Biomedical subjects
M F Jonkman
Publications and source records attributed to M F Jonkman.
A new porous polyetherurethane wound covering.
A polyetherurethane (PEU) wound covering with non-interconnected micropores up to approximately 5 microns has been prepared by means of a phase inversion process. This highly elastic, very thin (15-20 microns), pliable wound covering showed good, immediate adherence to wet wound surfaces and high water vapor permeability, but was impermeable to bacteria. In guinea pigs epidermal wound healing of partial-thickness wounds under PEU wound coverings was accelerated compared with uncovered controls and an occlusive wound covering, OpSite. Water in liquid form or wound exudate could not leak through the PEU covering, but its high water vapor permeability induced concentration of the wound exudate into a jellylike clot layer, which apparently accelerated reepithelialization. The main conclusion from a clinical study on 20 donor sites was that the use of the PEU covering reduced pain, besides prevention of fluid retention. No differences in epithelialization were seen in comparison to tulle gras-treated wounds.
Biodegradable lysine diisocyanate-based poly(glycolide-co-epsilon-caprolactone)-urethane network in artificial skin.
A biodegradable lysine diisocyanate-based poly(glycolide-co-epsilon-caprolactone)urethane network has been evaluated as a material for the construction of a macroporous bottom layer (dermal analogue) in a two-layer artificial skin. High rates of in vitro degradation were observed; degradation of the porous poly(glycolide-co-epsilon-caprolactone)urethane networks was faster in vivo than in vitro. Subcutaneous implantation in guinea pigs showed that the porous polyurethane networks allowed rapid cell ingrowth, degraded almost completely 4-8 wk after implantation and evoked no adverse tissue reaction.
Accelerated epithelization under a highly vapor-permeable wound dressing is associated with increased precipitation of fibrin(ogen) and fibronectin.
In a previous study we showed that the use of a newly developed, highly water vapor permeable, PEU wound dressing accelerates the epithelization of partial-thickness wounds more than an occlusive wound dressing (OpSite) in comparison with air exposure. The purpose of this study was to investigate the distribution of fibrin(ogen), fibronectin, and type IV collagen during the epithelization process under these three conditions. The breathable PEU film enabled coagulation of the wound exudate, preserving it into a semisolid gelatinous state. This coagulum layer contained an abundant amount of fibrin(ogen) and fibronectin. In wounds occluded with OpSite film, depositions of fibrin(ogen) and fibronectin were less extensive. Migrating keratinocytes contained intracellular depositions of fibrin(ogen), suggesting that these cells phagocytize components of the provisional fibrin matrix during wound healing. It was concluded that accelerated epithelization underneath the highly water vapor permeable polyetherurethane film dressing is associated with the presence of a gelatinous coagulum containing fibrin(ogen) and fibronectin. We speculate that the enhanced healing rate might be caused by an increased concentration of growth-promoting factors present in the residual exudate underneath the PEU dressing.
A new high water vapor permeable polyetherurethane film dressing.
This study summarizes the Ph.D.-research project concerning the development of a new high water vapor permeable wound dressing. The dressing is composed of a 15 microns thin polyetherurethane (PEU) film, which has many non-interconnected cavities to enable a high water vapor permeability up to 20.1 g.m-2.h-1.kPa-1. Since only water vapor permeates through the PEU dressing, the wound exudate underneath is condensed into a gelatinous coagulum. Epithelialization was accelerated by 25% under the clot-permissive PEU film compared with the fluid retaining OpSite film. In clinical situations on donor sites and grafted full-thickness burn wounds, the PEU film indeed prevented fluid accumulation and induced the formation of a "red" coagulum underneath. It furthermore reduces pain significantly compared to conventional paraffin gauze dressing. In conclusion, the optimum environment for epithelialization is a wound, in which the exudate is permitted to gelatinize between moist and dry.
Poly(ether urethane) wound covering with high water vapour permeability compared with conventional tulle gras on split-skin donor sites.
The experimental poly(ether urethane) (PEU) wound covering with a high water vapour permeance was compared with tulle gras treatment on adjacent areas of the same 20 split-skin donor sites. All patients experienced little or no pain from the PEU-covered areas, while 70 per cent of the patients complained of more pain from the tulle gras-covered areas. The PEU covering did not absorb the wound exudate underneath, neither did it retain wound fluid, but turned the wound exudate into a jelly-like clot layer by allowing a high evaporative water loss from the wound. Tulle gras treatment also prevented wound desiccation, but the exudate was absorbed into the overlaying cotton pads, where it became dry at the outer surface. Microscopy revealed that re-epithelialization occurred at a similar rate under the PEU covering as under tulle gras. In conclusion, the high water vapour permeable PEU wound covering prevents fluid retention, induces clotting of the wound exudate and reduces pain in split-skin donor sites. Tulle gras dressed with gauzes and crêpe bandage prevents wound desiccation, but causes more pain.
Water vapour permeance: a meaningful measure for water vapour permeability of wound coverings.
