Interaction of a plasma-sprayed hydroxyapatite coating in
contact with human osteoblasts and culture medium
Be ´ atrice Labat,
1
Nathalie Demonet,
2
Aline Rattner,
1
Jean-Luc Aurelle,
3
Jean Rieu,
2
Jacques Frey,
1
Annette Chamson
1
1
Laboratoire de Biochimie, Faculte ´ de Me ´decine, 15 rue Ambroise Pare ´, 42023 St Etienne cedex 02, France
2
Laboratoire de Me ´canique des Biomate ´riaux, Ecole Nationale des Mines, 158 cours Fauriel, 42023
St Etienne cedex 02, France
3
SERF, BP 2334, 69152 De ´cines cedex, France
Received 3 March 1998; accepted 20 January 1999
Abstract: The loss of calcium from plasma-sprayed cal-
cium phosphate ceramics (CPCs) on bioinert metal substrate
(Ti-6Al-4V) immersed in cell culture medium with or with-
out human osteoblast culture was measured. The ceramics
were a CPC and a duplex system composed of a CPC layer
on an alumina coating. The dissolution of calcium com-
pounds was monitored by measuring the calcium leaked
from the coatings into the culture medium in 15 days. Cal-
cium was measured by flame photometry. The surfaces of
the ceramics exposed to the culture medium and in contact
with osteoblasts were analysed by X-ray diffraction (XRD).
The dissolution process occurred in the first 6 days of con-
tact, but the calcium released into the culture medium was
only a small fraction of the calcium content of the coatings.
The presence or absence of osteoblasts on the surface of the
ceramics did not make significant difference for the calcium
release. The XRD spectra of the ceramics before and after
immersion and in contact with cells did not show a signifi-
cant change in the compounds of the coatings. © 1999 John
Wiley & Sons, Inc. J Biomed Mater Res, 46, 331–336, 1999.
Key words: hydroxyapatite; calcium phosphate ceramics;
calcium dissolution; human osteoblasts; XRD
INTRODUCTION
Bioactive coatings have been developed to enhance
the integration of metal prostheses used in orthopedic
surgery and dentistry and to prolong the life of the
implant. The bone-bonding capacity of these coatings
has been improved to prevent the loosening of ce-
mentless prostheses. The bone-anchoring
1–10
capacity
and dissolution properties
11–18
of calcium phosphate
ceramics (CPCs), and particularly hydroxyapatite
(HA), are well documented. Dissolution properties of
CPCs depend upon their composition and structure.
Amorphous compounds dissolve faster than crystal-
line compounds.
13
Thus, as amorphous phases are dis-
solved first, they are believed to be one of the factors
of the initial biological response at the surface of the
ceramic.
19
Some authors link the dissolution to protein
anchoring prior to cell attachment.
20–22
It was recently
suggested that another type of composite coating
should be used to overcome the problem of degrada-
tion causing thinning of the coating with time. The
proposed composite was a calcium phosphate coating
on top of alumina.
23,24
This study was therefore carried out to examine the
dissolution of plasma-sprayed CPCs immersed in cul-
ture medium and the effect of contact with human
osteoblasts. Dissolution was monitored by measuring
the rate of calcium leakage and X-ray diffraction
(XRD) analysis of the surface of the ceramic.
MATERIALS AND METHODS
Biomaterials
The ceramics were plasma-sprayed onto titanium alloy
(Ti-6Al-4V) (Serf, De ´cines 69152, France) by the technique
used to prepare hip prostheses. The supports were 52-mm-
and 90-mm-diameter disks, and they were given three types
of coating: porous alumina (Al
2
O
3
) (negative control), po-
rous CPC mainly composed of three types of calcium phos-
phate [hydroxyapatite Ca
10
(PO
4
)
6
(OH)
2
, - and -TCP
Ca
3
(PO
4
)
2
], and CPC-coated porous alumina ceramic (CPC/
Correspondence to: J. Frey
Contract grant sponsor: Po ˆle Rho ˆ ne-Alpes de GBM
© 1999 John Wiley & Sons, Inc. CCC 0021-9304/99/030331-06