Synergistic Poly(lactic acid) Antibacterial Surface Combining Superhydrophobicity for Antiadhesion and Chlorophyll for Photodynamic Therapy.

The problem of nosocomial infections caused by bacterial growth on material surfaces is an urgent threat to public health. Although numerous materials and methods have been explored to fight against infections, the methods are complicated and the materials are slightly toxic. It is highly desirable to develop an antibacterial strategy that kills bacteria effectively without drug resistance and cytotoxicity. Herein, we present a synergistic antibacterial polylactic acid (PLA) surface with superhydrophobic antibacterial adhesion and photodynamic bactericidal activity. Initially, the surface displayed low-adhesion superhydrophobicity and resisted most bacterial adhesion. Furthermore, completely non-toxic chlorophyll possessed excellent photodynamic bactericidal properties under non-toxic visible light, which was incorporated into micro-/nanoscale PLA surfaces. We achieved efficient antibacterial activity using completely non-toxic materials and a facile non-solvent-induced phase separation process. This non-toxic, simple, good biocompatible, and no drug-resistant strategy has great advantages in combating bacterial infections.

Fluorometric determination of ciprofloxacin using molecularly imprinted polymer and polystyrene microparticles doped with europium(III)(DBM)3phen.

The authors describe a microparticle-based system for the detection of the fluoroquinolone antibiotic ciprofloxacin. The method is using the tris(dibenzoylmethane)(1,10-phenanthroline)europium(III) luminophore in polystyrene microparticles along with a molecularly imprinted polymer (MIP) for ciprofloxacin. If ciprofloxacin is captured by the MIP, it quenches the fluorescence of the luminophores. Fluorescence drops linearly in the 0.5-100 µg L-1 ciprofloxacin concentration range, and the detection limit is 92 ng L-1. The method was applied to the analysis of fish samples to assess the analytical performance of the probe. Recoveries ranged from 85.4 to 86.6%, and relative standard deviations between 2.1 and 3.9% (for n = 5). Graphical abstract Schematic presentation of a microparticle-based probe using the tris(dibenzoylmethane)(1,10-phenanthroline)europium(III) luminophore in polystyrene particles along with a molecularly imprinted polymer for ciprofloxacin. After removal of template, carboxylic groups left in the probe can bind to ciprofloxacin through hydrogen bonds.

Injectable Conductive Hydrogel with Self-Healing, Motion Monitoring, and Bacteria Theranostics for Bioelectronic Wound Dressing.

Wounds at joints are difficult to treat and tend to recover more slowly due to the frequent motions. When using traditional hydrogel dressings, they are easy to crack and undergo bacterial infection, difficult to match and monitor the irregular wounds. Integrating multiple functions within a hydrogel dressing to achieve intelligent wound monitoring and healing remains a significant challenge. In this research, a multifunctional hydrogel is developed based on polysaccharide biopolymer, poly(vinyl alcohol), and hydroxylated graphene through dynamic borate ester bonding and supramolecular interaction. The prepared hydrogel not only exhibits rapid self-healing (within 60 s), injectable, conductive and motion monitoring properties, but also realizes in situ bacterial sensing and killing functions. It shows excellent bacterial sensitivity (within 15 min) and killing ability via the changes of electrical signals and photothermal therapy, avoiding the emergence of drug-resistant bacteria. In vivo experiments prove that the hydrogel can promote wound healing effectively. In addition, it displays great electromechanical performance to achieve real-time monitoring and prevent re-tearing of the wound at human joints. The injectable pH-responsive hydrogel with good biocompatibility demonstrates considerable potential as multifunctional bioelectronic dressing for the detection, treatment, management, and healing of infected joint wounds.

Theranostic antibacterial hydrogel based on biopolymers cross-linked and doped with phytic acid from rice bran for wound healing.

Theranostic antibacterial wound dressing is highly recommended in practical applications. The conventional methods of integrating diagnostic and therapeutic functions have the disadvantages of complicated preparation, mutual interference, inability to effectively broad spectrum antibacterial property, and easy to induce drug-resistant bacteria. Herein, a pH and light-responsive theranostic antibacterial hydrogel is developed by biopolymers polyvinyl alcohol (PVA) and polyaniline (PANI), and cross-linking with phytic acid (PA), which is widely present in rice bran. The biological polymer-based conductive hydrogel enables timely diagnosis and photothermal sterilization in-situ for wound healing. Because PANI is highly sensitive to pH changes in the bacterial microenvironment, the hydrogel can detect bacterial infections at concentrations as low as 103 CFU/mL. Subsequently, PANI absorbs near-infrared light to achieve on-demand exothermic sterilization (under 808 nm irradiation for 20 min, the killing ratios for Staphylococcus aureus and Escherichia coli reached almost 100 %). In addition, the hydrogel can monitor the intensity of joint movement to avoid wound re-tearing sensitively. In vitro cytotoxicity and hemocompatibility experiments and in vivo full-thickness infected wound model indicate that the hydrogel has good biocompatibility, antibacterial ability, and can accelerate the wound healing effectively. This work will promote the development of wearable electronic devices and precision medicine.

Stimuli-Responsive Antibacterial Materials: Molecular Structures, Design Principles, and Biomedical Applications.

