|Articles about Biomaterials|
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| A comparative study of the potential of solid triglyceride nanostructures coated with chitosan or poly(ethylene glycol) as carriers for oral calcitonin delivery
Garcia-Fuentes, M., C. Prego, et al. (2005), Eur J Pharm Sci 25(1): 133-43.
Abstract: We have previously reported the formation and characterization of poly(ethylene glycol) (PEG)-coated and chitosan (CS)-coated lipid nanoparticles. In the present work our goal was to study the interaction of these surface-modified lipid nanoparticles with Caco-2 cells and to evaluate the potential of these nanostructures as oral delivery systems for salmon calcitonin (sCT). The interaction of rhodamine-loaded nanoparticles with the Caco-2 cell monolayers was evaluated quantitatively and qualitatively by confocal laser scanning microscopy and fluorimetry, respectively. The ability of these nanoparticles to reversibly enhance the transport of hydrophilic macromolecules through the monolayers was investigated by measuring the transepithelial electric resistance and the permeability to Texas Red-dextran. Finally, in vivo studies of the response to sCT-loaded nanoparticles were performed in rats. The results showed that the association of rhodamine-loaded nanoparticles to the Caco-2 cell monolayer was independent of the surface coating of the nanoparticles (CS-coated versus PEG-coated nanoparticles). However, while PEG-coated nanoparticles did not affect the permeability of Caco-2 monolayers, CS-coated nanoparticles produced a dose-dependent reduction in the transepithelial electric resistance, simultaneously to an enhanced dextran transport. The results obtained following oral administration of sCT-loaded CS-coated nanoparticles to rats showed a significant and prolonged reduction in the serum calcium levels as compared to those obtained for control (sCT solution). In contrast, the hypocalcemic response of sCT-loaded PEG-coated nanoparticles was not significantly different of that provided by the control (sCT solution). Therefore, these results indicate that the surface composition of the particles is a key factor in the improvement of the efficiency of oral sCT formulations. Moreover, the encouraging results obtained for CS-coated nanoparticles underline their potential as carriers for peptide delivery.
| A comparative study of three different biomaterials in the engineering of skeletal muscle using a rat animal model
Kamelger, F. S., R. Marksteiner, et al. (2004), Biomaterials 25(9): 1649-55.
Abstract: Defects caused by traumatic or postsurgical loss of muscle mass may result in severe impairments of the functionality of skeletal muscle. Tissue engineering represents a possible approach to replace the lost or defective muscle. The aim of this study was to compare the suitability of three different biomaterials as scaffolds for rat myoblasts, using a new animal model. PKH26-fluorescent-stained cultured rat myoblasts were either seeded onto polyglycolic acid meshes or, alternatively, suspended in alginate or in hyaluronic acid-hydrogels. In each of the eight Fisher CDF-344 rats, four capsule pouches were induced by subcutaneous implantation of four silicone sheets. After two weeks the silicone sheets were removed and myoblast-biomaterial-constructs were implanted in the preformed capsules. Specimens were harvested after four weeks and examined histologically by H&E-staining and fluorescence microscopy. All capsules were well-vascularized. Implanted myoblasts fused by forming multinucleated myotubes. This study demonstrates that myoblasts seeded onto different biomaterials can be successfully transplanted into preformed highly vascularized capsule pouches. Our animal model has paved the way for studies of myoblast-biomaterial transplantations into an ectopic non-muscular environment.
| A comparative study on the use of a HA/collagen/chondroitin sulphate biomaterial (Biostite) and a bovine-derived HA xenograft (Bio-Oss) in the treatment of deep intra-osseous defects
Scabbia, A. and L. Trombelli (2004), J Clin Periodontol 31(5): 348-55.
