Relationship between Dislocation Density and Antibacterial Activity of Cryo-Rolled and Cold-Rolled Copper

• Published in: Materials Vol. 12; no. 2; p. 200
• Main Authors: Parmar, Vinod, Changela, Kandarp, Srinivas, B., Mani Sankar, Manimuthu, Mohanty, Sujata, Panigrahi, S. K., Hariharan, K., Kalyanasundaram, Dinesh
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09.01.2019; MDPI
• Subjects: Bacteria; Biofilms; Bone surgery; Cold; Cold rolling; Contact angle; Copper; Cytotoxicity; Dislocation density; Electric discharges; Equal channel angular pressing; Machining; Mechanical properties; Nanostructured materials; Nitrogen; Nosocomial infections; Plastic deformation; Stainless steel; Staphylococcus infections; Strain; Strain hardening; Tensile tests; United States > US; India; nanostructuring; dislocation; defects; nano-crystalline; copper; antibacterial; cryo-rolling; leaching
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma12020200

In the present work, cold rolling and cryo-rolling were performed on 99% commercially pure copper substrates. Both cold and cryo-rolling processes caused severe plastic deformation that led to an increase in dislocation density by 14× and 28× respectively, as compared to the pristine material. Increases in average tensile strengths, by 75% (488 MPa) and 150% (698 MPa), were observed in the two rolled materials as the result of the enhancement in dislocation density. In addition to strength, enhanced antibacterial property of cryo-rolled copper was observed in comparison to cold rolled and pristine copper. Initial adhesion and subsequent proliferation of bio-film forming Gram-positive bacteria Staphylococcus aureus was reduced by 66% and 100% respectively for cryo-rolled copper. Approximately 55% protein leakage, as well as ethidium bromide (EtBr) uptake, were observed confirming rupture of cell membrane of S. aureus. Inductively coupled plasma-mass spectroscopy reveals higher leaching of elemental copper in nutrient broth media from the cryo-rolled copper. Detailed investigations showed that increased dislocation led to leaching of copper ions that caused damage to the bacterial cell wall and consequently killing of bacterial cells. Cryo-rolling enhanced both strength, as well as antibacterial activity, due to the presence of dislocations.