Biocompatibility evaluation of dental metal alloys in vitro: expression of extracellular matrix molecules and its relationship to cell proliferation rates

The Evaluation of Osteoblastic Cell Behavior on Treated Titanium Surface

Background:

There are several potential advantages in optimizing the initial events of osseointegration in the benefit of clinical outcome.

Objective:

The objective of the present study was to evaluate the behavior of osteoblastic cells on surfaces treated by double acid etching using HNO3 and H2SO4.

Methods:

Commercially pure titanium (grade 4) discs measuring 6 mm in diameter and 2 mm in thickness were used. The discs were divided into two groups: machined group and double acid-etched discs (HNO3 and H2SO4). Surface characteristics were assessed using Scanning Electron Microscopy. Pre-osteoblastic MC3T3-E1 cells were used for cell culture on the tested surfaces to assess proliferation, viability (MTT), as well as secretion (ELISA) and cytoplasmic expression (Western blot) of type I collagen.

Results:

The data obtained were analyzed using t-test or two-way ANOVA followed by Bonferroni’s test at 95% significance. The titanium surfaces showed average roughness values for the machined and treated surfaces of 0.29 and 1.16, respectively (p<0.05). An increase in cell proliferation was observed, which was corroborated by the viability assay. Both type I collagen secretion and intracellular expression were higher on the double acid-etched surface compared to the machine surfaces (p<0.05).

Conclusion:

Implant surfaces treated by double acid etching positively affected the early events of the interaction between titanium and osteoblastic cells, suggesting optimization of osseintegration.

The Evaluation of Osteoblastic Cell Behavior on Treated Titanium Surface

Background:

There are several potential advantages in optimizing the initial events of osseointegration in the benefit of clinical outcome.

Objective:

The objective of the present study was to evaluate the behavior of osteoblastic cells on surfaces treated by double acid etching using HNO3 and H2SO4.

Methods:

Commercially pure titanium (grade 4) discs measuring 6 mm in diameter and 2 mm in thickness were used. The discs were divided into two groups: machined group and double acid-etched discs (HNO3 and H2SO4). Surface characteristics were assessed using Scanning Electron Microscopy. Pre-osteoblastic MC3T3-E1 cells were used for cell culture on the tested surfaces to assess proliferation, viability (MTT), as well as secretion (ELISA) and cytoplasmic expression (Western blot) of type I collagen.

Results:

The data obtained were analyzed using t-test or two-way ANOVA followed by Bonferroni’s test at 95% significance. The titanium surfaces showed average roughness values for the machined and treated surfaces of 0.29 and 1.16, respectively (p<0.05). An increase in cell proliferation was observed, which was corroborated by the viability assay. Both type I collagen secretion and intracellular expression were higher on the double acid-etched surface compared to the machine surfaces (p<0.05).

Conclusion:

Implant surfaces treated by double acid etching positively affected the early events of the interaction between titanium and osteoblastic cells, suggesting optimization of osseintegration.

Cytotoxicity of alloying elements and experimental titanium alloys by WST-1 and agar overlay tests

OBJECTIVE

This study was performed to evaluate the biocompatibility of nine types of pure metals using 36 experimental prosthetic titanium-based alloys containing 5, 10, 15, and 20wt% of each substituted metal.

METHODS

The cell viabilities for pure metals on Ti alloys that contain these elements were compared with that of commercially pure (CP) Ti using the WST-1 test and agar overlay test.

RESULTS

The ranking of pure metal cytotoxicity from most potent to least potent was: Co>Cu>In>Ag>Cr>Sn>Au>Pd>Pt>CP Ti. The cell viability ratios for pure Co, Cu, In, and Ag were 13.9±4.6%, 21.7±10.4%, 24.1±5.7%, and 24.8±6.0%, respectively, which were significantly lower than that for the control group (p<0.05). Pure Pd and Pt demonstrated good biocompatibility with cell viabilities of 93.8±9.6% and 97.2±7.1%, respectively. The Ti-5Pd alloy exhibited the highest cell viability (128.4±21.4%), which was greater than that of CP Ti. By alloying pure Co or Cu with Ti, the cell viabilities for the Ti-xCo and Ti-xCu alloys increased significantly up to 10wt% of the alloying element followed by a gradual decrease with a further increase in the concentration of the alloying element. Based on the agar overlay test, pure Ag, Co, Cr, Cu, and In were ranked as 'moderately cytotoxic', whereas all Ti alloys were ranked as 'noncytotoxic'.

SIGNIFICANCE

The cytotoxicity of pure Ag, Co, Cr, Cu, and In suggests a need for attention in alloy design. The cytotoxicity of alloying elements became more biocompatible when they were alloyed with titanium. However, the cytotoxicity of titanium alloys was observed when the concentration of the alloying element exceeded its respective allowable limit. The results obtained in this study can serve as a guide for the development of new Ti-based alloy systems.

