* Corresponding author. Tel.: #44-115-970-9424; fax: #44-115- 970-9732. E-mail address: colin.scotchford@nottingham.ac.uk (C.A. Scotchford). Biomaterials 22 (2001) 337}347 Osteoblast growth on titanium foils coated with hydroxyapatite by pulsed laser ablation M.D. Ball, S. Downes, C.A. Scotchford*, E.N. Antonov, V.N. Bagratashvili, V.K. Popov, W.-J. Lo, D.M. Grant, S.M. Howdle Biomaterials Group, School of Biomedical Sciences, Queens+ Medical Centre, University of Nottingham, Clifton Boulevard, Nottingham NG7 2UH, UK Institute of Laser and Information Technologies, Russian Academy of Sciences, 2 Pionersky, Troitsk, Moscow Region 142190, Russia Biomaterials Group, School of Mechanical, Materials and Manufacturing Engineering and Management, Nottingham, UK School of Chemistry, University of Nottingham, Nottingham, UK Received 20 October 1999; accepted 10 May 2000 Abstract Pulsed laser ablation is a new method for deposition of thin layers of hydroxyapatite (HA) on to biomaterial surfaces. In this paper, we report activity and morphology of osteoblasts grown on HA surfaces fabricated using di!erent laser conditions. Two sets of "lms were deposited from dense HA targets, at three di!erent laser #uences: 3, 6 and 9 J cm. One set of the surfaces was annealed at 5753C to increase the crystallinity of the deposited "lms. Primary human osteoblasts were seeded onto the material surfaces and cytoskeletal actin organisation was examined using confocal laser scanning microscopy. The annealed surfaces supported greater cell attachment and more de"ned cytoskeletal actin organisation. Cell activity, measured using the alamar Blue assay, was also found to be signi"cantly higher on the annealed samples. In addition, our results show distinct trends that correlate with the laser #uence used for deposition. The cell activity increases with increasing #uence. This pattern was repeated for alkaline phosphatase production by the cells. Di!erences in cell spreading were apparent which were correlated with the #uence used to deposit the HA. The optimum surface for initial attachment and spreading of osteoblasts was one of the HA "lms deposited using 9 J cm laser #uence and subsequently annealed at 5753C  2001 Elsevier Science Ltd. All rights reserved. Keywords: Osteoblast; Hydroxyapatite; Laser deposition; Crystallinity 1. Introduction Biological responses to materials di!er, both in vitro and in vivo, the di!erences being in#uenced by the sur- face properties of the material used in the device [1]. In an attempt to improve the in vivo performance of metal surfaces, calcium phosphate ceramics have been used in a variety of clinical applications as coatings on metal prostheses, and as dense and porous bone "llers for orthopaedics, neurosurgery and dentistry [2]. The exact mechanisms by which calcium phosphate ceramics im- prove bone bonding are not clearly understood, although it is known that the bioactivity of ceramics is related to the dissolution rate and that the early cellular response is of primary importance [3]. Cell and tissue reactions at ceramic interfaces have been studied using cell cultures [4], organ culture [4,5] and in vivo [6]. The sequence and timing of events at the implant interface is critical in determining the extent of bone apposition [7]. Protein adsorption to calcium phosphate materials is known to be important in bone cell attachment [8], speci"c serum glycoproteins a!ect cell attachment and spreading on biomaterials [9], and adsorption of serum proteins is a!ected by surface free energy [10]. Thermal spraying techniques are currently used for the coating of metallic prosthesis, and involve heating a ceramic powder above its melting point to produce partial molten droplets, which are accelerated by a gas stream and projected onto the metal. On impact, the droplets #ow into thin lamellar particles adhering to the surface, overlapping and inter- locking as they solidify. Whilst these techniques are use- ful, there are major drawbacks such as low interfacial strength, poor packing density and expensive argon/ helium gas as a carrier [11]. 0142-9612/01/$ - see front matter  2001 Elsevier Science Ltd. All rights reserved. PII: S 0 1 4 2 - 9 6 1 2 ( 0 0 ) 0 0 1 8 9 - 7