Abstract: OBJECTIVES: This parallel-group, randomized, clinical trial was designed to evaluate the clinical outcome of deep intra-osseous defects following reconstructive surgery with the use of a synthetic hydroxyapatite/equine Type I collagen/chondroitin sulphate biomaterial (Biostite), as compared to a bovine-derived hydroxyapatite xenograft (Bio-Oss). MATERIAL AND METHODS: Twenty-four systemically healthy subjects with moderate to advanced periodontitis, 11 females and 13 males, aged 30-64 years, seven smokers, were selected. Patients presented with one interproximal deep intra-osseous defect (intra-osseous component >or=4 mm) as clinically and radiographically evaluated. Immediately before surgery and 12 months after surgery, pocket probing depth (PPD), clinical attachment level (CAL) and radiographic depth of the defect (DEPTH) were evaluated. RESULTS: Thirteen defects were treated with Biostite (test) and 11 defects with Bio-Oss (control). In the test group, PPD amounted to 7.8+/-1.3 mm before surgery, and decreased significantly to 3.6+/-1.6 mm 12 months following surgery, while in the control group PPD significantly decreased from 7.5+/-2.0 mm pre-surgery to 3.1+/-1.0 mm post-surgery. At 1 year, CAL gain and DEPTH gain were 2.9+/-1.9 and 2.5+/-1.4 mm, respectively, in the test group, and 4.0+/-2.4 mm and 3.1+/-1.8 mm, respectively, in the control group. No statistically significant differences for PPD reduction, CAL gain and DEPTH gain were detected between the groups. CONCLUSIONS: The results of the present study indicate that both Biostite and Bio-Oss grafting biomaterials have determined a clinically and statistically significant improvement in terms of CAL gain, PPD reduction and radiographic DEPTH gain when used for the treatment of deep intra-osseous defects.
| A comparison of combinations of titanium and resorbable plating systems for repair of isolated zygomatic fractures in the adult: a quantitative biomechanical study
Hanemann, M., Jr., O. Simmons, et al. (2005), Ann Plast Surg 54(4): 402-8.
Abstract: Multiple studies have sought to determine the postreduction stability of internal fixation in zygomaticomaxillary complex (ZMC) fractures. Three-point fixation with titanium miniplates is increasingly recommended to repair these injuries. Use of bioresorbable plates has been suggested to eliminate potential postoperative hardware complications. By quantitatively comparing different combinations of titanium and resorbable plating systems, this study attempts to demonstrate which combinations will provide stable fixation of the fractured ZMC. Osteotomies were performed on 40 zygomas in 20 fresh-frozen cadaver skulls, simulating noncomminuted ZMC fractures. The control group (group 0) consisted of titanium plates at the zygomaticofrontal (ZF) suture, infraorbital rim (IOR), and zygomaticomaxillary buttress (ZMB). Group 1 consisted of titanium plates at the ZF and IOR, and a resorbable plate at the ZMB. Group 2 used a titanium plate at the ZF, and resorbable plates at the IOR and ZMB. Group 3 consisted of resorbable plates at the ZF, IOR, and ZMB. A mechanical test system was used to apply loads in the vectorial direction of the masseter. Critical forces and patterns of hardware failure were recorded. Group 0 failed at a mean force of 589 +/- 146 N (60 kg). Group 1 failed at a mean force of 507 +/- 124 N (52 kg). No statistically significant differences between groups 0 and 1 were found. The mean force required for failure in groups 2 and 3 was lower. Differences in the force required for failure between groups 2 and 3 and the control group was significant (P <0.05). Failure patterns were analyzed. The ZF plate tended to stretch predominantly in groups 1, 2, and 3, whereas it tended to break in group 0 (P = 0.005). The IOR plate demonstrated predictable screw failure in groups 2 and 3 (P = 0.007). For group 0, the ZF was the site of the majority of critical failures. For groups 2 and 3, the IOR was almost invariably the site of critical failure (P = 0.004). At the ZMB, there was no significant association between failure modes and it was rarely the site of critical failure, regardless of the method of fixation. However, the strength of fixation was proportional to the number of titanium plates used. Overall, the method of fixation significantly affected the force required for mechanical failure of ZMC fractures (P <0.0001). The presence of teeth significantly increases the force required for implant failure in ZMC fracture fixation when combinations of plates are used (P = 0.038). All combinations of titanium and resorbable plates may be sufficient to overcome the displacing forces produced by the masseter and may be used for internal fixation of isolated ZMC fractures in the adult.
| A comparison of cryopreserved vein allografts and prosthetic grafts for hemodialysis access
Madden, R. L., G. S. Lipkowitz, et al. (2005), Ann Vasc Surg 19(5): 686-91.
