|Articles about Biomaterials|
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| Combined effects of zoledronic acid and doxorubicin on breast cancer cell invasion in vitro
Woodward, J. K., H. L. Neville-Webbe, et al. (2005), Anticancer Drugs 16(8): 845-54.
Abstract: The bisphosphonate zoledronic acid and the cytotoxic drug doxorubicin induce synergistic levels of apoptosis in breast cancer cells. As zoledronic acid and doxorubicin have been shown to reduce cell invasion and migration, we have investigated if these drugs also act synergistically on breast cancer invasion in vitro. MCF7 cells were treated with 0.05 microM doxorubicin/4 h followed by 1 or 10 microM zoledronic acid/24 h (or the reverse sequence). To study invasion, MCF7 cells were either grown on Transwell membranes coated with Matrigel or in a 24-well plate. Cells were treated sequentially using the above drug combinations, prior to starting the invasion assays for 48 h. Cell growth and death were also assessed under the same conditions. We found that invasion of MCF7 cells treated with zoledronic acid and doxorubicin was significantly reduced when compared with control, but the effect was dependent on drug sequence. At 1 microM, zoledronic acid significantly reduced invasion only if cells were pre-treated with doxorubicin, but cell growth was unaffected. For 10 microM zoledronic acid, invasion was reduced when administered before or after the doxorubicin, but this dose of zoledronic acid caused a significant reduction in MCF7 growth. Apoptosis was not induced by any of the drug doses and combinations. We conclude that pre-treatment with 0.05 microM doxorubicin followed by 1 microM zoledronic acid reduces invasion when cells were grown on Matrigel. For 10 microM zoledronic acid, pre- or post-doxorubicin also reduces invasion, but for this combination inhibition of cell growth may contribute to the reduction in invasion observed.
| Combined microscale mechanical topography and chemical patterns on polymer cell culture substrates
Charest, J. L., M. T. Eliason, et al. (2006), Biomaterials 27(11): 2487-94.
Abstract: This paper presents a technique to independently form mechanical topography and surface chemical patterns on polymer cell substrates, and studies the response of osteoblast cells to these surface patterns. The patterns were formed in two separate steps: hot embossing imprint lithography formed the mechanical topography and microcontact printing created the chemical pattern. The resulting substrate had surface features consisting of embossed grooves 4mum deep and 8mum wide spaced by 16mum wide mesas and microcontact printed adhesive lanes 10mum wide with spacings that ranged from 10 to 100mum. When presented with either mechanical topography or chemical patterns alone, the cells significantly aligned to the pattern presented. When presented with mechanical topography overlaid with an orthogonal chemical pattern, the cells aligned to the mechanical topography. As the chemical pattern spacing was increased, osteoblasts remained aligned to the mechanical topography. Unlike traditional microfabrication approaches based on photolithography and wet chemistry, the patterning technique presented is compatible with a large number of biomaterials, could form patterns with features much smaller than 1mum, and is highly scalable to large substrates.
| Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media
Nakajima, T., Y. H. Xu, et al. (2005), J Hazard Mater 120(1-3): 75-80.
Abstract: A novel method for the removal of inorganic arsenic(III) (As(III)), monomethylarsonate (MMA), and dimethylarsinate (DMA) from aqueous media, was proposed and investigated. This method involves the combined use of TiO2-photocatalyst and an adsorbent, which has a high ability of As(V) adsorption, under photo-irradiation. When an aqueous solution of As(III) was stirred and irradiated by sunlight or xenon lamp in the presence of TiO2 suspension, the oxidation of As(III) into As(V) was effectively attained. By use of the same photocatalytic reaction, MMA and DMA were also degraded into As(V), while the total organic carbon (TOC) in the aqueous phase was decreased. When an aqueous solution of As(III) was stirred with a mixed suspension of TiO2 and an adsorbent for As(V) (activated alumina) under sunlight irradiation, the arsenic removal reached 89% after 24 h. By use of the same photocatalyst-adsorbent system, 98% of MMA and 97% of DMA were removed. The mechanism of the removal of arsenic species by the photocatalyst-adsorbent system was discussed.
| Combining novel biomolecules and stimuli-sensitive biomaterials into new recognition-response biomaterial systems
Hoffman, A. S. (1988), Artif Organs 12(6): 504-5.
