Synthetic Mimics of Antimicrobial Peptides (SMAMPs) in Layer‐by‐Layer Architectures: Possibilities and Limitations

Abstract

Polymer‐based synthetic mimics of antimicrobial peptides (SMAMPs) show promising antimicrobial activity in solution and as surface‐attached networks. In this paper, their potential as active ingredients in layer‐by‐layer (LbL) assemblies is evaluated. These consist of the weak, anionic polyelectrolyte poly(acrylic acid), and either the hydrophobic butyl SMAMP or the hydrophilic diamine SMAMP (both of which are cationic, weak polyelectrolytes). In situ surface plasmon resonance spectroscopy is used to optimize the LbL assembly conditions. An “overshooting” is observed when depositing the SMAMP layer. Zeta potential measurements show that the layer charge inversion is reduced at each build‐up step due to layer interpenetration. Thus, the positive charge of LbL assemblies with SMAMPs as the top layer is low; a significant part is consumed to maintain layer stability. This leads to reduced antimicrobial activity. Fine‐tuning of the assembly and post‐treatment conditions leads to SMAMP‐PAA LbL systems with optimized antimicrobial activity and stability.

Polymer‐Based Surfaces Designed to Reduce Biofilm Formation: From Antimicrobial Polymers to Strategies for Long‐Term Applications

“…There were also attempts to make simultaneously antimicrobial and protein‐repellent material using the layer‐by‐layer (LbL) approach, in which alternating layers of polyanions and antimicrobial polycations were applied onto a surface . The idea behind this application of LbL is that the two polymers do not form a stack of discrete polymer layers; the individual polymers rather undergo mixing.…”

“…Thus, the surface would contain sufficient cationic polymer patches to be antimicrobial, but these would be neutralized by patches of the anionic polymer so that the material is overall protein‐repellent. The data from the above cited LbL studies and our own work indicate that it is very difficult to obtain LbL materials that are antimicrobially active, protein‐repellent, and at the same time stable under physiological conditions. In some cases, this was solved by covalent cross‐linking of the two polymers involved .…”

“…[19] There were also attempts to make simultaneously antimicrobial and protein-repellent material using the layer-by-layer (LbL) approach, in which alternating layers of polyanions and antimicrobial polycations were applied onto a surface. [111][112][113][114] The idea behind this application of LbL is that the two polymers do not form a stack of discrete polymer layers; the individual polymers rather undergo mixing. Thus, the surface would contain sufficient cationic polymer patches to be antimicrobial, but these would be neutralized by patches of the anionic polymer so that the material is overall protein-repellent.…”

Fluorescent ROMP Monomers and Copolymers for Biomedical Applications

“…Under these conditions, every chain is fluorescently labeled and elaborate purification is unnecessary, as there are no low molecular weight fluorescent functional bioactive monomers, resulting in bioactive fluorescent copolymers for biological studies and materials applications, e.g., surface coatings. [37][38][39][40][41][42] These polymers were based on exooxanorbornene imide (M1, M2, and M3, Figure 2) and exo-5-norbornene 2-carboxylic acid (M4 and M5, Figure 2), i.e., they had polymerizable units similar to those of functional bioactive monomers frequently used in our research (M6, M7, M8, and M9, respectively, all also in the exo-configuration, Figure 2). Further design criteria for the fluorescent monomers were that the fluorophores should be as small as possible and that the monomers could not contain hydrophobic spacers, as this would have changed the overall bioactivity of the target copolymers.…”

“…In this paper, we present the synthesis and ring‐opening metathesis copolymerization of five fluorescent monomers with functional bioactive monomers, resulting in bioactive fluorescent copolymers for biological studies and materials applications, e.g., surface coatings . These polymers were based on exo ‐oxanorbornene imide ( M1 , M2 , and M3 , Figure ) and exo ‐5‐norbornene 2‐carboxylic acid ( M4 and M5 , Figure ), i.e., they had polymerizable units similar to those of functional bioactive monomers frequently used in our research ( M6 , M7 , M8 , and M9 , respectively, all also in the exo ‐configuration, Figure ).…”