Effect of Cationic Groups on the Selectivity of Ternary Antimicrobial Polymers

Bacterial Specific Recognition of Sulfonium Poly(Amino Acid) Adsorbents for Ultrafast MRSA Capture Against Bloodstream Infection

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections pose significant health risks, potentially leading to severe conditions such as bacteremia. Developing effective treatments to eliminate resistant bacteria from the bloodstream, simultaneously mitigate infection-related complications, and reduce mortality remains challenging. Herein, microspheres are synthesized with bacterial elimination and inflammation prevention by crosslinked sulfonium poly(amino acids). As-synthesized microsphere, PM1 0.6B MS, exhibits an ultrafast adsorption efficiency of 0.41 × 108 CFU mg-1 min-1 for MRSA, which positions the highest index among the reported resin and inorganic adsorptions. This bacterial-specific and efficient capture of PM1 0.6B MS is attributed to its strong interactions with teichoic acids in MRSA (Ka: 1.8 × 105 M-1) rather than acting with phospholipids of mammalian cells. Unlike the present resin-based adsorbent, for example, heparin-modified polyethylene in the only commercial Seraph® 100, PM1 0.6B MS kills adsorbed bacteria within 1 h and can be reused by simple treatment. Meanwhile, PM1 0.6B MS also shows good hemocompatibility and longer thrombin activation time to reduce the risk of thrombosis and hemolysis. In vivo experiments further confirm the abilities of PM1 0.6B MS to prevent inflammation by removing bacteria. This adsorbent is a promising candidate for early treating life-threatening bloodstream infections, potentially preventing bacteremia and subsequent organ damage.

Effect of Defined Block Sequence Terpolymers on Antifungal Activity and Biocompatibility

Invasive fungal infections cause over 3.7 million deaths worldwide annually, underscoring the critical need for new antifungal agents. Developing selective antifungal agents is challenging due to the shared eukaryotic nature of both fungal and mammalian cells. Toward addressing this, synthetic polymers designed to mimic host defense peptides are promising new candidates for combating fungal infections. This study investigates well-defined multiblock terpolymers with specific arrangements of cationic, hydrophobic, and hydrophilic groups, as potential antifungal agents. The block sequence in these copolymers significantly impacts their minimum inhibition concentration (MIC) against Candida albicans and biocompatibility. Furthermore, compared to their statistical counterparts, these block polymers exhibit lower MIC values in certain instances. Notably, triblock terpolymers containing a central hydrophobic block present an enhanced antifungal efficacy and biocompatibility. These findings highlight the potential of block sequence-controlled polymers as a versatile platform for developing customized and targeted antifungal therapies.

Polyacrylamide-Based Antimicrobial Copolymers to Replace or Rescue Antibiotics

Antibiotics save countless lives each year and have dramatically improved human health outcomes since their introduction in the 20th century. Unfortunately, bacteria are now developing resistance to antibiotics at an alarming rate, with many new strains of "superbugs" showing simultaneous resistance to multiple classes of antibiotics. To mitigate the global burden of antimicrobial resistance, we must develop new antibiotics that are broadly effective, safe, and highly stable to enable global access. In this manuscript, we report the development of polyacrylamide-based copolymers as a class of broad-spectrum antibiotics with efficacy against several critical pathogens. We demonstrate that these copolymer drugs are selective for bacteria over mammalian cells, indicating a favorable safety profile. We show that they kill bacteria through a membrane disruption mechanism, which allows them to overcome traditional mechanisms of antimicrobial resistance. Finally, we demonstrate their ability to rehabilitate an existing small-molecule antibiotic that is highly subject to resistance development by improving its potency and eliminating the development of resistance in a combination treatment. This work represents a significant step toward combating antimicrobial resistance.

