Biomaterials.info - Resources for Engineers

Record 901 to 920

Biological control of Phytophthora ramorumon rhododendron
Orlikowski, L. B. (2004), Commun Agric Appl Biol Sci 69(4): 687-92.
Abstract: Phytophthora ramorum was found in Poland in 2000 as the causal agent of rhododendron blight. Besides eradication of diseased plants and rhododendron growing around, chemical and biological control of the pathogen is necessary. In this study in vitro activity of grapefruit extract and chitosan in the inhibition of P. ramorum growth and sporulation and their efficacy in the control of leaf and stem rot development was evaluated. Amendment of V8 juice agar and soil leachate with grapefruit extract resulted in the inhibition of colony growth and sporulation of P. ramorum. Zoosporangia were more susceptible to the extract than pathogen hyphae and chlamydospores. Chitosan only slightly inhibited the colony growth and zoosporngia production. Spraying of rhododendron inoculated with P. ramorum with grapefruit extract at conc. 165 microg/cm3 inhibited 2-3 times the spread of necrosis on stems and leaves. Pre- and postinoculation spraying of rhododendrons with chitosan at conc. of 1000 microg/cm3 suppressed the disease spread about 40%.

Biological effects of residual glutaraldehyde in glutaraldehyde-tanned collagen biomaterials
Speer, D. P., M. Chvapil, et al. (1980), J Biomed Mater Res 14(6): 753-64.
Abstract: Glutaraldehyde is commonly used to control physical and biological properties of collagen structure by means of intramolecular and/or intermolecular crosslinking of collagen molecules. Solubility, antigenicity, and biodegradation of naturally occurring or reconstituted collagenous matrices are effectively reduced by glutaraldehyde treatment. Adverse biological reactions to glutaraldehyde have been limited to infrequent contact dermatitis and to biocidal effects which are exploited in chemical sterilization media. In the present study of glutaraldehyde-tanned collagen sponge, the presence of glutaraldehyde was correlated with cytotoxic effects upon fibroblasts in tissue culture and foreign body giant cell reaction to bioimplants of the sponge. Fibroblast growth in tissue culture is 99% inhibited at media concentrations of 3.0 ppm glutaraldehyde. Extracts of glutaraldehyde collagen sponge in aqueous media at pH 7 and 4.5 yielded 6 micrograms and 65 micrograms glutaraldehyde per gram of collagen sponge, respectively. The yield increased tenfold at pH 4.5. Observations indicate that leaching of the glutaraldehyde from glutaraldehyde-tanned collagen sponge is sufficient to produce potentially adverse cellular effects both in vivo and in vitro.

Biological evaluation of a polyvinyl siloxane impression material
Mazzanti, G., C. Daniele, et al. (2005), Dent Mater 21(4): 371-4.
Abstract: OBJECTIVES: The aim of this study was to determine the irritant properties of a new polyvinyl siloxane impression material (Ghenesil, Lascod-Italy) after single application to intact skin of the rabbit. METHODS: The material was evaluated for primary skin irritation according to the UNI EN ISO 10993-10:1996 using three healthy male New Zealand White rabbits. The back of the animals was clipped free of fur and divided into four sites with the same area 24 h before application of the sample. The material was applied to only two sites; the other two were used as controls. All the sites were covered by gauze and the back of the rabbit was wrapped with a non-occlusive bandage. After 4 h, the bandage and the test material were removed; 1h later the sites were examined for skin irritation and the observation was repeated after 24, 48 and 72 h. The Score of Primary Irritation (SPI) was calculated for each animal and the Primary Irritation Index (PII) was calculated as the arithmetical mean of SPI values. RESULTS: The PII of the test material resulted 0.06. SIGNIFICANCE: Based on present results, it can be concluded that the primary skin irritation of the polyvinyl siloxane impression material tested can be considered negligible.

