The study of surface transformation of pulsed laser deposited hydroxyapatite coatings

Abstract

Hydroxyapatite (HA) coatings generally exhibit very good biocompatibility owing to their compositional resemblance to the natural hard tissue and to bioactive properties that are directly related to surface transformations in physiological fluids. In this study, two types of porous HA coatings produced with pulsed laser deposition were tested with respect to their dissolution/reprecipitation in a semidynamic simulated physiological solution. Coatings with higher porosity produced with a 355-nm wavelength laser exhibited significant reprecipitation earlier than those produced with a 266-nm wavelength laser. The dissolution of the non-HA phases played a major role in the reprecipitation of HA-like material as indicated by X-ray diffraction (XRD). The coatings' Ca/P ratio became closer to the theoretical value of HA. The newly formed HA had imperfect crystal structure and/or small crystal size as suggested by XRD. The reprecipitation resulted in a very dense morphology as shown by scanning electron microscopy, suggesting a mechanically strong structure after reprecipitation. Despite undergoing dissolution and reprecipitation, the coatings showed sufficient stability in the solution, as XRD and energy-dispersive X-ray studies indicated no significant loss of the coatings. The stability of these HA coatings and their ability to cause reprecipitation of HA in the simulated physiological solution showed the potential of these coatings for clinical applications.

Electrodeposition of hydroxyapatite coating on CoNiCrMo substrate in dilute solution

“…The increase in the concentration of the hydroxyl ions results in an increase in the concentration of hydrogen phosphate ions and phosphate ions by reactions (8) and (9):…”

“…Porous HA coating on these metal substrates can be adopted as bone cements in reconstruction [2]. To date many essential techniques have been used in the preparation of HA coatings, such as plasma spraying [3,4], magnetron sputtering [5,6], laser ablation [7,8], sol-gel [9,10], biomimetic [11], and electrochemical deposition [12][13][14][15]. Compared to other coating techniques, electrodeposition is conducted in solution at mild temperature and can be applied to complex or porous structures with high efficiency, good flexibility and economy [16].…”

Behavior of mammalian cells on magnesium substituted bare and hydroxyapatite deposited (Ti,Mg)N coatings

“…This treatment may result in the formation of undesired phases like whitlockite [19]. HA could also be coated on to the implant surfaces by using different techniques such as pulsed laser ablation, sputter deposition, electrophoretic deposition, thermal and plasma spraying [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Amorphous structure or low crystallinity of deposited HA films remains to be the main issue on the production of HA coatings since it directly affects the biological performance.…”

Preparation of Novel Hydroxyapatite/Yttria‐Stabilized‐Zirconia Gradient Coatings by Magnetron Sputtering

“…The cells (in culture medium) were dispensed into 24-well plates (2 Â 10 4 cells per well). The original samples were incubated for different periods (6,12,24,48, and 72 h) at 37 8C under a humidified atmosphere (5% CO 2 ). Colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were performed to assess the cytotoxicity of the cells that had been treated as described above.…”

“…Compared with regular multicomponent coatings, FGCs can effectively reduce the discontinuity of the thermal-expansion coefficients between the materials, and minimize the residual stresses in the coatings. Then, the useful life of the coatings can be improved.So far, various techniques, such as plasma spraying, [7,8] magnetron sputtering, [9,10] laser ablation, [11,12] sol-gel, [13,14] electrolytic deposition [15][16][17] and biomimetic strategies, [18] have been employed to prepare HA coatings. Of these, radiofrequency (RF) magnetron sputtering has the advantages of high deposition rate, relatively low sputtering temperature, uniform coating and high binding strength.…”