Evaluation of the tissue reaction to a percutaneous access device using titanium fibre mesh anchorage in goats

The tissue reaction to a percutaneous access device, applicable as a carrier for an implantable glucose sensor, was evaluated in goats. Titanium fibre mesh structures were used for anchorage of the device in superficial as well as deeper soft-tissue locations. The percutaneous part was subcutaneously anchored with a fibre mesh sheet. The distal part was placed intraperitoneally and anchored in deeper soft-tissue layers using a fibre mesh cuff. All implants showed good healing with the surrounding tissue. Histological evaluation showed that the subcutaneous fibre mesh sheets and peritoneal fibre mesh cuffs were filled with immature connective tissue, generally free of inflammation. Problems concerning disconnection of the silicone catheter from the titanium holding element and filling of part of the peritoneal fibre mesh cuff with silicone glue have to be overcome by more appropriate preclinical testing and improved implant design. Our results demonstrate that titanium fibre mesh structures can be used effectively for soft-tissue anchorage of percutaneous access devices. A sufficient ingrowth of connective tissue was obtained in superficial as well as in deeper soft-tissue layers. The access device could have application as a carrier for an implantable glucose sensor for glucose monitoring in different tissue compartments.     

钛网添加对镁/铝复合板微观组织和力学性能影响研究

目的 有效抑制镁/铝复合板界面处金属间化合物的形成。以钛网为中间金属夹层,研究它对镁/铝复合板微观组织和力学性能的影响。方法 利用复合轧制技术制备以钛网为中间金属夹层的镁/铝-钛复合板,采用扫描电子显微镜(SEM)、电子背散射衍射仪(EBSD)、万能试验机等对复合板退火前后的微观组织和力学性能进行表征和分析,系统研究中间层钛网对轧制态和退火态复合板微观组织、织构、拉伸性能、界面结合强度的影响规律。结果 中间层钛网均匀分布在镁/铝-钛复合板界面处,钛网的添加能有效抑制复合板退火过程中镁-铝金属间化合物的连续生长,减少金属间化合物的数量。与镁/铝复合板相比,钛网的添加对轧制态和退火态复合板中镁层和铝层的平均晶粒尺寸和织构类型的影响较小。与镁/铝复合板相比,钛网的添加降低了轧制态复合板的界面剪切强度和延伸率,但极大提升了退火态复合板的界面剪切强度、拉伸强度和延伸率。结论 中间层钛网的添加可有效减少复合板界面处金属间化合物的数量,提升退火态复合板的综合力学性能。     

A percutaneous device to study glucose kinetics in subcutaneous tissue fluid

In the current study subcutaneous glucose kinetics were investigated in tissue fluid collected with a percutaneous device (PD). PDs containing a subcutaneous tissue chamber were implanted subcutaneously in New Zealand white rabbits. Sintered titanium fiber mesh sheets were used for subcutaneous anchorage of the PD. The bottom of the subcutaneous tissue chamber was either covered with a titanium fiber mesh sheet, a cellulose acetate membrane, or left uncovered. Subcutaneous glucose kinetics were determined after injection of octreotide and glucagon. The tissue reaction to the implants was evaluated histologically. No dynamic relationship was observed between glycaemia and subcutaneous tissue fluid glucose for all membrane covered devices. Histological evaluation showed that the presence of a seroma cavity in combination with obstruction of the membrane prevented adjustment of the subcutaneous glucose concentration in response to changes in glycaemia. In the uncovered devices, on the other hand, changes in glycaemia were reflected in subcutaneous tissue fluid. Our results prove that it is possible to measure changes in the glucose concentration in subcutaneous tissue fluid collected with a percutaneous device. Therefore, we conclude that a percutaneous device has an application as model to study the in vivo performance of implantable glucose sensors. The use of porous membranes in such devices has to be avoided.     

Effect of carbon fibres on the static and fatigue mechanical properties of fibre metal laminates

It is crucial to understand the characteristic fatigue crack initiation and its growth mechanisms, as well as the relationship between the mechanical properties and the fatigue damage evolution in fibre metal laminates (FMLs). Two types of FML were studied in this work: a polyacrylonitrile‐based carbon fibre epoxy matrix composite sandwiched by Ti‐6Al‐4V (Ti‐alloy) sheets (IMS60‐Ti) and a pitch‐based carbon fibre epoxy matrix composite sandwiched by Ti‐alloy sheets (K13D‐Ti). The static and fatigue mechanical properties of IMS60‐Ti and K13D‐Ti were investigated. The increased failure strain of the FML was greater than that of carbon fibre‐reinforced polymer (CFRP) matrix composites. The fatigue life of IMS60‐Ti was much longer than that of K13D‐Ti. The fatigue damage process in IMS60‐Ti was related to the fatigue creep behaviour of the Ti‐alloy face sheet and mode II cracking at the CFRP/Ti‐alloy interface, and the damage in K13D‐Ti was related to the K13D CFRP laminate.     

