We previously reported a xanthan gum (Xan) hydrogel showing excellent mechanical properties. Mineralization of hydroxyapatite (Hap) upon the Xan hydrogel would provide a unique biomaterial applicable for bone tissue engineering. Here, we show the mineralization of Hap upon the Xan hydrogel by means of an alternate soaking process. Hap was gradually grown upon the Xan-matrix surface with increasing number of soaking cycles due to the ionic interactions between calcium cations and carboxyl groups. Interestingly, the mineralization induced a microstructure change in the gel-matrix from a layered structure to a porous structure. The mechanical properties of the resulting Hap-Xan composite hydrogels were further investigated by a tensile test, where the Hap-Xan composite hydrogel with an appropriate amount of Hap (Xan/Hap=2.7) was capable of approximately 370% elongation.

We have designed a novel 1,8-naphthalimide derivative with an open space for an anion. Computational calculation has predicted that the space could trap various anion species and photo-induced charge transfer depending on the anion's electrophilic properties. Indeed, the fluorescence behaviour of the 1,8-naphthalimide derivative complexes with each anion is consistent with the computational prediction.

1-Methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium can be a discriminator for anionic polysaccharides via monomer-excimer switching and photo-induced colorimetric reaction. In the system, the excimer fluorescence increases remarkably in the presence of sulfated polysaccharides. The degree of enhancement depends on the number of sulfate groups in its structure. In contrast, the degree of excimer enhancement is not significant in the presence of carboxylated polysaccharides probably due to a different photo-induced decay pathway. The solutions containing carboxylated polysaccharides certainly become yellow via a photo-induced colorimetric reaction.