Adhesion of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa onto nanohydroxyapatite as a bone regeneration material L. Grenho, 1,2 M. C. Manso, 3,4 F. J. Monteiro, 1,2 M. P. Ferraz 1,5 1 INEB, Instituto de Engenharia Biom edica, Universidade do Porto, Rua Campo Alegre, 823, 4150-180 Porto, Portugal 2 Universidade do Porto, Faculdade de Engenharia (FEUP), Departamento de Engenharia Metal  urgica e Materiais, Rua Dr Roberto Frias, s/n, 4200-465 Porto, Portugal 3 Faculdade de Cie ˆ ncias da Sa ude, Universidade Fernando Pessoa, Prac ¸a 9 de Abril 349, 4249-004 Porto, Portugal 4 REQUIMTE, Universidade do Porto, Portugal 5 CEBIMED, Centro de Estudos em Biomedicina, Universidade Fernando Pessoa, Prac ¸a 9 de Abril 349, 4249-004 Porto, Portugal Received 19 October 2011; revised 6 February 2012; accepted 7 February 2012 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.34139 Abstract: In orthopedics due to the enormous number of sur- gical procedures involving invasive implant biomaterials, infections have a huge impact in terms of morbidity, mortal- ity, and medical costs. In this study the initial adhesion of several strains namely Staphylococcus aureus, Staphylococ- cus epidermidis, and Pseudomonas aeruginosa, to nanohy- droxyapatite, previously heat-treated at 725  C and 1000  C was assessed. Adherent cells were evaluated by scanning electron microscopy and quantified by confocal laser scan- ning microscopy and as colony forming units after being released by sonication. The wettability and roughness of samples surfaces were assessed by contact angle measure- ments and atomic force microscopy, respectively. Nanohy- droxyapatite heat-treated at 1000  C appeared to be more resistant to bacterial adhesion, over time, in five of the six tested strains while the clinical strains isolated from orthope- dic infections presented superior ability to adhere, as well as better capacity to produce slime. The increase in materials sintering temperature resulted in increased hydrophobicity and roughness; however, other surface features such as the decrease in surface area and on porosity as well as the decrease on zeta potential may be the aspects that contrib- uted to a lower bacterial adhesion on the materials sintered at 1000  C. V C 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A: 000–000, 2012. Key Words: bone infection, biomaterials, nanohydroxyapa- tite, bacterial adhesion How to cite this article: Grenho L, Manso MC, Monteiro FJ, Ferraz MP. 2012. Adhesion of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa onto nanohydroxyapatite as a bone regeneration material. J Biomed Mater Res Part A 2012:00A:000–000. INTRODUCTION Bone tissue infections, namely osteomyelitis, osteitis, spon- dylodiscitis, septic arthritis, and prosthetic joint infections, still represent the worst complications in orthopedic sur- gery and traumatology. These infectious processes are rela- tively frequent either when caused by direct infection from adjacent soft tissues, haemathogenous route or by surgical manipulation for biomaterials implantation. 1 From orthopedic prostheses to ventricular shunts, mod- ern medical procedures increasingly rely on indwelling devi- ces, many of which reside within the body for extended time periods. Unfortunately, infections associated with in- dwelling medical devices remain a significant clinical chal- lenge. For example, the number of catheter-related blood- stream infections yearly in the US has been estimated at >500,000. Such infections have a mortality rate of up to 25%; treatment costs alone approach roughly $28,000 per case. Altogether, infections associated with indwelling devi- ces account for nearly half of the two million nosocomial infections that occur in the US each year. 2 On the basis of updated epidemiological data concerning exclusively infections associated to prosthetic implants (including: artificial knees, hips, tendons and ligaments, fixa- tion systems, and so on), about 16% of the infections are of polymicrobial origin. A very large proportion of all implant- related infections are caused by staphylococci (roughly four out of five), and two single staphylococcal species, respec- tively Staphylococcus aureus and Staphylococcus epidermidis, account together for two out of three infection isolates. They represent, in absolute, the main causative agents in Correspondence to: L. Grenho; e-mail: liliana.grenho@ineb.up.pt Contract grant sponsor: Portuguese Foundation for Science and Technology (FCT); contract grant number: SFRH/BD/72866/2010 Contract grant sponsor: NanoforBone; contract grant number: NORTE-01-0202-FEDER-005372 Contract grant sponsor: NaNOBiofilm; contract grant number: PTDC/SAU-BMA/111233/2009 V C 2012 WILEY PERIODICALS, INC. 1