Antibacterial Properties of TiO2 Nanotubes coated with nano-ZnO and nano-Ag

TiO2 nanotubes grown on titanium alloy are known to increase the biocompatibility of the alloy when used in dental/orthopaedic implants. Furthermore, their nanotubular structures can act as antibacterial agent carrier and as a scaffold for tissue engineering with the aim of adding antibacterial properties to the implant. 

This study aims at fabricating an antibacterial and biocompatible nanocomposite coating on Ti-6Al-4V involving nano-ZnO and nano-Ag. Initially, TiO2 nanotubes were self-assembled on the polished surface of medical grade Ti-6Al-4V alloy discs using anodisation. First, silver nanoparticles were chemically reduced from silver ammonia using delta-δ-gluconolactone for different duration on the nanotubes to form TiO2-Ag composite coating. Nano hydroxyapatite (HA) was added to the latter coating with the aim of reducing toxicity from silver, hence forming TiO2-Ag-HA coating. Secondly, nano-ZnO was thermo-chemically grown on the TiO2 nanotubes using zinc nitrate and hexamethylenetetramine. They were then annealed at 350-550C hence forming TiO2-ZnO. HA was grown on the latter coating by a biomimetic method whereby the coated discs were placed in a concentrated simulated body fluid at 37C forming TiO2-ZnO-HA. The stability of the 4 coatings, TiO2-Ag, TiO2-Ag-HA, TiO2-ZnO and TiO2-ZnO-HA were assessed using the dialysis method (n=3 each) and then exposed to Staphylococcus aureus for 24 hours in brain heart infusion (BHI) broth. 

Their antibacterial properties were assessed using different assays and microscopic imaging with respect to different controls (n=6 each for assays and n=3 for imaging). Their biocompatibility properties were assessed in the presence of primary human osteoblast cells in DMEM media with the help of biochemical assays, molecular gene expression and microscopic imaging (n=3). Both silver and zinc coated nanotubes showed significant level of antibacterial properties with silver coating being more bactericidal than the coating containing zinc. Nonetheless, the zinc oxide coatings were more biocompatible than the silver coating. Nano silver and zinc oxide containing composite coatings were successfully synthesised and tested in the presence of bacteria and human cells. The final conclusion was that nano-silver was still toxic and nano-ZnO coatings were more biocompatible.

Thesis

Urvashi Fowdar Gunputh, Antibacterial Properties of TiO2 Nanotubes coated with nano-ZnO and nano-Ag, PhD thesis, University of Plymouth, 2018.

Publications arising from the research

U Danookdharree, HR Le and C Tredwin. The effect of initial etching sites on the morphology of anodised TiO2 nanotubes on Ti-6Al-4V alloy, Journal of Electrochemical Society, 2015, 162, E213-222.

U Gunputh and HR Le, Anodised TiO2 nanotubes as a scaffold for antibacterial silver nanoparticles on titanium implant, Materials Science and Engineering C, 1 October 2018, 91, 638-644.

U Gunputh and H Le, Composite coatings for implants and tissue engineering, In L Ambrosio (editor), Biomedical Composites ~ second edition, 2017, 111-138.  ISBN 978-0-08-100759-4.

UF Danookdharree, A Besinis, C Tredwin and RD Handy, Antibacterial properties and molecular biocompatibility of TiO2-ZnO nanocomposite coatings for dental implants, Journal of Dental Research, 2017, 96(Special Issue B), 13.

UF Gunputh, H Le, A Besinis, C Tredwin and RD Handy, Multilayered composite coatings of titanium dioxide nanotubes decorated with zinc oxide and hydroxyapatite nanoparticles: controlled release of Zn and antimicrobial properties against Staphylococcus aureus, International Journal of Nanomedicine, 16 May 2019, 14, 3583-3600.

UF Gunputh, H Le, K Lawton, A Besinis, C Tredwin and RD Handy, Antibacterial properties of silver nanoparticles grown in situ and anchored to titanium dioxide nanotubes on titanium implant against Staphylococcus aureus, Nanotoxicology, 2019, latest articles ahead of print.

Conference presentations

U Danookdharree, H Le, R Handy and C Tredwin, Antibacterial properties and molecular biocompatibility of TiO2-ZnO nanocomposite coatings for dental implants, BSODR Annual Meeting, 6-8 September 2017.

U Danookdharree, H Le, R Handy and C Tredwin, Synthesis of a long term antibacterial coating involving strongly adhered ZnO nanoparticles to titania nanotubes for hip implant material, Hip Surgery: A Joint Engineering and Surgical Challenge, Institution of Mechanical Engineers (IMechE), 3-4 November 2015.

U Danookdharree, H Le, R Handy and C Tredwin. Antibacterial coating made of strongly adhered nanosilver to titania nanotubes for dental implants, Annual Meeting, International Association for Dental Research, 14-16 September 2015.

U Danookdharree and HR Le, Antimicrobial silver nanoparticles in titanium dioxide nanotubes grown on Ti-6Al-4V medical grade alloy, 2nd Symposium on Diagnostics and the Developing World, Brunel University ~ London, 23 March 2015.

U Danookdharree, HR Le, R Handy and C Tredwin, Tailoring the interfacial adhesion of anodised TiO2 nanotubes on Ti-6Al-4V alloy for medical implants, 26th Annual Conference, European Society for Biomaterials (ESB), Liverpool ~ UK, 31 August – 3 September 2014.