|Articles about Biomaterials|
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| An innovative auto-catalytic deposition route to produce calcium-phosphate coatings on polymeric biomaterials
Leonor, I. B. and R. L. Reis (2003), J Mater Sci Mater Med 14(5): 435-41.
Abstract: The aim of this research is to develop a new methodology to obtain bioactive coatings on bioinert and biodegradable polymers that are not intrinsically bioactive. In this study three types of materials were used as substrates: (i) high molecular weight polyethylene (HMWPE) and two different types of starch based blends (ii) starch/ethylene vinyl alcohol blends, SEVA-C and (iii) starch/cellulose acetate blends, SCA. Two types of baths were originally proposed and studied to produce novel auto-catalytic calcium-phosphate (Ca-P) coatings. Then, the coated surfaces were analyzed by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), as produced, and after different immersion periods in SBF. The evolution of Ca and P concentrations was determined by induced-coupled plasma emission (ICP) spectroscopy. The crystalline phases present on the films formed on the different material surfaces, after a certain soaking time, were identified by thin-film X-ray diffraction (TF-XRD). The obtained results indicated that it was possible to coat the materials surfaces with a Ca-P layer with only 60 min of immersion in both types of auto-catalytic solutions. Furthermore, it was possible to observe the clear bioactive nature of the Ca-P coatings after different immersion periods in a simulated body fluid (SBF). The results from TF-XRD confirmed the presence of partially amorphous Ca-P films with clearly noticeable hydroxylapatite peaks. These new methodologies allow for the production of an adherent bioactive film on the polymeric surfaces prior to implantation, which may allow for the development of bone-bonding, bioabsorbable implants and fixation devices.
| An interfacial instability in a transient wetting layer leads to lateral phase separation in thin spin-cast polymer-blend films
Heriot, S. Y. and R. A. Jones (2005), Nat Mater 4(10): 782-6.
Abstract: Spin-coating is a very widely used technique for making uniform thin polymer films. For example, the active layers in most experimental semiconducting polymer-based devices, such as light-emitting diodes and photovoltaics, are made this way. The efficiency of such devices can be improved by using blends of polymers; these phase separate during the spin-coating process, creating the complex morphology that leads to performance improvements. We have used time-resolved small-angle light scattering and light reflectivity during the spin-coating process to study the development of structure directly. Our results provide evidence that a blend of two polymers first undergoes vertical stratification; the interface between the stratified layers then becomes unstable, leading to the final phase-separated thin film. This has given us the basis for establishing a full mechanistic understanding of the development of morphology in thin mixed polymer films, allowing a route to the rational design of processing conditions so as to achieve desirable morphologies by self-assembly.
| An introduction to Staphylococcus aureus, and techniques for identifying and quantifying S. aureus adhesins in relation to adhesion to biomaterials: review
Harris, L. G., S. J. Foster, et al. (2002), Eur Cell Mater 4: 39-60.
Abstract: The ability of Staphylococcus aureus to adhere to the extracellular matrix and plasma proteins deposited on biomaterials is a significant factor in the pathogenesis of orthopaedic-device related infections. S. aureus possesses many adhesion proteins on its surface, but it is not known how they interact with each other to form stable interactions with the substrate. A novel method was developed for extracting adhesins from the S. aureus cell wall, which could then be further analysed. The protocol involves using a FastPrep instrument to mechanically disrupt the cell walls resulting in native cell walls. Ionically and covalently bound proteins were then solubilised using sodium dodecyl sulphate (SDS) and lysostaphin, respectively. Western blot analysis of covalently bound proteins using anti-protein A and anti-clumping factor A sera showed that S. aureus produces most surface proteins in early growth, and less in post-exponential and stationary growth. Immuno-gold labelling of protein A, and clumping factor A was observed all over the bacteria and showed no distinct surface distribution pattern. However, this labelling showed expression of surface associated proteins varied in a growth-phase dependent and cell-density dependent manner.
| An introduction to the biomechanics and biomaterials of bone, joints, and implants
Pugh, J. (1976), Bull Hosp Joint Dis 37(2): 124-48.
