The roles of sub-micron and microscale roughness on shear-driven thrombosis on titanium alloy surfaces.

BACKGROUND: Continuous-flow ventricular assist devices (cfVADs) are implanted in patients with end-stage heart failure to assist with blood circulation. However, VAD implantation is associated with dangerous thrombotic complications. Our goal was to determine the impact of micron and sub-micron scale Ti6Al4V surface roughness on adherent platelet aggregate properties under clinically relevant shear rates. METHODS: We used fluorescence microscopy to visualize platelets in real time as they adhered to Ti6Al4V coupons of varying degrees of roughness, including a smooth control, in microfluidic channels and quantified deposition using an image processing algorithm. We systematically characterized roughness using spatial frequencies to generalize results for more blood-biomaterial contact applications. RESULTS: We observed that on the control and sub-micron rough surfaces, at 1000 s-1 , platelets adhered uniformly on the surface. At 2000 s-1 , we observed small and stably adherent platelet aggregates. At 5500 s-1 , platelet aggregates were large, unstable and interconnected via fibrillar structures. On a surface with micron-scale roughness features, at all three shear rates, platelets deposited in the troughs of the roughened surface, and formed aggregates. Thrombus height at 2000 s-1 and 5500 s-1 was greatest on the roughest surface and lowest on the mirror-finished surface, as indicated by the mean fluorescence intensity. CONCLUSIONS: These results demonstrated that at high shear rates, thrombi form regardless of surface topography at the scales applied. At lower shear rates, micron-scale surface features cause thrombus formation, whereas submicron features result in innocuous platelet adhesion. These findings have implications for manufacturing costs and other considerations.

Exploring the functionalization of Ti-6Al-4V alloy with the novel antimicrobial peptide JIChis-2 via plasma polymerization.

This study aimed to characterize the immobilization of the novel JIChis-2 peptide on the Ti-6Al-4V alloy, widely used in the biomedical sector. The antimicrobial activity of JIChis-2 was evaluated in the Gram-negative bacterium E. coli. Its immobilization occurred by inducing the formation of covalent bonds between the N-terminus of the peptides and the surface previously submitted to acrylic acid polymerization via the PECVD technique. Coated and uncoated surfaces were characterized by FTIR, AFM, SEM and EDX. Studies of global and localized corrosion were carried out, seeking to explore the effects triggered by surface treatment in an aggressive environment. Additionally, the ability of the functionalized material to prevent E. coli biofilm formation evidenced that the strategy to immobilize JIChis-2 in the Ti-6Al-4V alloy via PECVD of acrylic acid resulted in the development of a functional material with antibiofilm properties.

Design and 3D printing of novel titanium spine rods with lower flexural modulus and stiffness profile with optimised imaging compatibility.

PURPOSE: To manufacture and test 3D printed novel design titanium spine rods with lower flexural modulus and stiffness compared to standard solid titanium rods for use in metastatic spine tumour surgery (MSTS) and osteoporosis. METHODS: Novel design titanium spine rods were designed and 3D printed. Three-point bending test was performed to assess mechanical performance of rods, while a French bender was used to assess intraoperative rod contourability. Furthermore, 3D printed spine rods were tested for CT & MR imaging compatibility using phantom setup. RESULTS: Different spine rod designs generated includes shell, voronoi, gyroid, diamond, weaire-phelan, kelvin, and star. Tests showed 3D printed rods had lower flexural modulus with reduction ranging from 2 to 25% versus standard rod. Shell rods exhibited highest reduction in flexural modulus of 25% (~ 77.4 GPa) and star rod exhibited lowest reduction in flexural modulus of 2% (100.8GPa). 3D printed rod showed reduction in stiffness ranging from 40 to 59%. Shell rod displayed highest reduction in stiffness of 59% (179.9 N/mm) and gyroid had least reduction in stiffness of 40% (~ 259.2 N/mm). Rod bending test showed that except gyroid, other rod designs demonstrated lesser bending difficulty versus standard rod. All 3D printed rods demonstrated improved CT/MR imaging compatibility with reduced artefacts versus standard rod. CONCLUSION: By utilising novel design approach, we successfully generated a spine rod design portfolio with lower flexural modulus/stiffness profile and better CT/MR imaging compatibility for potential use in MSTS/other conditions such as osteoporosis. Thus, exploration of new rod designs in surgical application could enhance treatment outcome and improve quality of life for patients.

