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Record 4141 to 4160

The preparation of Zn2+-doped TiO(2) nanoparticles by sol-gel and solid phase reaction methods respectively and their photocatalytic activities
Liu, G., X. Zhang, et al. (2005), Chemosphere 59(9): 1367-71.
Abstract: The photocatalytic oxidation of the organic pollutants with TiO(2) as photocatalyst has been widely studied in the world, and many achievements have been made. The degradation of pollutants is highly related to the photocatalytic activity of TiO(2). It is demonstrated that doping ions to TiO(2) is one way to enhance the photocatalytic activity of TiO(2). In this paper, Zn(2+)-doped TiO(2) nanoparticles were prepared through sol-gel and solid phase reaction methods, characterized by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of the elaborated powders was studied following the degradation of Rhodamine B. The results showed that the photocatalytic activity of Zn(2+)-doped TiO(2) prepared by sol-gel method is close to that of pure TiO(2) particles, however, the photocatalytic activity of Zn(2+)-doped TiO(2) prepared by solid phase reaction method is much higher than that of pure TiO(2) particles. The most efficient degradation of Rhodamine B was found with TiO(2) particles doped with 0.5% Zn(2+) in mole and calcined at 500 degrees C. Also the reason for the enhancement of the photocatalytic activity of TiO(2) by Zn(2+) doping through solid phase reaction method was discussed.

The present and future of drug-eluting stents
Indolfi, C., A. Mongiardo, et al. (2005), Ital Heart J 6(6): 498-506.
Abstract: The only widely accepted way to reduce restenosis rate after percutaneous balloon angioplasty has been the use of coronary bare metal stents, and the last decade has witnessed a prompt and widespread adoption of bare metal stents that has revolutionized the field of interventional cardiology. The new millennium has seen the recent development of drug-eluting stents (DES), allowing controlled release of a drug directly to the injured artery, which seem to have prevented by large the problem of in-stent restenosis. The goal of this review was to summarize recent laboratory and clinical investigations concerning the effects of DES in various settings relevant to coronary heart disease. In the experimental setting, we examine the intracellular signaling and the role of smooth muscle cells after vascular injury. We also discuss recent observations from our laboratory showing the effects of coating per se on cell apoptosis and proliferation. In the clinical setting, the effects of DES in patients with stable or unstable angina pectoris is examined in detail for the relevant implications both in the treatment and prognosis. The results of a meta-analysis on the effects that have been overlooked in individual studies are reported which show a striking reduction in bypass surgery after DES implantation. Finally, we discuss the potential role of new materials and technologies (i.e., nanotechnology) that will improve DES performance allowing other future clinical applications in patients with ST-elevation myocardial infarction, vulnerable plaques, insulin-dependent diabetes mellitus, etc.

The problems and promise of DNA barcodes for species diagnosis of primate biomaterials
Lorenz, J. G., W. E. Jackson, et al. (2005), Philos Trans R Soc Lond B Biol Sci 360(1462): 1869-77.
Abstract: The Integrated Primate Biomaterials and Information Resource (www.IPBIR.org) provides essential research reagents to the scientific community by establishing, verifying, maintaining, and distributing DNA and RNA derived from primate cell cultures. The IPBIR uses mitochondrial cytochrome c oxidase subunit I sequences to verify the identity of samples for quality control purposes in the accession, cell culture, DNA extraction processes and prior to shipping to end users. As a result, IPBIR is accumulating a database of 'DNA barcodes' for many species of primates. However, this quality control process is complicated by taxon specific patterns of 'universal primer' failure, as well as the amplification or co-amplification of nuclear pseudogenes of mitochondrial origins. To overcome these difficulties, taxon specific primers have been developed, and reverse transcriptase PCR is utilized to exclude these extraneous sequences from amplification. DNA barcoding of primates has applications to conservation and law enforcement. Depositing barcode sequences in a public database, along with primer sequences, trace files and associated quality scores, makes this species identification technique widely accessible. Reference DNA barcode sequences should be derived from, and linked to, specimens of known provenance in web-accessible collections in order to validate this system of molecular diagnostics.

