|Articles about Biomaterials|
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| Reconstruction of old radical cavities and long-term results
Magliulo, G., R. D'Amico, et al. (2004), J Otolaryngol 33(3): 155-9.
Abstract: Various techniques and materials have been proposed to deal with the problems that concern radical cavities, such as recurrence of the inflammatory process, the need for regular medication, and social inconvenience (eg, inability to practice water sports, working in an adverse enviroment). This article provides a detailed report of the results of revalidation of old radical cavities using hydroxyapatite granules as a filling. The material was incorporated with fibrin adhesive to fill the mastoid cavity and was covered with a sheet of bone pate sealant. Twenty-eight patients with chronic discharging old radical cavities were selected for this study (mean follow-up 11.4 years; range 10-14 years). At the 6-month follow-up, grafting was successful in 25 patients, whereas the functional outcomes showed an air-bone gap below 30 dB in 18 patients. No postoperative sensorineural hearing loss was observed. The long-term follow-up demonstrated a slight worsening of the initial findings; four other patients had reperforation of the tympanic membrane, and hearing deteriorated in five patients to above 30 dB air-bone gap. These results could be a consequence of an alteration in the function of the eustachian tube and of the severity of the preoperative pathologic processes.
| Reconstruction of orbital floor fracture with polyglactin 910/polydioxanon patch (ethisorb): a retrospective study
Buchel, P., A. Rahal, et al. (2005), J Oral Maxillofac Surg 63(5): 646-50.
Abstract: PURPOSE: We sought to evaluate the effectiveness and the complications related to the use of Ethisorb (resorbable alloplastic material) in the reconstruction of orbital floor fractures. PATIENTS AND METHODS: We retrospectively reviewed the charts of all patients who underwent orbital floor fracture reconstruction with Ethisorb since 2001. We only included patients with a minimum follow-up of 3 months. The following data were recorded for every patient: age, gender, cause of trauma, time from trauma to surgery, signs and symptoms, concomitant ocular injuries, radiographic analysis, pertinent intraoperative findings (including the type of approach), follow-up time, and postoperative complications. RESULTS: Eighty-seven patients were included in the study. Twenty-one patients (24.1%) experienced postoperative complications. Of these, only 3 patients (3.4%) had permanent complications directly related to the Ethisorb membrane (diplopia, enophthalmos). Two of these patients required revision surgery and are discussed in the article. CONCLUSIONS: The results of our study demonstrate the effectiveness of Ethisorb in the repair of small-to-moderate orbital floor fracture defects (up to a maximum size of 2 x 2 cm).
| Reconstruction of the common bile duct by a vascular prosthetic graft: an experimental study in pigs
Christensen, M., H. B. Laursen, et al. (2005), J Hepatobiliary Pancreat Surg 12(3): 231-4.
Abstract: BACKGROUND/PURPOSE: The purpose of the present study was to investigate whether it was possible to use a vascular graft for reconstruction of the common bile duct (CBD) in pigs. METHODS: Eight pigs, each weighing approximately 60 kg, were used for the experiments. The gallbladder was dissected and the cystic duct and cystic artery were ligated and divided. The CBD was displayed and divided. Then the CBD was reconstructed with a standard walled expanded polytetrafluoroethylene (ePTFE) vascular graft (internal diameter 4 mm) by means of 12 interrupted monofilament glycomer 63 (Biosyn) 4.0 sutures. The ends of the vascular graft were inserted into the CBD and the sutures were placed through the graft and the CBD in such a way that the latter would cover the former. The anastomotic line was covered by fibrin glue. On postoperative day 8, a laparotomy was performed; the pigs were investigated for signs of gall leakage, and cholangiography was performed. Blood samples for the determination of liver parameters were taken before the primary surgery and before the explorative laparotomy. RESULTS: At evaluations on the eighth postoperative day, all animals except one were without signs of bile leakage. One pig had an encapsulated biloma. Another animal had to be operated on day 6 because of illness, and laparotomy showed a perforated gastric ulcer, but no bile leakage. Cholangiography revealed slight intrahepatic dilatation in all animals. Bilirubin and alkaline phosphatase levels were unaffected by the surgery. CONCLUSIONS: Reconstruction of the CBD by means of a vascular graft seems to be a safe procedure in the short term in a pig model.
| Reconstructive surgery of male urethra using human amnion membranes (grafts)--first announcement
Koziak, A., A. Marcheluk, et al. (2004), Ann Transplant 9(4): 21-4.