Biological evaluation of biomaterials for cardiovascular applications: some current results
Bruck, S. D. (1977), Med Prog Technol 5(2): 51-6.
Abstract: The proper biologic evaluation of biomaterials for blood-contacting applications must include considerations of hemorheologic parameters, species-related differences, and damages to the reticuloendothelial system. Although there are no materials currently available that are completely blood compatible, several smooth-surfaced polymers are quite tolerable in the physiological environment. These include chemically grafted polyacrylamide hydrogels, glow-discharge polymers of silica-free hexamethldisiloxane, and ethyl cellulose perfluorobutyrate.

Biological evaluation of calcium alginate microspheres as a vehicle for the localized delivery of a therapeutic enzyme
Barrias, C. C., M. Lamghari, et al. (2005), J Biomed Mater Res A 74(4): 545-52.
Abstract: Gaucher disease (GD) is caused by the decreased activity and/or stability of the lysosomal enzyme glucocerebrosidase (GCR). The available treatment consists in the intravenous administration of exogenous GCR, and is effective in reverting most of the symptoms. However, in terms of bone pathology, which is among the most disabling manifestations, a slow and incomplete response is observed, indicating that adjuvant therapies are necessary to consistently restore GCR activity in bone and accelerate regeneration. In this study, calcium alginate microspheres were analyzed as a vehicle for localized GCR delivery to bone. Results demonstrated that the entrapped enzyme retained full activity and exhibited a broader pH-dependent activity profile, compared to that of free-GCR, with improved stability at physiological pH. GCR release profile was established, and it was demonstrated that GCR could be released in a sustained manner. The biological behavior of the system was evaluated by analyzing the uptake of released GCR by GCR-deficient cells from GD patients, using different techniques: GCR activity measurements, radiolabeling, and cellulose acetate electrophoresis. Results demonstrated that GCR was internalized by cells significantly enhancing the residual enzymatic activity. To achieve an activity reconstitution level comparable to that obtained using free-GCR, only half of the dose was required with entrapped-GCR.

Biological evaluation of ChuangYuLing dressing-a multifunctional medicine carrying biomaterial
Peng, R., Q. Zheng, et al. (2005), J Huazhong Univ Sci Technolog Med Sci 25(1): 72-4, 77.
Abstract: The safety of Chuangyuling (CYL) dressing-a multifunctional medicine carrying biomaterial was evaluated in order to provide foundation for the application of CYL as material used in the wound healing. The traditional Chinese medicine (TCM) extract solution was compounded with scaffolds (gelatin and Bletilla hyacinthine gum), and then frozen and dried to form spongy and porous material CYL. According to the standard of biological evaluation of medical devices that was instituted by the ministry of health of China, the biological evaluation of CYL dressing was conducted. The results showed that all the contents of biological evaluation test consisting of acute toxicity, skin irritation, sensitization and cytotoxicity met the requirement of standards. It was concluded that the biomaterial carrying TCM (CYL dressing) is safe for application of wound healing.

Biological evaluation of hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterials with poly-L-lactide of different molecular weights intraperitoneally implanted into mice
Najman, S., V. Savic, et al. (2004), Biomed Mater Eng 14(1): 61-70.
Abstract: Histopathologic analysis of the tissue with HAp/PLLA implants was made and the leukocyte formula and chemiluminescence response of peritoneal phagocytes 2, 7 and 12 weeks after intraperitoneal implantation studied. Implants were made of HAp/PLLA biocomposites with PLLA molecular weights of 50000 (HAp/PLLA(50)) and 430000 g/mol (HAp/PLLA(430)) and of crushed devitalized femur bone of a young Wistar rat. Leukocyte formula and chemiluminescence of peritoneal phagocytes showed no systemic inflammatory response. The studied implants caused locally weak inflammatory reaction. The resorption of implants ranges in intensity (polymer resorption, i.e. disappearance rate), from the highest with the bone implants, low with HAp/PLLA(50), to the lowest with the HAp/PLLA(430) implants. Good resorption of the biocomposites and its mutual ingrowth with connective tissue prove their good biocompatibility.

