Titanium Surface Chemical Composition Interferes in the Pseudomonas aeruginosa Biofilm Formation

Bacterial adhesion on three different surfaces: untreated Ti, plasma nitriding, and plasma carbonitriding Ti substrates were investigated. The samples were placed in bacterial cultures of Pseudomonas aeruginosa to assess biofilm formation. The correlation between the amount of bacteria attached to the surface after a lapse of time with nanotopography and physicochemical properties was performed. TiN showed the highest capacity to avoid bacterial adhesion, while presenting intermediate roughness and wettability. Although the surface of TiCN had the highest surface roughness and low contact angle (high wettability), bacterial adhesion was intermediate on this sample. Untreated Ti, even though presenting a smooth surface and low wettability, had the highest tendency to form biofilms.     

Effects of Er:YAG laser on bacteria associated with titanium surfaces and cellular response in vitro

This in vitro study examined (a) the anti-bacterial efficacy of a pulsed erbium-doped yttrium aluminum garnet (Er:YAG) laser applied to Streptococcus sanguinis or Porphyromonas gingivalis adhered to either polished or microstructured titanium implant surfaces, (b) the response of osteoblast-like cells and (c) adhesion of oral bacteria to titanium surfaces after laser irradiation. Thereto, (a) bacteria adhered to titanium disks were irradiated with a pulsed Er:YAG laser (λ?=?2,940 nm) at two different power settings: a lower mode (12.74 J/cm² calculated energy density) and a higher mode (63.69 J/cm²). (b) After laser irradiation with both settings of sterile titanium, disks were seeded with 10⁴ MG-63 cells/cm². Adhesion and proliferation were determined after 1, 4, and 24 h by fluorescence microscopy and scanning electron microscopy. (c) Bacterial adhesion was also studied on irradiated (test) and non-irradiated (control) surfaces. Adhered P. gingivalis were effectively killed, even at the lower laser setting, independent of the material’s surface. S. sanguinis cells adhered were effectively killed only at the higher setting of 63.69 J/cm². Laser irradiation of titanium surfaces had no significant effects on (b) adhesion or proliferation of osteoblast-like MG-63 cells or (c) adhesion of both oral bacterial species in comparison to untreated surfaces. An effective decontamination of polished and rough titanium implant surfaces with a Er:YAG laser could only be achieved with a fluence of 63.69 J/cm². Even though this setting may lead to certain surface alterations, no significant adverse effect on subsequent colonization and proliferation of MG-63 cells or increased bacterial adhesion was found in comparison to untreated control surfaces.     

Role of fibronectin in staphylococcal adhesion to metallic surfaces used as models of orthopaedic devices

Staphylococcal infection of various prosthetic and internal fixation devices is a major complication associated with orthopaedic surgery. This study investigated the role of the host protein fibronectin in promoting adhesion of Staphylococcus aureus and Staphylococcus epidermidis to metallic surfaces representing materials used for orthopaedic devices. Pure human fibronectin was adsorbed in vitro onto coverslips (0.8 × 0.8 cm) of stainless steel, pure titanium, or titanium-aluminum-niobium alloy. In vitro bacterial adhesion was promoted more strongly by the metallic surfaces coated with fibronectin than by albumin-coated controls for two strains of S. aureus and one strain of S. epidermidis. Furthermore, with the fibronectin-coated coverslips, bacterial adhesion to titanium alloy was significantly greater than adhesion to stainless steel. Adhesion of the three staphylococcal strains was promoted more strongly by coverslips explanted from the subcutaneous space of guinea pigs and tested under similar conditions than by albumin-coated controls. Incubation of either in vitro fibronectin-coated or explanted metallic coverslips with anti-fibronectin antibodies produced a significant decrease in staphylococcal adhesion. These results suggest that the presence of fibronectin on the surface of implanted metallic devices is an important determinant of colonization of orthopaedic biomaterials by staphylococi.     