Abstract: OBJECTIVE: Assessment of technical aspects of the surgical procedure and usefulness, suitability and efficacy of human amnion grafts as a biomaterial in reconstructive surgery of strictured male urethra. PATIENTS AND METHODS: Human amnion membranes were used in 2 men suffering from long, recurring strictures of urethra. Narrowed part of urethra was careful prepared and cleaned of adjacent tissue. Then a longitudinal incision was performed through the whole length of strictured segment and then it was covered with human amnion membrane. RESULTS: Hospitalization time 4 to 5 days. The Foley catheter was removed 2 weeks after surgery 3 months after surgery controlled urethrographies and urethroscopies show wide urethra lumen, wider than in adjacent parts. In urethroscopy operated place covered with epithelium, smooth, without scare. CONCLUSIONS: Human amnion grafts and described technique seem to be a promising method of managing long, recurring male urethra strictures but need long-term follow-up and analysis of more cases.
| Reconstructive surgery of the extensive ureter strictures using human dura mater allografts
Koziak, A., P. Kania, et al. (2004), Ann Transplant 9(4): 12-6.
Abstract: OBJECTIVE: To present and evaluate our experiences with use of human dura mater allografts in reconstructive surgery of long ureter strictures; first human derived, collagen based, oligocellular biomaterial utilized in genitor-urinary reconstructive surgery. To describe on the basis of our experiences with dura mater preferable from a technical and biological standpoint features of biomaterial as a matrix for the ureter regeneration in this condition. We also assessed a technical aspects, suitability and efficacy of the new operative method. PATIENTS AND METHODS: Between 1980 and 1992, in our search for ideal biomaterial useful for reconstructive surgery of extensive ureter obstruction we used to apply human dura mater allografts. A total of 6 females and 2 males were treated with reconstructive surgery with human dura mater allografts utilized for supplementation of the ureter wall defect. Diagnosis was based on ultrasonography, excretory urography and retrograde ureteropyelography. Imaging studies revealed obstructed ureter segment of at least 4 cm length. RESULTS: In all cases procedure was completed without any complications. Hospitalization after the surgery lasted approximately 8-10 days. Early and late follow-up excretory urography demonstrated lack of obstruction in the operated ureter segment. Long term follow-up of 12 months to 18 years (meanly 8,75 years) showed no signs of renal function deterioration, without urine obstruction on the operated side in all patient. Fluoroscopy scans showed signs of peristaltic wave in the operated ureter segment. CONCLUSIONS: Both a supplementary biomaterial used and a new operative method proved to be a promising option in reconstruction of long ureter strictures. Unfortunately a threat of prion related diseases, which resulted in exclusion dura mater grafts and all biomaterial originated from nervous system from transplantology, forced us to search for new suitable material.
| Rectocele repair using biomaterial augmentation: current documentation and clinical experience
Altman, D., A. Mellgren, et al. (2005), Obstet Gynecol Surv 60(11): 753-60.
