Biomaterials.info - Resources for Engineers

Record 801 to 820

Augmented humoral and cellular immune responses to hepatitis B DNA vaccine adsorbed onto cationic microparticles
He, X., L. Jiang, et al. (2005), J Control Release 107(2): 357-72.
Abstract: Plasmid expressing HBV small envelope antigen was formulated with poly(lactide-co-glycolide-acid) (PLGA) and cetyltrimethylammonium bromide (CTAB) to generate highly uniform microparticles. Controlled release of DNA from these microparticles was demonstrated in vitro and in vivo using flow cytometry and confocal laser scanning microscopy with the focus on localization and quantitatively evaluation of antigen-presenting cells (APCs) involved in the expression of target antigen. Compared to mice vaccinated with naked DNA, mice immunized with PLGA-CTAB-DNA microparticles displayed a much higher percentage of CD11c+, HBsAg-expressing APCs in the draining lymph nodes at 24 h and day 14 postinoculation. In addition, a prolonged transcription of plasmid DNA was detected by RT-PCR in mice immunized with the microparticles. A significantly enhanced immunogenicity of PLGA-CTAB-DNA over naked DNA was observed in immunized mice, including higher levels of antibody production, interferon gamma (IFN-gamma) secretion and cytotoxic T lymphocyte activity. Mice immunized with PLGA-CTAB-DNA microparticles also showed greater efficacy of immunoprotection against challenge of transplanted HBsAg-expressing tumor cells. Our data suggest that controlled release of the PLGA-CTAB-DNA microparticles might involve in the mechanisms of its augmented immunogenicity and enhanced immunoprotection.

Autologous chondrocyte implantation with collagen bioscaffold for the treatment of osteochondral defects in rabbits
Willers, C., J. Chen, et al. (2005), Tissue Eng 11(7-8): 1065-76.
Abstract: Osteochondral injury is therapeutically irreversible within current treatment parameters. Autologous chondrocyte implantation (ACI) promises to regenerate hyaline articular cartilage, but conventional ACI is plagued by complications determined by periosteal grafting. Here we propose the utilization of collagen membrane in ACI as an effective bioscaffold for the regeneration of osteochondral lesions. Using a rabbit model of osteochondral injury, we have inoculated autologous chondrocytes onto a type I/III collagen scaffold [so-called matrix-induced ACI (MACI)] and implanted into 3-mm osteochondral knee defects. All untreated defect histology showed inferior fibrocartilage and/or fibrous tissue repair. In our time-course study, ACI with type I/III collagen membrane regenerated cartilage with healthy osteochondral architecture in osteochondral defects at 6 weeks. At 12 weeks, articular cartilage regeneration was maintained, with reduced thickness and proteoglycan compared with the adjacent cartilage. Both 6-week (p < 0.01) and 12-week (p < 0.05) ACI with collagen membrane showed significant improvement as compared with untreated controls. To further examine the efficacy of cartilage regeneration by ACI, we conducted a dose-response study, using chondrocytes at various cell densities between 10(4) and 10(6) cells/cm(2). The results showed that cell density had no effect on outcome histology, but all cell densities were significantly better than untreated controls (p < 0.01) and cell-free collagen membrane treatment (p < 0.05). In short, our data suggest that autologous chondrocyte-seeded type I/III collagen membrane is an effective method for the treatment of focal osteochondral knee injury in rabbits.

Autologous human fibrin as the biomaterial for tissue engineering
Ruszymah, B. H. (2004), Med J Malaysia 59 Suppl B: 30-1.
Abstract: Patient own fibrin may act as the safest, cheapest and immediate available biodegradable scaffold material in clinical 1 tissue engineering. This study investigated the feasibility of using patient own fibrin isolated from whole blood to construct a new human cartilage, skin and bone. Constructed in vitro tissues were implanted on the dorsal part of the nude mice for in vivo maturation. After 8 weeks of implantation, the engineered tissues were removed for histological analysis. Our results demonstrated autologous fibrin has great potential as clinical scaffold material to construct various human tissues.

