Evaluation of antibacterial activity of branched quaternary ammonium grafted green polymers

Fabrication of antimicrobial and high-toughness poly (lactic acid) composite films using tung oil derivatives

Tung oil derivatives are promising alternatives to traditional toxic plasticizers for improving the toughness of poly (lactic acid) (PLA) films. In this study, a tung oil-based quaternary ammonium salt (Q-ETO) was synthesized using a multi-step process involving epoxidation, ring opening, and substitution reactions. PLA based composite films with various amounts of Q-ETO were prepared by solvent casting. The impact of various amount of Q-ETO on PLA/Q-ETO composite films were evaluated with regard to their mechanical properties, hydrophilicity, water vapor permeability, optical properties, thermal stability, antibacterial properties, and leaching properties. The PLA/5%Q-ETO composite film yielded the highest elongation at break (82.52 ± 9.53 %), which was 153.67 % higher than that of pure PLA. All PLA composite films showed an antibacterial efficiency exceeding 90 % against both S. aureus and E. coli. Moreover, the PLA/Q-ETO composite film blocked the transmission of both ultraviolet and visible light while preventing the permeation of water vapor. The addition of Q-ETO only weakly affected the color and thermal stability of the PLA/Q-ETO composite film. Given the numerous advantages of the PLA composite film, it has significant potential for application as a food packaging material.

Reusable antimicrobial antibiotic-free dressings obtained by photopolymerization

In recent years significant efforts have been made to develop new materials for wound dressing with improved healing properties. However, the synthesis methods usually employed to this end are often complex or require several steps. We describe here the synthesis and characterization of antimicrobial reusable dermatological wound dressings based on N-isopropylacrylamide co-polymerized with [2-(Methacryloyloxy) ethyl] trimethylammonium chloride hydrogels (NIPAM-co-METAC). The dressings were obtained with a very efficient single-step synthesis procedure based on visible light (455 nm) by photopolymerization. To this end, F8BT nanoparticles of the conjugated polymer (poly(9,9-dioctylfluorene-alt-benzothiadiazole) - F8BT) were used as macro-photoinitiators, and a modified silsesquioxane was employed as crosslinker. Dressings obtained by this simple and gentle method show antimicrobial and wound healing properties, without the incorporation of antibiotics or any other additives. The physical and mechanical properties of these hydrogel-based dressings were evaluated, as well as their microbiological properties, through in vitro experiments. Results show that dressings with a molar ratio of METAC of 0.5 or higher exhibit high swelling capacity, appropriate water vapor transmission rate values, stability and thermal response, high ductility and adhesiveness. In addition, biological tests showed that the dressings have significant antimicrobial capacity. The best inactivation performance was found for hydrogels synthesized with the highest METAC content. The dressings were tested several times with fresh bacterial cultures, showing a bacterial kill efficiency of 99.99 % even after three repetitions in a row, employing the same dressing, demonstrating the intrinsic bactericidal property of the materials and their reusability. In addition, the gels show low hemolytic effect, high dermal biocompatibility and noticeable wound healing effects. Overall results demonstrate that some specific hydrogel formulations have potential application as dermatological dressings for wound healing and disinfection.

Cucurbit[7]uril-Mediated Supramolecular Bactericidal Nanoparticles: Their Assembly Process, Controlled Release, and Safe Treatment of Intractable Plant Bacterial Diseases

A safe, biocompatible, and stimuli-responsive cucurbit[7]uril-mediated supramolecular bactericidal nanoparticle was fabricated by encapsulating a highly bioactive carbazole-decorated imidazolium salt (A₁, EC₅₀ = 0.647 μg/mL against phytopathogen Xanthomonas oryzae pv oryzae) into the host cucurbit[7]uril (CB[7]), thereby leading to self-assembled topographies from microsheets (A₁) to nanospheroidal architectures (A₁@CB[7]). The assembly behaviors were elucidated by acquired single-crystal structures, ¹H NMR, ITC, and X-ray powder diffraction experiments. Complex A₁@CB[7] displayed lower phytotoxicity and could efficiently switch on its potent antibacterial ability via introducing a simple competitor 1-adamantanamine hydrochloride (AD). In vivo antibacterial trials against rice bacterial blight revealed that A₁@CB[7] could relieve the disease symptoms after being triggered by AD and provide a workable control efficiency of 42.6% at 100 μg/mL, which was superior to bismerthiazol (33.4%). These materials can provide a viable platform for fabricating diverse stimuli-responsive supramolecular bactericides for managing bacterial infections with improved safety.

