeks post-operation, ten pigs each were euthanized. Mesh integration and shrinkage were evaluated through macroscopic observation, biomechanical testing and histopathological analysis. RESULTS: The large pore meshes (6.1-6.6 mm(2)) showed significantly better integration than small pore (0.9-1.1 mm(2)) counterparts, by biomechanical testing and histological assessment. This was independent of mesh weight. The lightweight small pore mesh exhibited significantly more shrinkage than any of the other meshes, while the three-dimensional heavyweight large pore mesh exhibited the least shrinkage. Mesh shrinkage and elongation at 50 Newton (N) as one parameter of the implant structural stability appeared to be strongly interrelated. CONCLUSION: Tissue ingrowth of meshes depends on increasing pore size. Macroporous mesh design >1.5 mm diameter appears to be optimal in terms of mesh integration. Lightweight meshes with a large pore size on one hand and a lack of structural stability on the other hand drives mesh shrinkage. High stretchability (Elongation >50 N) induces higher shrinkage and therefore elongation at 50 N appears to be a new parameter to estimate mesh shrinkage. Three-dimensional mesh constructions relate to the lowest shrinkage behavior caused by higher structure stability.

Multi-membrane hydrogels.

Polysaccharide-based hydrogels are useful for numerous applications, from food and cosmetic processing to drug delivery and tissue engineering. The formation of hydrogels from polyelectrolyte solutions is complex, involving a variety of molecular interactions. The physical gelation of polysaccharides can be achieved by balancing solvophobic and solvophilic interactions. Polymer chain reorganization can be obtained by solvent exchange, one of the processing routes forming a simple hydrogel assembly. Nevertheless, many studies on hydrogel formation are empirical with a limited understanding of the mechanisms involved, delaying the processing of more complex structures. Here we use a multi-step interrupted gelation process in controlled physico-chemical conditions to generate complex hydrogels with multi-membrane 'onion-like' architectures. Our approach greatly simplifies the processing of gels with complex shapes and a multi-membrane organization. In contrast with existing assemblies described in the literature, our method allows the formation of free 'inter-membrane' spaces well suited for cell or drug introduction. These architectures, potentially useful in biomedical applications, open interesting perspectives by taking advantage of tailor-made three-dimensional multi-membrane tubular or spherical structures.