|Articles about Biomaterials|
|First Page||Previous Page||Next Page||Last Page|
| Nanopattern-induced changes in morphology and motility of smooth muscle cells
Yim, E. K., R. M. Reano, et al. (2005), Biomaterials 26(26): 5405-13.
Abstract: Cells are known to be surrounded by nanoscale topography in their natural extracellular environment. The cell behavior, including morphology, proliferation, and motility of bovine pulmonary artery smooth muscle cells (SMC) were studied on poly(methyl methacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) surfaces comprising nanopatterned gratings with 350 nm linewidth, 700 nm pitch, and 350 nm depth. More than 90% of the cells aligned to the gratings, and were significantly elongated compared to the SMC cultured on non-patterned surfaces. The nuclei were also elongated and aligned. Proliferation of the cells was significantly reduced on the nanopatterned surfaces. The polarization of microtubule organizing centers (MTOC), which are associated with cell migration, of SMC cultured on nanopatterned surfaces showed a preference towards the axis of cell alignment in an in vitro wound healing assay. In contrast, the MTOC of SMC on non-patterned surfaces preferentially polarized towards the wound edge. It is proposed that this nanoimprinting technology will provide a valuable platform for studies in cell-substrate interactions and for development of medical devices with nanoscale features.
| Nano-probing of the membrane dynamics of rat pheochromocytoma by near-field optics
Piga, R., R. Micheletto, et al. (2005), Biophys Chem 117(2): 141-6.
Abstract: High-resolution analysis of activities of live cells is limited by the use of non-invasive methods. Apparatuses such as SEM, STM or AFM are not practicable because the necessary treatment or the harsh contact with system probe will disturb or destroy the cell. Optical methods are purely non-invasive, but they are usually diffraction limited and then their resolution is limited to approximately 1 microm. To overcome these restrictions, we introduce here the study of membrane activity of a live cell sample using a Scanning Near-field Optical Microscope (SNOM). A near field optical microscope is able to detect tiny vertical movement on the cell membrane in the range of only 1 nm or less, about 3 orders of magnitude better than conventional optical microscopes. It is a purely non-invasive, non-contact method, so the natural life activity of the sample is unperturbed. In this report, we demonstrated the nanometer-level resolving ability of our SNOM system analyzing cardiomyocytes samples of which membrane movement is known, and then we present new intriguing data of sharp 40 nm cell membrane sudden events on rat pheochromocytoma cell line PC12. All the measurements are carried out in culture medium with alive and unperturbed samples. We believe that this methodology will open a new approach to investigate live samples. The extreme sensitivity of SNOM allows measurements that are not possible with any other method on live biomaterial paving the way for a broad range of novel studies and applications.
| Nanoscale characterization of carbazole-indole copolymers modified carbon fiber surfaces
Sarac, A. S., M. Serantoni, et al. (2005), J Nanosci Nanotechnol 5(10): 1677-82.
Abstract: Polycarbazole, carbazole and indole containing copolymers were electrochemically coated onto carbon fiber. The resulting polymers and copolymers were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Characterization of the thin polymer films were performed on the polymer-coated surface of the carbon fiber. Therefore, the results obtained could elucidate the relationship between the initial feed monomer ratio, the resulting polymer/copolymer film morphology and the surface structure formed. The thickness increase (in diameter) was 0.3 and 0.9 microm, for two different composition of carbazole/indole on the carbon fiber. The carbon fibers coated with copolymer thin films were from 6.5 to 8.2 microm in diameter (from AFM measurement).
| Nanoscale investigation of pathogenic microbial adhesion to a biomaterial
Emerson, R. J. t. and T. A. Camesano (2004), Appl Environ Microbiol 70(10): 6012-22.
