In situ synthesis of biocompatible imidazolium salt hydrogels with antimicrobial activity

In Vitro Antibacterial and Anti-Inflammatory Properties of Imidazolium Poly(ionic liquids) Microspheres Loaded in GelMA-PEG Hydrogels

Repairing damaged tissue caused by bacterial infection poses a significant challenge. Traditional antibacterial hydrogels typically incorporate various components such as metal antimicrobials, inorganic antimicrobials, organic antimicrobials, and more. However, drawbacks such as the emergence of multi-drug resistance to antibiotics, the low antibacterial efficacy of natural agents, and the potential cytotoxicity associated with metal antibacterial nanoparticles in hydrogels hindered their broader clinical application. In this study, we successfully developed imidazolium poly(ionic liquids) (PILs) polymer microspheres (APMs) through emulsion polymerization. These APMs exhibited notable antibacterial effectiveness and demonstrated minimal cell toxicity. Subsequently, we integrated the APMs into a gelatin methacryloyl (GelMA)-polyethylene glycol (PEG) hydrogel. This composite hydrogel not only showcased strong antibacterial and anti-inflammatory properties but also facilitated the migration of human skin fibroblasts (HSF) and human umbilical vein endothelial cells (HUVECs) and promoted osteogenic differentiation in vitro.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Semi-IPN ionogel based on poly (ionic liquids)/xanthan gum for highly sensitive pressure sensor

In this paper, a novel ionogel with semi-interpenetrating poly (ionic liquids)/xanthan gum (PIL/XG) polymer network (semi-IPN) was prepared by using a simple one-pot method. The structure and the pressure sensing performance have been systematically investigated. It was found that introducing a low content (0.3-3.1 wt%) of XG significantly promoted the mechanical performance of ionogels with little effect on the ionic conductivity. The optimized PIL/XG containing 2.2 wt% XG exhibited high compression strength (761.0 kPa) and ionic conductivity (0.63 S/m at 25 °C). Such ionogels showed a liner response (0-100 kPa) and high sensitivity value of 6.86 kPa^-1 in a capacitive mode. Meanwhile, as a resistive sensor, PIL/XG exhibited a wide response range to dynamic pressure ranges with stable repeatability. Furthermore, this ionogel exhibited excellent bactericidal properties against both gram-positive bacteria and gram-negative bacteria. This research provides a potential approach for developing ionogels based on semi-IPN with pressure-sensitive and anti-bacterial properties.

Exploring the Absorption Mechanisms of Imidazolium-Based Ionic Liquids to Epigallocatechin Gallate

Imidazolium-based ionic liquids are wildly used in natural product adsorption and purification. In this work, one typical polymeric ionic liquid (PIL) was synthesized by using L-proline as the anion, which exhibited excellent adsorption capacity toward tea polyphenol epigallocatechin gallate (EGCG). The adsorption conditions were optimized with the response surface method (RSM). Under the optimum conditions, the adsorption capacity of the PIL for EGCG can reach as high as 552 mg/g. Dynamics and isothermal research shows that the adsorption process of EGCG by the PIL particularly meets the quasi-second-order kinetic equation and monolayer adsorption mechanism. According to thermodynamic parameter analysis, the adsorption process is endothermic and spontaneous. The results of theoretical calculation by molecular docking also demonstrated the interaction mechanisms between EGCG and the ionic liquid. Considering the wide application of imidazolium-based ionic liquids in component adsorption and purification, the present study can not only be extended to other similar experimental mechanism validation, but also be representative for guiding the synthesis of PIL and optimization of adsorption conditions.

Dynamic grafting of carboxylates onto poly(vinyl alcohol) polymers for supramolecularly-crosslinked hydrogel formation

Supramolecular hydrogels have attracted considerable interest due to their unique stimuli-responsive and self-healing properties. However, these hydrogel systems are usually achieved by covalent grafting of supramolecular units onto the polymer backbone, which in turn limits their reprocessability. Herein, we prepared a supramolecular hydrogel system by forming dynamic covalent crosslinks between 4-carboxyphenylboronic acid (CPBA) and polyvinyl alcohol (PVA). The system was then further crosslinked with either calcium ions or branched polyethylenimine (PEI) to generate hydrogels with distinctly different properties. Incorporation of calcium ions resulted in the formation of hydrogels with higher storage modulus of 7290 Pa but without self-healing properties. On the other hand, PEI-crosslinked hydrogel (PVA-CPBA-PEI) exhibited >2000% critical strain value, demonstrated high stability over 52 days and showed sustained antibacterial effect. A combination of supramolecular interactions and dynamic covalent crosslinks can be an alternate strategy to fabricate next generation hydrogel materials.