Surface-initiated atom-transfer radical polymerization (SI-ATRP) of bactericidal polymer brushes on poly(lactic acid) surfaces

We have modified the surface of poly(lactic acid) (PLA) by bromination in the presence of N-bromosuccinimide (NBS) under UV irradiation. This new approach to impart functionality to the surface does not effect the bulk of the material. Brominated PLA surfaces served as initiators for atom-transfer radical polymerization (SI-ATRP) of 2-(methacryloyloxy)ethyl]trimethylammonium chloride, a quaternary ammonium methacrylate (QMA). Grafting of poly(QMA) brushes rendered PLA films hydrophilic and these films displayed a three-order of magnitude increase in antimicrobial efficacy against Gram-negative bacteria such as Escherichia coli as compared to unmodified PLA. The two-step strategy described here to modify PLA surface represents a useful route to modified PLA materials for biomedical and antimicrobial packaging applications.

A Synthetic Overview of Preparation Protocols of Nonmetallic, Contact-Active Antimicrobial Quaternary Surfaces on Polymer Substrates

Antibacterial surfaces have been researched for more than 30 years and remain highly desirable. In particular, there is an interest in providing antimicrobial properties to commodity plastics, because these, in their native state, are excellent substrates for pathogens to adhere and proliferate on. Therefore, efficient strategies for converting surfaces of commodity plastics into contact-active antimicrobial surfaces are of significant interest. Many systems have been prepared and tested for their efficacy. Here, the synthetic approaches to such active surfaces are reviewed, with the restriction to only include systems with tested antibacterial properties. The review focuses on the synthetic approach to surface functionalization of the most common materials used and tested for biomedical applications, which effectively has limited the study to quaternary materials. For future developments in the field, it is evident that there is a need for development of simple methods that permit scalable production of active surfaces. Furthermore, in terms of efficacy, there is an outstanding concern of a lack of universal antimicrobial action as well as rapid deactivation of the antibacterial effect through surface fouling.

Synthesis and Antibacterial Activity of Metal-Containing Ultraviolet-Cured Wood Floor Coatings

In our previous report, the antibacterial agents with different metals, mono(hydroxyethoxyethyl)phthalate [M(HEEP)₂, M = Zn, Mn, and Ca], were synthesized. For increasing their yields, modified synthesis and purified processes were further investigated. The result of energy-dispersive X-ray spectroscopy showed the M(HEEP)₂ could be stable and successfully synthesized, and their yields were raised to 73–85% from our previous report of 43–55%. For ultraviolet-cured wood floor coating application, the Zn(HEEP)₂ was selected as an antibacterial agent and mixed with commercial UV wood floor coating. The effects on the antibacterial activity of UV films with different Zn(HEEP)₂ additions of 0, 4, 8, and 12 phr as well as the commercial nano-Ag of 12 phr against Escherichia coli were evaluated. In the static antibacterial test, the UV films with Zn(HEEP)₂ additions had similar antibacterial activity of 57–59%. In another dynamic shaking antibacterial test, the film containing 12 phr Zn(HEEP)₂ had the best antibacterial activity among all the UV films. On the film properties, the Zn(HEEP)₂-containing UV films had lower gloss and abrasion resistance, and slightly increased the hardness than those of UV film without Zn(HEEP)₂ addition. However, there were no noticeable differences in mass retention, lightfastness, and thermal stability between UV films with and without the Zn(HEEP)₂ addition. In this study, the 12 phr Zn(HEEP)₂-containing UV film provided the best antibacterial activity against E. coli and had the balanced film properties for application on the UV wood floor coating.

Recent Progress in Antimicrobial Strategies for Resin-Based Restoratives

Repairing tooth defects with dental resin composites is currently the most commonly used method due to their tooth-colored esthetics and photocuring properties. However, the higher than desirable failure rate and moderate service life are the biggest challenges the composites currently face. Secondary caries is one of the most common reasons leading to repair failure. Therefore, many attempts have been carried out on the development of a new generation of antimicrobial and therapeutic dental polymer composite materials to inhibit dental caries and prolong the lifespan of restorations. These new antimicrobial materials can inhibit the formation of biofilms, reduce acid production from bacteria and the occurrence of secondary caries. These results are encouraging and open the doors to future clinical studies on the therapeutic value of antimicrobial dental resin-based restoratives. However, antimicrobial resins still face challenges such as biocompatibility, drug resistance and uncontrolled release of antimicrobial agents. In the future, we should focus on the development of more efficient, durable and smart antimicrobial dental resins. This article focuses on the most recent 5 years of research, reviews the current antimicrobial strategies of composite resins, and introduces representative antimicrobial agents and their antimicrobial mechanisms.

