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Record 4121 to 4140

The issue of bioresorption of the Bio-Oss xenogeneic bone substitute in bone defects
Duda, M. and J. Pajak (2004), Ann Univ Mariae Curie Sklodowska [Med] 59(1): 269-77.
Abstract: Bone grafts and bone substitute biomaterial implemented in guided tissue regeneration should undergo the process of biological decomposition in the recipient's system. The aim of this work is the presentation of current views concerning the issue of Bio-Oss bovine bone bioresorption and their juxtaposition with the results of the author's own research. The work presents histopathological and immunohistochemical tests of the xenogeneic Bio-Oss preparation from biopsies carried out 30 months after implantation. It was observed that the preparations contained correct bone neighbouring remnant particles of Bio-Oss, intratrabecular fibromatosis around the implant, abundant vascularisation, absence of osteoid and of active inflammatory process. A small number of T and B lymphocytes was detected. The results obtained in the above-described case testify to the descending character of the inflammatory infiltration 30 months after the implementation of Bio-Oss and efficient restoration of the bone. The prevalent view in literature is that Bio-Oss is resorbable biomaterial. However, there are also reports questioning this view as remnants of Bio-Oss have been detected even 44 months after implantation into the bone defect. In the author's own cases, Bio-Oss remnants could be observed 30 months after implanting. It seems that although the creation of new bone structure is indisputable, the process of biological decomposition of Bio-Oss should be described as slow bioresorption.

The materials specialists education and features of biomaterials study and analysis
Arsenjev, P. A., N. V. Komissarenko, et al. (1997), Biomed Sci Instrum 33: 281-5.
Abstract: The work considers some questions of the biomaterials specialists education. The problem of the specialists education in the field of a biomedical material science is not finally solved till now, because of the complexity and variety of necessary knowledge. The main question is what base education is the best for the biomaterial specialists? This work represents the standpoint of scientific school, realizing the educational process based on an electronic engineering material science.

The measurement temperature: an important factor relating physicochemical and adhesive properties of yeast cells to biomaterials
Gallardo-Moreno, A. M., M. L. Gonzalez-Martin, et al. (2004), J Colloid Interface Sci 271(2): 351-8.
Abstract: Flow chambers applied to the study of the initial adhesion process of Candida parapsilosis are rarely found in the literature. The ability of these microorganisms to proliferate and form biofilms in environments at temperatures around 22 or 37 degrees C is reflected in the contamination of laboratory instruments and material or in human implant infections, respectively. The initial interaction between yeasts and substrata is mediated by physicochemical forces, which in turn originate from the physicochemical surface properties of both interacting phases. In this context, this work aims to relate the initial rates of adhesion rates to glass and silicone of Candida parapsilosis, strains 294 and 289, grown at 22 and 37 degrees C with the theoretical predictions of the adhesion process, expressed by the interaction free energies and calculated through the physicochemical parameters, which are also measured at 22 and 37 degrees C. The results indicate that physicochemical parameters of yeasts are changed not only by the culture temperature but also by the measurement temperature; only when the measurement temperature is equal to the growth temperature a coherent relation between in vitro adhesion data and interaction free energies can be established. In this sense, the adhesion to glass is mediated by long-range forces or, what amounts to the same thing, by Lifshitz-van der Waals interaction free energy. On the other hand, the adhesion to silicone rubber seems to be moderated by acid-base interaction free energy, which involves the presence of short-range forces. Based on these results, it can be assumed that the substratum surface properties are directly related to the kind of force acting on the initial microbial adhesion process, while cell surface properties dictate the changes in the strength of the force between different samples.

The mechanical test method of cardiovascular and related biomaterials
Yokobori, A. T., Jr. and T. Yokobori (1991), Biomed Mater Eng 1(1): 25-43.
Abstract: Mechanical testing methods were developed by us using the pulsatile internal pressure through-flow system. The methods were applied to estimate the permeability and fatigue strength of a vascular substitute, the mechanical behaviour of anastomosed site between vascular substitute and blood vessel, and the mechanical behaviour of the blood vessel itself. A testing method is also proposed for puncturing a vascular substitute which is used as blood access for hemodialysis. The mechanical behaviour of punctured vascular substitute and the puncturing technique itself are investigated. The fatigue-creep testing method of cellophane membrane is also reported to estimate the durability of cellophane membrane by using the circulating pulsatile internal pressure through-flow system. The mechanical testing method for visco-elastic characteristic of biomaterials is discussed.