Abstract: In hemodialysis patients with insufficient vasculature for creation of a native arteriovenous fistula (AVF), a polytetrafluoroethylene (PTFE) graft is commonly utilized. Because of PTFE complications, our group and others have used cryopreserved cadaver femoral vein allografts (Synergraft [SYN], CryoLife, Marietta, GA) in selected patients. Based on our experience with these allografts, we hypothesized that they were more resistant to thrombosis than PTFE grafts. The purpose of this study was to compare the thrombosis rates of SYN and PTFE grafts in a prospective, randomized fashion. Our study was interrupted when the FDA ordered CryoLife, Inc. to retain certain vascular tissue products, and patient accrual stopped in 2003. Most patients referred for hemodialysis access are evaluated with bilateral, upper extremity Doppler ultrasound. Starting in 2001, those with insufficient vasculature for native AVF were offered randomization into the PTFE or SYN groups. All accesses were placed in the upper extremity, above the elbow. Access patency and complications were recorded, and failure was defined as access removal, abandonment, or replacement of > 50% with a new conduit. Prior to FDA interruption of the study, 27 patients were randomized into each group. Patient characteristics were similar, but there were significantly more males and African-Americans in the SYN group. No significant differences were seen in primary or secondary patency, number of thrombectomies, revisions, or total interventions. Significantly more fistulagrams were performed in the SYN group (p < 0.05). No infections were seen in either group, but 2 aneurysms occurred in the SYN group. Nine (33%) patients in each group died with functioning access. Access failures: In the SYN group, 8 of 27 (30%) failed, with 5 failing from multiple access stenoses unresponsive to balloon angioplasty; in the PTFE group 4 of 27 (18%) failed, with 2 failing from multiple stenoses. In conclusion, for initial hemodialysis access in patients without sufficient vasculature for native AVF, our results do not support the routine use of SYN allografts in the general dialysis population.
| A comparison of resistance to fracture among four commercially available forms of hydroxyapatite cement
Miller, L., A. B. Guerra, et al. (2005), Ann Plast Surg 55(1): 87-92; discussion 93.
Abstract: Hydroxyapatite cement is a relatively new biomaterial that has found widespread use in craniomaxillofacial surgery. Despite its common usage, complication rates as high as 32% have been reported. When failed implants are removed, implant fracture has been cited as a potential cause of failure. The purpose of this study was to evaluate resistance to fracture among 4 commercially available hydroxyapatite cement formulations. The materials tested included Norian Craniofacial Repair System (carbonated apatite cement) (AO North America, Devon, PA), Norian CRS Fast Set Putty (carbonated apatite cement) (AO North America), BoneSource (hydroxyapatite cement) (Stryker Leibinger, Portage, MI), and Mimix (hydroxyapatite cement) (Walter Lorenz Surgical, Inc, Jacksonville, FL). To ensure consistency, all materials were embedded in acrylic wells. Each material was placed into a well 2.54 cm in diameter and 0.953 cm in thickness. The materials were prepared per manufacturer specifications. All materials were incubated at 37.0 degrees C, in 6% CO2, 100% humidity for 36 hours. Using the Bionix MTS Test System, a 12-mm-diameter probe applied incremental force to the center of the disk at a rate of 0.1 mm per second. The transmitted force was measured using a Bionix MTS Axial-Torsional Load Transducer for each disk. The force which resulted in fracture was recorded for each material. Ten disks of each material were processed by this method, for a total of 40 disks. The significance of resistance to fracture for the 4 compounds was analyzed using 1-way analysis of variance with post hoc Scheffe method. Mean fracture force with related P values was plotted for direct comparison of group outcomes. Material type contributed significantly to variance in fracture force for the biomaterials studied. Norian CRS required the greatest mean fracture force (1385 N, SD+/-292 N), followed by Norian CRS Fast Set Putty (1143 N, SD+/-193 N). Mimix required a mean fracture force of 740 N, SD+/-79 N. BoneSource required a mean fracture force of 558 N, SD+/-150 N. Mimix and BoneSource required significantly less force for fracture when compared with Norian CRS and Fast Set Putty (P<0.01). Comparisons of fracture load resistance between 4 commonly used bone substitute materials have not been previously reported. Increasing biomaterial strength may reduce complications resulting from reinjury to cranioplasty sites. In this model, Norian CRS and Norian CRS Fast Set Putty demonstrated a significantly greater resistance to fracture when compared with BoneSource and Mimix.
| A comparison of suture retention strengths for three biomaterials
Obermiller, J. F., J. P. Hodde, et al. (2004), Med Sci Monit 10(1): PI1-5.