Abstract: Although the etiology of rectocele remains debated, surgical innovations are currently promoted to improve anatomic outcome while avoiding dyspareunia and alleviating rectal emptying difficulties following rectocele surgery. Use of biomaterials in rectocele repair has become widespread in a short time, but the clinical documentation of their effectiveness and complications is limited. Medline and the Cochrane database were searched electronically from 1964 to May 2005 using the Pubmed and Ovid search engines. All English language publications including any of the search terms "rectocele," "implant," "mesh," "biomaterial," "prolapse," "synthetical," "pelvic floor," "biological," and "compatibility" were reviewed. This review outlines the basic principles for use of biomaterials in pelvic reconstructive surgery and provides a condensation of peer-reviewed articles describing clinical use of biomaterials in rectocele surgery. Historical and new concepts in rectocele surgery are discussed. Factors of importance for human in vivo biomaterial compatibility are presented together with current knowledge from clinical studies. Potential risks and problems associated with the use of biomaterials in rectocele and pelvic reconstructive surgery in general are described. Although use of biomaterials in rectocele and other pelvic organ prolapse surgery offers exciting possibilities, it raises treatment costs and may be associated with unknown and potentially severe complications at short and long term. Clinical benefits are currently unknown and need to be proven in clinical studies. Target Audience: Obstetricians & Gynecologists, Family Physicians Target Audience: After completion of this article, the reader should be able to explain that the objective of surgical treatment is to improve anatomic outcome and alleviate rectal emptying difficulties, describe the efficacy of biomaterials in rectocele repair, and summarize the potential risks and problems associated with use of biomaterials in rectocele and pelvic reconstructive surgery.
| Redox and redox-coupled processes of heme proteins and enzymes at electrochemical interfaces
Murgida, D. H. and P. Hildebrandt (2005), Phys Chem Chem Phys 7(22): 3773-84.
Abstract: Modern bioelectrochemical methods rely upon the immobilisation of redox proteins and enzymes on electrodes coated with biocompatible materials to prevent denaturation. However, even when protein denaturation is effectively avoided, heterogeneous protein electron transfer is often coupled to non-Faradaic processes like reorientation, conformational transitions or acid-base equilibria. Disentangling these processes requires methods capable of probing simultaneously the structure and reaction dynamics of the adsorbed species. Here we provide an overview of the recent developments in Raman and infrared surface-enhanced spectroelectrochemical techniques applied to the study of soluble and membrane bound redox heme proteins and enzymes. Possible biological implications of the findings are critically discussed.
| Reduced platelet adhesion to titanium metal coated with apatite, albumin-apatite composite or laminin-apatite composite
Uchida, M., A. Ito, et al. (2005), Biomaterials 26(34): 6924-31.
Abstract: Titanium metal coated with apatite (HA-Ti), albumin-apatite composite (AA-Ti) or laminin-apatite composite (LA-Ti) was prepared by the immersion of NaOH- and heat-treated titanium metal in a calcium phosphate solution, or one supplemented with albumin or laminin. Platelet adhesion to the obtained materials under flow conditions was investigated in real time using a cone- and plate-type viscometer and fluorescence labeled platelets. Adhesion and activation of the platelets on the HA-Ti, AA-Ti and LA-Ti were definitely suppressed as compared with those on untreated titanium metal with a mirror surface. Furthermore, the numbers of platelets adhered to AA-Ti and LA-Ti are smaller than those adhered to HA-Ti, although the differences were not statistically significant. These findings suggest that HA-Ti, AA-Ti and LA-Ti, especially AA-Ti and LA-Ti, would exhibit thromboresistance that is superior to commercially pure titanium metal in terms of platelet adhesion.
| Reduced T cell response to beta-lactoglobulin by conjugation with acidic oligosaccharides
Yoshida, T., Y. Sasahara, et al. (2005), J Agric Food Chem 53(17): 6851-7.
Abstract: We have previously reported that the conjugation of beta-lactoglobulin (beta-LG) with alginic acid oligosaccharide (ALGO) and phosphoryl oligosaccharides reduced the immunogenicity of beta-LG. In addition, those conjugates showed higher thermal stability and improved emulsifying properties than those of native beta-LG. We examine in this study the effect of conjugation on the T cell response. Our results demonstrate that the T cell response was reduced when mice were immunized with the conjugates. The findings obtained from an experiment using overlapping synthetic peptides show that novel epitopes were not generated by conjugation. One of the mechanisms for the reduced T cell response to the conjugates was found to be the reduced susceptibility of the conjugates to processing enzymes for antigen presentation. We further clarify that the beta-LG-ALGO conjugate modulated the immune response to Th1 dominance. We consider that this property of the beta-LG-ALGO conjugate would be effective for preventing food allergy as well as by its reduced immunogenicity. Our observations indicate that the method used in this study could be applied to various protein allergens to achieve reduced allergenicity with multiple improvements in their properties.
| Reduction in complement activation from biomaterials by removal of air nuclei from the surface roughness
Ward, C. A., A. Koheil, et al. (1984), J Biomed Mater Res 18(3): 255-69.
