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PubMed1981

[Liquid storage media for vascular prosthesis of biological origins : their impact on biocompatibility (author's transl)].

Unlike synthetic arterial substitutes which are supplied as presterilized, dry-packaged products with potentially indefinite shelf lives, arterial prosthesis of modified biological origin must stored in less convenient liquid preservative media. These preservatives can affect the post-implantation performance and the biocompatibility of the devices. In order to identify the most suitable media, a modified "in vitro" cell culture test method was developed. It makes use of endothelial cells prepared from the aorta of chick embryo. In general, the prosthesis stored in liquid media had a disappointing performance from the point of view of neo-endothelium development and adhesion. Residual cytotoxicity was also noted for most of these currently used prosthesis storage and pre-surgical preparation protocols. Although devices stored in physiologic media showed adequate biocompatibility according to this cell culture test, it appears that neo endothelialization does not proceed concurrently with healing. Cellular development where present, adheres poorly to the substrate and cannot resist the shear forces of normal blood flow. Pre-implantation treatment of such prosthesis with cellular growth-promoting substances may enhance cell-prosthesis adhesion.

Animals↗

PubMed1995

Development of a ferrocene-mediated needle-type glucose sensor covered with newly designed biocompatible membrane, 2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate.

To prepare the long-life and stable glucose sensor, we developed the ferrocene-mediated needle-type glucose sensor covered with newly designed biocompatible membrane, 2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate (MPC-co-BMA) membrane. In this membrane, the hydrophilic phosphorylcholine chains were grafted on the hydrophobic polymer surface. 1. The poly(MPC-co-BMA) membrane inhibited platelet activation and protein adhesion on the surface, showing excellent biocompatibility. These results suggested that the hydrophilic phospholipids chains might have the potential for suppressing activation and adsorption of biochemical molecules. 2. The ferrocene-mediated needle-type glucose sensor covered with poly(MPC-co-BMA) membrane achieved excellent results in vitro. Subcutaneous tissue glucose concentrations were measured in a wide range from 1.7 to more than 16.7 mmol/l. The correlation between subcutaneous tissue (Y) and blood (X) glucose concentrations was Y = 1.04X + 0.12 (r = 0.98). The subcutaneous tissue glucose concentrations could be monitored precisely for 7 days without any in vivo calibrations, and for 14 days by introducing in vivo calibrations. We therefore conclude that this sensor is stable and reliable, as compared to any other glucose sensors we developed.

Adult↗

PubMed1995

Influence of surface texture and charge on the biocompatibility of endovascular stents.

BACKGROUND: The mechanical behaviour and the surface characteristics of endovascular stents are key factors determining stent patency. In-vitro studies have suggested that surface texture and charge alter the biocompatibility of metallic stents. In this study, the influence of surface texture and charge of metallic stents on thrombosis and neointima formation was evaluated in a rabbit model. METHODS: Twenty-four stainless steel Palmaz-Schatz stents were coated either by an electrochemical deposition of metal on the stent surface or were coated with a metallic film which was implanted into the stent surface by argon ion bombardment. The coatings consisted of platinum, gold, or copper. Coated and uncoated control stents were implanted in rabbit iliac arteries. As antithrombotic therapy, 500 IU heparin and 60 mg aspirin was given intravenously before stent implantation, followed by 60 mg aspirin intravenously every third day for 4 weeks. Thrombus and neointima formation in arterial cross-sections of 24 coated stents were compared with 19 uncoated stents using quantitative, computer-assisted histomorphometry and transmission electron microscopy. RESULTS: A higher stent surface porosity and more surface cracks after stent expansion were found after galvanization than after ion implantation. The in-vitro surface potentials of uncoated steel, copper-, and gold-coated or platinized stents were +150, +120, +180, and +180 mV, respectively. Four weeks after implantation, six of 14 galvanized stents, but none of the uncoated or ion bombarded stents, were occluded by a thrombus. Neointimal hyperplasia was increased in stents coated by galvanization compared with stents coated by ion implantation. In both study groups, the most electropositive coating (platinum or gold) induced markedly less neointima formation than the least electropositive (copper). CONCLUSION: Stent surface texture was the most important factor determining biocompatibility of coated Palmaz-Schatz stents in this study. In contrast to suggestions derived from in-vitro studies, the charge of stents does not seem to play a major role with respect to stent thrombogenicity. Low stent charge correlates with an increased neointima formation.

Animals↗

PubMed1995

Changes in biocompatibility of dialysis fluid during its dwell in the peritoneal cavity.