Fe-Pd based ferromagnetic shape memory actuators for medical applications: Biocompatibility, effect of surface roughness and protein coatings

Ferromagnetic shape memory (FMSM) alloys constitute an exciting new class of smart materials that can yield magnetically switchable strains of several percent at constant temperatures and frequencies from quasi-static up to some kilohertz. In addition to their FMSM properties, these alloys can still be operated as conventional shape memory materials and also exhibit related superelasticity, which are both important features for use in medical devices. In this study, extensive in vitro assessments demonstrate for the first time that vapor-deposited single crystalline Fe(70)Pd(30) thin films and roughness graded polycrystalline splats of the same stoichiometry exhibit excellent biocompatibility and even bioactivity in contact with different cell types-a prerequisite for medical applications. The present study shows that fibroblast and epithelial cell lines, as well as primary osteoblast cells, proliferate well on Fe-Pd. The number of focal contacts, important for strong tissue bonding, can be improved with different binding agents from the extracellular matrix. However, even without coating, there is clear evidence that cells on Fe-Pd substrates behave similarly to control experiments. Additionally, cytotoxic effects of polycrystalline surfaces with various roughness profiles can be excluded, giving another tunable parameter for applying Fe-Pd magnetically switchable membranes in, e.g., stents and valves.

Relationship between radial diffusion of copper ions released from a metal disk and cytotoxic effects. Comparison with results obtained using extracts

The extended use of metallic biomaterials yields to increasing sources of metal ions within the human body and may result in inflammation of the surrounding tissues, cell damage, and cancer. The aim of this study was to investigate the relationship between the radial diffusion of metal ions released from a metal disk by the corrosion process and the toxic effect on a cell line that grew around it. Results obtained with the metal disks (direct contact) were compared with assays made with extracts obtained from the dissolution of a metallic sample ex situ and then added to the cell culture to elucidate the cause of apparent inconsistencies in previous reports. The change of copper concentration due to corrosion and transient diffusion of copper ions from the copper disks into the cell line was evaluated according to Fick's 2nd law. Surviving cells distribution was interpreted considering the radial and time-dependence of copper concentration. We concluded that the toxic effect on those cells close to metallic biomaterials may be underestimated when only the extract methodology is employed for cytotoxic tests or when during the experiments with disks the presence of concentration gradients and the non-homogeneous distribution of dead cells are disregarded.

Biocompatibility of platinum-metallized silicone rubber: in vivo and in vitro evaluation

Silicone rubber is commonly used for biomedical applications, including implanted cuff electrodes for both recording and stimulation of peripheral nerves. This study was undertaken to evaluate the consequences of a new platinum metallization method on the biocompatibility of silicone rubber cuff electrodes. This method was introduced in order to allow the manufacture of spiral nerve cuff electrodes with a large number of contacts. The metallization process, implying silicone coating with poly(methyl methacrylate) (PMMA), its activation by an excimer laser and subsequent electroless metal deposition, led to a new surface microtexture. The neutral red cytotoxicity assay procedure was first applied in vitro on BALB/c 3T3 fibroblasts in order to analyze the cellular response elicited by the studied material. An in vivo assay was then performed to investigate the tissue reaction after chronic subcutaneous implantation of the metallized material. Results demonstrate that silicone rubber biocompatibility is not altered by the new platinum metallization method.

Interactions of fibroblasts with soldered and laser-welded joints

Relatively little is known about the biocompatibility of the soldered or laser-welded joints of dental appliances. We investigated the reaction of human gingival fibroblasts cultured in vitro in direct contact with samples of soldered and laser-welded joints from orthodontic lingual arches. Contrast phase light microscopy was used to evaluate cell adhesion, morphology and proliferation after 6 and 24h and after 7 and 16 days. Scanning electron microscopy (SEM) was performed at 16 days. Our in vitro findings provide evidence that laser-welded orthodontic appliances have superior fibroblast biocompatibility.

Interaction of soft condensed materials with living cells: phenotype/transcriptome correlations for the hydrophobic effect

The assessment of biomaterial compatibility relies heavily on the analysis of macroscopic cellular responses to material interaction. However, new technologies have become available that permit a more profound understanding of the molecular basis of cell-biomaterial interaction. Here, both conventional phenotypic and contemporary transcriptomic (DNA microarray-based) analysis techniques were combined to examine the interaction of cells with a homologous series of copolymer films that subtly vary in terms of surface hydrophobicity. More specifically, we used differing combinations of N-isopropylacrylamide, which is presently used as an adaptive cell culture substrate, and the more hydrophobic, yet structurally similar, monomer N-tert-butylacrylamide. We show here that even discrete modifications with respect to the physiochemistry of soft amorphous materials can lead to significant impacts on the phenotype of interacting cells. Furthermore, we have elucidated putative links between phenotypic responses to cell-biomaterial interaction and global gene expression profile alterations. This case study indicates that high-throughput analysis of gene expression not only can greatly refine our knowledge of cell-biomaterial interaction, but also can yield novel biomarkers for potential use in biocompatibility assessment.