Abstract
The incessant need for the elimination of pathogenic viruses and multi-drug resistant bacteria has been a critical issue during recent decades, and requires the creation of new antimicrobial materials. Our study describes the production of silver-modified anodic alumina substrates by two methods, and estimation of their bactericidal activity. Aluminum oxide coatings were obtained via an anodization process of low-purity aluminum in an acidic bath for different time periods. The realization of silver infiltration into the pores of the alumina layers was carried out employing two different routes—electrochemical deposition, and in situ thermal reduction. The obtained films were characterized using scanning electron microscopy (SEM). Changes in the surface morphology and thickness of the initial oxide structures after hot water sealing procedure were observed. The presence of silver inside the pores of the alumina layers was also assessed. It was found that silver electrodeposition resulted in greater surface saturation. Large silver accumulations were observed on the thinner anodic films which experienced electroplating for longer time periods. Finally, the antibacterial activity of the modified alumina structures against Gram-negative (Escherichia coli) and Gram-positive (Bacillus cereus) bacteria was evaluated. The results demonstrate that silver deposits acquired by the electrochemical technique improve the bactericidal efficiency of the anodic aluminum oxide (AAO) layers. On the contrary, alumina structures with chemically embedded Ag particles did not show significant antibacterial properties. Overall, the present studies demonstrate that biological activity of silver-doped AAO films depends on the techniques used for their modification.
Highlights
During the past couple of decades, porous anodic alumina, fabricated via an anodization process, has received great attention [1]
Bacterial cells were recovered from the test specimens by adding 10 mL of sterile phosphatebuffered saline (PBS) and vortexing for 1–2 min to detach them
As the insulating properties of alumina are strongly dependent on its uniform distribution and thickness, it was of great interest to investigate these features of the resulting oxide layers after 30 and 60 min anodization processes at the side edge of the metal pads
Summary
During the past couple of decades, porous anodic alumina, fabricated via an anodization process, has received great attention [1]. The porous structure of the anodic aluminum oxide (AAO) gives the opportunity for the incorporation of a variety of metal particles in different forms—nanowires, nanorods, and nanotubes [6]. The most simple and inexpensive approaches for the deposition of metallic particles into the pores of alumina substrates are electrochemical and chemical methods [9]. In the early 1970s, Hermann et al proposed 93 examples of electrochemical deposition using different solutions of Pb, Cd, Cr, Fe, Au, Co, Cu, Mn, Ni, Se, Ag, Te, Zn, and Sn [11] This type of surface modification is widely used to promote new colors and the corrosion resistance of anodic alumina substrates [10]. The aim of the current investigation was to produce silver-doped anodic a substrates by two different routes—electrochemical and chemical methods— evaluate their antibactericidal activity against Gram-negative (Escherichia co Gram-positive (Bacillus cereus) bacteria. For the preparation of all solutions, analytical-grade reagents were employed
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