Fast Gelation of Poly(ionic liquid)-Based Injectable Antibacterial Hydrogels

Traditional antibacterial hydrogels have a broad-spectrum bactericidal effect and are widely used as wound dressings. However, the biological toxicity and drug resistance of these antibacterial hydrogels cannot meet the requirements of long-term clinical application. Imidazolium poly(ionic liquids) (PILs) are polymeric antibacterial agents exhibiting strong antibacterial properties, as they contain a strong positive charge. In this study, two imidazolium PILs, namely poly(N-butylimidazolium propiolic acid sodium) (PBP) and poly(N-(3,6-dioxaoctane) imidazolium propiolic acid sodium) (PDP), as high efficiency antibacterial agents, were synthesized by polycondensation reaction. Then, the PILs were compounded with polyethylene glycol (PEG) by a thiol-yne click reaction to prepare injectable antibacterial hydrogels. An in vitro assay showed that the injectable antibacterial hydrogels could not only quickly kill Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), but also had low toxicity for human skin fibroblasts cells (HSFs) and human umbilical vein endothelial cells (HUVECs), respectively. Additionally, the lipopolysaccharide (LPS) inflammation model revealed that the injectable antibacterial hydrogels also had anti-inflammatory effects, which would be advantageous to accelerate wound healing.

Embracing Additive Manufacturing Technology through Fused Filament Fabrication for Antimicrobial with Enhanced Formulated Materials

Antimicrobial materials produced by 3D Printing technology are very beneficial, especially for biomedical applications. Antimicrobial surfaces specifically with enhanced antibacterial property have been prepared using several quaternary salt-based agents, such as quaternary ammonium salts and metallic nanoparticles (NPs), such as copper and zinc, which are incorporated into a polymeric matrix mainly through copolymerization grafting and ionic exchange. This review compared different materials for their effectiveness in providing antimicrobial properties on surfaces. This study will help researchers choose the most suitable method of developing antimicrobial surfaces with the highest efficiency, which can be applied to develop products compatible with 3D Printing Technology.

Antimicrobial Property of Halogenated Catechols

Bacterial infection associated with multidrug resistance (MDR) bacteria is increasingly becoming a significant public health risk. Herein, we synthesized a series of halogenated dopamine methacrylamide (DMA), which contains a catechol side chain modified with either chloro-, bromo-, or iodo-functional group. Catechol is a widely used adhesive moiety for designing bioadhesives and coating. However, the intrinsic antimicrobial property of catechol has not been demonstrated before. These halogenated DMA were incorporated into hydrogels, copolymers, and coatings and exhibited more than 99% killing efficiencies against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. More importantly, hydrogel containing chlorinated DMA demonstrated broad-spectrum antimicrobial activities towards multiple MDR bacteria, which included methicillin resistant S. aureus (MRSA), vancomycin resistant enterococci (VRE), multi antibiotics resistant Pseudomonas aeruginosa (PAER), multi antibiotics resistant Acinetobacter baumannii (AB) and carbapenem resistant Klebsiella pneumoniae (CRKP). These hydrogels also demonstrated the ability to kill bacteria in a biofilm while exhibiting low cytotoxic. Based on molecular docking and molecular dynamics simulation, Cl-functionalized catechol can potentially inhibit bacterial fatty acid synthesis at the enoyl-acyl carrier protein reductase (FabI) step. The combination of moisture-resistant adhesive property, inherent antimicrobial property, and the versatility of incorporating halogenated DMA into different polymeric materials greatly enhanced the potential for using these monomers for designing multifunctional bioadhesives and coatings.

Designer broad-spectrum polyimidazolium antibiotics

We designed and synthesized antimicrobial compounds effective in killing pan-drug-resistant bacterial pathogens. These compounds have a large therapeutic window due to their low mammalian cell toxicity. A lead compound showed efficacy in treating murine model S. aureus and P. aeruginosa infections. In the case of the obligate respiratory bacterium P. aeruginosa we were unable to evolve strains resistant to these compounds. This paper points toward the potential of this type of compound to deal with the current threat of pan-resistant pathogens.

For a myriad of different reasons most antimicrobial peptides (AMPs) have failed to reach clinical application. Different AMPs have different shortcomings including but not limited to toxicity issues, potency, limited spectrum of activity, or reduced activity in situ. We synthesized several cationic peptide mimics, main-chain cationic polyimidazoliums (PIMs), and discovered that, although select PIMs show little acute mammalian cell toxicity, they are potent broad-spectrum antibiotics with activity against even pan-antibiotic-resistant gram-positive and gram-negative bacteria, and mycobacteria. We selected PIM1, a particularly potent PIM, for mechanistic studies. Our experiments indicate PIM1 binds bacterial cell membranes by hydrophobic and electrostatic interactions, enters cells, and ultimately kills bacteria. Unlike cationic AMPs, such as colistin (CST), PIM1 does not permeabilize cell membranes. We show that a membrane electric potential is required for PIM1 activity. In laboratory evolution experiments with the gram-positive Staphylococcus aureus we obtained PIM1-resistant isolates most of which had menaquinone mutations, and we found that a site-directed menaquinone mutation also conferred PIM1 resistance. In similar experiments with the gram-negative pathogen Pseudomonas aeruginosa, PIM1-resistant mutants did not emerge. Although PIM1 was efficacious as a topical agent, intraperitoneal administration of PIM1 in mice showed some toxicity. We synthesized a PIM1 derivative, PIM1D, which is less hydrophobic than PIM1. PIM1D did not show evidence of toxicity but retained antibacterial activity and showed efficacy in murine sepsis infections. Our evidence indicates the PIMs have potential as candidates for development of new drugs for treatment of pan-resistant bacterial infections.