Chemical Modification of Acrylonitrile-Divinylbenzene Polymer Supports with Aminophosphonate Groups and Their Antibacterial Activity Testing

Bacterial contamination is a major public health concern on a global scale. Treatment resistance in bacterial infections is becoming a significant problem that requires solutions. We were interested in obtaining new polymeric functionalized compounds with antibacterial properties. Three components (polymeric amine, aldehyde, and phosphite) were used in the paper in a modified "one-pot" Kabachnik-Fields reaction, in tetrahydrofuran at 60 °C, to create the N-C-P skeleton in aminophosphonate groups. Two copolymers were thus prepared starting from an acrylonitriledivinylbenzene (AN-15%DVB) copolymer containing pendant primary amine groups modified by grafting aminophosphonate groups, i.e., aminobenzylphosphonate (Bz-DVB-AN) and aminoethylphosphonate (Et-DVB-AN). The two copolymers were characterized by FT-IR spectroscopy, SEM-EDX, TGA, and antibacterial properties. It was shown that the novel products have antibacterial qualities against S. aureus and E. coli bacteria. The sample with the strongest antibacterial activity was Et-DVB-AN. We assessed how well the Weibull model and the first-order kinetic model represent the inactivation of microbial cells in our samples. The main advantage of the new antibacterial agents developed in this work is their easy recovery, which helps to avoid environmental contamination.

Effect of cyclic topology versus linear terpolymers on antibacterial activity and biocompatibility: antimicrobial peptide avatars

Host-defense peptides (HDPs) and their analogs hold significant potential for combating multidrug-resistant (MDR) bacterial infections. However, their clinical use has been hindered by susceptibility to proteases, high production costs, and cytotoxicity towards mammalian cells. Synthetic polymers with diverse topologies and compositions, designed to mimic HDPs, show promise for treating bacterial infections. In this study, we explored the antibacterial activity and biocompatibility of synthetic amphiphilic linear (LPs) and cyclic terpolymers (CPs) containing hydrophobic groups 2-ethylhexyl (E) and 2-phenylethyl (P) at 20% and 30% content. LPs were synthesized via RAFT polymerization and then cyclized into CPs through a hetero-Diels-Alder click reaction. The bioactivity of these terpolymers was correlated with their topology (LPs vs. CPs) and hydrophobic composition. LPs demonstrated superior antibacterial efficacy compared to CPs against four Gram-negative bacterial strains, with terpolymers containing (P) outperforming those with (E). Increasing the hydrophobicity from 20% to 30% in the terpolymers increased toxicity to both bacterial and mammalian cells. Notably, our terpolymers inhibited the MDR Gram-negative bacterial strain PA37 more effectively than gentamicin and ciprofloxacin. Furthermore, our terpolymers were able to disrupt cell membranes and rapidly eliminate Gram-negative bacteria (99.99% within 15 minutes). Interestingly, CPs exhibited higher hemocompatibility and biocompatibility with mammalian macrophage cells compared to LPs, showcasing a better safety profile (CPs > LPs). These findings underscore the importance of tailoring polymer architectures and optimizing the hydrophilic/hydrophobic balance to address challenges related to toxicity and selectivity in developing antimicrobial polymers.

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

Self-Cross-Linkable Maleic Anhydride Terpolymer Coating with Inherent High Antimicrobial Activity and Low Cytotoxicity

Developing coating materials with low cytotoxicity and high antimicrobial activity has been recognized as an effective way to prevent medical device-associated infections. In this study, a maleic anhydride terpolymer (PPTM) is synthesized and covalently attached to silicone rubber (SR) surface. The formed coating can be further cross-linked (SPM) through the self-condensation of pendent siloxane groups of terpolymer. No crack or delamination of SPM was observed after 500 cycles of bending and 7 day immersion in deionized water. The sliding friction force of a catheter was reduced by 50% after coating with SPM. The SPM coating without adding any extra antibacterial reagents can kill 99.99% of Staphylococcus aureus and Escherichia coli and also significantly reduce bacterial coverage, while the coating displayed no antimicrobial activity when maleic anhydride groups of SPM were aminated or hydrolyzed. The results of the repeated disinfection tests showed that the SR coated with SPM could maintain 87.3% bactericidal activity within 5 cycles. Furthermore, the SPM coating only imparted slight toxic effect (>85% viability) on L929 cells after 36 h of coculture, which is superior to the coating of aminated SPM conjugated with the antimicrobial peptide E6. The terpolymer containing maleic anhydride units have great potential as a flexible and durable coating against implant infections.

