High protein adsorptive capacity of amino acid‐functionalized hydroxyapatite

Abstract

Charged functional groups present on the surface of biomaterials play an important role to regulate the affinity and attachment of macromolecules, including proteins, on the surface of biomaterials. In this study, the protein adsorptive capacity of hydroxyapatite (HA) was regulated by introducing different amino acids during the precipitation of HA. After incubation of HA samples in 5000 μg/mL lysozyme solution at pH 7.4 for 24 h, unmodified HA adsorbed 0.886 mg/m(2) of lysozyme while amino acid-functionalized HA (AA-HA) particles demonstrated higher adsorption capacity ranging from 1.090 to 1.680 mg/m(2). Incorporation of amino acids with longer side chain lengths decreased the crystallinity and increased the negative value of the surface charge of HA particles. The specific surface areas were significantly increased in the presence of amino acids. Protein loading capacity onto AA-HA was further enhanced by regulating the pH of working solution whereby the protein adsorption rate increased with decreasing the pH, while reverse trend obtained in unmodified HA. The study demonstrated that the amount of adsorbed lysozyme onto AA-HA particles was correlated with the particles' surface charges.

Environmental pH-controlled loading and release of protein on mesoporous hydroxyapatite nanoparticles for bone tissue engineering

“…The results demonstrated that MHA had a greatly improving protein loading capacity, nearly double that of HA. A number of factors are important in determining the amount of protein adsorbed on surfaces [6,10,16,17,20]. A higher surface area generally corresponds to a higher amount of protein adsorption [10,16].…”

“…The adsorption behaviors of large biomolecules onto hydroxyapatite have been frequently studied [16,17,19,22]. To our knowledge, attention has been focused on the amount of adsorption for large biomolecules, while models of adsorption onto MHA have scarcely been mentioned in the previous papers.…”

“…Hydroxyapatite particles [HA, Ca 10 (PO 4 ) 6 (OH) 2 )] with various morphologies and surface properties have been investigated as protein delivery device due to their biocompatible, nontoxic, and noninflammatory properties [11,[14][15][16][17]. Protein loading on HA is carried out by surface physical adsorption.…”

The Effect of Different Solvents for Chitosan Solubilization on The Crystal Growth of in situ Prepared Hydroxyapatite

“…where β hkl is the full width at half maximum in radians, Ɵ is the diffraction angle for plane (hkl), K is the constant depending on crystal habit (chosen as 0.94) and λ is the wavelength of Cu Kα radiation (1.5406Å) [12].…”

“…Additionally, HA crystals carry two different protein binding sites on its surface, e.g. P and C sites that can bind to positively cationic groups such as NH 3 + or negatively charged anionic groups such as COO -, respectively [12].…”