Automated quantitative analysis of complex lipidomes by liquid chromatography/mass spectrometry
Hermansson, M., A. Uphoff, et al. (2005), Anal Chem 77(7): 2166-75.
Abstract: Recent advances in mass spectrometry have revolutionized the analysis of lipid compositions of cells and other biomaterials by simplifying the analytical protocol dramatically and by increasing the sensitivity of detection by several orders of magnitude. However, the throughput of the published mass spectrometric methods is severely limited by data analysis, which requires extensive operator involvement. Consequently, we have developed an automated method that allows unattended identification and quantification of lipid molecular species of all the major lipid classes from a two-dimensional chromatographic/mass spectrometric data set. More than 100 polar lipid species could be automatically quantified from different biological samples with good accuracy and reproducibility. The response was linear over approximately 3 orders of magnitude with the equipment used, and approximately 35 samples could be analyzed in a day. This method makes high-throughput lipidomics feasible in biology, biotechnology, and medicine.

Axial correction of pes varus by transverse-opening wedge osteotomy and T-plate fixation with beta-tricalcium phosphate (beta-TCP) transplantation in dachshunds
Izumisawa, Y., T. Seno, et al. (2005), J Vet Med Sci 67(4): 437-40.
Abstract: Axial correction was performed surgically in two miniature dachshunds presenting with lateral patellar dislocation and limping caused by pes varus. Pes varus had resulted from asymmetric closure of the physis of the distal tibia. Prior to surgery, osteotomy was simulated by measuring X-ray films to determine the distance required for the wedge opening. Transverse-opening wedge osteotomy was performed on the medial side of the distal tibia, and beta-tricalcium phosphate (beta-TCP) was inserted in a wedge shape into the area created by the cuneiform osteotomy. Finally, the tibia was fixed by a veterinary 1.5/2.0-mm T-plate. Both dogs were able to walk a few days after surgery, and the lateral dislocation of the patella normalized almost completely in about one month. At two months, X-ray films showed that the implant had remained in position without any dislocation, and the beta-TCP had fused with the surrounding bone.

Backfill for iliac-crest donor sites: a prospective, randomized study of coralline hydroxyapatite
Bojescul, J. A., D. W. Polly, Jr., et al. (2005), Am J Orthop 34(8): 377-82.
Abstract: We report on a prospective randomized study of coralline hydroxyapatite (CH) used as backfill for iliac-crest donor sites. Autogenous iliac-crest bone graft is routinely harvested for spinal fusion. Donor-site morbidity is underappreciated; the presumption is that donor sites regenerate. In this study, we assessed the biological viability of the backfill CH (Pro OsteonTM Implant 500 Hydroxyapatite Bone Void Filler; Interpore, Irvine, Calif) and compared donor-site morbidity after harvest. Twelve patients (11 men, 1 woman) were enrolled: 5 in the backfill group and 7 in the no-backfill group. As part of routine evaluations done preoperatively and 6 weeks, 3 months, 6 months, and 1 year postoperatively, plain radiographs and computed tomography (CT) scans were used to assess bone ingrowth, and technetium bone scans were used to assess biological activity. Postoperative pain analysis was also done. Ten patients (9 men, 1 woman) completed the study. Of the 4 completers in the backfill group, 3 (75%) showed bony ingrowth on plain radiographs and CT scans at 1 year; the fourth patient showed bony ingrowth only on plain radiographs. All 4 patients showed biological activity on bone scans and reported mild pain to no pain. Of the 6 completers in the no-backfill group, 1 (17%) showed bony ingrowth on plain radiographs and CT scans. No patient showed biological activity on bone scans at 1 year. CH aids in iliac-crest healing after bone-graft harvesting by acting as a biological osteoconductive matrix. Postoperative pain at the bone-graft site is potentially reduced. More studies of larger numbers of patients are needed to assess the true long-term benefits of this material in a clinical setting.