Understanding How Cationic Polymers' Properties Inform Toxic or Immunogenic Responses via Parametric Analysis

Cationic polymers are widely used materials in diverse biotechnologies. Subtle variations in these polymers' properties can change them from exceptional delivery agents to toxic inflammatory hazards. Conventional screening strategies optimize for function in a specific application rather than observing how underlying polymer-cell interactions emerge from polymers' properties. An alternative approach is to map basic underlying responses, such as immunogenicity or toxicity, as a function of basic physicochemical parameters to inform the design of materials for a breadth of applications. To demonstrate the potential of this approach, we synthesized 107 polymers varied in charge, hydrophobicity, and molecular weight. We then screened this library for cytotoxic behavior and immunogenic responses to map how these physicochemical properties inform polymer-cell interactions. We identify three compositional regions of interest and use confocal microscopy to uncover the mechanisms behind the observed responses. Finally, immunogenic activity is confirmed in vivo. Highly cationic polymers disrupted the cellular plasma membrane to induce a toxic phenotype, while high molecular weight, hydrophobic polymers were uptaken by active transport to induce NLRP3 inflammasome activation, an immunogenic phenotype. Tertiary amine- and triethylene glycol-containing polymers did not invoke immunogenic or toxic responses. The framework described herein allows for the systematic characterization of new cationic materials with different physicochemical properties for applications ranging from drug and gene delivery to antimicrobial coatings and tissue scaffolds.

Biocompatible cationic polypeptoids with antibacterial selectivity depending on hydrophobic carbon chain length

The overuse of antibiotics has triggered a new infection crisis and natural antimicrobial peptides (AMPs) have been extensively studied as an alternative to fight microorganisms. Polypeptoids, or polypeptide-biomimetics, offer similar properties to polypeptides and a highly tunable structure that has been synthesized by various methods such as ring opening polymerization (ROP) using N-carboxyanhydride monomers. Simultaneous high antibacterial activity and biocompatibility of a structure by efficient synthesis is desired in the application of those materials. Herein, a series of cationic polypeptoids (PNBs) with variable side chain lengths was obtained by introducing positive charges to the main chain in one step and preserving the backbone structure, namely polypeptoids (PNBM, PNBE, PNBB) with different end groups (methyl (M), ethyl (E), butyl (B)). To address the issue of infection in interventional biomedical implants, we report cost-effective modified polyurethane (PU) films (PU-PNBM, PU-PNBE, PU-PNBB) as physical-biological synergistic antibacterial surfaces that overcome problems such as steric hindrance and the solubility of the materials. Antibacterial selectivity was achieved by regulating the different side chain lengths. When methyl and ethyl were used as hydrophobic side chains, they can only selectively kill Gram-positive Staphylococcus aureus. PNBB, the most hydrophobic and with a butyl side chain can kill both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and inhibit the growth of bacterial biofilms. Effective in both solution and modified substrate, its biocompatibility is not compromised while the antibacterial properties are substantially improved. Furthermore, PU-PNBB films demonstrated their potential in vivo antimicrobial efficiency in a model of S. aureus infection established on mouse skin. The synthesis route and the surface modification strategies are convenient, providing a solution to the problem of poor biocompatibility in antimicrobial surface applications and a strategy for the use of peptide polymers for targeted therapy after specific infections in the biomedical field.

Biocidal Potency of Polymers with Bulky Cations

The performance of antimicrobial polymers depends sensitively on the type of cationic species, charge density, and spatial arrangement of cations. Here we report antimicrobial polymers bearing unusually bulky tetraaminophosphonium groups as the source of highly delocalized cationic charge. The bulky cations drastically enhanced the biocidal activity of amphiphilic polymers, leading to remarkably potent activity in the submicromolar range. The cationic polynorbornenes with pendent tetraaminophosphonium groups killed over 98% E. coli at a concentration of 0.1 μg/mL and caused a 4-log reduction of E. coli within 2 h at a concentration of 2 μg/mL, showing very rapid and potent bactericidal activity. The polymers are also highly hemolytic at similar concentrations, indicating a biocidal activity profile. Polymers of a similar chemical structure but with more flexible backbones were made to examine the effects of the flexibility of polymer chains on their activity, which turned out to be marginal. We also explore variants with different spacer arm groups separating the cations from the backbone main chain. The antibacterial activity was comparably potent in all cases, but the polymers with shorter spacer arm groups showed more rapid bactericidal kinetics. Interestingly, pronounced counterion effects were observed. Tightly bound PF₆^- counteranions showed poor activity at high concentrations due to gross aggregate formation and precipitation from the assay media, whereas loosely bound Cl^- counterions resulted in very potent activity that monotonically increased with increasing concentration. In this paper, we reveal that bulky phosphonium cations are associated with markedly enhanced biocidal activity, which provides an innovative strategy to develop more effective self-disinfecting materials.