Abstract: An important present and emerging trend in biomaterials development is the synthesis of polymers which combine capabilities of biologic recognition ("biomimetic") with sensitivity to small environmental changes ("stimuli-responsive"). This short article highlights some of the many opportunities and challenges in this exciting area.
| Comments on cell adhesion to biomaterial surfaces: conflicts and concerns
Baier, R. E. (1982), J Biomed Mater Res 16(2): 173-5.
| Comments on cell adhesion to biomaterial surfaces: the origin of saturation in platelet deposition--is it kinetic or thermodynamic?
Ruckenstein, E. and R. Srinivasan (1982), J Biomed Mater Res 16(2): 169-72.
| Comments on the measurement of height of cells adherent to biomaterial surfaces
Goodman, S. L. (1993), Biomaterials 14(7): 556-8.
| Comments on the origin of platelet deposition and on cell adhesion to biomaterial surfaces
Neumann, A. W., D. W. Francis, et al. (1983), J Biomed Mater Res 17(2): 375-81.
| Compactibility study of calcium phosphate biomaterials
Nicolazo, C., H. Gautier, et al. (2003), Biomaterials 24(2): 255-62.
Abstract: This study investigated the micromechanism responsible for the densification and consolidation of powders during dynamic compaction, an experimental process in which ceramic is formed without heating. Three calcium-deficient apatites (CDA: two powders and a fibrous compound) and a biphasic calcium phosphate (BCP) were studied to determine their aptitude (rheological and physical properties) for compactibility under various dynamic compaction pressures. Powders were investigated for their physicochemistry, particle size, and flow time, and compacts for their compaction rate, density, specific area, mechanical characteristics, and disintegration time. Powder particles showed different morphological features depending on the synthesis protocol used, specific area and rheological behaviour. Compacts were not obtained with BCP, regardless of the gas pressure used, whereas CDA produced compacts with good mechanical properties (high hardness and compression stress), particularly for the fibrous compound. The poor compressibility and compactibility of BCP powders were confirmed, whereas fibrous CDA powders showed good compactibility conducive to high-quality filling of biomaterials.
| Comparative analysis of different collagen-based biomaterials as scaffolds for long-term culture of human fibroblasts
Vaissiere, G., B. Chevallay, et al. (2000), Med Biol Eng Comput 38(2): 205-10.
Abstract: Biodegradable scaffolds, along with cells, are important components of most tissue-engineered constructs. In the study, there is a comparison of the behaviour of human fibroblasts cultured for up to six weeks in four different collagen-based three-dimensional matrices, in the form of sponges composed of pure native type I collagen (control), of collagen-GAG-chitosan (CGC) and of collagen cross-linked by two concentrations of diphenylphosphorylazide (DPPA-2 and DPPA-3). Variations in size and weight of the sponges, as well as fibroblast growth and migration, and total protein and collagen synthesis, are determined with time in culture. Owing to their low thermal stability, the partial denaturation and dissolution of the control sponges after incubation at 37 degrees C lead to considerable contraction and low cell proliferation. CGC sponges, stabilised by ionic interactions between the different components, show, after six weeks, limited contraction (20%) and weight increase (10% when seeded) and high cell growth (threefold increase). Similar results are obtained with weakly, cross-linked (DPPA-2) collagen sponges. Highly cross-linked (DPPA-3) sponges do not contract, whereas weight gain and cell proliferation are no different from those found with CGC and DPPA-2 sponges. Similar levels of total protein and collagen synthesis are shown for fibroblasts seeded in different matrices, with a slight general decrease (twofold) after three weeks, a much lower value than that observed with fibroblasts in culture within a contracted collagen gel (sixfold). Furthermore, the fraction of neo-synthesised collagen deposited in the sponges after six weeks represents more than 60% of the total, compared with only 10% obtained with fibroblasts in monolayer culture or 30% within a collagen gel. These results indicate that the matrices, particularly the CGC and DPPA-2 sponges, provide excellent supports for fibroblast growth and the formation of dermal and skin equivalents.
| Comparative analysis of sequence-specific DNA recombination systems in human embryonic stem cells
Tan, S. M. and P. Droge (2005), Stem Cells 23(7): 868-73.
