Adsorption of bovine serum albumin on poorly crystalline apatite: influence of maturation (original) (raw)
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Adsorption and structural properties of hydroxy- and new lacunar apatites
Journal of Molecular Structure
Design of novel phosphorus apatites, K 2 Pb 6 Zn 2 (PO 4) 6 and K 2 Pb 4 Ca 4 (PO 4) 6 , zinc hydroxyapatite Ca 8 Zn 2 (PO 4) 6 (OH) 2 , as well as hydroxyapatite Ca 10 (PO 4) 6 (OH) 2 , and its corresponding calcined powder were conducted by means of two different synthesis protocols, i.e. solid state and wet chemical methods. The prepared materials adopt P6 3 /m (No 176) as a space group. Structural refinements for K 2 Pb 6 Zn 2 (PO 4) 6 and K 2 Pb 4 Ca 4 (PO 4) 6 lacunar apatites, and that for the calcined hydroxyapatite, were performed using Rietveld method. For K 2 Pb 6 Zn 2 (PO 4) 6 , the refinement results showed that the majority of Pb 2þ cations occupy (6h) sites. This study examines the impact of the synthesis conditions on the physico-chemical properties and on the surface reactivity of the prepared materials. The analysis of the interactions of the samples with respect to a protein model (Bovin Serum Albumin), evaluated under the same experimental conditions, revealed a fast-kinetic process for the precipitated samples, compared to the crystals obtained by solid chemical reaction. Thus, the equilibrium conditions were reached in less than 20 min for the former while 6 h of contact were requested for the latter. However, all the obtained isotherms show a Langmuirian shape. The difference in the adsorption parameters of the materials, i.e. constant affinity and amount adsorbed at saturation, is discussed in terms of surface characteristics, chemical composition, crystals size and specific surface area. It is concluded that the interaction with the Bovin Serum Albumin (BSA) molecules is highly sensitive to the microstructure of the crystals.
Key Engineering Materials, 2004
Revised simulated body fluid (rSBF) was modified by addition of bovine serum albumin (BSA) and glucose in physiological amounts. Precipitation experiments were carried out in sealed plastic containers. The influence of both components on precipitation and crystallization of calcium phosphates from supersaturated solution equal to 4 times the ionic concentration of rSBF was studied under physiological conditions (solution pH = 7.40 ± 0.05, temperature 37.0 ºC ± 0.2 °). The experimental results showed that BSA was co-precipitated with calcium phosphates, but it evidently hindered the crystallization of the precipitates. Glucose showed negligible influence on crystallization of calcium phosphates.
Adsorption of O-phospho-L-serine and L-serine onto poorly crystalline apatite
Journal of colloid and interface science, 2001
The adsorption of phosphoserine and serine was studied to determine the effect of amino acid functional groups on the surface reactivity of synthetic poorly crystalline apatite similar to bone mineral. The experimental results for phosphoserine and serine uptake agree respectively with the Langmuir and Freundlich models. Phosphoserine exhibits stronger adsorption capacity and a higher affinity constant for the surface crystals compared to serine molecules. The enhanced adsorption capacity noted for phosphoserine might be related ...
Adsorption and bioactivity studies of albumin onto hydroxyapatite surface
Colloids and Surfaces B-biointerfaces, 2011
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
Journal of Biomedical Materials Research, 2004
The biocompatibility of implant materials used for substitution of bone tissue depends on its ability to induce the deposition of a hydroxyapatite layer when in contact with body fluids. In previous work, some of the authors found that bovine serum albumin (BSA) promotes calcium phosphate deposition if preadsorbed on hydroxyapatite and retards precipitation if preadsorbed on titania. In the present study, we investigated the adsorption of BSA upon particles of titania and hydroxyapatite in order to understand the different role played by the protein on the mineralization of both biomaterials. The adsorption isotherms were determined and the structural changes induced by adsorption at different surface coverages were investigated by circular dichroism spectroscopy and differential scanning microcalorimetry. At low surface coverages, the adsorbed BSA molecules lost part of their ␣-helix content. However, at high surface coverages, corresponding to the plateau values of the adsorption isotherms, the BSA molecules did not undergo structural rearrangements upon adsorption. In the latter circumstances, the availability of BSA calcium binding sites, which should be responsible for inducing mineralization, depends on the electrostatic interactions between BSA and the sorbent surface. A possible explanation for the different mineralization behavior of hydroxyapatite and titania is advanced.
