• Antibacterial activity and biofilm inhibition by surface modified titanium alloy medical implants following application of silver, titanium dioxide and hydroxyapatite nanocoatings

      Besinis, Alexander; Hadi, Sanna Dara; Le, Huirong; Tredwin, Christopher; Handy, Richard; Plymouth University (Taylor and Francis, 2017-03-17)
      One of the most common causes of implant failure is peri-implantitis, which is caused by bacterial biofilm formation on the surfaces of dental implants. Modification of the surface nanotopography has been suggested to affect bacterial adherence to implants. Silver nanoparticles are also known for their antibacterial properties. In this study, titanium alloy implants were surface modified following silver plating, anodisation and sintering techniques to create a combination of silver, titanium dioxide and hydroxyapatite (HA) nanocoatings. Their antibacterial performance was quantitatively assessed by measuring the growth of Streptococcus sanguinis, proportion of live/dead cells and lactate production by the microbes over 24 h. Application of a dual layered silver–HA nanocoating to the surface of implants successfully inhibited bacterial growth in the surrounding media (100% mortality), whereas the formation of bacterial biofilm on the implant surfaces was reduced by 97.5%. Uncoated controls and titanium dioxide nanocoatings showed no antibacterial effect. Both silver and HA nanocoatings were found to be very stable in biological fluids with material loss, as a result of dissolution, to be less than 0.07% for the silver nanocoatings after 24 h in a modified Krebs-Ringer bicarbonate buffer. No dissolution was detected for the HA nanocoatings. Thus, application of a dual layered silver–HA nanocoating to titanium alloy implants creates a surface with antibiofilm properties without compromising the HA biocompatibility required for successful osseointegration and accelerated bone healing.
    • Antimicrobial silver nanoparticles in titaniumdioxide nanotubes grown on Ti-6Al-4V medical grade alloy

      Danookdharree, Urvashi; Le, Huirong; University of Plymouth (Royal Society of Chemistry, 2015-03-23)
    • Evaluation of environmental friendly Ag-PTFE composite coating for use in threaded compression fittings

      Sieh, Raymond; Le, Huirong; University of Derby; Plymouth University (Sage Publications, 2017-07-06)
      Threaded tubular fittings are used in a wide variety of industries for critical applications involving fluid transfer in a pressurised or vacuum system. These fittings are made of corrosion resistant metals such as stainless steel which are desirable in corrosive operating conditions; however, stainless steel is prone to galling which can cause threads to seize, resulting in loss of productivity. To prevent this, threads are electroplated using silver (Ag) coatings which prevent galling and serve as a solid lubricant during the connection make-up process. The Ag cyanide electroplating process currently used in industry is both hazardous to human health and its wastes are detrimental to the environment. The objective of this work is to evaluate environmental friendly self-lubricating Ag and Ag-polytetrafluoroethylene composite coatings using a non-cyanide electroplating process against the commercially available cyanide Ag coating through the analysis of torque-angle signatures and the torque-angle slope which characterises the make-up process. Results from the experiments suggest that the non-cyanide Ag-polytetrafluoroethylene coating is a potentially viable replacement option. Investigation and analysis of the coating performance have also highlighted potential risks of failure through poor lubrication during the make-up process and suggestions for improving the make-up process.
    • Process optimisation of non-cyanide Ag–PTFE metal matrix composite electroplating for threaded connections

      Sieh, Raymond; Le, Huirong; Cree, Alistair; University of Plymouth (2015-02-11)
    • Tailoring the interfacial adhesion of anodised TiO2 nanotubes on Ti-6Al-4V alloy for medical implants

      Danookdharree, Urvashi; Le, Huirong; Handy, Richard; Tredwin, Christopher; University of Plymouth (2014-09)
      Self-assembled nano-structure on the surface of bone/dental implants has attracted significant interest in the last few decades. In this context, anodic TiO2 nanotubes have been shown to have a beneficial effect on osteoblast differentiation and bone formation around implant [1-2]. However, there is uncertainty about the interfacial adhesion to substrate as a surface coating for medical implants [3]. In this study, the effects of anodising conditions on the morphology, composition and interfacial adhesion of the nanotubes grown on titanium alloy were investigated with various electrolytes, pH values and voltage seep rate.
    • Tribological properties of nanoclay reinforced polyimide nanocomposite coatings for alloy steels

      Meng, Maozhou; Le, Huirong; University of Derby; Department of Mechanical Engineering and Built Environment; College of Engineering and Technology; University of Derby; Derby UK; Department of Mechanical Engineering and Built Environment; College of Engineering and Technology; University of Derby; Derby UK (Wiley, 2017-06-30)
      A new process was developed to deposit uniform Montmorillonite nanoclay reinforced polyimide nanocomposite coating on alloy steels. The nanoclay particles were successfully dispersed in N, N-Dimethylacetamide using a combination of magnetic stirring, soaking, and ultrasonic agitation. It was found that the uniform and crack-free coating can be achieved. The tribological tests indicated that the nanocomposite coating has good adhesion to alloy steels, good load carrying capacity, relatively low friction, and wear. This nanocomposite is a promising material for some offshore, aerospace, and automotive structures that are subjected to sliding contact in corrosive environment.