Biomechanical evaluation of cell-loaded and cell-free hydroxyapatite implants for the reconstruction of segmental bone defects

Porous hydroxyapatite (HA) scaffoldings are currently used in tissue engineering for bone reconstruction. When this osteoconductive biomaterial is combined with osteoprogenitor cells, it acquires osteoinductive features which accelerate and improve bone formation in vivo. The aim of our study was to assess the mechanical properties of HA–bone complexes undergoing indentation tests, and relate stiffness to composition and structure as examined by micro X-ray. To this purpose, 35-mm tibia diaphyseal resections were performed in sheep. Gaps were filled using porous HA cylinders. Implants were loaded with autologous bone marrow stromal cells (BMSC); cell-free cylinders were used as control. After 8 weeks, bone tissue was found within the internal macropores of cell-loaded HA carriers, and in control implants, bone formation was mostly limited to the outer surface. As assessed by indentation testing the stiffness values of bone–HA composites were halfway between those of HA scaffoldings and tibia bone. Cell-loaded implants were stiffer than cell-free ones. In a cell-loaded implant we also analyzed the variation of stiffness along the main axis of the tibia.     

Fabrication of multilayered titanium aluminide sheets by self-propagating high-temperature synthesis reaction using hot rolling and heat treatment

This study is concerned with the fabrication of multilayered and bulk Ti aluminide sheets by self-propagating high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. A multilayered Ti/Al sheet was prepared by stacking thin Ti and Al sheets alternatively. When this sheet was hot-rolled and heat-treated at 1000°C, a multilayered sheet composed of Ti₃Al and TiAl was made through the process of formation and growth of intermetallic phases at Ti/Al interfaces and porosity reduction. A bulk Ti aluminide sheet having a lamellar structure of TiAl and Ti₃Al was also fabricated successfully by heat treatment at 1400°C.     

Tissue response to hafnium

The aim of the present experimental study was to evaluate the tissue response to hafnium (Hf) a reactive metal closely related to titanium (Ti) and zirconium (Zr). Hf has not been previously evaluated as implant material in a biologic environment. In a first experiment, 21 machined Hf non-threaded implants (test) and 21 similar Ti implants (control) were inserted in the abdominal wall of 21 rats. Animals were sacrificed after 8 days (6 rats), 6 (7 rats) and 12 weeks (8 rats). In a second experiment, 18 rabbits received 18 Hf and 18 Ti threaded implants in their tibiae, one implant in each tibia. The rabbits were sacrificed after 6, 12 and 24 weeks (6 animals/time interval). The bulk metal of the abdominal wall implants, embedded together with the surrounding tissue, was electrolytically dissolved and semithin (1 m) sections of the intact tissue–implant interface were evaluated by light microscopy (morphometry). Bone-implant contact and bone area within threads were evaluated in ground sections. In soft tissues, a fluid space containing predominantly monocytes/macrophages surrounded the abdominal implants at 8 days. At 6 and 12 weeks, a fibrous capsule, consisting of layers of macrophages and fibroblasts, surrounded the implants. Macrophages, including multinuclear giant cells, always formed the innermost layer in contact with the implant surface. No quantitative or qualitative difference in the tissue organization was detected between Ti and Hf implants. In rabbits, 6 weeks after insertion, the proximal two threads located within the cortical bone were filled with bone in contact with Hf and Ti. The distal threads contained bone marrow. After 12 and 24 weeks, mature bone was present in the proximal 3–4 implant threads. No statistically significant difference was found between Hf and Ti implants at any time periods. It is concluded that Hf is an interesting metal for biomedical applications in bone and soft tissue. © 2001 Kluwer Academic Publishers     

