Microcalorimetric Study of Protein Adsorption onto Calcium Hydroxyapatites

Abstract

To clarify the adsorption mechanism of proteins onto calcium hydroxyapatite (Hap), the present study measured adsorption (DeltaHads) and desorption (DeltaHdes) enthalpies of bovine serum albumin (BSA; isoelectric point (iep) 4.7, molecular mass (Ms) 67,200 Da, acidic protein), myoglobin (MGB; iep=7.0, Ms=17,800 Da, neutral protein), and lysozyme (LSZ; iep=11.1, Ms=14,600 Da, basic protein) onto Hap by a flow microcalorimeter (FMC). Five kinds of large platelike particles of CaHPO4.2H2O (DCPD) after hydrolyzing at room temperature with different concentrations of NaOH aqueous solution ([NaOH]) for 1 h were used. DCPD converted completely to Hap after treatment at [NaOH]>or=2%, and the crystallinity of Hap was increased with an increase in [NaOH] up to 10%. The amounts of protein adsorbed (Deltanads) and desorbed (Deltandes) were measured simultaneously by monitoring the protein concentration downstream from the FMC with a UV detector. The Deltanads values were also measured statically by a batch method in each system. The Deltanads values measured by the FMC and static measurements fairly agreed with each other. Results revealed that DeltaHBSAads was decreased with an increase in [NaOH]; in other words, DeltaHBSAads was decreased with the improvement of Hap's crystallinity, suggesting that the BSA adsorption readily proceeded onto Hap. This fact indicated a high affinity of Hap to protein. This affinity was further recognized by DeltaHBSAdes because its positive value was increased by increasing [NaOH]. These opposite tendencies in DeltaHBSAads and DeltaHBSAdes revealed that Hap possessed a high adsorption affinity to BSA (i.e., enthalpy facilitated protein adsorption but hindered its desorption). The fraction of BSA desorption was also decreased with an increase in [NaOH], confirming the high affinity of Hap to protein. Similar results were observed on the LSZ system, though the enthalpy values were smaller than those of BSA. In the case of neutral MGB, DeltaHBSAads also exhibited results similar to those of the BSA and LSZ systems. However, due to its weak adsorption by the van der Waals force, DeltaHBSAdes was small and almost zero at [NaOH]>or=2%. Hence, the fraction of MGB desorption was less dependent on [NaOH].

Kinetic study on the protein decomposition by photocatalytic Ti(IV)-doped calcium hydroxyapatite particles

“…This result can be explained by their low adsorption ability of LSZ onto the TiHap particles. As the authors disclosed in our previous literature that the adsorption of LSZ onto TiHap is endothermic process, 16) i.e., the adsorption of LSZ is driven by entropy change of LSZ with changing their conformation. Hence, the adsorption of LSZ is inhibited at low temperature condition.…”

Preparation and Characterization of Monosdispersed Metal Phosphate Particles and Characteristics of Protein Adsorption Onto Various Apatite Particles

“…In the past decade, the authors' group has been conducted fundamental studies on the adsorption of acidic bovine serum albumin (BSA), neutral myoglobin (MGB), and basic lysozyme (LSZ) onto various kinds of synthetic Hap particles. [34][35][36][37][38][39][40][41][42][43][44][45][46][47] In these studies, we investigated by changing many factors of Hap particles, such as calcium-to-phosphorus (Ca/P) atomic ratio, kinds of divalent cations (Ca, Sr and Ca-Sr solid solution), mean particle length, contents of carbonate ions incorporated and heat treatment temperature. The synthesis methods of various kinds of apatite particles as employed in the following sections were briefly described.…”

Molecular Docking Characterization of a Four-Domain Segment of Human Fibronectin Encompassing the RGD Loop with Hydroxyapatite

“…Numerous experimental methods have been developed to investigate the protein adsorption with HA, and researchers have studied the adsorption of proteins on the surface of biomaterials by the methods such as atomic force microscopy (AFM) [16], flow microcalorimetry (FMC) [17], solid state NMR [18], 2D electrophoresis [19], and steered molecular dynamics (SMD) simulations [20]. In this work, the interaction mechanism of FN-III [7][8][9][10] , which contains the RGD loop, with HAP molecules was investigated systematically by using a molecular docking strategy.…”