Bio-Medical Materials and Engineering - Volume 7, issue 6

Authors: Khang, Gilson | Jeon, Ju Hyoung | Lee, Jin Whan | Cho, Soon Chae | Lee, Hai Bang

Article Type: Research Article

Abstract: Surface treatment, such as plasma glow discharge treatment, onto poly(lactide‐co‐glycolide) (PLGA) has been investigated to improve the cell‐, tissue‐ and blood‐compatibility. Surface‐treated samples were characterized by measurement with a contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the plasma‐treated PLGA surfaces decreased with increasing plasma exposure time from 92^{\circ} to about 30^{\circ} , i.e., increased hydrophilicity. From the results of ESCA analysis of plasma‐treated films, the incorporation of oxygen molecules into plasma onto the PLGA surface was observed. Cell adhesion and growth on plasma‐treated PLGA surfaces were more active than …on the control. Furthermore, the maximum adhesion and growth of cells in moderate hydrophilicity were investigated. Morphology of the adhered platelets on the plasma‐treated PLGA surface showed less activity than on the control, and the number of adhered platelets on the plasma‐exposed PLGA sample decreased with decreasing water contact angle. It seems that surface wettability of PLGA plays an important role in cell adhesion, spreading and growth, and platelet adhesion. Show more

Keywords: Poly(lactide‐co‐glycolide), plasma treatment, wettability, fibroblast, platelets, adhesions

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 357-368, 1997

Authors: Khang, Gilson | Jeon, Ju Hyoung | Lee, Jin Whan | Cho, Soon Chae | Lee, Hai Bang

Article Type: Research Article

Abstract: Surface treatment, such as plasma glow discharge treatment, onto poly(lactide‐co‐glycolide) (PLGA) has been investigated to improve the cell‐, tissue‐ and blood‐compatibility. Surface‐treated samples were characterized by measurement with a contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the plasma‐treated PLGA surfaces decreased with increasing plasma exposure time from 92^{\circ} to about 30^{\circ} , i.e., increased hydrophilicity. From the results of ESCA analysis of plasma‐treated films, the incorporation of oxygen molecules into plasma onto the PLGA surface was observed. Cell adhesion and growth on plasma‐treated PLGA surfaces were more active than …on the control. Furthermore, the maximum adhesion and growth of cells in moderate hydrophilicity were investigated. Morphology of the adhered platelets on the plasma‐treated PLGA surface showed less activity than on the control, and the number of adhered platelets on the plasma‐exposed PLGA sample decreased with decreasing water contact angle. It seems that surface wettability of PLGA plays an important role in cell adhesion, spreading and growth, and platelet adhesion. Show more

Keywords: Poly(lactide‐co‐glycolide), plasma treatment, wettability, fibroblast, platelets, adhesions

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 357-368, 1997

Authors: Yoshikawa, Takafumi | Peel, Sean A.F. | Gladstone, Janice R. | Davies, John E.

Article Type: Research Article

Abstract: Bone marrow cells obtained from rat femora were subjected to primary culture with 15% fetal bovine serum in the presence of 10^{-8} M dexamethasone, and following trypsin treatment 5 days later were seeded on Petriperm^{{\rm TM}} dishes which have a flexible bottom. After a 2‐day subculture, a cyclic stress consisting of a 1 s stretch (0.3% strain, 0.5 Hz) and a 1 s relaxation for 30 min every day was started. Culture tissue was removed on day 2 of the subculture (immediately prior to start of stimulation), and then on days 5 and 8 (3 and …6 days after the start of stimulation, respectively), at which times dry weight, DNA, alkaline phosphatase (ALP) activity, and bone Gla protein (BGP, osteocalcin) were measured. Both the dry weight and DNA showed a significant increase in the stimulated group by day 8, while the ALP activity showed a significant increase by day 5. The BGP began to increase in the stimulated group on day 5 in contrast to the control group in which it only increased on day 8. These results support the contention that mechanical stimulation promotes the differentiation of osteogenic cells and enhances bone formation. Since in this experimental model the acceleration of bone formation by mechanical stimulation can be reproduced in vitro, it is extremely useful for investigating the mechanisms underlying mechanical stimulation. Show more

Keywords: Osteogenesis, mechanical stimulation, alkaline phosphatase, osteocalcin, rat marrow cells

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 369-377, 1997

Authors: Yoshikawa, Takafumi | Peel, Sean A.F. | Gladstone, Janice R. | Davies, John E.