Abstract: BACKGROUND: The suture holding capacity, suture retention strength, and burst strength of three biomaterials (Marlex), SIS, and PeriGuard) were evaluated to compare their performance characteristics in an ex vivo setting representing the immediate postoperative period. MATERIAL/METHODS: A circular defect was created in the fascial tissue of the abdominal aponeurosis collected from normal dogs. Defects were repaired with either Marlex (polypropylene mesh), Periguard (bovine pericardium) or small intestinal submucosa (SIS) using 2-0 prolene and a 1.0-cm suture bite. The force required to induce failure at the repair site was recorded as the suture-holding capacity. Suture retention strength was calculated as the load distribution over the specimen cross-section in contact with the suture at the time of rupture. Burst strength of the raw materials was also measured. RESULTS: The suture-holding capacity was 370.9+/-56.2 N for Marlex; 214.3+/-36.1 N for Periguard, and 287.9+/-34.3 N for SIS. The suture retention strengths were: Marlex, 413.4+/-59.7 N/mm2; Periguard, 97.0+/-20.1 N/mm2; and SIS, 106.9+/-12.7 N/mm2. The burst strength of Marlex, Periguard and SIS were 476.7+/-50.8 N, 432.12+/-82.1 N, and 433.6+/-79.5 N respectively. CONCLUSIONS: All three materials provide adequate strength and suture-holding capacities to be of use in the repair of soft tissue defects.
| A comparison of the adsorption of three adhesive proteins to biomaterial surfaces
Fabrizius-Homan, D. J. and S. L. Cooper (1991), J Biomater Sci Polym Ed 3(1): 27-47.
Abstract: The adsorption of three cell adhesive proteins with known thrombogenic activity [fibrinogen (FGN), fibronectin (FN), and vitronectin (VN)] was quantified from mono-component protein solutions, from a quaternary-component protein solution, and from plasma and diluted plasma in order to compare their potential for adsorption to polymeric substrates from solutions of varying complexity. The surfaces studied included polyethylene (PE), silicone rubber (SR), Teflon-FEP (FEP), and two polyetherurethanes: one with a poly(tetramethylene oxide) soft segment (PTMO-PU) and one with a poly(ethylene oxide) soft segment (PEO-PU). The adsorption of these proteins from single-component solutions followed the Freundlich isotherm and the adhesive proteins showed similar trends in Freundlich parameters for surfaces of similar surface wettability. Adsorption from a quaternary-component solution composed of physiological molar ratios of the three proteins and human serum albumin (HSA) revealed a significant enrichment of adsorbed vitronectin as determined from ratios of the adsorbed surface fraction of each protein to its respective bulk fraction. The other proteins' adsorption was enriched to a lesser extent in the decreasing order of FGN greater than FN greater than HSA for all surfaces. The relative enrichment of VN from plasma was also high as compared with its bulk concentration, whereas the enrichment of FGN, FN, and HSA was much lower and of approximately the same magnitude. Compared with the three other proteins, VN showed a resistance to displacement from the polymer substrates as either the plasma concentration was increased or the length of contact with plasma and diluted plasma was increased.
| A complete dielectric response model for liquid water: a solution of the Bethe ridge problem
Emfietzoglou, D., F. A. Cucinotta, et al. (2005), Radiat Res 164(2): 202-11.
