RESUMEN
The in vitro cell behavior on Nitinol after different surface treatments was investigated. As references samples, commercially pure titanium (cpTi) and bioactive titanium were used. The surface treatments influenced the topography, surface energy, crystallographic structure, ion release, chemistry, and ability to form apatite layer from simulated body fluids. Regardless of the surface treatment, the bioactivity study showed that the kinetics of apatite film formation was similar for all tested samples. No clear indication of the surface characteristics influence on the ability for calcium-phosphate precipitation was evident. Cell activity studies showed that ground nickel titanium, spark oxidized and thermally oxidized (at 400 degrees C and below) had higher cellular activity and caused increased alkaline phosphatase (ALP) and osteocalcin (OC) expression which was comparable to control tissue culture plastic and titanium reference samples. Regardless of surface modifications, preimmersion of the samples in media for 72 h resulted in cell proliferation at the same level for all samples. Therefore, it can be concluded that preconditioning of samples alters surface properties and modulates the cell response regardless of the initial surface treatment and its properties. Moreover, a detrimental effect on cell response was observed after 7 and 14 days in culture for alkali treated samples. This was attributed to a high surface nickel concentration and a high nickel ion release rate from these surfaces.
Asunto(s)
Aleaciones/química , Huesos/citología , Níquel/química , Osteocalcina/química , Titanio/química , Fosfatasa Alcalina/química , Línea Celular Tumoral , Proliferación Celular , Supervivencia Celular , Cristalografía por Rayos X/métodos , Medios de Cultivo/química , Humanos , Técnicas In Vitro , Propiedades de Superficie , Temperatura , HumectabilidadRESUMEN
Ni-Ti alloy due to its unique mechanical properties, is used for many types of implants. Failure of these implants can be attributed to many different factors; however infections are a common problem. In this paper, the attachment of the bacteria, Staphylococcus aureus, to the Ni-Ti surface modified by a range of processes with and without of light activation (used to elicit antimicrobial properties of materials) was assessed and related to different surface characteristics. Before the light activation the number of bacterial colony forming units was the greatest for the samples thermally oxidised at 600°C. This sample and the spark oxidised samples showed the highest photocatalytic activity but only the thermally oxidised samples at 600°C showed a significant drop of S. aureus attachment. The findings in this study indicate that light activation and treating samples at 600°C is a promising method for Ni-Ti implant applications with inherent antimicrobial properties. Light activation was shown to be an effective way to trigger photocatalytic reactions on samples covered with relatively thick titanium dioxide via accumulation of photons in the surface and a possible increase in defects which may result in free oxygen. Moreover, light activation caused an increase in the total surface energy.
RESUMEN
This study reports the relationship between the biocompatibility and surface properties of experimental bone cements. The effect of hydroxyapatite (HA) or alpha-tri-calcium phosphate (alpha-TCP) incorporated into bone cements prepared with methyl methacrylate as base monomer and either methacrylic acid or diethyl amino ethyl methacrylate (DEAEMA) as comonomers was investigated. The in vitro biocompatibility of these composite cements was assessed in terms of the interaction of primary human osteoblasts grown on the materials over a period of 5 days and compared with a control surface. These results were related to the surface properties investigated through a number of techniques, namely Fourier transform infrared, contact angle measurements, X-ray photoelectron spectroscopy and energy dispersive analysis of X-rays. Complementary techniques of thermal analysis and ion chromatography were also performed. Biocompatibility results showed that the addition of alpha-TCP improves biocompatibility regardless of comonomer type. This is in contrast to HA-based cements where cell proliferation was significantly lower. Surface characterisations showed that structural integrity of the materials was maintained in the presence of the acid and base comonomers, and water contact angles were reduced particularly in DEAEMA containing materials. Furthermore, ion chromatography confirmed higher Ca2+ and PO4(3-) ion release by both types of ceramics, particularly for those containing DEAEMA. In conclusion, the incorporation of acidic and basic comonomers to either HA or alpha-TCP ceramics containing bone cements can have differential effects upon the attachment and proliferation of bone cells in vitro. Moreover, those cements consisting of alpha-TCP and containing DEAEMA comonomer indicated the most favourable biocompatibility.
Asunto(s)
Cementos para Huesos/química , Osteoblastos/citología , Materiales Biocompatibles , Fosfatos de Calcio , División Celular , Cerámica , Durapatita , Humanos , Metacrilatos , Microscopía Electrónica de Rastreo , Osteoblastos/ultraestructura , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Rayos XRESUMEN
Nickel titanium (NiTi) shape memory alloys have been investigated for several years with regard to biomedical applications. However, little is known about the influences of surface modifications on the biocompatibility of these alloys. The effects of a range of surface treatments were investigated. Cytotoxicity and cytocompatibility studies with both fibroblast and endothelial cells showed no differences in the biocompatibility of any of the NiTi surfaces. The cytotoxicity and cytocompatibility of all surfaces were favorable compared to the controls. The hemolysis caused by a range of NiTi surfaces was no different from that caused by polished 316L stainless steel or polished titanium surfaces. The spreading of platelets has been linked to the thrombogenicity of materials. Platelet studies here showed a significant increase in thrombogenicity on polished NiTi surfaces compared to 316L stainless steel and pure titanium surfaces. Heat treatment of NiTi was found to significantly reduce thrombogenicity, to the level of the control. The XPS results showed a significant decrease in the concentration of surface nickel with heat treatment and changes in the surface nickel itself from a metallic to an oxide state. This correlates with the observed reduction in thrombogenicity.