Biological evaluation of polyester dendrimer: poly(ethylene oxide) "bow-tie" hybrids with tunable molecular weight and architecture
Gillies, E. R., E. Dy, et al. (2005), Mol Pharm 2(2): 129-38.
Abstract: High molecular weight (MW) polymers have shown promise in terms of improving the properties and the efficacy of low MW therapeutics. However, new systems that are highly biocompatible, are biodegradable, have well-defined MW, and have multiple functional groups for drug attachment are still needed. The biological evaluation of a library of eight polyester dendrimer-poly(ethylene oxide) (PEO) bow-tie hybrids is described here. The group of evaluated polymers was designed to include a range of MWs (from 20000 to 160000) and architectures with the number of PEO arms ranging from two to eight. In vitro experiments revealed that the polymers were nontoxic to cells and were degraded to lower MW species at pH 7.4 and pH 5.0. Biodistribution studies with (125)I-radiolabeled polymers showed that the high MW carriers (>40000) exhibited long circulation half-lives. Comparison of the renal clearances for the four-arm versus eight-arm polymers indicated that the more branched polymers were excreted more slowly into the urine, a result attributed to their decreased flexibility. Due to their essentially linear architecture that does not provide for good isolation of the iodinated phenolic moieties, the polymers with "two arms" were rapidly taken up by the liver. The biodistributions of two long-circulating high MW polymers in mice bearing subcutaneous B16F10 tumors were evaluated, and high levels of tumor accumulation were observed. These new carriers are therefore promising for applications in drug delivery and are also useful for improving our understanding of the effect of polymer architecture on pharmacokinetic properties.

Biological fabrication of nacreous coating on titanium dental implant
Wang, X. X., L. Xie, et al. (2005), Biomaterials 26(31): 6229-32.
Abstract: Titanium screws with 3.5mm diameter and 8mm length, as well as titanium flat sheets with size 4 mm x 8 mm x 0.3mm, were implanted into the epithelial mantle pearl sacs of a fresh water bivalve (Hyriopsis cumingii Lea) by replacing the pearls. After 45 days of cultivation, the implant surfaces were deposited with a nacre coating with iridescent luster. The coating could conform to some extent the thread topography of the screw implant and was about 200-600 microm in thickness. The coating was composed of a laminated nacreous layer and a transitional non-laminated layer that consisted mainly of vaterite and calcite polymorphs of calcium carbonate. The transitional layer was around 2-10 microm thick in the convex and flat region of the implant surface and could form close contact with titanium surface; while the transitional layer was much thicker in the steep concave regions and could not form close contact with the titanium surface. The reasons for inhomogeneity in thickness and the variation in interface character were discussed and the improvement to the design of the dental implant with respect to this coating method was suggested in the paper. The results suggest that it is possible to fabricate a biologically active and degradable, and mechanically tough and strong nacre coating on titanium dental implant by this novel coating technology.

Biological interactions: causes for risks and failures of biomaterials and devices
Jayabalan, M. (1993), J Biomater Appl 8(1): 64-71.
Abstract: Biomaterials and devices have been used in a variety of applications ranging from disposable extracorporeal devices and soft and hard tissue augmentation, to total artificial internal organs. However, there are risks and failures in each application which are a result of undesirable biological interactions. This article deals with various biological interactions in each category of implants and devices used in medical applications.

