Synthesis, Enzymatic Degradation, and Polymer-Miscibility Evaluation of Nonionic Antimicrobial Hyperbranched Polyesters with Indole or Isatin Functionalities.

Most macromolecular antimicrobials are ionic and thus lack miscibility/compatibility with nonionic substrate materials. In this context, nonionic hyperbranched polyesters (HBPs) with indole or isatin functionality were rationally designed, synthesized, and characterized. Antimicrobial disk diffusion assay indicated that these HBPs showed significant antibacterial activity against 8 human pathogenic bacteria compared to small molecules with indole or isatin groups. According to DSC measurements, up to 20% indole-based HBP is miscible with biodegradable polyesters (polyhydroxybutyrate or polycaprolactone), which can be attributed to the favorable hydrogen bonding between the N-H moiety of indole and the C═O of polyesters. HBPs with isatin or methylindole were completely immiscible with the same matrices. None of the HBPs leaked out from plastic matrix after being immersed in water for 5 days. The incorporation of indole into HBPs as well as small molecules facilitated their enzymatic degradation with PETase from Ideonella sakaiensis, while isatin had a complex impact. Molecular docking simulations of monomeric molecules with PETase revealed different orientations of the molecules at the active site due to the presence of indole or isatin groups, which could be related to the observed different enzymatic degradation behavior. Finally, biocompatibility analysis with a mammalian cell line showed the negligible cytotoxic effect of the fabricated HBPs.

Cellulose-Organic Montmorillonite Nanocomposites as Biomacromolecular Quorum-Sensing Inhibitor.

The aim of this study was to develop simple cellulose nanocomposites that can interfere with the quorum-sensing (QS)-regulated physiological process of bacteria, which will provide a sustainable and inexpensive solution to the serious challenges caused by bacterial infections in various products like food packaging or biomedical materials. Three cellulose nanocomposites with 1-5 w% octadecylamine-modified montmorillonite (ODA-MMT) were prepared by regeneration of cellulose from ionic liquid solutions in the presence of ODA-MMT suspension. Structural characterization of the nanocomposites showed that the ODA-MMT can be exfoliated or intercalated, depending on the load level of the nanofiller. Thermal gravimetric analysis showed that the incorporation of ODA-MMT nanofiller can improve the thermal stability of the nanocomposites compared with regenerated cellulose. Evaluation of the anti-QS effect against a pigment-producing bacteria C. violaceum CV026 by disc diffusion assay and flask incubation assay revealed that the QS-regulated violacein pigment production was significantly inhibited by the cellulose nanocomposites without interfering the bacterial vitality. Interestingly, the nanocomposite with the lowest load of ODA-MMT exhibited the most significant anti-QS effect, which may be correlated to the exfoliation of nanofillers. To our knowledge, this is the first report on the anti-QS effect of cellulose nanocomposites without the addition of any small molecular agents. Such inexpensive and nontoxic biomaterials will thus have great potential in the development of new cellulosic materials that can effectively prevent the formation of harmful biofilms.

Biocompatible non-leachable antimicrobial polymers with a nonionic hyperbranched backbone and phenolic terminal units.

This work aimed to develop biocompatible non-leachable antimicrobial polymers without ionic structures. A series of nonionic hyperbranched polymers (HBPs) with an isatin-based backbone and phenolic terminal units were synthesized and characterized. The molecular structures and thermal properties of the obtained HBPs were characterized by SEC, NMR, FTIR, TGA and DSC analyses. Disk diffusion assay revealed significant antibacterial activity of the obtained phenolic HBPs against nine different pathogenic bacteria. The presence of a methoxy or long alkyl group close to the phenolic unit enhanced the antibacterial effect against certain Gram positive and negative bacteria. The obtained nonionic HBPs were blended in polyester poly(hexamethylene terephthalate) films, which showed no noticeable leakage after being immersed in water for 5 days. Finally, these HBPs showed no cytotoxicity effect to MG-63 osteoblast-like human cells according to MTT analysis, and negligible hemolytic effect.

Usage of natural chitosan membrane obtained from insect corneal lenses as a drug carrier and its potential for point of care tests.