The protective effect of chitin and chitosan against Vibrio alginolyticus in white shrimp Litopenaeus vannamei
Wang, S. H. and J. C. Chen (2005), Fish Shellfish Immunol 19(3): 191-204.
Abstract: White shrimp, Litopenaeus vannamei, which had been injected with chitin at 4, 6 and 8 microg g(-1) or chitosan at 2, 4 and 6 microg g(-1), were challenged with pathogen Vibrio alginolyticus at 2 x 10(6) colony-forming units (cfu) shrimp(-1) and then placed in seawater of 34 per thousand. The survival of shrimp that received chitin or chitosan at either dose was significantly higher than that of control shrimp after 1 day, and at the termination of the experiment (6 days after the challenge). In another experiment, the total haemocyte count (THC), phenoloxidase activity, respiratory burst, superoxide dismutase (SOD) activity, and phagocytic activity to V. alginolyticus were measured when L. vannamei (10.4 +/- 0.7 g) were injected individually with chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1). L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased significantly its THC and respiratory burst after 2 days. L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) still maintained significantly higher phenoloxidase activity after 6 days. L. vannamei received chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased its phagocytic activity against V. alginolyticus after 1 day, respectively. It is therefore concluded that L. vannamei that received chitin at 6 microg g(-1) or chitosan at 4 microg g(-1) or less increased its immune ability and resistance to V. alginolyticus infection.

The quantification of cellular viability and inflammatory response to stainless steel alloys
Bailey, L. O., S. Lippiatt, et al. (2005), Biomaterials 26(26): 5296-302.
Abstract: The biocompatibility of metallic alloys is critical to the success of many orthopedic therapies. Corrosion resistance and the immune response of the body to wear debris products ultimately determine the performance of these devices. The establishment of quantitative tests of biocompatibility is an important issue for biomaterials development. We have developed an in vitro model to measure the pro-inflammatory cytokine production and in this study investigated the cellular responses induced by nitrogenated and 316L stainless steel alloys in both particulate and solid form. We utilized a murine macrophage cell line, RAW 264.7, to characterize and compare the mRNA profiles of TNF-alpha and IL-1beta in these cells using real time-polymerase chain reaction (RT-PCR). Fluorescence microscopy and flow cytometry were used to probe the viability of the population and to examine the apoptotic pathway. The goals of this work were to develop improved measurement methods for the quantification of cellular inflammatory responses to biomaterials and to obtain data that leads to an enhanced understanding of the ways in which the body responds to biomaterials. Using these techniques, we observed evidence for an association between the upregulation of IL-1beta and reversible apoptosis, and the upregulation of TNF-alpha and irreversible apoptosis.

The rabbit ear chamber: a unique in vivo model for the continuous observation of implanted biomaterials
Matlaga, B. F. and T. N. Salthouse (1976), Biomater Med Devices Artif Organs 4(3-4): 359-66.
Abstract: The rabbit ear chamber provides a unique system for viewing an in vivo environment from outside the body. The plastic chamber, modified for our use, is described. Once surgically implanted into the ear of a Laboratory Lop rabbit, a thin tissue bed which grows between the layers of the chamber can be viewed through the microscope. The absorption of biomaterials placed into the chamber can then be observed as a dynamic process.

The reduction half cell in biomaterials corrosion: oxygen diffusion profiles near and cell response to polarized titanium surfaces
Gilbert, J. L., L. Zarka, et al. (1998), J Biomed Mater Res 42(2): 321-30.
Abstract: Mechanically assisted corrosion processes can greatly increase the oxidation currents generated in passivating alloy systems like Co-Cr and titanium due to oxide film disruption. When oxide films are abraded, repassivation and ionic dissolution both occur at rates that are orders of magnitude higher than undisrupted surfaces. The excess electrons generated by these anodic processes must be consumed in corresponding reduction reactions that include the reduction of oxygen. If large enough, these reduction reactions may locally deplete the concentration of solution-dissolved oxygen and, in turn, affect cell behavior in the vicinity of the implant surface. To date, this hypothesis has not been tested. In the present study, a scanning electrochemical microscope was used to measure oxygen concentration profiles in vitro near a planar titanium electrode polarized to different voltages representative of those attainable by titanium undergoing mechanically assisted corrosion. The potentials investigated ranged from 0 mV to -1000 mV (AgCl). The oxygen concentration as a function of distance from the titanium surface was measured using a platinum-iridium microelectrode and an amperometric technique. Also, preliminary experiments were performed to assess the response of rat calvarial osteoblast-rich cells cultured for 2 h on titanium samples polarized to two different potentials (0 mV and -1000 mV versus AgCl). The results of this study indicate that oxygen concentrations near titanium surfaces are affected by sample potentials out to probe-sample distances as great as 500 microm. Within 2 microm of the surface, oxygen concentrations decreased by 15 to 25% for sample potentials between -100 and -500 mV. At potentials more negative than -600 mV, the oxygen concentration dropped rapidly to near zero by -900 mV. The cell experiments showed a statistically significant difference in the amount of cell spreading, as measured by projected cell area, between the two groups (p < 0.03), with the cells cultured at -1000 mV undergoing much less spreading. This implies that -1000 mV inhibits normal cell behavior at the titanium surface and that this is most likely due, at least in part, to a diminished oxygen supply.

