Biocompatible Tough Ionogels with Reversible Supramolecular Adhesion.

Cohesive and interfacial adhesion energies are difficult to balance to obtain reversible adhesives with both high mechanical strength and high adhesion strength, although various methods have been extensively investigated. Here, a biocompatible citric acid/L-(-)-carnitine (CAC)-based ionic liquid was developed as a solvent to prepare tough and high adhesion strength ionogels for reversible engineered and biological adhesives. The prepared ionogels exhibited good mechanical properties, including tensile strength (14.4 MPa), Young's modulus (48.1 MPa), toughness (115.2 MJ m-3), and high adhesion strength on the glass substrate (24.4 MPa). Furthermore, the ionogels can form mechanically matched tough adhesion at the interface of wet biological tissues (interfacial toughness about 191 J m-2) and can be detached by saline solution on demand, thus extending potential applications in various clinical scenarios such as wound adhesion and nondestructive transfer of organs.

Regulation of Hydrophobic Structures of Antibacterial Guanidinium-Based Amphiphilic Polymers for Subcutaneous Implant Applications.

Antimicrobial peptide mimics have been used to kill bacteria and construct antibacterial materials. Precise design and construction of chemical structure are essential for easy access to highly effective antimicrobial peptide mimics. Herein, cationic guanidinium-based polymers (PGXs) with varying hydrophobic structures were synthesized to explore the structure and antibacterial activity relationship of antimicrobial peptide mimics and to construct antibacterial implants. The effect of the hydrophobic chemical structure, including carbon chain length and configuration, on the antimicrobial activities against both Escherichia coli and Staphylococcus aureus was investigated. The antibacterial activities of PGXs improved with increasing alkyl chain length, and PGXs with a straight-chain hydrophobic structure exhibited better bactericidal activities than those with cyclic alkane and aromatic hydrocarbon. Furthermore, PGXs grafted with poly(dimethylsiloxane) (PDMS-PGXs) showed a similar bactericidal change tendency of PGXs in solution. Additionally, the PDMS-PGXs showed potent antibiofilm performance in vitro, which can inhibit bacterial infection in vivo as subcutaneous implants. This study may propose a basis for the precise design and construction of antibacterial materials and provide a promising way of designing biomedical devices and implants with bacterial infection-combating activities.

Enabling Antibacterial and Antifouling Coating via Grafting of a Nitric Oxide-Releasing Ionic Liquid on Silicone Rubber.

Infections caused by bacteria and biofilms on the surfaces of biomedical devices and implants pose serious threats to public health. Herein, a nitric oxide (NO) gas-releasing quaternary ammonium-type ionic liquid (IL)-based coating on polydimethylsiloxane (PDMS), PDIL-NO, with effective and long-acting antibacterial and antifouling properties was prepared. N-(2-((2, 3-Dimethylbut-3-enoyl)oxy)ethyl)-N, N-dimethyloctan-1-aminium bromide (IL-Br), and 2-methyl-2-propenoic acid 2-(2-methoxyethoxy) ethyl ester were covalently grafted onto the surfaces of PDMS by a thiol-ene click chemical reaction, followed by incorporation of l-proline anions (Pro-) through anion exchange with Br- to adsorb NO gas. The prepared PDIL-NO showed a prolonged NO-releasing time (>1440 min) and a relatively high concentration (88 µM). Additionally, PDIL-NO possessed good and long-term antimicrobial activity, and could effectively reduce the adsorption of bovine serum albumin and adhesion of bacteria, as well as inhibit wound infection and reduce inflammation in vivo due to the synergetic effect of IL and the released NO. This study may provide a new approach to combat bacterial infections associated with biomedical devices and implants.

Fluorescent Imidazolium-Type Poly(ionic liquid)s for Bacterial Imaging and Biofilm Inhibition.

Fluorescent imidazolium-type poly(ionic liquid)s (PIL)s were synthesized by anion exchange of bromide (Br-) in poly(3-butyl-1-vinylimidazolium bromide) (PIL-Br) with a fluorescent anion, namely, 3-(4-(1,2,2-triphenylvinyl)phenoxy)propane-1-sulfonate (TPESO3-). Such an anion exchange provided antibacterial PILs with aggregation-induced emission (AIE) properties that simultaneously kill and image bacteria. These fluorescence and antibacterial properties could be regulated by controlling the Br-/TPESO3- ratio. The fluorescence intensity increases as this ratio increases, while the antibacterial property exhibits an opposite trend. Moreover, the AIE-type PILs are useful for fluorescently imaging dead bacteria (macroscopically and microscopically) and could effectively inhibit biofilm growth. This study provided a convenient method to obtain fluorescent PILs with adjustable antibacterial and imaging properties.