Baclofen-loaded microspheres in gel suspensions for intrathecal drug delivery: in vitro and in vivo evaluation
Lagarce, F., N. Faisant, et al. (2005), Eur J Pharm Biopharm 61(3): 171-80.
Abstract: Severe spasticity is a very disabling disorder treated by continuous baclofen intrathecal infusion which unfortunately remains an expensive and uncomfortable treatment. In order to address these issues, new sustained release formulations designed for intrathecal baclofen delivery were sought with the aim of minimising the burst effect of baclofen which can lead to toxicity. Baclofen was encapsulated in poly(lactide-co-glycolide) (PLGA) microspheres which were then dispersed in chitosan thermosensitive gels, Pluronic PF-127 gels, carboxymethylcellulose solutions or Ringer lactate solution. The release rate was assessed in vitro using continuous flow cells and in vivo after intrathecal injection in goats: baclofen was quantified in cerebrospinal fluid (CSF) and plasma, and the associated pharmacological effect was evaluated. The results showed that the burst effect was reduced by at least a factor of 2 in vitro, after microsphere dispersion in viscous media. In vivo, PF-127 gel was found to be the best vehicle to reduce the burst effect by a factor of 10 in CSF, and by a factor of 2 in plasma. The toxic effect of baclofen due to the burst effect was reduced by the dispersion in PF127 gels. Therapeutic levels of baclofen in CSF were maintained during at least 1 month.

Bacteria/blood/material interactions. I. Injected and preseeded slime-forming Staphylococcus epidermidis in flowing blood with biomaterials
Brunstedt, M. R., S. Sapatnekar, et al. (1995), J Biomed Mater Res 29(4): 455-66.
Abstract: Blood-material interactions were studied using in vitro recirculation with human blood, slime-forming Staphylococcus epidermidis, and cardiovascular materials. Staphylococcus epidermidis, under preseeded or injected conditions, adhered to nonsmooth materials and elevated plasma levels of fibrinopeptide A (FpA) and C3a in the presence of all materials. Increased white blood cell (WBC) and platelet adhesion and thrombospondin and platelet factor 4 (PF4) release were noted for respective materials in the presence of injected bacteria. Materials that adhered significant quantities of injected S. epidermidis exhibited low levels of adsorbed proteins. Materials with high levels of preseeded S. epidermidis showed high levels of adsorbed proteins. Adhesion of preseeded bacteria and blood plasma elevations of C3a and FpA were lowest on semicrystalline polymer substrates, intermediate on halogenated substrates, and highest on amorphous substrates. In the presence of injected bacteria, WBCs and platelets adhered at earlier recirculation times to amorphous substrates than to semicrystalline substrates.

Bacterial adherence to biomaterials and tissue. The significance of its role in clinical sepsis
Gristina, A. G. and J. W. Costerton (1985), J Bone Joint Surg Am 67(2): 264-73.
Abstract: The direct examination of tissue and biomaterials from prosthesis-related infections of twenty-five patients showed that the causative bacteria grew in glycocalyx-enclosed biofilms that were adherent to surfaces of biomaterials and tissues in 76 per cent. This high rate of recovery of adherent biofilm-mediated growth suggests that the process occurs commonly in the presence of a foreign body or biomaterial-related infection. Because of the adherent mode of growth of the infecting organisms, accurate microbiological sampling was difficult. The analysis of joint fluids or of swabs of excised tissue and of prosthetic surfaces often yielded only one species from what was a polymicrobial population based on electron microscopic studies. We adapted direct quantitative sampling methods from environmental microbiology in order to recover a large number of species from these infections, but comparison of the organisms isolated by these techniques with the morphological types that were seen by electron microscopy indicated that in some instances all bacterial components of the biofilms were still not being recovered.

Bacterial adherence to titanium surface coated with human serum albumin
Kinnari, T. J., L. I. Peltonen, et al. (2005), Otol Neurotol 26(3): 380-4.
Abstract: HYPOTHESIS: An albumin coating on titanium implants will inhibit bacterial adhesion on the implant surface. BACKGROUND: Bacterial, protein, and platelet adhesion on otologic implants and tympanostomy tubes is a major reason for implant sequelae and can eventually lead to implant removal. The role of albumin coating of the implant in prevention of protein adhesion on implant surface has already been tested by the authors. In the present study the authors examined the in vitro adherence of Staphylococcus aureus and Pseudomonas aeruginosa on an albumin-coated and uncoated titanium surface. METHODS: Human serum albumin (HSA)-coated and uncoated titanium surfaces were exposed to viable S. aureus and P. aeruginosa and, after washings, photographed by fluorescence microscopy to quantify the adhered bacteria, which was stained with acridine orange. RESULTS: Bacteria in the suspension adhered at a significantly lesser rate to the coated surfaces than to the uncoated surfaces, with overall bacterial adhesion dependent on bacterial concentration. Binding of S. aureus on HSA-coated surfaces was inhibited significantly (from 82 to 95% depending on concentration). Binding of P. aeruginosa was inhibited from 29 to 37%. CONCLUSION: Because albumin coating can reduce bacterial adherence on titanium surfaces in vitro, reduction is possible in bacterial contamination and infection of the HSA-coated titanium implant in vivo.