Influence of Tools and Cutting Strategy on Milling Conditions and Quality of Horizontal Thin-Wall Structures of Titanium Alloy Ti6Al4V.

Titanium and nickel alloys are used in the creation of components exposed to harsh and variable operating conditions. Such components include thin-walled structures with a variety of shapes created using milling. The driving factors behind the use of thin-walled components include the desire to reduce the weight of the structures and reduce the costs, which can sometimes be achieved by reducing the machining time. This situation necessitates, among other things, the use of new machining methods and/or better machining parameters. The available tools, geometrically designed for different strategies, allow working with similar and improved cutting parameters (increased cutting speeds or higher feed rates) without jeopardizing the necessary quality of finished products. This approach causes undesirable phenomena, such as the appearance of vibrations during machining, which adversely affect the surface quality including the surface roughness. A search is underway for cutting parameters that will minimize the vibration while meeting the quality requirements. Therefore, researching and evaluating the impact of cutting conditions are justified and common in scientific studies. In our work, we have focused on the quality characteristics of horizontal thin-walled structures from Ti6Al4V titanium alloys obtained in the milling process. Our experiments were conducted under controlled cutting conditions at a constant value of the material removal rate (2.03 cm3/min), while an increased value of the cut layer was used and tested for use in finishing machining. We used three different cutting tools, namely, one for general purpose machining, one for high-performance machining, and one for high-speed machining. Two strategies were adopted: adaptive face milling and adaptive cylindrical milling. The output quantities included the results of acceleration vibration amplitudes, and selected surface topography parameters of waviness (Wa and Wz) and roughness (Ra and Rz). The lowest values of the pertinent quantities were found for a sample machined with a high-performance tool using adaptive face milling. Surfaces typical of chatter vibrations were seen for all samples.

Graphene Coated Ti-6Al-4V Exhibits Antibacterial and Antifungal Properties Against Oral Pathogens.

PURPOSE: This study aimed to explore the antimicrobial properties of graphene coated Ti-6Al-4V to oral pathogens. MATERIALS AND METHODS: Graphene directly synthesized on Ti-6Al-4V alloy was characterized by scanning electron microscopy (SEM) and Raman spectroscopy. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, live/dead fluorescent staining and SEM were used to analyze the antimicrobial properties of graphene coated Ti-6Al-4V alloy to Porphyromonas gingivalis (P. gingivalis), Fusobacterium nucleatum (F. nucleatum), and Candida albicans (C. albicans). Reactive oxygen species (ROS) generation was monitored to reveal the antimicrobial mechanism. RESULTS: Graphene coated Ti-6Al-4V alloy caused a significant reduction in the presence of both bacterial and fungal pathogens as compared to uncoated Ti-6Al-4V alloy. P. gingivalis, F. nucleatum, and C. albicans on graphene coated Ti-6Al-4V alloy were less active than on uncoated Ti-6Al-4V alloy, and tended to become shrunk and deformed. Meanwhile, graphene coated Ti-6Al-4V alloy induced more generation of ROS in the pathogens than uncoated Ti-6Al-4V alloy. CONCLUSIONS: Graphene coated Ti-6Al-4V alloy exhibited antimicrobial properties against oral pathogens, the induction of oxidative stress might be involved in its antimicrobial mechanisms.

Preparation of chitosan-tannic acid coating and its anti-osteoclast and antibacterial activities in titanium implants.

INTRODUCTION: Bacterial infection and aseptic loosening caused by bone resorption at the implant interface are major clinical complications during bone defect implantation surgery, and surface modification of the implant to address the aforementioned problems has long been a research focus. MATERIALS AND METHODS: In this paper, a chitosan (CTS)-tannic acid (TA) colloid coating with a negative charge and excellent hydrophilicity was prepared on a Ti6Al4V (TC4) surface using a layer-by-layer assembly method. The physical properties, anti-osteoclast activity, and antimicrobial activity of the coatings were investigated. RESULTS: The findings showed that when the pH value was 5 and the ratio of CTS:TA was 0.8, the carrying rate of TA was the best. Furthermore, the CTS-TA coating had no cytotoxicity on the morphology and proliferation of BMSCs cells and effectively inhibited the differentiation of RAW264.7 cells into osteoclasts and the proliferation of Staphylococcus aureus and Escherichia coli. With the increase in the immersion time of TC4 in CTS-TA colloid solution, the inhibitory effects will also enhance. CONCLUSION: Therefore, the preparation of the CTS-TA coating provides a revolutionary technique for implant surface modification to avoid postoperative bacterial infection and aseptic loosening.

A novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold with enhanced osteoporotic osseointegration through osteoimmunomodulation.

BACKGROUND: Femoral stem of titanium alloy has been widely used for hip arthroplasty with considerable efficacy; however, the application of this implant in patients with osteoporosis is limited due to excessive bone resorption. Macrophages participate in the regulation of inflammatory response and have been a topic of increasing research interest in implant field. However, few study has explored the link between macrophage polarization and osteogenic-osteoclastic differentiation. The present study aims to develop a novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold with enhanced osteoporotic osseointegration through immunotherapy. METHOD: To improve the osteointegration under osteoporosis, we developed a hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold (PT). Biomimetic extracellular matrix (ECM) was constructed inside the interconnected pores of PT in micro-scale. And in nano-scale, a drug cargo icariin@Mg-MOF-74 (ICA@MOF) was wrapped in ECM-like structure that can control release of icariin and Mg2+. RESULTS: In this novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold, the macroporous structure provides mechanical support, the microporous structure facilitates cell adhesion and enhances biocompatibility, and the nanostructure plays a biological effect. We also demonstrate the formation of abundant new bone at peripheral and internal sites after intramedullary implantation of the biofunctionalized PT into the distal femur in osteoporotic rats. We further find that the controlled-release of icariin and Mg2+ from the biofunctionalized PT can significantly improve the polarization of M0 macrophages to M2-type by inhibiting notch1 signaling pathway and induce the secretion of anti-inflammatory cytokines; thus, it significantly ameliorates bone metabolism, which contributes to improving the osseointegration between the PT and osteoporotic bone. CONCLUSION: The therapeutic potential of hierarchical PT implants containing controlled release system are effective in geriatric orthopaedic osseointegration.

Surface chemistry in Ti-6Al-4V feedstock as influenced by powder reuse in electron beam additive manufacturing.

X-ray photoelectron spectroscopy (XPS) as well as scanning and transmission electron microscopy (SEM/TEM) analysis was carried out on four Ti-6Al-4V powders used in electron beam powder-bed fusion (PBF-EB) production environments: virgin low oxygen (0.080 wt% O), reused medium oxygen (0.140 wt% O), reused high oxygen (0.186 wt% O), and virgin high oxygen (0.180 wt% O). The two objectives of this comparative analyses were to (1) investigate high oxygen containing Grade 23 Ti-6Al-4V powders which were further oxidized as a function of reuse and (2) comparing the two virgin Grade 23 and Grade 5 powders of similar oxygen content. The microstructure of the low oxygen virgin Grade 23 powder was consistent with martensitic α' microstructure, whereas the reused powder displayed tempered α/ß Widmänstatten microstructure. XPS revealed a decrease in TiO2 at the surface of the reused powders with an increase in Al2O3. This trend is energetically favorable at the temperatures and pressures in PBF-EB machines, and it is consistent with the thermodynamics of Al2O3 vs. TiO2 reactions. An unexpected amount of nitrogen was measured on the titanium powder, with a general increase in nitride on the surface of the particles as a function of reuse in the Grade 23 powder.

Selective Laser Melted Titanium Alloy for Transgingival Components: Influence of Surface Condition on Fibroblast Cell Behavior.

PURPOSE: To mechanically characterize and assess the biological properties of Ti6Al4V surfaces obtained by Selective Laser Melting in order to determine whether this process is conceivable for production of implant-supported prostheses and particularly trans-gingival components. As-built and polished surfaces were studied in comparison with components obtained by computer numerical control machining technology in order to consider whether the properties are in the same range as the conventional method currently used. MATERIALS AND METHODS: Cylindrical specimens of Ti6Al4V (n = 6) were built with Selective Laser Melting for the characterization of mechanical properties according to ISO 22674 and discs (n = 12) were fabricated in the same conditions for cytotoxicity evaluation. Discs (n = 12) of Ti6Al4V were also obtained by computer numerical control machining as control. Half of the number of discs (n = 6) from each process were polished, to simulate the laboratory protocol for polishing of transmucosal components and half of the discs remained unaltered (as-built). Surface roughness measurements of disc specimens (as-built and polished) were compared with computer numerical control milling specimens (as-built and polished). Proliferation of human gingival fibroblasts on Ti6Al4V surfaces was also assessed for each condition. Viability and cell morphology were then evaluated qualitatively. Ra and Sa data were compared using Student's t-test (α = 0.05) and metabolic activity data were compared using Kruskal-Wallis statistical test (α = 0.05). RESULTS: Selective Laser Melting specimens showed elongation at break greater than 2% and 0.2% yield strength better than 500MPa which complied with ISO 22674 standards. Although Selective Laser Melting samples displayed significantly increased roughness on as-built surfaces compared to computer numerically controlled milling samples (p < 0.05), no statistically significant difference was observed after mechanical polishing (p = 0.279). Regarding metabolic activity, no statistical difference was observed between groups at day 3 (p > 0.05) and fibroblasts showed a viability higher than 97% on all discs. Cell shapes on polished samples suggested moderate adhesion compared to unpolished samples. CONCLUSION: With the manufacturing parameters selected in this study, Selective Laser Melting of Ti6Al4V appeared to be compatible with a prosthetic application type 4 according to ISO 22674. Surfaces obtained, followed by recommended postprocessing provided components with equivalent biological properties compared to computer numerical control machining technology.