不同粉末粒度的粉末轧制多孔钛板的孔隙性能研究

为满足湿法冶金、氯碱、水处理、制药等行业对多孔钛板过滤元件的需求,以粉末轧制法制备多孔钛板为出发点,开展了满足轧制工艺要求的多孔钛板粉末轧制、烧结、性能测试等研究。通过对不同性能的钛粉进行粉末轧制、真空烧结,制得了宽度为420 mm、厚度不同、组织均匀的多孔钛板,研究了不同粉末性能对其孔隙度、最大孔径和透气度的影响。结果表明:随着粉末粒度的减小,多孔钛板的密度有所增大,孔隙度、最大孔径和透气度逐渐减小。其中,多孔钛板最大孔径和透气度的变化规律与模压多孔材料的相同。在追求孔隙度最大化时,以最小的轧制压力轧制成型多孔钛板,粉末粒度越大,其厚度越大。当粉末粒度相同时,多孔钛板厚度越大,其内部孔道路径越长,孔结构越复杂,气体在透过多孔结构通道时所消耗的能量也越多,透气度则越低。     

Tyrosine-derived polycarbonate membrane in treating mandibular bone defects. An experimental study.

This study was designed to evaluate the suitability of a novel bioabsorbable material in treating bone defects. A poly(desaminotyrosyl-tyrosine-ethyl ester carbonate) (PDTE carbonate) membrane (thickness 0.2-0.3 mm) was implanted into the mandibular angle of 20 New Zealand White rabbits to cover a through-and-through defect (12 x 6 mm). In group 1, the defects were left unfilled but covered with membrane and in group 2 the defects were filled with bioactive glass mesh and covered with membrane, too. Controls were left uncovered and unfilled. The animals were followed for 6, 12, 24 and 52 weeks, respectively. The material was evaluated by qualitative analysis of histological reactions and newly formed bone.We found that PDTE carbonate elicited a modest foreign body reaction in the tissues, which was uniform throughout the study. New bone formation was seen in all samples after six weeks. Group 1 had more new bone formation until 24 weeks and after this the difference settled. Based on findings of this study it was concluded that PDTE carbonate membranes have good biocompatibility and are sufficient to enhance bone growth without additional supportive matrix.     

A new titanium fiber mesh-cuffed peritoneal dialysis catheter: An experimental animal study

CAPD catheters are associated with infectious complications. To solve this problem, we developed a new catheter. In our design, sintered titanium fiber mesh material replaced the Dacron cuffs, as used in standard Tenckhoff catheters. The purpose of the current study was to compare the tissue response to new titanium-cuffed vs. Dacron-cuffed catheters. Experimental and standard Tenckhoff catheters were inserted intraperiotoneally in 12 goats, using a so-called two-stage surgical technique. In the first surgical session, the catheters were implanted. However, the percutaneous part of the catheter was buried subcutaneous. After 3-5 weeks, the percutaneous part of the catheter was exteriorized. After 14 weeks of implantation, all implants with surrounding tissue were retrieved and prepared for histological evaluation. Subsequently, we quantified: the characteristics of the fibrous tissue capsule surrounding the cuffs, the tissue inside the cuff porosity, and the epidermal downgrowth. Histologic and histomorphometric evaluation showed that titanium mesh evoked a lesser inflammatory response inside the cuff porosity compared with Dacron cuffs. Besides, the fibrous tissue capsule surrounding the titanium cuffs was significantly thinner. Supported by the obtained results, we conclude that the use of titanium fiber mesh has a great potential for application in percutaneous devices.     

The influence of micro-formation on the in-plane elastic behaviour of paper

The in-plane stiffness of a paper sheet decreases as the amount of interfibre bonding is reduced. Part of this reduction has been explained in the past as due to the absence of stress in the constituent fibrous material in directions transverse to the fibre axis in a lightly bonded sheet. A model is offered to explain how the remaining reduction of stiffness for lightly bonded sheets is dependent on the uniformity of mass distribution, i.e., the formation, of the sheet. The theory is shown to be consistent with reported experimental results.     

Formation of {111} fibre texture in recrystallised aluminium sheet

Abstract

The deep drawability of commercial purity aluminium sheets is improved by introducing a (in fcc materials rather unusual) {111} fibre texture in the sheet surface layers. An additional step of warm rolling after the conventional hot and cold rolling leads to the formation of a pronounced shear texture in the sheet surface layers. During the final recrystallisation annealing, the desired {111} texture prevails at the expense of the other shear texture components. The present paper aims to clarify the mechanisms of the formation of {111}∥ND orientations during both warm rolling and recrystallisation. The effect of the {111} surface texture on the plastic anisotropy of the resulting sheets is discussed.     

