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Record 2461 to 2480

Incisional hernia repair: laparoscopic techniques
LeBlanc, K. A. (2005), World J Surg 29(8): 1073-9.
Abstract: Repair of incisional hernias using the laparoscopic technique has continued to evolve since its inception in 1991. An analysis of the current literature has revealed that hernias as large as 1600 cm2 have been successfully repaired with this method. The average size appears to be about 105 cm2. Several choices of a biomaterial are available today, differing in the type of synthetic product or products that are used to manufacture them. Others incorporate an absorbable component. The goal of all of them is to prevent adhesion formation. The fixation devices that can be used are also varied. The results of laparoscopic incisional hernia repair are described. The conversion rate of these procedures is an impressive 2.4% with an enterotomy rate of 1.8%. These results affirm the low risk of this operation. The recurrence rate of 4.2% confirms the permanence of the repair. This procedure may become the standard of care in the near future.

Incorporation and in vitro release of doxorubicin in thermally sensitive micelles made from poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)-b-poly(D,L-lactide-c o-glycolide) with varying compositions
Liu, S. Q., Y. W. Tong, et al. (2005), Biomaterials 26(24): 5064-74.
Abstract: Thermally sensitive block copolymers, poly(N-isopropylacrylamide-co-N, N-dimethylacrylamide)-b-poly(d,l-lactide-co-glycolide) [P(NIPAAm-co-DMAAm)-b-poly(D,L-lactide-co-glycolide) (PLGA)] with different compositions and lengths of PLGA block are synthesized and utilized to fabricate micelles containing doxorubicin (DOX), a model anticancer drug, by a membrane dialysis method for targeted anticancer drug delivery. The critical association concentration (CAC) of the polymers ranges from 4.0 to 25.0 mg/L. An increased length of core-forming block PLGA leads to a decrease in the CAC. The clearly defined core-shell structure of micelles is proved by 1H-NMR analyses of the micelles in CDCl3 and D2O. The morphology of the micelles is analyzed by transmission electron microscopy, showing a spherical structure of both blank and drug-loaded micelles. The results obtained from dynamic light scattering show that the blank and drug-loaded micelles have an average size below 200 nm. The lower critical solution temperature (LCST) of the micelles made from the various polymers is similar, around 39 degrees C in phophate-buffered solution (PBS). The presence of serum in PBS does not alter the LCST significantly. The drug loading capacity varies depending on the PLGA block. The polymers are degradable, and the degradation of PLGA-based polymers is faster than that of poly(lactide) (PLA)-based polymer. The DOX-loaded micelles are stable in PBS containing serum at 37 degrees C but deform at 39.5 degrees C above the normal body temperature, thus triggering DOX release. It is revealed by confocal laser scanning microscopy that free DOX molecules enter cell nuclei very fast and DOX-loaded micelles accumulate mostly in cytoplasm after endocytosis. At a temperature above the LCST, more DOX molecules release from the micelles and enter the nuclei as compared to the temperature below the LCST. DOX-loaded micelles show greater cytotoxicity at a temperature above the LCST. The P(NIPAAm-co-DMAAm)-b-PLGA micelles developed may be a good carrier for anticancer drug delivery.

Incorporation of fluorine ions into hydroxyapatite by a pH cycling method
Qu, H., A. L. Vasiliev, et al. (2005), J Mater Sci Mater Med 16(5): 447-53.
Abstract: Fluorine ions were incorporated into hydroxyapatite (HA) using a pH cycling method and the resulting materials were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrochemical analysis. TEM observations showed that fluoridated hydroxyapatite (FHA) nanoparticles with a narrow particle size distribution were obtained at several different levels of fluorine incorporation. Significant particle growth was observed following calcining at 1200 degrees C. The TEM data revealed that, instead of forming laminated structures, a mixture of HA and FA was obtained, and that this mixture transformed into a single homogeneous FHA phase upon heating. It was found that the efficiency of fluorine incorporation did not vary significantly with the initial HA particle size, but increased as the fluorine content of the initial solution was increased. A relatively low fluorine incorporation efficiency, approximately 60%, was attained for most of the FHA samples and this was attributed to the short holding time at each pH cycle and the limited number of pH cycles employed in the current study.

