Nickel suppression in Ni-Ti alloys by plasma immersion ion implantation surface treatment: New materials for orthopaedic implantation

Conference Theme: Spinal Motion Segment: From Basic Science to Clinical Applicationpublished_or_final_versio

Suppression of nickel out-diffusion from porous nickel-titanium shape memory alloy by plasma immersion ion implantation

Summary form only given. Porous nickel titanium is a promising material for medical application not only because of its super elasticity and shape memory effect but also the porous structure which may enhance bone growth due to the increased surface area. It is thus especially suitable for bone tissue in-growth and fixation of biomedical implants. However, like its dense counterpart, Ni leaching from the materials causes health concern. Thus, in order to suppress Ni diffusion from the materials to body fluids and tissues in humans, a diffusion barrier or similar structure must be introduced. In this work, we produced this diffusion barrier layer by oxygen or nitrogen plasma immersion ion implantation (PIII). In vitro tests were conducted by immersing the plasma-treated NiTi into simulated body fluid (SBF) at 37plusmn0.5degC for 5 weeks and the resulting SBF was analyzed for Ni and Ti using inductively-coupled plasma mass spectrometry (ICMPS). Our results show that Ni leaching is significantly mitigated by both nitrogen and oxygen PIII.published_or_final_versio

Perception and use of complementary and alternative medicine for low back pain

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Danger- and pathogen-associated molecular patterns recognition by pattern-recognition receptors and ion channels of the transient receptor potential family triggers the inflammasome activation in immune cells and sensory neurons.

An increasing number of studies show that the activation of the innate immune system and inflammatory mechanisms play an important role in the pathogenesis of numerous diseases. The innate immune system is present in almost all multicellular organisms and its activation occurs in response to pathogens or tissue injury via pattern-recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Intracellular pathways, linking immune and inflammatory response to ion channel expression and function, have been recently identified. Among ion channels, the transient receptor potential (TRP) channels are a major family of non-selective cation-permeable channels that function as polymodal cellular sensors involved in many physiological and pathological processes.In this review, we summarize current knowledge of interactions between immune cells and PRRs and ion channels of TRP families with PAMPs and DAMPs to provide new insights into the pathogenesis of inflammatory diseases. TRP channels have been found to interfere with innate immunity via both nuclear factor-kB and procaspase-1 activation to generate the mature caspase-1 that cleaves pro-interleukin-1ß cytokine into the mature interleukin-1ß.Sensory neurons are also adapted to recognize dangers by virtue of their sensitivity to intense mechanical, thermal and irritant chemical stimuli. As immune cells, they possess many of the same molecular recognition pathways for danger. Thus, they express PRRs including Toll-like receptors 3, 4, 7, and 9, and stimulation by Toll-like receptor ligands leads to induction of inward currents and sensitization in TRPs. In addition, the expression of inflammasomes in neurons and the involvement of TRPs in central nervous system diseases strongly support a role of TRPs in inflammasome-mediated neurodegenerative pathologies. This field is still at its beginning and further studies may be required.Overall, these studies highlight the therapeutic potential of targeting the inflammasomes in proinflammatory, autoinflammatory and metabolic disorders associated with undesirable activation of the inflammasome by using specific TRP antagonists, anti-human TRP monoclonal antibody or different molecules able to abrogate the TRP channel-mediated inflammatory signals

The incidence and characteristics of clozapine-induced fever in a local psychiatric unit in Hong Kong

Objective: To determine the incidence, characteristics, and predictors of clozapine-induced fever in a sample of patients in a local psychiatric unit. Method: A retrospective review of case notes of 227 inpatients newly started on clozapine from March 2003 to December 2006 was conducted. Demographic characteristics, presence of fever, investigations carried out, fever characteristics, and complications of fever were recorded and analyzed. Patients with clozapine-induced fever were compared with their fever-free counterparts on demographic and clinical factors. Multivariate logistic regression was performed to identify predictors of clozapine-induced fever. Results: Thirty-one out of 227 patients (13.7%) developed clozapine-induced fever. The means for day of onset of clozapine-induced fever after clozapine initiation and duration of fever were 13.7 and 4.7 days, respectively. The mean highest body temperature was 38.8°C. Fever resolved within 48 hours after clozapine discontinuation in 79% of the patients with clozapine-induced fever. One out of 7 patients (14.3%) had fever on re-challenge. Clozapine-induced fever was associated with rate of titration more than 50 mg/wk (OR 18.9; 95% CI 5.3 to 66.7; P < 0.01), concomitant use of valproate (OR 3.6; 95% CI 1.5 to 8.9; P = 0.01), and presence of physical illnesses (OR 3.2; 95% CI 1.2 to 8.3; P = 0.02). Conclusion: Clozapine-induced fever is common. Temporary withdrawal of clozapine may result in resolution of fever, and clozapine re-challenge may be considered after fever subsides. Slower rate of clozapine titration may be helpful in patients with underlying physical illness and concomitant valproate treatment.link_to_subscribed_fulltex