Abstract: The great potential of human embryonic stem cells (hESCs) in basic research, regenerative medicine, and gene therapy is widely recognized. Controlled manipulation of hESC genomes through sequence-specific DNA recombination (SSR) may play a significant role in future hESC applications. However, very little is known about the functionality of SSR systems in hESCs. We demonstrate here that mutant phage lambda integrase, phage P1 Cre recombinase, and mutant gammadelta resolvase displayed distinct activities on episomal recombination substrates. Interestingly, cofactor-independent lambda integrase catalyzed the integrative pathway five times more efficiently than the excisive pathway. Such a degree of directionality in hESCs could be explored for sequential gene insertions into predetermined genomic sequences. We also report an improved, easy-to-use plasmid transfection system that employs silica microspheres and, in combination with SSR, could be applied to hESC genome engineering.
| Comparative assessment of ureteral stent biomaterial encrustation
Tunney, M. M., P. F. Keane, et al. (1996), Biomaterials 17(15): 1541-6.
Abstract: Long-term use of ureteral stents is hindered by the inherent problem of biomaterial encrustation which may lead to stone formation and attendant problems. The wide variety of polymeric biomaterials currently used for stent fabrication suggests that no single material is significantly superior to the others at resisting encrustation. A model representing upper urinary tract conditions was employed to compare the long-term struvite and hydroxyapatite encrustation of five materials currently used in the fabrication of ureteral stents. Silicone was least prone to struvite encrustation, followed by polyurethane, silitek, percuflex and hydrogel-coated polyurethane, in rank order. Similarly, silicone was least prone to hydroxyapatite encrustation, followed by silitek, polyurethane, percuflex and hydrogel-coated polyurethane. This study has shown that the problem of encrustation may limit the long-term use of ureteral stent biomaterials and suggests directions for improvement of biomaterials in this regard.
| Comparative efficacy of 2 different demineralized bone matrix allografts in treating long-bone nonunions in heavy tobacco smokers
Ziran, B., S. Cheung, et al. (2005), Am J Orthop 34(7): 329-32.
Abstract: Smoking impairs bone healing and increases the risk for complications associated with nonunions. The efficacies of 2 different allografts, Grafton (demineralized bone matrix [DBM] in a gel-like glycerol carrier) and Orthoblast (DBM with a reverse thermal poloxamer carrier) were examined with respect to nonunions in patients who reported heavy tobacco use. The Grafton allograft was used in 25 patients, and the Orthoblast allograft was used in 13 patients. All patients smoked more than half a pack of cigarettes a day and did not use electric stimulators. A successful graft was defined as healing on the first graft attempt without complications or later regraft. The Grafton and Orthoblast success rates were 52% and 85%, respectively (P =.077). The unique thermal properties of the Orthoblast reverse poloxamer, which may enhance DBM osteoinduction, may account for the difference in success rates. Although results failed to reach statistical significance, the large difference and high likelihood ratio (4.2) between the 2 groups suggest that perhaps not all commercially available allografts may necessarily perform with the same efficacy with respect to heavy smokers.
| Comparative evaluation of decalcified and non-decalcified freeze-dried bone allografts in rhesus monkeys. I. Histologic findings
Yukna, R. A. and S. Vastardis (2005), J Periodontol 76(1): 57-65.
Abstract: BACKGROUND: Controversy exists regarding the relative merits of decalcified (DFDBA) and non-decalcified (FDBA) freeze-dried bone allografts when used in periodontal or other oral surgical procedures. METHODS: Under typical sedation, six rhesus monkeys had nylon mesh cylinders containing either DFDBA or FDBA implanted into surgically created vertical grooves on the facial aspects of all posterior quadrants. Each quadrant received three cylinders containing one type of bone, plus one empty cylinder (E) as negative control, and the full thickness flaps were closed to completely cover the cylinders. Cylinders were retrieved at 1, 2, and 3 months and processed for histologic evaluation. Photomicrographs taken at 8x were randomly evaluated using a histometric grid point counting technique for new bone and old bone within the chambers, and the data were analyzed with analysis of variance plus post-tests. RESULTS: The nylon chambers and their contents were well-tolerated by the tissues. FDBA chambers contained more new bone and total bone than either the DFDBA or E chambers at all time periods (P <0.05). DFDBA was not statistically significantly different than E at any time period. FDBA had less old bone than DFDBA at 3 months (P<0.05). FDBA and DFDBA had more total bone (grafted plus new) present than E at all time periods (P<0.05). CONCLUSION: These results suggest that FDBA may stimulate earlier, more rapid, and more substantial new bone formation than DFDBA in a monkey jaw defect model system.
| Comparative histopathologic study of various lens biomaterials in primates after Nd:YAG laser treatment
Hansen, S. O., D. J. Apple, et al. (1987), J Cataract Refract Surg 13(6): 657-61.