Increased erythromycin production by alginate as a medium ingredient or immobilization support in cultures of Saccharopolyspora erythraea
Hamedi, J., F. Khodagholi, et al. (2005), Biotechnol Lett 27(9): 661-4.
Abstract: Erythromycin production by Saccharopolyspora erythraea immobilized in 2% (w/v) calcium alginate or grown in medium containing 20 g sodium alginate/l inoculated with free cells was almost twice more than that of the control. S. erythraea did not consume alginate, agar, dextran, silicon antifoaming agent or cyclodextrin as a carbon source, although, all of these increased the production of erythromycin. Highest titer of erythromycin (2.3 times more than that of the control) was achieved in medium containing 1 g agar/l.

Increased osteoblast function on PLGA composites containing nanophase titania
Webster, T. J. and T. A. Smith (2005), J Biomed Mater Res A 74(4): 677-86.
Abstract: Nanotechnology creates materials that potentially outperform, at several boundaries, existing materials in terms of mechanical, electrical, catalytic, and optical properties. However, despite their promise to mimic the surface roughness cells experience in vivo, the use of nanophase materials in biological applications remains to date largely unexplored. The objective of the present in vitro study was, therefore, to determine whether when added to a polymer scaffold, nanophase compared to conventional ceramics enhance functions of osteoblasts (or bone-forming cells). Results from this study provided the first evidence that functions (specifically, adhesion, synthesis of alkaline phosphatase, and deposition of calcium-containing mineral) of osteoblasts increased on poly-lactic-co-glycolic acid (PLGA) scaffolds containing nanophase compared to conventional grain size titania with greater weight percentage (from 10-30 wt %). Because the chemistry, material phase, porosity (%), and pore size of the composites were similar, this study implies that the surface features created by adding nanophase compared to conventional titania was a key parameter that enhanced functions of osteoblasts. In this manner, the study adds another novel property of nanophase ceramics: their ability to promote osteoblast functions in vitro when added to a polymer scaffold. For this reason, nanophase ceramics (and nanomaterials in general) deserve further attention as orthopedic tissue engineering materials.

Increasing the oxidative stability of liquid and dried tuna oil-in-water emulsions with electrostatic layer-by-layer deposition technology
Klinkesorn, U., P. Sophanodora, et al. (2005), J Agric Food Chem 53(11): 4561-6.
Abstract: Omega-3 Fatty acids have numerous health benefits, but their addition to foods is limited by oxidative rancidity. Engineering the interfacial membrane of oil-in-water emulsion droplets to produce a cationic and/or thick interface is an effective method to control lipid oxidation. Cationic and thick emulsion droplet interfacial membranes can be produced by an electrostatic layer-by-layer deposition technique resulting in droplets that are coated by multiple layers of emulsifiers. Tuna oil-in-water emulsion droplets coated by lecithin and chitosan produce cationic emulsion droplets that are more oxidatively stable than emulsions coated by lecithin alone. Ethylenediaminetetraacetic acid (EDTA) was able to increase the oxidative stability of emulsions stabilized with lecithin and chitosan more effectively than mixed tocopherols. The combination of EDTA and mixed tocopherols was not more effective than EDTA alone suggesting that control of prooxidant metals was the most important antioxidant technology. The production of emulsion droplets coated with lecithin and chitosan could be an excellent technology for stabilization of oxidatively unstable lipids for use in a variety of food products.

Independence of synaptic specificity from neuritic guidance
Vogt, A. K., G. J. Brewer, et al. (2005), Neuroscience 134(3): 783-90.
Abstract: Neuronal circuits are interconnected with a high degree of specificity. While axonal guidance has been demonstrated to be crucial for the choice of the correct target region, its role in specificity at the level of individual cells remains unclear. Specificity of synapse formation may either result from precise guidance of axonal outgrowth onto the target or depend on a molecular "match" between pre- and postsynapse. To distinguish between these possibilities, an in vitro system was used in which neuritic outgrowth of rat cortical neurons is accurately guided along the narrow pathways of a surface micropattern. The micropattern consisted of a blend of extracellular matrix molecules applied to a cell repellent background of polystyrene by microcontact printing. The system reproduces guidance by attractant and repellent surface cues while no other signals that may influence synapse formation, like gradients of trophic factors or accumulations of signaling molecules, are provided. While the number of contact points between neighboring cells was strongly reduced on patterned substrates due to the geometrical restrictions, frequency of synapse formation was not different from homogeneous cultures. Thus it was unaffected by stringent guidance onto the target cell or by the number of cell-cell contacts. Moreover, a statistically significant enrichment of reciprocal contacts between mixed pairs of excitatory and inhibitory neurons over probabilistic predictions was found, which has similarly been shown by others in dissociated neuronal cultures. Our results indicate that precise axonal guidance is insufficient for target-specific synapse formation and suggest that instead recognition between individual cells is required.