OBJECTIVE: To evaluate the changes in biocompatibility of peritoneal dialysis solutions during intraperitoneal dwell. DESIGN: We studied the effect of the drained dialysates at time 0 and after 30, 60, 120, 240, and 360 minutes of intraperitoneal dwell on the growth of peritoneal mesothelial cells and fibroblasts and the synthesis of proteins by these cells. On one day the patients were dialyzed with glucose-based Dianeal and on alternate days with an amino acid-containing solution based on Travasol. PATIENTS: Dialysates were collected from 4 patients during continuous ambulatory peritoneal dialysis (CAPD) training. RESULTS: Unused dialysis solutions containing glucose or amino acids inhibit growth of mesothelial cells and fibroblasts. Dialysates obtained after 30 or 60 minutes of intraperitoneal dwell support the growth of these cells in a way similar to 10% fetal calf serum, but dialysates drained after a longer dwell of 120-360 minutes had a stronger effect on growth of these cells than did serum. All glucose-based dialysates stimulate the synthesis of collagen in mesothelial cells, whereas they reduce the synthesis of non-collagen proteins. All glucose-based dialysates reduce the synthesis of collagen and non-collagen proteins in fibroblasts compared with the production of these proteins in the presence of serum. CONCLUSION: Changes in the properties of the dialysis solutions during their intraperitoneal dwells do not seem to increase their biocompatibility. Indeed, excessive mitogenic effect and the stimulation of collagen synthesis of the dialysates may induce pathological changes in the peritoneum.

Biocompatible Materials↗

PubMed1995

In vitro biocompatibility of a heat-sterilized, low-toxic, and less acidic fluid for peritoneal dialysis.

OBJECTIVE: The aim of this study was to investigate a peritoneal dialysis (PD) fluid (PD-Bio), produced with the intention of reducing the amount of glucose degradation products and to increase the final pH. The heat sterilization of the fluid was performed with the glucose separated from the electrolytes. After sterilization the two solutions were combined. METHODS: The in vitro biocompatibility of PD-Bio was measured as the inhibition of cell growth of a cultured fibroblast cell line and as the stimulated release of interleukin-1 beta from cultured human mononuclear cells. The glucose degradation products were measured as UV absorbance at 228 nm or 284 nm and the concentration of aldehydes was estimated with high-performance liquid chromatography and gas chromatography. RESULTS: Our results demonstrate that in comparison to conventional PD fluids the pH of PD-Bio was increased, to about 6.5. Due to less contaminating glucose degradation products in PD-Bio, basal cytotoxicity was significantly decreased for both 1.5% and 4% glucose-containing fluids, and the stimulated release of interleukin-1 beta was normalized compared to sterile filtered controls with the same pH. UV absorbance measured at 228 nm was decreased, whereas the absorbance at 284 nm was equal to that of a conventional fluid. In PD-Bio the concentrations of formaldehyde, acetaldehyde, methylglyoxal, and 2-furaldehyde were found to be below the detection limit, whereas glyoxal was present in the same and 5-hydroxymethylfurfural (5-HMF) in higher concentrations than in conventionally produced PD fluid. CONCLUSIONS: The results demonstrate that it is possible to improve biocompatibility of PD fluids by simply changing the way the fluid is produced.

Acetaldehyde↗

PubMed1994

Individual differences in biocompatibility responses to hemodialysis.

There are very few reports in the literature on individual differences in the response to dialysis treatment. We studied the influence of the individual patient, dialysis membrane quality, blood-flow (Qb) and surface area on leukocyte activation and complement generation (C3a) during 234 hemodialysis treatments using Cuprophan (CU), hemophane (HE) and polyamide (PA) dialyzers. The most common reaction was a decrease in leukocyte count and an increase in C3a after 15-minutes of treatment. Leukocyte overshoot by the end of dialysis was observed at high Qb for all three membranes but at low Qb only during CU treatments. The reaction patterns were influenced by the quality of the membrane, area and Qb. Analysis of each individual patient showed for a large number of treatments reaction patterns corresponding to those described in the literature. However, some patients reacted differently. In four patients (20%), the nadir in leukocyte count and maximum in C3a concentration was reached considerably later during CU-dialysis. Three patients were devoid of pronounced early leukocyte response but presented with the late overshoot during CU-dialysis. Three other patients reacted with an early drop in leukocyte count and a rapid increase in C3a generation during PA treatments but not during HE treatments. Three other patients reacted vice versa. A particular mode of dialysis treatment may thus be biocompatible for some patients but not necessarily for all. In the case biocompatibility is desired the individual response to the particular dialysis mode needs to be identified. The underlying mechanisms warrant further studies.

Adult↗

PubMed1994

Biocompatibility studies on peritoneal cells.