The mechanism of surface-indented protein-loaded PLGA microparticle formation: the effects of salt (NaCl) on the solidification process
Chen, J. L., M. K. Yeh, et al. (2004), J Microencapsul 21(8): 877-88.
Abstract: The purpose of this study was to evaluate ovalbumin (OVA) leakage pathways and to explore the mechanism of the surface-indented microparticle formation in the preparation of OVA-loaded microparticles. OVA-loaded poly (D,L-lactic-co-glycolic acid) (PLGA) microparticles were prepared by a water-in oil-in water (w/o/w) solvent evaporation method associated with varied NaCl (NaCl) concentrations and adjusted with urea at 1240mOsm kg(-1) in the external aqueous phase. To evaluate dichloromethane (DCM)-related OVA leakage, three stirring rates, 600, 800, 1000rpm at 25 degrees C were carried out during the solvent evaporation stage. Both DCM and OVA levels in the external phase medium and total dispersion were sampled and measured. The time course of particle characteristics was evaluated by microscopy or SEM photography. The surface adsorptive capacities of the prepared microparticles were measured by using bovine serum albumin conjugated with fluorescein isothiocyanate (FITC-BSA). The findings were that the DCM-related OVA leakage accounted for approximately 34%, of the total leakage. By combining NaCl in the external phase, a faster solidifying crust-like structure was formed as a barrier to remarkably reduce OVA loss and improve OVA content from 40.1 to 72.8 microg mg(-1). The yield and OVA content for formulations containing NaCl were much improved by the ionic effect, in addition to the osmotic effect. The total entrapment efficiency was also highly increased from 43 to 72%. The formations of the crust-like surface structure of the microparticle were affected by entrapped drugs, salt content in the external phase and aqueous volume in the inner phase. A scheme was proposed to interpret the formation mechanism of the surface-indented microparticles. In comparison to the surface-smooth microparticles, the surface adsorptive capacities of the surface-indented microparticles were highly improved from 26.6 to 87.0%, determined by the adsorption of FITC-BSA.

The micro patterning of glutaraldehyde (GA)-crosslinked gelatin and its application to cell-culture
Yang, L. J. and Y. C. Ou (2005), Lab Chip 5(9): 979-84.
Abstract: This paper proposes a novel technique for fabricating micro patterns of glutaraldehyde (GA)-crosslinked gelatin. It provides another means to crosslink gelatin other than using photo-sensitizing agents, and the micro patterns of GA-crosslinked gelatin can still be made successfully by accessing conventional photolithography. A much less toxic and increased biocompatible approach to strengthening the gelatin microstructures can be developed according to this idea. This paper also describes a potential methodology for using GA-crosslinked gelatin patterns as single-cell culture bases. The best spatial resolution of the micro gelatin bases can reach 10 microm, and the selective growing density of human Mesenchymal stem cells on the gelatin patterns surpasses the density on the glass substrate by 2-3 orders of magnitude.

The miscibility of poly(D,L-lactide-co-glycolide) with amphiphilic molecules and the interaction of their mixtures with DNA at air/water interface
Sun, L., M. Xu, et al. (2005), Colloids Surf B Biointerfaces 43(1): 29-35.
Abstract: The miscibility of poly(D,L-lactide-co-glycolide) (PLG) with three amphiphilic molecules and the interaction of the PLG/surfactant mixtures with DNA at air/water interface are investigated by pi-A isotherms, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) techniques. The pi-A isotherms of the PLG mixtures with cationic C(12)AzoC(6)PyBr, and C(12)AzoC(6)N(CH(3))(3)Br, are quite different from the pi-A isotherm of pure PLG on water subphase. In contrast to the case, the pi-A isotherm of PLG mixed with nonionic C(12)AzoC(6)OPy is almost identical to the pure PLG except some increasing of molecular area. Similar phenomena are observed on DNA subphase. The in situ BAM and ex situ AFM observations demonstrate that the dispersion of PLG at air/water interface becomes good when it mixes with the two cationic surfactants, whereas quite poor due to the phase separation when it mixes with the nonionic amphiphilic molecule. Based on these results we conclude that the cationic surfactants can affect the conformation change of PLG at air/water interface and figure a well miscibility with polymer whereas the nonionic amphiphilic molecule presents poor miscibility. In addition, the even mixing of the PLG and the cationic surfactants is favorable for the adsorption to DNA more effectively.

