Antibacterial Properties of Silicone Membranes after a Simple Two-Step Immersion Process in Iodine and Silver Nitrate Solutions

Abstract

Silicone is widely used in packing materials, medical equipment, and separation membranes. Since microbial cells easily adhere to the surface of silicone materials and form biofilms, techniques for incorporating antimicrobial activity into silicone materials are in high demand. This study describes the preparation of silver Ag /silicone composite membranes through a simple two-step immersion process, utilizing an iodine solution followed by a silver nitrate solution at room temperature. Scanning electron microscopy SEM observations revealed that particles with sizes of several nanometers to several tens of nanometers were present on the silicone membrane surface; these particles were identified as silver iodide using energy-dispersive X-ray spectroscopy EDS . The Ag/silicone membrane possessed excellent antibacterial efficacy against Escherichia coli and Staphylococcus aureus, and the antibacterial efficacy R against both types of bacteria was R > 4, even after stomacher treatment or acidic treatment of pH 2-6 for 24 h. The mechanical strength of the silicone membrane was also maintained after antibacterial treatment, with Young s modulus values of 7.9 1.2 MPa and 8.3 1.5 MPa for the untreated membrane and Ag/silicone membrane, respectively p > 0.05 . In addition, the reduction in permeation performance of the Ag/silicone membrane was only 20%, despite the antibacterial treatment on the membrane surface. This antibacterial treatment method of silicone membranes can be conducted at room temperature 25 without special equipment, and may be applied to other types of silicone materials.

“Smart” Triiodide Compounds: Does Halogen Bonding Influence Antimicrobial Activities?

“…This results in membrane immobilization [6]. Iodine has a strong microbicidal effect on pathogens by causing such irreversible damages [6,27,48,50]. They lead to denaturation of amino acids and nucleic acids in the microbial cell, inhibition of metabolic pathways and destabilization of the cell membrane structure [32,38].…”

“…They lead to denaturation of amino acids and nucleic acids in the microbial cell, inhibition of metabolic pathways and destabilization of the cell membrane structure [32,38]. This takes place through microbial membrane penetration, intracytoplasmic protein oxidation and iodination of cell proteins [6,31,32,48,50]. All the microorganisms studied are inhibited strongly by the antimicrobial activity of the effective antiseptic iodine with ZOIs of about 80 mm (Table 1).…”

“…Such channels are present in the plasma membrane of Gram-positive bacteria and in both the outer and plasma membranes of Gram-negative bacteria [48]. The antibacterial activity of chitosan is due to an interaction between the positively charged chitosan (protonated amine groups) and the negatively charged bacterial membrane (LPS in Gram-negative bacteria and may be teichoic acid in the cell wall of Gram-positive bacteria) [50,51,53,57,58]. Similarly, the antimicrobial effect of [Na(12-crown-4) 2 ]I 3 is through the interaction between the partial positively charged carbon atoms in the crown ether complex and the negatively or partly negatively charged outer cell wall components of the microorganisms.…”

“…The iodide ion, with its lower lipophilicity and negative charge ( [49]. The small, uncharged and lipophilic iodine molecule acts rapidly as broad-spectrum microbicidal agent against Gram-positive and Gram-negative bacteria [27,48,50]. Larger hydrophilic molecules with molecular weights less than 600-700 pass across the outer membrane through porin channels [51].…”

Antibiofilm Effects of Heated Scallop Shell Powder on Campylobacter jejuni Biofilms

“…Therefore, this study aimed to explore the effects of HSSP treatment on C. jejuni biofilms. In recent years, superior materials with antimicrobial activity, such as silver nanoparticles [28,29] and graphene oxide [30,31], have been reported, but these materials cannot be added directly to food. Contrastingly, HSSP is approved as a food additive in Japan, and it provides calcium supplementation in addition to improved shelf life owing to its antimicrobial activity.…”