Abstract: The activation of the rabbit complement system by each of three different synthetic materials is reported. Samples of each type of material were subjected to one of two different priming procedures. One priming procedure was intended to remove the air nuclei from the surface roughness of the materials; the other procedure was just the normal one. It was found that the removal of the air nuclei during priming reduced the complement activation by each of the two materials of lower surface tension, but not by a statistically significant amount for the material of highest surface tension, cellophane. For the denucleated samples of the three materials, the amount of complement activation was found to correlate with the critical surface tension of the materials; if the samples of the materials were normally primed, there was no correlation of the amount of complement activation with the critical surface tension of the material.
| Reduction in platelet adhesion to biomaterials by removal of gas nuclei
Ward, C. A., B. Ruegsegger, et al. (1974), Trans Am Soc Artif Intern Organs 20A: 77-84.
| Reduction of vascular intimal-medial hyperplasia in polytetrafluoroethylene arteriovenous grafts via expression of an inhibitor of G protein signaling
Fields, R. C., K. Baig, et al. (2005), Ann Vasc Surg 19(5): 712-8.
Abstract: Polytetrafluoroethylene (PTFE) arteriovenous (AV) grafts are performed routinely for vascular access. The limited life span of PTFE grafts is a major cause of morbidity. Graft failure is attributed to venous outflow tract vascular smooth muscle (VSM) hyperplasia, which is linked to heterotrimeric G protein signaling. We proposed that expression of a peptide inhibitor of G(betagamma) signaling (betaARKct) in the venous outflow of PTFE grafts would reduce hyperplasia and prolong graft patency. Left carotid to right external jugular vein PTFE AV grafts were placed in swine. The isolated external jugular vein was treated with an adenovirus encoding betaARKct, empty adenovirus, or phosphate-buffered saline for approximately 25 min. After 7 or 28 days, flow probe analysis was performed and the vein was harvested and analyzed for cross-sectional area comparison. After both 7 and 28 days, when compared to controls, treated animals demonstrated a statistically significant reduction in VSM hyperplasia with a reduction in cross-sectional intimal and medial areas of >40% (p < 0.05). Flow was maintained in treated grafts, while control groups demonstrated a >50% reduction (p < 0.05) at 7 days. Further, treated grafts demonstrated significant improvement in graft patency at 28 days (100% vs. 12% for treated and untreated grafts, respectively). The inhibition of G(betagamma) signaling reduces intimal-medial hyperplasia and prolongs graft patency in PTFE AV grafts. This represents a novel molecular therapeutic strategy for improving the patency of vascular access grafts.
| Re-Engineering the liver with natural biomaterials
Gupta, S., H. Malhi, et al. (2000), Yonsei Med J 41(6): 814-24.
Abstract: The extensive regenerative capacity of hepatocytes and the key roles of the liver in metabolic processes have generated interest in the liver as an appropriate target for cell and gene therapy. If cells were considered as natural biomaterials, then liver cell transplantation would fall within the general field of bioengineering. While unmodified hepatocytes engraft in the liver and ectopic sites, biological modifications and optimization of bioengineered systems would facilitate engraftment and survival of transplanted cells, especially in ectopic locations. Acute liver failure, chronic liver disease and metabolic deficiency states are among the conditions that can potentially be treated by cell transplantation. In acute liver failure, cell transplantation into the liver, along with the creation of an extrahepatic reservoir of cells might be required because engraftment and proliferation of transplanted cells in the liver needs time. In other situations, gradual liver repopulation alone might well be effective without additional manipulations.
| Regenerating the periodontium: is there a magic formula?
Foster, B. L. and M. J. Somerman (2005), Orthod Craniofac Res 8(4): 285-91.