The need for standards in an emerging discipline: clinical retrieval and analysis of surgical implants and biomaterials
Daniels, A. U. (1988), J Biomed Mater Res 22(A2 Suppl): 113-7.

The nine residue plasminogen-binding motif of the pneumococcal enolase is the major cofactor of plasmin-mediated degradation of extracellular matrix, dissolution of fibrin and transmigration
Bergmann, S., M. Rohde, et al. (2005), Thromb Haemost 94(2): 304-11.
Abstract: The glycolytic enzyme alpha-enolase represents one of the nonclassical cell surface plasminogen-binding proteins of Streptococcus pneumoniae. In this study we investigated the impact of an internal plasminogen-binding motif of enolase on degradation of extracellular matrix and pneumococcal transmigration. In the presence of host-derived plasminogen activators (PA) tissue-type PA or urokinase PA and plasminogen S. pneumoniae expressing wild-type enolase efficiently degraded Matrigel or extracellular matrix (ECM). In contrast, amino acid substitutions in the nine residue plasminogen-binding motif of enolase significantly reduced degradation of ECM or Matrigel by mutated pneumococci. Similarly, recombinant wild-type enolase but not a mutated enolase derivative that lacks plasminogen-binding activity efficiently degraded ECM and Matrigel, respectively. In particular, bacterial cell enolase-bound plasmin potentiated dissolution of fibrin or laminin and transmigration of pneumococci through a fibrin matrix. In conclusion, these results provide evidence that the enolase is the major plasminogen-binding protein of pneumococci and that the nine residue plasminogen-binding motif of enolase is the key cofactor for plasmin-mediated pneumococcal degradation and transmigration through host ECM.

The ovariectomised sheep as a model for testing biomaterials and prosthetic devices in osteopenic bone: a preliminary study on iliac crest biopsies
Fini, M., G. Pierini, et al. (2000), Int J Artif Organs 23(4): 275-81.
Abstract: A histomorphometric and ultrastructural evaluation on sheep iliac bone was performed. Six sheep were ovariectomised (OVX Group) and 6 were left intact (Sham-aged, Control Group). An iliac crest biopsy was performed randomly in 6 animals at the beginning of the study, then, in all the animals, after 12 and 24 months. A significant decrease in trabecular bone volume, trabecular thickness (p<0.0005) and cell volume (p<0.005) was observed in OVX animals. A modest decrease in trabecular number and osteoid thickness together with an increase in trabecular separation were observed in OVX animals at 12 and 24 months. The osteoid volume showed a significant difference (p<0.05) between the groups. In OVX animals, at 12 months, Scanning Electron Microscopy revealed an enlargement of the trabecular space and a progressive replacement of bone matrix with adipose tissue. These signs were accentuated at 24 months. In conclusion, OVX sheep showed a loss of trabecular bone starting at 12 months after ovariectomy. The developed osteopenic state may be considered as a useful tool when doing research on biomaterial osteointegration.

The ovariectomized ewe model in the evaluation of biomaterials for prosthetic devices in spinal fixation
Giavaresi, G., M. Fini, et al. (2001), Int J Artif Organs 24(11): 814-20.
Abstract: The effect of surgical ovariectomy on cancellous bone was investigated by comparing mechanical properties and microarchitectural characteristics of the lumbar vertebrae in ovariectomized and sham-operated ewes. Eighteen mongrel ewes, 4+/-1 years old, were randomly divided into three groups: 6 animals served as a control group (Baseline), 6 were bilaterally ovariectomized (OVX), and the others were used as a sham-operated group (SHAM). OVX and SHAM ewes were euthanized 24 months after surgery; the L5 vertebrae were processed for mechanical and histomorphometric analyses. Maximum load, maximum strength (p<0.0005) and elastic modulus (p <0.005) decreased by about 28% in the OVX group in comparison with the other groups. In the OVX group, vertebral cancellous bone volume, trabecular thickness and trabecular number decreased by about 32% (p<0.0005), 15% (p=0.001) and 20% (p=0.019), respectively. An overall decrease in the bone turnover rate of the OVX group was registered in terms of bone formation rate (p=0.007) and activation frequency (p<0.0005). The variations observed in cancellous bone mechanics and histomorphometry would suggest the development of an osteopenic state in ewe vertebrae at 24 months. Such findings may be useful for future experimental investigations on biomaterials and prosthetic devices to be implanted in the osteopenic spine.

