Bio-Medical Materials and Engineering - Volume 14, issue 4

Authors: Scholtmeijer, K. | Janssen, M.I. | van Leeuwen, M.B.M | van Kooten, T.G. | Hektor, H. | Wösten, H.A.B.

Article Type: Research Article

Abstract: The physiochemical nature of surfaces can be changed by small proteins which are secreted by filamentous fungi. These proteins, called hydrophobins, are characterized by the presence of eight conserved cysteine residues and a typical hydropathy pattern. Upon contact with a hydrophilic–hydrophobic interface they self‐assemble into highly insoluble amphipathic membranes. As a result, hydrophobic surfaces become hydrophilic and vice versa. Genetic engineering of hydrophobins was used to study structure–function relationships. In addition, engineered hydrophobins were constructed to increase the biocompatibility of surfaces. The glycosylated N‐terminal region of the mature SC3 hydrophobin was deleted and the cell‐binding domain of human fibronectin was …introduced at the N‐terminus. The gross properties of the hydrophobins were not affected. However, the physiochemical properties of the hydrophilic side of the assembled protein did change. Growth of fibroblasts on Teflon could be improved by coating the solid with the engineered hydrophobins. Thus, by changing the N‐terminal part of hydrophobins, the physiochemical nature of the hydrophilic side of the assembled form can be altered and a variety of new functionalities introduced. The fact that hydrophobins self‐assemble at any hydrophilic–hydrophobic interface, irrespective of the chemical nature of the surface, therefore provides a generic approach to modify surfaces and make them interesting candidates for the use in various technical and medical applications. Show more

Keywords: , Biocompatibility, genetic engineering, hydrophobin, surface modification

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 447-454, 2004

Authors: Leegsma‐Vogt, Gea | Rhemrev‐Boom, Maria M. | Tiessen, Renger G. | Venema, Kor | Korf, Jakob

Article Type: Research Article

Abstract: Glucose or lactate biosensors are very useful for monitoring metabolism. Continuous monitoring of glucose is for example very important in diabetic patients. The measurement of lactate, a marker for oxygen deficiency, is used in the intensive care unit to monitor the patients' condition. In our laboratory we have developed two types of on‐line biosensors to measure in vivo glucose and lactate: a sandwich‐type biosensor and, very recently, a miniaturized flow‐through biosensor. These biosensors are not placed in the body itself, but are connected to implanted microdialysis or ultrafiltration probes. Both types of biosensors are based on the oxidation of substrate …using glucose oxidase or lactate oxidase and electrochemical detection. In the sandwich‐type sensor, the enzymes are physically immobilized between two cellulose nitrate filters, and operate with ferrocene as a mediator. In the miniaturized biosensor, with an internal volume of 10–20 nanolitres, the enzymes are immobilized on the electrode via in situ encapsulation in poly(1,3‐phenylenediamine). In this review we shall explain the working of these biosensors, and describe their application in clinical monitoring and experimental research. Show more

Keywords: Biosensor, glucose, lactate, monitoring

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 455-464, 2004

Authors: Saravanapavan, Priya | Jones, Julian R. | Verrier, Sophie | Beilby, Robert | Shirtliff, Victoria J. | Hench, Larry L. | Polak, Julia M.

Article Type: Research Article

Abstract: Bioactive materials are routinely used in dental and orthopaedic applications. The concept was first introduced in 1971, with the discovery of 45S5 Bioglass® , which is known to develop an interfacial bond between the implant and the host tissue. This glass is composed of SiO2 , CaO, P2 O5 and Na2 O. Since then numerous glasses and glass ceramics with similar compositions have been extensively studied for clinical applications. Until 1990 it was accepted that P2 O5 and Na2 O were necessary components for the glass composition to be bioactive. However, calcium silicate glasses with high SiO2 …content are impossible to produce using the traditional melt‐quench method. This is due to the liquid–liquid immiscibility region that is present between 0.02 and 0.3 mole fraction of CaO and in terms of bioactivity, high CaO compositions were inferior to those quaternary bioactive glass compositions already in existence. In the last few years several studies have been reported regarding the production of CaO–SiO2 glasses via the sol–gel processing technique. This report summarises the findings of the past and the present and also outlines potential of these calcium silicate gel‐glasses in the field of biomaterials. Show more

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 467-486, 2004

Authors: Baroud, G. | Bohner, M. | Heini, P. | Steffen, T.

