Bio-Medical Materials and Engineering - Volume 18, issue 1

Authors: Shabalovskaya, S. | Anderegg, J. | Rondelli, G. | Vanderlinden, W. | De Feyter, S.

Article Type: Research Article

Abstract: Comparative fibrinogen adsorption and platelet morphology were evaluated on a wide array of well-characterized Nitinol surfaces (polished, chemically etched, boiled in water, electropolished in different electrolytes and heat treated). XPS, SEM, AFM, atomic adsorption spectroscopy and electrochemistry were employed to acquire information on surface chemistry, topography and Ni release. Obtained surfaces, of various topographies and crystallinity from mostly amorphous to nano-crystalline with Ni concentration from 1 to 8%, induced Ni release into biological medium in a subtoxic range (0–11 ng/ml/cm2 ). Fibrinogen adsorption to Nitinol surfaces ranged from that characteristic to pure Ni (130 ng/cm2 ) to pure Ti (300 …ng/cm2 ). It was directly proportional to the Ti surface concentration and correlated with open circuit potential related to surface charge. Human platelet morphology varied from round to fully spread depending on surface treatment. Base layer of fully spread cells detected on all surfaces could be even and smooth with no propensity for thrombosis or sticky causing platelet aggregation and thrombus-like structures. Using appropriate surface treatments thrombogenicity of Nitinol can be manipulated to satisfy both the requirements for stents and defect closures. Show more

Keywords: NiTi surface topography, roughness, nickel release, fibrinogen, platelets, open circuit potential, thrombogenicity

Citation: Bio-Medical Materials and Engineering, vol. 18, no. 1, pp. 1-14, 2008

Authors: Brochhausen, Christoph | Zehbe, Rolf | Gross, Ulrich | Libera, Jeanette | Schubert, Helmut | Nüsing, Rolf M. | Klaus, Günter | Kirkpatrick, C. James

Article Type: Research Article

Abstract: Tissue engineering of articular cartilage remains an ongoing challenge. Since tissue regeneration recapitulates ontogenetic processes the growth plate can be regarded as an innovative model to target suitable signalling molecules and growth factors for the tissue engineering of cartilage. In the present study we analysed the expression of cyclooxygenases (COX) in a short-term chondrocyte culture in gelatin-based scaffolds and in articular cartilage of rats and compared it with that in the growth plate. Our results demonstrate the strong cellular expression of COX-1 but only a focal weak expression of COX-2 in the seeded scaffolds. Articular cartilage of rats expresses homogeneously …COX-1 and COX-2 with the exception of the apical cell layer. Our findings indicate a functional role of COX in the metabolism of articular chondrocytes. The expression of COX in articular cartilage and in the seeded scaffolds opens interesting perspectives to improve the proliferation and differentiation of chondrocytes in scaffold materials by addition of specific receptor ligands of the COX system. Show more

Keywords: Articular cartilage, tissue engineering, growth plate, cyclooxygenases, chondrocytes

Citation: Bio-Medical Materials and Engineering, vol. 18, no. 1, pp. 15-23, 2008

Authors: Fukui, N. | Sato, T. | Kuboki, Y. | Aoki, H.

Article Type: Research Article

Abstract: The purpose of this study was to develop a new biodegradable bone substitute materials consisting of synthesized nano-size hydroxyapatite (nano-HAp) and Type I biodegradable honeycomb collagen sponge (HCS) composites. Bone defects in rabbit mandibles were prepared by a drill, and the composites were implanted into the bone defects. The HCS only and the HCS/calcined hydroxyapatite (HAp) composite were used as comparative materials. The bone tissues reaction at the early stage within 3 weeks after implantaion was investigated histologically. Amounts of new bone formation were determined by NIH-image analysis software using the histological sections. The amounts of the new bone formation …were largest in the nano HAp/HCS compared to the comparative materials. Within 2 weeks after implantation, the nano-HAp/HCS composite was more rapidly exchanged by new bone than the comparative materials. From these results it was considered that the nano-HAp/HCS composites can be used as an effective biodegradable bone substitutive material. Show more

Keywords: Nano-hydroxyapatite/honeycomb collagen sponge composite, bone tissue reaction, biodegradable

Citation: Bio-Medical Materials and Engineering, vol. 18, no. 1, pp. 25-33, 2008

Authors: John, Lindsay C.H.

Article Type: Research Article

Abstract: Sternal dehiscence is an important complication of cardiac surgery. A simple mathematical analysis is described for determining the relative strength (S) of different types of sternal closure. This is based upon resolving the tensions within the segments of a sternal wire to derive a dehiscence force. The strength of the closure (S) is the ratio of the volume of sternum which the dehiscence force acts upon to the dehiscence force itself. The derived S values varied from 4.3 for a closure using 6 transverse wires to 11.4 for a closure using the Modified Technique. The analysis suggested that closures which …redistribute the transverse force to act obliquely upon a greater volume of sternum, such as the Modified Technique, are less likely to fail. Show more

Keywords: Sternum, cardiac surgery, surgical wound dehiscence

Citation: Bio-Medical Materials and Engineering, vol. 18, no. 1, pp. 35-44, 2008

Authors: Joyce, T.J.

Article Type: Research Article

Abstract: The key joint of the forefoot during gait is the first metatarsophalangeal joint. It plays an important role in propelling the human form but can be subject to a number of diseases which can lead to its replacement with an artificial joint. Some of these designs of prosthesis employ a two-piece ball and socket arrangement and are available with a range of biomaterial couples including ceramic-on-ceramic, metal-on-metal and metal-on-polymer. Calculation of predicted lubrication regimes applicable to these implant designs was undertaken. Modelling the ball and socket implant as an equivalent ball-on-plane model and employing elastohydrodynamic theory allowed the minimum film …thickness to be calculated and in turn the lambda ratio to indicate the lubrication regime. The calculations were undertaken for a 50 to 1500 N range of loading values, a 0 to 30 mm/s range of entraining velocities, and a 3 to 15 mm radius range of sizes. Calculations showed that the ceramic-on-ceramic and metal-on-metal implants could operate under fluid film lubrication, whereas the metal-on-polymer combination operated in the boundary lubrication regime. It was also recognized that manufacturing capabilities are critical to the radial clearances and values of surface roughness that can be achieved, and thus the predicted lubrication regime. Show more

Keywords: Metatarsophalangeal, lubrication regimes, metal-on-metal, ceramic-on-ceramic, metal-on-polymer

Citation: Bio-Medical Materials and Engineering, vol. 18, no. 1, pp. 45-51, 2008