Fabrication of plane-type axon guidance substrates by applying diamond-like carbon thin film deposition.

This research aims to fabricate plane-type substrates for evaluating the axon behaviors of neuronal cells in vitro toward the development of brain-on-chip models by applying the functions of diamond-like carbon (DLC) thin film deposition, which helped to eliminate the costly and time-consuming lithography process by utilizing a shadow mask. The DLC thin films were partially deposited on stretched polydimethylsiloxane (PDMS) substrates covered with a metal mask by the plasma chemical vaper deposition method, and using the substrates culture teats with human neuroblastoma cells (SH-SY5Y) were performed. Three patterns of interconnection structures of axons were created on the substrates with disordered and regular linear wrinkle structures with several µm size formed by the depositions. The patterns were characterized by the structure that the aggregations of axons formed on the linear DLC thin film deposited areas were separately placed in regular intervals and connected each other by plenty of axons, which were individually taut in a straight line at about 100 to over 200 µm in length. The substrates expected of uses for evaluation of axon behaviors are available without fabricating guiding grooves by conventional soft lithographic methods requiring multiple stages and their treating times.

Impedance Characteristics of Monolayer and Bilayer Graphene Films with Biofilm Formation and Growth.

Biofilms are the result of bacterial activity. When the number of bacteria (attached to materials' surfaces) reaches a certain threshold value, then the bacteria simultaneously excrete organic polymers (EPS: extracellular polymeric substances). These sticky polymers encase and protect the bacteria. They are called biofilms and contain about 80% water. Other components of biofilm include polymeric carbon compounds such as polysaccharides and bacteria. It is well-known that biofilms cause various medical and hygiene problems. Therefore, it is important to have a sensor that can detect biofilms to solve such problems. Graphene is a single-atom-thick sheet in which carbon atoms are connected in a hexagonal shape like a honeycomb. Carbon compounds generally bond easily to graphene. Therefore, it is highly possible that graphene could serve as a sensor to monitor biofilm formation and growth. In our previous study, monolayer graphene was prepared on a glass substrate by the chemical vapor deposition (CVD) method. Its biofilm forming ability was compared with that of graphite. As a result, the CVD graphene film had the higher sensitivity for biofilm formation. However, the monolayer graphene has a mechanical disadvantage when used as a biofilm sensor. Therefore, for this new research project, we prepared bilayer graphene with high mechanical strength by using the CVD process on copper substrates. For these specimens, we measured the capacitance component of the specimens' impedance. In addition, we have included a discussion about the possibility of applying them as future sensors for monitoring biofilm formation and growth.

Investigation of nanoplastic cytotoxicity using SH-SY5Y human neuroblastoma cells and polystyrene nanoparticles.

Nanoplastics have spread widely throughout not only the oceans but also the atmosphere, and recently created great concern about human health relevant to ingestion and accumulation of the nanoparticles by aquatic organisms in the human food-chain. However, how the nanoplastics have an affect on actual human body remains largely unknown, and in particular, little knowledge about nanoplastic exposure to the nervous system in human has been obtained in vitro and still less vivo. Here, we evaluated how much concentration of nanoplastics had a direct impact on cells in the nervous system as the fundamental information. Specifically, the cytotoxicity was investigated by exposure of polystyrene nanoparticles (PS) to cultured neural cells, human neuroblastoma cells, SH-SY5Y. Our results demonstrated that the PS exposure induced the cytotoxicity in the cells promoted differentiation into neuronal phenotype, and the adverse effect was comparable to or exceed that of acrylamide, a well-recognized potent neurotoxin. Also, the cells under PS exposure exhibited shrinkage of neurite outgrowth, morphology alteration and swelling of the nuclei, and spilling of intracellular components. Moreover, our findings indicate that the concentration of nanoplastics caused the cytotoxicity on neuronal cells is likely to be much higher than those predicted from the marine environment.