Abstract: We present a complete yet computationally simple model for the dielectric response function of liquid water over the energy-momentum plane, which, in contrast to earlier models, is consistent with the recent inelastic X-ray scattering spectroscopy data at both zero and finite momentum transfer values. The model follows Ritchie's extended-Drude algorithm and is particularly effective at the region of the Bethe ridge, substantially improving previous models. The present development allows for a more accurate simulation of the inelastic scattering and energy deposition process of low-energy electrons in liquid water and other biomaterials. As an example, we calculate the stopping power of liquid water for electrons over the 0.1-10 keV range where direct experimental measurements are still impractical and the Bethe stopping formula is inaccurate. The new stopping power values are up to 30-40% lower than previous calculations. Within the range of validity of the first Born approximation, the new values are accurate to within the experimental uncertainties (a few percent). At the low end, the introduction of Born corrections raises the uncertainty to perhaps approximately 10%. Thus the present model helps extend the ICRU electron stopping power database for liquid water down to about two orders of magnitude with a comparable level of uncertainty.
| A composite of hydroxyapatite with electrospun biodegradable nanofibers as a tissue engineering material
Ito, Y., H. Hasuda, et al. (2005), J Biosci Bioeng 100(1): 43-9.
Abstract: Biodegradable and biocompatible poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a copolymer of microbial polyester, was fabricated as a nanofibrous film by electrospinning and composited with hydroxyapatite (HAp) by soaking in simulated body fluid. Compared with a PHBV cast (flat) film, the electrospun PHBV nanofibrous film was hydrophobic. However, after HAp deposition, both of the surfaces were extremely hydrophilic. The degradation rate of HAp/PHBV nanofibrous films in the presence of polyhydroxybutyrate depolymerase was very fast. Nanofiber formation increased the specific surface area and HAp enhanced the invasion of enzyme into the film by increasing surface hydrophilicity. The surface of the nanofibrous film showed enhanced cell adhesion over that of the flat film, although cell adhesion was not significantly affected by the combination with HAp.
| A computational approach to predicting cell growth on polymeric biomaterials
Abramson, S. D., G. Alexe, et al. (2005), J Biomed Mater Res A 73(1): 116-24.
Abstract: A predictive model that can correlate the chemical composition of a biomaterial with the biological response of cells that are in contact with that biomaterial would represent a major advance and would facilitate the rational design of new biomaterials. As a first step toward this goal, we report here on the use of Logical Analysis of Data (LAD) to model the effect of selected polymer properties on the growth of two different cell types, rat lung fibroblasts (RLF, a transformed cell line), and normal foreskin fibroblasts (NFF, nontransformed human cells), on 112 surfaces obtained from a combinatorially designed library of polymers. LAD is a knowledge extraction methodology, based on using combinatorics, optimization, and Boolean logic. LAD was trained on a subset of 62 polymers and was then used to predict cell growth on 50 previously untested polymers. Experimental validation indicated that LAD correctly predicted the high and low cell growth polymers and found optimal ranges for polymer chemical composition, surface chemistry, and bulk properties. Particularly noteworthy is that LAD correctly identified high-performing polymer surfaces, which surpassed commercial tissue culture polystyrene as growth substratum for normal foreskin fibroblasts. Our results establish the feasibility of using computational modeling of cell growth on flat polymeric surfaces to identify promising "lead" polymers for applications that require either high or low cell growth.
| A computer-assisted in-vitro biomaterial test for percutaneous devices using human keratinocyte cultures
Knabe, C., C. Grosse-Siestrup, et al. (1997), J Mater Sci Mater Med 8(9): 577-82.
Abstract: The aim of this study was to assess the suitability of a computer-assisted in vitro test system to evaluate candidate biomaterials used for percutaneous devices. Silicone rubber (Silastic) and five different polymers from the Eurobiomat concerted action, polyetherurethane, polyvinylchloride with plasticizer, di-ethylhexylphthalate (PVC-DEHP), polyvinylchloride with plasticizer, tri-ethylhexyltrimellitate (PVC-TEHTM), polyethylene and polypropylene were examined with respect to their qualities to facilitate keratinocyte attachment. HaCaT-cells, a spontaneously transformed non-tumorigenic human keratinocyte cell line, were cultured on the different materials for 3 days. Cellular behaviour was examined morphologically by phase-contrast and scanning electron microscopy throughout the 72 h incubation period. For the computer-assisted measurement of the cell-covered substrate surface and subsequent statistical analysis the cells were fixed after 3 days of incubation, stained, photographed and the images then digitally transformed. Of the different polymers examined silicone rubber showed the most favourable results with respect to the quantitative analysis of the cell-covered substrate surface as well as concerning cytomorphological findings. The results of this study indicate that the in vitro test system described is a sensitive screening method for evaluating candidate biomaterials used for percutaneous devices in a fast and reproducible manner, thus reducing number of animal experiments.