The regulation of expanded human nasal chondrocyte re-differentiation capacity by substrate composition and gas plasma surface modification
Woodfield, T. B., S. Miot, et al. (2006), Biomaterials 27(7): 1043-53.
Abstract: Optimizing re-differentiation of clinically relevant cell sources on biomaterial substrates in serum containing (S+) and serum-free (SF) media is a key consideration in scaffold-based articular cartilage repair strategies. We investigated whether the adhesion and post-expansion re-differentiation of human chondrocytes could be regulated by controlled changes in substrate surface chemistry and composition in S+ and SF media following gas plasma (GP) treatment. Expanded human nasal chondrocytes were plated on gas plasma treated (GP+) or untreated (GP-) poly(ethylene glycol)-terephthalate-poly(butylene terephthalate) (PEGT/PBT) block co-polymer films with two compositions (low or high PEG content). Total cellularity, cell morphology and immunofluorescent staining of vitronectin (VN) and fibronectin (FN) integrin receptors were evaluated, while post-expansion chondrogenic phenotype was assessed by collagen types I and II mRNA expression. We observed a direct relationship between cellularity, cell morphology and re-differentiation potential. Substrates supporting high cell adhesion and a spread morphology (i.e. GP+ and low PEG content films), resulted in a significantly greater number of cells expressing alpha(5)beta(1) FN to alpha(V)beta(3) VN integrin receptors, concomitant with reduced collagen type II/ImRNA gene expression. Substrates supporting low cell adhesion and a spherical morphology (GP- and high PEG content films) promoted chondrocyte re-differentiation indicated by high collagen type II/I gene expression and a low percentage of alpha(5)beta(1) FN integrin expressing cells. This study demonstrates that cell-substrate interactions via alpha(5)beta(1) FN integrin mediated receptors negatively impacts expanded human nasal chondrocyte re-differentiation capacity. GP treatment promotes cell adhesion in S+ media but reverses the ability of low PEG content PEGT/PBT substrates to maintain chondrocyte phenotype. We suggest alternative cell immobilization techniques to GP are necessary for clinical application in articular cartilage repair.

The relationship of Periotest values, biomaterial, and torque to failure in adult baboons
Carr, A. B., E. Papazoglou, et al. (1995), Int J Prosthodont 8(1): 15-20.
Abstract: A quantitative measure of implant stability would be beneficial to decision-making regarding the status of the bone anchorage around an implant. The Periotest device has been reported to provide such a measure, but the in vivo data are incomplete and inconclusive in support of this claim. The purpose of this study was to determine in an in vivo model the relationship between Periotest values (PTV), three different implant biomaterials, and torque to failure. A total of 79 screw-shape implants made of commericially pure titanium, titanium alloy, and HA-coated alloy were evaluated in the posterior maxillary and mandibular quadrants of six female baboons following healing for 3 to 4 months. At uncovering, the implants were tested with the Periotest device and torqued to failure using an electronic torque driver. Analysis of the PTV-biomaterial relationship revealed no significant difference among the implants based on the biomaterial (P =.7453). Analysis of PTV-torque revealed a significant relationship (P =.0117), however, the association between PTV and torque was not strong and does not explain 92% of the variation between the parameters (Pearson correlation.2823, R2 =.08).