Individual inflammatory response of human blood monocytes to mesh biomaterials
Schachtrupp, A., U. Klinge, et al. (2003), Br J Surg 90(1): 114-20.
Abstract: BACKGROUND: Alloplastic implants such as those employed in hernia repair induce distinct local inflammation and seroma production. As monocytes take a key position in the inflammatory foreign body reaction, their specific release of cytokines was investigated in vitro after incubation with alloplastic materials. METHODS: Human blood monocytes were isolated from buffy coats of 42 healthy blood donors. Cells were cultivated in polystyrene culture wells (4 x 10(6) cells/well) on polypropylene-polyglactin mesh, on polytetrafluoroethylene, in control wells with the addition of 1 micro g lipopolysaccharide (LPS) and on pure polystyrene. Supernatant was taken after 1 h and 5 days, and concentrations of tumour necrosis factor (TNF) alpha, interleukin (IL) 6 and IL-10 were determined. Donors were defined as 'high' or 'low' responders when concentrations of TNF-alpha were above the 75th or below the 25th percentiles, respectively. RESULTS: In contact with biomaterials, the monocytes liberated TNF-alpha, IL-6 and IL-10, similar to levels observed after stimulation with LPS. Median cytokine concentrations were not normally distributed and were influenced by donor, timepoint and applied stimulus. One donor matched the criteria for low responder and three for high responder. CONCLUSION: The individual was identified as an independent factor for the inflammatory response of monocytes to biomaterials. Moreover, high and low responders could be identified. The variability of cytokine release and the lack of a normal distribution suggest that a larger sample size should be used in future studies of cellular response.

Individual plasma proteins detected on rough biomaterials by phase imaging AFM
Holland, N. B. and R. E. Marchant (2000), J Biomed Mater Res 51(3): 307-15.
Abstract: In the past several years, atomic force microscopy (AFM) has provided topographic images of adsorbed plasma proteins in situ at unprecedented resolution. Imaging has been limited to adsorbed protein on relatively smooth model substrates such as mica, graphite, or self-assembled monolayers on which the small height of the protein can be observed from the background. The inherent roughness of biomaterial surfaces has prevented observation of adsorbed proteins in topographic images. We report imaging isolated fibrinogen molecules adsorbed on National Heart Lung and Blood Institute (NHLBI) reference materials polydimethylsiloxane and low-density polyethylene in situ using phase imaging AFM. Fibrinogen, a plasma protein important for blood coagulation and platelet aggregation, was adsorbed from dilute solution onto reference biomaterial surfaces at sub-monolayer coverage. Tapping mode AFM was used to image the samples. For polydimethylsiloxane, the lateral size of the surface features is much greater than the dimensions of proteins. This allowed adsorbed proteins to be observed in topographic images. The phase imaging signal of tapping mode AFM provides information on differences in material properties of the surface, and was used to distinguish individual protein molecules from the underlying polymer surface. On the low-density polyethylene surface, characteristic topographical features are of the same magnitude as the protein molecules, so that protein cannot be distinguished from the surface using topographic images. However, phase images were used to successfully locate and characterize the distribution of the protein. Phase imaging was not able to distinguish fibrinogen adsorbed onto expanded polytetrafluoroethylene. The utility and limitations of the phase imaging technique for characterizing protein adsorption to rough surfaces is discussed.

Induced piezoelectricity in isotropic biomaterial
Zimmerman, R. L. (1976), Biophys J 16(12): 1341-8.
Abstract: Isotropic material can be made to exhibit piezoelectric effects by the application of a constant electric field. For insulators, the piezoelectric strain constant is proportional to the applied electric field and for semiconductors, an additional out-of-phase component of piezoelectricity is proportional to the electric current density in the sample. The two induced coefficients are proportional to the strain-dependent dielectric constant (depsilon/dS + epsilon) and resistivity (drho/dS - rho), respectively. The latter is more important at frequencies such that rhoepsilonomega less than 1, often the case in biopolymers.Signals from induced piezoelectricity in nature may be larger than those from true piezoelectricity.