Bacterial adhesion to titanium-oxy-nitride (TiNOX) coatings with different resistivities: a novel approach for the development of biomaterials
Koerner, R. J., L. A. Butterworth, et al. (2002), Biomaterials 23(14): 2835-40.
Abstract: In this study the quantitative adhesion of a strain of Staphylococcus epidermidis, Streptococcus mutans and Pseudomonas aeruginosa to and the ease of removal from different TiNOX coatings was investigated by means of a parallel plate flow chamber and in situ image analysis. Quality of adhesion was determined by counting bacteria which remained attached to the surface after exposure to an air-liquid interface. S. epidermidis and S. mutans showed a bipolar adhesion pattern with highest numbers of adhesion at low and high resistivity with lowest adhesions at a resistivity of 10(4) microohms cm. P. aeruginosa was the least adherent organism. These results indicate that the affinity of these three strains under the current experimental conditions is minimal for TiNOX coatings with a specific resistivity. TiNOX coatings with pre-adsorbed fibrinogen showed different numbers of S. epidermidis adhered to the different coatings. However, the affinity of this strain for fibrinogen-coated TiNOX remains low when the resistivity is around 10(4) microohms cm. This indicates that the specific influence of the resistivities of the TiNOX coatings is transferred through the adsorbed fibrinogen film to the interface with adhering bacteria.

Bacterial biofilm development on hydroxyapatite-coated glass
Elliott, D., J. Pratten, et al. (2005), Curr Microbiol 51(1): 41-5.
Abstract: Glass plates are frequently used as the substratum in flow cell experiments to allow continuous non-destructive observations of biofilm development via microscopy. The aim of this study was to evaluate hydroxyapatite-coated glass as a substratum for flow cell experiments, in comparison to plain glass, for modelling primary colonization of the tooth surface by Streptococcus sanguis. Glass plates were magnetron sputter coated with hydroxyapatite, producing a thin transparent layer. Biofilm development in the flow cell was recorded using image capture from a microscope, and images were analyzed to determine percentage coverage of the substratum over 24 h. Removal of biofilm by increasing the flow rate was also assessed. No statistically significant differences were detected between S. sanguis biofilms grown on the two different substratum materials. Hence, this work supports the proposal that the conditioning film reduces the influence of substratum surface properties.

Bacterial colonization on different suture materials--a potential risk for intraoral dentoalveolar surgery
Otten, J. E., M. Wiedmann-Al-Ahmad, et al. (2005), J Biomed Mater Res B Appl Biomater 74(1): 627-35.
Abstract: In this in vivo and in vitro study on resorbable (Monocryl and nonresorbable (Deknalon) monofilament sutures used in intraoral dentoalveolar surgery the bacterial colonization was compared. For the in vivo study the sutures were applied in 11 patients during dental surgery. Eight days postoperative the sutures were removed and the adhered bacteria were isolated and identified by biochemistry, morphology, antibiotic susceptibility, and gas chromatography. The colonization was studied by scanning electron microscopy. Aerobic and anaerobic bacteria were isolated in nearly equal colony-forming units (cfu) on each suture. In comparison with Monocryl about 15% more aerobic and anaerobic strains were isolated on Deknalon. Regarding the pathogens only, about three times more anaerobic strains were isolated on both sutures in total. Additionally, more pathogens were found on Deknalon than on Monocryl (aerobic >40%, anaerobic >25%). The variety of bacteria correspond with purulent infections, not with normal oral flora. Intraindividual comparisons of cfu showed differences in dependence of the patient as described for subgingivale plaques. For the in vitro study the sutures were incubated with Streptococcus intermedius and Prevotella intermedia for 0.5 h. Scanning electron microscopy was performed to examine qualitatively the level of bacterial adherence. After 0.5 h the bacteria adhered very well. The colonization rate of Streptococcus intermedius on both sutures was similar. Coccoid bacteria within biofilms were seen. The growth of Prevotella intermedia was much better on Deknalon than on Monocryl. The risk of bacteremia at the time of suture removal is discussed.