Abstract: Microbial infections of medical implants occur in more than 2 million surgical cases each year in the United States alone. These increase patient morbidity and mortality, as well as patient cost and recovery time. Many treatments are available, but none are guaranteed to remove the infection. In many cases, the device infections are caused by the adhesion of microbes to the implant, ensuing growth, pathogenesis, and dissemination. The purpose of this work is to examine the initial events in microbial adhesion by simulating the approach and contact between a planktonic cell, immobilized on an atomic force microscope (AFM) cantilever, and a biomaterial or biofilm substrate. The two model microbes used in this study, Candida parapsilosis (ATCC 90018) and Pseudomonas aeruginosa (ATCC 10145), were chosen for both their clinical relevance and their ease of acquisition and handling in the laboratory setting. Attractive interactions exist between C. parapsilosis and both unmodified silicone rubber and P. aeruginosa biofilms. Using C. parapsilosis cells immobilized on AFM cantilevers with a silicone substrate, we have measured attractive forces of 4.3 +/- 0.25 nN in the approach portion of the force cycle. On P. aeruginosa biofilms, the magnitude of the attractive force decreases to 2.0 +/- 0.40 nN and is preceded by a 2.0-nN repulsion at approximately 75 nm from the cell surface. These data suggest that C. parapsilosis may adhere to both silicone rubber and P. aeruginosa biofilms, possibly contributing to patient morbidity and mortality. Characterization of cell-biomaterial and cell-cell interactions allows for a quantitative link between the physicomechanical and physicochemical properties of implant materials and the nanoscale interactions leading to microbial colonization and infection.
| Nanoscale size effect of magnetic nanocrystals and their utilization for cancer diagnosis via magnetic resonance imaging
Jun, Y. W., Y. M. Huh, et al. (2005), J Am Chem Soc 127(16): 5732-3.
| Nanostructured antifouling poly(ethylene glycol) films for silicon-based microsystems
Sharma, S. and T. A. Desai (2005), J Nanosci Nanotechnol 5(2): 235-43.
Abstract: The creation of antifouling surfaces is one of the major prerequisites for silicon-based micro-electrical-mechanical systems for biomedical and analytical applications (known as BioMEMS). Poly(ethylene glycol) (PEG), a water-soluble, nontoxic, and nonimmunogenic polymer has the unique ability to reduce nonspecific protein adsorption and cell adhesion and, therefore, is generally coupled with a wide variety of surfaces to improve their biocompatibility. To this end, we have analyzed PEG thin films of various grafting densities (i.e., number of PEG chains per unit area) coupled to silicon using a single-step PEG-silane coupling reaction scheme using variable-angle ellipsometry. Initial PEG concentration and coupling time were varied to attain different grafting densities. These data were theoretically analyzed to understand the phenomenon of PEG film formation. Furthermore, all the PEG films were evaluated for their ability to control biofouling using albumin and fibrinogen as the model proteins. PEG thin films formed by using higher PEG concentrations (> or = 10 mM PEG) or coupling time (> or = 1 h) demonstrated enhanced protein fouling resistance behavior. This analysis is expected to be useful to form PEG films of desired grafting density on silicon substrates for appropriate application.
| Nanostructured ceramic oxides with a slow crack growth resistance close to covalent materials
Chevalier, J., S. Deville, et al. (2005), Nano Lett 5(7): 1297-301.
Abstract: Oxide ceramics are sensitive to slow crack growth because adsorption of water can take place at the crack tip, leading to a strong decrease of the surface energy in humid (or air) conditions. This is a major drawback concerning demanding, long-term applications such as orthopaedic implants. Here we show that a specific nanostructuration of ceramic oxides can lead to a crack resistance never reached before, similar to that of covalent ceramics.
| Nanostructuring titania by embossing with polymer molds made from anodic alumina templates
Goh, C., K. M. Coakley, et al. (2005), Nano Lett 5(8): 1545-9.
Abstract: We demonstrate a method for embossing titania sol--gel precursor with poly(methyl methacrylate) (PMMA) molds to make thin films of titania that have dense arrays of 35--65 nm diameter pores, whose features are 1 order of magnitude smaller than those previously demonstrated for sol--gel molding. We show that the high modulus of PMMA is necessary to preserve small features with high aspect ratios on the mold for nanopatterning. The molds are prepared by thermally infiltrating PMMA into anodic alumina templates, whose pore dimensions and depths are adjustable by varying anodization conditions. The difficulties associated with mold release from a master are avoided by wet etching the template. These titania films, and others made with other semiconductors, could be useful for photovoltaic, photocatalytic, and sensing applications where nanostructuring of surfaces with controlled dimensions are essential.
| Nanotechnology for biomaterials engineering: structural characterization of amphiphilic polymeric nanoparticles by 1H NMR spectroscopy
Hrkach, J. S., M. T. Peracchia, et al. (1997), Biomaterials 18(1): 27-30.
