Sputtered Hydroxyapatite Nanocoatings on Novel Titanium Alloys for Biomedical Applications

Titanium and titanium alloys have been extensively studied for many applications in the area of bone tissue engineering. It was believed that the excellent properties of titanium alloys, e.g. lightweight, excellent corrosion resistance, high mechanical strength and low elastic modulus compared to other metallic biomaterials such as stainless steels and Cr-Co alloys, would provide enhanced stability for load-bearing implants. However, they usually lack sufficient osseointegration for implant longevity, and their biocompatibility is also an important concern in these applications due to the potential adverse reactions of metallic ions with the surrounding tissues once these metallic ions are released from the implant surfaces. One approach for consideration to improve the healing process is the application of a hydroxyapatite nanocoating onto the surface of biomedical devices and implants. Hydroxyapatite, with its excellent biocompatibility, and similar chemistry and structure to the mineral component of bone, provides a bioactive surface for direct bone formation and apposition with adjacent hard tissues. The deposition of a SiO2 interlayer between the implant surface and the hydroxyapatite nanocoating is necessary to further improve the biocompatibility of metal implants, as SiO2 has its own excellent compatibility with living tissues, and high chemical inertness, which lead to enhanced osteointegrative and functional properties of the system as a whole. Therefore, SiO2 and hydroxyapatite nanocoatings were deposited onto titanium alloys using electron beam evaporation and magnetron sputtering techniques, respectively, with different process parameters to optimize the deposition conditions and so achieve desired properties. Surface characteristics are essential due to their role in enhancing osseointegration. Surface morphology and microstructure were observed using a scanning electron micro-scope (SEM) and elemental analysis was performed by the energy dispersive X-ray spectroscopy method (EDS). The crystal structure was examined using X-ray diffractometer (XRD) to identify the phase components, while nanocoating thickness was measured using profilometer. This chapter is divided into five major parts. First is an overview of bone and bone implants, including their structure and mechanical properties. The second part highlights the importance of nanocoatings for bone implants longevity. Various coatings and surface modification techniques of titanium and its alloys are also elucidated. The advantages and drawbacks of each technique are reviewed. The last part focuses on the study of sputtered hydroxyapatite and SiO2 nanocoatings on titanium. A thorough discussion of the results is presented

ATP level variations in heterotrophic bacteria during attachment on hydrophilic and hydrophobic surfaces

A survey of the extracellular ATP levels of 86 heterotrophic bacteria showed that gram-negative bacteria of the genera Sulfitobacter, Staleya, and Marinobacter secreted elevated amounts of extracellular ATP, ranging from 6.0 to 9.8 pM ATP/colony forming unit (cfu), and that gram-positive bacteria of the genera Kocuria and Planococcus secreted up to 4.1 pM ATP/cfu. Variations in the levels of extracellular and intracellular ATP-dependent luminescence were monitored in living cells of Sulfitobacter mediterraneus ATCC 700856T and Planococcus maritimus F 90 during 48 h of attachment on hydrophobic (poly[tert-butyl methacrylate], PtBMA) and hydrophilic (mica) surfaces. The bacteria responded to different polymeric surfaces by producing either intracellular or extracellular ATP. The level of intracellular ATP in S. mediterraneus ATCC 700856T attached to either surface was as high as 50–55 pM ATP/cfu, while in P. maritimus F 90 it was 120 and 250 pM ATP/cfu on PtBMA and mica, respectively. S. mediterraneus ATCC 700856T generated about 20 and 50 pM of extracellular ATP/cfu on PtBMA and mica, respectively, while the amount generated by P. maritimus F 90 was about the same for both surfaces, 6 pM ATP/cfu. The levels of extracellular ATP generated by S. mediterraneus during attachment on PtBMA and mica were two to five times higher than those detected during the initial screening. High-resolution atomic force microscopy imaging revealed a potentially interesting correlation between the porous cell-surface of certain (α- and γ-proteobacteria and their ability to secrete high amounts of ATP. [Int Microbiol 2006; 9(1):37-46

Applications of Synchrotron-Source IR Spectroscopy for the Investigation of Insect Wings

Synchrotron-source infrared (IR) spectroscopy offers an effective method to characterise the chemical composition across surfaces. The intense light source allows the detection of trace quantities of different chemical components with a superior signal-to-noise ratio, while the highly collimated light enables high-resolution spatial mapping of the chemical distribution. In this chapter, we introduce synchrotron-source IR spectroscopy, using the infrared microspectroscopy (IRM) beamline at the Australian Synchrotron as an example. We then discuss the use of synchrotron-source IR spectroscopy to analyse insect wings in terms of experimental setup and a summary of the results in two different modes of operation, transmission and attenuated total reflection (ATR). Insect wings possess unique anti-wetting, self-cleaning, anti-biofouling and bactericidal properties and provide inspiration for biomimetic surfaces on synthetic materials which possess similar properties, useful in a range of industries