Bacterial adherence to tantalum versus commonly used orthopedic metallic implant materials

OBJECTIVES: Evaluation of bacterial adhesion to pure tantalum and tantalum-coated stainless steel versus commercially pure titanium, titanium alloy (Ti-6Al-4V), and grit-blasted and polished stainless steel. DESIGN: Experimental in vitro cell culture study using Staphylococcus aureus and Staphylococcus epidermidis to evaluate qualitatively and quantitatively bacterial adherence to metallic implants. METHODS: A bacterial adhesion assay was performed by culturing S. aureus (ATCC 6538) and S. epidermidis (clinical isolate) for one hour with tantalum, tantalum-coated stainless steel, titanium, titanium alloy, grit-blasted and polished stainless steel metallic implant discs. Adhered living and dead bacteria were stained using a 2-color fluorescence assay. Adherence was then quantitatively evaluated by fluorescence microscopy and digital image processing. Qualitative adherence of the bacteria was analyzed with a scanning electron microscope. The quantitative data were related to the implant surface roughness (Pa-value) as measured by confocal laser scanning microscopy. RESULTS: Bacterial adherence of S. aureus varied significantly (p = 0.0035) with the type of metallic implant. Pure tantalum presented with significantly (p < 0.05) lower S. aureus adhesion compared to titanium alloy, polished stainless steel, and tantalum-coated stainless steel. Furthermore, pure tantalum had a lower, though not significantly, adhesion than commercially pure titanium and grit-blasted stainless steel. Additionally, there was a significantly higher S. aureus adherence to titanium alloy than to commercially pure titanium (p = 0.014). S. epidermidis adherence was not significantly different among the tested materials. There was no statistically significant correlation between bacterial adherence and surface roughness of the tested implants. CONCLUSIONS: Pure tantalum presents with a lower or similar S. aureus and S. epidermidis adhesion when compared with commonly used materials in orthopedic implants. CLINICAL IMPLICATION: Because bacterial adhesion is an important predisposing factor in the development of clinical implant infection, tantalum may offer benefits as an adjunct or alternative material compared with current materials commonly used for orthopedic implants.     

Surface roughness and bacterial adhesion on root dentin treated with diode laser and conventional desensitizing agents

The treatments for dentin hypersensitivity (DH) may change the surface roughness of the root dentin, which can lead to biofilm accumulation, increasing the risk of root caries. The aim was to compare the surface roughness of root dentin after different treatments of DH and the biofilm formation on those surfaces. After initial surface roughness (Sa) assessment, 50 bovine root fragments received the following treatments (n = 10): G 1—no treatment; G2—5% sodium fluoride varnish; G3—professional application of a desensitizing dentifrice; G4—toothbrushing with a desensitizing dentifrice; and G5—diode laser application (908 nm; 1.5 W, 20 s). The Sa was reevaluated after treatments. Afterward, all samples were incubated in a suspension of Streptococcus mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted using a stereoscope, and the results were expressed in CFU/mL. The one-way ANOVA and the Tukey’s tests compared the roughness data and the results obtained on the bacterial adhesion test (α = 5%). G2 (2.3 ± 1.67%) showed similar Sa variation than G1 (0.25 ± 0.41%) and G5 (5.69 ± 0.99%), but different from group G3 (9.05 ± 2.39%). Group 4 showed the highest Sa variation (30.02 ± 3.83%; p < 0.05). Bacterial adhesion was higher in G4 (2208 ± 211.9), suggesting that bacterial growth is greater on rougher surfaces. The diode laser and the conventional treatments for DH may change the surface roughness of the root dentin, but only brushing with desensitizing dentifrice induced a higher bacteria accumulation on root dentin surface.     

In vitro study on the hemocompatibility of plasma electrolytic oxidation coatings on titanium substrates

Passively levitated ventricular assist devices (VADs) are vulnerable to impeller-housing contact and could benefit from surface coatings that improve wear resistance. Such coatings can be manufactured by plasma electrolytic oxidation (PEO), but their suitability for blood-contact applications needs further investigation. We therefore compared blood–surface interactions of polished titanium grade 5 (Ti Gr 5), as a general VAD reference material, uncoated ground titanium grade 4 (Ti Gr 4) and two commercially available PEO coatings on Ti Gr 4. In n = 4 static platelet adhesion tests, material samples were incubated with platelet-rich plasma (PRP) and consecutively analyzed for adhesive platelets by immunofluorescence microscopy. Additionally, PRP supernatant of incubated material samples was analyzed for changes in antithrombin III and fibrinogen concentrations by turbodimetry and enzyme-linked immunosorbent assay, respectively. We could not find any significant differences between the materials in the analyzed hemocompatibility markers (P > .05). Thus, we conclude that PEO coatings might offer a similar hemocompatibility to that of polished Ti Gr 5 and uncoated Ti Gr 4. Nevertheless, future studies should investigate blood–surface interactions of PEO coatings under realistic VAD-related flow conditions to better evaluate their potential for VAD applications.     