Bacterial infection of biomaterials. Experimental protocol for in vitro adhesion studies
Bryers, J. D. and S. Hendricks (1997), Ann N Y Acad Sci 831: 127-37.
Abstract: Some of the more common reactor systems and novel diagnostic tools employed in the study of bacterial cell adhesion and biofilm formation have been described. Sampling and experimental requirements are shown to greatly influence the design and construction of a biofilm reactor. As analytical techniques evolve, the capability to non-invasively follow the development of biofilms and to assess the attached cell reactivity has increased. Both non-invasive and invasive diagnostic methods affect the type and design of biofilm flow reactor with both types of analyses providing complementary information on biofilm processes. To correctly interpret the contribution of a specific rate process to the net accumulation of cells at a substratum, one requires a reactor system devoid of any mass transfer limitations and a process analysis approach to allow for the correct collection and analysis of data.

Bacterial products primarily mediate fibroblast inhibition in biomaterial infection
Henke, P. K., T. M. Bergamini, et al. (1998), J Surg Res 74(1): 17-22.
Abstract: PURPOSE: The stimulation of fibroblast growth is essential for the normal healing and tissue integration of biomaterials. The local elevation of proinflammatory mediators in infected perigraft fluid (PGF) may inhibit this growth. We sought to determine whether infected PGF inhibited fibroblast growth, and, if so, whether this was primarily dependent on the biomaterial, bacteria, or host. METHODS: In vivo Dacron or expandable polytetra-fluoroethylene (ePTFE) grafts, sterile or colonized with slime-producing (RP-62A, viable or formalin-killed) or nonslime-producing (RP-62NA) Staphylococcus epidermidis (1 x 10(7) CFU/cm2), were implanted in Swiss Webster mice, and the PGF was harvested at 7 and 28 days. Antibodies to tumor necrosis factor alpha, interleukin 1 alpha, interferon gamma (7 micrograms/day), and indomethacin (50 micrograms/day) were administered by microinfusion pumps for 7 days and the PGF was harvested. Inhibition of the proinflammatory mediators was confirmed by enzyme-linked immunosorbant assay. The nontreated, heat-treated, or trypsin-digested in vivo PGF was incubated with an in vitro [3H]thymidine murine fibroblast (ATCC CCL-12) proliferation assay. RESULTS: Fibroblast inhibition was significant at 7 and 28 days with infected PGF incubation compared with sterile and was not dependent on bacterial slime production or viability. Dacron sterile PGF did not significantly inhibit fibroblasts compared with control, whereas sterile ePTFE stimulated (P < 0.05) fibroblasts. Treatment of the PGF with proinflammatory cytokines, heat, and trypsin failed to reverse fibroblast inhibition in the infected state. CONCLUSION: Biomaterial infection is associated with fibroblast inhibition that is dependent primarily on bacterial products and not the host or biomaterial. Conservative intervention strategies for graft infection need to address the problem of poor healing as well as bacterial clearance.

Bacterial sterility of stored nonanimal stabilized hyaluronic acid-based cutaneous filler
Bhatia, A. C., K. A. Arndt, et al. (2005), Arch Dermatol 141(10): 1317-8.