Abstract: Nanoparticles composed of diblock poly(D,L-lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) or a branched, multiblock PLA-(PEG)3 were prepared by the single emulsion technique. Results of previous studies of these nanoparticles suggested that their structure is of the core-corona type with a polyester core and an outer PEG coating. In the present study, 1H NMR spectroscopy was utilized to provide direct evidence of the structure of these nanoparticles suspended in an aqueous environment. The results confirm the existence of the core-corona structure under these conditions, and show that the PEG moieties extend out from the nanoparticle core into the aqueous environment, and exhibit chain mobility similar to that of PEG in solution.
| Nanotechnology: a new look
Williams, D. (2004), Med Device Technol 15(8): 9-10.
Abstract: A recently published report has reassessed the meanings of nanoscience and nanotechnology and considered the opportunities and hazards that arise within this area. Some of the factors relevant to medical nanotechnology are considered here.
| Nanowire dye-sensitized solar cells
Law, M., L. E. Greene, et al. (2005), Nat Mater 4(6): 455-9.
Abstract: Excitonic solar cells-including organic, hybrid organic-inorganic and dye-sensitized cells (DSCs)-are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient and stable excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
| Nasal delivery of insulin using chitosan microspheres
Varshosaz, J., H. Sadrai, et al. (2004), J Microencapsul 21(7): 761-74.
Abstract: Nasal delivery of insulin is an alternative route for administration of this drug. The objective of this study was preparation of chitosan microspheres for insulin nasal delivery. After preparation of insulin chitosan microspheres by emulsification-cross linking process, the effect of chitosan quantity (200-400mg), cross-linker type (ascorbic acid or ascorbyl palmitate) and amount (70-140 mg) were studied on the morphology, particle size, loading efficiency, flow and release of insulin from the microspheres by a factorial design. Optimized formulation was administered nasally in four groups of diabetic rats and their serum insulin levels were analysed by the insulin enzyme immunoassay kit and the serum glucose by the glucose oxidase kits. Insulin loading in microspheres was between 4.7-6.4% w/w, preparation efficiency more than 65% and mean particle size was 20-45 microm. In most cases, drug released followed a Higuchi model. Ascorbic acid caused an increase in stability, particle size and T50%, while decreased the loading efficiency and production efficiency. Increasing the chitosan content, increased particle size, flow and insulin release rate form the microspheres. The increase of cross-linking percentage decreased the flow and size of the microspheres while increase of cross-linking percentage promoted the stability and decreased DE8% of insulin. Microspheres containing 400mg of chitosan and 70mg ascorbyl palmitate caused a 67% reduction of blood glucose compared to i.v. route and absolute bioavaliability of insulin was 44%. The results showed that chitosan microspheres of insulin are absorbable from nasal route.
| Natural tissue as a biomaterial
Kiraly, R. J. and Y. Nose (1974), Biomater Med Devices Artif Organs 2(3): 207-24.
| N-Chloroacyl-6-O-triphenylmethylchitosans: useful intermediates for synthetic modifications of chitosan
Holappa, J., T. Nevalainen, et al. (2005), Biomacromolecules 6(2): 858-63.