The response of normal human osteoblasts to anionic polysaccharide polyelectrolyte complexes
Nagahata, M., R. Nakaoka, et al. (2005), Biomaterials 26(25): 5138-44.
Abstract: Polyelectrolyte complexes (PEC) were prepared from chitosan as the polycation and several synthesized functional anion polysaccharides, and their effects on cell attachment, morphology, proliferation and differentiation were estimated using normal human osteoblasts (NHOst). After a 1-week incubation, PEC made from polysaccharides having carboxyl groups as polyanions showed low viability of NHOst on it although the NHOst on it showed an enhancement in their differentiation level. On the other hand, NHOst on PEC made from sulfated or phosphated polysaccharides showed similar attachment and morphology to those on the collagen-coated dish. When the number of NHOst was estimated after 1 week, the number on the PEC was ranged from 70% to 130% of those on the collagen-coated dish, indicating few effects of these PEC on cell proliferation. In addition, NHOst on PEC films made from sulfated polysaccharides differentiated to a level very similar to that observed on the collagen-coated dish, indicating that these PEC films maintain the normal potential of NHOst to both proliferate and differentiate. Measurement of gap junctional intercellular communication of NHOst on PEC revealed that PEC did not inhibit communication, suggesting that PEC films have few effects on cell homeostasis. Thus, PEC made from the sulfated polysaccharide may be a useful material as a new scaffold for bone regeneration.

The response of primary articular chondrocytes to micrometric surface topography and sulphated hyaluronic acid-based matrices
Hamilton, D. W., M. O. Riehle, et al. (2005), Cell Biol Int 29(8): 605-15.
Abstract: Understanding the response of chondrocytes to topographical cues and chemical patterns could provide invaluable information to advance the repair of chondral lesions. We studied the response of primary chondrocytes to nano- and micro-grooved surfaces, and sulphated hyaluronic acid (HyalS). Cells were grown on grooves ranging from 80 nm to 9 microm in depth, and from 2 microm to 20 microm in width. Observations showed that the cells did not spread appreciably on any groove size, or alter morphology or F-actin organization, although cells showed accelerated movement on 750 nm deep grooves in comparison to flat surfaces. On chemical patterns, the cells migrated onto, and preferentially attached to, HyalS and showed a greater degree of spreading and F-actin re-arrangement. This study shows that 750 nm deep grooves and sulphated hyaluronic acid elicit responses from primary chondrocytes, and this could have implications for the future direction of cartilage reconstruction and orthopaedic treatments in general.

The restoration of anatomic form of atrophied alveolar processes of jaws with the help of bioimplant lioplast
Kupryakhin, V. A. and L. T. Volova (2005), Cell Tissue Bank 6(2): 125-9.
Abstract: The purpose of the present research was: 1. To investigate the opportunity of application of allogen osteoplastic materials such as Lioplast, received in Samara Tissue Bank of Samara State Medical University. 2. To work out a new technique of producing lyophilized allogen osteoplastic materials, such as Lioplast, with application of an ultrasonic method of clearing. 3. The development of various techniques of operative intervention on jaws for increase in volume of atrophied, as a result of secondary adentia, alveolar shoot. 4. The application of spongy allogen osteoplastic material as a skeleton for filling in surgical operations on jaws. 5. The demonstration of the Technique of a bone-periostic Lioplast 'sandwich' for formation of an alveolar shoot.

The restoration of the articular surfaces overlying Replamineform porous biomaterials
Chiroff, R. T., R. A. White, et al. (1977), J Biomed Mater Res 11(2): 165-78.
Abstract: Replamineform porous implants (4 mm X 4 mm diameter) were placed into full-thickness cartilage and bone defects of the weight-bearing surface of the lateral femoral condyles of adult male white rabbits. These were analyzed at 1 day, 1 week, 6 weeks, 3 months, and 6 months for 1) ingrowth of tissue within the implants and 2) restoration of the articular surface overlying them. Appropriate unfilled, but similar, control defects were also studied. Mineralized bone was seen within the substance of both the TiO2 and hydroxyapatite implants at 1 week; this extremely rapid response was present in every specimen studied and was not seen with alphaAl2O3 or control animals. With the passage of time, maturation of this bone ingrowth occurred so that by 3 months, they were all incorporated into the surrounding bone. Only the hydroxyapatite implants showed consistent regenerative healing of hyaline articular cartilage from the margins of the defects with the passage of time; this occurred whenever the subchondral bone adjacent to the defect proliferated in a "creeping" fashion over the articular aspect of the implant, and the undamaged cartilage then followed it. Fibrocartilage, and not hyaline cartilage, formed the articular surface over the TiO2 and alphaAl2O3 implants and in the controls.