For comparison of the evaporative water loss through wound coverings, it is necessary to have an accurate and reliable method of measurement. The water vapour permeance (WVP), obtained with the Evaporimeter, meets these requirements, under both in vitro and in vivo circumstances.
Evaporative water loss and epidermis regeneration in partial-thickness wounds dressed with a fluid-retaining versus a clot-inducing wound covering in guinea pigs.
The effects of a new high vapour permeable poly-(ether urethane) (PEU) wound covering on evaporative water loss (EWL) and epidermis regeneration in partial-thickness wounds in guinea pigs were investigated and compared with an occlusive wound covering (OpSite) and air-exposed controls. It was also assessed whether the EWL reflected the phases of epidermis regeneration. In PEU-covered wounds, the initially raised EWL of 100 gm-2h-1 decreased in four days to 30 gm-2h-1, the same level as in occluded wounds. In control wounds this level was only reached after seven days, reflecting slower epidermis regeneration. The results showed that triphasic EWL behaviour corresponded to the sequence of wound healing. There was (1) a constant raised EWL until epidermal resurfacing is complete, (2) a fast EWL decrease during parakeratotic keratinization, and (3) a gradual normalization of the EWL during maturation of the stratum corneum. In wounds covered with OpSite this phasic EWL behaviour did not occur, owing to forced reduction because of the relatively impermeable covering. It was concluded that the PEU wound covering has an ideal water vapour permeance of 22.2 gm-2h-1 kPa-1, as can be seen in the accelerated epidermis regeneration and fast EWL reduction in partial thickness wounds in guinea pigs.
Sudan black B as a histological stain for polymeric biomaterials embedded in glycol methacrylate.
Sudan black B, usually a stain for all kinds of lipid, turned out to be an excellent histological stain for polymeric biomaterials embedded in glycol methacrylate. Staining the surrounding connective tissue with toluidine blue-basic fuchsin makes details of the polymer-tissue interface clearly visible. Sudan black B might be used to visualize the biodegradation process of polymeric biomaterials.
New method to assess the water vapour permeance of wound coverings.
A new method for assessing the permeability to water vapour of wound coverings is presented, using the evaporimeter developed by Nilsson. This new method combines the water vapour transmission rate (WVTR) and the vapour pressure difference across a wound covering in one absolute measure: the water vapour permeance (WVP). The WVP of a wound covering is the steady flow (g) of water vapour per unit (m2) area of surface in unit (h) time induced by unit (kPa) vapour pressure difference, g.m-2.h-1.kPa-1. Since the WVP of a wound covering is a more accurate measure for the permeability than the WVTR is, it facilitates the prediction of the water exchange of a wound covering in clinical situations.
A clot-inducing wound covering with high vapor permeability: enhancing effects on epidermal wound healing in partial-thickness wounds in guinea pigs.
Although the use of an occlusive wound covering accelerates the reepithelialization of a partial-thickness wound, it has the disadvantage of leading to wound exudate accumulation. The effect of an experimental polyetherurethane (PEU) wound covering with a high vapor permeability was compared with an occlusive wound covering (OpSite covering) and air exposure with respect to the rate of reepithelialization, eventual epidermal thickness, and scab thickness in 122 partial-thickness wounds in guinea pigs. The percentage of reepithelialization on day 2 was 85% in wounds covered with the permeable PEU membrane, whereas it was 66% and 35%, respectively, in wounds covered with the occlusive covering or exposed to air. The epidermal thickness did not differ among the three types of treatment. The scab thickness, however, was maximal in the uncovered air-exposed wounds. We conclude that epidermal wound healing is accelerated when the PEU wound covering is used. This wound-healing-promotion effect is apparently due to the high water vapor permeability of PEU, which induces clotting of the wound exudate, and subsequent jellifying of the clot layer.
A rapid connective tissue stain for glycol methacrylate embedded tissue.
No reliable connective tissue stains for GMA sections were available until recently. However, the use of toluidine blue in combination with basic fuchsin appeared to be a rapid and reliable connective tissue stain for glycol methacrylate (GMA) embedded tissue.
Segmental uterine horn replacement in the rat using a biodegradable microporous synthetic tube.
To investigate the possible use of a biodegradable microporous synthetic tube for fallopian tube replacement, polyetherurethane/poly-L-lactide (PU/PLLA) grafts in the uterine horn of the rat were studied and their patency and healing characteristics compared with those of nonbiodegradable polytetrafluoroethylene (PTFE; Teflon) grafts as well as with those of reanastomosed uterine horns. Regarding the healing characteristics, the PU/PLLA grafts were superior to the PTFE graft, as was indicated by the regeneration of endometrium and the extensive perigraft tissue ingrowth. However, the graft/uterine anastomoses of the PU/PLLA and PTFE grafts became obstructed by a plug of mucosal folds, all reanastomosed, uterine horns in the control experiments remaining open. In conclusion, although biodegradable microporous PU/PLLA uterine horn grafts have better healing characteristics than PTFE grafts, they easily obstruct at the graft/uterine junction. Mucosal suturing and/or the use of splints may contribute to the feasibility of biodegradable microporous artificial fallopian tubes in tubal surgery.