Article Type: Research Article

Abstract: The incidence of osteoporotic bone fractures is growing exponentially as the western population ages and as life expectancy increases. Vertebroplasty, where acrylic or calcium phosphate cement is injected into the weakened vertebrae to augment them, is an emerging procedure for treating spinal fragility fractures. However, cement injection is currently limited because there are no clear standards for a safe, reproducible and predictable procedure. The purpose of this paper is to examine the role that bone cements play in the underlying bio‐mechanisms that affect the outcomes of cement injection. Our most important finding after combining clinical, laboratory and theoretical research is …that the process of cement injection poses conflicting demands on bone cements. The cements are required to be more viscous and less viscous at the same time. The challenge therefore is to develop biomaterials, techniques and/or devices that can overcome or manage the conflicting demands on cement viscosity. Show more

Keywords: Vertebroplasty, biomaterials, acrylic and calcium‐phosphate bone cements, injectability, extravasation, injection forces

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 487-504, 2004

Authors: Kobayashi, Masanori

Article Type: Research Article

Abstract: The importance of knee meniscus function is now recognized, and the treatment of meniscus injury has been changing from resection to repair. However, depending on the type of injury, meniscectomy sometimes cannot be avoided. In such case, it is important to anticipate the future problem of degenerative change or osteoarthrosis in knee joint. In future, autograf using regenerative meniscus will be developed by tissue engineering. However, even if it will be possible, considering the healing period, the young athlete with severe meniscus injury may select meniscectomy in order to return to sports life as early as possible avoiding the …long immobilization or declining sports skill. In consideration of the prognosis and circumstances in such patients, we need a artificial meniscus for salvage. To assess further the use of polyvinyl alcohol‐hydrogel (PVA‐H) artificial meniscus, we performed some mechanical tests about PVA‐H and animal experiment. In mechanical tests, we found that a high water content PVA‐H showed viscoelastic behaviour similar to that of human meniscus. Moreover, the frictional coefficient of PVA‐H against natural articular cartilage was also effective. In the animal experiment using rabbits, the lateral meniscus was replaced with an artificial meniscus in one knee side and lateral meniscectomy was performed in another knee side of each rabbit. We have already reported the results up to 1 year after operation, present study investigated the results in postoperative 1.5 years. In the results, the articular cartilage state of knee joint implanted PVA‐H meniscus was good even after 1.5 years, while OA change progressed in meniscectomy knee joint. In addition, neither wear nor breakage of PVA‐H was observed. These results proved that an artificial meniscus using a high water content PVA‐H can compensate for meniscal function and might be clinically applicable. Show more

Keywords: Polyvinyl alcohol‐hydrogel (PVA‐H), meniscectomy, osteoarthritis (OA), artificial meniscus, high water content

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 505-515, 2004

Authors: Suuronen, Riitta | Kontio, Risto | Ashammakhi, Nureddin | Lindqvist, Christian | Laine, Pekka

Article Type: Research Article

Abstract: Bioabsorbable fixation devices have been used in craniomaxillofacial (CMF) surgery since the early 70's. In our departments the experimental use started in the 80's with self‐reinforced (SR) polylactide devices. The first clinical operations were carried out in 1991. Since that time, we have used different types of self‐reinforced bioabsorbable devices in the fixation of several hundreds of osteotomies and fractures. Patients' acceptance has been generally excellent and very few complications occurred during this follow‐up of over 10 years. The complications have been minor and have not affected the end results of the operations. In only one oncologic patient, the devices …needed to be removed and replaced with a rigid reconstruction plate. The minor complications consisted mainly of a few infections, dehiscence of the wound and plate exposure together with granulation tissue in the operation field. No implant‐specific complications were recorded. However, there is a learning curve for the surgeon, as there is with all new methods introduced. Based on our experience, self‐reinforced bioabsorbable devices are safe to be used in several indications in the craniomaxillofacial skeleton, also in load‐shearing situations. Show more

Keywords: Craniomaxillofacial surgery, resorbable, absorbable, bone plates and screws

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 517-524, 2004

Authors: Krupa, D. | Baszkiewicz, J. | Kozubowski, J.A. | Lewandowska‐Szumieł, M. | Barcz, A. | Sobczak, J.W. | Biliński, A. | Rajchel, A.