Novel animal model for studying the molecular mechanisms of bacterial adhesion to bone-implanted metallic devices: Role of fibronectin in Staphylococcus aureus adhesion

Infection around metallic implants is a rare but severe complication of orthopaedic surgery. A novel animal model mimicking conditions of internal fixation devices was developed to evaluate the role of host proteins adsorbed on metallic devices in promoting adhesion and colonization of the material surfaces by Staphylococcus aureus. Small plates made of pure titanium were either fixed (three screws per plate) onto the iliac bones of guinea pigs or implanted into their subcutaneous space as controls. Five to 6 weeks after surgery, the plates and screws were removed from the previously killed animals, carefully rinsed in buffer, and tested in an in vitro assay of S. aureus adhesion to metallic surfaces. To evaluate the role of fibronectin in staphylococcal adhesion to explanted plates and screws, a mutant of S. aureus that is specifically defective in fibronectin adhesion due to decreased expression of the fibronectin adhesin was compared with its isogenic parental strain. A significant reduction in adhesion of the fibronectin adhesin-defective mutant compared with the parental strain occurred on both the subcutaneously implanted and bone-implanted metallic plates. The results of this specific biological assay suggest that fibronectin is present on bone-implanted metallic devices and promotes attachment of S. aureus to their surfaces. This novel experimental model should help to characterize several parameters of bacterial adhesion to metallic orthopaedic devices and to develop novel anti-adhesive strategies for preventing such infections.     

Lavage of contaminated surfaces: an in vitro evaluation of the effectiveness of different systems

INTRODUCTION: Lavage is an effective, additive therapeutic procedure with a broad application in surgery. In addition to irrigation with the conventional syringe, the pulsed jet lavage system is used. The effectiveness of bacterial reduction depends on, among other things, the irrigation pressure. Complications of high-irrigation pressure in bone and joint surgery are intramedullary seeding of bacteria, visible damage of the bone, or delayed healing of the fracture by lavage of the fracture zone. The purpose of this in vitro study was to evaluate the effectiveness of mechanical irrigation on several surfaces using different systems of irrigation. MATERIALS AND METHODS: Four different test surfaces (nonbiological surfaces: sterilized bone cement and titanium osteosynthesis plates; biological surfaces: gamma-irradiated bovine muscle and cancellous bone) were contaminated with a defined suspension of different bacterial species (Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa). The samples were irrigated with three different systems (conventional 50-ml plastic syringe, manual pump irrigator, jet lavage) in a standardized, randomized experimental setup. After irrigation of the sample the amount of residual bacteria (colony-forming units) was determined. RESULTS: An effective bacterial reduction was achieved with the use of irrigation regardless of the system that was used and surface that was cleaned. On average P. aeruginosa was reduced around log 1.907, E. faecalis around log 1.666 and S. aureus around log 1.506. On biological surfaces, a reduction around log 0.801 for muscle and around log 1.738 for bone samples was achieved independent of the system that was used for irrigation. For the titanium surface a reduction of log 1.652 compared with log 2.580 for the bone cement surface was demonstrated. Statistical analysis showed that mechanical lavage resulted in a significant reduction of all tested bacterial species on the surfaces. The best bacterial reduction was achieved with the manual pump irrigator (P = 0.06). The results demonstrate that the manual pump irrigator achieved significantly better bacterial reduction (P = 0.039) on "biological surfaces" (bone and muscle) compared with nonbiological surfaces (titanium and cement). CONCLUSION: The results show that irrigation is an effective technique for bacterial reduction on contaminated surfaces. A remarkable finding was the limited bacterial reduction of Staphylococcus aureus from gamma-sterilized muscle. The use of a continuous manual pump irrigator showed a greater reduction of bacteria contamination compared with the other means of irrigation investigated. In conclusion, the manual continuous irrigation system proved to be practical, economical and effective in reducing the bacterial load on various surfaces.     

