Thermal preparation of highly porous calcium phosphate bone filler derived from marine algae.

A sustainable marine-derived bioceramic with a unique porous structure has been developed for hard tissue repair. The conversion of alga was achieved through a novel technique, involving well controlled thermal processing followed by low pressure-temperature hydrothermal synthesis. In its preparation, a heat treatment step was required to remove the organic compounds from the algae, which reinforces the mineralised matrices. Its removal is necessary to prevent issue such as immune biocompatibility and ensure phase purity of the resultant biomaterial. This paper investigates the hydrothermal technique used for the transformation of mineralised red algae to hydroxyapatite that preserves the algae's unique structure. It specifically focuses on the effects of heat treatment on the morphology of the algae, TGA, SEM and hot stage XRD to quantity the changes.

Evaluation of inherent toxicology and biocompatibility of magnesium phosphate bone cement.

Magnesium phosphate cement (MPC) is a kind of novel biodegradable bone adhesive for its distinct performance. However, there is few research work concerning on the systemic biocompatibility and genetic toxicological evaluation of MPC. In this study, the investigation on the inherited toxicology of MPC including gene mutation assay (Ames test), chromosome aberration assay (micronucleus test), and DNA damage assay (unscheduled DNA synthesis test) were carried out. Fracture healing and degradation behavior were explored for the evaluation of the biocompatibility of MPC, using macroscopical histological, histomorphometrical, and scanning electron microscopical methods. The results of mutagenicity and potential carcinogenicity of MPC extracts were negative, and the animal implantation illustrated no toxicity and good resorption. The study suggested that bioresorbable MPC was safe for application and might have potential applications for physiological fracture fixation.

[Extraction and application of Perna viridis foot protein as bioadhesive].

Mussel adhesive proteins have attracted increasing interests for their potential use as environmentally friendly bioadhesives in medicine and aqueous conditions. In this study, surface coating analysis, quartz crystal microbalance (QCM), cell and bone tissue adhesion and cytotoxicity assay were used to study the properties of the Perna viridis foot proteins (Pvfp) extract as bioadhesive. The results of coating ability on various materials and QCM analysis revealed that Pvfp extract has comparable or superior adsorbtion ability to that of Cell-Tak (the naturally extracted MAP mixture from Mytilus edulis, and has been commercialized), and also, the cell adhesion ability of Pvfp extract was stronger than that of Cell-Tak and poly-L-lysine. No cytotoxicity was detected using human HeLa and 293T cells. Furthermore, broken bones of mouse could be stuck together by use of Pvfp extract. In bulk-scale adhesion tests, Pvfp extract showed much greater tensile strength than did fibrin glue for conglutinating poly (vinl chloride) sticks and for binding together pig's femur segments. These results suggested that Pvfp extract be an efficient cell and tissue adhesive in biotechnological application and it might be a potential bioadhesive in medical practice.

Injectable acrylic bone cements for vertebroplasty based on a radiopaque hydroxyapatite. Formulation and rheological behaviour.

The utilization of injectable acrylic bone cement is crucial to the outcome of vertebroplasty and kyphoplasty. However, only a few cements that are in clinical use today are formulated specifically for use in these procedures and even these formulations are not regarded as "ideal" injectable bone cements. The aim of this work is to prepare bioactive bone cements by adding strontium hydroxyapatite (SrHA) to a cement formulation based on polymethylmethacrylate. Thus, the cement combines the immediate mechanical support given by the setting of the acrylic matrix with optimum radiopacity and bioactivity due to the incorporation of the SrHA. Formulations of bioactive cement were prepared with 10 and 20 wt% of SrHA as synthesised and after a surface treatment with the monomer. Cements loaded with treated particles showed an enhancement of their handling properties, and hence, an improvement on their rheological behaviour, injectabilities and compressive parameters. Further experiments were also carried out to determine their bioactivity and biocompatibility and results appear in other publication.

Contact killing antimicrobial acrylic bone cements: preparation and characterization.

Novel antimicrobial poly(methyl methacrylate) (PMMA)-based bone cement was synthesized by co-polymerizing PMMA/MMA with various percentages of quaternary amine dimethacrylate (QADMA) by free radical bulk polymerization technique at room temperature using benzoyl peroxide and N,N-dimethyl-p-toulidine (DMPT) as a redox initiator. The modified bone cement was characterized by FT-IR and 1H-NMR spectral studies. The thermal and physical properties of the bone cements of varying composition of QADMA were evaluated by thermogravimetric analysis (TGA), differential calorimetry (DSC) and contact angle measurements. Peak exothermic temperature was observed to decrease, while setting time increased with increase in QADMA content in the bone cement formulations. The antibacterial activity of the synthesized bone cement containing quaternary amine dimethacrylate against Escherichia coli and Staphylococcus aureus was studied by zone of inhibition, colony count method and scanning electron microscopy (SEM). QADMA containing acrylic bone cement showed a broad spectrum of contact killing antimicrobial properties. Retention of E. coli onto the surface of PMMA bone cement was observed, whereas there was complete prevention of retention of E. coli onto the modified PMMA bone cement with 15% QADMA. The studies were compared with the acrylic bone cement synthesized using 15% N-vinyl-2-pyrrolidone (NVP) in place of QADMA to which iodine was added as an antimicrobial agent during co-polymerization.

Apatite formation in the reaction-setting mixture of Ca(OH)2--KH2PO4 system.