Article Type: Research Article

Abstract: Bone marrow cells obtained from rat femora were subjected to primary culture with 15% fetal bovine serum in the presence of 10^{-8} M dexamethasone, and following trypsin treatment 5 days later were seeded on Petriperm^{{\rm TM}} dishes which have a flexible bottom. After a 2‐day subculture, a cyclic stress consisting of a 1 s stretch (0.3% strain, 0.5 Hz) and a 1 s relaxation for 30 min every day was started. Culture tissue was removed on day 2 of the subculture (immediately prior to start of stimulation), and then on days 5 and 8 (3 and …6 days after the start of stimulation, respectively), at which times dry weight, DNA, alkaline phosphatase (ALP) activity, and bone Gla protein (BGP, osteocalcin) were measured. Both the dry weight and DNA showed a significant increase in the stimulated group by day 8, while the ALP activity showed a significant increase by day 5. The BGP began to increase in the stimulated group on day 5 in contrast to the control group in which it only increased on day 8. These results support the contention that mechanical stimulation promotes the differentiation of osteogenic cells and enhances bone formation. Since in this experimental model the acceleration of bone formation by mechanical stimulation can be reproduced in vitro, it is extremely useful for investigating the mechanisms underlying mechanical stimulation. Show more

Keywords: Osteogenesis, mechanical stimulation, alkaline phosphatase, osteocalcin, rat marrow cells

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 369-377, 1997

Authors: Li, Jianguo

Article Type: Research Article

Abstract: The purpose of this study was to compare the morphology of the tissues remaining on smooth and dimpled surfaces of a ceramic composite of zirconia–hydroxyapatite (TZ‐2Y/25HA) with commercially pure titanium (cp Ti) after a push‐out test. The tissue–material interface was viewed on the specimens without being tested mechanically. Cylindrical implants were inserted in the femurs of rabbits for three months. Each femur received three implants. After sacrificing the animals, the target tissues were collected and divided into two groups: group I was fixed in 4% formalin immediately, and group II was tested mechanically by push‐out before fixation. Specimens were then …dehydrated for SEM observation. The results showed that no remaining tissue appeared on the smooth cp Ti surface, whereas remaining tissues, mineralized and collagenous tissues, were seen on the smooth surface of the TZ‐2Y/25HA. New bone had grown into and filled the most of dimple spaces of both the cp Ti and TZ‐2Y/25HA implant. A submicron gap between the bone and cp Ti was found, whereas the TZ‐2Y/25HA was occasionally in direct contact with new bone. Thus TZ‐2Y/25HA showed an intimate contact to bone in some areas, and cp Ti showed an unmineralized tissue separated interface to bone continuously. Taken together, the laser machining seems to have no adverse effects on tissue response and is a potential technique for producing micro‐patterned surfaces on dental and medical implants. Show more

Keywords: Anti‐rotation, bone ingrowth, dimpled implant surface

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 379-385, 1997

Authors: Li, Jianguo

Article Type: Research Article

Abstract: The purpose of this study was to compare the morphology of the tissues remaining on smooth and dimpled surfaces of a ceramic composite of zirconia–hydroxyapatite (TZ‐2Y/25HA) with commercially pure titanium (cp Ti) after a push‐out test. The tissue–material interface was viewed on the specimens without being tested mechanically. Cylindrical implants were inserted in the femurs of rabbits for three months. Each femur received three implants. After sacrificing the animals, the target tissues were collected and divided into two groups: group I was fixed in 4% formalin immediately, and group II was tested mechanically by push‐out before fixation. Specimens were then …dehydrated for SEM observation. The results showed that no remaining tissue appeared on the smooth cp Ti surface, whereas remaining tissues, mineralized and collagenous tissues, were seen on the smooth surface of the TZ‐2Y/25HA. New bone had grown into and filled the most of dimple spaces of both the cp Ti and TZ‐2Y/25HA implant. A submicron gap between the bone and cp Ti was found, whereas the TZ‐2Y/25HA was occasionally in direct contact with new bone. Thus TZ‐2Y/25HA showed an intimate contact to bone in some areas, and cp Ti showed an unmineralized tissue separated interface to bone continuously. Taken together, the laser machining seems to have no adverse effects on tissue response and is a potential technique for producing micro‐patterned surfaces on dental and medical implants. Show more

