ISSN:0920-5063    

DOI:10.1163/156856295X00616

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Silicones, model biomaterials with almost ubiquitous applications, are the focus of a contentious debate. In this review, we will consider both established physicochemical phenomena and immunological phenomena; and then consider the human clinical phenomena that relate directly to them. We will explore the two competing theories of the biological activity of silicones, and we will discuss the weaknesses in the various arguments that silicone is inert. We conclude that from a pathophysiological perspective, silicones should be expected to be bioactive materials and that the physicochemical and immunological data at the experimental level are compelling.

ISSN:0920-5063    

DOI:10.1163/156856295X00625

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Current estimates are that up to a million women in the U.S. have breast implants with the predominant type being the silicone gel implant. Concerns have been raised regarding the safety of silicone gel breast implants with focus upon whether escaped gel might cause inflammatory and immune responses that subsequently lead to autoimmune rheumatic diseases such as progressive systemic sclerosis (scleroderma), systemic lupus erythematosus (SLE), Sjögren's syndrome or rheumatoid arthritis. A spectrum of illnesses ranging from local symptoms to systemic disease is seen in some patients with silicone breast implants, however, it remains to be determined whether such illnesses in these patients are coincidentally associated or are secondary to the implants. Our understanding of the relationship between the presence of autoimmune rheumatic diseases and silicone breast implants is limited. The available data indicate that silicone elicits a minimal immunological response as compared to conventional antigens. The histological, immunological and epidemiological experimental data derived from patients with silicone implants, as well as those from animal studies, are reviewed. These data do not convincingly demonstrate that there is a cause and effect relationship between silicone breast implants and autoimmune diseases. Further investigations are needed to clarify the interaction of silicone with the cellular and humoral immune systems, as well as with host and environmental factors.

ISSN:0920-5063    

DOI:10.1163/156856295X00634

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Silicone materials have been used in medical applications for at least 30 years. Despite this long history of use the question whether silicones can mediate an immunological reaction that may be detrimental to the host remains unanswered. Most studies on the biocompatability of silicones conclude that silicones are chemically stable compounds, which however are often capable of eliciting a benign chronic inflammatory response. Recently, our laboratory has conducted a series of animal experiments aimed at determining the immunological adjuvancy potential of silicone-gel taken from commercial breast implants. Our previous studies have indicated that silicone-gel is a potent humoral (antibody) adjuvant. Our present studies have found that silicone-gel is capable of eliciting auto-antibodies to rat thyroglobulin and bovine collagen II. However this immune response did not produce any histological evidence of thyroiditis or arthritis. Theories to explain why silicone-gel behaves as an adjuvant are discussed along with discussion of the hypothesis on the desirability of replacing silicone-gel with a more hydrophilic material in bioimplants.

ISSN:0920-5063    

DOI:10.1163/156856295X00643

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In vivo and in vitro studies, case reports and population studies show that: (1) silicone is immunogenic; (2) silicone is biodegradable and transported via the reticuloendothelial system to distant locations; (3) silicone breast implants "leak" and in turn silicone migrates outside the breast tissue; (4) case reports and population studies document an autoimmune reaction and immunological dysfunction in patients with silicone breast implants; (5) these immunological abnormalities and symptoms are reversible upon removal of the breast implants (in 50-70% of cases). The criteria to establish medical causation are defined, and based on those criteria it is concluded that silicone breast implants cause immunological disease.

ISSN:0920-5063    

DOI:10.1163/156856295X00652

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

More than 1000 patients with rheumatic disorders and silicone implants have been reported. In this review, the clinical features of patients with scleroderma, inflammatory myositis, systemic lupus erythematosus and silicone implants are discussed. The clinical features of the most common rheumatic disorder associated with silicone implants, the "Silicone Implant Associated Syndrome", are introduced. In addition, other local regional, and neurologic disorders associated with silicone implants are discussed. This comprehensive clinical review provides the clinician with information regarding the common symptoms, signs and laboratory features of rheumatic disorders of patients with silicone implants.