Histological evaluation of natural coral skeleton as a grafting material in miniature swine mandible

Natural coral skeleton (NCS) has recently been proposed as a bone graft substitute that enhances bone formation. The present paper describes the effects of implanting NCS in bone cavities prepared in the mandibles of miniature pig, and compares these with the effects of two alloplastic materials; a tricalcium phosphate (TCP) and a porous hydroxyapatite (PHA). On 11 pigs, 5 × 5 mm windows were created through alveolar bone of the four mandibular incisors. Three cavities were filled with the various materials and the fourth was left unfilled. The animals were slaughtered at 0, 1, 2, 4, 12, 26 and 52 weeks post-operatively and the tissues were examined histologically. Healing completed at 26 weeks for NCS and TCP, and at 52 weeks for PHA. NCS granules provided surface for cell attachment and deposition of a distinguishable organic matrix two weeks post-operatively. This matrix developed to bone after four weeks. The granules gradually resorbed and were replaced by bone at 52 weeks. The excellent properties of NCS, biocompatibility, porosity and osteogenic effect make us suggest that it might be a suitable replacement for bone grafting.     

Preparation of composite TiO2-zeolite sheets using a papermaking technique and their application to environmental improvement Part II Effect of zeolite coexisting in the composite sheet on NO x removal

Sheets with a photocatalytic action were prepared using a papermaking technique. These sheets included single TiO₂-sheet (Ti) and composite TiO₂ sheets with A type zeolite (Ti-ZeA) and Y type zeolite (Ti-ZeY). A sheet (ZeA-Ti sol) containing A type zeolite treated with TiO₂ sol was also prepared. Nitrogen monoxide (NO) was photocatalytically decomposed continuously when these sheets were used under UV irradiation. The subsequent photooxidation of NO to NO₂ and of NO₂ to HNO₃ was observed. The NO _x removal efficiencies of the sheets increased in the following order; Ti-ZeY < Ti < Ti-ZeA < ZeA-Ti sol. The reaction mechanism is discussed on the basis of the combined effects of the photocatalytic ability of TiO₂ and the function of zeolites to adsorb NO and retain the products.     

Thermoforming woodfibre–polypropylene composite sheets

Thermoforming of woodfibre–polypropylene composite sheets made without any modification of the fibres or the polymer is the focus of this paper, the emphasis being on their formability and the associated issues. Both the degree to which a material conforms to the desired part geometry after deformation and the extent to which a sheet material may be deformed before unacceptable defects occur are considered. Four thermoforming processes such as V-bending, die-match forming, air pressure forming and deep drawing have been utilised to examine both single-curvature and double-curvature deformation conditions. The technique of Grid Strain Analysis (GSA) has been applied to quantify differences in strain distributions during sheet deformation. The effects of thermoforming process parameters and sheet composition on sheet formability are also discussed. Notably, this study considers composite sheets reinforced with wood fibres rather than woodflour, enabling the study of fibre layup and fibre interlocking effects. While the tensile strengths of the composite sheets increase marginally the stiffnesses increase significantly compared to those of unreinforced polypropylene. The key deformation mechanism for layered woodfibre–polypropylene composite sheets is inter-ply shear while intra-ply shear dominates the deformation of homogeneous sheets. Forming temperature and blank size have the most pronounced effects on the formability of these composite sheets.     

Tyrosine derived polycarbonate membrane is useful for guided bone regeneration in rabbit mandibular defects

Standardized bilateral through-and-through defects (12 × 6 mm) were created extraorally in the mandibular angle of 18 New Zealand White rabbits. Animals were divided in to three groups (n = 6) according to the intended healing time. On the left side, defects were covered with a poly(desaminotyrosyl-tyrosine-ethyl ester carbonate) (PDTE carbonate) membrane wrapped around the inferior border of the mandible and fixed with bioabsorbable sutures. On the right side, the defects were filled with a mesh made of bioactive glass 13–93 and 3 wt% chitosan. The defects were covered with the same membranes. Periosteal flap was sutured over the membrane. Radiographically, bone ingrowth was seen in all specimens at 12 weeks postoperatively. At 24 weeks, completely ossified area remained approximately at the same level as at 12 weeks, but the non-ossified area decreased to almost zero. However, the bioactive glass mesh did not improve the results. Nevertheless, enveloping the defect with PDTE carbonate membrane seemed to play a crucial role in new bone formation. Based on these results, we conclude that tyrosine polycarbonate is a promising new material for guided bone regeneration.     

