Antifouling and Antimicrobial Mechanism of Tethered Quaternary Ammonium Salts in a Cross-linked Poly(dimethylsiloxane) Matrix Studied Using Sum Frequency Generation Vibrational Spectroscopy

Abstract

Poly(dimethylsiloxane) (PDMS) materials containing chemically bound (''tethered'') quaternary ammonium salt (QAS) moieties are being developed as new contact-active antimicrobial coatings. Such coatings are designed to inhibit the growth of microorganisms on surfaces for a variety of applications which include ship hulls and biomedical devices. The antimicrobial activity of these coatings is a function of the molecular surface structure generated during film formation. Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study polymer surface structures at the molecular level in different chemical environments. SFG was successfully used to characterize the surface structures of PDMS coatings containing tethered QAS moieties that possess systematic variations in QAS chemical composition in air, in water, and in a nutrient growth medium. The results indicated that the surface structure was largely dependent on the length of the alkyl chain attached to the nitrogen atom of the QAS moiety as well as the length of alkyl chain spanning between the nitrogen atom and silicon atom of the QAS moiety. The SFG results correlated well with the antimicrobial activity, providing a molecular interpretation of the activity. This research showed that SFG can be effectively used to aid in the development of new antimicrobial coating technologies by correlating the chemical structure of a coating surface to its antimicrobial activity.

Antibacterial/Antiviral Property and Mechanism of Dual-Functional Quaternized Pyridinium-type Copolymer

“…It has been proven that quaternary ammonium salt (QAS) moieties can affect the viability of Gram-positive and Gram-negative bacteria due to positive charges that exert a strong electrostatic interaction with negatively charged bacteria [25][26][27]. Therefore, the positive charge density of QAS antimicrobial agents plays a key role in their antimicrobial performance.…”

Molecular level studies of polymer behaviors at the water interface using sum frequency generation vibrational spectroscopy

“…80,81 SFG has been used to characterize the surfaces of PDMS materials with various quaternary ammonium salts (QAS) incorporated into the polymer. 20,21 In addition, the effects of bulk biocide concentration and the tethered QAS chain length on the surface structure of PDMS incorporated with QAS were investigated. Such surface structures can be well correlated to the antifouling activity tested using bacteria.…”

“…To improve such antibiofouling systems, molecular level research on polymer functional group orientation changes in aqueous environment has been performed as well. [19][20][21] In addition to biofouling, a particular section of recent biopolymer research focuses on polyelectrolytic systems, where the interactions between water, charged polymers, and surfactants have been studied. The folding mechanisms of polymers between water and oil interfaces are extremely important in a number of biological systems.…”

Characterization and Study of Properties in a Polar Solvent of a Functionalized and Quaternized Poly(dimethylsiloxane-co-methyl-hydridosiloxane)

“…Some of the most widely known modifiers are the quaternary ammonium salts (QAS) because of their ability to provide hydrophilic moieties. Polysiloxanes with QAS groups can act as cationic surfactants with a high capacity to reduce surface tension and allow good solubility in polar solvents [31][32][33][34]. For example, Majumdar et al [31,35] developed an environmentally friendly marine anti-repellent coating with pendant QAS groups.…”