# Innovative Antibacterial Polymer Coatings
## 3 Conclusions  
This review discusses various approaches to preparing coatings that exhibit antibacterial activity against different microbial agents, focusing on their inhibition or direct killing. The methods highlighted include: (i) The creation of coatings that release cytotoxic compounds to kill bacteria, ranging from traditional techniques to more innovative and advanced strategies; (ii) development of contact-active surfaces, which operate by disintegrating bacterial cell membranes upon contact; (iii) the formulation of anti-adhesive coatings designed to limit bacterial adhesion to various surfaces, utilizing superhydrophobic or hydrophilic properties. Many of these techniques involve surface modification through the incorporation of antibacterial substances using various methods like adsorption, covalent bonding, or ligand-receptor interactions. The use of antibiotics and antiseptics as antibacterial agents raises concerns about bacterial resistance, which may occur due to the continuous release of active compounds into the environment over extended periods. Another type of surface includes copper, silver, or other metal nanoparticles with pronounced antibacterial properties that kill bacteria by different mechanisms and may have practical applications in clinical practice. The key challenge with these coatings is that they contain only a fixed number of antibacterial agents, resulting in a temporary effect that may not provide lasting protection. Moreover, they may possess potential toxicity to human cells and environmental concerns with prolonged exposure or be susceptible to oxidation, which may reduce effectiveness over time. Good contact-killing abilities were demonstrated by coatings based on quaternary ammonium compounds (QAS) or chitosan against Gram-positive and Gram-negative bacteria. Still, they are not very effective against spores and fungi. Additionally, they are not suitable for long-term use and tend to degrade over time. The main disadvantage of using anti-adhesive surfaces is the use of polymers, and their fabrication is sometimes very complicated. They often have poor mechanical properties and can wear off due to abrasion, scratching, or repeated use; they degrade over time, thus losing their abilities. Currently, an innovative alternative involves surfaces that catalytically produce bactericides using externally applied chemical, electrical, or optical energy. This group includes light-activated antibacterial coatings, which are currently attracting significant research interest due to their ability to provide continuous surface disinfection, overcoming the limitations of other coatings. This process, triggered by the irradiation of specific compounds called photosensizers with visible light, results in the production of harmful components such as singlet oxygen and free radicals through photodynamic activity. Despite the large number of antibacterial coatings reported in the literature, the following main drawbacks and challenges remain as follows:  
Many reports focus on the antimicrobial activity against a limited number of Gram-negative and Gram-positive etalon strains. However, there is a lack of detailed investigations into the bactericidal activity of antibacterial coatings against various clinical strains, which are the primary contributors to nosocomial infections in hospitals and lead to high mortality rates among patients. Moreover, the mechanism by which bactericidal agents affect different types of bacterial cells, leading to their apoptosis and death, is not fully understood. This remains a challenge for researchers who are working to develop effective antibacterial coatings that possess bactericidal properties against not only etalon strains but also clinical strains. There is a lack of comprehensive investigations into the repeated testing cycles of bactericidal activity for the antibacterial coatings developed. This issue is especially critical because these coatings will undergo daily cleaning, especially in hospital environments.