Infections are regarded as the most severe complication associated with human health, which are urgent to be solved. Stimuli-responsive materials are appealing therapeutic platforms for antibacterial treatments, which provide great potential for accurate theranostics. In this review, the advantages, the response mechanisms, and the key design principles of stimuli-responsive antibacterial materials are highlighted. The biomedical applications, the current challenges, and future directions of stimuli-responsive antibacterial materials are also discussed. First, the categories of stimuli-responsive antibacterial materials are comprehensively itemized based on different sources of stimuli, including external physical environmental stimuli (e.g., temperature, light, electricity, salt, etc.) and bacterial metabolites stimuli (e.g., acid, enzyme, redox, etc.). Second, structural characteristics, design principles, and biomedical applications of the responsive materials are discussed, and the underlying interrelationships are revealed. The molecular structures and design principles are closely related to the sources of stimuli. Finally, the challenging issues of stimuli-responsive materials are proposed. This review will provide scientific guidance to promote the clinical applications of stimuli-responsive antibacterial materials.

Preparation of a carboxylated single-walled carbon-nanotube-chitosan functional layer and its application to a molecularly imprinted electrochemical sensor to quantify semicarbazide.

Semicarbazide (SEM) is a protein-bound nitrofurazone metabolite that is detrimental to human health. Therefore, to ensure food safety, it is necessary to detect SEM in food samples. To this end, we developed a novel electrochemical sensor to detect SEM by using a molecularly imprinted polymer (MIP) as the recognition element. Computer-aided molecular modelling was performed to guide the synthesis of the MIP, and subsequently, MIP/carboxylated single-walled carbon-nanotubes/chitosan (MIP/SWNTs-COOH/CS) was prepared as the sensing platform to develop the electrochemical sensor. The linear range of the sensor was 0.04-7.6 ng mL-1, with a detection limit of 0.025 ng mL-1. The sensor was successfully applied to detect SEM in four different real samples, with recoveries ranging from 83.16% to 93.40%. The results indicated that the fabricated electrochemical sensor can be widely applied to detect SEM in the environment and in agri-food products.

Novel magnetic fluorescence probe based on carbon quantum dots-doped molecularly imprinted polymer for AHLs signaling molecules sensing in fish juice and milk.

A magnetic fluorescence probe was fabricated by coating carbon quantum dots-doped molecularly imprinted polymers (MIPs) layers on the surface of Fe3O4 particles (MFMP) for detection of N-acyl homoserine lactones (AHLs) signaling molecules. N-Z-L-homoserine lactone molecular was used as the template to prepare AHLs MIP layers, employing MAA and HEMA as functional monomers. The developed MFMP owned superparamagnetism, fluorescence, fast response and class-selectivity. If AHLs (C4-HSL, C6-HSL, C8-HSL, C10-HSL, C12-HSL and C14-HSL) were captured by the MFMP, they quenched the fluorescence of the probe. Fluorescence dropped linearly in the concentration ranges of 3.65 × 10-3 µmol/L-0.96 × 10-1 µmol/L for AHLs. The MFMP was applied to the analysis of fish juice and milk samples, and recoveries ranged from 83.10% to 90.74% with relative standard deviation less than 5.1%. This study offered a novel strategy to fabricated AHLs fluorescence probe with great potential for wide-ranging application in agri-food products.

Temperature-Responsive Hierarchical Polymer Brushes Switching from Bactericidal to Cell Repellency.

Unlike conventional poly(N-isopropylacrylamide) (PNIPAM)-based surfaces switching from bactericidal activity to bacterial repellency upon decreasing temperature, we developed a hierarchical polymer architecture, which could maintain bactericidal activities at room temperature while presenting bacterial repellency at physiological temperature. In this architecture, a thermoresponsive bactericidal upper layer consisting of PNIPAM-based copolymer and vancomycin (Van) moieties was built on an antifouling poly(sulfobetaine methacrylate) (PSBMA) bottom layer via sequential surface-initiated photoiniferter-mediated polymerization. At room temperature below the lower critical solution temperature (LCST), the PNIPAM-based upper layer was stretchable, facilitating contact killing of bacteria by Van. At physiological temperature (above the LCST), the PNIPAM-based layer collapsed, thus leading to the burial of Van and exposure of bottom PSBMA brushes, finally displaying notable performances in bacterial inhibition, dead bacteria detachment, and biocompatibility, simultaneously. Our strategy provides a novel pathway in the rational design of temperature-sensitive switchable surfaces, which shows great advantages in the real-world infection-resistant applications.

Nonleaching Bacteria-Responsive Antibacterial Surface Based on a Unique Hierarchical Architecture.

Bacteria-responsive surfaces popularly exert their smart antibacterial activities by bacteria-triggered delivery of antibacterial agents; however, the antibacterial agents should be additionally reloaded for the renewal of these surfaces. Herein, a reversible, nonleaching bacteria-responsive antibacterial surface is prepared by taking advantage of a hierarchical polymer brush architecture. In this hierarchical surface, a pH-responsive poly(methacrylic acid) (PMAA) outer layer serves as an actuator modulating the surface behavior on demand, while antimicrobial peptides (AMP) are covalently immobilized on the inner layer. The PMAA hydration layer renders the hierarchical surface resistant to initial bacterial attachment and biocompatible under physiological conditions. When bacteria colonize the surface, the bacteria-triggered acidification allows the outermost PMAA chains to collapse, therefore exposing the underlying bactericidal AMP to on-demand kill bacteria. In addition, the dead bacteria can be released once the PMAA chains resume their hydrophilicity because of the environmental pH increase. The functionality of the nonleaching surface is reversible without additional reloading of the antibacterial agents. This approach provides a new methodology for the development of smart surfaces in a variety of practical biomedical applications.