Apatite deposition on titanium surfaces — the role of albumin adsorption
Biomaterials, 1997
Titanium implant surfaces are known to spontaneously nucleate apatite layers when in contact with simulated body fluids. However, adsorption of proteins may influence the process of apatite layer formation. In this study the role of bovine serum albumin (BSA) adsorption in the process of apatite deposition on titanium substrates is investigated. Deposition of calcium phosphate was induced by immersing titanium substrates in a Hank's balanced salt solution (HBSS) for times ranging from 1 to 23 days. The resulting substrates were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), wettability measurements and electrochemical impedance determinations. All these methods indicate the presence of a calcium phosphate layer. The same procedure was repeated substituting HBSS with a solution of BSA in HBSS. Although SEM, EDS and electrochemical impedance spectra do not reveal the presence of an apatite layer, XPS analysis strongly indicates that the inhibition of apatite formation by BSA is only partial. The competition between BSA adsorption and apatite deposition seems to lead to a mixed film where the protein co-exists with calcium phosphate. Wettability studies suggest that this surface film is heterogeneous and porous, similar to the thicker films formed in albumin-free HBSS. 0 1997 Elsevier Science Limited. All rights reserved
Insight into biological apatite: Physiochemical properties and preparation approaches
2013
Biological apatite is an inorganic calcium phosphate salt in apatite form and nano size with a biological derivation. It is also the main inorganic component of biological hard tissues such as bones and teeth of vertebrates. Consequently, biological apatite has a wide application in dentistry and orthopedics by using as dental fillers and bone substitutes for bone reconstruction and regeneration. Given this, it is of great significance to obtain a comprehensive understanding of its physiochemical and biological properties. However, upon the previous studies, inconsistent and inadequate data of such basic properties as the morphology, crystal size, chemical compositions, and solubility of biological apatite were reported. This may be ascribed to the differences in the source of raw materials that biological apatite are made from, as well as the effect of the preparation approaches. Hence, this paper is to provide some insights rather than a thorough review of the physiochemical properties as well as the advantages and drawbacks of various preparation methods of biological apatite.
Journal of Materials Science: Materials in Medicine, 2014
Bisphosphonates (BPs) are well established as an important class of drugs for the treatment and prevention of several bone disorders including osteoporosis. This work investigated the interaction of two bisphosphonates, risedronate and tiludronate, with several apatitic supports, a well-crystallised hydroxyapatite (HA) and nanocrystalline apatites with varying maturation times, chemical composition and surface characteristics. The purpose was to fully understand the adsorption mechanism and desorption process, by the evaluation of the effect of several physicochemical parameters (temperature, pH and concentration of calcium and phosphate ions). Whatever the nature of the BP and the structure and composition of the apatite, the adsorption of such anti-resorptive agents can be well described as an ion exchange-reaction between phosphates species on the apatitic surface and BP molecules in solution. However, the parameters of adsorption can vary depending on the physicochemical conditions of the adsorption reaction. In addition, the structure and composition of the apatitic surface also influence the adsorption properties. Finally, BPs molecules are slowly released from apatitic supports, because most of the adsorbed molecules are irreversibly bound and not spontaneously released by dilution or simple washing. Moreover, similar to their adsorption, the release of bisphosphonates is strongly affected not only by the chemical properties of the molecule, but also by the chemical and structural characteristics of the apatitic substrates. The understanding of the adsorption and release processes provides fundamental tools for the development of drug delivery systems using apatite materials.