Mesothelial morphology and organisation after peritoneal treatment with solid and liquid adhesion barriers--a scanning electron microscopical study.

Separation of traumatized tissue represents the only promising strategy in postoperative adhesion prevention, a relevant clinical problem after surgical intervention. In the present study scanning electron microscopy (SEM) and subsequent morphometry were used to analyse the tissue response to five commercial adhesion barriers. Standardised peritoneal lesions in Wistar rats were covered with solid and viscous barrier materials and semiquantitatively analysed 14 days postoperatively. Striking morphological differences in lesion surface organisation between the barrier groups became apparent with colonisation of the barrier by mesothelial cells to different degrees. Furthermore, the mesothelial cells showed either a normal or activated phenotype depending on the underlying biomaterial. These experiments demonstrate that the examination by SEM gives useful insights into the performance of barrier materials and the cellular processes of adhesion prevention, since mesothelial cells play an active role in the pathogenesis of adhesion formation.

Current strategies and future perspectives for intraperitoneal adhesion prevention.

INTRODUCTION: The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found. DISCUSSION: Mesothelial cells play a crucial physiological role in friction less gliding of the serosa and the maintenance of anantiadhesive surface. The formation of postoperative adhesions results from a cascade of events and is regulated by various cellular and humoral factors. Therefore, optimization or functionalization of barrier materials by developments interacting with this cascade on a structural or pharmacological level could give an innovative input for future strategies in peritoneal adhesion prevention. For this purpose, the proper understanding of the formal pathogenesis of adhesion formation is essential. Based on the physiology of the serosa and the pathophysiology of adhesion formation, the available barriers in current clinical practice as well as new innovations are discussed in the present review.

Effect of fibrous filter properties on the oil-in-water-emulsion separation and filtration performance.

Separation of secondary emulsions of dispersed droplet size less than 10 µm, by means of fibrous medium is a very complex but important process. The study investigates the influence of thin fibrous filter properties, i.e. surface energy, pore size and porosity on the separation performance of an isooctane in water emulsion (0.2%, mean drop size 2 µm). Experiments were carried out on five different filter media with a wide variation in their pore size (2-51 µm), surface energy (14-46 mN/m) and porosity (0.46-0.87) at similar process conditions. Filter media with different wettability are obtained by applying various hydrophobic and hydrophilic coatings. All the used coatings contain nanoparticles (25 nm) to impart nanoscale surface roughness at the single fiber surface. Besides emulsion properties and operating conditions, the phase separation mechanism and performance highly depends on pore size, surface energy and porosity of the filter media. More complete coalescence takes place at reduced pore size and at a surface preferentially wetted by the dispersed phase. Whereas when the pore size equals to the influent droplet size, then the surface wettability of filter is less effective and the separation mechanism is governed by inflow velocity. The emulsion inflow velocity and pressure drop are significantly affected by the filter media air permeability but do not depend on filter surface energy.

Bionics in textiles: flexible and translucent thermal insulations for solar thermal applications.

Solar thermal collectors used at present consist of rigid and heavy materials, which are the reasons for their immobility. Based on the solar function of polar bear fur and skin, new collector systems are in development, which are flexible and mobile. The developed transparent heat insulation material consists of a spacer textile based on translucent polymer fibres coated with transparent silicone rubber. For incident light of the visible spectrum the system is translucent, but impermeable for ultraviolet radiation. Owing to its structure it shows a reduced heat loss by convection. Heat loss by the emission of long-wave radiation can be prevented by a suitable low-emission coating. Suitable treatment of the silicone surface protects it against soiling. In combination with further insulation materials and flow systems, complete flexible solar collector systems are in development.

Biomimetics and technical textiles: solving engineering problems with the help of nature's wisdom.

The significance of inspiration from nature for technical textiles and for fibrous composite materials is demonstrated by examples of already existing technical solutions that either parallel biology or are indeed inspired by biological models. The two different basic types of biomimetic approaches are briefly presented and discussed for the "technical plant stem." The technical plant stem is a biomimetic product inspired by a variety of structural and functional properties found in different plants. The most important botanical templates are the stems of the giant reed (Arundo donax, Poaceae) and of the Dutch rush (Equisetum hyemale, Equisetaceae). After analysis of the structural and mechanical properties of these plants, the physical principles have been deduced and abstracted and finally transferred to technical applications. Modern computer-controlled fabrication methods for producing technical textiles and for structuring the embedding matrix of compound materials render unique possibilities for transferring the complex structures found in plants, which often are optimized on several hierarchical levels, into technical applications. This process is detailed for the technical plant stem, a biomimetic, lightweight, fibrous composite material based on technical textiles with optimized mechanical properties and a gradient structure.

Control of material stiffness during degradation for constructs made of absorbable polymer fibers.

Augmentation devices for cruciate ligament surgery should provide gradually decreasing mechanical properties with a half-time strength of at least 6 months to temporarily protect healing tendon grafts or sutured ligaments against high tensile loads during the postoperative healing period. The absorbable material of choice that shows such slow degradation kinetics is poly(L-lactide). However, previous studies have shown that poly(L-lactide) fulfills the requirement of a long half-time strength, while the corresponding stiffness decreases at a much slower rate. An augmentation stiffness that does not change much versus time cannot provide a gradual increase in graft load, which is important to stimulate the orientation of the collagenous tissue. Therefore a new augmentation device was designed, which should decrease both in strength and stiffness during degradation. The cord was braided out of two fibers made of poly(L-lactide) and poly(L-lactide-co-glycolide), which degrade at different rates. The cord prototype was degraded in vitro and the rupture force and stiffness was tested at eight different time points up to 60 weeks. The initial rupture force and stiffness was 522.7 +/- 2.8 N and 104.1 +/- 3.8 N/%, respectively. Both strength and stiffness decreased continuously with a half-time strength of 18 weeks and a half-time stiffness of 39 weeks. The gradually decreasing stiffness was achieved by the breakdown of the faster-degrading fiber component made of poly(L-lactide-co-glycolide). Thus the new augmentation device can provide a continuous increase of forces in a tendon graft or in a healing ligament.

Rat Schwann cells in bioresorbable nerve guides to promote and accelerate axonal regeneration.

A micro-structured, biodegradable, semipermeable hollow nerve guide implant was developed to bridge nerve lesions. Quantitative comparison of cell migration and axonal growth using time lapse video recording in vitro revealed that axons grow eight times faster than neuritotrophic Schwann cells migrate. To accelerate regeneration, purified Schwann cells are best injected into nerve guides before implantation. Nerve guides made from resorbable poly-lactide-co-glycolide support Schwann cell attachment, cell survival, and axonal outgrowth in vitro. The therapeutic concept aims at the development of an 'intelligent neuroprosthesis' that first mediates regeneration and then disappears.