Bio-Medical Materials and Engineering - Volume 5, issue 3

Authors: Gautam, S.K. | Kamat, M.V. | Basu, S.

Article Type: Research Article

Abstract: Bio-interactions between a material and blood govern the compatibility of the material with the human body and, therefore, the single most important requirement for the blood interfacing implants/devices is haemocompatibility. The decisive events which control haemocompatibility occur at the molecular level and affect the various subphases of blood rheology. This effect on the already complex human blood rheology can be used to our advantage in the screening of blood-contacting materials. An attempt has been made in the present work to evaluate the haemocompatibility of materials based on changes in microrheological parameters of human blood. Samples of materials of equal surface …area known to be haemocompatible (medical grade silicon, polyvinyl chloride from blood bags) and materials known to be extremely haemo-incompatible (pyrex glass, copper, cotton fabric, all commercial grade) were incubated at 37.4°C in freshly drawn anticoagulated whole human blood, and changes in the haemorheological parameters (whole blood, plasma viscosity, intrinsic viscosity of red cells, platelet aggregation, albumin fibrinogen ratio) have been evaluated. The results of the study show that alterations in the haemorheological parameters are reliable indicators to the compatibility/incompatibility characteristics of well-known substances and that there is a case for haemorheological screening of biomaterials in the overall framework of haemocompatibility tests. Show more

Keywords: haemorheology, haemocompatibility, biomaterials, viscosity, evaluation

DOI: 10.3233/BME-1995-5301

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 3, pp. 141-149, 1995

Authors: Allen, Matthew | Butter, Ruth | Chandra, Lalitesh | Lettington, Alan | Rushton, Neil

Article Type: Research Article

Abstract: There is widespread interest in the use of interfacial layers in the preparation of diamond and diamond-like carbon (DLC) coatings. These DLC coatings deposited onto metal suhstrates with a silicon carbide (SiC) interfacial layer exhibit improved adhesion and show promise as wear-retardant coatings for biomedical implants. Although the DLC coatings show excellent biocompatibility in vitro. they may be susceptible to damage within the biological environment, leading to exposure of the interfacial silicon carbide. We have investigated the effects of two forms of silicon carbide (α-SiC and β-SiC) on macrophages, fibroblasts and bone cells in vitro. Both α- and β-SiC are …well-tolerated by cells at concentrations of up to 0.1 mg/ml but cause severe cytotoxicity at a concentration of 1 mg/ml. If SiC is to be used as an interfacial layer on biomedical implants, the quality of the DLC coating must be optimised to minimise the risk of film breakdown. Show more

Keywords: silicon carbide, DLC, interface, biocompatibility, toxicity

DOI: 10.3233/BME-1995-5302

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 3, pp. 151-159, 1995

Authors: Gil, F.J. | Fernández, E. | Manero, J.M. | Planell, J.A. | Sabria, J. | Cortada, M. | Giner, L.

Article Type: Research Article

Abstract: Wear is one of the main surface failure mechanisms in materials and it will play a leading role in substitutive dental biomaterials. The aim of the present study is to compare the abrasive wear of different metallic materials used in dental applications. The results show that the abrasive wear of alloys based on precious metals such as Pt, Pd, Au and Ag is higher than for Ti and Ti based alloys. The alloy with the highest weat resistance is the Co-Cr which exhibits as well the highest hardness and Young's modulus. Since the method corresponds to a well-established abrasive wear …standard, the behaviour of the different materials can be easily compared. Show more

Keywords: wear, abrasive, dental alloys, metal

DOI: 10.3233/BME-1995-5303

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 3, pp. 161-167, 1995

Authors: Chan, F.H.Y. | So, A.T.P. | Kung, A.W.C. | Lam, F.K. | Yip, H.C.L.

Article Type: Research Article

Abstract: A computerised thermal imaging system for thyroid diagnosis was developed by the authors and it was discovered that the rate of changes of temperature, rather than the absolute values, associated with a sequence of thermograms could help the medical doctors to identify clinical disorders. In order to further enhance the diagnostic capabilities and speed, a new method for medical thermogram analysis has been developed that compresses a sequence of thermograms into one thermogram while retaining the important information such as the geometrical patterns of the objects and the rate of temperature changes of each pixel within the images. As motion …artifacts arc unavoidable when a patient undergoes minutes of thermogram recording, direct comparison between images is deemed impossible. A high speed image matching algorithm has been developed to provide an absolute geometrical foundation for pixel-to-pixel comparison. The rate of change of temperature of a particular pixel along the sequence is represented by one single parameter after a process of temperature integration which can then be converted into a corresponding gray level for display. The resultant compressed thermogram can give a clear distinction between problem areas and normal ones. Although our emphasis is on thyroid diagnosis, it is anticipated that this new technique can be applicable to other areas of a human body. Show more

Keywords: thermography, medical diagnosis, image sequence compression, thyroid conditioning monitoring, boundary matching

DOI: 10.3233/BME-1995-5304

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 3, pp. 169-183, 1995

Authors: Dalton, Paul D. | Jefferson, Alan | Hong, Ye | Chirila, Traian V. | Vijayasekaran, Sarojini | Tahija, Sjakon G.

Article Type: Research Article

Abstract: A frequent cause of the failure of various materials tested as artificial vitreous substitutes is their short retention in the vitreous humour of the eye. Previous techniques to monitor the residence time of the vitreous substitutes have been traditionally complicated and usually involved the chemical modification of the test fluids. Fourier transform infrared (FTIR) spectrometry is used in this study to determine the rate of disappearance of a crosslinked poly(l-vinyl-2-pyrrolidinone) (PVP) hydrogel after injection into the vitreous humour of rabbits. The fluid removed from the eye at various postoperative intervals of time (1 day, 1 week, and 1 month) was …placed on a horizontal attenuated reflectance (ATR) unit, and the infrared spectrum from 700 to 3000 cm−1 was obtained directly. The absorption band at 1295cm−1 due to C-N stretching vibration does not overlap with bands of any other species (natural vitreous, blood) present in the test fluid. By estimating the intensity of this band, it was found that about 80% of the injected polymer was removed from the vitreous cavity within 1 month. This study shows that (1) FTIR spectrometry is a convenient method to assess the residence time of foreign materials in the vitreous humour, and (2) the PVP gel is unsuitable in this current form as a permanent vitreous substitute, regardless of the pathways of its removal, such as phagocytosis of fragments produced by the injection process, or enzymatic biodegradation. Show more

Keywords: vitreous substitute, poly(l-vinyl-2-pyrrolidinone) hydrogel, vitrectomy, injection or gel, Fourier transform infrared spectrometry

DOI: 10.3233/BME-1995-5305

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 3, pp. 185-193, 1995