Evaluation of antibacterial activity and influencing factors of normal and nanostructured copper-based materials

Copper-based materials have garnered extensive recognition for their effective nature against microorganisms and their minimal toxicity. However, the evaluation for their antibacterial activity is still in its nascent stages, and the evaluation results based on existing criteria are not representative of real-world application.

To evaluate the antibacterial activity and primary determinants of influence of copper-based materials in order to investigate their practical antibacterial activity and potential mechanisms of such materials.

Staphylococcus aureus and Escherichia coli bacterial suspensions were applied via inoculation onto the surfaces of normal and nanostructured copper foil. Following incubation of the inoculated surfaces under diverse experimental conditions-including varying compositions of the bacterial suspension, the use of chemical neutralizers, the existence of organic interferents, and low temperature and humidity-surviving bacteria were enumerated. Using the scanning electron microscopy and X-ray photoelectron spectroscopy, the surface changes of copper-based materials were examined.

Following 1 h of exposure to 37 °C and 90% relative humidity, Staphylococcus aureus was reduced by 4.45 log10 on normal copper foil, while all of the bacteria were eradicated on nanostructured copper foil. In addition, it was discovered that preparing a bacterial suspension with PBS results in a significant number of Escherichia coli fatalities during the test, whereas using TPS promotes the bacteria's normal growth. Furthermore, the outcomes of the antibacterial activity test were diminished when chemical neutralization was employed, and the presence of organic interferents had distinct impacts on normal copper foil and nanostructured copper foil. Additionally, low temperatures and humidity diminished the antibacterial activity of copper foil, whereas normal copper foil produced significantly better results.

While copper-based materials exhibit robust antibacterial activity as determined by standard assays, their efficacy in real-world applications is subject to various influencing mechanisms. In order to objectively evaluate the antibacterial activity of copper-based materials and provide precise guidance for their development and practical application, it is essential to regulate test conditions with targeted.