Abstract: OBJECTIVE: Left untreated, periodontal disease results in destruction of periodontal tissues including cementum, bone and the periodontal ligament, and subsequently, tooth loss. Increased research efforts focused on understanding periodontal disease at the cellular, molecular and clinical level have resulted in improved modalities for arresting disease progression; however, outcomes of existing procedures are not predictable and often disappointing. Critical to improving the predictability of regenerative therapies is targeting studies toward enhancing our understanding of the cellular and molecular events required to restore periodontal tissues. DESIGN: Toward this goal our laboratory has focused on defining cells, mechanisms and factors regulating development of periodontal tissues, using in vitro and in vivo rodent models. RESULTS AND CONCLUSION: Results from these studies have enabled us to identify attractive candidate factors/cells including: 1) products secreted by epithelial cells that act on mesenchymal cells (amelogenins): we observed that both follicle cells and cementoblasts are responsive to amelogenin-like molecules resulting in changes in the expression of genes associated with cell maturation; 2) morphogens (bone morphogenetic proteins, BMP): we report that follicle cells respond differently to BMPs vs. cementoblasts, depending on dose of and specific BMP used; 3) phosphates: existing data suggest that phosphates act as signaling molecules regulating the expression of genes associated with cementoblast maturation. Knowledge gained from these studies has provided insight as to the cells/factors required for designing improved regenerative therapies.
| Regeneration of articular cartilage
Kinner, B., R. M. Capito, et al. (2005), Adv Biochem Eng Biotechnol 94: 91-123.
Abstract: Loss of articular cartilage from the ends of bones forming diarthrodial joints can be the source of profound pain and disability, and eventually lead to complete degeneration of the joint, necessitating total joint replacement. Until a few years ago, there seemed little hope of treating such defects. Novel surgical procedures and cell therapies have recently been found, however, to stimulate the formation of reparative tissue resulting in the relief of pain and restoration of function, at least for a limited time period. Moreover, studies of the healing of chondral defects in animal models have revealed that there is some potential for regeneration of this connective tissue. The introduction of certain biomaterial scaffolds along with selected surgical procedures and cell therapies has been demonstrated in animal studies to facilitate the cartilage reparative process and now offers the promise of extending the longevity of clinical treatments of cartilage defects. Collectively these findings provide the basis for the rational development of approaches for the more complete regeneration of articular cartilage, and demonstrate that meaningful clinical outcomes can be achieved even if complete regeneration is not achieved.
| Regenerative biology and medicine
Stocum, D. L. (2002), J Musculoskelet Neuronal Interact 2(3): 270-3.
Abstract: The replacement of damaged tissues and organs with tissue and organ transplants or bionic implants has serious drawbacks. There is now emerging a new approach to tissue and organ replacement, regenerative biology and medicine. Regenerative biology seeks to understand the cellular and molecular differences between regenerating and non-regenerating tissues. Regenerative medicine seeks to apply this understanding to restore tissue structure and function in damaged, non-regenerating tissues. Regeneration is accomplished by three mechanisms, each of which uses or produces a different kind of regeneration-competent cell. Compensatory hyperplasia is regeneration by the proliferation of cells which maintain all or most of their differentiated functions (e.g., liver). The urodele amphibians regenerate a variety of tissues by the dedifferentiation of mature cells to produce progenitor cells capable of division. Many tissues contain reserve stem or progenitor cells that are activated by injury to restore the tissue while simultaneously renewing themselves. All regeneration-competent cells have two features in common. First, they are not terminally differentiated and can re-enter the cell cycle in response to signals in the injury environment. Second, their activation is invariably accompanied by the dissolution of the extracellular matrix (ECM) surrounding the cells, suggesting that the ECM is an important regulator of their state of differentiation. Regenerative medicine uses three approaches. First is the transplantation of cells into the damaged area. Second is the construction of bioartificial tissues by seeding cells into a biodegradable scaffold where they produce a normal matrix. Third is the use of a biomaterial scaffold or drug delivery system to stimulate regeneration in vivo from regeneration-competent cells. There is substantial evidence that non-regenerating mammalian tissues harbor regeneration-competent cells that are forced into a pathway of scar tissue formation. Regeneration can be induced if the factors leading to scar formation are inhibited and the appropriate signaling environment is supplied. An overview of regenerative mechanisms, approaches of regenerative medicine, research directions, and research issues will be given.
| Regulation of cell adhesion using a signal-responsive membrane substrate
Okajima, S., T. Yamaguchi, et al. (2005), Biotechnol Bioeng 91(2): 237-43.
