Mechanism of phosphate adsorption to a three-dimensional structure of boehmite in the presence of bovine serum albumin.
A new microcrystalline boehmite (tentatively named PT-A) was synthesized as an efficient phosphate adsorbent to replace aluminum hydroxide gel. The characteristic structure of PT-A was examined by nitrogen adsorption/desorption, X-ray diffraction, deviation microscopy, and scanning electron microscopy to establish a pore structural model of PT-A. With this model structure, the details of the mechanism of interaction between PT-A and phosphate in the presence of bovine serum albumin (BSA) are discussed. PT-A is a spherical particle with a diameter of approximately 100 microns and a porous surface structure, and its inside is packed with boehmite microcrystals (crystallite size, 2 nm). PT-A has three types of pores in its structure: a micropore with a narrow size-distribution, a mesopore with a broad size-distribution, and a macropore (radii of pores are 0.7, 1-20, and approximately 300 nm, respectively). When phosphate was incubated with PT-A in human gastric and intestinal juices or in an aqueous solution containing BSA, the amounts of phosphate adsorbed by PT-A were not affected by the presence of proteins. The nitrogen adsorption/desorption isotherms and energy dispersive X-ray analyses demonstrated that phosphate could diffuse to the smaller tunnels freely even if the external surface of PT-A was covered with BSA. It was also demonstrated that the main site of adsorption for phosphate was in micropores of PT-A, whereas BSA was adsorbed only to the external surface and none entered inside smaller tunnels consisting of micro- and mesopores.
Ookubo
A
A
Department of Chemical Science and Technology, Faculty of Engineering, University of Tokushima, Japan.
Nishida
M
M
Ooi
K
K
Ishida
K
K
Hashimura
Y
Y
Ikawa
A
A
Yoshimura
Y
Y
Kawada
J
J
D000327:Adsorption; D000536:Aluminum Hydroxide / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry*; D005750:Gastric Juice / Q000737:chemistry; D006801:Humans; D008024:Ligands; D008855:Microscopy, Electron, Scanning; D009584:Nitrogen / Q000737:chemistry; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry*; D016062:Porosity; D012710:Serum Albumin, Bovine; D013816:Thermodynamics; D014961:X-Ray Diffraction
D008024:Ligands; D010710:Phosphates; D012710:Serum Albumin, Bovine; D000536:Aluminum Hydroxide; C069471:aluminum oxide hydroxide; D000537:Aluminum Oxide; D009584:Nitrogen