Article Type: Research Article

Abstract: This paper is concerned with the corrosion resistance and biocompatibility of titanium after surface modification by the ion implantation of calcium or phosphorus or calcium + phosphorus. Calcium and phosphorus ions were implanted in a dose of 1017 ions/cm2 . The ion beam energy was 25 keV. The microstructure of the implanted layers was examined by TEM. The chemical composition of the surface layers was determined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37°C. The biocompatibility was evaluated in vitro. As shown by TEM …results, the surface layers formed during calcium, phosphorus and calcium + phosphorus implantation were amorphous. The results of the electrochemical examinations (Stern's method) indicate that the calcium, phosphorus and calcium + phosphorus implantation into the surface of titanium increases its corrosion resistance in stationary conditions after short‐ and long‐term exposures in SBF. Potentiodynamic tests show that the calcium‐implanted samples undergo pitting corrosion during anodic polarisation. The breakdown potentials measured are high (2.5 to 3 V). The good biocompatibility of all the investigated materials was confirmed under the specific conditions of the applied examination, although, in the case of calcium implanted titanium it was not as good as that of non‐implanted titanium. Show more

Keywords: Titanium, ion implantation, corrosion resistance, biocompatibility

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 525-536, 2004

Authors: Goto, Tetsuya | Yoshinari, Masao | Kobayashi, Shigeru | Tanaka, Teruo

Article Type: Research Article

Abstract: The interaction between implant materials and bone cells or oral epithelial (OE) cells contributes to the clinical success of dental implants. The functional activity of cells in contact with an implant is determined by its surface properties. Before cells attach, extracellular matrix (ECM) in the serum deposits on the substrate; rounded cells then attach and spread upon it. Cells form focal adhesions and polarize, then start to migrate or proliferate to form colonies. Comparison of the attachment and behavior of osteoblastic cells on titanium (Ti) and hydroxyapatite (HA) revealed that more cells attached on HA and that these spread more …rapidly than on Ti. In contrast, cells did not form good stress fibers or vinculin‐positive focal adhesions on HA, whereas the cells on Ti possessed well‐defined and polarized stress fibers. The initial attachment of OE cells to Ti was inferior to that on polystyrene culture dish or glass, and the OE cell migration area, indicated by the deposition of LN5, was smaller on Ti than on the other materials. This review summarizes data on the attachment and behavior of osteoblastic cells and OE cells on biomaterials, which may suggest future improvements in surface properties. Show more

Keywords: Cell attachment, behavior, oral epithelial cell, osteoblast, titanium

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 537-544, 2004

Authors: Anselme, K. | Bigerelle, M. | Loison, I. | Noël, B. | Hardouin, P.

Article Type: Research Article

Abstract: Intercellular adhesions are known to play an important role in differentiation of osteoblasts and in the development of bone tissue architecture. However, to our knowledge, they have never been studied during the formation of bone tissue in contact with a biomaterial surface. In an in vitro kinetic study, we followed the expression of proteins involved in cell–cell interactions (β‐catenin), in cell–material interactions (vinculin) and in cytoskeleton (actin) of human osteoblastic cells cultured on grooved titanium‐based substrates during 1, 2, 4, 6, 24, 48, and 72 hours. The human osteoblasts aligned themselves in the 150 μm wide grooves only after 24 …hours. The distribution of vinculin‐positive focal contacts, actin cytoskeleton and β‐catenin positive‐adherens junctions was not significantly influenced by the cell alignment. β‐catenin‐positive adherens junctions were expressed by human osteoblasts as soon as 1 hour after inoculation. At this time, they showed a patch‐like aspect along cytoplasmic processes in contact with an underlying or an adjacent cell. After 2 hours, the patches were more and more numerous underlining the connections between cells. After 4 hours and more, the patches were organised in a parallel arrangement perpendicular to the two connected cells forming a “zip‐like” aspect. Additionally, using double immuno‐staining, we demonstrated that sometimes β‐catenin and vinculin appeared co‐localised and sometimes not. The linkage of catenin/cadherin complex and vinculin‐positive focal contacts with actin filaments may explain this apparent co‐localisation. Show more

Keywords: Adhesion, β‐catenin, vinculin, osteoblast, titanium, actin, human

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 545-556, 2004

Authors: Lori, J.A. | Nok, A.J.

Article Type: Research Article

Abstract: Mucin is the main salivary protein in the mouth of animals including man. The present study aims at investigating the role of electrostatic interactions in the adsorption of mucin to titanium in vitro. The binding profile of mucin to titanium was analyzed according to an adsorption isotherm. Mucin was dissolved and the solution suspended with native, calcium, magnesium, or potassium treated commercially pure Ti powder, at pH 3.0 and 7.4. The amount of unabsorbed protein in the supernatant fluid was measured. The maximum amount of adsorbed mucin was 0.11 mg/1.0 g of Ti. The mucin–Ti association constant was estimated to …be 2.91 ml/mg. Pretreatment of Ti with calcium, or magnesium alone, or combined resulted in increased adsorption of mucin to Ti. No increase in adsorption was recorded following pretreatment of Ti with potassium. The results indicate the involvement of electrostatic interactions in the absorption of mucin to Ti. Show more

Keywords: Mucin, protein‐binding, titanium absorption

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 557-563, 2004

Authors: Towler, M.R. | Kenny, S. | Boyd, D. | Pembroke, T. | Buggy, M. | Hill, R.G.