| A conditioning lesion enhances sympathetic neurite outgrowth
Shoemaker, S. E., H. H. Sachs, et al. (2005), Exp Neurol 194(2): 432-43.
Abstract: Axonal regeneration can be influenced by a conditioning lesion (an axonal injury made prior to a second test lesion). Previously, sympathetic neurons in vivo were shown to respond to a conditioning lesion with decreased neurite outgrowth, in contrast to the enhanced outgrowth observed in all other peripheral neurons examined. The present experiments tested the effects of a conditioning lesion on neurite outgrowth in vitro from the superior cervical ganglion (SCG) and the impact of several factors on that response. Ganglia axotomized 1 week earlier and then explanted in Matrigel or collagen gel responded with a significant increase in neurite extension compared to sham-operated ganglia. A distal axotomy produced by unilateral removal of the salivary glands (sialectomy) caused an increase in neurite outgrowth similar to that of a proximal axotomy. These conditioning lesions induced both an increase in the rate of elongation, and, in the case of the proximally axotomized SCG, a shorter initial delay of outgrowth. The enhanced outgrowth following sialectomy was specific to the nerve containing the majority of axons projecting to the salivary glands, suggesting that the conditioning lesion effect is restricted to previously injured neurons. Deletion of the gene for leukemia inhibitory factor (LIF), a gene induced by axotomy, did not abolish the conditioning lesion effect in SCG explants or dissociated cell cultures. In conclusion, sympathetic neurons are capable of responding to a conditioning lesion with increased neurite outgrowth. The hypothesis that the neuronal cell body response to axotomy plays an important role in the conditioning lesion response is discussed.
| A cone-and-plate device for the investigation of platelet biomaterial interactions
Skarja, G. A., R. L. Kinlough-Rathbone, et al. (1997), J Biomed Mater Res 34(4): 427-38.
Abstract: A device based on the cone-and-plate flow geometry commonly employed for viscometry was developed for the investigation of cell-surface interactions. The cone-and-plate geometry is capable of generating uniform, constant shear-rate flow fields, and control of cone rotational speed allows for easy variation of fluid shear rate. The current design is adapted for use with any material that is available in the form of a flat plate (film or coating). It also allows for replicate samples (the same or different surfaces) to be evaluated simultaneously. The device was tested under varying flow conditions for its ability to measure platelet adhesion from suspensions of washed platelets containing red cells. Collagen- and albumin-coated polymer materials were used as "standard" surfaces of known platelet reactivity (high and low, respectively). Adhesion to the collagen-coated surface was measured over a range of shear rate from 0 to 300 s(-1) and times up to 15 min. Platelet adhesion was observed to increase with increasing shear rate and time. Adhesion was significantly higher in the presence of red cells as has been observed by others. Effective platelet diffusion coefficients, calculated from the data on adhesion to the collagen surface, increased with increasing shear rate. Very little platelet adhesion to the albumin-coated surface, known to be unreactive to platelets, was observed when measured over a 15 min time period at 300 s(-1) shear rate, indicating that the device itself does not stimulate the platelets in the flow field. The data generated provide validation for this device as a simple means of measuring cell adhesion under controlled flow conditions to any smooth surface available in flat plate form.
| A conservative approach to the nonsurgical rejuvenation of the face
Gordon, M. L. (2005), Dermatol Clin 23(2): 365-71.
