Adsorption and bioactivity studies of albumin onto hydroxyapatite surface.
Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase.
Brazilian Center for Physics Research, Xavier Sigaud 150, 22290-180, RJ, Brazil. elenatude@gmail.com
Elena
E
Mavropoulos
Andréa M
AM
Costa
Lilian T
LT
Costa
Carlos A
CA
Achete
Alexandre
A
Mello
José M
JM
Granjeiro
Alexandre M
AM
Rossi
D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials / Q000378:metabolism*; D002021:Buffers; D002118:Calcium / Q000032:analysis; D002417:Cattle; D003198:Computer Simulation; D017886:Durapatite / Q000378:metabolism*; D006801:Humans; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D010758:Phosphorus / Q000032:analysis; D011208:Powders; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013054:Spectrophotometry, Atomic; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D002021:Buffers; D011208:Powders; D012710:Serum Albumin, Bovine; D010758:Phosphorus; D017886:Durapatite; D002118:Calcium