The Road to Bioabsorbable Stents: Reaching Clinical Reality?
Erne, P., M. Schier, et al. (2005), Cardiovasc Intervent Radiol
Abstract: This article provides an overview of the evolution of revascularization devices since Gruntzig's initial introduction of balloon angioplasty in 1977. In-stent restenosis (ISR) is the major shortcoming of conventional (permanent-implant) stent therapy; even with the innovation and promising benefits of drug-eluting stents, management of ISR is very difficult. ISR is mainly caused by the interaction between the blood and the stent surface and a permanent mechanical irritation of the vascular tissue. Thus stenting technology has moved toward the development of temporary implants composed of biocompatible materials which mechanically support the vessel during the period of high risk for recoil and then completely biodegrade in the long term. Preclinical and first clinical experiences with bioabsorbable magnesium stents are discussed.

The role of adsorbed fibrinogen in platelet adhesion to polyurethane surfaces: a comparison of surface hydrophobicity, protein adsorption, monoclonal antibody binding, and platelet adhesion
Wu, Y., F. I. Simonovsky, et al. (2005), J Biomed Mater Res A 74(4): 722-38.
Abstract: Ten specially synthesized polyurethanes (PUs) were used to investigate the effects of surface properties on platelet adhesion. Surface composition and hydrophilicity, fibrinogen (Fg) and von Willebrand's factor (vWf) adsorption, monoclonal anti-Fg binding, and platelet adhesion were measured. PUs preadsorbed with afibrinogenemic plasma or serum exhibited very low platelet adhesion, while adhesion after preadsorption with vWf deficient plasma was not reduced, showing that Fg is the key plasma protein mediating platelet adhesion under static conditions. Platelet adhesion to the ten PUs after plasma preadsorption varied greatly, but was only partially consistent with Fg adsorption. Thus, while very hydrophilic PU copolymers containing PEG that had ultralow Fg adsorption also had very low platelet adhesion, some of the more hydrophobic PUs had relatively high Fg adsorption but still exhibited lower platelet adhesion. To examine why some PUs with high Fg adsorption had lower platelet adhesion, three monoclonal antibodies (mAbs) that bind to sites in Fg thought to mediate platelet adhesion were used. The antibodies were: M1, specific to gamma-chain C-terminal; and R1 and R2, specific to RGD containing regions in the alpha-chain N- and C-terminal, respectively. Platelet adhesion was well correlated with M1 binding, but not with R1 or R2 binding. When these mAbs were incubated with plasma preadsorbed surfaces, they blocked adhesion to variable degrees. The ability of the R1 and R2 mAbs to partially block adhesion to adsorbed Fg suggests that RGD sites in the alpha chain may also be involved in mediating platelet adhesion and act synergistically with the C-terminal of the gamma-chain.

The role of bacterial-laden biofilms in infections of maxillofacial biomaterials
Nishioka, G. J., J. K. Jones, et al. (1988), J Oral Maxillofac Surg 46(1): 19-25.
Abstract: Biomaterials from 11 consecutive patients with persistent infections refractory to antimicrobial therapy and local wound care were surgically removed and studied by scanning electron microscopy for the presence of bacterial-laden biofilms. Unlike previously reported biomaterial infections involving other regions of the body, infections in this study were not associated with a conspicuous bacterial-laden biofilm. Instead, adherent light bacterial colonization without a biofilm layer was noted. The only specimen that was suggestive of a bacterial-laden biofilm was in a patient who suffered from a chronic infection. Consistent with previous reports, bacterial colonization was frequently polymicrobial. Observations made in this study suggest that bacterial adherence may not require an obvious biofilm layer.