Abstract: Biomechanics and biomaterials of bone, joints, and implants has been presented in an overview manner with the use of selected examples. The musculoskeletal system is a living, dynamic entity that is constructed so that changes in mechanics, if the body does not have time to compensate, can lead to major problems over a period of time. The mechanics of the tissues ensure a smoothly operating system.
| An inverted microcontact printing method on topographically structured polystyrene chips for arrayed micro-3-D culturing of single cells
Dusseiller, M. R., D. Schlaepfer, et al. (2005), Biomaterials 26(29): 5917-25.
Abstract: With the goal to investigate the relation of shape and function of single cells or clusters of cells in a 3-dimensional (3-D) microenvironment, we present a novel platform technology to create arrays of microwells on polystyrene (PS) chips for hosting cells in a local microenvironment characterized by controlled shape and surface chemistry. The micro-3-D cell culturing combines 2-dimensional chemical patterning with topographical microstructuring presenting to the cells a local 3-D host structure. Microwells of controlled dimensions were produced by a two-step replication process, based on standard microfabrication of Si, replica molding into poly(dimethylsiloxane), and hot embossing of PS. This allowed the production of large numbers of microstructured surfaces with high reproducibility and fidelity of replication. Using inverted micro contact printing, the plateau surface between the microwells was successfully passivated to block adsorption of proteins and prevent cell attachment by transfer of a graft-copolymer, poly(l-lysine)-g-poly(ethylene glycol). The surface inside the microwells was subsequently modified by spontaneous adsorption of proteins or functionalized PLL-g-PEG/PEG-X (X=biotin or specific, cell-interactive peptide) to elicit specific responses inside the wells. Preliminary cell experiments demonstrated the functionality of such a device to host single epithelial cells (MDCK II) inside the functionalized microwells and thus to control their 3-D shape. This novel platform is useful for fundamental cell-biological studies and applications in the area of cell-based sensing.
| An investigation of the cytotoxicity and histocompatibility of in situ forming lactic acid based orthopedic biomaterials
Burdick, J. A., R. F. Padera, et al. (2002), J Biomed Mater Res 63(5): 484-91.
Abstract: The cytotoxicity and biocompatibility of polymer networks prefabricated from multifunctional lactic acid based oligomers that are being developed for orthopedic applications were assessed through in vitro cytotoxicity analysis and subcutaneous implantation. After 7 and 14 days, no significant difference was observed in the relative viability or alkaline phosphatase activity of primary rat calvarial osteoblasts cultured in the presence or absence of degrading polymer networks, indicating that the degradation products had no detrimental effect on the function or activity of the cultured cells. The tissue response to preformed lactic acid networks implanted in rats consisted of a mild inflammatory response with an increase in fibrous capsule thickness and inflammation correlating with faster degrading polymer compositions. This relatively neutral response is indicative of a biocompatible, degradable polymer that has potential medical applications. Finally, porous scaffolds were implanted subcutaneously in rats, and vascularized fibrous tissue infiltration was highly dependent on the scaffold porosity and architecture. This finding indicates that an in situ forming porous scaffold of this composition may support the infiltration of surrounding vascularized tissue, and thus be applicable to orthopedic treatments of large bone defects.
| An in-vitro study of the sterilization of titanium dental implants using low intensity UV-radiation
Riley, D. J., V. Bavastrello, et al. (2005), Dent Mater 21(8): 756-60.