Formation of titanium nitride barrier layer in nickel-titanium shape memory alloys by nitrogen plasma immersion ion implantation for better corrosion resistance

Nickel-titanium shape memory alloys (NiTi) are potentially useful in orthopedic implants due to their super-elasticity and shape memory properties. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, we describe our fabrication of TiN barrier layers in NiTi by nitrogen plasma immersion ion implantation followed with vacuum annealing at 450°C or 600°C. Our results show that the barrier layer is not only mechanically stronger than the NiTi substrate, but also is effective in impeding the out-diffusion of Ni from the substrate. Among the samples, the 450°C-annealed TiN barrier layer possesses the highest mechanical strength and best Ni out-diffusion impeding ability. The enhancement can be attributed to the consolidation of the Ti-N layer resulting from optimal diffusion at 450°C. © 2005 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Improvements of anti-corrosion and mechanical properties of NiTi orthopedic materials by acetylene, nitrogen and oxygen plasma immersion ion implantation

Nickel-titanium shape memory alloys (NiTi) are useful materials in orthopedics and orthodontics due to their unique super-elasticity and shape memory effects. However, the problem associated with the release of harmful Ni ions to human tissues and fluids has been raising safety concern. Hence, it is necessary to produce a surface barrier to impede the out-diffusion of Ni ions from the materials. We have conducted acetylene, nitrogen and oxygen plasma immersion ion implantation (PIII) into NiTi alloys in an attempt to improve the surface properties. All the implanted and annealed samples surfaces exhibit outstanding corrosion and Ni out-diffusion resistance. Besides, the implanted layers are mechanically stronger than the substrate underneath. XPS analyses disclose that the layer formed by C2H2 PIII is composed of mainly TiCx with increasing Ti to C concentration ratios towards the bulk. The nitrogen PIII layer is observed to be TiN, whereas the oxygen PIII layer is composed of oxides of Ti4+, Ti3+ and Ti 2+. © 2005 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Anti-corrosion performance of oxidized and oxygen plasma-implanted NiTi alloys

Nickel-titanium shape memory alloys are useful orthopedic biomaterials on account of its super-elastic and shape memory properties. However, the problem associated with out-diffusion of harmful nickel ions in prolonged use inside the human body raises a critical safety concern. Titanium oxide films are deemed to be chemically inert and biocompatible and hence suitable to be the barrier layers to impede the leaching of Ni from the NiTi substrate to biological tissues and fluids. In the work reported in this paper, we compare the anti-corrosion efficacy of oxide films produced by atmospheric-pressure oxidation and oxygen plasma ion implantation. Our results show that the oxidized samples do not possess improved corrosion resistance and may even fare worse than the untreated samples. On the other hand, the plasma-implanted surfaces exhibit much improved corrosion resistance. Our work also shows that post-implantation annealing can further promote the anti-corrosion capability of the samples. © 2004 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Corrosion resistance, surface mechanical properties, and cytocompatibility of plasma immersion ion implantation-treated nickel-titanium shape memory alloys

Nickel-titanium shape memory alloys are promising materials in orthopedic applications because of their unique properties. However, for prolonged use in a human body, deterioration of the corrosion resistance of the materials becomes a critical issue because of the increasing possibility of deleterious ions released from the substrate to living tissues. We have investigated the use of nitrogen, acetylene, and oxygen plasma immersion ion implantation (PIII) to improve the corrosion resistance and mechanical properties of the materials. Our results reveal that the corrosion resistance and mechanical properties such as hardness and elastic modulus are significantly enhanced after surface treatment. The release of nickel is drastically reduced as compared with the untreated control. In addition, our in vitro tests show that the plasma-treated surfaces are well tolerated by osteoblasts. Among the three types of samples, the best biological effects are observed on the nitrogen PIII samples. © 2005 Wiley Periodicals, Inc.link_to_subscribed_fulltex