Bio-Medical Materials and Engineering - Volume 17, issue 5

Authors: Viano, A.M. | Spence, K.E. | Shanks, M.A. | Scott, M.A. | Redfearn, R.D. | Carlson, C.W. | Holm, T.A. | Ray, A.K.

Article Type: Research Article

Abstract: Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) is the material of choice for one of the articulating surfaces in many total joint replacements, notably hip and knee prostheses. The various methods used by the orthopaedic biomaterials industry to sterilize and anneal UHMWPE components, and the resulting oxidation and crosslinking, affect the mechanical wear resistance properties in ways still unknown at the microscopic and molecular levels. Transmission electron microscopy and chemical pyrolysis were used to quantify crosslinking induced by gamma irradiation and annealing in air. Changes in lamellar stacking and the amount of crosslinking suggest two types of crosslinking: relatively unstable crosslinks in the amorphous region …initially resulting from gamma irradiation which are later replaced by more thermally stable crosslinks resulting from rearrangements at the annealing temperature. Lamellar mobility, the ability of crystalline lamellae to flow in the material, is enhanced during the transition from one type of bond to the other, and this appears to optimize near eight hours of annealing time. Results from decomposition and percent crystallinity measurements provide further support for this theory. Show more

Keywords: Ultrahigh-molecular-weight polyethylene, lamellar structure, cross-linking

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 257-268, 2007

Authors: Kang, Sun-Woong | Yoo, Sung Pil | Kim, Byung-Soo

Article Type: Research Article

Abstract: Transplantation of cultured chondrocytes can regenerate cartilage tissue in cartilage defects. This method requires serial cell passages to expand chondrocytes to a large number of cells for transplantation. However, as chondrocytes are expanded in number in monolayer culture, the cells gradually lose their differentiated phenotype and may not form cartilage tissue. This study investigated whether chondrocytes cultured through various passages maintain their potential to reexpress a chondrogenic phenotype in three-dimensional scaffolds and form cartilage tissue in vitro and in vivo. The growth rate, viability, synthesis of collagen type I and II, and apoptotic activity of chondrocytes with passage number of …1, 2 and 5 were compared during in vitro culture. As the passage number increased, the cell growth rate and viability decreased and apoptotic cell increased. Passage 2 chondrocytes exhibited a high expression of collagen type II and a low expression of collagen type I. In contrast, passage 5 chondrocytes exhibited a low expression of collagen type II and a high expression of collagen type I, indicating chondrocyte dedifferentiation. To examine the ability of chondrocytes to regenerate cartilage tissues in vitro and in vivo, chondrocytes were expanded in vitro to passage number of 1 or 5, seeded onto biodegradable polymer scaffolds, and maintained in vitro or implanted into subcutaneous spaces of athymic mice for 1 month. Histological and immunohistochemical analyses of cartilage tissues engineered in vitro and in vivo with passage 1 chondrocytes showed mature and well-formed cartilage and the presence of highly sulfated glycosaminoglycans and type II collagen, a collagen type produced by differentiated chondrocytes. In contrast, tissues engineered in vitro and in vivo with passage 5 chondrocytes did not have chondrocyte morphology or cartilage-specific extracellular matrices (i.e., glycosaminoglycans and type II collagen). The results of this study show that chondrocyte passage number is an important factor affecting the quality of cartilage tissue-engineered with the chondrocytes, and that chondrocytes. Show more

Keywords: Cartilage, chondrocyte, passage number, tissue engineering

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 269-276, 2007

Authors: Santoni, Brandon G. | Pluhar, G. Elizabeth | Motta, Tatiana | Wheeler, Donna L.

Article Type: Research Article

Abstract: Synthetic grafting materials, such as calcium phosphates (hydroxyapatite, HA; tricalcium phosphate, TCP), polymers, or composites thereof, can be used as osteoconductive scaffolds and delivery vehicles for osteoinductive growth factors. Carrier materials must be engineered to deliver these factors in a controlled fashion at a rate and dose consistent with the biological need and responsiveness of the system to optimize bone formation and ingrowth. They should also simultaneously provide mechanical support and slowly resorb as new bone is formed. This investigation assessed the elution characteristics of BMP-7 (OP-1) from hollow calcium phosphate spheres of varying chemical composition (HA/β-TCP) and porosity …(dense/porous). The pharmacokinetics indicated a bimodal trend of protein release with protein elution peaking between fifteen and thirty minutes in solution (bolus release) and continuing through the eight-week time point (sustained release). Eluted OP-1 bioactivity was characterized over a three-week period using mesenchymal stem cell (MSC) cultures and included assessment of the protein's differential, proliferative, and calcified nodule forming abilities. Alkaline phosphatase enzyme (ALP) activity in MSCs peaked between 12 and 16 days post-OP-1 exposure. Elutant from the HA dense treatment group induced the highest degree of ALP expression while elutant from the β-TCP treatment groups induced the formation of significantly higher numbers of calcified nodules in culture. The aggregate modulus of a clinically relevant 2 cc dose of carriers was quantified using custom designed testing fixtures to investigate the effects of carrier size, porosity, chemical composition, and the presence of a central hole on mechanical integrity. Significant increases in moduli were noted for carrier size and chemical composition (HA>β-TCP). These preliminary in vitro and ex vivo results indicate the clinical potential of the hollow calcium phosphate carriers as successful load-bearing delivery vehicles for OP-1. Show more

Keywords: Biomaterials, biomechanics, drug delivery, bone regeneration, bone morphogenic protein, mesenchymal stem cell