Chitosan is an indispensable biopolymer for use as a drug carrier thanks to its non-toxic, biodegradable, biocompatible, antimicrobial, and anti-oxidative nature. In previous studies, chitosan was first dissolved into weak acids and formed into gel, then used for carrying pharmaceutically active compounds such as nanoparticles, capsules, composites, and films. Using the produced chitosan gel after dissolving it in weak acids has advantages, such as ease of processing for loading the required amount of active substance and making the desired shape and size. However, dissolved chitosan loses some of its natural properties such as fibrous structure, crystallinity, and thermal stability. In this study, for the first time, three-dimensional chitosan lenses obtained from an insect's (Tabanus bovinus) compound eyes, with the original shape intact, were tested as a drug carrier. A model drug, quercetin, was loaded into chitosan membrane, and its release profile was examined. Also, a point-of-care test was conducted for both chitin and chitosan membranes. Chitin and chitosan membranes obtained from insect corneal lenses were characterized by using FTIR, TGA, elemental analysis, and surface wettability analysis as well as stereo, binocular, and scanning electron microscopies. It was observed that chitosan membrane could be used as a drug carrier material. Both chitin and chitosan membranes will be improved for lateral flow assay, and these membranes can be tested for other bioengineering applications in further studies.

Production of novel chia-mucilage nanocomposite films with starch nanocrystals; An inclusive biological and physicochemical perspective.

In the current study, chia mucilage composite films with starch nanocrystals (3% and 6%) were produced. The films were analyzed physicochemically (FT-IR, AFM, TGA, DSC), mechanically (Tensile strength and contact angle) and biologically (antimicrobial, antioxidant and cytotoxicity) properties. The incorporation of starch nanocrystals was confirmed through FT-IR spectra showing broad OH peak and CO stretching and shift in NH bending vibrations to the lower wave number. Starch nanocrystals enhanced (control 287.23 °C, film with 3% SNC 286.91 °C and film with 6% mucilage 289.41 °C) the thermal properties of the composite films. The Young Modulus of the film showed an increase after the incorporation of starch nanocrystals due to the strong interaction between mucilage and nanocrystals. On the other hand, the overall hydrophobicity of mucilage composite film decreased due to the hydrophilic nature of cornstarch nanocrystals. MTT assay for cell proliferation revealed significant inhibition of cancer cell (HepG2) lines and exhibits a very low inhibition of epithelial cell line (Vero). Starch nanocrystals enhanced the antibacterial and antioxidant (threefold increase compare to control) properties of mucilage composite films. Mucilage-SNC composite films could be a good therapeutic gain for control and directed drug delivery, food packaging, food coating.

Effect of different animal fat and plant oil additives on physicochemical, mechanical, antimicrobial and antioxidant properties of chitosan films.

Practical application of chitosan-essential oil blend films is limited due to the uneconomical extraction procedure of essential oils from plants. This study aimed to produce chitosan films blended with low cost and commercially available oils and fats consumed in daily human diet (olive, corn and sunflower oils, butter and animal fats). The study also focused on how physicochemical, biological and mechanical properties of chitosan blend films were influenced by the incorporation of oils and fats with varying unsaturation degrees. Possible interactions of chitosan film matrix with incorporated oils or fats were investigated. Chitosan-olive oil film showed better surface morphology and higher thermal stability than the films with other unsaturated oils. Tensile strength, Young's modulus and elongation at break were improved by 57.2%, 25.1% and 31.7% for chitosan-olive oil film, respectively. Chitosan-olive oil blend film had the highest antibacterial activity (almost equal to that of commercial antibiotic gentamicin). Edible films obtained from by incorporation of natural oils and fats into chitosan can help produce an environmentally friendly packaging material that is low cost and easily manufactured.

False flax (Camelina sativa) seed oil as suitable ingredient for the enhancement of physicochemical and biological properties of chitosan films.

To overcome the drawbacks of synthetic films in food packaging industry, researchers are turned to natural bio-based edible films enriched with various plant additives. In current study chitosan blend films were produced by incorporating Camelina sativa seed oil at varying concentrations to chitosan matrix. The chitosan blend films were characterized both physicochemically (structural, morphological, thermal, optical and mechanical) and biologically (antimicrobial and antioxidant activity). The incorporation of C. sativa seed oil notably enhanced thermal stability, antioxidative, anti-quorum sensing and antimicrobial activity. Except elongation at break, other mechanical properties of the blend films were not affected by incorporation of C. sativa seed oil. The surface morphology of blend films was recorded as slightly rough, non-porous and fibre-free surface. As it was expected the optical transmittance in visible region was gradually decreased with increasing fraction of seed oil. Interestingly the hydrophilicity of the blend films revealed a swift increase which can be explained by the formation of micelle between glycerol and Tween 40 in blend films. This study provides valuable information for C. sativa seed oil to be used as a blending ingredient in chitosan film technology.