Biological performances of collagen-based scaffolds for vascular tissue engineering
Boccafoschi, F., J. Habermehl, et al. (2005), Biomaterials 26(35): 7410-7.
Abstract: Collagen is widely used for biomedical applications and it could represent a valid alternative scaffold material for vascular tissue engineering. In this work, reconstituted collagen films were prepared from neutralized acid-soluble solutions for subsequent haemocompatibility and cell viability performance assays. First, haemoglobin-free, thrombelastography and platelet adhesion tests were performed in order to investigate the blood contact performance. Secondly, specimens were seeded with endothelial cells and smooth muscle cells, and cell viability tests were carried out by MTT and SEM. Results show that neutralized acid-soluble type I collagen films do not enhance blood coagulation, do not alter normal viscoelastic properties of blood and slightly activate platelet adhesion and aggregation. Cell culture shows that the samples are adequate substrates to support the adhesion and proliferation of endothelial and smooth muscle cells.

Biological requirements for biomaterials. I. Cytotoxicity of biomaterials, in vitro. II. Cell adhesion to biomaterials, in vitro
Kawahara, H. (1985), Implantologist 3(2): 41-9.

Biologically modified polymeric biomaterial surfaces: introduction
Piskin, E. (1992), Clin Mater 11(1-4): 3-7.
Abstract: Synthetic polymers are the most diverse class of biomaterials. As with all other biomaterials, they must meet certain criteria depending on the intended medical application. Biocompatibility is one of the basic criteria for selection of a particular biomaterial. Biomaterial surfaces are believed to play an important role in determining their biocompatibilities. The study of the surface properties of biomaterials, and also interactions between the biomaterial and the living system interface are fundamental to define the behavior of the biomaterial in the biological environment, and therefore to evaluate accurately the biocompatibility of a new biomaterial. Surfaces of polymeric biomaterials may be modified by using a variety of biological entities (e.g. proteins and cells) not only to increase their biocompatibilities but also to add a functionality to the respective surfaces. I intended to highlight the topics which are discussed in depth in the other chapters of this volume.

Biomaterial adherent macrophage apoptosis is increased by hydrophilic and anionic substrates in vivo
Brodbeck, W. G., J. Patel, et al. (2002), Proc Natl Acad Sci U S A 99(16): 10287-92.
Abstract: An in vivo rat cage implant system was used to identify potential surface chemistries that prevent failure of implanted biomedical devices and prostheses by limiting monocyte adhesion and macrophage fusion into foreign-body giant cells while inducing adherent-macrophage apoptosis. Hydrophobic, hydrophilic, anionic, and cationic surfaces were used for implantation. Analysis of the exudate surrounding the materials revealed no differences between surfaces in the types or levels of cells present. Conversely, the proportion of adherent cells undergoing apoptosis was increased significantly on anionic and hydrophilic surfaces (46 +/- 3.7 and 57 +/- 5.0%, respectively) when compared with the polyethylene terephthalate base surface. Additionally, hydrophilic and anionic substrates provided decreased rates of monocyte/macrophage adhesion and fusion. These studies demonstrate that biomaterial-adherent cells undergo material-dependent apoptosis in vivo, rendering potentially harmful macrophages nonfunctional while the surrounding environment of the implant remains unaffected.

Biomaterial and design concepts to minimize wear in total joint arthroplasties
Lemons, J. E. (1994), Semin Arthroplasty 5(1): 45-51.
Abstract: The evolution of high technology-based total joint arthroplasty (TJA) materials and designs has resulted in systems that provide significant advantages related to surgical procedures, functional mechanics, and short-term and long-term rehabilitation. The research and development community has been addressing key issues associated with attachment-to-tissues for force transfer and wear and debris from articulating surfaces. To minimize wear, multiple material and design technologies have been applied, with recent emphasis on surface and bulk modifications of alloys and polymers plus the reconsideration of ceramic and metallic articulations. This article provides an overview of the biomaterial considerations for articulating surfaces of existing TJA systems, efforts to control wear phenomena, and implications on the clinical aspects of long-term function.

Biomaterial and implant surfaces: a surface science approach
Kasemo, B. and J. Lausmaa (1988), Int J Oral Maxillofac Implants 3(4): 247-59.