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 277-289, 2007

Authors: Wan, Tao | Aoki, Hideke | Hikawa, Junta | Lee, Jun Hee

Article Type: Research Article

Abstract: A sputtering technique is an effective method for surface modification of materials, but there are many complex process parameters to influence on the physical and chemical properties of the sputtered coating films. In this paper the process parameters were investigated when the hydroxyapatite (HA) was coated onto various substrates including titanium (Ti), alumina ceramic (Al2 O3 ) and stainless steel (SUS) plates under various sputtering conditions, target type, Ar gas pressure, and discharge power. The deposition rate of HA was much higher in a solid plate target than in a powder lump target owing to the difference of apparent …density 75%, 18%, respectively. Ar gas pressure little influenced on the deposition rate. The HA coating thickness increased in proportion with discharge power. After hydrothermal treatment the thickness of HA slightly decreased, on the other hands Ca/P ratio slightly raised. The surface of the HA coating was smooth, homogeneous and dense. Show more

Keywords: Sputtering technique, hydroxyapatite, surface morphology, roughness

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 291-297, 2007

Authors: Nordberg, A. | von Holst, H. | Brolin, K. | Beckman, A.

Article Type: Research Article

Abstract: Purpose: The aim is to investigate fixation of cervical vertebral fractures by patching it with a composite laminate of adhesive and fibres, in comparison with use of only adhesives. Material and methods: The composite fixation was tested on bonded roe deer vertebrae. 25 specimens were sawed in two halves, creating a generic fracture, and thereafter bonded. The adhesives used were a dental system, Scotchbond XT, and a cyanoacrylate, M-bond 200. The fibres used were unidirectional carbon fibres and randomly distributed E-glass fibres. The composites were applied as a 7 mm wide patch circumferential along the induced fracture. Reference specimens for …comparison were also made. The ultimate tensile strength was tested in an Instron 5567. The failure site was examined with a microscope. Strain vectors were tracked using Digital Speckle Analysis. Results: Scotchbond XT + E-glass fibres gave best results, with a tensile strength of 3.5 N/mm circumferential length (24.3% of reference). All composites had lower stiffness than cortical bone. The dental adhesive fibre composites gave better results than the cyanoacrylate fibre composites. In all cases fibre reinforced adhesive composite gave better results than adhesive without fibre reinforcement. Conclusion: Fibre-adhesive composite is a promising technique for fixating cervical vertebral fractures. Show more

Keywords: Fracture, cervical vertebra, fixation, adhesive, composite

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 299-308, 2007

Authors: Padois, K. | Rodriguez, F.

Article Type: Research Article

Abstract: The Cementek® is a self-setting bone cement composed of a solid phase and a liquid phase. After mixing these two phases, it sets in situ to form an hydroxyapatite (HAp) as the only end product. It is difficult to introduce a new component into this cement without modifying the final product and its mechanical properties. In order to improve the mechanical properties of the Cementek® , a natural polymer (chitosan) was added in the initial formulation. Two types of chitosan were added into the Cementek® , at various concentration, in either the liquid or the solid phase. The effects …of chitosan addition on the properties of the self-setting bone cement are examined. The different composites were characterized by the determination of the setting time, the chemical transformation by X-ray diffraction and mechanical tests. The chemical transformations were not affected by the addition of chitosan neither in the liquid nor in the solid phase. The maturation towards HAp appeared to be complete for all the composites. The setting time was decreased by the addition of chitosan in the solid phase. However the setting time value of each composite remained compatible with a practical use in situ. This study shows that the maturation mode of the samples directly affects the mechanical properties of the obtained composites. The sterilization of the cement with chitosan has been studied. Show more

Keywords: Bone cement, biomaterial, chitosan, mechanical properties, γ-sterilization

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 309-320, 2007

Authors: Li, G. | Huang, J. | Li, Y. | Zhang, R. | Deng, B. | Zhang, J. | Aoki, H.

Article Type: Research Article

Abstract: Influence of a discrete nano-hydroxyapatite crystal (nano-HAp) on lymphatic leukemia P388 cell behavior was investigated by an in vitro technique using an MTT test and FITC analysis. The discrete nano-HAp was prepared by decanting upside clear layer of the nano-HAp suspension which was synthesized by a wet method using calcium hydroxide suspension and phosphoric acid solutions. The nano-HAp was identified as hydroxyapatite by the X-ray powder diffraction pattern and an infrared spectroscopy. The nano-HAp with concentrations of 8–40 μg/ml was dispersed into PRMI 1640 media with leukemia cells derived from BALB/C mice. The survival ratio of the cells decreased with …the amounts of the nano-HAp increasing. Apoptosis rates of leukemia P388 cells on co-culturing with the nano-HAp of 35 μg/ml for 24, 48 h were 14.5% and 45.8%, respectively, and higher than those of 10.4% and 34% in controls. The G0 /G1 peak values in leukemia P388 cell cycle were declined to reduce and the S peak values increased with extension time of co-culture. These results proved that the discrete nano-HAp can cause apoptosis of the leukemia P388 cells, and selectively act on G1 phase and arrest the G1 phase in cell cycle of the leukemia P388. Show more

Keywords: Discrete nano-hydroxyapatite, leukemia P388 cells, survival ratio, cell cycle

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 321-327, 2007

Authors: Meek, Marcel F.

Article Type: Letter

Citation: Bio-Medical Materials and Engineering, vol. 17, no. 5, pp. 329-334, 2007