This review outlines the problems involved in assessing the biocompatibility of PD fluids. It has summarized the data available from conventional in vitro studies and highlights many of the inadequacies of this approach. In vivo data are lacking both on host defense and on the clinical effect of changing conventional PD fluids for a more "ideal" formulation. The best parameters for assessing biocompatibility need to be defined. Alternative formulation of fluids must be aimed towards (1) a system that interferes minimally with host defense, and (2) a system that maintains the integrity of the peritoneal membrane for ultrafiltration and clearance. Cell culture studies should be designed to model the in vivo situation. Ex vivo studies (cells exposed within the peritoneal cavity) should be used to support in vivo findings. Finally, in vitro results must be related to clinical significance, and changes in fluid composition should be followed by improvements in clinical outcome.

Biocompatible Materials↗

PubMed1994

Biocompatibility and risk of infection in haemodialysis patients.

Infection remains a major cause of morbidity and mortality in the dialysis patient. Most of these infections are bacterial and often lead to sepsis. In this review the possible influence of the biocompatibility of the dialysis membrane on the incidence of bacterial infections is discussed. Specifically, the role of the membrane on granulocyte function such as phagocytosis, adhesion, and production of reactive oxygen species is shown to be adversely affected by recurrent exposure to complement-activating membranes. Recent clinical studies also support the notion that dialysis with bioincompatible membranes is associated with a higher incidence of clinical infections than membranes that are more biocompatible.

Biocompatible Materials↗

PubMed1993

Are total hip prostheses implanted with the use of methylmethacrylate biocompatible?

OBJECTIVES: The biocompatibility of total hip replacement prostheses and methylmethacrylate cement which is used for fixation of the prosthetic components has been subject to debate for three decades. METHODS: We have studied the host response to total hip replacement prostheses in a number of clinical and experimental investigations. RESULTS: Methylmethacrylate cement is immunologically relatively inert while it causes, in in vitro experiments and in vivo, a foreign body type of reaction. In cementless prostheses, the wear of polyethylene which is used for lining of the acetabular component causes a similar foreign body type of reaction. CONCLUSION: Ultimately, the total hip prosthesis cannot be made invisible to the host system. The host response can be controlled and reduced, but not eliminated by technical improvement and development of more biocompatible materials.

Biocompatible Materials↗

PubMed1993

Fibrinolytic activity during hemodialysis: a biocompatibility-related phenomenon.

According to recent reports, fibrinolytic activity may be enhanced during hemodialysis. The aim of this work was to study the fibrinolytic activity in uremic patients, and to evaluate the effect of membrane biocompatibility on the fibrinolytic system during hemodialysis. Tissue plasminogen activator (t-PA), t-PA antigen, plasminogen activator-inhibitor (PAI), plasminogen (PL) and alpha-2-antiplasmin (AP) were measured in 10 uremic patients on maintenance hemodialysis treated sequentially with Cuprophane and polyacrylonitrile (AN69) membranes. Blood samples were obtained before and at 15, 60 and 120 minutes after the initiation of dialysis. Blood was also collected from 20 healthy individuals who served as controls. During cuprophane dialysis, t-PA increased significantly at 60 minutes (14.8 vs. 8.4 IU/ml, P < 0.05) and at 120 minutes (13.8 P < 0.01). This was accompanied by an increase in t-PA antigen, which was significant at 15 (5.1 vs. 13.1 ng/ml), 60 (15.2) and 120 (9.6) minutes (P < 0.05) of dialysis. However, during AN69 dialysis t-PA and t-PA antigen plasma levels remained stable. No significant changes were observed in PL, AP or PAI during hemodialysis with either membrane. In conclusion, hemodialysis enhances fibrinolytic activity, which is likely the result of t-PA Ag release. Therefore, this phenomenon seems to be closely related to dialysis membrane biocompatibility.

Adult↗

PubMed1995

[Biocompatibility and extracorporeal circulation].

Present knowledge about biocompatibility during extracorporeal circulation, especially in hemodialysis, has been reported. Clinical implications of membrane biocompatibility on coagulation, fibrinolysis, complement and kalikrein cascade has been analyzed. Particular attention is for the platelet activation in hemodialysis and ist effect upon the coagulation system and dialytic efficiency. The the role of epoprostenol sodium salt (prostacyclin) continous infusion in hemodialysis has been described. Finally future perspectives of anticoagulation during dialytic treatment have been advanced.

Biocompatible Materials↗

PubMed1996

Biocompatibility and immunology in the encapsulation of islets of Langerhans (bioartificial pancreas).

