Phosphate coatings assessment

Proteins such as rhBMP can be incorporated into calcium phosphate layers when biomimetically co-precipitated with the inorganic components (Liu et al., 2004). For example, rhBMP-2 (0.1-10pgml-1) retains its osseoinductive potential when incorporated into the crystal lattice of hydroxyapatite in a dose-dependent manner as ascertained by protein blot staining and enzyme-linked immunosorbent assay (ELISA). The positive osseogenicity of rhBMP-2 was assessed quantitatively by monitoring ALP activity (see Section 7.10.3.1) on rat BMSCs grown directly on the calcium phosphate coatings. 

As with chemical etches, developing optimum conversion coatings requires assessment of the microstructure of the steel. Correlations have been found between the microstructure of the substrate material and the nature of the phosphate films formed. Aloru et al. demonstrated that the type of phosphate crystal formed varies with the orientation of the underlying steel crystal lattice [154]. Fig. 32 illustrates the different phosphate crystal morphologies that formed on two heat-treated surfaces. The fine flake structure formed on the tempered martensite surface promotes adhesion more effectively than the knobby protrusions formed on the cold-rolled steel. 

A nonisotopic ELISA method in which serum specimens are added to microtiter wells coated with human Tg is also available. In this method, antibody binding is assessed using a peroxidase-conjugated anti-IgG/o-phenylenedi-amine system. An automated two-step fluorescent enzyme immunoassay has been reported. In this assay, Tg is immobilized on magnetic beads, and anti-human IgG mouse monoclonal antibody is labeled with alkafine phosphatase 4-methyiumbelliferyl phosphate is used as the substrate. IRMA and ELISA both have similar detection limits (approximately 3 to 5 U/mL). A considerably more sensitive radioassay has been reported in which diluted serum is incubated with T-labeled Tg to allow formation of antigen-antibody complexes these complexes are then precipitated by adding solid-phase protein A. Its detection limit is reported to be approximately 0.2 U/mL. 

Matthews, 2000). A phosphate salt solution and an aqueous suspension of HAp powder were used as an electrolyte for PEO and EPD, respectively. The corrosion resistance was assessed by potentiodynamic polarisation tests in a buffered physiological solution (see also Kwok et al., 2009). The results of this study indicated that a hybrid combination of PEO and EPD produces an osseoconductive phase-pure ITAp layer and an anticorrosive titania interlayer that promise to provide good mechanical and biochemical stability in the highly corrosive environment of the human body. Other studies involving titania bond coats include Albayrak and Altintas, 2010 Paluszkiewicz, Dlugon andKwiatek, 2012 Rath etal., 2012 and Jain etal. (2013). 

In this chapter common methods to evaluate chemical properties and phase composition of bioceramic coatings will be briefly described that are available in many laboratories including X-ray diffraction (XRD), vibrational spectroscopy techniques such as infrared (FTIR) and Raman spectroscopy and nuclear magnetic resonance spectroscopy (NMR). These methods provide a host of information on bulk phase composition, degree of crystallinity and crystallite size. Some special techniques including cathodoluminescence serve to reveal intrinsic coating properties that cannot be assessed by conventional analytical techniques, for example to distinguish between amorphous calcium phosphate (ACP) and crystalline calcium phosphates. 

Burke EM, Human JD, Weimer JJ, Cheney AB, Rigsbee JM, Lucas LC (2001) Influence of coating strain on calcium phosphate thin-lllm dissolution. J Biomed Mater Res 57 41-47 Burr DB, Mori S, Boyd RD, Sun TC, Blaha JD, Lane L, Parr J (1993) Histomorphometric assessment of the mechanisms for rapid ingrowth of bone to HA/TCP coated implants. J Biomed Mater Res 27 ... 

The cathode of new car batteries is manufactured with carbon-coated lithium iron phosphate (C-LiFeP04). The target lifetime of the battery is 10 yr. An accelerated test was developed to assess manufacturing steps in which one month is equivalent to 1 yr. If the standard deviation of the catalyst life in the accelerated test is 1.4 month, what is the probability that the battery will last longer than 8 yr ... 

These organophosphates were used to coat both precipitated and ground calcium carbonates, and the coated fillers were assessed in SBR and EPDM elastomers. Coating was by adding an aqueous or organic solution of the phosphate modifier to an aqueous... 

Antibody membrane electrodes were characterized using cyclic voltammetry (CV), chronoamperometry (CA) and ELISA protocols. The electrolyte solution used for the CV consisted of 0.1 M phosphate buffer saline (PBS) at pH 7.4, 0.1 M NaCl and 0.1 M NaHC03. The ELISA test was conducted to assess the bioactivity of the antibody protein incorporated into the polymers. This was performed directly on the polymers deposited on platinum strips, which were coated on polyester and prepared as described above. A section of the polymer was removed from the bulk using a hole puncher and was placed in the bottom of microtitre plates for ELISA analysis. The plates were read at 405 nm every 10-minute interval. 

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