Abstract: An efficient synthetic route was developed for the mild chloroacylation of chitosan with different chloroacyl chlorides. Full N-chloroacylation was obtained with this procedure without any O-acylation, and products having lower degrees of substitution can also be produced. Organo-soluble 6-O-triphenylmethylchitosan was used as a starting material for the acylation reactions. The resulting N-chloroacyl-6-O-triphenylmethylchitosan intermediates were also organo-soluble and characterized by FT-IR. N-Methylpiperazine moieties were attached to make end products that were sufficiently soluble for characterization by NMR and also to prove that the present intermediates could be used for further modifications. The end products were fully characterized by 1H NMR, 13C NMR, and 2D 1H-13C heteronuclear single-quantum correlation NMR spectroscopy. The degrees of substitution were determined by 1H NMR. Molecular weight determination by GPC-LS displayed a significant degradation of the polymer. The weight-average molar masses (M(w)) of the end products ranged from 29.6 to 49.4 kDa, when the M(w) of the starting material was 144.2 kDa.
| Near net-shape fabrication of hydroxyapatite glass composites
Zhu, Q., G. De With, et al. (2004), J Mater Sci Mater Med 15(11): 1187-91.
Abstract: Near net-shape fabrication of hydroxyapatite (HA) glass composites has been attempted by infiltrating a glass into porous HA performs. Main efforts were put to develop glasses that are chemically compatible with HA at elevated temperatures. After extensive investigations in the phosphate and borosilicate systems, glasses of (50-55)SiO2-(20-25)B203-(10-20)Li2O-(0-6)CaO (wt%) composition were successfully developed. The glass shows good chemical compatibility with HA at elevated temperatures. Dense HA/glass composites can be fabricated at 850-950 degress C by the melt infiltration process. Investigations demonstrated a good near net-shape capability of the process, where the linear shrinkage induced by the infiltration process is less than 0.1%. Preliminary mechanical tests showed that the fracture strength and toughness of the infiltrated HA/glass composite are comparable with dense HA.
| Needs, problems, and opportunities in biomaterials and biocompatibility
Andrade, J. D. (1992), Clin Mater 11(1-4): 19-23.
Abstract: There are four topics related to biomaterials and biocompatibility which I feel are key problems, are often unrecognized, and are therefore rich opportunities for work in the near future: (i) the covalent instability of proteins, (ii) the concept of statistical specificity and statistical heterogeneity, (iii) the issue of solid surface dynamics and surface relaxation, and (iv) the growing concern with the costs of health care and of medical research. Each is briefly discussed in this paper.
| Neocartilage from human mesenchymal stem cells in alginate: implied timing of transplantation
Ma, H. L., T. H. Chen, et al. (2005), J Biomed Mater Res A 74(3): 439-46.
Abstract: Previous reports have demonstrated the suitability of alginate microencapsulation for chondrogenesis of human mesenchymal stem cells (MSCs) in vitro. This study examined the MSCs-alginate constructs that were transplanted beneath the dorsal skin of nude mice for 8 weeks after a variety of in vitro culture periods. The in vitro culture had great effects on gross morphology and histological characteristics of transplants. The integrity of alginate of transplants increased as the in vitro culture period increased. Transplants were characterized by an opaque and yellowish color, fair burnish, a firm to elastic texture, but without any evidence of calcification spots. Histological findings agreed with the clinical determination of hyaline cartilage, characterized by isolated cells with basophilic ground substance positive in Safranin-O staining and collagen type II immunohistochemistry. Transplants with exposure to TGF-beta1 for more than 2 weeks before transplantation, lost burnish, were flexible in texture, and had an increased formation of calcification spots. Accordingly, 1-week exposure to TGF-beta1 in vitro before transplantation is appropriate for neocartilage formation of human MSCs in alginate. These findings suggested that regeneration using cell therapy or tissue engineering should assist in ascertaining the optimal timing of transplantation.
| Neo-intimal development on textured biomaterial surfaces during clinical use of an implantable left ventricular assist device
Graham, T. R., K. Dasse, et al. (1990), Eur J Cardiothorac Surg 4(4): 182-90.