Biotribocorrosion of 3D-Printed silica-coated Ti6Al4V for load-bearing implants.

Laser-based 3D Printing was utilized to deposit a silica (SiO2) coating on the surface of Ti6Al4V (Ti64) alloy for implementation onto articulating surfaces of load-bearing implants. The surface laser melting (SLM) technique was implemented in 1, and 2 laser passes (1LP and 2LP) after SiO2 deposition to understand the influence of remelting on the coating's hardness and tribological performance. It was observed that compositional and microstructural features increased the cross-sectional hardness. Wear rate was observed to decrease from 2.9×10-4 in the Ti64 to 5.2 ×10-6, 3.8×10-6, and 2.1×10-7 mm3/Nm for the as-processed or zero laser-pass (0LP), 1LP, and 2LP, respectively. Coated samples displayed a positive shift in open-circuit potential (OCP) during linear wear by displaying a 368, 85, and 613 mV increase compared to Ti64 for 0LP, 1LP, and 2LP, respectively. Our results showed promising tribological performance of SiO2 coated Ti6Al4V for articulating surfaces of load-bearing implants.

Mechanical properties of additively manufactured variable lattice structures of Ti6Al4V.

Engineered micro- and macro-structures via additive manufacturing (AM) or 3D-Printing can create structurally varying properties in part, which is difficult via traditional manufacturing methods. Herein we have utilized powder bed fusion-based selective laser melting (SLM) to fabricate variable lattice structures of Ti6Al4V with uniquely designed unit cell configurations to alter the mechanical performance. Five different configurations were designed based on two natural crystal structures - hexagonal closed packed (HCP) and body-centered cubic (BCC). Under compressive loading, as much as 74% difference was observed in compressive strength and 71% variation in elastic modulus, with all samples having porosities in a similar range of 53 to 65%, indicating the influence of macro-lattice designs alone on mechanical properties. Failure analysis of the fracture surfaces helped with the overall understanding of how configurational effects and unit cell design influence these samples' mechanical properties. Our work highlights the ability to leverage advanced manufacturing techniques to tailor the structural performance of multifunctional components.

Zirconia-Toughened Alumina Coated Ti6Al4V via Additive Manufacturing.

CoCr alloy-based femoral heads have failed prematurely due to galvanic-induced corrosion when coupled with a titanium hip stem. Coupling a titanium based-femoral head with the titanium hip stem is ideal in addressing this failure mode. Ti6Al4V (Ti64) alloy was reinforced with zirconia-toughened alumina (ZTA) by directed-energy deposition (DED)-based additive manufacturing (AM) to address that concern. Preliminary materials processing work resulted in failed samples due to cracking, porosity, and delamination. After careful parameter optimization, a Ti64+5wt.%ZTA (5ZTA) composition produced a metallurgically sound and coherent interface, minimal porosity, and bulk structures. Hardness was observed to increase by 27%, normalized wear rate reduced by 25%, and contact resistance increased during in vitro tribological testing along with faster surface re-passivation.

Heparin Enriched-WPI Coating on Ti6Al4V Increases Hydrophilicity and Improves Proliferation and Differentiation of Human Bone Marrow Stromal Cells.