Abstract: OBJECTIVES: Commercial titanium dental implants are coated with nanostructured TiO2. The aim of the research reported in this paper was to assess whether the TiO2 at the surface of a dental implant is sufficiently photoactive to eradicate bacteria when illuminated with low intensity light. METHODS: The photoactivity of dental implants was established by studies of the photoenhanced decomposition of Rhodamine B. In vitro studies to establish the influence of irradiating with UV light an implant that is immersed in a solution containing Escherichia Coli were performed. RESULTS: It was demonstrated that under low UV intensity irradiation, 49 microW cm(-2), bacteria are killed at a rate of approximately 650 million per cm2 of implant per minute. SIGNIFICANCE: The results indicate that illumination of dental implants with UV light may be a suitable treatment for periimplantitis.
| An open channel flow chamber for characterizing biofilm formation on biomaterial surfaces
An, Y. H., J. B. McGlohorn, et al. (2001), Methods Enzymol 337: 79-88.
| An open, multicentre study of NASHA/Dx Gel (Zuidex) for the treatment of stress urinary incontinence
Chapple, C. R., F. Haab, et al. (2005), Eur Urol 48(3): 488-94.
Abstract: OBJECTIVE: The Zuidex system facilitates non-endoscopic urethral injection for stress urinary incontinence (SUI). It comprises four pre-filled syringes of non-animal stabilised hyaluronic acid/dextranomer (NASHA/Dx) gel and an Implacer device. This open, 12-month study was performed to evaluate the safety and efficacy of this system in women with SUI. METHODS: Patients were aged > or =18 years with a history of SUI for > or =12 months (hypermobility and/or intrinsic sphincter deficiency), had failed prior non-invasive therapy and were invasive-therapy naive. Up to two treatments with NASHA/Dx gel were permissible (re-treatment was offered at week 8). Positive response to treatment was defined as a reduction in provocation test leakage of > or =50% compared with baseline. Efficacy was also measured by 24-hour pad weight test leakage, and number of incontinence episodes/24 hours. RESULTS: A total of 142 patients were enrolled, with a mean age of 55.7 years. The response rate was 78% at week 12, and 77% at month 12. Significant reductions in median provocation test leakage, 24-hour pad-weight test leakage and number of incontinence episodes/24 hours were observed at all time-points. At month 12, the median decreases from baseline in these three variables were 93%, 89% and 67%, respectively. Treatment-related adverse events were of a nature expected with urethral injection - most were transient, and of mild or moderate intensity. CONCLUSIONS: Treatment with NASHA/Dx gel produced large, statistically significant reductions in urinary leakage sustained over 12 months and was well tolerated. These findings suggest that NASHA/Dx gel could be considered as an early intervention in treatment-naive cases of SUI.
| An open-label evaluation of HP-Guar gellable lubricant eye drops for the improvement of dry eye signs and symptoms in a moderate dry eye adult population
Hartstein, I., S. Khwarg, et al. (2005), Curr Med Res Opin 21(2): 255-60.
Abstract: OBJECTIVE: Evaluate the efficacy of a polymer hydroxypropyl guar (HP-Guar) gellable lubricant eye drop (Systane* Lubricant Eye Drops) in reducing dry eye signs and symptoms among dry eye patients who exhibited at least moderate signs and symptoms.METHODS: 168 patients with moderate dry eye signs and symptoms were enrolled at 29 sites in this open label study. The mean age of patients was 62 years with a minimum age of 28 years and a maximum of 90 years. One hundred and forty-seven patients completed the study, 111 female and 35 male, excluding 1 subject (gender not captured). In order to be included in the study, subjects were required to have a total corneal staining score > or = 4 (NEI grid) in at least one eye, with a grade > or = 2 in at least one zone of the same eye. Patients also had to indicate that their eyes 'felt dry enough to want to use eye drops' at least 'some of the time' on a standardized frequency scale. Eligible patients were dispensed a run-in drop (Opti-Free Express Rewetting Drops*) to use QID for 7 days, and then examined. Patients continuing to meet the inclusion criteria were dispensed the test drops (HP-Guar gellable lubricant eye drops) to use QID, and re-examined on Day 28. At each visit, corneal and conjunctival staining were measured, and six ocular discomfort symptoms were rated on a standardized 0-4 severity scale. At Days 0 and 28, patients subjectively rated product acceptability using a Likert scale. RESULTS: No significant changes in corneal or conjunctival staining were observed with the use of the run-in drop. After 28 days of test drop use, there was a statistically significant reduction in corneal staining (p < 0.0001). Ninety-four percent of patients improved from baseline, with mean reduction in total corneal staining of 4.1 units (0-15 total scale) (62%). Conjunctival staining also improved significantly (p < 0.0001) with a mean total reduction of 3.1 (59%). Patients experienced statistically significant symptomatic relief from day 0 to day 28 for all six ocular discomfort severity questions (p < 0.0001). CONCLUSION: Lubricating drops effectively relieved signs and symptoms associated with moderate dry eye, with measurable improvements evident in both objective staining and subjective questionnaire measures after 28 days in this study population.
