Antibacterial properties of Ag/TiO2/PDA nanofilm on anodized 316L stainless steel substrate under illumination by a normal flashlight

Surface Modification of Stainless Steel for Enhanced Antibacterial Activity

Stainless-steel grade 316L is widely used in medical and food processing applications due to its corrosion resistance and durability. However, its inherent lack of antibacterial properties poses a challenge in environments requiring high hygiene standards. This study investigates a novel surface modification approach combining electrochemical anodization and nonthermal plasma treatment to enhance the antibacterial efficacy of SS316L. The surface morphology, roughness, chemical composition, and wettability of the modified surfaces were systematically analyzed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and water contact angle (WCA) measurements. SEM revealed the formation of tunable nanoporous structures with pore diameters ranging from 100 to 300 nm, depending on the applied anodizing voltage (40 and 60 V). AFM measurements demonstrated that surface roughness varied significantly with anodizing voltage, from 4.3 ± 0.4 nm at 40 V to 15.0 ± 0.6 nm at 60 V. XPS analysis confirmed the presence of Cr2O3, a key oxide for corrosion resistance, and revealed increased oxygen concentration after plasma treatment, indicating enhanced surface oxidation. Wettability studies showed that plasma treatment changed the surfaces to superhydrophilic, with WCAs below 5°. Antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was significantly improved, with plasma-treated samples exhibiting up to 92% reduction in bacterial adhesion. These results demonstrate that the combined anodization and plasma treatment process effectively enhances the antibacterial and surface properties of SS316L, making it a promising strategy for applications in medical and food processing industries.

Polydopamine antibacterial materials

Recently, the development of polydopamine (PDA) has demonstrated numerous excellent performances in free radical scavenging, UV shielding, photothermal conversion, and biocompatibility. These unique properties enable PDA to be widely used as efficient antibacterial materials for various applications. Accordingly, PDA antibacterial materials mainly include free-standing PDA materials and PDA-based composite materials. In this review, an overview of PDA antibacterial materials is provided to summarize these two types of antibacterial materials in detail, including the fabrication strategies and antibacterial mechanisms. The future development and challenges of PDA in this field are also presented. It is hoped that this review will provide an insight into the future development of antibacterial functional materials based on PDA.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.