Abstract: Implantable left ventricular assist systems are being developed for long term clinical use. Prototype devices are currently used as extended mechanical bridges to cardiac transplantation. The Thermo Cardiosystems Inc. (TCI) pneumatic pusher plate left ventricular assist device (LVAD) features textured blood contacting surfaces to encourage the formation of an adherent fibrin-cellular coagulum. This serves as the foundation for the development of a neo-intimal lining. The TCI LVAD was implanted in 6 male patients (age range 22-53 years) between 1986 and 1988. The duration of implantation ranged from 1-41 days. No clinical thromboembolic events or pump-related thromboembolism occurred and none was evident at necropsy. The six device linings have been fully evaluated. Explanted devices were free of thrombus and calcification. Lining samples for light and electron microscopy were collected from areas of the diaphragm identical for flex and blood shear conditions and from high and low shear areas on the static housing. Islands of collagenous tissue were deposited on the static housing amongst compact fibrin. By day 13, cells populated the surface of the developing neo-intima overlying the diaphragm. By 41 days, the surface cell density increased and the cells became spindle shaped and relatively orientated in the high shear/flex area. Immunohistochemical techniques suggest that these cells are of mesenchymal origin. Textured blood contacting surfaces appear satisfactory in the preliminary clinical use of this device.
| Neoperitoneal formation after implantation of various biomaterials for the repair of abdominal wall defects in rabbits
Bellon, J. M., L. A. Contreras, et al. (1999), Eur J Surg 165(2): 145-50.
Abstract: OBJECTIVE: To study the interfaces between the visceral peritoneum and some of the biomaterials used to repair defects in the abdominal wall. DESIGN: Animal study. SETTING: School of medicine, Spain. MATERIAL: 48 New Zealand white rabbits divided into 4 groups of 12 each. INTERVENTIONS: Full thickness defects 50 x 70 mm were created in the abdominal wall and repaired with polytetrafluoroethylene (PTFE, Soft Tissue Patch), one of two polypropylene patches (Marlex and Prolene), or lyophylised dura mater (Lyo-Dura). 3 animals from each group were killed at 14, 30, 60 and 90 days and specimens examined by light microscopy, scanning electron microscopy, and immuno histochemistry by labelling of macrophages with RAM-11, a specific monoclonal antibody (MoAb). MAIN OUTCOME MEASURES: Infection, healing, development of adhesions, and histological appearance of the interface. RESULTS: Tissues responded similarly to materials of similar structures. Layered prostheses (PTFE and Lyo-Dura) caused formation of a well organised neoperitoneum with few adhesions to the abdominal viscera (loose adhesions in 2 animals in each group), whereas the mesh prostheses generated a disorganised neoperitoneum with many adhesions (Marlex loose adhesions 3, firm 8, and integrated 1; Prolene loose adhesions 2, firm 8, and integrated 2). Lyo-Dura was associated with the formation of areas of calcification. Labelling of macrophages with the MoAb showed that they were in direct contact with all materials studied. CONCLUSIONS: Layered biomaterials with little or no porosity (PTFE and Lyo-Dura) are the most suitable of the four for implantation in sites where the prosthesis is in contact with the visceral peritoneum, because they induce minimal adhesions.
| Neovascularization and vascular markers in a foreign body reaction to subcutaneously implanted degradable biomaterial in mice
van Amerongen, M. J., G. Molema, et al. (2002), Angiogenesis 5(3): 173-80.
Abstract: To study the spatiotemporal processes of angiogenesis during a foreign body reaction (FBR), biodegradable bovine collagen type-1 (COL-I) discs were implanted in mice for a period up to 28 days. The cellular infiltration (consisting mainly of macrophages, giant cells and fibroblasts), and the extent of neovascularization into the discs were determined. Also the expression levels and/or distribution of the endothelial cell markers von Willebrand factor (vWF), platelet endothelial cell adhesion molecule-1 (PECAM-1)/CD31, MECA-32 antigens and endomucin, and of the basal lamina marker collagen type IV (Coll IV) were analysed. In time, a strong neovascularization of the discs was observed, with frequently occurring vascular sprouting, and intussusceptive growth of vessels. In this model, vWF, MECA-32 and endomucin antibodies often failed to stain neovessels in the COL-I discs. In contrast, staining for collagen IV basal lamina component in combination with CD31 covered the complete range of neo-vessels. We conclude that the model described in this study is a useful model to study FBR induced angiogenesis because of the active neovascularization taking place during prolonged periods of time.
|First Page||Previous Page||Next Page||Last Page|