| An organometallic synthesis of TiO2 nanoparticles
Tang, J., F. Redl, et al. (2005), Nano Lett 5(3): 543-8.
Abstract: We report the synthesis of TiO2 nanoparticles that uses the low-temperature reaction of low-valent organometallic precursors. Bis(cyclooctatetraene)titanium reacts with dimethyl sulfoxide in organic solution at temperatures as low as room temperature to produce TiO2. In the absence of any supporting ligand, the reaction gives precipitation of amorphous TiO2 powder; however, in the presence of basic ligands such as tributylphosphine, tributylphosphine oxide and trioctylphosphine oxide, the precipitation is arrested, and chemically distinct, isolated, internally crystalline TiO2 nanoparticles are formed.
| An overview of biomaterials
Schindhelm, K. and B. K. Milthorpe (1986), Australas Phys Eng Sci Med 9(1): 29-32.
| An ultrastructural study of root canal walls in contact with endodontic biomaterials
Guigand, M., J. M. Vulcain, et al. (1997), J Endod 23(5): 327-30.
Abstract: The aim of this in vitro study was to compare structural and ultrastructural changes to the unmineralized extracellular matrix after using two root canal restoration materials, one calcium hydroxide based and the other calcium oxide based. Pig teeth were restored with no preliminary root canal preparation. The filling materials were left in the root canals for 3, 8, 15, or 21 days. Observations were carried out by scanning electron microscopy. Results showed that when the calcium oxide-based material was used, it penetrated tubules and the unmineralized extracellular matrix material was reduced to a minimum. Teeth filled with the calcium hydroxide-based material were similar to control samples with an intact predentine. These observations suggest that the calcium oxide-based material induces changes in the unmineralized extracellular matrix of the endodontium.
| Analysis of biomaterials
Sabbatini, L. (2005), Anal Bioanal Chem 381(3): 529-30.
| Analysis of biomaterials deposited on soft contact lenses
Wedler, F. C. (1977), J Biomed Mater Res 11(4): 525-35.
Abstract: Formation of opaque deposits on the anterior (air) surface of hydrophilic soft contact lenses is a problem worthy of investigation by all concerned. These deposits have been analyzed for biomaterials by chemical, biochemical, electrophoretic, and immunological techniques. Qualitative and quantitative chemical colorimetric tests revealed the presence of variable amounts of protein (5-10 microgram/lens), carbohydrate (1.0-1.2 microgram/lens), and phospholipids (0.01-0.05 micronmole/lens). Cholesterol and glucose were not present at detectable levels. Fluorescent antibody tests with appropriate controls gave positive tests for albumin, lysozyme, gamma-G-globulin, and alpha1-lipoprotein in the deposits, all proteins present in tear fluid. Deposits were most effectively removed from the lenses by the combination of heat, sodium dodecyl sulfate (SDS) detergent, and the thiol reagent dithiothreitol (DTT). SDS-denatured protein migrated on polyacrylamide gels with electrophoretic patterns corresponding to molecular weights for those proteins detected by the above antibody tests. The nature of the bonding interactions of biomaterials to the lenses was probed by chemical reagents used to remove them, employed singly and in all possible combinations. Urea, guanidine hydrochloride, potassium thiocyanate, potassium perchlorate, hydroxylamine, and EDTA were much less effective than SDS and DTT. These data suggest that apolar interactions plus disulfide bonds may be important in stabilizing the deposit structure, and point to improved cleaning procedures.
| Analysis of captan on nitrile glove surfaces using a portable attenuated total reflection fourier transform infrared spectrometer
Phalen, R. N. and S. S. Que Hee (2005), Appl Spectrosc 59(6): 724-31.