The participation of P- and E-selectins on biomaterial-mediated tissue responses
Tang, L., W. Jiang, et al. (2002), J Biomed Mater Res 62(4): 471-7.
Abstract: Biomaterial-mediated inflammatory responses often compromise the functions of implantable devices. The mechanism(s) involved in the inflammatory responses, which can be arbitrarily divided into phagocyte transmigration, chemotaxis, and adhesion to implant surfaces, are not totally understood. Because adhesion molecules have been shown to involved in phagocyte transmigration, this study was designed to investigate the participation of endothelial adhesion molecules in the pathogenesis of biomaterial-mediated inflammatory responses and fibrotic tissue formation. Using transgenic adhesion molecule knockout mice, we found that (1) deficiency of P-selectin reduced polymorphonuclear neutrophils (PMN) but not macrophages/monocytes (Mphi) transmigration and adhesion. (2) Furthermore, absence of both P- and E-selectin (P/E-deficient) dramatically diminished both PMN and Mphi recruitment to the peritoneal cavity and accumulation on implanted biomaterials. (3) Finally, the impairment of inflammatory responses in P/E-deficient mice significantly reduced the extent of subsequent biomaterial-mediated fibrotic responses. We conclude that P- and E-selectins are important for both biomaterial-mediated inflammatory and fibrotic reactions. Our results also indicate that the reduction of phagocyte accumulation might be responsible to the decrease of fibrotic tissue formation surrounding material implants. Better understanding of such sequence of events may help the rational design of biomaterials with desired tissue reactivity.

The parting of the ways? How biomaterials may differ from advanced materials in the next century
Williams, D. (1999), Med Device Technol 10(4): 8-11.
Abstract: A recent symposium on the future role of materials science in some critical industries suggests that the historical reliance of the medical device industry on the advances made in conventional materials development may not be sustained in the next few decades.

The pathology of breast biopsy site marking devices
Guarda, L. A. and T. A. Tran (2005), Am J Surg Pathol 29(6): 814-9.
Abstract: This report presents our experience with 54 cases of patients who had excision of breast lesions after deployment of radiographic biopsy site markers at the time of stereotactic biopsy. These were of two types: pellets of a resorbable copolymer of polylactic acid/polyglycolic acid (31 cases) and plugs of bovine collagen (23 cases), both containing embedded metallic clips for long-term radiographic marking. On gross examination, the pellets have a characteristic appearance similar to a soft grain of rice, whereas the collagen plugs are spongiform with variable hemorrhagic changes. Microscopically, there are distinct differences in the morphologic features of these two types of biopsy site markers and the associated tissue reactions. With the pellets, there is an initial cell-poor fibrotic reaction around empty spaces followed by a multinucleate giant cell reaction and penetration of the marker core by eosinophilic fibrinous material. The collagen plugs are recognized as eosinophilic, hyalinized, acellular material, accompanied by an inflammatory infiltrate composed predominantly of lymphocytes, plasma cells, eosinophils and, occasionally, neutrophils, which penetrate the core of the marker with time. The degradation of the collagen plug appears to be associated with infiltration of the marker by fibrovascular tissue and deposition of native collagen; of note is the absence of a significant multinucleate giant cell reaction. These novel breast biopsy site markers do not interfere with the histologic processing of the tissue or with their histopathologic interpretation.