ISSN:0920-5063    

DOI:10.1163/156856295X00661

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Static and dynamic human blood adsorption studies on polydimethylsiloxane, PDMS, and silicone rubber show that these materials are similar, but not identical, in their protein adsorption behavior. Fibrinogen, immunoglobulin G, and albumin were the predominant proteins identified on the material surfaces with fibronectin, Hageman factor (factor XII), and factor VIII/vWF adsorbing at intermediate levels. While the protein adsorption characteristics for the two materials were similar, higher levels of the respective proteins were identified on silicone rubber compared to PDMS. Monocytes/macrophages incubated on PDMS, silicone rubber and low density polyethylene, LDPE, with or without protein adsorption produced variable levels of IL-1β, IL-6 and TNF-α dependent on the polymer and adsorbed protein. PDMS showed lower levels of the cytokines when compared to the polystyrene control and polyethylene. Protein preadsorption on the PDMS, polystyrene, and LDPE surfaces showed lower levels of cytokines when compared to the respective quantities produced with no protein adsorption suggesting a passivating effect by the protein adsorption phenomenon on monocyte/macrophage activation. Preadsorption of IgG, fibrinogen or fibronectin decreased the quantitative expression of IL-1β but increased the functional activity in the thymocyte proliferation assay indicating the presence of monocyte/macrophage activation products which either downregulated the activity of IL-1β or upregulated thymocyte proliferation in an independent fashion.

ISSN:0920-5063    

DOI:10.1163/156856295X00670

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In order to prevent epidermal down growth when a silicone percutaneous device was implanted, immobilization of collagen was performed onto the surface of a silicone device. The immobilization of collagen was achieved through covalent bonds between the amino groups in the collagen molecules and the carboxyl groups in poly (acrylic acid) chains grafted onto the silicone device surface. When the collagen-immobilized silicone device model was percutaneously implanted in rabbits, no sign of epidermal down growth was observed even 7 weeks after implantation, while the epidermis reached down to the deep part of the dermis as early as 3 weeks after implantation when collagen was not immobilized onto the device model surface. To have tighter fixation of the device models to the surrounding dermal tissue, the silicone device model was covered with a polyethylene sponge having an average interconnecting pore size of 150 μm. Collagen immobilization was also performed onto the sponge surface. Both the collagen-immobilized silicone device models as well as the non-treated models with polyethylene sponge were percutaneously implanted in rabbits and epidermal down growth as well as the occurrence of bacterial infection was examined. Without collagen immobilization onto the sponge surface of the device model, bacterial infection was noticed as early as 2 weeks after the implantation. The number of infected device models increased as the implantation time became longer and bacterial infection was observed in six out of severn device models at the 10th week post implantation. When the sponge surface was immobilized with collagen, bacterial infection was noticed in only one model at the 5th week after implantation. Six out of seven implanted device models with collagen immobilization were free of bacterial infection until the animals were sacrificed 30 weeks after implantation.

ISSN:0920-5063    

DOI:10.1163/156856295X00689

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Tissue attachment to substratum surfaces is of central importance to the in vivo performance of prosthetic implant materials. It is not yet understood why connective tissue does not attach to the surface of silicone or any other polymeric material. Recently the authors have conclusively demonstrated that micro-range surface roughness modifies cellular responses in cell culture and modifies biocompatibility and tissue attachment in vivo significantly. In order to better understand the basic interactions between living cells or tissues on one hand and man-made substratum surfaces on the other hand, the germane literature is reviewed here. Cells adhere to substratum surfaces mainly through focal adhesions which are a complex of intracellular, transmembrane and extracellular proteins. Adhesion is facilitated and modified by proteins adsorbed to the substratum surface. Protein adsorption in turn is modified by the underlying substratum surface properties including surface chemistry, charge, and free energy. When silicone and other polymeric implants having well-defined surface topographic features including pores, pillars, or grooves were implanted, the tissue response to these implants was strongly influenced by the dimensions of these features as well as by other geometric details. Highest biocompatibility along with tissue attachment was seen when topographic features had dimensions of 1-3 μm and a uniform distribution. Cell culture studies revealed that topographic features affect cellular alignment, direction of proliferation, cellular attachment, growth rate, metabolism, and cytoskeletal arrangement. Since discontinuities or curvatures associated with topographic features may represent local changes in surface free energy, it is hypothesized that these discontinuities trigger changes in protein adsorption, protein configuration, and cellular response.

ISSN:0920-5063    

DOI:10.1163/156856295X00698

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor