# Novel Approaches to Combat Medical Device-Associated BioFilms
## 3 Novel Approaches to Combat Medical Device-Associated Biofilms
### Antimicrobial Peptides  
Antimicrobial peptides (AMPs), which are a type of small-molecular peptide and are also known as host defense peptides (HDPs) [10], widely exist in nature and are a part of the innate immunity of almost all living organisms. AMPs can be extracted from bacteria, fungi, plants, insects, amphibians, fish, birds, mammals, and even the human body and can also be produced by chemical synthesis. AMPs have broad-spectrum and rapid antibacterial activity and do not easily result in drug resistance. In particular, their killing effect on certain drug-resistant pathogens has attracted attention. They can be used as single antibacterial agents or combined with traditional antibiotics. To date, a variety of AMPs have been used in in vivo and in vitro studies, and some have been used in clinical practice, such as colicins and daptomycin. AMPs can not only exhibit powerful bactericidal activity, inhibit the formation of biofilms, and reduce or eliminate mature biofilms when the concentration is equal to or higher than the minimum inhibitory concentration (MIC) of the corresponding planktonic cells, but also display antibiofilm activity when the concentration is lower than the MIC of the corresponding planktonic cells [10]. This may be related to the mechanism underlying the multimode antibiofilm activity of AMPs. AMPs act on the bacterial cell membrane, forming different \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Surface-Modifying Compounds** & **Pathogens** & **Mechanism of Action** & **Reference** \\ \hline Isoeugenol & _S. aureus, L. monocytogenes,_ & Antibacterial & [141] \\  & and _P. fluorescens_ & & \\ \hline N-acetyl cysteine and chitosan film & _S. aureus_ & \begin{tabular}{c} Antibacterial and \\ antiadhesion \\ \end{tabular} & [144] \\ \hline AgNP & _E. coli_ and _S. aureus_ & \begin{tabular}{c} Antibacterial and \\ antiadhesion \\ \end{tabular} & [146] \\ \hline Silver-containing phosphonate monolayers & _E. coli_ and _S. epidermidis_ & Antiadhesion & [147] \\ \hline Hydrophobin (Vmh2 and Pac3) & _S. epidermidis_ & Antiadhesion & [152] \\ \hline ECA & _C. albicans_ & Antiadhesion & [153] \\ \hline Poly(glycidol) & _S. aureus_ & Antiadhesion & [154] \\ \hline tPA & _S. aureus_ & \
\begin{tabular}{c} Antiadhesion, increases the \\ sensitivity of biofilm \\ infections to antibiotics \\ \end{tabular} & [157] \\ \hline TMS/O2 & _S. aureus_ & Antiadhesion & [158] \\ \hline Direct thrombin inhibitors (argatroban, & _st staphylococcal_ & Antiadhesion & [159] \\ hirudin, and dabigatran) & _st staphylococcal_ & Antiadhesion & [160] \\ \hline DNase I & _S. mutans_ and _S. aureus_ &
\begin{tabular}{c} Affect the structural integrity \\ of the biofilm \\ \end{tabular} & [160] \\ \hline Polypyrrole & _S. mutans_ and _S. sanguinis_ & Affect the integrity of biofilms & [161] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of novel surface-modifying compounds used against biofilms and mechanisms of action. complex structures on the membrane through different mechanisms, such as the formation of barrel-state, toroidal pore, carpet, and aggregate models, which destroy the integrity and stability of the membrane, cause leakage of the cellular contents, and lead to the death of bacterial cells [165; 166; 167; 168; 169; 170; 171]. In addition, there are other potential antib biofilm mechanisms (Figure 1). Some AMPs can interfere with cellular metabolic processes and inhibit cell wall, nucleic acid, or protein biosynthesis by interacting with intracellular targets [172]. For example, B22, which is a derivative of BMAP-27B, can penetrate and kill established _Vibrio cholerae_ and _P. aeruginosa_ biofilms. After treatment with nanomolar concentrations of B22, _P. aeruginosa_ and _V. cholerae_ cells display expression changes in a variety of physiological metabolic processes, including protein synthesis, peptide glycan biosynthesis, respiration, and the detoxification of ROS.