Effects of Roughness, Fibronectin and Vitronectin on Attachment, Spreading, and Proliferation of Human Osteoblast-Like Cells (Saos-2) on Titanium Surfaces

The influence of surface roughness and the presence of adhesion molecules in the culture medium were studied regarding cell adhesion, shape, and proliferation of osteoblast-like cells grown on two types of titanium disk. Type I disks were acid etched and type II disks were sandblasted and acid etched. Surface roughness was determined by contact profilometry and scanning electron microscopy. Chemical composition and oxide thickness of the superficial titanium layer were established with energy dispersive X-ray spectrometry, electron spectroscopy for chemical analysis and auger electron spectroscopy. Titanium release in the culture medium was assessed by inductively coupled plasma-optical emission spectrometry. Osteoblast-like cells (Saos-2) were cultured on both types of titanium disks (1) in standard conditions (DMEM culture medium supplemented with fetal calf serum), (FCS), (2) with the culture medium alone (DMEM alone), (3) in the presence of fibronectin or vitronectin (DMEM supplemented with fibronectin or vitronectin). Cultures were also performed in the presence of monoclonal anti-integrin (β₁, α_v) to test the cell adhesion molecules involved in the cell binding to the titanium surface. We found that sandblasting does not modify the chemical surface composition and that titanium represents only 5–6% (in the atom percentage) of surface elements. Release of titanium in the culture medium was found to increase from 24 to 72 hours. In the absence of FCS, fibronectin, or vitronectin, cells appeared scanty and packed in clusters. On the contrary, cells cultured in the presence of FCS, fibronectin, or vitronectin were flattened with large and thin cytoplasmic expansions. The addition of anti β₁ or α_v integrin subunit monoclonal antibody in the culture medium decreased adhesion and spreading of cells, particularly in the presence of fibronectin. Cell proliferation was significantly higher on culture plastic than on both types of disks, but was increased on rough but not on smooth surfaces. These results indicate that a high surface roughness and presence of fibronectin or vitronectin are critical elements for adhesion, spreading, and proliferation of cells on titanium surfaces. Received: 14 November 1997 / Accepted: 1 November 1998     

Reduction of fretting corrosion of Ti-6Al-4V by various surface treatments

Titanium and titanium-6% aluminum-4% vanadium (Ti-6Al-4V) are known to be biocompatible and corrosion resistant. However, there have been numerous reports of elevated tissue levels of titanium due to passive dissolution, wear, or fretting corrosion of implants. Studies were undertaken to determine whether the fretting corrosion of Ti-6Al-4V could be reduced by surface treatment of one or both surfaces in a fretting situation. Three different surface treatments were studied: ion implantation, physical vapor deposition nitriding, and plasma ion nitriding. The specimens used were screws fretting against the countersinks of a two-hole plate. Fretting corrosion was assessed by weight loss, by chemical analysis of test solutions, and by scanning electron microscopy. Surface treatment of one component, the screws, resulted in reduction in the release of titanium to only 18–32% of that seen with the untreated controls. Weight loss of the untreated plates fretted against physical vapor deposition nitrided screws and plasma ion nitrided screws was reduced to 31 and 38% of the control, respectively. The weight loss of plasma nitrided screws was only 30% that of the control. Nitriding of both plates and screws resulted in a further decrease in plate weight loss and metal release. Plasma ion nitriding of both components had the most significant effect, with the weight loss and titanium release being only 11 and 2% of the control values, respectively.     

A New Approach for Decreasing Postoperative Peritoneal Adhesions: Preventing Peritoneal Trauma with Soybean Oil

Background: Covering peritoneal surfaces with soybean oil may decrease peritoneal adhesions by preventing peritoneal trauma. Method(s): Forty female albino Wistar rats were divided into four equal groups. In Group 1, soybean oil only (0.1 ml) was injected into the peritoneal cavity. In Group 2, an untreated adhesion model was generated. In Group 3, an adhesion model was generated, followed by covering the area with soybean oil (0.1 ml). In Group 4, the area was first covered with soybean oil (0.1 ml) followed by generation of an adhesion model. All rats were sacrificed on postoperative day 10, and adhesions were scored. Results: The mean macroscopic adhesion scores in Groups 1, 2, 3, and 4 were 0.0 ± 0.0, 2.90 ± 0.21, 1.90 ± 0.94, and 0.50 ± 0.71, respectively. The Group 4 score differed significantly from that of Group 2 (p <. 001), but was not different from that of Group 1 or 3 (p >. 05). Discussion: Soybean oil can effectively decrease adhesion formation if applied before peritoneal trauma.     

