Abstract
Severely broken bones often require external bone fixation pins to provide support but they can become infected. In order to reduce such infections, novel solutions are required. Titanium zirconium nitride (Ti-ZrN) and Ti-ZrN silver (Ti-ZrN/Ag) coatings were deposited onto stainless steel. Surface microtopography demonstrated that on the silver containing surfaces, Sa and Sv values demonstrated similar trends whilst the Ra, average height and RMS value and Sp values increased with increasing silver concentration. On the Ti-ZrN/Ag coatings, surface hydrophobicity followed the same trend as the Sa and Sv values. An increase in dead Staphylococcus aureus and Staphylococcus epidermidis cells was observed on the coatings with a higher silver concentration. Using CTC staining, a significant increase in S. aureus respiration on the silver containing surfaces was observed in comparison to the stainless steel control whilst against S. epidermidis, no significant difference in viable cells was observed across the surfaces. Cytotoxicity testing revealed that the TiZrN coatings, both with and without varying silver concentrations, did not possess a detrimental effect to a human monocyte cell line U937. This work demonstrated that such coatings have the potential to reduce the viability of bacteria that result in pin tract infections.
Highlights
Broken bones often require external bone fixation pins to provide support but they can become infected
Energy Dispersive X-Ray (EDX) analysis was undertaken on the four Titanium zirconium nitride (Ti-ZrN)/Ag coatings
Due to heavier elements being able to backscatter electrons more freely, they appeared on the image as a brighter phase resulting in the silver to be visualised as white nanoparticles showing their distribution throughout the surfaces (Fig. 2)
Summary
Broken bones often require external bone fixation pins to provide support but they can become infected. The development of pin-site infections are influenced by a number of patient-specific risk factors, including the surgical technique used, the use of prophylactic antibiotics and the post-operative pin care protocol[7]. This includes the overall maintenance of the external fixation devices (e.g. cleansing, dressing changes and showering)[7]. A pin tract infection can result in discomfort to the patient, additional cost due to treatment regimes (care, cleaning and replacement of device, increased use of drug delivery and antibiotics), as well as the development of other medical conditions including osteomyelitis, septic arthritis, toxic shock syndrome and bacteraemia, with the latter sometimes resulting in death[8]. Staphylococcus aureus infections have been reported to be the most common causative agent of metal biomaterial associated infections, whilst Staphylococcus epidermidis are more frequently associated with polymeric biomaterial infections[13]
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