Abstract: A Nd:YAG laser was used to perform posterior capsulotomies on primates in whom one-piece silicone or three-piece polymethylmethacrylate intraocular lenses were in place for more than one year. The eyes were followed for eight weeks after treatment before enucleation. Histologically, no toxic effects caused by the dispersion of any of the biomaterial within the eyes and no significant inflammatory reactions were seen. The silicone lenses used in this study compared favorably with traditional polymethylmethacrylate lenses when posterior capsulotomies with a Nd:YAG laser were performed.
| Comparative in vitro encrustation studies of biomaterials in human urine
Gleeson, M. J., J. A. Glueck, et al. (1989), ASAIO Trans 35(3): 495-8.
Abstract: A new dynamic in vitro human urine model was developed to compare biomaterial encrustation. The model incorporates a capacity to study seven biomaterials, a daily urine inflow of 500 ml, a reservoir capacity of 700 ml, and a turnover rate of four days. Encrustation studies performed for 2 weeks in sterile and infected (Proteus Vulgaris) urine on segmented polyether polyurethane, polyester polyurethane, silicone (Mitsui), silicone (Dow Corning), biothane, biolor 1 and biolor 11 demonstrated that biolor 11 (silicone-carbon composite) caused the least encrustation. Encrustation analysis showed brushite in the sterile model and struvite and ammonium acid urate in the infected mode I. Biolor II should have beneficial applications in catheters, stents and prosthetics which come in contact with urine.
| Comparative in vitro study on a ultra-high roughness and dense titanium coating
Borsari, V., G. Giavaresi, et al. (2005), Biomaterials 26(24): 4948-55.
Abstract: A new implant surface has been developed with the purpose of avoiding as much stress shielding as possible, and thus prolong the prosthesis lifespan. The aim of this study was to investigate the in vitro effect of this new ultra-high roughness and dense Titanium (Ti) surface (PG60, Ra = 74 microm) in comparison with medium (TI01, Ra = 18 microm) and high (TI60, Ra = 40 microm) roughness and open porous coatings; all the coatings were obtained by vacuum plasma spraying. MG63 osteoblast-like cells were seeded on the tested materials and polystyrene, as control, for 3 and 7 days. Cells proliferated on the material surfaces similarly to the control. Alkaline phosphatase activity had lower values for TI60 than TI01 (p < 0.0005) and PG60 (p < 0.005). Osteocalcin levels measured on TI60 were significantly (p < 0.0005) lower in comparison with TI01 and PG60 at 7 days. Procollagen-I synthesis reduced with increasing roughness and the lowest data was found for PG60. While at 3 days Transforming Growth Factor beta1 levels augmented with increasing roughness, at 7 days TI60, the high roughness surface, was significantly lower than PG60 (p < 0.005) and TI01 (p < 0.001). All tested materials showed significantly higher Interleukin-6 levels than those of polystyrene at both experimental times. Nitric Oxide activity on TI01 was significantly (p < 0.05) higher than on TI60 and polystyrene. In conclusion, the new ultra-high roughness and dense coating PG60 provided a good biological response, even though, at least in vitro, it behaved similarly to the coatings already used in orthopaedics.
| Comparative investigation of alloplastic materials for hernia repair with improved methodology
Kapischke, M., K. Prinz, et al. (2005), Surg Endosc 19(9): 1260-5.