New quantitative image analysis of staphylococcal biofilms on the surfaces of nontranslucent metallic biomaterials

Background Implant-related infection after orthopedic surgery is difficult to cure. One of the causes of infection is the bacterial biofilm that forms around biomaterials used during surgery. Therefore, it is necessary to investigate bacterial biofilms extensively to resolve the problems of these postoperative infections. However, no established culture method or quantification system exists for bacterial biofilms grown on the surface of the metallic biomaterials used in orthopedics, which are nonradiolucent. The purpose of this study was to develop a quantitative method to evaluate the difference in resistance of stainless steel versus titanium to staphylococcal biofilms and the efficacy of antibiotics against biofilms. Methods The bacterial strains used in this study were three Staphylococcus aureus stains: strain Seattle 1945 and two clinical strains cultured from postoperative infections. Staphylococcal biofilms were formed on stainless steel washers (SUS304) and titanium washers (pure titanium). They were stained with crystal violet and were examined with a digital microscope to calculate the bacterial coverage rate (BCR) by NIH imaging. Results The BCR of S. aureus biofilms formed on stainless steel and titanium washers increased over time. At 24, 48, and 72 h after cultivation, the amount of biofilm on the surface of the stainless steel washers was significantly greater or tended to be greater than that on the titanium. Cefazolin was applied to the obtained biofilms of two clinically isolated S. aureus strains. Cefazolin did not eradicate the biofilms but significantly reduced the biofilm of one strain. Conclusion The newly developed quantitative method (static microtube culture and measurement system) was useful for assessing the amount of bacterial biofilms on the surface of nontranslucent biomaterial. We found that titanium may be more resistant to bacterial infection than stainless steel. To control implant-related severe infections, the biomaterials should be assessed from the viewpoint of their resistibility to bacterial adhesions and infections.     

Enhanced Cell Integration to Titanium Alloy by Surface Treatment with Microarc Oxidation: A Pilot Study

Microarc oxidation (MAO) is a surface treatment that provides nanoporous pits, and thick oxide layers, and incorporates calcium and phosphorus into the coating layer of titanium alloy. We presumed such modification on the surface of titanium alloy by MAO would improve the ability of cementless stems to osseointegrate. We therefore compared the in vitro ability of cells to adhere to MAOed titanium alloy to that of two different types of surface modifications: machined and grit-blasted. We performed energy-dispersive x-ray spectroscopy and scanned electron microscopy investigations to assess the structure and morphology of the surfaces. Biologic and morphologic responses to osteoblast cell lines (SaOS-2) were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase activity), and αvβ3 integrin. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the MAO group increased in comparison to those in the machined and grit-blasted groups. The osteoblast cell lines of the MAO group were also homogeneously spread on the surface, strongly adhered, and well differentiated when compared to the other groups. This method could be a reasonable option for treating the surfaces of titanium alloy for better osseointegration. Each author certifies that he has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. This work was performed at Seoul St. Mary’s Hospital and St. Mary’s Hospital, Seoul, Korea.     

Inorganic antimicrobial coating for titanium alloy and its effect on bacteria

Background  For orthopedic implants, infection is a serious problem. Therefore, we considered an implant with antimicrobial ability can prevent infection. We tried to coat a titanium alloy surface with Novaron, a commercially available inorganic antimicrobial. The purpose of this study was to analyze the differences among the surfaces of materials coated using different processing pressures of the working gas and analysis of the antimicrobial activity. Methods  One of the inorganic antimicrobials Novaron (grade VZ 600) was applied to titanium alloy (Ti6Al4V) plates. This antimicrobial has limited heat resistance, so we used cold spray technology to coat the titanium alloy with it. The principle of cold spray technology is spraying a powder in a high-velocity gas jet, accelerated by adiabatic expansion, against a substrate. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) were used to analyze the differences among the surfaces of materials coated using different processing pressures of the working gas. The Japanese Industrial Standard (JIS) method (JIS Z2801: 2000) was used to analyze the antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Antimicrobial activity was analyzed only for the sample coated at 3.0 MPa. Results  The SEM and EDS results indicated that when the pressure of the working gas was increased, the antimicrobial coated the titanium adequately. This material showed good effects against S. aureus and P. aeruginosa and some effect for K. pneumoniae. Conclusions  Antimicrobial implants represent a preventive method against infection. There is a possibility of using them not only for clean operations but also for operations with suspected bacterial contamination, such as fixation of slight compound fractures.     

