Experience of using heat citric acid disinfection method in central dialysis fluid delivery system.

We applied the heat citric acid disinfection method in the main part of the central dialysis fluid delivery system (MPCDDS), which consists of a multiple-patient dialysis fluid supply unit, dialysis console units, and dialysis fluid piping. This disinfection method has been used for single-patient dialysis machines, but this is the first trial in the MPCDDS. We examined, by points of safety and disinfection effect, whether this disinfection method is comparable to conventional disinfection methods in Japan. The conventional disinfection method is a combination of two disinfectants, sodium hypochlorite and acetic acid, used separately for protein removal and decalcification. Consequently, total microbial counts and endotoxin concentrations fully satisfied the microbiological requirements for standard dialysis fluid of ISO 11663. From our results and discussion, this heat citric acid disinfection method is proved to be safe and reliable for MPCDDS. However, to satisfy the microbiological requirements for ultrapure dialysis fluid, further consideration for this method in MPCDDS including the reverse osmosis device composition and piping is necessary.

Manufacturing micropatterned collagen scaffolds with chemical-crosslinking for development of biomimetic tissue-engineered oral mucosa.

The junction between the epithelium and the underlying connective tissue undulates, constituting of rete ridges, which lack currently available soft tissue constructs. In this study, using a micro electro mechanical systems process and soft lithography, fifteen negative molds, with different dimensions and aspect ratios in grid- and pillar-type configurations, were designed and fabricated to create three-dimensional micropatterns and replicated onto fish-scale type I collagen scaffolds treated with chemical crosslinking. Image analyses showed the micropatterns were well-transferred onto the scaffold surfaces, showing the versatility of our manufacturing system. With the help of rheological test, the collagen scaffold manufactured in this study was confirmed to be an ideal gel and have visco-elastic features. As compared with our previous study, its mechanical and handling properties were improved by chemical cross-linking, which is beneficial for grafting and suturing into the complex structures of oral cavity. Histologic evaluation of a tissue-engineered oral mucosa showed the topographical microstructures of grid-type were well-preserved, rather than pillar-type, a well-stratified epithelial layer was regenerated on all scaffolds and the epithelial rete ridge-like structure was developed. As this three-dimensional microstructure is valuable for maintaining epithelial integrity, our micropatterned collagen scaffolds can be used not only intraorally but extraorally as a graft material for human use.

Development of microstructured fish scale collagen scaffolds to manufacture a tissue-engineered oral mucosa equivalent.

The present study aimed to develop a more biomimetic tissue-engineered oral mucosa equivalent comprising 1% type I tilapia scale collagen scaffold having microstructures mimicking the dermal-epidermal junction of oral mucosa and oral keratinocytes as graft materials for human use. We designed four micropattern prototypes mimicking the dermal-epidermal junction. Using a semiconductor process and soft lithography, negative molds were fabricated to develop microstructures using both polydimethylsiloxane and silicon substrates. Micropattern configurations of dermal-epidermal junctions manufactured from fish collagen consisting of a fibril network using our micropatterning system were well preserved, although the internal fibril network of the pillar pattern was sparse. Mixing 1% chondroitin sulfate with the collagen matrix minimized tissue-engineered oral mucosa equivalent contraction. Histologic examinations showed a flattening of the vertical dimensions of all microstructures and expansion of their pitches, indicating changes in the originally designed configurations. Nonetheless, histologic examinations revealed that a fully differentiated and stratified epithelial layer was developed on all scaffolds, suggesting that the microstructured fish scale collagen scaffolds have potential in the manufacturing of tissue-engineered oral mucosa equivalents for clinical use; however, enhancement of the mechanical properties of micropatterns is required. Our micropatterning technology can also apply to the development of oral mucosa in vitro models.