Bio-Medical Materials and Engineering - Volume 4, issue 1

Authors: Babizhayev, Mark A. | Chumayevskii, Nikolai A.

Article Type: Research Article

Abstract: Intraocular lenses (IOL) made of polymethyl methacrylate (PMMA) lack an important yellowish pigment useful as a filter in the visual process and in the protection of the retina from short wavelength light. It was found that the PMMA used for IOL manufacturing can be tinted by dry exposure to mercury near-UV emitting lamp (emission maximum, 365 nm, light bandwidth ± 140 nm; irradiance of 50–100 W/sq m as measured at the PMMA surface; time of exposure 70–100 h, room temperature). The UV irradiated samples were stored in the atmosphere of N2 under the heating-protected and clean conditions. The IOL …sample holder allowed to remove IOL loops and their fixation areas from the zone of the passing light. The absorptive properties of IOLs treated with UV light were similar to those of young human lenses. Raman vibration and fluorescence spectral analyses of IOLs have shown that the yellow colour and its intensity in the irradiated samples depends on the presence of conjugated C=C and C=O groups (π−π conjugation) in the chemical composition of PMMA. When the PMMA samples were exposed for 70 h to a high level of UV radiation (50–100 W/sq m) no damage was seen with scanning electron microscopy at both side surfaces of the IOLs. The PMMA water exhaustive extracts made by 70 h of UV radiation exposure did not show any cytological damage when injected into the cell cultures of fibroblasts. The threshold for optical breakdown in PMMA was detected by 100 h of UV radiation at the level of exposure equivalent to at least 20,000 times levels for expected ambient UV exposure to PMMA within the eye. A rigorous quality index defmed as the ratio of the line C = C/C = O stretching mode intensities was introduced for the UV-absorbing PMMA photostability. The findings suggest an applicability of the photochemical tinting and further research to test the efficacy and safety of UV-absorbing chromophore induction in the PMMA IOLs. Show more

Keywords: intraocular lenses, polymethyl methacrylate, ultraviolet irradiation, Raman and fluorescence spectroscopy, surface area effects, biocompatibility and cytotoxicity, ultraviolet-absorbing chromophores

DOI: 10.3233/BME-1994-4101

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 1-16, 1994

Authors: Torrisi, L.

Article Type: Research Article

Abstract: Thin films of bio-polymers, such as polymethylmetacrylate, polytetrafluoroethylene, polyethylene-terephthalate and polyimide, are efficiently etched in air by UV laser pulses. A different sharp laser fluence threshold for significant etching is measured for each polymer. The thresholds are correlated to the chemical structure and to the wavelength-dependent absorption coefficient of the irradiated polymer. The polymers, having low absorption coefficients, show thresholds of the order of some J/cm2 , about one order magnitude higher than polymers having high absorption coefficients. Measurements on the polymer etching rates, in terms of removed molecules per eV at the used 347 nm wavelength, and a discussion …on the laser-polymer interaction are presented. An interesting application of the laser ablation process to bio-polymers, concerning the ability to realize microfilters for the bio-medical field by irradiating the polymer surface through a perforated metal mask, is discussed. Show more

Keywords: microfilter, bio-polymer, laser-ablation

DOI: 10.3233/BME-1994-4102

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 17-26, 1994

Authors: Nakamura, Takao | Hayashi, Kozaburo | Hirano, Katsuhiko | Matsumoto, Takeo

Article Type: Research Article

Abstract: Limiting factors of the system efficiency of an electric-motor-driven ventricular assist device (VAD) consisting of a brushless dc motor and a ball screw in the actuator were analyzed from the balance of force and torque in the pump and actuator. The results suggested that several mechanical components in the actuator should be improved to increase the efficiency. According to the suggestion, rotor material was changed from stainless steel to a lighter engineering plastics; smaller ball bearings were used to reduce rotor inertia; the ball screw was changed from rolled- to ground-execution type; the friction loss in the anti-rotation column inside …the ball screw shaft was reduced by changing sliding mechanism to rolling one. These improvements elevated the total system efficiency from 11% to 15%, The new system cleared durability testing of longer than 900 h. More elaborate assembly of the mechanical components of the actuator would increase the efficiency. Show more

Keywords: efficiency, electro-mechanical actuator, optical encoder, ventricular assist device

DOI: 10.3233/BME-1994-4103

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 27-36, 1994

Authors: Kim, Yong S. | Kang, Yoon H. | Kim, Jeong K. | Park, Joon B.