Biomaterial and implant surfaces: on the role of cleanliness, contamination, and preparation procedures
Kasemo, B. and J. Lausmaa (1988), J Biomed Mater Res 22(A2 Suppl): 145-58.
Abstract: Material specificity in implant-tissue interactions derives primarily from the surface properties (chemical composition, microstructure, etc.) of the implant. This article addresses several questions related to implant and biomaterial surfaces: What is the status of real implant surfaces (composition, cleanliness, contamination, microstructure, etc.), and how does it vary with preparation procedures? Can the surface status be varied and analyzed in a controlled manner? How significant are surface status variations for in vivo function? And so on. We discuss clean surfaces, how they are contaminated, and how the contamination may affect the properties. We also discuss different preparation procedures, such as conventional machining, plasma treatment, and sterilization. Three important conclusions are drawn: (i) The surface status of a particular implant material may vary widely depending on its preparation and handling history. (ii) The surface status of implants is expected to be important for in vivo function, and should thus be controlled and standardized. (iii) It is usually not possible to predict how a change in surface status will affect the long-term, in vivo function of an implant.

Biomaterial aspects of calcium phosphates. Properties and applications
Jarcho, M. (1986), Dent Clin North Am 30(1): 25-47.
Abstract: Biomaterials composed of calcium phosphate ceramics are receiving increasing attention as potential bone graft substitutes. These substances have proved to be the most biocompatible hard-tissue implant materials discovered. The mechanical and biologic properties of the calcium phosphates, as well as their present and future applications, are discussed.

Biomaterial aspects of Interpore-200 porous hydroxyapatite
White, E. and E. C. Shors (1986), Dent Clin North Am 30(1): 49-67.
Abstract: Interpore-200 is the product of over 11 years of continuous research and development. It has been investigated at over 25 research centers in a wide variety of animal and human implant settings, including alveolar ridge augmentation, periodontics, and orthognathic reconstructions. The biomaterial aspects of Interpore-200 show the following: Interpore-200 has a highly interconnected, three-dimensional porosity that is uniform and consistent. The hydroxyapatite manufactured from marine corals is biocompatible and nontoxic. Interpore-200 is essentially pure hydroxyapatite, with the balance consisting of tricalcium phosphate. Interpore-200 is approximately 55 to 65 per cent porous with nominal pore diameters of 200 micron. Unlike nonporous materials, Interpore-200 is osteoconductive and results, when placed next to a viable bone, in an advancing front of bone into the implant. From 50 to 88 per cent of the porosity within the implant is filled with woven and lamellar bone within 3 months. Moreover, the surfaces of Interpore-200 are intimately bonded with the bone tissue. The biomechanical properties of Interpore-200 blocks are similar to those of a cancellous bone graft. Once ingrown with vascularized bone tissue, the defect site is, in effect, restored. Interpore-200 adequately matches the elastic properties of bone so that stresses necessary to maintain healthy bone are transmitted throughout the regenerated region. Extensive animal and clinical studies have shown that nonporous implants or implants without interconnected porosity can result in aberrant mineralization, stress shielding, low fatigue strength, and bulk displacement. Hydroxyapatite with interconnected porosity like Interpore-200 reacts differently than materials with limited or no porosity. In animals, Interpore-200 exhibits 0 to 5 per cent biodegradation per year. Moreover, this minimal biodegradation is compensated by regeneration of bone. These studies have now been extended for 4 years. Interpore-200 and its ingrown bone are remodeled in response to the same chemical and biomechanical forces that remodel normal bone. Therefore, Interpore-200 responds in accordance to Wolff's law. Having achieved an optimal combination of biomaterial (hydroxyapatite) in an ideal porous structure (replamineform), Interpore-200 fulfills the expectation of early researchers in the basic sciences who demonstrated that an interconnected porous material is better tolerated by the body than the same material in solid form.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomaterial aspects of surface replacement arthroplasty of the hip
Black, J. and V. Sholtes (1982), Orthop Clin North Am 13(4): 709-28.

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