Abstract: With ever-increasing frequency, dermatology patients are requesting information and treatments that improve the appearance of their skin. Corresponding to this trend, there is an ever-increasing number of products and procedures available that claim to aid in this pursuit. Finding a suitable regimen is a challenge for patients and physicians alike. Many different approaches may be helpful. This article outlines one general approach to choosing effective and safe treatments and procedures.
| A conserved trimerization motif controls the topology of short coiled coils
Kammerer, R. A., D. Kostrewa, et al. (2005), Proc Natl Acad Sci U S A 102(39): 13891-6.
Abstract: In recent years, short coiled coils have been used for applications ranging from biomaterial to medical sciences. For many of these applications knowledge of the factors that control the topology of the engineered protein systems is essential. Here, we demonstrate that trimerization of short coiled coils is determined by a distinct structural motif that encompasses specific networks of surface salt bridges and optimal hydrophobic packing interactions. The motif is conserved among intracellular, extracellular, viral, and synthetic proteins and defines a universal molecular determinant for trimer formation of short coiled coils. In addition to being of particular interest for the biotechnological production of candidate therapeutic proteins, these findings may be of interest for viral drug development strategies.
| A container for transporting small laboratory animals for magnetic resonance imaging
Zhan, H., T. Tada, et al. (2005), J Neurosci Methods 144(1): 143-6.
Abstract: We have constructed a simple container, consisting of a propylene tube, a High-Efficiency Particulate Aerosol (HEPA) filter and a rubber glove, for transporting small animals to magnetic resonance imaging (MRI) facilities that are located outside a pathogen-free environment. Results of pathogens analysis indicate that the container is able to prevent infection by several microorganisms. The quality of the MR images of mice and rats transported in, and imaged while in the container was satisfactory. This container can be useful for examinations that required the use of instruments located outside clean animal units, ensuring safety for both humans and animals.
| A contemporary snapshot of the use of hydroxyapatite coating in orthopaedic surgery
Shepperd, J. A. and H. Apthorp (2005), J Bone Joint Surg Br 87(8): 1046-9.
| A continuous damage random thresholds model for simulating the fracture behavior of nacre
Nukala, P. K. and S. Simunovic (2005), Biomaterials 26(30): 6087-98.
Abstract: This study investigates the fracture properties of nacre using a discrete lattice model based on continuous damage random threshold fuse network. The discrete lattice topology of the model is based on nacre's unique brick and mortar microarchitecture. The mechanical behavior of each of the bonds in the discrete lattice model is governed by the characteristic modular damage evolution of the organic matrix and the mineral bridges between the aragonite platelets. The numerical results obtained using this simple discrete lattice model are in very good agreement with the previously obtained experimental results, such as nacre's stiffness, tensile strength, and work of fracture. The analysis indicates that nacre's superior toughness is a direct consequence of ductility (maximum shear strain) of the organic matrix in terms of repeated unfolding of protein molecules, and its fracture strength is a result of its ordered brick and mortar architecture with significant overlap of the platelets, and shear strength of the organic matrix.
| A descriptive study on retrieved non-threaded and threaded implant designs
Bolind, P. K., C. B. Johansson, et al. (2005), Clin Oral Implants Res 16(4): 447-55.
Abstract: OBJECTIVES: In the light microscope compare the amount of bone saucerization for non-threaded cylindrical and threaded implant designs in retrieved samples from patients. MATERIAL AND METHOD: Consecutively received retrieved oral implants from 117 patients, whereof 85 non-threaded cylindrical and 85 Branemark implants, have been included in the study. For 75 non-threaded cylindrical and 46 Branemark implants was the entire implant length available for calculation. Undecalcified ground sections were investigated in the light microscope with calculation of percentage of implant length coronal to the first bone-implant contact and percentage of bone to implant contact. RESULTS: Mean value for implant length coronal to first bone-implant contact was 65%, standard error of the mean (SEM) 3 (range 0-100%), for non-threaded cylindrical implants and 43%, SEM 6 (range 0-100%) for Branemark implants. Mean values of bone contact along the entire implant length was 23%, SEM 2 (range 0-65%), for the non-threaded cylindrical implants and 33%, SEM 5 (range 0-93%) for the Branemark implants. CONCLUSION: Within the limitations of this retrospective, retrieval study non-threaded cylindrical implants demonstrated a greater bone saucerization when evaluated in the light microscope.
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