Titanium alloy (Ti6Al4V) is one of the most prominent biomaterials for bone contact because of its ability to bear mechanical loading and resist corrosion. The success of Ti6Al4V implants depends on bone formation on the implant surface. Hence, implant coatings which promote adhesion, proliferation and differentiation of bone-forming cells are desirable. One coating strategy is by adsorption of biomacromolecules. In this study, Ti6Al4V substrates produced by additive manufacturing (AM) were coated with whey protein isolate (WPI) fibrils, obtained at pH 2, and heparin or tinzaparin (a low molecular weight heparin LMWH) in order to improve the proliferation and differentiation of bone-forming cells. WPI fibrils proved to be an excellent support for the growth of human bone marrow stromal cells (hBMSC). Indeed, WPI fibrils were resistant to sterilization and were stable during storage. This WPI-heparin-enriched coating, especially the LMWH, enhanced the differentiation of hBMSC by increasing tissue non-specific alkaline phosphatase (TNAP) activity. Finally, the coating increased the hydrophilicity of the material. The results confirmed that WPI fibrils are an excellent biomaterial which can be used for biomedical coatings, as they are easily modifiable and resistant to heat treatments. Indeed, the already known positive effect on osteogenic integration of WPI-only coated substrates has been further enhanced by a simple adsorption procedure.

Effect of Molybdenum (Mo) Addition on Phase Composition, Microstructure, and Mechanical Properties of Pre-Alloyed Ti6Al4V Using Spark Plasma Sintering Technique.

The effect of molybdenum additions on the phases, microstructures, and mechanical properties of pre-alloyed Ti6Al4V was studied through the spark plasma sintering technique. Ti6Al4V-xMo (where x = 0, 2, 4, 6 wt.% of Mo) alloys were developed, and the sintered compacts were characterized in terms of their phase composition, microstructure, and mechanical properties. The results show that the equiaxed primary alpha and Widmänstatten (alpha + beta) microstructure in pre-alloyed Ti6Al4V is transformed into a duplex and globular model with the increasing content of Mo from 0 to 6%. The changing pattern of the microstructure of the sample strongly influences the properties of the material. The solid solution hardening element such as Mo enhances mechanical properties such as yield strength, ultimate tensile strength, ductility, and hardness compared with the pre-alloyed Ti6Al4V alloy.

Rapid human-derived iPSC osteogenesis combined with three-dimensionally printed Ti6Al4V scaffolds for the repair of bone defects.

Human-induced pluripotent stem cells (iPSCs) are an alternative source of mesenchymal stem cells used for bone regeneration. However, the current osteogenically induced methods for iPSCs are slow and complex. We have used retinoic acid (RA) to induce osteogenic iPSCs within 10 days and assess whether a rapid differentiation could improve the osteogenic potential of the three-dimensionally printed Ti6Al4V (3DTi) scaffolds. First, the osteogenic differentiation of iPSCs was induced with RA, and the osteogenic potential of iPSCs was evaluated using standard assays. In addition, a 5-mm mandibular bone defect was generated in rats and was repaired with 3DTi scaffolds that were seeded with iPSC-induced osteoblasts. The capacity of seeded scaffolds for the enhancement of bone regeneration in vivo was assessed. Finally, we tested the potential mechanisms of RA-dependent iPSC bone induction and its effect on the Wnt/ß-catenin pathway. The results showed that iPSCs could form osteocytes within 10 days. Animal experiments confirmed that rapid osteo-induced iPSCs could enhance the bone regeneration and osteointegration capacity of the 3DTi scaffolds. Mechanistically, RA could activate the AKT/GSK3ß/ß-catenin pathway during the process of iPSCs osteogenesis. The rapid osteoinduction of iPSCs combined with 3DTi scaffolds is a safe, effective, and reproducible method for repairing mandibular bone defects.

Schwann Cell-derived exosomes promote bone regeneration and repair by enhancing the biological activity of porous Ti6Al4V scaffolds.

Implants made of porous titanium alloy and fabricated by 3D printing are increasingly used in clinical research. However, porous titanium alloys do not integrate very well with surrounding bone tissue, and bone ingrowth into the implants is not substantial. Schwann cells (SCs) and SC-derived exosomes can effectively promote nerve regeneration, but their role in bone tissue regeneration and repair has not been studied. Therefore, we added SC-derived exosomes to bone marrow stromal cell (BMSC) cultures and observed their effect on BMSCs in vitro; then, we combined exosomes with porous Ti6Al4V scaffolds and observed their effects on bone regeneration and repair in vivo. We found that SC-derived exosomes could promote the migration, proliferation and differentiation of BMSCs and that combining exosomes with porous titanium alloy can effectively improve the efficacy of titanium alloy scaffolds in bone repair. The combination of exosomes and porous Ti6Al4V implants may constitute a new therapeutic strategy for treating bone defects.