Successful transplantation of encapsulated islets (bioartificial pancreas) would circumvent problems of islet availability and rejection in the treatment of insulin-dependent diabetes with biological organ replacement. Alginates are widely used as a hydrogel matrix or membrane for immunoprotected transplantation. A major problem in the use of diffusion-based devices is the biocompatibility of the material used. The foreign body reaction after implantation of empty microcapsules into different compartments in rats, dogs and pigs is evaluated in this article. However, biocompatibility of the bioartificial pancreas has three different aspects: reaction of the entrapped islet to the encapsulation technique and material; reaction of the recipient against the incorporated device ( = foreign body reaction); and finally the reaction of the recipient against the encapsulated islet ( = immunology of bioartificial pancreas). It is obvious from different experiments that even if foreign body reactions (reactions against material) are almost abolished the recipient may react against material released from the encapsulated islet. In conclusion, transplantation of encapsulated islets induces various morphological reactions (i.e. inflammation and fibrosis) as a result of a variety of donor and recipient related factors. Therefore, the use of an adequate animal model that reflects the human situation is essential for progress in the development of a bioartificial pancreas.

Alginates↗

PubMed1996

Material properties, biocompatibility, and wear resistance of the Medtronic pyrolytic carbon.

Pyrolytic carbon is the material of choice for components in the majority of heart valves available today. Many manufacturers have vertically integrated their manufacturing capabilities to include their own carbon manufacturing facilities. Medtronic is no exception. Because of the critical nature of pyrolytic carbon to the success of a valve design, a series of in vitro tests were conducted to determine the relative equivalence of Medtronic and CarboMedics, Inc. (CMI) pyrolytic carbon based on the Medtronic HallTM design. Correlation between in vivo and in vitro pyrolytic carbon wear is provided based on an analysis of explanted Medtronic Hall discs manufactured by CMI. Material, physical, chemical, and biocompatibility proprieties for Medtronic carbon were determined using standardized techniques. Structural integrity of the discs was evaluated by accelerated cyclic testing to determine depth of wear characteristics. Explanted valves were subjected to identical depth of wear analysis. No statistical difference was found between CMI and Medtronic pyrolytic carbon discs based on mechanical and physical properties and depth of wear on both inflow and outflow disc surfaces. Furthermore, evaluation of CMI discs after explant from human subjects confirms similar wear characteristics with a half life in excess of the 570 years projected from the in vitro experiments. In summary, material properties, structural integrity and biocompatibility testing conducted on heart valve discs made by Medtronic showed results virtually identical to those from testing of discs made by CMI.

Biocompatible Materials↗

PubMed1996

Biocompatibility studies on glass ionomer cements by primary cultures of human osteoblasts.

Glass ionomer cements (GICs) are materials largely employed in the dental field that have been considered recently as cements in orthopaedic surgery for their proven osteogenic features. The aim of this study was to compare the response of cultured human osteoblastic cells to a number of commercial glass ionomer cements in order to provide indications useful for the further development of formulations that have potential for use as cements or implants in repair and replacement of bone tissue. The GICs tested were: Ketac-Fil Aplicap, lonocem lonocap 1,0, GC Fuji II, GC Fuji II LC and Vitremer 3M. Several features such as plating efficiency, adhesion and morphology of the cells were studied, as well as the only specific biochemical parameter of osteoblastic phenotype, namely osteocalcin production. In addition, the colonisation of materials by osteoblastic cells was verified by means of scanning electron microscopy. Altogether, the results obtained indicate that four of the five glass ionomer cements tested are biocompatible, showing vital cells adhering to the materials, proliferating and expressing the biochemical markers of osteoblastic phenotype, whereas Vitremer 3M, although currently employed in the dental field, exhibits a great cytotoxicity toward the cells. The adverse reaction of this GIC can be attributed to the leaching of at least two components of the polyacidic phase evidenced by protonic magnetic resonance analysis (PMR), namely 2-hydroxyethylmethacrylate (HEMA), and an unidentified acidic species. The addition of pure HEMA at the same concentrations found by means of PMR to cultures of osteoblastic cells resulted in a complete cell death. Our results also show that in vitro methods employing primary cultures of human cells specific to the implant sites of prostheses are appropriate and suitable tools for evaluating biocompatibility of materials. Furthermore, this kind of approach can provide indications useful in the design of novel materials as well as in improving the characteristics of the formulations already available.

Biocompatible Materials↗

PubMed1997

Biocompatibility and osteoconductivity of the pyrost bone substitutes.

