A sulfonate-based polypeptide toward infection-resistant coatings

Biocompatible quaternary pullulan functionalized 2D MoS2 glycosheet-based non-leaching and infection-resistant coatings for indwelling medical implants

Medical implants are frequently used in medicine and reconstructive surgery to treat various pathological and anatomical conditions. However, over time, biofilm formation on the surface of these implants can cause recurrent infections and subsequent inflammatory responses in the host, resulting in tissue damage, necrosis, and re-hospitalization. To address these implant-associated infections, the best approach is to create antimicrobial coatings. Here, we report the fabrication of a biocompatible, non-leaching, and contact-based antibacterial coating for implants using quaternary pullulan functionalized MoS2 (MCP) glycosheets. The cationic MCP glycosheets were coated on the surfaces of polydopamine-modified stainless steel and polyvinyl fluoride substrates through a simple process of electrostatic interaction. The developed coating showed excellent antibacterial activity (>99.5%) against E. coli and S. aureus that remained stable over 30 days without leaching out of the substrates and retained its antibacterial activity. MCP-coated implants did not induce any acute or sub-chronic toxicity to mammalian cells, both in vitro and in vivo. Furthermore, MCP coating prevented S. aureus colonization on stainless steel implants in a mouse model of implant-associated infection. The MCP coating developed in this study represents a simple, safe, and effective antibacterial coating for preventing implant-associated infections.

Host defense peptide mimicking cyclic peptoid polymers exerting strong activity against drug-resistant bacteria

Extensive use of antibiotics accelerates the emergence of drug-resistant bacteria and related infections. Host defense peptides (HDPs) have been studied as promising and potential therapeutic candidates. However, their clinical applications of HDPs are limited due to their high cost of synthesis and low stability upon proteolysis. Therefore, HDP mimics have become a new approach to address the challenge of bacterial resistance. In this work, we design the amphiphilic peptoid polymers by mimicking the positively charged and hydrophobic structures of HDPs and synthesize a series of cyclic peptoid polymers efficiently via the polymerization on α-amino acid N-substituted glycine N-carboxyanhydrides (α-NNCAs) using 1,8-diazabicycloundec-7-ene (DBU) as the initiator. The optimal cyclic peptoid polymer, poly(Naeg_0.7Npfbg_0.3)₂₀, displays strong antibacterial activities against drug-resistant bacteria, but low hemolysis and cytotoxicity. In addition, the mode-of-action study indicates that the antibacterial mechanism is associated with bacterial membrane interaction. Our study implies that HDP mimicking cyclic peptoid polymers have potential application in treating drug-resistant bacterial infections.

A cationic BODIPY photosensitizer decorated with quaternary ammonium for high-efficiency photodynamic inhibition of bacterial growth

On account of the constant evolution of antibiotic-resistant bacteria, the effects of existing antibacterial materials are being gradually weakened, and the difficulty in curing infectious diseases is increasing. Therefore, more novel antibacterial materials or methods are eagerly required to combat microbial infections. Recently, the advantages of photodynamic therapy in the antibacterial field have gradually been validated. Herein, a trimethylamine (TMA) salt-modified 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) photosensitizer (BODIPY-TMA) was synthesized for antibacterial applications. Due to the positive charge of the TMA group, enhanced interactions were observed between the prepared BODIPY-TMA nanoparticles (BODIPY-TMA NPs) and negatively-charged bacterial membranes. The BODIPY-TMA NPs showed much better antibacterial effect toward both S. aureus and E. coli compared with their BODIPY-Br NPs counterpart without a positive charge. Moreover, the BODIPY-TMA NPs efficiently prevented the formation of biofilms and destroyed pre-established biofilms. Thus, such positively-charged photosensitizers may pave the way for the exploration of highly effective antibacterial agents.

Preparation of antibacterial polypeptides with different topologies and their antibacterial properties

Antimicrobial peptides (AMPs) are attractive antimicrobial agents used to combat bacterial infections, and have been advanced to be one of the most promising alternatives to conventional antibiotics. They stand out for their attractive broad-spectrum activity, unmatched antibacterial mechanism that is not prone to develop drug resistance and diversified topologies, which can be fabricated with manifold amino acid blocks. In this study, using n-hexylamine and amine-terminated polyamidoamine dendrimers (Gx-PAMAM, x = 1-2) as initiators, a series of AMPs with linear and star-shaped topological structures were constructed via the controllable ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs). The antibacterial performances of the tailored linear and star-shaped AMPs were comprehensively evaluated in both solution states and surface-bonded states. The results indicated that the star-shaped AMPs exhibited enhanced bactericidal activity against Gram-negative E. coli and similar bactericidal activity against Gram-positive S. aureus when compared with the linear AMPs. It is worth mentioning that star-shaped AMPs demonstrated a significantly faster bactericidal efficiency (completely killed bacteria within 5 min at a concentration of 2 × MIC for S. aureus) than their linear analogues (took 15 min to achieve the same effect). However, when the AMPs were immobilized to the surface, they similarly exhibited superior antibacterial activity and fast bactericidal efficiency towards S. aureus and E. coli in the case of the same surface grafting amount. In addition, both the surfaces grafted with AMPs of different topologies demonstrated favorable biocompatibility in vitro.