MC3T3‐E1 Cells Behavior on Surfaces Bombarded by Argon Ions in Planar Cathode Discharge

To evaluate the effect of topography in nanoscale, titanium surfaces were bombarded by argon ions (a chemically inert gas), in an atmosphere of plasma. The effects of surface parameters on morphology, adhesion, proliferation, and MC3T3‐E1 preosteoblasts differentiation were analyzed. Nontreated (smooth) surfaces were used as a control. The levels of average roughness (Ra) observed in bombarded and smooth titanium surfaces were of 95 and 14 nm, respectively. The wettability increased on treated surfaces. The number of attached cells (30 and 60 min) was significantly higher on the bombarded surface. The cell proliferation after 3 and 7 days was also significantly higher on the ion‐bombarded surface. In addition, the ALP activity and expression of osteocalcin were higher in cells grown on the treated surface. The results showed that bombardment with argon ions increased the roughness and the wettability of the Ti surface, promoting a significant increase in the adhesion, proliferation, and differentiation of preosteoblasts.     

Vitamin E blended Uhmwpe may have the potential to reduce bacterial adhesive ability

Biomaterial‐associated infection (BAI), a clinical problem resulting in septic failure of joint replacement implants, is initiated by bacterial adhesion, often by Staphylococcus epidermidis. Ultra high molecular weight polyethylene (UHMWPE) is a material of choice for joint replacement; reducing the adhesion of S. epidermidis to the polymer could be a means to decrease infection. We examined the adhesion of two ATCC and one clinical strain of S. epidermidis to standard polyethylene (PE), vitamin E blended UHMWPE (VE‐PE), and oxidized UHMWPE (OX‐PE) after different incubation times: a significant (p < 0.01) decrease in the adhered staphylococci on VE‐PE and a significantly higher incidence of the dislodged biofilm bacteria on OX‐PE was observed compared with that registered on PE. With attenuated total reflectance (ATR)–FTIR spectroscopy before and after suspension in bacterial medium for 48 h, new absorptions were observed mainly in OX‐PE, indicating adsorption of protein‐like substances on the polymer surface. We hypothesized that the different hydrophilicity of the surfaces with different chemical characteristics influenced protein adsorption and bacterial adhesion. These results may have clinical implications concerning the prevention of septic loosening: the VE‐PE could have the potential to reduce S. epidermidis adhesive ability if the preliminary data observed in these selected strains is further confirmed, as diversity among clinical strains is well known. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1662–1667, 2011     

An in vitro evaluation of the responses of human osteoblast-like SaOs-2 cells to SLA titanium surfaces irradiated by erbium:yttrium–aluminum–garnet (Er:YAG) lasers

Erbium:yttrium–aluminum–garnet (Er:YAG) laser treatment is an effective option for the removal of bacterial plaques. Many studies have shown that Er:YAG lasers cannot re-establish the biocompatibility of titanium surfaces. The aim of this study was to evaluate the responses of the human osteoblast-like cell line, SaOs-2, to sand-blasted and acid-etched (SLA) titanium surface irradiation using different energy settings of an Er:YAG laser by examining cell viability and morphology. Forty SLA titanium disks were irradiated with an Er:YAG laser at a pulse energy of either 60 or 100 mJ with a pulse frequency of 10 Hz under water irrigation and placed in a 24-well plate. Human osteoblast-like SaOs-2 cells were seeded onto the disks in culture media. Cells were then kept in an incubator with 5 % carbon dioxide at 37 °C. Each experimental group was divided into two smaller groups to evaluate cell morphology by scanning electron microscope and cell viability using 3-4,5-dimethylthiazol 2,5-diphenyltetrazolium bromide test. In both the 60 and the 100 mJ experimental groups, spreading morphologies, with numerous cytoplasmic extensions, were observed prominently. Similarly, a majority of cells in the control group exhibited spreading morphologies with abundant cytoplasmic extensions. There were no significant differences among the laser and control groups. The highest cell viability rate was observed in the 100 mJ laser group. No significant differences were observed between the cell viability rates of the two experimental groups (p?=?1.00). In contrast, the control group was characterized by a significantly lower cell viability rate (p?<?0.001). Treatments with an Er:YAG laser at a pulse energy of either 60 or 100 mJ do not reduce the biocompatibility of SLA titanium surfaces. In fact, modifying SLA surfaces with Er:YAG lasers improved the biocompatibility of these surfaces.     

