Immobilization hydroxyapatite

Pure Ti02 was recently reported to be active in the disinfection of water contaminated by spores of the type Fusarium solani [142], Bacillus anthracis [143], or Cryptosporidium parvum oocysts [144], or when supported as nanocomposites on zeolite H(i for E. coli deactivation [145], and it found applications in water treatment as a replacement for chlorine. Ag-Ti02 immobilized systems were used for inactivation of bacteria, coupling the visible light response of the system and the strong bactericidal effect of Ag [146]. Silver was deposited on hydroxyapatite to form nanocomposites with a high capacity for bacterial adsorption and inactivation [147], or used for airborne bacterial remediation in indoor air [148],... 

Ma L.Q. Factor influencing the effectiveness and stability of aqueous lead immobilization by hydroxyapatite. J Environ Qual 1996 25 1420-1429. 

Aryal, S., Bahadour, K.C.R., Bhattarai, J.R., Prabu, P. and Kim, H.Y. (2006) Immobilization of collagen on gold nanoparticles, preparation, characterization and hydroxyapatite growth, foumal of Materials Chemistry, 16, 4642-4648. 

In order to achieve the firm fixation of the artificial cornea to host tissues, composites of collagen-immobilized poly(vinyl alcohol) hydrogel with hydroxyapatite were synthesized by a hydroxyapatite particles kneading method. The preparation method, characterization, and the results of corneal cell adhesion and proliferation on the composite material were studied. PVA-COL-HAp composites were successfully synthesized. A micro-porous structure of the PVA-COL-HAp could be introduced by hydrochloric acid treatment and the porosity could be controlled by the pH of the hydrochloric acid solution, the treatment time, and the crystallinity of the HAp particles. Chick embryonic keratocyto-like cells were well attached and proliferated on the PVA-COL-HAp composites. This material showed potential for keratoprosthesis application. Further study such as a long-term animal study is now required [241]. 

Ability of a protein to bind in a bio-specific (selective) manner to a chosen immobilized ligand Ability of certain proteins to complex with zinc and copper Mechanism not fully understood. Involves ability of some proteins to bind to calcium and phosphate ions on the surface of hydroxyapatite crystals... 

Phosphates have also been used as either impermeable or permeable reactive barriers for containment or remediation of contaminated groundwater. Fuller et al. (2002) looked at the mechanisms of U(VI) immobilization by apatites with EXAFS. Matheson et al. (2001) examined mechanisms of U(VI) removal in apatite-based permeable reactive barriers. Gauglitz et al. (1992) conducted laboratory studies on the efficacy of hydroxyapatite to remove U and Th from brine solutions. The minerals saleeite (Mg(U02)2(P04)2-9H20) and metaatunite (Ca(U02)2(P04)2-6H20) were observed. The concept of using apatite as a backfill material around repositories was explored. Apatite barriers made of Apatite II have been successfully... 

Arey, J. S., Seaman, J. C. Bertsch, P. M. 1999. Immobilization of uranium in contaminated sediments by hydroxyapatite addition. Environmental Science Technology, 33, 337-342. 

Studies on the mechanisms of lead immobilization by hydroxyapatite. Environmental Science Technology, 36, 1625-1629. 

Xu, T. Schwartz, F. W. 1994. Lead immobilization by hydroxyapatite in aqueous solutions. Journal of Contaminant Hydrology, 15, 187-206. 

Adsorption This method is the simplest way to immobilize enzymes. Enzymes can be adsorbed physically on a surface-active adsorbent by contacting an aqueous solution of enzyme with an adsorbent. Commonly employed adsorbents are (Zaborsky, 1973) alumina, amon-exchange resins, calcium carbonate, carbon, cation-exchange resins, celluloses, clays, collagen, colloid-ion, conditioned metal, glass plates, diatomaceous earth, and hydroxyapatite. The advantages of adsorption techniques are as follows ... 

The use of hydroxyapatites as a catalyst support has the following advantages (1) well-defined monomeric active species can be immobilized on the surface based on multiple functionalities, for example, cation exchange ability, adsorption capacity and nonstoichiometry (2) their hydrophilic character allows smooth reactions under aqueous conditions and (3) due to their robust structure, no leaching of metals occurs. 

It is produced in recombinant CHO cells cultured in a medium free of animal-derived components. The BeneFix production process involves an ultrafiltration/diafiltration step, followed by four chromatographic steps ion exchange (Q resin), pseudo-affinity (Cellufine sulfate resin), hydroxyapatite, and affinity (immobilized Cu2+ ions). After these chromatographic steps, there are membrane processes (nanofiltration for viral clearance and diafiltration for solvent exchange), after which the purified protein is formulated (Edwards and Kirby, 1999). 

Enamel mineral has many large hydroxyapatite crystals, whereas bone has many small ones with numerous vacancies and substitutions. These differences increase the elasticity of bone compared with enamel and promote its interactions with the surrounding collagen. Recently, a tightly bound hydration shell that fills a porous collagen-apatite junction was discovered around normal bone crystals. The water-filled pores are normally immobile, but repeated stresses cause the water to leak out from between the mineral and collagen. The drying increases mineralization and crystal formation, which may explain the decreased elasticity of bones with age. 

Metal bioavailability is an important parameter in determining the effectiveness of metal-contaminated soils in remediation. Assessment of metal bioavailability varies from humans to plants to microbes, and as such, various methods have been developed for a specific purpose. In this section we provide an overview of various methods used to determine the effectiveness of P-induced Pb immobilization. Reduction of Pb bioavailability by PR was demonstrated by feeding-trial and plant-uptake studies (Laperche et al., 1996). Hydroxyapatite and PR effectively... 

Boisson, J., Ruttens, A., Mench, M., and Vangronsveld, J. (1999). Evaluation of hydroxyapatite as a metal immobilizing soil additive for the remediation of polluted soils, 1 Influence of hydroxyapatite on metal exchangeability in soil, plant growth and plant metal accumulation. Environ. Pollut. 104, 225-233. 

Arends J, Christoffersen J, Christoffersen MR, Eckert H, Fowler BO, Heughebaert JC, Nancollas GH, Yesinowski JP, Zawacki SJ (1987) A calcium hydroxylapatite precipitated from an aqueous-solution —an international multimethod analysis. J Cryst Growth 84 515-532 Arey JS, Seaman JC, Bertsch PM (1999) Immobilization of uranium in contaminated sediments by hydroxyapatite addition. Environ Sci Tech 33 337-342 Belousova EA, Griffin WL, O Reilly SY, Fisher NI. (2002) Apatite as an indicator mineral for mineral exploration Trace-element compositions and their relationship to host rock type. J Geochem Explor 76 45-69... 

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