Inducers and inhibitors of biomineralization: lessons from pathological calcification
Giachelli, C. M. (2005), Orthod Craniofac Res 8(4): 229-31.
Abstract: OBJECTIVES: Ectopic calcification is a common response to soft tissue injury and systemic mineral imbalance and can lead to devastating clinical consequences when present in joints, heart valves and blood vessels. We have hypothesized that mineralization of matrices in any tissue is normally controlled by a balance between procalcific and anticalcific regulatory proteins such that abnormal deposition of apatite is avoided. Alterations in this balance induced by injury, disease or genetic deficiency are postulated to induce ectopic mineral deposition. Over the past several years, we have developed in vitro and in vivo models of ectopic calcification to investigate potential inducers and inhibitors of this process. RESULTS: Osteopontin, a secreted phosphoprotein, has emerged as a major inhibitor of ectopic mineralization. Osteopontin is a potent inhibitor of vascular cell calcification in vitro and mice lacking osteopontin are highly susceptible to ectopic calcification. Furthermore, osteopontin treatment of biomaterials protected against ectopic mineralization. Our studies indicate that in addition to inhibiting apatite crystal initiation and growth, osteopontin stimulates resorption of ectopic calcification via peripheral macrophages and giant cells. In contrast, inorganic phosphate has emerged as a major inducer of mineralization in these systems. Elevated inorganic phosphate (Pi) was shown to induce smooth muscle cell matrix calcification with morphological properties similar to those observed in calcified human valves and atherosclerotic plaques. Furthermore, mineralization induced by inorganic phosphate was dependent on the activity of the sodium-dependent phosphate cotransporter, Pit-1. CONCLUSIONS: These studies implicate controlled, transcellular transport of Pi as a major requirement for matrix calcification.

Induction of CD40 ligand expression in human T cells by biomaterials derived from left ventricular assist device surface
Schuster, M., A. Kocher, et al. (2001), Transplant Proc 33(1-2): 1960-1.

Induction of meniscal regeneration in dogs using a novel biomaterial
Cook, J. L., J. L. Tomlinson, et al. (1999), Am J Sports Med 27(5): 658-65.
Abstract: A unique biomaterial, porcine small intestinal submucosa, was used to construct grafts for implantation into surgically created medial meniscal defects in dogs. Five dogs received grafts and two were left untreated as controls. All dogs were evaluated at 4, 8, and 12 weeks by means of lameness scoring, force plate analysis, and ultrasonography. Twelve weeks after implantation the dogs were sacrificed and the replacement tissue was evaluated for gross and histologic appearance, amount, glycosaminoglycan content, and type II collagen immunoreactivity. Four weeks after instrumentation, both groups had lameness scores that were significantly higher than preoperative scores, but at the 8- and 12-week evaluations, scores for the grafted dogs were not different from preoperative values. The ultrasonographic appearance of replacement tissue in grafted defects resembled normal meniscus. In the untreated defects, only unorganized tissue was present. In control dogs, replacement tissue resembled fibrous tissue and cartilage erosions were visible on the medial femoral condyles. In four of the five grafted dogs, replacement tissue was grossly indistinguishable from normal meniscus. The amount of tissue in the defect was significantly greater for the grafted dogs. Histologically, replacement tissue in control dogs was composed of vascularized connective tissue with no evidence of chondroid differentiation. Replacement tissue in grafted dogs closely resembled normal meniscal tissue with respect to chondroid differentiation, collagen content, and zonal architecture. Porcine small intestinal submucosa appeared to have beneficial effects on meniscal regeneration.

Induction of proliferation and differentiation of cultured urothelial cells on acellular biomaterials
Ram-Liebig, G., A. Meye, et al. (2004), BJU Int 94(6): 922-7.
Abstract: OBJECTIVE: To determine the optimum conditions for the proliferation of urothelial cells, leading to the confluent coverage of large surfaces of biocompatible membranes, and for their terminal differentiation. MATERIALS AND METHODS: Porcine and human urothelial cells were cultured on different matrices under different growth conditions. Proliferative activity and the viability of cells were evaluated using fluorescent markers for nuclei and cytoplasm. Growth and differentiation were assessed by histological, histochemical and immunohistochemical methods. RESULTS: Under fibroblastic induction and supplementation of 5% fetal calf serum (FCS), urothelial cells showed more proliferation than in other conditions tested. Terminal differentiation of superficial cells was achieved by lowering the concentration of FCS to 1% at the air-liquid interface. CONCLUSIONS: The mitogenic effects of the extracellular matrix content of biological membranes and fibroblastic inductive factors are synergistic with each other, and can compensate for a low FCS concentration and the absence of other additives. Lowering the FCS concentration to 1% inhibits the proliferation of urothelial cells and permits their terminal differentiation.