Decontamination-induced modification of bioactivity in essential oil-based plasma polymer coatings

Plasma polymer coatings fabricated from Melaleuca alternifolia essential oil and its derivatives have been previously shown to reduce the extent of microbial adhesion on titanium, polymers, and other implantable materials used in dentistry. Previous studies have shown these coatings to maintain their performance under standard operating conditions; however, when used in e.g., a dental implant, these coatings may inadvertently become subject to in situ cleaning treatments, such as those using an atmospheric pressure plasma jet, a promising tool for the effective in situ removal of biofilms from tissues and implant surfaces. Here, we investigated the effect of such an exposure on the antimicrobial performance of the Melaleuca alternifolia polymer coating. It was found that direct exposure of the polymer coating surface to the jet for periods less than 60 s was sufficient to induce changes in its surface chemistry and topography, affecting its ability to retard subsequent microbial attachment. The exact effect of the jet exposure depended on the chemistry of the polymer coating, the length of plasma treatment, cell type, and incubation conditions. The change in the antimicrobial activity for polymer coatings fabricated at powers of 20–30 W was not statistically significant due to their limited baseline bioactivity. Interestingly, the bioactivity of polymer coatings fabricated at 10 and 15 W against Staphylococcus aureus cells was temporarily improved after the treatment, which could be attributed to the generation of loosely attached bioactive fragments on the treated surface, resulting in an increase in the dose of the bioactive agents being eluted by the surface. Attachment and proliferation of Pseudomonas aeruginosa cells and mixed cultures were less affected by changes in the bioactivity profile of the surface. The sensitivity of the cells to the change imparted by the jet treatment was also found to be dependent on their origin culture, with mature biofilm-derived P. aeruginosa bacterial cells showing a greater ability to colonize the surface when compared to its planktonic broth-grown counterpart. The presence of plasma-generated reactive oxygen and nitrogen species in the culture media was also found to enhance the bioactivity of polymer coatings fabricated at power levels of 10 and 15 W, due to a synergistic effect arising from simultaneous exposure of cells to reactive oxygen and nitrogen species (RONS) and eluted bioactive fragments. These results suggest that it is important to consider the possible implications of inadvertent changes in the properties and performance of plasma polymer coatings as a result of exposure to in situ decontamination, to both prevent suboptimal performance and to exploit possible synergies that may arise for some polymer coating-surface treatment combinations

Content of Metals in Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. from Water Bodies of Different Salinity

Металлы определяли в двух видах макрофитов – Phragmites australis Trin. ex Steud и Potamogeton pectinatus L., произрастающих в водоемах с разной соленостью, с помощью эмиссионного спектрометра с индуктивно-связанной плазмой. Анализ результатов методом главных компонент показал, что на валовое содержание металлов влияет вид макрофитов и условия окружающей среды, в частности химический состав воды. Оба вида макрофитов из пресноводного водохранилища Бугач отличались более высокими концентрациями железа, алюминия, никеля, ванадия и кобальта по сравнению с теми же видами макрофитов, собранными в солоноватоводных озерах. Однако для макрофитов из оз. Шира, отобранных в опресненной и солоноватоводной частях озера, расхождений в содержании данных металлов не выявлено. В ряде случаев пробы из одной точки, но собранные в разные годы имели существенные различия – это наблюдалось для растений тростника из солоноватоводной станции оз. Шира, и растений рдеста из оз. Шунет. Было установлено, что наиболее высокое валовое содержание большинства металлов характерно для P. pectinatusMetals were determined in two species of macrophytes Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. grown in lakes of different salinity, using emission spectrometer with inductively coupled plasma. Principal component analysis revealed that the total metal content is influenced by species of macrophytes and environmental conditions (in particular water chemistry). Both species of macrophytes from freshwater reservoir Bugach were characterized by higher concentrations of Fe, Al, Ni, V and Co in comparison with the same species from brackish lakes. However, there were no significant differences in content of these metals between samples of macrophytes taken in desalinated and saltwater parts of Shira Lake. In some cases, metal content of samples collected in different years at the same place were significantly different. It was observed for plants of Ph. australis collected in brackish station of Shira Lake, and plants of P. pectinatus from Lake Shunet. It was found that the highest total content of most metals is typical for P. pectinatu