Development of a new calcium phosphate cement (CPC) system as an alternative to that commonly used, basically consisting of tetracalcium phosphate and dicalcium phosphate self-setting mixtures, could be of interest in achieving special properties of the product. Powder mixtures of Ca(OH)(2) and KH(2)PO(4) were studied to assess their potential for the precipitation of apatite-like phase with the use of potassium phosphate salt solution as the cement liquid. X-ray diffraction and infrared (IR) spectroscopy studies and pH and setting time measurements were performed. The set cement was revealed to consist of a low crystalline carbonate-substituted apatite-like phase. The setting time of the cement was about 5 min. Its dissolution in distilled water led to an increase in solution pH to about 11.5, the pH slowly decreasing to 10.2 at day 10. The results showed the cement to be of an increased carbonate substitution ability compared to the tetracalcium phosphate-dicalcium phosphate anhydrous cement.

Fatigue testing and performance of acrylic bone-cement materials: state-of-the-art review.

Over the past three decades or so, a very large volume of literature has been generated on the impact of an assortment of variables on the fatigue lifetimes of a large number of acrylic bone-cement formulations. In the present article, this literature is examined critically to reveal areas of agreement, areas of disagreement, as well as a welter of underexplored and unexplored topics. For example, there is unanimity of support for the notion that an increase in the molecular weight of the powder constituents or the fully cured cement leads to an increase in the cement's fatigue life, whereas there is disagreement as to whether vacuum mixing the cement constituents leads to an increase in the fatigue life of the fully cured cement (relative to the hand-mixed counterpart). Among the underexplored topics is systematic study of the effect of test frequency on the fatigue results, whereas determination of the optimal concentration of the antibiotic in an antibiotic-loaded cement is an example of the unexplored topics. It is pointed out that resolving the controversies, addressing the underexplored topics, and filling the lacunae will allow comprehensive evaluations of acrylic bone-cement materials to be made. This enhanced body of knowledge will prove invaluable in the continued use of acrylic bone cement as the anchoring agent in cemented arthroplasties.

Preparation of macroporous calcium phosphate cement tissue engineering scaffold.

Unlike sintered hydroxyapatite there is evidence to suggest that calcium phosphate cement (CPC) is actively remodelled in vivo and because CPC is formed by a low-temperature process, thermally unstable compounds such as proteins may be incorporated into the matrix of the cement which can then be released after implantation. The efficacy of a macroporous CPC as a bone tissue engineering scaffold has been reported; however, there have been few previous studies on the effect of macroporosity on the mechanical properties of the CPC. This study reports a novel method for the formation of macroporous CPC scaffolds, which has two main advantages over the previously reported manufacturing route: the cement matrix is considerably denser than CPC formed from slurry systems and the scaffold is formed at temperatures below room temperature. A mixture of frozen sodium phosphate solution particles and CPC powder were compacted at 106 MPa and the sodium phosphate was allowed to melt and simultaneously set the cement. The effect of the amount of porogen used during processing on the porosity, pore size distribution and compressive strength of the scaffold was investigated. It was found that macroporous CPC could reliably be fabricated using cement:ice ratios as low as 5:2.

Bone bonding behavior of the hydroxyapatite containing glass-titanium composite prepared by the Cullet method.

Bioactive composites composed of hydroxyapatite containing glass (HA-G) as a coating and titanium (Ti) or titanium alloy implants as a substrate were prepared by the Cullet method. This method results in the HA-G coating layer on the substrate with a compositional gradient in HA concentration. The results of in vitro and in vivo experiments investigating the characteristics of the composite materials are reported and discussed in this article. In vitro evaluations confirmed that the Cullet method was suitable for the preparation of the functionally gradient composite implants with higher reliable quality. In vivo experiments permitted evaluation of bonding strength of these composite implants to living bone tissue. Mechanical pull-out tests indicated that the implants bonded to living bone at least as firmly as those by the conventional method, and that the adhesion between the HA-G coating layer and metal substrate was well integrated and strongly maintained in vivo. SEM observations with EDX and a histological study of the interface between the HA-G-Ti composite implants and bone tissue revealed not only that the implants bonded to bone directly without any intervening tissue but that bone ingrowth into the HA-G layer occurred. The HA-G-Ti composite implants demonstrate both biocompatible and osteoconductive characteristics, and may be expected to obtain good and lasting results when applied clinically.

Influence of mixing technique on some properties of PMMA bone cement.

PMMA bone cements (Refobacin-Palacos R, Sulfix 6, AKZ, and CMW bone cement, types I and II), from six different clinics, were investigated in three stages. In the first stage, studies of density, hardness, flexural strength, and compressive strength were made, as well as molecular weight measurements and microscopic investigations. These studies reflected the current state of techniques of application used in operating theaters. They revealed wide variations in the properties of the materials studied. Secondly, a comprehensive study of the process-technology in the laboratory was performed. The following variables were investigated or discussed: mixing vessel, order of the individual components, mixing time, rate of mixing, pressure application on the mixed bone cement, kneading, cement thickness, pouring into the syringe, contact force during polymerization, and preparation quantity. The third stage involved the development and clinical testing of an improved mixing technique. Using this improved mixing technique, all three selected clinics achieved far better results with reduced variability. A comparison between a centrifuging technique after mixing and our improved, but conventional, mixing technique, displays advantages for the latter. The question regarding a correlation between cement specimens of high porosity and early implant loosening could not be answered on the basis of the 43 PMMA bone cement explants investigated (implanted 6 months to 15 years). In some cases, the studies revealed that the bone cement manufacturers should be required to revise and quantify existing instructions for use. The users, on the other hand, should give more consideration to the mixing technique and its consequences.