Abstract: BACKGROUND: A variety of alloplastic materials are used for hernia repair. We discuss the long-term stability and possible shrinkage of these materials. In the past, measurement of pore sizes was used to study the physical properties of alloplastic meshes. The aim of this study was to evaluate the measurement of pore sizes with regard to its correlation to possible mesh alteration. METHODS: The water absorption of different polypropylene (PP) and polyester (PE) mesh materials under defined conditions was studied. For shrinkage studies, meshes were stored in formaldehyde, distilled water, saline solution, trypsin solution, urea solution, and hydrogen peroxide. The measurement of the relation between material and pore was evaluated to investigate the potential shrinking and enlargement processes. This material-pore index (MPI) before as well as 1, 7, and 14 days after incubation was measured. RESULTS: In comparison to measuring single pore sizes, MPI determination is the more efficient method to evaluate the possible shrinking or enlargement processes of alloplastic materials. With this technique, incorrect determination of pore sizes due to the dynamic textile structure of meshes and to shrinkage or enlargement, is excluded. All tested alloplastic materials showed an insignificant increase in water absorption under the condition of rehydration up to 0.4%. We did not observe variances in the material in shrinking or enlargement. CONCLUSIONS: MPI was found to be more reliable than measuring single pores to investigate possible external influences on polymer materials. Biomaterials such as PP and PE proved to be absolutely inert under various in vitro conditions.
| Comparative study of acetic acid, methanol, and water adsorbed on anatase TiO2 probed by sum frequency generation spectroscopy
Wang, C. Y., H. Groenzin, et al. (2005), J Am Chem Soc 127(27): 9736-44.
Abstract: Sum frequency generation (SFG) vibrational spectroscopy is used to investigate the surface adsorption of three probe molecules-acetic acid, methanol, and water--on a film composed of nanoscale anatase TiO(2) particles. On the TiO(2) surface, only one adsorption mode, chemisorption, is observed for acetic acid. This is evidenced by one sharp SFG peak in the C-H region, which is stable with time and robust both to evacuation and to the addition of water. A Langmuir constant of (9.21 +/- 0.71) x 10(3) is determined from the adsorption isotherm. In the case of methanol adsorption, however, there are two adsorption modes, molecular physisorption and dissociative chemisorption. The corresponding SFG signals are stable with time but diminished with addition of water. Changes in the SFG features for methanol and for the methoxy species with addition of water and subsequent evacuation provide the first experimental proof of reversible hydroxylation and dehydroxylation at the TiO(2) surface. For water adsorption, only one mode, physisorption, is observed on the hydroxylated TiO(2) surface. The water adlayer is mobile, as is evidenced by variation of the water H-bonded SFG signal with time. Competitive adsorption among the three molecular probes is clearly resolved by in situ SFG measurements. The adsorption strength follows the order acetic acid (strongest), methanol, water (weakest). The adsorption order as well as the difference in response of methanol versus acetic acid adsorption to addition of water has direct implications for understanding TiO(2) photocatalysis as well as the surface modifications involved in TiO(2) photoelectrochemical solar cells and processes in TiO(2) nanomaterial synthesis and assembly.
| Comparative study of DNA encapsulation into PLGA microparticles using modified double emulsion methods and spray drying techniques
Oster, C. G. and T. Kissel (2005), J Microencapsul 22(3): 235-44.
Abstract: Recently, several research groups have shown the potential of microencapsulated DNA as adjuvant for DNA immunization and in tissue engineering approaches. Among techniques generally used for microencapsulation of hydrophilic drug substances into hydrophobic polymers, modified WOW double emulsion method and spray drying of water-in-oil dispersions take a prominent position. The key parameters for optimized microspheres are particle size, encapsulation efficiency, continuous DNA release and stabilization of DNA against enzymatic and mechanical degradation. This study investigates the possibility to encapsulate DNA avoiding shear forces which readily degrade DNA during this microencapsulation. DNA microparticles were prepared with polyethylenimine (PEI) as a complexation agent for DNA. Polycations are capable of stabilizing DNA against enzymatic, as well as mechanical degradation. Further, complexation was hypothesized to facilitate the encapsulation by reducing the size of the macromolecule. This study additionally evaluated the possibility of encapsulating lyophilized DNA and lyophilized DNA/PEI complexes. For this purpose, the spray drying and double emulsion techniques were compared. The size of the microparticles was characterized by laser diffractometry and the particles were visualized by scanning electron microscopy (SEM). DNA encapsulation efficiencies were investigated photometrically after complete hydrolysis of the particles. Finally, the DNA release characteristics from the particles were studied. Particles with a size of <10 microm which represent the threshold for phagocytic uptake could be prepared with these techniques. The encapsulation efficiency ranged from 100-35% for low theoretical DNA loadings. DNA complexation with PEI 25?kDa prior to the encapsulation process reduced the initial burst release of DNA for all techniques used. Spray-dried particles without PEI exhibited high burst releases, whereas double emulsion techniques showed continuous release rates.
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