Phenolic-Enriched Collagen Fibrillar Coatings on Titanium Alloy to Promote Osteogenic Differentiation and Reduce Inflammation.

The adsorption of biomolecules on biomaterial surfaces can promote their integration with surrounding tissue without changing their bulk properties. For biomaterials in bone reconstruction, the promotion of osteogenic differentiation and reduction of inflammation are desirable. Fibrillar coatings are interesting because of fibrils' high surface area-volume ratio, aiding adsorption and adhesion. Fibrils also serve as a matrix for the immobilization of biomolecules with biological activity, such as the phenolic compound phloroglucinol (PG), the subunit of marine polyphenols. The aim of this work was to investigate the influence of PG coatings on fibroblast- and osteoblast-like cells to increase the osseointegration of titanium implants. Collagen fibril coatings, containing PG at low and high concentrations, were produced on titanium alloy (Ti6Al4V) scaffolds generated by additive manufacturing (AM). These coatings, especially PG-enriched coatings, reduced hydrophobicity and modulated the behavior of human osteosarcoma SaOS-2 and mouse embryonic fibroblast 3T3 cell lines. Both osteoblastic and fibroblastic cells spread and adhered well on PG-enriched coatings. Coatings significantly reduced the inflammatory response. Moreover, osteogenic differentiation was promoted by collagen coatings with a high PG concentration. Thus, the enrichment of collagen fibril coatings with PG is a promising strategy to improve Ti6Al4V implants for bone contact in orthopedics and dentistry and is worthy of further investigation.

In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring.

The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butterfly wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main differences in both the bioactivity in simulated body fluid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these differences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant fields.

Use of non-thermal plasma pre-treatment to enhance antibiotic action against mature Pseudomonas aeruginosa biofilms.

Non-thermal plasma (NTP), generated at atmospheric pressure by DC cometary discharge with a metallic grid, and antibiotics (gentamicin-GTM, ceftazidime-CFZ and polymyxin B-PMB), either alone or in combination, were used to eradicate the mature biofilm of Pseudomonas aeruginosa formed on Ti-6Al-4V alloy. Our aim was to find the conditions for NTP pre-treatment capable of enhancing the action of the antibiotics and thus reducing their effective concentrations. The NTP treatment increased the efficacy of relatively low concentrations of antibiotics. Generally, the highest effect was achieved with GTM, which was able to suppress the metabolic activity of pre-formed P. aeruginosa biofilms in the concentration range of 4-9 mg/L by up to 99%. In addition, an apparent decrease of biofilm-covered area was confirmed after combined NTP treatment and GTM action by SYTO®13 staining using fluorescence microscopy. Scanning electron microscopy confirmed a complete eradication of P. aeruginosa ATCC 15442 mature biofilm from Ti-6Al-4V alloy when using 0.25 h NTP treatment and subsequent treatment by 8.5 mg/L GTM. Therefore, NTP may be used as a suitable antibiofilm agent in combination with antibiotics for the treatment of biofilm-associated infections caused by this pathogen.

[The Local Alternative Ti-6Al-4V Alloy Coating of Surgery Steel Instruments for Laser Deposition Forming].

Aiming at the medical practice problems of the surgical steel medical instruments, such as the crevice corrosion, the poor mechanical compatibility and the Ni, Cr plasma exudation, the laser deposition of Ti-6Al-4V alloy cladding layer at the local functional area as alternative coating was proposed and realized as a new process method. The accurate element content and good formability Ti-6Al-4V cladding powder was chosen, the low power and high duty cycle optimized laser process was adopt, the alternative coating of good fusion and low dilution was prepared. Through the elemental line scanning, the interface microstructure analysis and the experiments of basic mechanical properties, the basic properties of the cladding were characterized and verified. The experiments results showed that, the Ti, Al and V contents of the top coating were respectively about 88%, 4.9% and 3.9%, no sensitizing ions such as Cr and Ni were detected. Initial equiaxed α phase, flake ß phase dist were distributed in the coating and interface, the α' martensite was precipitated at the boundary of the flake ß phase, some refined granular ß phase dispersion pinned to the grain boundary of basket structure. The microhardness of cladding layer was 352.08~312.76 HV0.1. The friction coefficient of the cladding layer was about 0.22~0.65. A new technology and method reference for improving and upgrading the performance of surgical medical devices is provided by this research.