Researchers at the Georgia Institute of Technology have developed an innovative electrochemical process that could provide a new defense against bacterial infections without contributing to the growing issue of antibiotic resistance. This breakthrough leverages the natural antibacterial properties of copper and creates nanometer-sized needle-like structures on the surface of stainless steel to effectively kill harmful bacteria such as E. coli and Staphylococcus.

The process is both practical and cost-effective, potentially reducing the reliance on chemical disinfectants and antibiotics in hospitals, kitchens, and other environments where surface contamination can lead to severe illnesses. This development is particularly significant given the global health threat posed by drug-resistant infections. A study in 2019 found that such infections were directly responsible for 1.27 million deaths and contributed to nearly 5 million additional deaths, ranking them among the leading causes of death across all age groups.

Eliminating Gram-positive bacteria without chemicals is relatively straightforward, but Gram-negative bacteria present a substantial challenge due to their thick, multilayered cell membranes. If these bacteria persist on surfaces, they can multiply rapidly. Anuja Tripathi, the lead author of the study and a postdoctoral fellow at the School of Chemical and Biomolecular Engineering, aimed to develop an antibiotic-free bactericidal surface effective against both Gram-negative and Gram-positive bacteria.

a) Nanotextured stainless steel fabrication and its modification using Cu by electrochemical techniques. b,c) SEM and d,e) AFM, b,d) images of pristine stainless steel, and c,e) nanotextured stainless steel etched for 30 s at 8 V.
a) Nanotextured stainless steel fabrication and its modification using Cu by electrochemical techniques. b,c) SEM and d,e) AFM, b,d) images of pristine stainless steel, and c,e) nanotextured stainless steel etched for 30 s at 8 V. Credit: A. Tripathi et al.

Tripathi, along with Professor William R. McLain Julie Champion and former doctoral students Jaeyoung Park and Thomas Pho, devised a two-pronged approach that not only overcomes these challenges but also prevents bacteria from developing drug resistance.

Firstly, they used an electrochemical method to etch the stainless steel surface, creating nanoscale needle-like structures that puncture bacterial cell membranes. In a subsequent electrochemical process, they deposited copper ions onto the steel’s surface. Copper interacts with and ultimately compromises the bacterial cell membranes, enhancing the antibacterial efficacy.

Tripathi explains, Nanotextured stainless steel can kill both Gram-negative and Gram-positive bacteria, but we wanted to enhance the antibacterial activity for surfaces that might be highly contaminated. The copper-coated nanotextured stainless steel demonstrated a significant increase in antibacterial activity, achieving a 97% reduction in Gram-negative E. coli and a 99% reduction in Gram-positive Staphylococcus epidermidis in their study.

During the Tripathi's electrochemical process, current and an acid electrolyte etch nano-sized needle-like structures on the surface of stainless steel. The structures are able to destroy bacterial cells.
During the Tripathi’s electrochemical process, current and an acid electrolyte etch nano-sized needle-like structures on the surface of stainless steel. The structures are able to destroy bacterial cells. Credit: Candler Hobbs / Georgia Tech

Despite the known antibacterial properties of copper, its widespread use for surface contamination control has been limited by cost. Tripathi’s method, which applies only a thin layer of copper ions to stainless steel, is cost-effective while maintaining high antibacterial activity.

The dual-action approach has promising applications in medical settings. Stainless steel modified in this way could be used for common tools that easily become contaminated, such as scissors and forceps, as well as for high-touch surfaces like door handles, railings, and sinks.

These are areas where stainless steel is already prevalent and where bacterial contamination is a significant concern, particularly in hospitals and other shared environments.

These four samples of stainless steel show the different stages of Tripathi's process. At left, an unmodified sample at the top and a sample after the electrochemical etching process at the bottom. On the right, two samples after copper ion deposition — four minutes for the top piece and 15 minutes for the bottom piece.
These four samples of stainless steel show the different stages of Tripathi’s process. At left, an unmodified sample at the top and a sample after the electrochemical etching process at the bottom. On the right, two samples after copper ion deposition — four minutes for the top piece and 15 minutes for the bottom piece. Credit: Candler Hobbs / Georgia Tech

The electrochemical process developed by Tripathi and her colleagues could also be valuable in the food service industry. She suggests that this technique could be integrated into existing industrial processes, where electrochemical coating methods are already employed for food storage containers made of stainless steel.

Looking ahead, future research will explore the effectiveness of copper-coated nanotextured stainless steel against other harmful cells. Tripathi is particularly interested in its potential for use in medical implants to prevent infections. Given its effectiveness against E. coli, a notorious pathogen, she remains hopeful about its broader applications.

Reflecting on a recent E. coli outbreak in Calgary, Canada, which underscored the urgency of combating such resilient bacteria on surfaces, Tripathi stated, If we can effectively eliminate E. coli, we stand a good chance of eradicating many surface bacteria.


Sources

College of Engineering (Georgia Institute of Technology) | Anuja Tripathi, Jaeyoung Park, et al., Dual Antibacterial Properties of Copper-Coated Nanotextured Stainless Steel. Small, 2024, 2311546. doi.org/10.1002/smll.202311546


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