Bacteriorhodopsin: mutating a biomaterial into an optoelectronic material
Hampp, N. A. (2000), Appl Microbiol Biotechnol 53(6): 633-9.
Abstract: Bacteriorhodopsin (BR) is the key protein for the halobacterial photosynthetic capabilities and is one of the very rare molecules which occur in crystalline form in nature. Since its discovery, which was reported in 1971, many efforts have been made to exploit the obvious technical potential of this molecule. Successful application of gene technology methods for the modification of the physical function of a biomolecule was first demonstrated with BR. This approach points the way to a new class of materials derived from evolutionary optimized biomaterials by genetic re-engineering. Mutated BRs proved to have significant advantages over the wild type in optical applications. The current status of potential technical applications of BR is reviewed. BR is employed as a photoelectric, photochromic or energy-converting element. First systems now exist which demonstrate the successful integration of this new material into existing technologies. Analyzing the patents filed, which claim the processing or application of BR, gives an indication to areas where further technical uses are to be expected in the near future.

Balloon alignment T-stenting for bifurcation coronary artery disease using the sirolimus-eluting stent
Rizik, D. G., D. A. Dowler, et al. (2005), J Invasive Cardiol 17(8): 437-9.

Bangkok biomaterial center: 15 years experience in tissue banking
Vajaradul, Y. (2000), Cell Tissue Bank 1(3): 229-39.
Abstract: Tissue banking is started in Thailand in 1979 at the Department of Orthopaedic Surgery, Siriraj Hospital, Bangkok. At that time tissues produced were freeze-dried bone allografts which were sterilized by ethylene oxide. In 1984, the freeze-dried tissue allograft project received an award from the National Research Council of Thailand. The Bangkok Biomaterial Center was officially inaugurated on December 6, 1984 under the Royal Patronage of H.R.H. Princess Galyanivadhana and is located inside the Siriraj Hospital. The Center is involved in the procurement, processing, storage and development of bone and tissue allografts. A variety of allografts including bone, cartilage, fascia lata, dura mater, cornea and also cardiovascular tissues have been procured and processed. Preservation and long-term storage are accomplished by freeze drying and deep freezing. Grafts prepared by the Center are supplied free of charge at the request of surgeons in hospitals throughout Thailand and in neighboring countries. The Center acts as the National Tissue and Allograft Bank of Thailand. From December 1984 to February 2000, the Center has processed a total of 20 524 allografts: 16 981 freeze-dried bones, 705 deep-frozen bones, 1838 freeze-dried amnion, 559 freeze-dried dura mater, 342 freeze-dried fascia lata, 46 costal cartilage, 18 corneas, 2 skin, 5 trachea, 22 fresh tendon and 6 bone substitutes. The allografts processed were used in 2049 patients by 223 surgeons in 53 hospitals in Thailand and 4 cases in neighboring countries. There have been 413 cadaveric donors, 619 living donors, 16 brain dead donors and 270 graveyard donors. There have been complications in 126 patients (6.14%) due to various clinical conditions. There have been production and application of 4 hydroxyapatite occular implant by the Center. The Center is in the process of establishing a full-fledged Research, Clinical and Cell Culture Laboratory.

Basic fibroblast growth factor activates ERK and induces c-fos in human embryonic stem cell line MizhES1
Kang, H. B., J. S. Kim, et al. (2005), Stem Cells Dev 14(4): 395-401.
Abstract: Human embryonic stem (hES) cells can be maintained in a proliferative undifferentiated state in vitro by growing them on feeder layers of mouse embryonic fibroblast (MEF) cells along with basic fibroblast growth factor (bFGF/FGF-2). To understand the molecular mechanisms involved in the requirement of bFGF in human ES cells, we investigated expression of FGF receptors and intracellular signaling events in response to bFGF in human ES cell line MizhES1. On the basis of the results of RT-PCR, clear expression of FGF receptors FGFR1, FGR2, and FGFR3 was noticed. Because MAPK, PI3K, and PKC pathways are well-known pathways triggered by bFGF in other cells, these pathways were investigated after stimulation with bFGF. bFGF did not induce activation of PI3K or PKC, but induced activation of ERK (extracellular signal-regulated kinase). To monitor the consequences of ERK activation, we examined expression of the immediate early gene c-fos, one downstream target of the MEK1/ERK pathway. mRNA and protein levels of the c-fos gene were increased by bFGF. Induction of c-Fos was dependent on MEKl. Therefore, it is likely that bFGF contributes to maintenance of human ES cells, at least in part, through the MEK1/ERK pathway.

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