Porous Poly(Ionic Liquid) Membranes as Efficient and Recyclable Absorbents for Heavy Metal Ions.

Heavy metal ion pollution has become a serious environmental problem. Herein, this study reports the synthesis of poly(ionic liquid) (PIL) membranes via in situ photo-crosslinking of vinyl imidazole with both hydrophilic and hydrophobic ionic liquid monomers. The resultant amphiphilic polymer membranes are porous and exhibit high absorption capacity of metal ions (including Hg2+ , Pb2+ , Cu2+ , Cd2+ , and Zn2+ ) in both high (1000 mg L-1 ) and low (10 mg L-1 ) concentration metal ion solutions. These metal ionic absorption membranes are easily regenerated in acid solution and can be reused without significant decreases of absorption capacity after many cycles. These PIL membranes may have potential applications as eco-friendly and safe heavy metal ion removal materials.

CO2 Responsive Imidazolium-Type Poly(Ionic Liquid) Gels.

Poly(ionic liquid) (PIL) gels with CO2 stimulus responsiveness have been synthesized through the copolymerization of an imidazolium-type ionic liquid monomer with 2-(dimethyl amino) ethyl methacrylate. Upon bubbling with CO2 gas, the prepared PIL solution is converted to a transparent and stable gel, which can be turned back to the initial solution state after N2 bubbling. The reversible sol-gel phase transition behavior is proved by the reversible values of viscosity and ionic conductivity. The possible mechanism for such a reversible sol-gel phase transition is demonstrated by NMR, conductivity, and rheological measurements.

Antibacterial, anti-inflammatory and wet-adhesive poly(ionic liquid)-based oral patch for the treatment of oral ulcers with bacterial infection.

Oral aphthous ulcers are a common inflammatory efflorescence of oral mucosa, presenting as inflammation and oral mucosal damage and manifesting as pain. The moist and highly dynamic environment of the oral cavity makes the local treatment of oral aphthous ulcers challenging. Herein, a poly(ionic liquid)-based diclofenac sodium (DS)-loaded (PIL-DS) buccal tissue adhesive patch fabricated with intrinsically antimicrobial, highly wet environment adhesive properties and anti-inflammatory activities to treat oral aphthous ulcers was developed. The PIL-DS patch was prepared via polymerization of a catechol-containing ionic liquid, acrylic acid, and butyl acrylate, followed by anion exchange with DS-. The PIL-DS can adhere to wet tissues, including mucosa muscles and organs, and efficiently deliver the carried DS- at wound sites, exerting remarkable synergistic antimicrobial (bacteria and fungi) properties. Accordingly, the PIL-DS elicited dual therapeutic effects on oral aphthous ulcers with Staphylococcus aureus infection through antibacterial and anti-inflammatory activities, significantly accelerating oral aphthous ulcer healing as an oral mucosa patch. The results indicated that the PIL-DS patch, with inherently antimicrobial and wet adhesion properties, is promising for treating oral aphthous ulcers in clinical practice. STATEMENT OF SIGNIFICANCE: Oral aphthous ulcers are a common oral mucosal disease, which could lead to bacterial infection and inflammation in severe cases, especially for people with large ulcers or low immunity. However, moist oral mucosa and highly dynamic oral environment make it challenging to maintain therapeutic agents and physical barriers at the wound surface. Therefore, an innovative drug carrier with wet adhesion is urgently needed. Herein, a poly(ionic liquid)-based diclofenac sodium (DS)-loaded (PIL-DS) buccal tissue adhesive patch was developed to treat oral aphthous ulcers showing intrinsically antimicrobial and highly wet environment adhesive properties due to the presence of catechol-containing ionic liquid monomer. Additionally, the PIL-DS showed significantly therapeutic effects on oral aphthous ulcers with S. aureus infection through antibacterial and anti-inflammatory activities. We expect that our work can provide inspiration for the development of treatment for microbially infected oral ulcers.

Enhanced photocatalytic and antibacterial activity of acridinium-grafted g-C3N4 with broad-spectrum light absorption for antimicrobial photocatalytic therapy.

