QUATERNARY AMMONIUM ANTIMICROBIAL POLYMERS
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QUATERNARY AMMONIUM ANTIMICROBIAL POLYMERS
Abraham J. Domb1, Nurit Beyth2, Shady Farah1 1
Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
2
Department of Prosthodontics, Hebrew University - Hadassah School of Dental Medicine,
Israel.
ABSTRACT Polymers possessing antimicrobial activity have been used for self sterilization surfaces as well as agents for treating contaminated water. Cationic polymers based on quaternary ammonium or guanidine groups have shown high inherent antimicrobial activity where the activity is related to the disruption of the microorganism cell wall. A range of antimicrobial nanoparticles possessing active quaternary ammonium groups with one of the alkyl is a an octyl chain have been synthesized. These nanoparticles were incorporated in dental restoration compositions to form self sterile composites. Quaternary ammonium polyethyleneimine nanoparticles with N-octyl dimethyl residues, demonstrated high antibacterial effect.
INTRODUCTION Antimicrobial agents of low molecular weight are widely used as antimicrobial drugs, food preservatives and for water and soil decontamination. However, they suffer from residual toxicity [1]. Polymeric antimicrobial agents are nonvolatile, chemically stable, have long-term antimicrobial activity, can be bound to the surface of interest and hardly permeate through biological membranes such as the skin [2]. Distinctively, polycationic antimicrobials have high surface density of active groups which might result in increased antimicrobial activity [3]. Quaternary ammonium compounds have a broad spectrum of antimicrobial activity against both Gram-positive and Gram-negative bacteria. Most of these polymers bearing quaternary ammonium groups appear to act by interacting non-specifically with the cell wall and disrupting negatively charged bacterial cell membrane [4]. The most common polyamines used for medical applications include: poly(L-lysine) (PLL), poly(N-alkyl-4-vinylpyridinium) salts (PVP), polyamidoamine (PAMAM) dendrimers, polyethyleneimine (PEI), and poly(2dimethylaminoethyl methacrylate) (PDEAEM). These polycations are either homopolymers or random copolymers having linear, branched or dendritic architectures. A number of reviews and books issues discuss the physiochemical, biochemical and therapeutic aspects of these polymers [5].
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Linear and crosslinked quaternary ammonium polyethyleneimine (QA-PEI) inhibits bacterial growth [6,7]. Lin et al. proposed a novel, non-release strategy for creating bactericidal surfaces which involves covalent coating with long hydrophobic polycationic chains based on PEI which was found effective against a variety of Gram-positive and Gram-negative bacteria [7]. Its antibacterial activity was found to be dependent on molecular weight of PEI indicating that N-alkylated PEI of low molecular weights, i.e. 2- and 0.8-kDa, had a weak bactericidal activity due to short chain length which probably do not penetrate bacterial cell. Due to the positive charge of the amino groups in physiol
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