The role of biomaterials as occupational hazards in dentistry
Hensten-Pettersen, A. and N. Jacobsen (1990), Int Dent J 40(3): 159-66.
Abstract: Many of the biomaterials and auxilliary products used in dentistry are chemically and biologically reactive and may be of concern in occupational safety programmes. Observations from 1936 to 1975 indicated that most occupational problems were related to skin contact with procaine, soaps, eugenol, iodine, formalin, phenol, and other disinfectants. Methyl methacrylate monomer was identified as an irritant and allergen in the later part of this period. Investigations from 1975 to 1985 indicated that disinfectants and detergents were still important causes of dermatoses, whereas reactions to procaine had been replaced by reactions to pantocaine. Furthermore, adverse reactions to methyl methacrylate monomer and to elastomeric impression materials had replaced the former iodine, tricresol and eugenol reactions. In recent studies the frequency of occupation-related dermatoses varied from 21 per cent to 43 per cent, depending on the prevailing material usage in the various specialties. Reactions to local anaesthetics seemed to have disappeared. Transient, irritative reactions of the eyes and airways have been observed, mostly associated with exposure to volatiles from resin-based materials, X-ray chemicals and cleansers. The occupational problems related to biomaterials in dentistry seem to have been fairly constant over the years, reflecting the type of materials in common use, and with dermatological disorders being a tenacious companion. Neuropathological conditions in dental technicians have been associated with prolonged exposure to vapours of methyl methacrylate monomer. The more recent extensive use of volatile resin-based materials, and the use of protective gloves seems to have created new problems that need to be investigated.

The role of biomaterials in insulin delivery systems
Bruck, S. D. (1980), Int J Artif Organs 3(5): 299-304.
Abstract: The control of blood glucose levels in diabetes involving devices are critically reviewed, and the role of blood-contacting biomaterial components analyzed. These include mechanical insulin-delivery systems of the closed-loop type that require an electronic glucose sensor and feedback, and open-loop systems that deliver insulin without a sensor and feedback. Whole pancreatic and islet transplantations, islet encapsulation, and the potential role of polymeric sustained drug delivery systems are discussed. The medical and social impacts of diabetes mellitus are of prime public health concern and of even greater magnitude than those of heart disease in the United States. While future advances in device design, miniaturization, and biomaterials technology will significantly add to the arsenal of therapeutic alternatives, devices capable of controlling blood glucose levels ought to be viewed as mere interim phases rather than as final goals of the problem.

The role of biomaterials science in the next generation of artificial organ technology
Rosen, J. J. (1988), ASAIO Trans 34(3): 163-7.

The role of different biomaterials on adhesion of nontransformed buccal epithelial cells
Tucci, M. A. and H. A. Benghuzzi (1994), Biomed Sci Instrum 30: 205-12.
Abstract: The specific objective of this study was to investigate the effect of various biomedical polymers on the adhesion rate of buccal epithelial cells (BEC) as a model for biocompatibility. The BEC in this study were isolated, biotin labeled and seeded by following standard laboratory procedures. A total of 2.5 x 10(5) cells was plated in each microtiter-well pretreated with various concentrations of (0.01, 0.10 and 1% wt/vol) poly-L-valanine (P-Val), poly-L-alanine (P-Ala), poly-glycine (P-Gly), poly-L-tryptophan (P-Trp), poly-L-asparagine (P-Asn) and buffered control. At the end of 1, 4, and 24 hours the assay was developed by utilizing avidin-horseradish peroxidase and o-phenylenediamine dihydrochloride as substrate to measure biotin-labeled-BEC. Cell number was then determined using a standard curve prepared by using known BEC number vs. absorbance units. The data from this study suggest that: (I) the ease of adhesion of BEC was in the following order: P-Val > P-Gly = P-Trp = P-Ala > P-Asn > P-Asp = Control, (II) the rate of BEC spreading was strongly influenced by both incubation time and the polymer concentration, (III) the surface attachment of BEC to the polymer were demonstrated to vary depending on their chemical structure and level of microporosity. Thus, overall observation led us to conclude that the surface reactivity of polymer materials must always be taken into account in discussing their biocompatibility in vivo.

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