Keywords: Anti‐rotation, bone ingrowth, dimpled implant surface

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 379-385, 1997

Authors: Kohles, Sean S. | Thielke, Robert J. | Vanderby, Jr., Ray

Article Type: Research Article

Abstract: The variety of techniques used to measure the cross‐sectional area of soft connective tissues during mechanical testing lead to inconsistencies in elastic descriptions. This study compares the numerical differences between finite elasticity (Eularian and Lagrangian formulations) and infinitesimal elasticity when considering stress, strain and elastic modulus of ligamentous tissue. Our results found stress differences (Cauchy versus Kirchhoff) of 22.4%, strain differences (engineering versus Green versus Almansi) as large as 14% and elastic modulus differences (Eularian versus Lagrangian) of 44% from ligament tissue sampled from rats. It is therefore critical to maintain consistent (energy conjugate) elastic formulations for reporting mechanical evaluation …of soft hydrated tissue. Show more

Keywords: Ligaments, stress, strain, elasticity

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 387-390, 1997

Authors: Kohles, Sean S. | Thielke, Robert J. | Vanderby, Jr., Ray

Article Type: Research Article

Abstract: The variety of techniques used to measure the cross‐sectional area of soft connective tissues during mechanical testing lead to inconsistencies in elastic descriptions. This study compares the numerical differences between finite elasticity (Eularian and Lagrangian formulations) and infinitesimal elasticity when considering stress, strain and elastic modulus of ligamentous tissue. Our results found stress differences (Cauchy versus Kirchhoff) of 22.4%, strain differences (engineering versus Green versus Almansi) as large as 14% and elastic modulus differences (Eularian versus Lagrangian) of 44% from ligament tissue sampled from rats. It is therefore critical to maintain consistent (energy conjugate) elastic formulations for reporting mechanical evaluation …of soft hydrated tissue. Show more

Keywords: Ligaments, stress, strain, elasticity

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 387-390, 1997

Authors: Assad, M. | Lemieux, N. | Rivard, C.H.

Article Type: Research Article

Abstract: We have evaluated a genotoxicity assay that combines in situ end‐labeling, colloidal gold tagging and electron microscopy in order to adapt it to the measurement of in vitro biomaterial‐induced genotoxicity. Human lymphocytes were cultured in semi‐physiological medium which had been previously exposed to biomaterial extracts of commercially pure titanium following ISO standards. In order to visualize the location of induced DNA strand breaks, cells were then exposed to exonuclease III which partially digests and amplifies lesions by releasing nucleotides at free 3' hydroxyl ends from nicked double‐stranded DNA. The resulting single‐stranded DNA was allowed to hybridize with short …oligonucleotides of random sequences including biotinylated dUTP. After random priming using Escherichia coli DNA polymerase I, incorporation of biotin‐dUTP was detected by immunogold binding to the chromatin. Cells exposed to a mutagenic concentration of methyl methanesulfonate, as a positive control, showed a significantly higher and stronger gold staining than both titanium‐exposed and unexposed specimens. This assay allows a precise localization and quantification of both in vitro DNA breakage and DNA repair. It could provide a powerful tool for rapid assessment of the genotoxic potential of new biomaterials. Show more

Keywords: Biocompatibility, genotoxicity, DNA damage, in situ end‐labeling, immunogold, electron microscopy

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 391-400, 1997

Authors: Assad, M. | Lemieux, N. | Rivard, C.H.

Article Type: Research Article

Abstract: We have evaluated a genotoxicity assay that combines in situ end‐labeling, colloidal gold tagging and electron microscopy in order to adapt it to the measurement of in vitro biomaterial‐induced genotoxicity. Human lymphocytes were cultured in semi‐physiological medium which had been previously exposed to biomaterial extracts of commercially pure titanium following ISO standards. In order to visualize the location of induced DNA strand breaks, cells were then exposed to exonuclease III which partially digests and amplifies lesions by releasing nucleotides at free 3' hydroxyl ends from nicked double‐stranded DNA. The resulting single‐stranded DNA was allowed to hybridize with short …oligonucleotides of random sequences including biotinylated dUTP. After random priming using Escherichia coli DNA polymerase I, incorporation of biotin‐dUTP was detected by immunogold binding to the chromatin. Cells exposed to a mutagenic concentration of methyl methanesulfonate, as a positive control, showed a significantly higher and stronger gold staining than both titanium‐exposed and unexposed specimens. This assay allows a precise localization and quantification of both in vitro DNA breakage and DNA repair. It could provide a powerful tool for rapid assessment of the genotoxic potential of new biomaterials. Show more

Keywords: Biocompatibility, genotoxicity, DNA damage, in situ end‐labeling, immunogold, electron microscopy

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 6, pp. 391-400, 1997