Deciphering the Chitin Code in Plant Symbiosis, Defense, and Microbial Networks

Chitin is a structural polymer in many eukaryotes. Many organisms can degrade chitin to defend against chitinous pathogens or use chitin oligomers as food. Beneficial microorganisms like nitrogen-fixing symbiotic rhizobia and mycorrhizal fungi produce chitin-based signal molecules called lipo-chitooligosaccharides (LCOs) and short chitin oligomers to initiate a symbiotic relationship with their compatible hosts and exchange nutrients. A recent study revealed that a broad range of fungi produce LCOs and chitooligosaccharides (COs), suggesting that these signaling molecules are not limited to beneficial microbes. The fungal LCOs also affect fungal growth and development, indicating that the roles of LCOs beyond symbiosis and LCO production may predate mycorrhizal symbiosis. This review describes the diverse structures of chitin; their perception by eukaryotes and prokaryotes; and their roles in symbiotic interactions, defense, and microbe-microbe interactions. We also discuss potential strategies of fungi to synthesize LCOs and their roles in fungi with different lifestyles.

Efficiency of cleaning dental structural polymer materials and their resistance to biofouling

Aim. The formation of biofilms, involving microorganisms from the oral cavity, on the surface of various structural dental materials was investigated. Flexistron Plus, Dentalos Plus, and PEEK are used in dental orthopedic practice for prosthetics. Materials and methods. The difference in quantity depends on the structure and type of plastics, as well as on their mechanical cleaning. All the plastic samples were obtained using atomic force microscopy, which made it possible to detect differences in the microstructure and microrelief of all the types of plastics and to demonstrate bacterial growth on plastics before and after the mechanical cleaning of their surfaces with a toothbrush. Conclusion. The revealed facts of increased microbial contamination after the mechanical treatment of the surface of polymer materials suggest the need for additional lining with harder materials or the creation of new composites based on these polymers with high hygienic adequacy.

Advanced polymer materials with energy-effi cient molding mode for structural composite products

The epoxy resin and adhesive fi lm with energy-effi cient molding process are considered in present paper. These materials are suitable for production of structural polymer composite products based on fi brous fi llers obtained by prepreg technology. They can be used in the aviation, space, automobile, shipbuilding, railway transport and other fi elds.

Chromatic Sensor to Determine Oxygen Presence for Applications in Intelligent Packaging

A chromatic sensor has been designed for the detection of oxygen in package headspace. The sensor is based on the redox change of methylene blue (MB) to its leuco form. Its formulation includes the pigment, glycerol, as a sacrificial electron donor, TiO2, as a photocatalyst and ethylene-vinyl alcohol copolymer (EVOH), as a structural polymer matrix. The final sensor design that allows its manufacture by conventional printing and laminating technologies consists of the sensing polymer matrix (MB-EVOH) sandwiched in a suitable transparent multilayer structure. The outer layers protect the sensor from the external atmosphere and allow visualization of the colour. The inner layer is sufficiently opaque to facilitate sensor reading from the outside, is thick enough to avoid direct contact with food (functional barrier), and is oxygen-permeable to expose the sensing material to the internal package atmosphere. In the absence of oxygen, the sensor becomes white by irradiation with halogen lamps in less than 60 s. All components are substances permitted for food contact except the pigment, but specific migration analysis showed no trace of migration thanks to the functional barrier included in the design.

Embedded optical nanosensors for monitoring the processing and performance of polymer matrix composites

We provide a broad review of optically responsive materials with potential for in situ monitoring of material state properties in structural polymer-based materials with nanoscale spatial resolution.