Abstract: We have developed a novel cell culture material that regulates cell adhesion by changes in potassium ion concentration. The material is a polyethylene substrate grafted to a copolymer of the thermoresponsive polymer N-isopropylacrylamide (NIPAM) and benzo-18-crown- 6-acrylamide (BCAm), with a pendant crown ether as sensor. The crown ether recognizes potassium ion concentrations and NIPAM conformational changes lead to changes in the hydrophobicity/hydrophilicity balance of the entire polymer at constant cell culture temperatures. Although cells were successfully cultured on the ion recognition material in normal culture medium at 37 degrees C, the cells could be detached from the material surface by adding potassium ions alone, without proteolytic enzymes, because the surface to which the cells were attached altered its surface characteristics to a more hydrophilic state. Therefore, cell layers with intact cell-to-cell junctions and high activities were successfully recovered. Furthermore, by changing the target sensors, this material will be able to control cell adhesion through various cellular signals.
| Regulation of mouse follicle development by follicle-stimulating hormone in a three-dimensional in vitro culture system is dependent on follicle stage and dose
Kreeger, P. K., N. N. Fernandes, et al. (2005), Biol Reprod 73(5): 942-50.
Abstract: The developmental requirements of ovarian follicles are dependent on the maturation stage of the follicle; in particular, elegant studies with genetic models have indicated that FSH is required for antral, but not preantral, follicle growth and maturation. To elucidate further the role of FSH and other regulatory molecules in preantral follicle development, in vitro culture systems are needed. We employed a biomaterials-based approach to follicle culture, in which follicles were encapsulated within matrices that were tailored to the specific developmental needs of the follicle. This three-dimensional system was used to examine the impact of increasing doses of FSH on follicle development for two-layered secondary (100-130 microm; two layers of granulosa cells surrounding the oocyte) and multilayered secondary (150-180 microm, several layers of granulosa cells surrounding the oocyte) follicles isolated from mice. Two-layered secondary follicles were FSH responsive when cultured in alginate-collagen I matrices, exhibiting FSH dose-dependent increases in follicle growth, lactate production, and steroid secretion. Multilayered secondary follicles were FSH dependent, with follicle survival, growth, steroid secretion, metabolism, and oocyte maturation all regulated by FSH. However, doses greater than 25 mIU/ml of FSH negatively impacted multilayered secondary follicle development (reduced follicle survival). The present results indicate that the hormonal and environmental needs of the follicular complex change during the maturation process. The culture system can be adapted to each stage of development, which will be especially critical for translation to human follicles that have a longer developmental period.
| Regulatory and biomaterials investigations
Phillips, R. W. (1990), J Oral Implantol 16(4): 255-6.
| Regulatory concerns in the development of biologic-biomaterial combinations.United States Food and Drug Administration
Chapekar, M. S. (1996), J Biomed Mater Res 33(3): 199-203.
Abstract: Several biologic-biomaterial combinations are currently under development in an attempt to modulate tissue or organ function in patients. The FDA regulations on combination products and the intercenter agreements among the Center for Biologics Evaluation and Research (CBER), the Center for Devices and Radiological Health (CDRH), and the Center for Drugs Evaluation and Research (CDER) provide further guidance on center jurisdiction of combination products and other products where there are jurisdictional concerns. The biological component of biologic-biomaterial combinations raises a number of issues that relate to the safety and bioactivity of the final product. For example, transmission of adventitious agents to patients via somatic cells, tissue, or cell-derived products is a major safety concern as are in vivo inflammatory responses elicited by the biomaterial component. CBER has drafted a number of "Points to Consider" documents to provide further guidance in the development of biological products. The intent of this article is to provide the highlights of the FDA regulations for combination products and the intercenter agreement between CBER and CDRH delineating the responsibilities of each center for medical device activities. In addition, the article focuses on the CBER's concerns related to the development of somatic cell-biomaterial combinations for therapeutic use.
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