Antibacterial Textile Based on Hydrolyzed Milk Casein

Antimicrobial textile structures are developed based on polypropylene (PP) and a natural material, hydrolyzed casein. The casein, from bovine milk, is subjected to acid hydrolysis in aqueous media, then blended into the PP matrix in the melt phase by extrusion. The obtained blend, containing 5 wt.% of hydrolyzed casein, is then processed by a melt spinning process to get multifilaments, leading to the production knitting structures. Thanks to the addition of the hydrolyzed casein, the obtained textile showed a strong antibacterial activity towards both Gram (+) and Gram (−) bacterial strains. The addition of 5 wt.% hydrolyzed casein does not significantly impact the mechanical properties of PP in the dumbbells form, but a small decrease was observed in the tenacity of the filaments. No moisture retention was observed after the addition of hydrolyzed casein, but the rheological behavior was slightly affected. The obtained results can contribute to addressing concerns regarding nonrenewable antibacterial agents used in textile materials, particularly their effects on the environment and human health, by offering antibacterial agents from a biobased and edible substance with high efficiency. They are also promising to respond to issues of wasting dairy products and recycling them, in addition to the advantages of using melt processes.

New details of assembling bioactive films from dispersions of amphiphilic molecules on titania surfaces

Tailoring the surface properties of materials for biomedical applications is important to avoid clinical complications. Forming thin layers of amphiphilic molecules with apolar regions that facilitate attractive intermolecular interactions, can be a suitable and versatile approach to achieve hydrophobic surface modification and provide functional antibacterial properties. Aiming to correlate layer structure and properties starting from film formation, octadecylphosphonic acid (ODPA) and dimethyloctadecyl (3-trimethoxysilylpropyl) ammonium chloride (DMOAP) layers were adsorbed onto smooth titania surfaces. Then the films were studied by atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), and their interactions with aqueous environments were characterized by contact angle and zeta potential measurements. In addition, antibacterial assays were performed using E. coli and S. mutants to reveal the antibacterial properties effected by the surface modification. Immediately after sputter deposition, titania was hydrophilic; however, after air storage and adsorption of DMOAP or ODPA, an increase in the water contact angle was observed. XPS investigations after layer formation and after antibacterial tests revealed that the attachment of layers assembled from ODPA on titania substrates is considerably stronger and more stable than that observed for DMOAP films. Heat treatment strongly affects DMOAP layers. Furthermore, DMOAP layers are not stable under biological conditions.

Structure–property relationship of amphiphilic molecules on smooth substrates was explored through a multi-step approach and its influence on biological activity.

Antibacterial quaternary ammonium compounds in dental materials: A systematic review

OBJECTIVE

Quaternary ammonium compounds (QACs) represent one of the most effective classes of disinfectant agents in dental materials and resin nanocomposites. This reviews aims to give a wide overview on the research in the field of antibacterial QACs in dental materials and nanocomposites.

METHOD

An introduction to dental materials components as well as the microorganisms and methods of evaluation for the antimicrobial assays are presented. Then, the properties and synthesis route of QACs, as monomer and filler, are shown. Finally, antimicrobial monomers and fillers, specifically those contain quaternary ammonium salts (QASs), in dental materials are reviewed.

RESULTS

QACs have been used as monomer and micro/nanofiller in restorative dentistry. They possess one or more methacrylate functional groups to participate in polymerization reactions. QACs with multiple methacrylate groups can also be used as crosslinking agents. Furthermore, QACs with chain length from ∼12 to 16 have higher antimicrobial activity in cured dental resins. In general, increasing the chain length leads to a threshold value (critical point) and then it causes decrease in the antimicrobial activity.

SIGNIFICANCE

The current state of the art of dental materials and resin nanocomposites includes a wide variety of antimicrobial materials. Among them, QACs presents low cytotoxicity and excellent long-term antimicrobial activity without leaching out over time.

Burkholderia cepacia lipase immobilized on heterofunctional magnetic nanoparticles and its application in biodiesel synthesis

Biodiesel production using immobilized lipase as a biocatalyst is a promising process. The performance of immobilized lipase is mainly determined by supporting materials and immobilization method. To avoid the shortcomings of adsorption and covalent bonding methods, in this study, we developed a novel heterofunctional carrier of being strengthened anion exchange and weakened covalent binding to avoid activity loss and improve operational stability of the immobilized lipase. 2,3-epoxypropyltrimethylammonium chloride with epoxy and quaternary ammonium group and glutaraldehyde were grafted onto aminated magnetic nanoparticles (AMNPs) to generate a new matrix, named GEAMNP. Then Burkholderia cepacia lipase (BCL) was immobilized on GEAMNP via anion exchange and covalent bonding. The transesterification between soybean oil and methanol was used to test the activities. Activity recovery of the immobilized BCL was up to 147.4% and the corresponding transesterification activity was 1.5-fold than that of BCL powder. The immobilized lipase was further used for biodiesel production to confirm its feasibility. The fatty acid methyl esters conversion yield could reach 96.8% in the first 12 h. Furthermore, the immobilized lipase, BCL-GEAMNP showed markedly improved operational stability, better reusability and higher esters than BCL-GAMNP, where MNPs were only modified with (3-aminopropyl) triethoxysilane and glutaraldehyde.