Article Type: Research Article

Abstract: Zinc polyalkenoate cements (ZPCs) and glass polyalkenoate cements (GPCs) are used routinely in dentistry, but have potential for orthopaedic applications as they set at body temperature without shrinkage or significant heat evolution. However, the materials have drawbacks; ZPCs are biocompatible in implant studies, but a fibrous collagen capsular layer forms adjacent to the cement. GPCs are bioactive in the bone environment as a result of the release of calcium, phosphate and fluoride ions, as well as the formation of a silicious gel phase, but research has shown that aluminum ions released result in defective bone mineralisation and as a consequence …the ability of these cements to chemically bond to bone is lost. Two approaches have been developed to overcome these problems. The ZPC route considers a ZnO : hydroxyapatite (HA) : poly(acrylic acid) (PAA) mixture, the HA incorporated to improve bioactivity. The GPC route employs a calcium zinc silicate glass; the zinc taking the role that aluminum plays in conventional GPCs. This study has shown that cements can be formulated by an acid base reaction between PAA and both calcium zinc silicate glasses (GPCs) and a mixture of hydroxyapatite and zinc oxide (ZPCs). The moduli of these cements are comparable to both bone and conventional acrylic cements, highlighting their potential for biomedical applications. Unfortunately, both materials have previously been shown to be toxic by cell culture methods, as a result of high zinc ion release, and so it is necessary to study ion release profiles of the cements in order to determine the magnitude of this release. Considering the ZPCs, the modulus of the cement has an inversely proportional relationship to the zinc ion release. From the data presented it is clear that increases in polymer concentration results in lower amounts of zinc ions being released, whilst molar mass of the PAA has no influence. Therefore it would appear that polymer concentration has a significant influence over ion release. Generally, the amount of Zn2+ released decreases with increasing HA content and/or decreasing ZnO content. Considering the GPCs, the materials are all seen to release large amounts of the active ion, when compared to the commercial versions. The extent of this release increases with temperature and agitation. The release could be minimised by an increased P : L mixing ratio, and an increased PAA concentration, which would produce a more cross‐linked cement matrix. Minimising the release of the active ion should improve the in vitro bioactivity of both materials. However, for a full understanding of the clinical benefits of such materials, an in vivo study would be required. Show more

Keywords: Glass polyalkenoate cements, ion release, modulus

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 565-572, 2004

Authors: Bigi, A. | Boanini, E. | Gazzano, M. | Rubini, K. | Torricelli, P.

Article Type: Research Article

Abstract: The direct synthesis of hydroxyapatite–poly‐L‐aspartic acid (HA–PASP) nanocrystals has been carried out in presence of increasing amounts of PASP in solution up to 56 mmol/l. WAXS, TEM, TGA, IR and chemical analyses were used to characterize the structure, morphology and composition of the products. PASP is quantitatively incorporated into HA crystals, provoking a reduction of the coherent length of the crystalline domains. Furthermore, composite crystals display a greater length/width ratio with respect to the control HA crystals, and show a remarkable trend towards aggregation. The broadening of the X‐ray diffraction reflections indicate a reduction of the coherent length along the …long dimension 002 and the cross section 310 of the apatite crystals. The comparison between the morphological and structural data allows to suggest a specific interaction between PASP and HA structure. Show more

Keywords: Hydroxyapatite, poly‐L‐aspartic acid, nanocrystals, crystal size, X‐ray diffraction

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 573-579, 2004

Authors: Kalkura, S. Narayana | Anee, T.K. | Ashok, M. | Betzel, C.

Article Type: Research Article

Abstract: An easy method to crystallise homogenous HAP at physiological pH as well as powders of HAP and CPP at low temperature are described. Platy and spherulitic crystals of HAP were crystallised at the physiological pH using single diffusion method. Well‐defined platy crystals of hydroxyapatite were obtained at the physiological temperature and pH. These crystals were found to be pure and homogenous form of HAP without any contamination from the crystallising medium. Spherulitic crystals of HAP of approximately 3 mm in diameter were obtained in the presence of Fe at 47°C. A sol‐gel technique involving agarose is described for the preparation …of hydroxyapatite and calcium pyrophosphate. Pure form of HAP was synthesised at 85°C and its sintering properties were also studied. At a temperature of 1200°C, the material gets completely converted to α‐calcium pyrophosphate. The samples were analysed by XRD, IR, TGA and SEM. The particle size of the synthesised powders was measured using the dynamic light scattering experiments. Show more

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 581-592, 2004

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 593-600, 2004

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 4, pp. 601-603, 2004