Abstract: This study developed a method to produce uniform captan surface films on a disposable nitrile glove for quantitation with a portable attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometer. A permeation test was performed using aqueous captan formulation. Uniform captan surface films were produced using solvent casting with 2-propanol and a 25 mm filter holder connected to a vacuum manifold to control solvent evaporation. The coefficient of variation of the reflectance at 1735 +/- 5 cm(-1) was minimized by selection of the optimum solvent volume, airflow rate, and evaporation time. At room temperature, the lower to upper quantifiable limits were 0.31-20.7 microg/cm2 (r = 0.9967; p < or = 0.05) for the outer glove surface and 0.55-17.5 microg/cm2 (r = 0.9409; p < or = 0.05) for the inner surface. Relative humidity and temperature did not affect the uncoated gloves at the wavelength of captan analysis. Glove screening using ATR-FTIR was necessary as a control for between-glove variation. Captan permeation, after 8 hours exposure to an aqueous concentration of 217 mg/mL of Captan 50-WP, was detected at 0.8 +/- 0.3 microg/cm2 on the inner glove surface. ATR-FTIR can detect captan permeation and can determine the protectiveness of this glove in the field.
| Analysis of cell-seeded 3-dimensional bone constructs manufactured in vitro with hydroxyapatite granules obtained from red algae
Turhani, D., E. Watzinger, et al. (2005), J Oral Maxillofac Surg 63(5): 673-81.
Abstract: PURPOSE: Bone tissue engineering is a promising approach for the treatment of defective or lost bone in the maxillofacial region. Biocompatible and biodegradable scaffolds seeded with living cells are used to create functional tissue for load-bearing bone reconstruction. The aim of this study was to manufacture cell-seeded 3-dimensional bone constructs based on hydroxyapatite ceramic granule calcified from red algae and mesenchymal cambial-layer precursor cells. The ability of these cells to grow on hydroxyapatite ceramic was quantitatively investigated to evaluate 3-dimensional bone constructs for their potential use in bone tissue engineering. MATERIALS AND METHODS: Mesenchymal cambial-layer precursor cells were isolated from mandibular periosteum biopsy samples of 3 patients. To manufacture 72 bone constructs, these cells and hydroxyapatite ceramic granules (C GRAFT/Algipore; Clinician's Preference LLC, Golden, CO) were cultivated under osteogenic differentiation conditions in a rotating wall vessel system. After 6 and 21 days, histologic examination and scanning electron microscopy were performed. The absolute DNA content, protein synthesis, and alkaline phosphatase activity were also quantified. The osteoblastic phenotype of the constructs was confirmed by the expression of bone-specific genes (osteocalcin, osteonectin, osteopontin, and core binding factor alpha1) using semiquantitative reverse transcription-polymerase chain reaction and Western blot analysis. RESULTS: Cells within the constructs showed good viability, which was evidenced by an increase in DNA content over the culture period. The decrease in alkaline phosphatase-specific activity could be an indicator of the maturation of cells and the induction of mineralization. The osteoblastic phenotype of the constructs was demonstrated on protein and at the RNA level over the entire culture period. CONCLUSION: We observed a positive effect of hydroxyapatite ceramic granules on mesenchymal cambial-layer precursor cell behavior in cell-seeded 3-dimensional bone constructs, indicating the potential applicability of C GRAFT/Algipore composites in bone tissue engineering.
| Analysis of failed commercially pure titanium dental implants: a scanning electron microscopy and energy-dispersive spectrometer x-ray study
Shibli, J. A., E. Marcantonio, et al. (2005), J Periodontol 76(7): 1092-9.