Osseointegration features of orthopedic Ti–10Si–5B implants

The present work reports on osseointegration features in rabbit tibia of orthopedic Ti–10Si–5B implants, which present a typical structure formed by the Ti and Ti₆Si₂B phases. No inflammatory reaction or rejection was noted after implantation for sixteen weeks of smooth and rough Ti–10Si–5B screw implants. Results indicated that the removal force for Ti–10Si–5B screws was continuously increased after implantation for sixteen weeks, suggesting that the bone integration process was achieved. Histological analysis revealed the occurrence of normal bone tissue growth and the presence of osteoblasts near the metal–tissue interface. Higher torque values were used to remove the rough Ti–10Si–5B screw implants after sixteen weeks, denoting that the surface treatment provided superior anchor for bone tissues. The absence of inflammatory reaction during implantation of orthopedic Ti–10Si–5B implants for sixteen weeks denotes the good bone compatibility of the composition alloy.     

Transdermal absorption of L-dopa from a new system composed of two separate layers of L-dopa and hydrogel in rats

To maintain the stability of L-dopa in hydrogel, a new system composed of two separate layers of L-dopa and hydrogel was developed. L-Dopa sheets were made by immersing L-dopa solution into wiper sheets and by lyophilizing them. Examination for stability of L-dopa in the L-dopa sheet revealed that its stability was maintained for at least 12 weeks, providing the sheet was kept at room temperature in a dark box. In a cutaneous absorption study of L-dopa in rats, an L-dopa sheet was attached to the shaved abdominal skin. A hydrogel composed of cutaneous absorption enhancers, water and ethanol, was spread on vinyl tape (hydrogel sheet), and this sheet was placed over the L-dopa sheet. L-Dopa that was administered transdermally effectively penetrated through the skin: The plasma level of L-dopa peaked at 30 min and remained high between 60 and 180 min after the cutaneous application. Our system, composed of two separated layers of L-dopa and hydrogel, enabled the stability of L-dopa to be maintained without losing transdermal absorption of L-dopa.     

The measurement and significance of green sheet properties for the properties of hardened fibre cement

It is common practice for manufacturers of cellulose fibre cement to measure thickness, density and water content of freshly made fibre cement as manufacturing control measures. The thickness of the green fibre cement accurately reflects the thickness in the hardened state and is therefore an instantaneous direct control. However, world standards for fibre cement typically call for fibre cement to be made to a particular strength and although density and water content may be predictive of strength in general, they do not reflect the orientation of the fibres and their contribution to the directional strength of finished product. The purpose of this paper is to introduce two tests of the properties of green fibre cement (green sheet tensile test and green sheet modulus of elasticity) and to show how the properties of the green sheets relate to those of the hardened product. It will be seen that both of these green sheet properties relate directly to the strength of the hardened sheet.     

Urothelial cell transplantation using biodegradable synthetic scaffolds

Reconstruction of the urinary bladder with bowel to restore storage capacity is associated with significant complications arising from substituting an absorptive, mucus-producing intestinal epithelium for the barrier urothelium of the bladder. To overcome these problems, we are developing a "composite enterocystoplasty" procedure to replace the epithelium of the bowel with autologous in vitro-propagated normal urothelial cells. The aims of this study were to evaluate synthetic biomaterials as delivery vehicles for the cultured urothelial cells and provide support during transfer and cell adherence to the de-epithelialized bowel wall. The surgical compliance of 12 biomaterials was evaluated, along with their ability to support urothelial cell attachment. Transfer of urothelial cells onto biomaterials as single cell suspensions or intact cell sheets was investigated. Seeding of a single cell suspension on to non-woven mesh resulted in poor cell attachment. Seeding onto woven mesh was more efficient, but the most effective transfer method involved producing an intact cell sheet that could be combined with woven, knitted and non-woven biomaterials. Transfer of the cell sheet : mesh complexes onto a de-epithelialized bladder stroma produced a stratified epithelium incorporating the strands of the mesh and expressing urothelial-associated antigens after 48 h in organ culture. Thus, we have developed and evaluated a suitable transfer method for in vitro propagated urothelial cells to be used in "composite enterocystoplasty".