The purpose of this study was to re-evaluate the bone regeneration power and the in vitro biocompatibility of the Pyrost bone substitute. Twenty-four adult New Zealand White rabbits were used. Bony defect over both iliac crest and mid-diaphyseal portion of the ulna bone were created. Appropriate sized-block of Pyrost bone substitute were implanted. Four of the animals were killed at each postoperative month to evaluate its bone regeneration power by histologic study. The Pyrost bones were co-cultured with osteoblasts to evaluate its biocompatibility. The results showed that Pyrost bone substitute was quite stable and incorporated well with active bone regeneration. The Pyrost heal better at the iliac crest than at the ulnar defect. The Pyrost was compatible to the osteoblasts. Osteoblasts had successfully seeded and mitotically expanded on the porous surface of the Pyrost bone graft. The result showed that Pyrost bone obviously exerts an intense stimulus on osteo-regeneration in the presence of osteoblasts. We consider Pyrost to be an alternate to the conventional preserved allografts that is occasionally necessary.

Animals↗

PubMedDate not supplied

In vitro biocompatibility of bicarbonate-based peritoneal dialysis solutions.

OBJECTIVE: To review the current literature on the in vitro biocompatibility of peritoneal dialysis solutions buffered with bicarbonate and compare them to existing conventional lactate-buffered solutions. RESULTS: Conventional lactate-buffered solutions are known to inhibit or modulate cell functions related to host defense mechanisms; these effects are mediated by their low pH in combination with lactate concentration, as well as their glucose content, associated osmolality, and the presence of glucose breakdown products. CONCLUSIONS: Bicarbonate-buffered solutions appear to present a viable alternative for use in CAPD based on their significantly improved biocompatibility profile. The results of on-going clinical trials will clarify whether these in vitro data will impact significantly on peritoneal host defence, infection rate and the long term function of the peritoneal membrane in vivo.

Bicarbonates↗

PubMed1997

Biocompatibility: complement as mediator of tissue damage and as indicator of incompatibility.

The fully biocompatible surface is the host's own intact endothelium. Blood contact with a damaged or foreign endothelium, or with an artificial surface, will lead to a certain degree of activation of the defense systems. Complement is one of these systems which has a unique property to distinguish between 'self' and 'non-self'. Recent data using complement-specific inhibitors like soluble CR1 and monoclonal antibodies to C5 have shown that complement is not only associated with, but in fact contributes to, the whole body inflammatory reaction seen as a complication to cardiopulmonary bypass (artificial surfaces) and is responsible for the hyperacute rejection of xenografts (foreign endothelium). Complement activation, as measured by assays specific for neoepitopes exposed in the activation products, is a sensitive indicator of bioincompatibility. These assays have been increasingly important after a causal link between complement activation and tissue damage was demonstrated. Efforts have been made to improve the biocompatibility of artificial surfaces, including coating with heparin. This procedure not only improves coagulation compatibility, but also markedly reduces complement activation. Models to study complement compatibility in vitro and in vivo are described, and recommended complement activation assays reviewed.

Animals↗

PubMed1997

Biocompatibility of silver-modified polyester for antimicrobial protection of prosthetic valves.

BACKGROUND AND AIMS OF THE STUDY: The biocompatibility of a silver-coated polyethylene terephthlate (PET, polyester) fabric for the inhibition of prosthetic valve endocarditis (PVE) associated with mechanical heart valves (MHVs) was assessed. The infrequency of PVE is outweighed by mortality rates commonly exceeding 50%. These high mortality rates have been attributed to the poor effect of antibiotic therapy on colonized valves and infected myocardial tissue. Silver has been used as an antimicrobial for centuries due to its general effectiveness and relative lack of toxicity. Our previous work has shown PET polyester fabric coated with metallic silver by an ion beam-assisted deposition (IBAD) process to: (i) be effective in vitro in the inhibition of microbial attachment and colonization; (ii) be tightly adherent and low leaching; and (iii) promote tissue ingrowth and the organization of tissue pannus in a short-duration (five weeks) sheep mitral mechanical heart valve model. METHODS: This paper addresses additional biocompatibility assessment consisting of a cell compatibility assay in which serum extracts of silver-coated fabric were exposed to fibroblasts for 48 hours, after which cell viability and function were measured. The amount of silver in the extract was measured using elemental analysis techniques. RESULTS: No signs of toxicity were seen in the cells until the extract concentration reached 1200 p.p.m. Ten-week duration mechanical valve replacement studies in sheep with uncoated or coated polyester sewing cuffs showed comparable tissue ingrowth and mature pannus with a suggestion of a thinner pannus on the silver-coated fabric. Additional antimicrobial testing confirmed the effectiveness of this coating in inhibiting colonization of polyester fabric. CONCLUSIONS: These current results, together with the earlier data, suggest that IBAD silver coating on polyester facilitates healing and may provide protection against PVE.

Animals↗