As a metal-free polymeric photocatalyst, graphitic carbon nitride (g-C3N4) has attracted great attention owing to its high stability and low toxicity. However, g-C3N4 suffers from low light harvesting ability which limits its applications in antimicrobial photocatalytic therapy (APCT). Herein, acridinium (ADN)-grafted g-C3N4 (ADN@g-C3N4) nanosheets are prepared via covalent grafting of ADN to g-C3N4. The obtained ADN@g-C3N4 exhibits a narrow optical band gap (2.12 eV) and a wide optical absorption spectrum (intensity a.u. > 0.30) ranging from ultraviolet to near-infrared region. Moreover, ADN@g-C3N4 would produce reactive oxygen species (ROS) under light irradiation to exert effective sterilization and biofilm elimination activities against both gram-negative and gram-positive bacteria. Molecular dynamics simulation reveals that the ADN@g-C3N4 may move toward, tile and insert the bacterial lipid bilayer membrane through strong van der Waals and electrostatic interaction, decreasing the order parameter of the lipid while increasing the conducive of ROS migration, inducing ADN@g-C3N4 with improved antimicrobial and antibiofilm performance. Moreover, ADN@g-C3N4 could efficiently eradicate oral biofilm on artificial teeth surfaces. This work may provide a broad-spectrum light-induced photocatalytic therapy for preventing and treating dental plaque diseases and artificial teeth-related infections, showing potential applications for intractable biofilm treatment applications. An acridinium-grafted g-C3N4 (ADN@g-C3N4) with a narrow band gap and broad-spectrum light absorption was synthesized. The narrow optical band gap and improved electrostatic interaction with bacterial lipid bilayer membrane of ADN@g-C3N4 strengthened the ROS generation and facilitated the diffusion of ROS to bacteria surface, leading to enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation. STATEMENT OF SIGNIFICANCE: An acridinium-grafted g-C3N4 (ADN@g-C3N4) with a narrow band gap and broad-spectrum light absorption was developed as an antimicrobial photocatalytic therapy agent. The ADN@g-C3N4 exhibited enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation, showing potential applications for intractable biofilm treatment.

Polypropylene Nonwoven Fabric@Poly(ionic liquid)s for Switchable Oil/Water Separation, Dye Absorption, and Antibacterial Applications.

Pollutants in wastewater include oils, dyes, and bacteria, making wastewater cleanup difficult. Multifunctional wastewater treatment media consisting of poly(ionic liquid)-grafted polypropylene (PP) nonwoven fabrics (PP@PIL) are prepared by a simple and scalable surface-grafting process. The fabricated PP@PIL fabrics exhibit impressive switchable oil/water separation (η>99 %) and dye absorption performance (q=410 mg g-1 ), as well as high antibacterial properties. The oil/water separation can be easily switched by anion exchanging of the PIL segments. Moreover, the multiple functions (oil/water separation, dye absorption, and antibacterial properties) occurred at the same time, and did not interfere with each other. The multifunctional fibrous filter can be easily regenerated by washing with an acid solution, and the absorption capacity is maintained after many recycling tests. These promising features make PIL-grafted PP nonwoven fabric a potential one-step treatment for multicomponent wastewater.

Recyclable and Intrinsically Anti-cyanobacterial Polyanionic Membranes.

Cyanobacteria blooms possess serious threats to water resources. Herein, we report the synthesis of polyanionic membranes (PA-M) by in situ photo-crosslinking of a sulfate-based anionic monomer followed by cation-exchange with metal cations, Fe3+ (PA-Fe), Cu2+ (PA-Cu), or Zn2+ (PA-Zn). The effect of cations on the anti-cyanobacterial activities against both Microcystis aeruginosa (M. aeruginosa) and Anabaena flos-aquae (A. flos-aquae) was investigated. All the prepared metal-containing membranes (PA-Fe, PA-Cu, PA-Zn) exhibit high anti-cyanobacterial activities and long-term anti-cyanobacterial stability, demonstrating that the synthesized PA-M membranes can be used as an effective and safe inhibitor to control cyanobacterial blooms.

Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations.

The structure-antibacterial activity relationship between the small molecular compounds and polymers are still elusive. Here, imidazolium-type ionic liquid (IL) monomers and their corresponding poly(ionic liquids) (PILs) and poly(ionic liquid) membranes were synthesized. The effect of chemical structure, including carbon chain length of substitution at the N3 position and charge density of cations (mono- or bis-imidazolium) on the antimicrobial activities against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by determination of minimum inhibitory concentration (MIC). The antibacterial activities of both ILs and PILs were improved with the increase of the alkyl chain length and higher charge density (bis-cations) of imidazolium cations. Moreover, PILs exhibited lower MIC values relative to the IL monomers. However, the antibacterial activities of PIL membranes showed no correlation to those of their analogous small molecule IL monomers and PILs, which increased with the charge density (bis-cations) while decreasing with the increase of alkyl chain length. The results indicated that antibacterial property studies on small molecules and homopolymers may not provide a solid basis for evaluating that in corresponding polymer membranes.