Role of surface roughness of titanium versus hydroxyapatite on human bone marrow cells response

This study was designed to assess human bone marrow cell response and particularly cell adhesion, proliferation, and differentiation, when cultured in vitro on titanium alloy and hydroxyapatite with different values of surface roughness. A further aim was to compare the cell response on the two materials, currently used in spinal surgery. Cell adhesion was determined after 0.5, 2, 4, and 18 hours of incubation; proliferation after 8, 11, 14, and 16 days of culture; and differentiation was evaluated with the expression of alkaline phosphatase activity after 8 and 16 days of culture. This study showed that bone marrow cells grew faster on titanium alloy than on hydroxyapatite, although fewer cells attached to titanium, compared to those attached to hydroxyapatite. No statistically significant difference was observed as the expression of alkaline phosphatase activity on hydroxyapatite and titanium alloy of the same roughness. Cell adhesion, proliferation, and differentiation are dependent on surface roughness of the biomaterial, and all three increased as the roughness of titanium alloy increased. Conclusively, surface roughness of titanium and hydroxyapatite significantly influences bone marrow cell response, and therefore these biomaterials should be used with rough outer surface, if a significant cell response on them is desired. These advantages of titanium and hydroxyapatite theoretically seem to be of particular importance in the following situations: long fusions, lumbosacral fusion, revision surgery with poor bone bank, neuropathic scoliosis associated with few bone graft reserves, and adult patients with severe osteoporosis.     

In vivo evaluation of ammonia plasma modified ePTFE grafts for small diameter blood vessels replacement. A preliminary report.

BACKGROUND: Today, saphenous veins are most frequently used to reconstruct occluded or diseased small diameter vessels (< or =6 mm in diameter). However, these veins are unavailable in 30-40% of patients. In such a situation, prosthetic grafts provide the only alternative. Since an endothelial cell (EC) lining, important for maintaining a haemostatic-thrombotic balance, does not develop onto the intima of implanted grafts in humans, these grafts occlude within a short period of time. The failure of vascular grafts is attributed to their characteristics which are nonconducive towards endothelial cell adhesion, spreading and growth. In order to examine whether the patency of vascular grafts can be improved by the surface modification of grafts' intima, small diameter grafts were modified by a novel ammonia plasma treatment to enhance their interactions with EC. METHODS: Through laparotomy, ammonia plasma treated ePTFE (4 mm in diameter) grafts (n=3) and control untreated grafts (n=6) were implanted into the distal infrarenal aorta of rabbits. At appropriate time, grafts and adherent tissue were removed, fixed, stained and embedded in Poly/Bed 812. Light microscopic examination of thin sections cut from the proximal and distal anastomatic and midportion segments of explanted grafts was carried out. RESULTS: In control group studies, all animals developed lower limb paraplegia within seven days of implantation. Light microscopic examination of explanted control grafts showed that control grafts were obstructed by thrombosis/intimal hyperplasia. However, ammonia plasma modified explanted grafts, after one month of transplantation, revealed an endothelial cell-like lining that covered the grafts' inner surfaces. Accordingly, these grafts remained patent in animals. CONCLUSIONS: The grafts' surfaces that are made conducive to EC adhesion and proliferation and host response may influence endothelial regeneration. It is hoped that the combination of angiogenic molecules (i.e. endothelial cell specific growth factors such as VEGF) with ammonia plasma modified grafts may provide further insight into the development of ideal small diameter prosthesis.