Article Type: Research Article

Abstract: Bone particle-impregnated bone cement is investigated in vitro, which could be used to improve fixation between bone and cement interface by ingrowth of tissues that may replace bone particles. Inorganic bone particles (150–300 μm diameter) were mixed with regular bone cement powder by 0, 10, 20, and 30% by weight and implanted into the pre-drilled intramedullary canal (11cm long, 10mm diameter) of canine femur. A 4mm diameter, 10mm long stainless steel rod was implanted to simulate the prosthesis. The specimens were cut into 2mm thick discs transversely along the long axis of the bone and ground to examine with a …confocal laser microscope. Diametral tensile strength tests were performed for the 0, 10, 20, and 30% bone particle impregnated bone cement discs without the intramedullary implant. Present results show that mixing bone particles with bone cement decreased the number of pores and porosity but increased the size of pores. The analysis of porosity distribution showed no significant difference between bone cement and bone particle-impregnated bone cement. Also, the strength of the bone particle-impregnated bone cement decreased linearly with increased amount of bone particles in spite of the decreased percent porosity. Using a bone particle-impregnated bone cement along with a pre-coated implant could be one of the solutions to the problems in the fixation of total joint arthroplasty. Show more

Keywords: bone particle-impregnated bone cement, porosity, bone cement, fixation

DOI: 10.3233/BME-1994-4104

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 37-46, 1994

Authors: Tomita, N. | Tamai, S. | Ikeuchi, K. | Ikada, Y.

Article Type: Research Article

Abstract: Pullout friction and cross-sectional relaxation tests were conducted to quantitatively evaluate the handling characteristics of braided sutures. The excellent handling of silk suture could be explained in terms of a large difference between static and dynamic pullout resistances. The difference in the resistance was closely correlated to the slope of the cross-sectional relaxation versus time logarithmic plot. It was therefore concluded that the cross-sectional stress-relaxation plays an important role in the handling performance of braided sutures.

Keywords: suture, handling, silk, mechanical property, biomaterial

DOI: 10.3233/BME-1994-4105

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 47-59, 1994

Authors: Nishihara, Katsunari | Tange, Tsuyoshi | Hirota, Kazushi | Kawase, Kiyoshi

Article Type: Research Article

Abstract: In vivo inducement of hybrid-type artificial bone marrow with hemopoietic inductive microenvironment (HIM) in sintered hydroxyapatite (HA) chamber was carried out. This research is important to disclose the mechanisms of hemopoiesis and is useful for clinical application. In the evolution of vertebrates. cartilage of the inner skeleton changed into bone, having biomechanical properties to form bone marrow cavities. The hemopoietic nests immigrated into the cavities from the spleen. We should be able to induce hemopoietic nests in a hydroxyapatite chamber in place of bone, if we can find optimal structural conditions. Therefore, we tried to artificially induce a hematopoietic field …in muscles using sintered porous tubular hydroxyapatite and new type hydroxyapatite plate made by high-pressure gas technique. As a result, not only in the pore sites of tubular hydroxyapatite artificial bone, but at the surface of the new type hydroxyapatite plate implanted in the dorsal muscles, marked differentiation of bone marrow cell clusters of the hematopoietic field could be observed. Show more

Keywords: artificial bone marrow, hemopoietic inductive microenvironment (HIM), hydroxyapatite chamber, high-pressure gas technique, hybrid-type

DOI: 10.3233/BME-1994-4106

Citation: Bio-Medical Materials and Engineering, vol. 4, no. 1, pp. 61-65, 1994