Determination of Cu 2z ions release rate from antimicrobial copper bearing stainless steel by joint analysis using ICP-OES and XPS L. Ren 1,2 , J. Chong 1 , A. Loya 1 , Q. Kang 2 , J. L. Stair 3 , L. Nan 2 and G. Ren* 1 Antibacterial Cu bearing stainless steels (CuSS) have been developed recently and their performance has attracted significant attention widely in biomedical, healthcare and environ- mental facilities in cross-disciplines. The antibacterial ability and its efficiency of the CuSS are associated to the rate and concentration of Cu 2z ions releases from its surface. The surface properties such as corrosion resistance are also influenced by the amount and the rate of Cu ions released. Thus, the aim of this study focused on the determination of trace release amount of Cu 2z ions from a typical copper bearing 304 stainless steel (304CuSS). Meanwhile, the release of other key elements in the material such as Cr, Fe, Ni were also examined, and found these multiple elemental releases produced a highly synergistic effect on killing bacterium. The release rate of the metals from 304CuSS was conducted by an inductively coupled plasma optical emission spectrometry (ICP-OES). In this study, the commercial 304 stainless steel (304SS) was served as a control material, while the ICP results showed that the Cu 2z ions released from 304CuSS were maintained a constant level with a release rate as low as 0?8 ppb/day/cm 2 . This phenomenon could be explained by a coordinating role or synergistic effects of Cu, Fe, Cr, and Ni ions. XPS surface composition analysis showed a releases contribution results in day 1 and day 14 that the reduction trend of Cu quantities in through of the surface depth of 304CuSS is consistent and comprehensible. Keywords: Stainless steel, Copper, Cu, Antimicrobial, Inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS) This paper is part of a special issue on antimicrobial materials Introduction Stainless steel is well known for its anti-corrosion properties, which has cross-disciplines applications in a number of fields such as biomedical, healthcare and environmental devices and facilities. It is well known that copper (Cu) element in both its nanoparticle, micro- particles and bulk formations possesses excellent anti- bacterial capabilities. 1,2 Thus, we have developed and fabricated the innovative copper bearing stainless steels with excellent antibacterial ability in previous work. 3,4 One of the copper bearing stainless steels has been 304CuSS with 4 wt-% of copper in its composition, showed much more strong antibacterial activity against typical Staphylococcus aureus (S.aureus) and Escheri- chia coli (E.coli) compared to 304SS. 5,6 The antimicrobial ability of CuSS is ascribed to the release of trace amount of Cu 2z ions from the surface of the steel. 7 Cu 2z ions have long been known for antibacterial properties by damaging cell membranes and solidify proteins of bacteria cells, which is similar to the antibacterial mechanism of silver. 8 It was also explained that the bacterial DNA loses its replication ability that led to cellular proteins inactivated after the treatment with heavy metal ions such as Cu 2z ions. 9 Consequently, the release rate of a trace amount of Cu 2z ions is crucial to CuSS in terms of its level of antibacterial efficacy. The Cu 2z release rate also influences other properties such as corrosion. If the release rate is too fast, it would loss the corrosion resistance of the CuSS as a formation of local pitting. If it is too slow, it would not produce sufficient antibacter- ial efficiency. Thus, precise measurement of the amount of trace Cu 2z ions from the CuSS is significantly meaningful for guiding a system of design and fabrica- tion of the Cu bearing stainless steel metals with an appropriate amount of Cu immobilised in the stainless steel. The optimisation was done to allow that the formulated such as 304 Cu bearing stainless steel to 1 School of Engineering and Technology, University of Hertfordshire, Hatfield AL10 9AB, UK 2 Institute of Metal Research, Chinese Academy of Science, Shenyang, China 3 School of Life and Medical Sciences, University of Hertfordshire, Hatfield AL10 9AB, UK *Correspondent author, email g.g.ren@herts.ac.uk ß 2015 W. S. Maney & Son Ltd. Received 21 October 2014; accepted 29 December 2014 DOI 10.1179/1753555714Y.0000000264 Materials Technology: Advanced Biomaterials 2015 VOL 30 NO B2 B86