Antibacterial coating of substrates based on cationic biocides-enhanced thin films of selected polystyrene-based copolymers

Developing antimicrobial coatings is an important challenge nowadays, significant for managing microbial contamination across various applications, including medical devices, food packaging, and waste management. This study examines the preparation, modification and characterization of specific polystyrene-block-polyisoprene-block-polystyrene (SIS) and polystyrene-block-polybutadiene-block-polystyrene (SBS) thin polymer films modified by selected cationic biocides (CB), namely chlorhexidine (CHX) and dodecyltrimethylammonium bromide (DTAB). Two approaches were used to prepare and modify polymer films. First, CBs were added directly to the polymer solution. Second, pristine samples were exposed to plasma or UV radiation and afterwards immersed in an ethanol solution of CBs. Morphology, chemical structure and surface properties of the samples were characterized. Furthermore, their stability was evaluated, with a focus on their antibacterial activity and adhesion to selected substrates. The antibacterial activity of films improved when modified with CHX, as demonstrated by testing against Escherichia coli and Staphylococcus aureus. Specifically, one of the CHX-modified samples resulted in a bacterial survival rate of only 0.2 % in comparison with the control, less than the survival rates observed in DTAB-modified samples. Surface characterization revealed that lower zeta potential and contact angle values exhibited a correlation with higher hydrophilicity and antimicrobial activity, especially for CHX-modified films. Particularly the effect of surface charge is significant and plays a vital role. This work demonstrates several positive results of incorporating antibacterial agents into a polymer matrix. It also provides new insights into these materials as potential antibacterial coatings for a wide range of applications.