Abstract: BACKGROUND: The failure of osseointegration in oral rehabilitation has gained importance in current literature and in clinical practice. The integration of titanium dental implants in alveolar bone has been partly ascribed to the biocompatibility of the implant surface oxide layer. The aim of this investigation was to analyze the surface topography and composition of failed titanium dental implants in order to determine possible causes of failure. METHODS: Twenty-one commercially pure titanium (cpTi) implants were retrieved from 16 patients (mean age of 50.33 +/- 11.81 years). Fourteen implants were retrieved before loading (early failures), six after loading (late failures), and one because of mandibular canal damage. The failure criterion was lack of osseointegration characterized as dental implant mobility. Two unused implants were used as a control group. All implant surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive spectrometer x-ray (EDS) to element analysis. Evaluations were performed on several locations of the same implant. RESULTS: SEM showed that the surface of all retrieved implants consisted of different degrees of organic residues, appearing mainly as dark stains. The surface topography presented as grooves and ridges along the machined surface similar to control group. Overall, foreign elements such as carbon, oxygen, sodium, calcium, silicon, and aluminum were detected in failed implants. The implants from control group presented no macroscopic contamination and clear signs of titanium. CONCLUSION: These preliminary results do not suggest any material-related cause for implant failures, although different element composition was assessed between failed implants and control implants.
| Analysis of mesenchymal stem cells grown on a three-dimensional HYAFF 11-based prototype ligament scaffold
Cristino, S., F. Grassi, et al. (2005), J Biomed Mater Res A 73(3): 275-83.
Abstract: Ligaments are complex structures that maintain the mechanical stability of the joint. Healing of injured ligaments involves the interactions of different cell types, local cellular environment, and the use of devices. To gain new information on the complex interactions between mesenchymal stem cells (MSCs) and a specific hyaluronan-based prototype scaffold (HYAFF, useful for ligament tissue engineering, short time-course experiments were performed to analyze the proliferation, vitality, and phenotype of MSCs grown on the scaffold. MSC proliferation was analyzed using the MTT test, during the early time points (2, 4, 6, days). Viability was assessed using calcein/acetyloxymethylester immunofluorescence dye and confocal microscopy analysis. Hyaluronic acid receptor (CD44), typical matrix ligament proteins (collagen type I, type III, laminin, fibronectin, actin), and chondrogenic/osteogenic markers (collagen type II and bone sialoprotein) were evaluated by immunohistochemistry. Our data demonstrated that MSC growth and viability were cell density-dependent. MSCs completely wrapped the fibers of the scaffold, expressed CD44, collagen type I, type III, laminin, fibronectin, and actin, and were negative to collagen type II and bone sialoprotein. These data demonstrate that MSCs survive well in the hyaluronan-based prototype ligament scaffold, as assessed after 2 days from seeding, and express CD44, a receptor important for scaffold interaction, and proteins responsible for the functional characteristics of the ligaments.
| Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials
Watts, D. C. and A. J. Cash (1994), J Dent 22(2): 112-7.
Abstract: The penetration of visible light into dental biomaterials is an essential factor in photoinitiation of setting reactions and in the optical aspects of dental aesthetics. Light of visible blue wavelengths, 400-500 nm, has been applied at normal angles to 0.2-5.0 mm sections of human dentine and representative ceramic, polymerceramic composites and hybrid glass-polyalkenoate materials. The integrated optical transmission has been determined for each material section. The data have been converted to absorbance values and analysed to check for mathematical conformity to the Beer-Lambert Law. It is found that conformity (typically, P < 0.01) to the linear Beer-Lambert Law is only attained by making a substantial correction for the intensity of light reflected from the surface of aesthetic biomaterials. This is otherwise expressed by distinguishing between true and apparent absorbance. From linear regression of apparent absorbance with section thickness, the intercept depends upon the logarithm of the surface-reflection ratio. This factor ranges from 30% to 90% in the materials investigated. It follows that there is a high degree of inefficiency in the transmission of visible light into and through aesthetic biomaterials for the purposes of photoactivation using existing technology. Means by which this limitation and inefficiency may be reduced are discussed. While the reflectivity of aesthetic biomaterials has been perceived by dental practitioners, the magnitude of this effect and its implications in connection with light-cured materials have not been analysed and emphasized hitherto.
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