The physical properties and response of osteoblasts to solution cast films of PLGA doped polycaprolactone
Tang, Z. G., J. T. Callaghan, et al. (2005), Biomaterials 26(33): 6618-24.
Abstract: Polycaprolactone films doped with poly(lactide-co-glycolide) (65:35) in 0, 10, 20, and 30 (wt%) were prepared and evaluated in terms of morphology, dynamic contact angle analysis, and thermal properties. The unique surface morphology of the doped PCL film resulted, without introducing significant microstructure disruption of PCL aggregation. The doped PCL film registered a lower contact angle and increased hydrophilicity. Osteoblast cells attached to all doped materials, the 10% and 20% doped materials demonstrating the greatest cell growth.

The polyurethane foam covering the Meme breast prosthesis: a biomedical breakthrough or a biomaterial tar baby?
Guidoin, R., M. Therrien, et al. (1992), Ann Plast Surg 28(4): 342-53.
Abstract: Because controversy continues to surround the implantation of the polyurethane foam-covered Meme breast prosthesis, in vitro experiments were conducted to determine: (1) whether the polyurethane foam contains extractable toluene diamine isomers (TDAs), and (2) whether the polyurethane foam releases TDAs on exposure to mild hydrolytic conditions. Results confirmed the presence of extractable TDAs and other impurities in the foam covering the unused Meme prosthesis, and that the concentrations of these impurities could be significantly reduced by washing the foam in a regular detergent. This washing step was omitted from the manufacturer's production process. Furthermore, on exposure to mild alkalis, the foam exhibited significant degradation, rapid fragmentation, loss of mechanical strength and physical integrity, as well as the release of additional TDAs. Because of the potential long-term risks associated with the release of TDAs in vivo, continued clinical use of the Meme prosthesis containing this particular type of foam appears questionable.

The potential for poly-alpha-amino acids as biomaterials
Anderson, J. M., D. F. Gibbons, et al. (1974), J Biomed Mater Res 8(3): 197-207.

The potential of chitosan for the oral administration of peptides
Prego, C., D. Torres, et al. (2005), Expert Opin Drug Deliv 2(5): 843-54.
Abstract: Over recent years, a major challenge in drug delivery has been the design of appropriate vehicles for the oral administration of macromolecular drugs (peptides and proteins). Indeed, despite the increasing market value of these complex molecules, their clinical use has been highly limited by their reduced oral bioavailability. Among the different delivery approaches explored so far, those based on the use of the polysaccharide chitosan have opened promising alternatives towards this ambitious goal. This is due to the interesting physicochemical and biopharmaceutical properties of this polymer. This article describes the advances that have been made in the design of chitosan-based systems specially adapted for the oral administration of peptides. These systems include solutions, microspheres, nanoparticles, nanocapsules and liposomes. More specifically, this article discusses the efficacy of the different delivery approaches for improving the absorption of peptides, and analyses the various mechanisms that have been proposed for the understanding of their efficacy.

The powers of self-assembly
Williams, D. (2004), Med Device Technol 15(9): 11-3.
Abstract: During the past few years, new concepts of materials synthesis have been developed in which macromolecular structures form by-processes of self-assembly. Microstructures and nanostructures, which often mimic those found in nature, are formed without complex manufacturing methods. This article assesses the implications of this development for medical devices.

The preparation of insoluble fibroin films induced by degummed fibroin or fibroin microspheres
Lv, Q., C. Cao, et al. (2004), J Mater Sci Mater Med 15(11): 1193-7.
Abstract: Blending degummed fibroin (DF) or insoluble fibroin microspheres with concentrated fibroin solution, the insoluble films were obtained through drying the solution at 40-45 degrees C. The conformation of silk fibroin films was analyzed by infrared spectrum and X-ray diffractometry. The results demonstrated that beta-sheet conformation increased rapidly when the degummed silk or insoluble microspheres blended with fibroin, while the pure SF membrane was mainly composed of alpha/random coil conformation when the other conditions kept same. This suggested that fibroin microspheres and degummed fibroin could induce the formation of beta-sheet crystal and the insoluble films, without methanol after-treatment, could be obtained at approximately room temperature. Although the fibroin films blending with DF had many protuberances, the films containing fibroin microspheres had the smooth surface and could be used effectively in biotechnological materials and biomedical application.

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