Bio-Medical Materials and Engineering - Volume 14, issue 4
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Bio-Medical Materials and Engineering is to promote the welfare of humans and to help them keep healthy. This international journal is an interdisciplinary journal that publishes original research papers, review articles and brief notes on materials and engineering for biological and medical systems.
Articles in this peer-reviewed journal cover a wide range of topics, including, but not limited to: Engineering as applied to improving diagnosis, therapy, and prevention of disease and injury, and better substitutes for damaged or disabled human organs; Studies of biomaterial interactions with the human body, bio-compatibility, interfacial and interaction problems; Biomechanical behavior under biological and/or medical conditions; Mechanical and biological properties of membrane biomaterials; Cellular and tissue engineering, physiological, biophysical, biochemical bioengineering aspects; Implant failure fields and degradation of implants. Biomimetics engineering and materials including system analysis as supporter for aged people and as rehabilitation; Bioengineering and materials technology as applied to the decontamination against environmental problems; Biosensors, bioreactors, bioprocess instrumentation and control system; Application to food engineering; Standardization problems on biomaterials and related products; Assessment of reliability and safety of biomedical materials and man-machine systems; and Product liability of biomaterials and related products.
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.
Keywords: Glass polyalkenoate cements, ion release, modulus
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.
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.