Induction of T-cell apoptosis by polyurethane biomaterials used in left ventricular assist devices is dependent on calcineurin activation
Schuster, M., J. Ankersmit, et al. (2001), Transplant Proc 33(1-2): 1958-9.

Industrial considerations of biomaterials
Kimbell, J. T. (1973), Med Instrum 7(2): 148-50.

Infection control issues in central venous catheter care
Theaker, C. (2005), Intensive Crit Care Nurs 21(2): 99-109.
Abstract: Central venous catheters (CVCs) are now a routine part of patient management in the intensive care unit (ICU). Over time, a vast amount of literature associated with the use and care of CVCs has accumulated. The purpose of this article is to discuss the literature associated with the care of these devices in a narrative format. Although particular attention is paid to infection control issues, other fundamental areas such as catheter design, dressings, line changing and post insertion management are also discussed. The article goes on to look at the future of CVC design and concludes with an analysis of future developments related to CVCs.

Infection in inguinal hernia repair considering biomaterials and antibiotics
Gilbert, A. I. and L. L. Felton (1993), Surg Gynecol Obstet 177(2): 126-30.
Abstract: Synthetic biomaterials have been incriminated for promoting wound infection. Perioperative antibiotics have received praise for reducing the rate of infection after certain operations. These claims were tested in a cooperative multicenter prospective study of 2,493 inguinal hernia repairs. This study was done to examine the effect of prophylactic antibiotics in primary and recurrent inguinal hernia repaired with synthetic biomaterials. Clinical signs and symptoms of wound infection and the results of each infected repair are reported. The rate of infection was about 1 percent, whether or not biomaterials or antibiotics were used. More than 70 percent of wound infections occurred in patients 60 years of age or older. Removal of biomaterials from the infected wounds was not necessary and generally is not recommended. Recurrence has not occurred in any of the infected repairs. With or without prosthetic repair, the treatment of infected inguinal hernia wounds was relatively simple, of reasonable cost and concluded with a good result. The expense incurred for routine prophylactic antibiotic treatment in inguinal hernia operation could not be reconciled by any benefits obtained.

Infections from biomaterials and implants: a race for the surface
Gristina, A. G., P. Naylor, et al. (1988), Med Prog Technol 14(3-4): 205-24.
Abstract: Microorganisms in nature and disease are dependent on substratum attachment for optimal growth and development. Similarly, implanted biomaterials tend to potentiate bacteria on their surfaces so that normally friendly special or opportunistic organisms become virulent pathogens. Virulence is also enhanced because both bacteria and biomaterials interfere with host defense mechanisms. Infections centered on biomaterials are most difficult to eliminate and usually require removal of the device. The consequences of device failure are catastrophic and costly. It is the specific nature of the biomaterial surface, which is indirectly a reflection of bulk features, that causes and directs the changes in bacterial behavior which result in virulence. Features of organisms and materials and interactions responsible for these phenomena are reviewed.

Inferring the diameter of a biopolymer from its stretching response
Toan, N. M., D. Marenduzzo, et al. (2005), Biophys J 89(1): 80-6.
Abstract: We investigate the stretching response of a thick polymer model by means of extensive stochastic simulations. The computational results are synthesized in an analytic expression that characterizes how the force versus elongation curve depends on the polymer structural parameters: its thickness and granularity (spacing of the monomers). The expression is used to analyze experimental data for the stretching of various different types of biopolymers: polypeptides, polysaccharides, and nucleic acids. Besides recovering elastic parameters (such as the persistence length) that are consistent with those obtained from standard entropic models, the approach allows us to extract viable estimates for the polymers diameter and granularity. This shows that the basic structural polymer features have such a profound impact on the elastic behavior that they can be recovered with the sole input of stretching measurements.

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